Should We Use Clothianidin?

If you google “clothianidin” you’ll find that more than half of the results (even on the first page) are stories about how the pesticide kills bees and the EPA is (or was) covering it up. You might immediately conclude that it’s inconceivable that we haven’t banned it already.

But deciding whether to ban something requires value judgements that hopefully balance rights, risks and benefits (and hopefully include non-human considerations). This should be obvious: a lot of things kill bees and we haven’t banned all of them, even though bees are very useful to us as well as having some right to exist on their own. So the decision to ban clothianidin can’t be based merely on the fact that it harms bees, but needs to consider how it’s used and whether the benefits outweigh the costs.

In my previous clothianidin post, the thrust of the piece is saying that we need some kind of pesticide and since clothianidin is better than alternatives, we should use that. But if the pests clothianidin might control are easily controlled by other less harmful methods (or aren’t even normally a problem), then the argument falls apart: the risks to bees are basically not worth it under any circumstances. So that’s what I want to figure out. Do we really need it and what is the cost to bees? Is that trade-off worth it?

Questions

This topic will span multiple posts as I discover more research or think of new questions. To start, though, what are the questions we need to answer? Note that I’m primarily considering the use of clothianidin as a seed-coating on maize (corn), though it is used with other crops as well. I’m also assuming that maintaining high yields is a constraint — that is, I’m not considering the option that we could just go organic and everything would be fine. I’m dubious that current organic agriculture could actually grow enough corn to meet demand (without using a lot more land). Arguably if we stopped feeding so many animals, we wouldn’t need so much corn, but I see no way to make that happen any time soon. Thus, we “need” high corn yields because other societal choices (i.e. to feed animals and to make bio-fuels) have constrained our options. This is the context under which I’m considering these questions.

On to the questions!

Pests & Yields

  • What pests are seed-coatings of clothianidin protecting crops from? What kinds of damage do these pests do?
  • How common are these pests? In what regions? Is the pest pressure high or low?
  • Does clothianidin seed-coating improve yields and under what circumstances? Surprising (to me), grain yield is not the only consideration (but see below).
  • Does clothianidin seed-coating work better than alternate chemical insecticides? Have pests in many regions developed resistance to the alternatives and to what extent?
  • Are there workable and less dangerous alternate methods of control? This could mean alternate chemical pesticides or biological pesticides such as fungi, nematodes or wasps. It could also mean something as simple as rotation to different crops.

Unintended Effects

  • What is the damage to bees? What avenues of damage are there from clothianidin to bees? Can we mitigate them (e.g. contain pesticide-contaminated dust during planting)?
  • What kinds of harm do alternatives to clothianidin do to bees? Are they in general more or less harmful?
  • Similarly, how does clothianidin affect organisms other than bees? What risks are there from the alternatives to clothianidin?

Choices on the Farm

  • How routinely is clothianidin seed-coating currently used? Is it used more often than alternate methods of control (e.g. soil application of a pyrethroid pesticide) before it was available?
  • Does making the pesticide cheaply available (by only marginally more expensive seed coatings) increase overall use of pesticides because there’s less apparent cost to the farmer? Is it easier to unnecessarily apply a pesticide if the farmer doesn’t have to apply it himself?
  • How common are clothianidin seed-coatings? What percentage of seed corn gets routinely coated? Can farmers easily obtained uncoated seed?

There are probably more that I’ll think of later as I learn more. Surely those are enough for now! For this post, I’m going to start on some of these questions, but I’m under no illusions that I can answer any of them right now. For one, it’s pretty clear the research needed just doesn’t exist yet.

Pests and Damage

Question: What pests are clothianidin seed-coatings good for? What damage do these pests do?

The following is a table of major maize pests that clothianidin may control, largely taken from a couple references12 and the linked pages. I really recommend reading some of the links because most are from university-affiliated agricultural extensions and give a good idea at just how complex agriculture is and what we ask farmers to do. Plus there are pictures of bugs!

Pest How it affects maize
Corn Rootworm (Diabrotica spp.) Larvae eat the roots, possibly causing plants to lodge. Adults prefer to feed on the reproductive tissues in adult corn: silk, pollen and kernels. The corn rootworm is the most economically relevant maize pest that clothianidin is used for. There’s even a scale for judging the degree of root damage.
Seed corn maggot (Hylemya platura) Larvae bore into seeds and eat them, most commonly a problem in wet, cold conditions that delay germination.
Wireworm (Melanotus spp.) Larvae eat seeds and seedlings.
Black cutworm (Agrotis ipsilon) Larvae eat stems of seedlings, cutting them off.
White grub (Popillia japonica) Larvae eat seedlings.
Corn flea beetle (Chaetocnema spp.) Beetles feed on foliage and transmit Stewart’s wilt, a bacterial disease.
Chinch bug (Blissus leucopterus) Feed on foliage, weakens plant.
Corn leaf aphid (Rhopalosiphum madi) Suck sap from plants, doesn’t generally cause economic damage.

