Aaron Daigh has been tasked with a mighty challenge: figure out how to clean up the messes left by fracking brine spills. The North Dakota State University soil scientist says most of the average 42 spills a week are relatively small, covering only a few hundred square feet or a couple acres. However, they are still severe and do take land out of agricultural production, possibly for thousands of years. The Bakken oil field in western North Dakota is typical of hydraulic fracturing everywhere. Clean water is pumped into a well to open the seams. When the water is pumped out again, it is highly contaminated with sodium chloride and other minerals. “The brine is dangerous to the local ecosystem if it escapes because it’s so saline. The (electrical conductivity) is over 200. Sea water has an EC of 40 to 50,” Daigh said.
By comparison, prairie cropland is considered to be severely saline if the EC is 10 to 15. “The biggest spills come from pipeline breaks that go undetected,” he said. “These pipelines carry brine pumped out of a fracking well heading to a storage lagoon somewhere. After the brine settles for a while, it’s pumped into a deep well left over from the days of deep oil drilling. “So it’s highly saline. We’ve had some of these pipeline breaks let loose three million litres in one spill. The brine ends up following the lay of land and it can carry on for miles and miles. It might only be 40 or 50 feet wide, but it covers a large area.”
Daigh said the fracking process fractures geological formations that are millions of years old and loaded with highly concentrated sodium chloride. Those salts and other minerals are caught in the brine. When everything goes as planned, the brine is injected before it has a chance to contaminate the Earth’s surface. “Is there a way to harvest those minerals? We’ve had a lot of questions like that,” he said. “Is there enough lithium in there to extract it commercially? How about the magnesium and the many other minerals? How to use reclaimed salt?” Daigh said his role is to rehabilitate contaminated land, but these other questions will eventually be answered. He said fighting prairie salinity is difficult, even if there are no brine spills. “Here in western North Dakota, we’re in a dry climate,” he said. “Every time we try to leech salts back down into the ground, we’re fighting against what nature wants to do. If there’s salt in the soil and we get rain, the water wants to bring them right back up to the surface.”
The answer might be ferric hexacyanoferrate, a chemical that pulls salt out of the soil and crystallizes it on the surface. Early trials were encouraging. An NDSU news release said researchers applied ferric hexacyanoferrate to samples of brine-contaminated soil in the laboratory. Twenty-nine to 57 percent of the salt was pulled to the surface after seven days for easier removal. Salt crystals that formed on the soil surface were high in water content and easy to remove. This technique shows promise as a quick and simple way to clean up salt contaminated soil. “We started playing with these crystalization inhibitors and found that they shift salt crystallization to where it’s above the soil surface and detached from the soil,” he said.
“Once you vacuum up the crystals, you end up with bare clean ground. There’s no soil in the vacuum and no sodium salt left on the soil.
Bare clean ground
“But we know that one treatment won’t do it. There’s a lower boundary of how much sodium salt has to be in the soil for this operation to work. It won’t work if there’s only a small amount of salt. We can take out the first 50 percent really fast. The other half will require some other remediation action, perhaps other traditional recovery methods such as amendments like gypsum or calcium based leeching techniques. “We see the best potential for this in first response situations. Once a spill happens, get to it right away with the notion of trying to capture the greatest majority of the salts. Get half of it off in the first week. Maybe tile drain the area quickly to catch the salts before they go down into the ground.”
Daigh said the goal is to make the soil clean enough so it can be re-vegetated and eventually put back into agricultural production. NDSU says traditional methods that are used to remove salt from soil contaminated by brine spills either take too long or involve removing the soil. Excavating contaminated soil and moving it to designated areas only relocates the problem. Salt still remains in the soil. “No one has tried to bring the salt up, out of the ground, and harvest it. That would be a permanent remediation strategy,” the university said. “There was one major obstacle. As water evaporates from the soil, salts get deposited in the soil pores. The deposited salt can form a hard, cemented crust which is very difficult to remove. We needed to find a way to stop this salty crust from forming. “When the re-searchers applied this chemical to salt-contaminated soils in the laboratory, it made salts crystallize out of the soils and ‘bloom’ out on the surface.”
Twenty-nine percent of the salt had bloomed on sandy loam within seven days of application, 46 percent of the salt had bloomed on loam and 57 percent of the salt had bloomed on silty clay soil.
Daigh said safety was a concern, but toxicity toward humans and the environment is relatively minimal. He said the chemical is ex-traordinarily stable. When it does decompose, he added, the chemical yields hydrogen and free-cyanides, which can be toxic, but it breaks down quite slowly, taking decades or even centuries under most soil conditions. This slow breakdown can allow microbes to metabolize the cyanides and render them relatively harmless. As well, ferric hexacyanoferrate is just one example of a chemical that can be used. “Other chemicals with low-toxicity reaction products may produce similar results,” he said. “We need to find out how much to apply and how often to apply it.” Daigh said he is also researching the possibility of using this method to rehabilitate typical prairie salinity but doesn’t think it is likely. “This works because sodium chloride is highly soluble in water, but calcium salts and magnesium salts have low solubility,” he said. “The natural near-surface salinity we see on the northern great plains is calcium, magnesium, sulfate based. They don’t stay dissolved in water. “For this process to work, it re-quires salts to remain suspended in water until they start growing up out of the ground. The more calcium in the soil, the more it tends to cement up. The crystals that start never get a chance to get going and bloom on the surface.”
Genetically engineered crops don’t appear to harm humans or the environment, according to a new report released May 17 by the National Academies of Sciences, Engineering and Medicine.
An extensive analysis of two decades’ worth of evidence dug up no substantial proof that genetically engineered foods were any less safe to eat than those that are conventionally bred. The study’s authors also found no conclusive causal link between the engineered crops and environmental problems. The authors note, though, that it’s not always easy to make definitive conclusions; measuring long-term environmental changes is complicated.
The news comes in the midst of political tumult in the United States over laws to label foods made with GE ingredients. But when it comes to food safety and the environment, the authors conclude, how a plant is made isn’t as important as what is actually created.
In April, while his neighbors planted wheat, Randy Neva crisscrossed his Kensal, North Dakota, acreage with a John Deere no-till drill filled with barley seed as he looked for areas with the poorest soil. Instead of spending $200 to $350 per acre for soybean or corn seed, herbicides, and fertilizer, he spent approximately $25 per acre for seed and fuel on about 50 acres.
“It’s better to not spend money on something that won’t grow anything. If I don’t lose money, it’s like saving. I don’t get anything back, so I don’t put the investment into it,” Neva says. With 30 years of experience farming with his father, James, and his brother, Tim, he knows which areas drown out or are so saline-saturated that they yield very little to nothing.
The Nevas have been dabbling with barley for about five years at the encouragement of Lee Briese, an agronomist consultant with Centrol Inc. “Lee has long forewarned us of weeds and salinity problems and that we are wasting our money planting crops,” Neva says. “We’ve got certain areas that are pure white with salinity that won’t even grow weeds anymore.” Barley is the only crop that will grow in some saline areas, and this year Neva planted it around the farm’s slough borders and wherever he saw soil tinged with white. It set back planting a couple of days, but by seeding barley first, he could drive anywhere he wanted. He planted a normal rate of 50 to 60 pounds of barley seed per acre in plots as small as 1 acre, with many averaging 5 acres. It did make planting crops less convenient, he admits, since he had to swing around the barley-planted acres or raise the planter until he got over them. He had to do this whenever he sprayed his soybean or corn crops so he didn’t kill out the barley. The extra work is the reason many farmers continue to plant row crops in areas that won’t produce, Briese says. With lower commodity prices and high input costs, however, more farmers are choosing to patchwork-plant less expensive crops such as barley, rye, and winter camelina. “Barley is a cheap option and can be planted anytime you can get in there. Even planted as late as July 10, it will make grain if it’s the right fall. Or, you can get hay or at least a cover crop to control some of the weeds,” Briese says.
