Do Neonicotinoid Seed Treatments Have Value Regionally in Soybeans?

Angus Catchot, Extension Entomologist
By Angus Catchot, Extension Entomologist, Jeff Gore, Research and Extension Entomologist, Don Cook, Research Entomologist and Fred Musser, Research Entomologist October 31, 2014 14:34

Do Neonicotinoid Seed Treatments Have Value Regionally in Soybeans?

There has been a tremendous amount of scrutiny put on the neonicotinoid class of chemistry in recent years because of the potential link to declines in bee numbers. Researchers are working feverishly across the nation and the globe to determine the exact causes of bee decline. No doubt pesticides can and likely play a role to some degree, but there are many factors that also influence bee health such as habitat loss, Varroa mites, and diseases.

Neonicotinoids are a class of chemistry that are highly efficacious against insect pests and very safe to mammals. This has led to increased use in many crops grown in the Midsouth region. Most products are systemic through the plant so they have a broad range of potential uses from seed treatments to foliar sprays.

Because of the temperate climate in the Midsouth region, pest pressure varies greatly by crop annually and outbreaks are frequent. In most years, the risk of significant yield losses from insect pests are extremely high. Farmers routinely have to rely on insecticides to manage insect pests in cotton, corn, soybeans, wheat, rice, and grain sorghum. In some situations, catastrophic yield losses can occur quickly in the absence of timely insecticide applications. Unlike many areas of the U.S., farmers in the Midsouth region can change crops and crop mixes from year to year to capitalize on favorable commodity prices. While this adaptability can reduce economic risk associated with individual crops, it can cause huge acreage fluctuations with a given commodity from year to year, further leading to potential unforeseen pest outbreaks since many pests can infest multiple crops grown throughout the region.

Recently the Environmental Protection Agency (EPA) released a document looking at the value of neonicotinoid seed treatments in soybeans in the United States http://www2.epa.gov/sites/production/files/2014-10/documents/benefits_of_neonicotinoid_seed_treatments_to_soybean_production_2.pdf. They basically concluded that seed treatments in soybeans provide “negligible overall benefits to soybean production in most situations” and “published data indicate that in most cases there is no difference in soybean yield when soybean seed was treated with neonicotinoids versus receiving any insect control treatment”. Many believe that this document is potentially setting the stage for an all-out ban on neonicotinoid seed treatments in soybeans in the near future. While the EPA does acknowledge there may be some slight regional differences, their assessment is based on an incomplete data set.

The incomplete data source problem is three fold: 1) The EPA never asked the people who generate data if we had pertinent data to include, 2) as academic entomologist it has never really been an accepted practice to publish “efficacy” type trial data in a peer reviewed format as other disciplines commonly do. This applies even if it is scientifically valid replicated trial data. We do use other outlets, such as newsletters and grower meetings, but unless it is peer reviewed it carries little weight with the scientific community. 3) What defines a region? The Midsouth is typically “lumped” in with the Southeast (Georgia, South Carolina, North Carolina, Virginia) with regard to numerous agricultural issues. For many issues this is appropriate, but for agricultural issues related to insect pests, there are important differences between the regions, and entomologists in both regions acknowledge this difference. It is very common to have different pest issues and recommended control strategies between these regions. We define the Midsouth as an area including MS, LA, AR, TN, and the bootheel of MO.

As it turns out, even before EPA released this report, the Midsouth entomologists were working on a meta-analysis of the value of neonicotinoid seed treatment usage in all crops in the region for publication in a peer reviewed journal. This is forthcoming, but it takes time to gather and compile hundreds of trials across states and years. In the meantime, we have compiled PRELIMINARY data on neonicotinoid seed treatment use in soybeans in MS. Because the soybean growers in our region believe in the advantages of these seed treatments and are wanting a response to the EPA document, we felt it was necessary to share our preliminary findings now. The summary below currently represents soybeans in MS, but we are working on the data for other crops throughout the Midsouth region.

We have been testing neonicotinoid seed treatments in soybean since 2005, and first commercial use was in 2007 with 2% adoption; it has since reached about 90% adoption in MS.

1

Across 73 replicated trials in MS conducted from 2005-2014, we are averaging a 2.5 bushel/acre yield benefit from the use of a neonicotinoid seed treatment in soybean. We only included trials with Gaucho (imidacloprid) and/or Cruiser (thiamethoxam). We did not consider any combinations with seed treatment nematicides to avoid confounding yield results. In all cases the untreated seed had a fungicide applied as did the insecticide treated seed.

2

 

We did not see a statistical difference between imidacloprid and thiamethoxam in regards to yield protection. Both products performed similarly.

3

Looking at individual trials, there was a 73% probability of a positive yield response and 60% probability of a return > 1 bushel. The average response of all trials greater >1 bushel was 3.98 bushels. There was one trial during 2012 that had response of 37.6 bushels. We did not include this data point in the 3.98 bushel average. The large yield response in this trial was due to a pea weevil outbreak from usage of Austrian winter peas as a cover crop. During 2014, similar results were observed in several AR counties when pea cover crops were used as well. The benefit from risk aversion from use of seed treatments cannot always be captured in an economic analysis but examples such as this illustrate the occasional value provided by preventative pest management strategies. Seed treatments provided complete protection in this example.

4

Net value added to MS soybean producers since initial adoption in 2007 has been $204,992,095. This is based on the adoption rate of seed treatments and 60% probability of a yield difference greater than 1 bushel per acre with an average response of 3.98 bushels.

5

You can see from our preliminary findings that not only do seed treatments have a value in our region, but that value is substantial. In some cases it has been difficult to document which specific pests contributed to these increases. We know that the above ground pests such as bean leaf beetles and threecornered alfalfa hoppers are controlled for about 3-4 weeks after planting, but we believe the bigger response is the soil insect complex that is difficult to sample and quantify. We routinely see better and more vigorous stand establishment where seed treatments are used. In recent years soybean yields in Mississippi have been less variable with record yields the last few years. While seed treatments may not be responsible for the record yields, we believe they play an important role in yield stabilization.

We clearly have established that there is a value to the producers in our region, but the issue is bigger than that. While the row crops we grow in MS do not require the use of pollination services, our farmers have expressed on numerous occasions their willingness to work with beekeepers to mitigate risks. In fact we recently enacted the Mississippi Honeybee Stewardship Program designed to bring awareness to potential issues between beekeepers and row crop farmers http://www.mdac.state.ms.us/departments/bpi/pdf/Bee%20Brochure.pdf. For the first time our farmers are having the conversation with beekeepers about pesticide usage and how to avoid problems by working together. However, we need to be very careful when considering banning the very products that are keeping our farmers profitable. The growing fear is that our farmers will begin to see the beekeepers as threat to their freedom to operate and will no longer allow them to maintain colonies on their farms. In light of the EPA document, we have already heard this chatter. This will not be good for anyone in the end.

The appropriate use of insecticidal seed treatments are important decisions and we all want to do the right thing for the agricultural industry, the environment, and society as whole but let’s make sure the decisions are based on facts and not driven by politics.

 

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Angus Catchot, Extension Entomologist
By Angus Catchot, Extension Entomologist, Jeff Gore, Research and Extension Entomologist, Don Cook, Research Entomologist and Fred Musser, Research Entomologist October 31, 2014 14:34
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