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Neonicotinoid Insecticide: What to Think about Before Treating Seeds

The old joke goes like this. This is how you know when it’s time for planting your corn or soybeans: First, find a place in your field where no one can see you. Drop your slacks and sit down. If you have to stand up right away, it’s not time to plant yet. But if you can sit, then plant your seeds.

In reality, the joke is pretty close to the truth. Cold fields that can make you stand up and soon as your cheeks hit the earth are terrible for germination. Now that reduced tillage is becoming more popular, chilly fields are more common. Also, residue in the cold makes fungal growth more likely. There isn’t a direct link between residue and bugs, but such residue does give the insects more exposure to the seedlings and seeds. Therefore, seed companies have traditionally put a coat of insecticide on their seeds to deter the likes of corn maggots and wireworms from having a snack on the farmer’s seed money.

The same goes for soybeans. The insects that love to have an early spring soybean feast are aphids and bean leaf beetles, among others. Almost half of soybeans are treated with fungicides and insecticides, according to data from Bayer CropScience.

Expensive seeds have made treated seeds even more appealing. Such an investment calls for protection from early pests.

Here’s the Catch

The insecticide used to treat corn or soybean seeds are neonicotinoids. Cruiser, or Thiamethoxam; imidacloprid, or Gaucho; and clothiandidin, or Poncho can fend off pests from the seeds and are almost completely safe for the environment – except for the bee environment.

This set of insecticides are deathly to honeybees who touch the stuff. Clothianidin is incredibly toxic to the honeybee, for instance, according to Greg Hunt and Christian Krupke of Purdue University. They are entomologists who studied how neonicotinoids affected honeybees. Recently, a ban on such insecticies was requested by eleven environmentally concerned groups in hopes of protecting the honeybee.

In addition to honeybee concerns, the economics seem to be against neonicotinoids. The EPA analysed and concluded that there is almost no financial benefit for treating soybeans with neonicotinoids.

The officials did admit that the insecticide did protect against pests who came on without warning in random areas. This is of particular concern in the South. However, this benefit doesn’t affect many, according to the report. According to their analysis, the largest benefit is $6 an acre. They concluded that usually such neonicotinoid treatments on soybeans are not financially helpful for a farm.

The Jury is Still Out

So does your seed need neonicotinoid treatments? According University of Illinois entomologist Mike Gray, it’s needed on corn seed.

Corn is at greater risk to stand reductions that can be caused by a variety of secondary soil insects,” Gray said.

There isn’t a way to rescue a plant from a white grub or wireworm infestation. Once a stand of corn has been attacked, all you can do is replant. Soybeans, however, are a different story. Most entomologists say that the EPA are correct. In December, there were 18 Midwestern entomologists who composed a letter to the EPA saying that neonicotinoid treatments needn’t and shouldn’t be so widespread.

Unless soybeans are at high risk by the only significant early-season pest bean leaf beetle, blanket insecticide seed treatments are not a good idea,” entomologist Ada Szczepaniec said.

This prophylactic use of neonicotinoid insecticides veers off the integrated pest management (IPM) system. An IPM approach should include many methods of managing pests that includes pesticides as one option based on economic sensibility.

Such use of pesticides could be called “insurance” pest management (if such users still wanted to call it IPM). In this way, farmers can buy pre-treated seeds or seeds that are insect-resistant or herbicide-tolerant to make sure that pest management isn’t a problem. However, this strategy may eventually lead to insecticide-resistant pests since the same treatment is used widely again and again, according to the 18 Midwestern entomologists.

However, some entomologists from the South disagree. Entomologist Scott Stewart of University of Tennesse, said that there is an increase of two bushels an acre due to treated soybeans seed in the MidSouth. This was a 10-year study of 170 trials. He also believes that such treatments will become even more necessary now that cover crops are becoming more popular, allowing for more spring-season pests.

Nonetheless, the EPA’s conclusion jive with a study conducted in 2005 and 2007 by land-grant university students in Michigan, Minnesota and Iowa. It compared these aphid management strategies for soybeans:

  1. Untreated

  2. Prophylactic insecticide applied at first bloom

  3. Thiamethoxam, or Cruise, seed treatment

  4. IPM management strategy including scouting, application of insecticide on leaves if a certain threshold of 250 aphids on a plant was reached. If there were less than 250 per plant, no insecticide was used.