Farms along the Highway 281 corridor in North Dakota face similar challenges as the Neva farm, Briese says. “They have a lot of salinity and areas that drown out often. This has been going on for years,” he says. “I’ve been trying to get farmers to stop farming it just because it looks good in the spring. They should grow strips of barley or grass or anything different just because marginal soil is a money pit. They are kochia preserves since often that’s all that will grow there.” Instead of allowing Mother Nature to take over with the noxious weed, Briese encourages his clients to use no-till and to keep the soil covered. In areas where the salinity isn’t too high, winter rye works well. It overwinters, competes well against weeds, and has roots that create better infiltration to take up excess water. Neva seeded beans straight into it this spring and killed the rye with Roundup. “I’ve seen some success and an increase in the bean crop in past years,” he says. “It’s mucky, gluey soil, and the rye has a large root mass. So the advantage is that it adds structure to the soil and holds up the planter.”
Though the acres Neva planted won’t make a profit, he has a use for the barley. “We run cattle, so we’re hoping to use it for feed,” he says. He plans to cut the barley at the soft dough stage around mid-July. Even poor land can yield enough hay for one or more large bales per acre. Areas that are fenced can also be grazed, and some of the barley will be left to grow as cover and for wildlife. In some of the areas he didn’t plan to cut for hay, Neva added a little radish seed. It also grows in saline soil and is good for taking up excess water. Besides saving on input costs, some landowners he rents from give him a cost break on land that doesn’t produce well. “They appreciate that I’m trying to do something to improve the soil,” Neva says. “Long-term, we’re trying to get some health back in the soil, though I don’t know if I will see it in my lifetime. Some marginal areas may get better.”
With the focus of not spending money on crops that won’t yield anyway, Neva is looking for other ways to get ahead. On 302 acres of one half-section, he can only farm about 220 acres. The rest is grass and sloughs with cattails. This spring, he signed up for the Farmable Wetlands program and planted grasses in the rings around the sloughs. The seed mix cost $80 to $90 per acre, but he was able to cost-share the seed, labor, drill rental, and spray costs. He will receive payments for 10 years. Though there are restrictions and guidelines to follow, the program fits in with his farm operation. “I’m looking at my fields and seeing where I can do more of this. I’d rather get a little money than none,” Neva says. Even on his patchwork plots of land that won’t financially compensate him, he believes he is getting ahead, whether it is used for cattle feed or left for cover. When he drives past other fields that were planted end to end with beans or corn when soil conditions were favorable, he feels even better about his barley crop. “I’m looking at fields and areas that are planted with high expenses and have just a few spears of corn growing,” he says. Though it’s less convenient, he plans to continue planting inexpensive seed in his poorest land. “I think we’ll be doing it forever. Lee said there’s some land we won’t reclaim because the saline is so high,” Neva concludes.
Oats Face Numerous Pre-Harvest Question Marks
Oat producers are playing the waiting game when it comes to one of the most important things for oat crops: quality. “There’s always a concern about quality and you never know where that is going to be until harvest,” said Art Enns, president of the Prairie Oat Growers Association at Morris in Manitoba’s Red River Valley. Reports in South Dakota, where weather has been hot and dry, say quality hasn’t been what millers hoped for, Enns said. So far, oat crops across the Prairies are looking to fare better than their neighbours to the south. “I think it’s varied… but overall everyone is saying the crops are looking decent, despite all the rain we’ve had,” he said.
Seeded acreage for oats is down about 15-20 per cent from last year due to strong competition from pulse and lentil crops, Enns said. With the addition of wet weather, exactly how much of a yield producers will get is still up in the air.“Are there going to be losses due to flooding and stuff like that? Yes… We don’t know exactly what the crop is going to yield,” he said. Disease could also become an issue with the excess moisture and reports of fusarium showing up in some areas, he said. To what extent that will affect the crops also won’t be known until harvest.
Last year, oat crops had some severe problems with lodging affecting quality, but luckily crops so far this year haven’t encountered the same issues, Enns said. “The general crops overall are not showing as much (lodging), especially in the Red River Valley,” he said. “Last year we saw it affect quality… so I think we’re a step ahead at this point anyways, but it’s not in the bin yet.”
Prices in the Red River Valley are on the low end, but still similar to last year’s prices, Enns said.
“I know last week they were offering $3 (per bushel) off the combine; you could have sold for $3.25 (per bushel) a little bit earlier,” he said. “We know that the carryout is going to be a little bit lower than it normally is, so there could be some demand down the road, especially closer to springtime. Could that reflect on higher prices? That’s to be determined.”
In-furrow technology can protect and nourish the seed in its most vulnerable emergence stage. So, are in-furrow options like starter fertilizer, micronutrients, seed treatments, fungicides, nitrogen stabilizer, and fertilizer-compatible insecticides worth the money?
They can alleviate plant stress that clips yield potential. “You never want your crop to have a bad day,” says Fred Below, University of Illinois crop physiologist. His research finds that combining targeted crop inputs can deliver more yield than the sum of their parts used individually. “Top corn genetics have the potential for 600 bushels per acre. Yet, the U.S. corn yield average is around 170,” Below says.
Agronomically, “the advisability of in-furrow technology depends on soil test recommendations,” says Dan Kaiser, University of Minnesota nutrient management specialist. “If your soils already have high nutrient levels, in-furrow technology may not deliver an advantage. In poorly drained or cold soils, you may see an advantage. Of course, there’s not just one way to farm. Each situation is different.” Financially, it’s a tough time to be adding any input costs, says Gary Schnitkey, University of Illinois farm management specialist. “We advocate that you cut $100 per acre in costs to break even, assuming you don’t increase yields,” says Schnitkey. “If you make that investment in in-furrow technology, you have to get yield from it. Do the math.”
One major provider of in-furrow technology is West Central Distribution, a Willmar, Minnesota, wholesale distributor of crop protection and production inputs. It offers the Leaders of In-Furrow Technology (LIFT) package to retailers in 23 Corn Belt states. “Against the backdrop of lower commodity prices and the intensified focus on production techniques, LIFT capitalizes on new findings in nutrient-efficiency management and delivery technology,” says Dean Hendrickson, LIFT vice president of marketing. LIFT partners with BASF, FMC, Dow’s N Serve, and Nufarm customized seed treatments for one-pass planting and input delivery. “You choose from among the best products, at the best time, delivered in the furrow at planting, to preserve seeds’ maximum theoretical yield,” says Hendrickson. “Quick, even seedling emergence, along with disease and pest protection, should lower plant stress and capture the most growing-degree days.”
Here’s a closer look at LIFT’s individual component options.
