Instead of spraying crops, sometimes seeds are coated with pesticides, usually before the seed is even distributed to farmers. When the seed is planted the plant begins taking up the compound and expressing in throughout it’s tissues (in leaves, pollen and nectar), though much of the active ingredient is actually lost into the soil and finds it’s way into waterways (Goulson 2013). One worry is that then non-target insects using the crop, such as pollinators, may then be exposed the pesticides, with potential harmful effects. So the question is- does this type of seed treatment actually improve crop yields?
For soybeans, the answer is no, according to an EPA report released today. The report assessed grower pesticide use surveys throughout the US between 2009-13, comparing neonicotinoid treated soy (three different active ingredients: imidacloprid, thiamethoxam, and clothianidin) to non-treated soy. They found that the net economic gain of neonic seed treatments was $0 per acre. Additionally, treated seeds cost slightly more than untreated seeds, potentially leading to a net loss.
Given the potential harms of the pesticide to beneficial insects, and the lack of economic benefit, seed pesticide treatments seem like they are not the most effective way to control pest insects and crop damage. Studies of other crops that use neonic coated seeds, such as sunflower, are needed to determine if this method of pest control is something that should be abandoned for alternate methods. Right now it is challenging for growers to obtain untreated seed, because, as mentioned, it is often done by companies distributing the seeds. Altering the seed companies practices to reflect this data will likely benefit them, growers and the non-target insects that might be harmed by treated seeds.