In the end, the IPM strategy was the best.

Seed treatments provided little protection for soybean aphids,” Iowa State University entomologist Matt O’Neal said.  “They can protect yield, but when no pest is present, there is no benefit. It’s insurance, whether you need it or not.”


O’Neal did state, though, that aphids are just one kind of pest. Neonicotinoid treatments are meant for a broad spectrum of pests.

Iowan Farmer Jeff Anderson recounts the days before neonicotinoids and what it was like trying to grow soybeans, “Bean leaf beetles would eat the cotyledons right down to the ground,” he said. Now, the treatments erase those worries.

Seed manufacturers who use neonicotinoids disagree with the EPA as well. “In spite of what EPA concludes, they do have yield benefits,” Syngenta’s Caydee Savinelli said.

A study that Bayer, Valent, Syngenta, and Mitsui commissioned and AgInfomatics conducted with the help of 14 independent students showed that the use of neonicotinoids could increase yield by 2.8 percent.

Increased yield is not the only benefit. Officials from Syngenta said that thiamethoxam, or Cruiser, may make seedling stronger, grow faster and be healthier.

It’s also a fact that neonicotinoids don’t kill the helpful insects that are predators of pests like aphids. This is unlike broad-spectrum insecticides applied onto plants like pyrethroid and organophosphate which are deadly to good insects as well as pests.

Stop the Dusting

The one thing that may make neonicotinoid treatments history is what they do to honeybees. Honeybees already have enough adversaries with bad weather, mites, and disease. Their populations need to be protected.

Germany went ahead and levied laws against neonicotinoids once a large number were killed in 2008. The EU, in turn, banned the use of such treatments for two years.

Consequently, British farmers could feel the lack of such insecticides after a year. Flea beetles affected canola crops within one year of the suspension, Savinelli said.

Treated seed is not the problem,” she said. “It is when growers put talc in and use pneumatic planters rather than planters using finger pickups. The pneumatic planters and abrasive talc cause the neonicotinoid treatment to dust off.”

This dust can land on plants or hives nearby that honeybees frequent. Since corn seed is oddly shaped, dust from corn farming is more commonly a problem.

Bayer CropScience is selling a new product to help stop dust-off. This product is Fluency Agent. In testing, dust-off is reduced by 90 percent when compared to talc, and reduced by 60 percent when compared to graphite.

Fluency Agent is the best tool on the market for reducing dust,” Bayer CropScience’s Kerry Grossweiler said.

According to studies, Savinelli said that dust off actually is produced by the vacuum exhaust on a planter. Therefore, tests are being done in Canada, the U.S. and Europe on a physical deflector.

3 Things to Create Less Dust-off

This is what company officials and entomologists say to do to mitigate dust-off

  1. Observe the direction of the wind. If the wind is headed toward honeybees, dust-off will be more harmful for honeybees.

  2. Talk to beekeepers. “If growers know where they will be planting, communicate with neighbors who are beekeepers,” Grossweiler said. “If they know you are coming, they may be able to cover hives or move them.”

  3. Use seed that has been conditioned. If the seeds are uniform, there will be less dust-off, according to Savinelli.

Strips of Vegetation

According to ISU’s O’Neal, farmers could help bee populations be planting strips of native plants. This strip would make room for both the honeybees and the nepnicotinoid insecticidal seed.

In Iowa, a program called Science-Based Trials of Rowcrops Integrated with Prarie Strips (STRIPS) collaborated with farmers, scientists, Extension specialists and educators to create such vegetative strips next to farm or waterways.

Just using 10 percent of the farm for native plants, farmers will make a habitat for pollinating. This may even cut down on the loss of nitrogen in a field by 85 percent or erosion by 90 percent.

We’ve observed a remarkably diverse community of bees in corn and soybean fields in central Iowa,” O’Neal said. “Unfortunately, these two crops do not provide nectar and pollen throughout the time bees are active. With vegetative strips, it’s a 24/7 buffet for them throughout the summer. By limiting sediment and nitrogen loss and providing habitat for pollinators, our research suggests we can contribute to agriculture and conservation at the same time.”

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