Looking to unlock nutrients from soils and make them available to your crops? That’s the premise behind chelated micronutrient mixes and chelating agents. One such product that frees up tightly bound nutrient ions is Levesol, says Brian Kuehl, West Central director of product development. “It releases zinc (ZN), iron (Fe), copper (Cu), manganese (Mn), and P (phosphorus) ions and keeps them in soluble, plant-available form,” he says. “Levesol is the highest concentration of ortho-ortho EDDHA, a stable formula that protects very specific positively charged nutrients,” says Steve Roehl, Leaders of In-Furrow Technology (LIFT) research data analyst and plant scientist. “It makes them soluble for plant uptake while preventing them from bonding with soil components and other negatively charged plant nutrients, thus, increasing their plant availability.”
Other Levesol-containing product options include:
“It frees up iron, preventing soybean iron deficiency chlorosis by keeping Fe2+ in solution,” Roehl says.
Chelated with Levesol, this product delivers N, P, potassium (K), Fe, Cu, Mn, and Zn in-furrow to get seedlings off to a strong start, Kuehl says. About 25% of U.S. acres use liquid fertilizer in-furrow, according to West Central market research.
Chelated nutrient products’ efficiency depends on how strongly they hold the ions (charged nutrient particles), says Dan Kaiser, University of Minnesota nutrient management specialist. Some are held more strongly by the soil than others. Kaiser’s 2014 Levesol trials found that the product increased early corn growth “that did not translate into yield,” he says. “The growth response may have been a positive reaction to in-furrow starter P. I have not seen the full set of Levesol data.”
Kansas State University Levesol 2014 trials also found no yield results from its use in corn. “We measured more P in corn tissue and grain; that’s an indication that it’s putting more P in the plant,” says Dorivar Ruiz-Diaz, who did the research. He is KSU’s Extension soil fertility and nutrient management specialist. “With just one year’s data, I cannot say you will see a yield increase, because we need more data, but it’s getting the P into the plant tissue and grain,” he says. Levesol and related products are being or have been tested by 41 researchers in 29 states, including land-grant universities. “Starter treatments cost more per unit, so account for early-applied nutrients in later application rates to avoid waste,” says Kaiser. “The likelihood of a yield benefit to starter fertilizer is fairly rare, maybe one year out of 10, like in a wet spring. Broadcasting nutrients isn’t a horrible way to go.”
Soybeans, grain corn, longer-season cereals, increased canola yields and fewer frost damaged crops: these all point to the reality of climate change and its effects in Western Canada. “Global warming is happening and it’s caused by humans,” Thomas Homer-Dixon told the Grow Canada Conference audience in Ottawa last week. The researcher from the Centre for International Governance Innovation of Global Systems at the Balsillie School of International Affairs in Waterloo, Ont., said the atmosphere is failing to release about a watt per sq. metre of energy when compared to the long-term mean. It doesn’t sound like much until the math is added up to show that it represents the heat value of 400,000 Hiroshima-sized bombs going off on the planet every day. He said that sensational statistic puts the issue into perspective.
All that additional energy will result in global average temperatures more than doubling the 1 °C increase on which the Paris Accord’s climate change plan is predicated, he added. “There is a less than 20 percent chance that we will hold it to 2 °C.” Homer-Dixon said the food crops that the world grows evolved and were developed during a time of stable temperatures and weather conditions. “These are not those times,” he said. Homer-Dixon said farmers, government and the food industry need to be planning for more extreme weather conditions and far greater food insecurity. Kevin Folta, a professor and chair of the horticultural sciences department at the University of Florida, told the conference that many experts are focusing on mitigating climate change, but farmers and the industry need to start reacting to the effects now. “Mitigation discussions will follow,” he said. Homer-Dixon said weather effects from the rapidly heating planet are already being experienced, and climate change is still in its early days.
The erosion of the Arctic sea ice is causing more aggressive change in northern latitudes, which has thrown the polar vortex out of its normally abnormal patterns because of the loss of low-pressure troughs that often were appearing in the north. This is an overly simple description of the climate change event, but the result is the same: very regular, very extreme waves in the counter-clockwise movement of air around the North Pole result in violent, north-south swings in the jet stream. These waves of air movement cause protracted flows of dry and wet, hot and cold conditions.
Homer-Dixon said farmers could expect to see bigger storms, more rain near coasts and a greater chance of extreme droughts in the middle of the continents. “Just because it is warming in the (Canadian Prairies), extending growing seasons and allowing more cropping choices right now, doesn’t mean it will always work out,” he said. Mapping of credible weather models to 2080 and beyond shows that drought will likely be the norm for much of the United States in the summer with extreme heat losses to the cereal crops and many oilseeds. Parts of Western Canada from the Alberta and British Columbia Peace district to southeastern Saskatchewan appear to benefit with additional moisture and warm conditions, but southern Alberta, western Saskatchewan and Manitoba are not projected to be so lucky. Folta said farmers need to be acting now to adapt to the change that is currently upon them. He said it’s important to lobby for more research about pests moving in from southerly regions, but new, adapted crops also need to be developed and farmers and producers must collect and share all the data they can from their farms. “There is a lot research that needs to take place quickly,” he said about the need to move to precision agriculture. “I call it the farm to dork movement,” he said about the need to put data to work in plant breeding and environmental research. “Compared to 1950, you have two more weeks of growing season,” he said.
That advantage, when combined with more extreme temperature swings, is causing fruit production to suffer as trees are prompted to bud earlier, only to have the entire year’s crops destroyed by frosts.The researchers suggested that farmers should consider drought-proofing water projects and infrastructure changes that might otherwise take time, resources and government lobbying to achieve. Homer-Dixon said plant breeders have been forced to stretch their genetics to find genes capable of withstanding prolonged mid-season drought or temperature swings during flowering. Both researchers said mitigation strategies for climate change will buy some time, but the overall plan for agriculture and food needs to be focused on a hotter, more violent environment.
Bacterium effective when dusted on plants
The successful agent for destroying pesty insects, the microscopic bacterium, Bacillus thuringiensis, is most effective when it is dusted onto tobacco or other plants…. The bacteria are now recommended for use against tobacco budworms and hornworms. From known results they look promising as biological control agents.
Bacillus thuringiensis, or Bt, is still used to combat agricultural pests. Different strains of the bacterium target different insects; one strain can even kill mosquito larvae in water. Organic farmers dust or spray Bt on crops and consider it a natural insecticide. In conventional farming, Bt DNA is often inserted into a plant’s genome, creating genetically modified crops that make their own pesticide. In 2015, 81 percent of U.S. corn and 84 percent of U.S. upland cotton contained Bt genes.
In many fields this year, soybean aphids have been a no-show. However, that’s not the case everywhere, says Bruce Potter, University of Minnesota (U of M) Extension integrated pest management specialist. He says fields at the U of M Southwest Research and Outreach Center near Lamberton have experienced aphid infestations.
Even if you’ve so far had no soybean aphid infestations, Potter says it’s a bad idea to make the following soybean aphid assumptions.
1. It's too late for soybean aphids to hurt yield
Potter says aphid populations are late developing this year in some areas. Due to planting delays, soybean development also lags in some areas, such as southwestern Minnesota. Last week, soybeans were just beginning to fill in parts of Minnesota, says Potter. Several more weeks exist in which soybean aphids can damage yield potential. Yield can be lost until the R6.5stage (between full seed and beginning maturity). “If populations continue to increase and persist late, we could still lose 10 to 15 bushels (per acre) in most plantings and 40% in late-planted soybeans,” Potter says.
Aphid control does require an insecticide and application investment, he says. Still, in states like Minnesota, soybean aphids are a consistent threat to yield loss, he adds. “Particularly because of the tight farm economy, you should have budgeted for foliar soybean aphid control in 2016,” he says. “If you don’t need to treat – great. That goes on the black side of the balance sheet. If you do need to treat to avoid economic loss (remember the difference between economic injury level and economic threshold), you are likely to have a good return on your investment.” Use this economic/action threshold for soybean aphid treatment until soybeans reach the R6 stage.
2. I don’t have an aphid problem because I looked last week and populations were low
Did you look effectively? On more mature soybeans, aphids are now distributed throughout the soybean canopy. It makes scouting more difficult, says Potter. “If you are seeing spots of honeydew on lower canopy leaves, you are (or were) likely to be over 250 aphids per plant,” he says.
In some fields, aphid populations now are mostly in the small white dwarves in the lower canopy. Count these aphids. They reproduce rapidly, and these populations will begin to produce normal aphids later in the season. These populations can build to many thousand aphids per plant late in the season. Aphid populations rapidly can change in a week. In many fields, a large number of winged aphids were being produced on crowded plants earlier this month. Look for a large percentage of colonies of aphid nymphs with darker heads and wing pads as a clue that aphids may be preparing to leave the plant and perhaps the field, he says. Conversely, plants (or leaves) with few aphids are now being colonized by winged aphids. Fields with high populations can rapidly decline. Winged aphids leave, and fields with low aphid populations can rapidly increase with winged aphid immigrants.
Often they arrive in fields that previously had few aphids and few predators. Younger soybean plants present a particularly attractive landing strip. The comings and goings of the winged ones make predicting population increases more difficult. This migration happens every year about this time, and soybean aphids can be transported long distances on weather systems. Fortunately, you have some free helpers in the field. “We are just now starting to see a small amount of aphid mortality from fungal pathogens,” says Potter. “Look for groups of dead, discolored aphids. High humidity and cool temperatures will favor an epidemic.” Potter says population collapses from disease, predation, or emigration are the reason the soybean action threshold includes the caveat of “soybean aphid populations are increasing.”
3. I sprayed earlier, so I won't have a problem
Keep watching. Rapid population increases and the winged aphids that are now free to move about the country are two reasons that you need to scout until R6. “Earlier-sprayed fields may be reinfested since the insecticide removed predators and parasites. This can key explosive soybean aphid population increases,” Potter says. “It is one reason we recommend waiting to spray until the 250-aphids-per-plant aphid threshold,” he says. “Fields that were sprayed early should be watched closely for recolonization by winged aphids.” Pyrethroid insecticides are also not performing as well as they have previously in parts of Minnesota. “Some of these have occurred outside the area where there were issues last year,” he says. The problem fields have not yet been documented with an assay, but they do not seem to be due to application errors.” Check aphid control three to four days after an insecticide application, says Potter. Shaking the plant can dislodge alive but dying aphids. An insecticide-resistant aphid population is revealed by dead predator insects and pockets of healthy aphids with dead aphids in the remainder of the field.
Be wary, wine lovers: Climate change can muck with your merlots. By tracking the timing of French and Swiss grape harvests from 1600 through 2007, scientists have discovered that the link between high temperatures and drought conditions, a combination crucial for fine wine production has broken down since 1980.
Warm temperatures hasten grape maturation, requiring early harvests. In the past, warm springs and summers often coincided with scarce rainfall that produced good harvesting conditions. Climate change, however, produces warm temperatures in France and Switzerland independent of low rainfall. Harvest-delaying rainstorms increasingly prevent winemakers from collecting their warmth-matured crop at the optimum time, worsening wine quality, the scientists report March 21 in Nature Climate Change. The new work adds to the list of ways that climate change affects the wine industry, such as shifting the regions with the ripest climates for growing grapes.
Problem weeds give Steve Kaltenheuser a headache. The difficult-to-kill eyesores like water hemp spurred the Ames, Iowa, farmer to get creative this past summer. Kaltenheuser modified his son’s Miller Nitro 4365 sprayer into a bean rider to go through his 15-inch soybeans. His sprayer’s heavy-duty boom allowed him to mount seats from an old soybean rider. He then added umbrellas to protect the riders from the sun. This summer, the crew covered 1,400 acres that he didn’t think would be feasible to walk due to narrow rows.
The riders then sprayed the culprit, waterhemp, as they rode through the problem patches. Kaltenheuser had to innovate because of an early-season misstep with his herbicide program. In the spring, he incorporated Treflan followed by a second incorporated application of Authority First. “Both of those programs worked very well, and the beans stayed really clean,” he says. The issue came with his postemergence application. “I waited a little too long to hit them with Flexstar and Resource,” says Kaltenheuser. “I wanted to get them close to canopy, and that was a mistake.”
A few years ago, he switched to non-GMO soybeans. This enabled him to pick a high-yielding variety but still save seed costs. For Kaltenheuser, it’s about the economics. He grows the non-GMO variety because he’s able to reinvest the saved seed cost into his herbicide program. “When Roundup came out, it made everyone look like a professional,” says Kaltenheuser. “We’re losing that. There are more weeds out in cornfields than people realize. It’s going to become a lot more labor-intensive. To get ahead of it this year, I sprayed all the corn after brown silk with 2,4-D to try to prevent the waterhemp from going to seed.” In the past, Kaltenheuser hadn’t had any problem controlling the weeds, but this year was the perfect mix of the wrong conditions in his area – like a lack of rain.
“I remember killing tall water hemp easily a few years ago. Now water hemp has to be killed when it’s really small,” says Kaltenheuser. Because of that, he relies on a herbicide’s residual benefits. Water hemp has been causing plenty of people headaches. “Water hemp has been really, really bad,” says Paul Kassel, Iowa State University Extension agronomist. “Glyphosate is no longer dependable. There’s also some confirmed resistance with Flexstar.” The answer may be returning to practices from the past. “Farmers are going to have to double up on soil-applied products,” says Kassel. He thinks farming is going back to how it looked in the 1970s and 1980s. The days of adjusting to programs based on the weeds in the field are gone. “We’re going to have to plan on what might be there,” says Kassel.
Shotgun approaches are no longer going to cut it, says Kassel. Herbicide programs will take more time and investment.
Double incorporation may be necessary for best results, says Kassel.
“There’s been an interest in using residuals postemergence,” says Kassel. “I hear a lot of innovative approaches. Residual products don’t work unless it rains, so farmers have been incorporating it. I think people are adapting very well.”
Herbicides will still do 99% of the work, says Kassel. Yet, he predicts more intensive herbicide planning and management will be needed. Tillage is another tool Kassel believes farmers will turn to if needed. “I know of a few farmers who have pulled their cultivators out,” says Kaltenheuser. “I’m hoping I don’t have to do it again, but it’s a better option than walking the beans." “The biggest thing I’m going to change next year is that I’m going to spray early on the post application,” says Kaltenheuser. “In the future, I’ll do anything I can to lower the seed bank. Back in the old days, before we had Roundup, it was a big concern if weeds went to seed. I’m going to have to look at weed control a lot more like I did in the past.”
How resistance spreads
Surprised at how a field full of herbicide-resistant weeds results? It had its origins years earlier. Birds do it, bees do it, even educated fleas do it, as the old Cole Porter song goes. So why can’t water hemp (or weeds) do it? That last line probably isn’t funny if you’re battling herbicide-resistant weeds. Still, it says much about the way herbicide-resistant water hemp infests your fields in the first place.
That field full of weeds water hemp, Palmer amaranth, marestail, or something else started some time before.
Field flirters
It’s akin to when a point guard catches a cute courtside TV reporter’s eye. Water hemp is dioecious, with male and female plants. Sparks quickly fly. “Since water hemp is dioecious, pollen is already moving around,” says Pat Tranel, University of Illinois (U of I) weed scientist. “Pollen can be viable up to 120 hours, and it can move ½ mile from the pollen source.”
Initially, resistance is rare
Every herbicide selects for its own failure, even a brand-spanking-new one. In every weed species, rare genetic biotypes exist that resist a herbicide. This varies among herbicide sites of action, says Ian Heap, director of the International Survey of Herbicide-Resistant Weeds. Rare herbicide-resistant biotypes exploit management uniformity, much as a star center who shreds double-teaming defenders. Every herbicide application heightens the odds that resisters survive.
How quickly?
Really quick in the case of some weeds like Palmer amaranth. It’s double trouble if the weeds are herbicide-resistant biotypes. By producing up to 1.8 million seeds per plant, glyphosate Palmer amaranth infested 20% of the field areas in less than two years in a 2008 University of Arkansas analysis. You may be doing a laundry list of best-management practices to forestall resistance. Rotating herbicides’ sites of action. Lacing your row-crop rotation with small grains. Regularly scouting fields and rounding oddball weeds. Unfortunately, all can be for naught due to an often overlooked resistant-weed spreader: waterfowl. Kevin Bradley, University of Missouri Extension weed specialist, reports an MU trial found that weed seeds can remain intact after passing through a mallard duck’s digestive system. Think you’re cruising in a corn planter that goes 10 mph? It has nothing on mallard ducks, which can fly up to 48 mph for up to 38 hours.
Potentially, they can move weeds like Palmer amaranth, waterhemp, common lambsquarters, giant foxtail, and smartweed nearly 1,740 miles in 1½ days
Glyphosate seems synonymous with herbicide-resistant weeds. In most cases, though, weeds resist multiple sites of action. Here are herbicide action sites that water hemp resists and initial U.S. confirmation year.
“Water hemp won’t stop at six herbicide sites of action,” says U of I’s Tranel. “It will develop resistance to anything being developed, whether it’s the seventh, eighth, or ninth.” It’s important to note that no waterhemp biotype exists in all six herbicide sites of action. Still, multiple site resistance abounds. In 2009, for example, weed scientists confirmed an Illinois water hemp biotype that resisted four sites of action.
Glyphosate-tolerant water hemp and Palmer amaranth are bad now, but imagine how fearsome they could be if this weed equivalent of pro basketball’s Stephen Curry and LeBron James teamed up together! Could they cross-pollinate to create some sort of freak frankenweed? Now that would be bad – and it is currently happening with pigweed species like water hemp, Palmer amaranth, and spiny amaranth. “There is some hybridization occurring,” says Kevin Bradley, University of Missouri Extension weed specialist. “There are some weeds I walk by and say, ‘Wait a minute. That doesn’t look quite right.’ The leaves will look like water hemp, but the head looks like Palmer.” 2012. That’s the year Bill Molin, USDA-ARS plant physiologist in Stoneville, Mississippi, began tracking spiny amaranth and Palmer amaranth hybrid. Resistant to both glyphosate and ALS herbicides, the hybrid is the result of a cross between Palmer amaranth growing in a cotton field and spiny amaranth in a neighboring pasture.
Palmer and water hemp are doing it, too
Researchers at the University of Illinois and Colorado State University have also discovered amaranthus hybrids of Palmer amaranth and waterhemp. “The hybrids often look similar to the normal variation of the species,” says Pat Tranel, University of Illinois weed scientist. In many cases, hybridization between species can only be confirmed by genetic analysis, says University of Missouri’s Bradley.
The good news
Imagine if that imaginary basketball player brimmed with hybrid vigor by crossing Curry with James. Fortunately for you, this hybrid vigor so far doesn’t extend to amaranthus species. Palmer amaranth and waterhemp shoot bricks when it comes to hybridizing. In 2011, field studies by Colorado State University weed scientists showed that glyphosate-resistant Palmer amaranth transferred glyphosate resistance to:
Remain watchful, though.
“I think the danger in Missouri is with pastures between crop fields,” says University of Missouri’s Bradley. “There, Palmer amaranth that transfers resistance to spiny pigweed in the middle of a pasture is something of which we are aware.”
It’s akin to the anxiety a coach feels when his star forward, at midshot, flashes an on-court smile at a cheerleader. “Wherever these two plants are close together, there is a chance to hybridize,” Molin says.
How to control?
Double- and triple-team it just as you would a 40-point-a-night forward. “Broaden the spectrum of herbicides used,” says Molin. It’s important that this spectrum include herbicides with multiple effective modes of action, he says. Look beyond the field, too. Control weeds in fencerows, ditches, and other places these weeds can grow, he says.
Even more good news
Low hybridization of pigweed species also means low rates of hybridized seed being shed. Still, bear in mind that the average water hemp plant sheds 250,000 seeds. If water hemp hybridizes just 0.2% of the time, the plant still sheds 500 seeds that can germinate and emerge the next year.
No new tools are on the horizon, but there’s still technology to help you manage weed issues.
Herbicide-resistant weeds aren’t man-made, but that’s not to say man isn’t to blame. “Farmers have been selecting for herbicide-resistant weeds,” says Lisa Behnken, Extension educator for the University of Minnesota. “They do that by being very predictable.” Herbicide-resistant weeds occur naturally in the weed population. Farmers became more predictable, and the repeated use of the same chemical tools caused resistant weeds to become a larger part of the population. “Waterhemp became resistant to ALS herbicides before glyphosate technology was even around,” says Behnken.
Nozzles
Missing free throws frustrate the crowd on game day. The same goes for weed specialists when applicators continue to use flat-fan spray nozzles. “They haven’t adopted the air-induction nozzles,” says Fritz Breitenbach, Extension specialist for the University of Minnesota. “We’ve done enough work to show that they’re superior.” It’s a simple correction that could change the outcome of the game.
Mapping
In a University of Minnesota study, Behnken found that only 9% of farmers were mapping weeds. “We’d like to see that change,” says Behnken. As you are going across the fields during harvest, map the weeds. That allows you to spend money wisely on your herbicide program, and you can focus on the spots where you have more difficult problems. You only have one first chance to prevent a weed before it gets established, says Russ Higgins, University of Illinois Extension educator. Once it’s established, it becomes widespread across the field, and then it becomes costly and difficult to control.
Make multiyear plans
Last-minute-play calls are no longer acceptable management plans. Weed control needs to be a system approach, which includes multiple practices, says Behnken. “The majority of farmers are lucky if they make a one-year plan.” Instead, she recommends farmers create multiyear plans with backup plans. In those plans, Behnken recommends tactics that have both chemical and nonchemical tools. Also, don’t include the same herbicide or mode of action every year. Few new weed-control tools exist, says Breitenbach. “They have to rediscover old tools,” he says. Breitenbach recommends that you go back to incorporating cultural practices for more comprehensive weed control, such as:
Ever run into the former high school wallflower at a class reunion who now mimics a flashy NBA star? In the weed world, that’s water hemp.
Why Water hemp?
Waterhemp used to just line banks near streams and rivers. If this small-seed broadleaf did meander into your crop fields, tillage would bury it. No more. These days, less tillage ensures this shallow soil dweller has ample germination and emergence.
Season-long emergence
This emergence – which has started as early as late March in Illinois – can continue all through July, says Pat Tranel, University of Illinois weed scientist.
Late flusher
Late-season flushes separate waterhemp from other weeds. A 1996 Iowa State University study showed that most wooly cupgrass emerged May 10-20. Peak waterhemp emergence didn’t start until June 24.
Management
1 Million
The seeds one waterhemp plant can make with no competition, such as in a prevented-planting case. 44% That’s the soybean yield loss that can result from season-long water hemp infestations thicker than 20 plants per square foot. It pays to control weeds early. That’s because 1% is the soybean yield loss that results when control occurs on 6-inch water hemp with infestations of fewer than 10 plants per square foot.
Location
Water hemp is the league scoring champ when it comes to corn and soybeans. It infests row crops all the way from Louisiana to North Dakota. It’s particularly thick in Iowa and Missouri, infesting 90% or more of soybean acres.
That’s some wingspan. The seed head can reach up to 3 feet long! Palmer amaranth is an aggressive, invasive weed native to the desert regions of the southwest U.S. Facing a drought? That won’t slow Palmer. Given it originates from the desert, it’s drought-resistant. Palmer is akin to a towering center who grows every game. It grows nearly 2 inches per day. It’s also as prolific a scorer as a 3-point shooting guard. One plant can produce 1 million seeds, says Jeff Gunsolus, University of Minnesota weed specialist. The cheapest way to manage a weed is to prevent it from getting established in a field, says Iowa State University’s Bob Hartzler. He encourages farmers to hand-weed, especially the female plants, before it is established. Why is Palmer a challenge? It’s already knocked out two main defenses. Most populations resist glyphosate and ALS-inhibitor herbicides. If you let Palmer amaranth play out all season, yield loss could be up to 91% in corn and 79% in soybeans.
Double team
It’s easy to confuse Palmer and water hemp seedlings, says Hartzler. Water hemp has a shorter petiole and longer, narrower leaves than Palmer. The best trait to differentiate seedlings is the presence of petioles longer than the leaf blade on Palmer. Once they have flowered, the sharp bracts on female Palmer are a dead giveaway.
Management
Diversity of weed management must expand beyond herbicides, says Mike Owen, Iowa State University Extension weed scientist. Repeated use of the same chemical tools selects for resistance. Instead, try a combination of cultural practices and chemical tools for control.
Prevention
Harvest infested fields last. Otherwise, your combine will spread Palmer seeds. Flag areas where you spot Palmer amaranth, says Russ Higgins, University of Illinois Extension educator. When it’s in the introduction stage, there’s still an opportunity to eradicate it before it becomes a widespread threat, he says.
Location
Palmer infests row crops from Louisiana to Ohio to North Dakota. In a 2015 survey, it was on 60,000 acres in Kentucky, according to University of Kentucky’s J.D. Green. Nearly one third of Illinois counties have documented cases of Palmer.
Lack of crop diversity and no-till spur this winter annual’s spread. Marestail is number one, but not in a good way. It was the first glyphosate-resistant weed confirmed in the U.S. when it surfaced in Delaware in 2000. Since then, it’s moved at full speed into other areas like the Midwest.
Fall forward
Marestail rosettes often appear in the fall in the northern U.S. A fall application of 2,4-D or dicamba plus chlorimurin or metribuzin products offers the best residual control, says the University of Missouri’s Kevin Bradley. Preemergence herbicides are a must! Larger weeds are tough to kill. Limited postemerge corn options exist, and there are even fewer in soybeans, say University of Nebraska weed scientists. 200,000 The average number of seeds produced by one marestail plant. Of these, 80% will emerge off the plant, according to Purdue University.
Springing back
Spring and summer flushes of marestail south of I-70 in the Corn Belt are becoming more common. This likely is signaling a change in plant biology, due to herbicide selection and changes in crop rotation.
Why not rye?
A cereal rye cover crop planted after corn, soybean, or wheat harvest can nix fall marestail emergence and aid control. “A glyphosate and Fierce preemerge provides nearly 98% control of marestail at planting,” Bradley says. “Take out the cereal rye, and the same treatment provides just 40% control.” 83% The percentage of yield reduction in a soybean field where marestail is not controlled. Yield losses are less certain in corn.
Location
Glyphosate-resistant marestail migrated to the mid-South after its 2000 Delaware discovery. It now infests 90% of Kentucky soybean acres. It’s since moved to the Midwest and now plagues an estimated 30% of Iowa’s soybean acres.
This old fencerow and ditch dweller now infests crops. Its 17-foot maximum height would make it any team’s starting center. Typically, though, it’s 1 to 5 feet taller than the field’s crop. Giant ragweed biotypes exist that have resisted ALS inhibitors (Pursuit) in seven states and EPSP synthase inhibitors (glyphosate) in 12 states. There are confirmed giant ragweed biotypes resisting both herbicide action sites in Ohio, Minnesota, and Missouri. A single plant can produce an estimated 1 billion pollen grains during its lifetime. Its pollen triggers more than allergies; it creates cross-plant pollination potential. This creates genetic diversity that creates more herbicide-resistance potential.
Why is it a problem?
Giant ragweed used to dwell in undisturbed areas like fencerows and drainage ditches. Since the late 1980s, it’s moved into cropland. It’s now prevalent in cropland due to:
Management
The most effective herbicide programs combine preemergence and postemergence herbicide treatments with two or more herbicide sites of action. Scouting after the first post trip can pinpoint escapes.
Location
Giant ragweed infests more acres in the eastern Corn Belt. In Kentucky, for example, giant ragweed infests 40% of soybean and corn acres, Still, infestations occur farther west, with infestations estimated at around 10% in Iowa, mainly in north-central regions of that state.
The U.S. government will test various foods for exposure to glyphosate, the active ingredient in several herbicides. Tests on foods including soybeans, corn, milk and eggs are set to begin this year, says Food and Drug Administration spokesperson Lauren Sucher. In 2014, the Government Accountability Office called on the FDA and the U.S. Department of Agriculture to strengthen their monitoring of glyphosate, the most widely used herbicide in the world. Previously, methods for such testing would have been too costly and labor intensive, Sucher says, but new methods now make it more feasible. Bottom of Form Evidence for glyphosate’s ill effects is mixed and often clouded by spin on both sides. But there is little doubt that human exposure has increased along with a sharp increase in the herbicide’s use.
Introduced in the 1970s in Monsanto’s Roundup, glyphosate soon dominated the pesticide market; more than 250 million pounds are applied yearly to agricultural lands in the United States today. Initially, the herbicide, which interferes with an essential enzyme found in plants, was primarily used to clear weeds from fields before planting. In the 1990s, the development of crops genetically engineered to tolerate glyphosate, and the expiration of patents, led to a dramatic increase in its use, including applications to fields during growing season. Today, an estimated 90 producers in 20 countries make glyphosate, which is also used throughout the world for controlling house and garden weeds. Despite its widespread use, regulatory agencies have concluded that the herbicide has low toxicity and there has been no routine testing for glyphosate in food or people. A onetime study by the USDA’s Agricultural Marketing Service in 2011 found glyphosate residues in 90 percent of tested soybeans and a glyphosate metabolite in more than 95 percent of the samples. All the levels were below the acceptable dietary level for soybeans established by the U.S. Environmental Protection Agency of 20 parts per million, although the highest concentration was a close 18.5 ppm.
Numerous toxicology studies, many conducted by industry as required by the EPA, have found that glyphosate is relatively harmless. Animals don’t have the enzyme that glyphosate acts on and therefore shouldn’t be directly affected by it. Other research suggests ill effects. Yet evidence of harm isn’t clear-cut and has been stained by a handful of much-publicized and widely discredited studies. Such a muddled research history is all the more reason for standardized studies by independent scientists and for general monitoring, says Ana Soto, an expert in endocrine disrupting chemicals at Tufts University School of Medicine in Boston.
“If there is evidence of problems that keep coming up, and the chemical is in such widespread use, we need to study it,” says Soto. “That’s not revolutionary, that’s common sense.” The World Health Organization’s International Agency for Research on Cancer conducted its own review of more than 400 studies in 2015 and rated glyphosate as “probably carcinogenic to humans.” This designation of a 2A carcinogen is in part due to finding limited evidence from real-world exposures in humans. Studies in Canada, Sweden and the United States, for example, have shown that people who work with glyphosate-based herbicides have increased risks for non-Hodgkin’s lymphoma, although a separate large U.S. study found no such link. Designating glyphosate as “probably carcinogenic” also rests on evidence from studies of cancer in animal experiments and mechanistic evidence of how damage from glyphosate might occur at the cellular level. Other agents classified by the IARC as having similar strength of evidence for cancer-causing capabilities include the insecticide malathion, indoor emissions from wood-burning stoves and red meat.
The IARC assessment of herbicides that include glyphosate includes only studies that are in the public domain and can be independently reviewed, says Kathryn Guyton, senior toxicologist at the IARC Monographs Program and lead author on a paper summarizing the findings in the May 2015 Lancet Oncology. Therefore, many unpublished industry studies, which are accepted by regulatory agencies in the United States, were excluded. Also excluded are studies that don’t provide enough data for independent analysis, such as a widely disputed study by French researchers linking Roundup to kidney problems and tumors in rats. Following the IARC’s designation, the European Food Safety Authority reassessed glyphosate’s risks to health and the environment. The EFSA assessment, which was more narrowly focused on glyphosate alone and included some studies not reviewed by the IARC, was published in November 2015. It concluded that glyphosate “is unlikely to pose a carcinogenic hazard to humans,” and it raised the acceptable daily intake of glyphosate from 0.3 milligrams per kilogram of body weight per day to 0.5 mg/kg body weight per day.
But it also pointed to gaps in both toxicological and environmental data and established for the first time an “acute reference dose” the maximum amount that can be ingested in a short time period based on new toxicity data from rabbit studies (also 0.5 mg/kg body weight per day). The FDA’s decision to monitor food for glyphosate residue coincides with a statement of concern over glyphosate exposure published online February 17 in Environmental Health. The statement cites some dubious science (such as the retracted rat-tumor study). Nonetheless, given the conflicting evidence, its recommendations seem sound, says Soto. These include routine testing for glyphosate residues in human fluids by the U.S. Centers for Disease Control and Prevention. Monsanto spokesperson Charla Lordsays that if the FDA decides to rigorously test for glyphosate residue, the company is confident that the monitoring will reaffirm the product’s safety.
Randy Anderson has studied weeds and their elusive ways since his beginning years as a researcher back in the early 1980s. “I was looking then – as I am now – for alternative control methods for weeds that would let growers use fewer herbicides,” says Anderson, an agronomist at the USDA Agricultural Research Service North Central Agricultural Research Laboratory in Brookings, South Dakota. “That work led me to the study of population dynamics in weeds.”
From more than 30 years of watching weeds, Anderson has learned a critical lesson: Weed populations have the tenacity to evolve, shape shifting to changing conditions imposed by humans. Weeds are most adept at adapting when varying conditions occur in predictable patterns.
“The most notable example I’ve seen over the years is the development of herbicide-resistant weeds,” says Anderson. “Despite use of herbicides, we haven’t achieved control. Weeds are still there all the time.” Weeds are getting harder to control not only because of an increasing resistance to herbicides, but also because the hardiest species are survivalists. “We’ve eliminated the easy-to-control weeds, while our practices have served to select for the more difficult-to-control weeds like Palmer amaranth and jointed goatgrass, for example,” he says. Yet, weeds have their limitations, and exploiting these in a synergistic, whole-system approach offers potential for significant control. “I believe we can get to the point in the future where we can control weeds using a system of herbicide-free no-till,” says Anderson. Whole-system weed management is a multitactic approach comprising complex rotations, no-till, cover crops, synergism, and soil health. “A single cultural tactic has minimal impact because the pest population is elastic and flexible. It can easily adjust to one tactic,” says Anderson. “If several tactics are used in different ways to suppress weed-population growth, for instance, weeds have trouble adapting. Thus, weed density declines over time.”
A decline in weed populations offers a savings in input costs because of reduced use of herbicide. “An economic assessment of farmers in northeastern Colorado showed that producers using a multitactic approach to weed control were spending half of what conventional winter wheat/fallow farmers were spending for weed control,” says Anderson.
Whole-system weed management incorporates five cornerstones:
1. A broader perspective on managing weeds
“Consider that weeds are a natural part of your farming system and focus on managing them rather than eliminating them,” he says. “For instance, weeds can add diversity to the plant community and favor beneficial insects. We tend to see weeds as an enemy, thus, emphasizing elimination rather than management. This elimination approach leads to resistant weeds.”
2. Improved soil health
When soil is healthy, it tends to produce crops that compete well with weeds. “Research shows that when you improve the health of the soil, the crop is more tolerant of weeds,” says Anderson. “Crops grown in healthy soil have healthier seedlings, which access more nutrients and moisture earlier. Healthier crop seedlings can outgrow weeds.” Weeds are bound to come increasingly in check as you continue working to improve the health of your soils. “I’m noticing differences between past and present producers and how they view their soil,” he says. “When I started my career as a researcher, few farmers talked about soil health and what a weed could contribute.”
3. Systems complexity
Weed growth represents the first stage in the ongoing natural process of succession in plant life. “When the glaciers moved back, the first plants that moved in were weeds,” says Anderson. As farmers shape production systems with increasingly diverse and dynamic components, they create the systems complexity that shifts the plant and soil-life communities further along the continuum of succession. By contrast, says Anderson, “When we provide continuity of simple practices, we select for a certain plant community, and we give weed populations a chance to explode because they can adapt. The more complex the overall cropping system is, the easier it will be to control weeds and other pests.”
4. Crop diversity
“A systems approach would increase plant diversity in the rotation,” says Anderson. “All these crops would have different planting dates and differing growth periods, making it harder for weeds to adapt.” One rotation design that is effective in fostering dynamic pest suppression is a rotation arranged in a cycle of four, with two cool-season crops followed by two warm-season crops. “Diversifying crops with different planting dates within a life-cycle category, such as warm-season crops, for instance, accentuates the benefit gained with rotations comprised of two-year intervals of cool- and warm-season crops,” says Anderson. A warm-season sequence comprising corn and sunflowers, for instance, can be more beneficial than a warm-season sequence of corn followed by corn. “The key is having crops with planting dates differing by at least three weeks,” he says. “For example, corn is usually planted in early May, while proso millet and sunflower are usually planted in early June.” Adding cover crops and legumes increases the complexity needed to further confuse weeds.
5. No-till
Zero tillage reduces or eliminates the soil disturbance that encourages germination of weed seeds. “Tillage buries weed seed in the soil, which increases long-term survival of the seeds,” says Anderson. “Weed seeds die rapidly if left on the soil surface, where they are exposed to extremes in temperature. On the surface, they also experience alternate periods of wetting and drying. This process starts splitting the seed coat, causing the seed to deteriorate. Lying on the surface, the seeds are exposed, too, to predation by insects, birds, and mammals.” When no-till is used in conjunction with a diverse cropping system, weed control is improved. “Synergism between the two practices strengthens the cropping system,” he says. As whole-system cropping and weed management continue to evolve, Anderson sees a future where weeds play a balanced role. “If we took more of a systems approach, we wouldn’t spend so much time trying to eliminate that one aspect of nature that weeds represent,” he says. “Instead, we could invest more time and energy in simply growing more diverse crop communities.”
Each year, marketing representatives of agricultural chemical companies extoll the virtues of new herbicides. What they’re actually discussing are tweaks made in existing herbicide sites of action. The last truly new corn and soybeans herbicides were HPPD inhibitors that debuted around 20 years ago.
That said, there are some changes in existing corn and soybean chemistries that have recently been made, says Mike Owen, Iowa State University (ISU) Extension weed specialist. Owen highlighted some of them at this winter’s ISU Integrated Crop Management conference. The following changes also include the product’s site of action group number and the herbicide site of action.
Armezon Pro from BASF is a new herbicide for corn (field, sweet, seed, and popcorn). Armezon Pro is an EC formulation containing topramezone (Group 27, HPPD inhibitor) and dimethenamid-P (Group 15, very long-chain fatty acid inhibitor). It may be applied from corn emergence up to V8 stage or 30-inch-tall corn (12 inches tall for sweet corn). It provides burndown and residual control of some annual broadleaf and grass weeds. Use rate range is from 14 to 24 ounces per acre, depending on soil texture and organic matter.
DiFlexx from Bayer CropScience was registered for field, white, seed, and popcorn last spring. It’s a dicamba (Group 4, synthetic auxin) formulation with safener cyprosulfamide. It’s registered for preplant burndown, preemergence, and post-emergence application in corn. It has no planting restrictions due to safener inclusion. Postemergence applications can be made to corn up to the V10 stage. Observe the DiFlexx label recommendations for adjuvants. Use 8 to 16 ounces per acre with a seasonal total maximum of 32 ounces per acre.
Capreno from Bayer CropScience is a premix of tembotrione (Group 27, HPPD inhibitor) and thiencarbazone-methyl (Group 2, ALS inhibitor). It also contains the safener isoxadifen-ethyl and is now registered to be applied to V7 corn stage. Apply Capreno to field corn, silage, and white corn from emergence to 20 inches tall. Do not apply when corn is taller than 20 inches or has 7 or more leaf collars, whichever is more restrictive. MSO has been added as an adjuvant choice. All Bayer CropScience labels will include new pest-resistance management language. The language is generally more detailed and reflects the need to diversify weed management. Besides herbicide sites of action, seed-bank management is emphasized in addition to scouting, controlling weed escapes, and crop rotation.
Revulin Q from DuPont received EPA registration approval early in the first quarter of 2015. It’s a premix of dry mesotrione (Group 27, HPPD inhibitor), nicosulfuron (Group 2, ALS inhibitor), and a safener. Revulin Q is labeled for postemergence grass and broadleaf weed control in numerous types of corn including field corn grown for grain, silage, or seed; yellow popcorn; and sweet corn.
Cinch from DuPont (Group 15, very long-chain fatty acid inhibitor) can now be applied as part of a sequential soybean weed-control program. If Cinch is applied as a preplant surface, preplant incorporated, or a preemergence treatment, it can again be applied postemergence provided that the total rate during any one crop does not exceed 2.5 pints per acre. No more than 1.33 pints per acre of Cinch can be applied postemergence. Postemergence applications must be made at least 90 days before harvest. Cinch does not control emerged weeds.
Anthem Maxx from FMC is a premix of fluthiacet-methyl (Group 14, PPO inhibitor) and pyroxasulfone (Group 15, very long-chain fatty acid inhibitor) and replaces Anthem. Anthem Maxx has 4.3 pounds of active ingredient per gallon, double the active ingredient in Anthem. Anthem Maxx application rates will be one half the rate for Anthem. Anthem Maxx is registered for preplant burndown, preemergence, preplant incorporated, and postemergence application in field corn, sweet corn, popcorn, and soybeans. Postemergence applications in corn should be made through the V4 stage; in soybeans, it should be made through the V3 stage. Weeds should be small and actively growing. Observe application restrictions listed on the Anthem Maxx label. 0: The number of corn and soybean herbicides with a new site of action developed so far in this century.
Warrant Ultra from Monsanto is a premix of encapsulated acetochlor (Group 15, very long-chain fatty acid inhibitor) and fomesafen (Group 14, PPO inhibitor). This product can be applied preemergence and postemergence before soybeans reach growth stage R2, and it will control many annual grass and broadleaf weeds.
Encapsulating acetochlor provides a slow release of the herbicide and increases its potential to remain effective for a longer period of time. Warrant Ultra can now be applied to soybeans postemergence for extended residual control of some annual grass and broadleaf weeds.
Acuron from Syngenta controls annual grass and broadleaf weeds in field corn, seed corn, silage corn, sweet corn, and yellow popcorn. Acuron is a premix of S-metolachlor (Group 15, very long-chain fatty acid inhibitor), atrazine (Group 5, Photosystem II inhibitor), mesotrione (Group 27, HPPD inhibitor), and bicyclopyrone (Group 27, HPPD inhibitor). Acuron can be applied preemergence in all corn types listed. It may also be applied early postemergence in field, seed, and silage corn but not to emerged sweet corn or yellow popcorn because of potential severe crop injury. Acuron may also be applied in split application. Postemergence applications must be made before corn is 12 inches tall. Another premix called Acuron flexi may be available for 2016, but it had not yet received federal regulatory approval at press time. This premix contains the same active ingredients as Acuron, minus the atrazine. It’s for those areas where atrazine can’t be applied or where atrazine carryover concerns exist, says Ryan Lins, a Syngenta research and development scientist based in Minnesota. Owen notes most of Syngenta’s proprietary herbicides now have the Weed Science Society of America (WSSA) mode-of-action herbicide group numbers and revised resistance-management language included in the label.
FLEXSTAR (Group 14) and FLEXSTAR GT (Groups 9 and 14) labels now include an adjuvant statement that requires adjuvant products to meet the standards of the Chemical Producers and Distributors Association certification program.
Fierce XLT from Valent is a new premix registered for use in soybeans. Fierce XLT includes chlorimuron (Group 2, ALS inhibitor), flumioxazin (Group 14, PPO inhibitor) and pyroxasulfone (Group 15, very long-chain fatty acid inhibitor) and can be applied as an early preplant, preplant, or preemergence application. Preemergence applications of Fierce XLT must be made within three days after planting and prior to soybean emergence. Fierce XLT applications after soybeans have begun to crack or are emerged will result in severe injury. Do not apply Fierce XLT on soils with a composite pH of greater than 7.6. Do not perform any tillage operation after application, or residual weed control will be reduced.