Improving Yield

Question: Does clothianidin seed-coating improve yields?

Maize is primarily a feed and biofuel crop. It’s a “commodity” crop where generally the goal is high yields, reliably. So I had thought the question here was to find comparison studies in different regions of the country (or world) where clothianidin is compared to alternate methods and whether it improves yields. I have found some studies on this (though not as many as I’d like) but I also found out that yield isn’t the only consideration.

A study from the manufacturer, Bayer, definitely claim that yields are improved and pest damage reduced when using clothianidin as a seed-coating, as compared to their choices of controls (Andersch 20032). Under corn root worm pressure, they claim more than 60% increased yield than no treatment for corn rootworm and significantly more than most other pesticides they compared against (e.g. tefluthrin, a pyrethroid). However, their trials that don’t involve corn rootworm pressure (14 locations across the corn belt) seem to not show 60% gains over untreated seeds and closer to 20% (Figure 18 in Andersch 20032) suggesting pest pressure isn’t that high in many places. Further, its ability to prevent root damage was fairly similar to other chemical insecticides.

What about other research? There’s not nearly as much as it as I expected and the best is fairly regionally specific. But to get my head around it, I want to list out each relevant result and basically what it means.

Yield in New York

A trio of papers by W. J. Cox et. al.345, were examining corn forage yield and quality in test plots in New York. The results are basically mixed and clothianidin seed coatings weren’t clearly helpful.

Corn Forage Yield in Rotation with Soybean

In “Clothianidin Seed Treatments Inconsistently Affect Corn Forage Yield When following Soybean”3, the authors are attempting to see if clothianidin improves corn forage yield. Being nearly ignorant of the topic, I learn that this is different than just yield (which I thought of in terms of kernels of corn produced). When growing corn for forage the leaves and other parts of the plant matter, not just the number and quality of kernels. Corn forage can mean feeding cows straight on the corn plants or fermenting it into silage. Various measures are used to judge the quality of forage including moisture, total dry matter, and others related to dairy production. There’s even science that lets farmers calculate estimated milk yield based on the quality of forage6 The corn is often grown more densely than it would be for grain. It being the internet age, you can get a quick basic summary of corn for forage and silage online from many university agriculture extensions, such as this factsheet from Ohio State and this one from University of Missouri7.

Cox et. al. note that maize is often subject to cold, wet springs in the northeastern US which delays germination and puts the crop more at risk for seed corn maggot and other pests. These pests could affect forage yield. The experiment, repeated over two years, was basically a grid of two corn hybrids either treated or not (the hybrids themselves had a Bt trait) grown in fields the year after soybeans. The authors collected plant matter or counted plants at different stages of growth and reported dry matter and other important values. The results, however, are inconclusive as to whether the clothianidin helped. Emergence was improved the year that conditions were poor (one year in the experiment had that cold, wet spring and the other didn’t) but no real significant effect on dry matter by silking stage when both years are included. Corn forage quality (the part the dairy people would care about) was not improved.

I don’t understand the statistics well enough to assess the correctness8, but they do seem to have considered a lot of variables and the results just look mixed. I do have one concern: they did not measure or otherwise determine how much pest pressure there was during the experiment. Since soybeans were previously grown on the field, it’s possible pest pressure was low enough that a pesticide wouldn’t be expected to help much. That said, if that’s the case, then it’s a good reason for seeds to not be routinely coated with a pesticide. However, the authors note that in 2006 apparently 35% of the corn seed sold by Pioneer in New York (with 40% market share) was coated with clothianidin. This study suggests it might generally be unnecessary.9

Corn Growth in Rotation with Soybean

In “The Effect of Clothianidin Seed Treatments on Corn Growth following Soybean”4, the authors are analyzing the same experiment as the above from a different angle. They are trying to determine if the seed coating negatively affects growth under low insect pressure, but possibly under poor (wet, cold) conditions. Previous research suggested this might be the case. To cut to the chase, they found no negative effects but only marginal improvements in any measurements and do not recommend routine clothianidin seed coating.

Corn Forage in Continuous Corn

In “Seed-Applied Insecticides Inconsistently Affect Corn Forage in Continuous Corn”5, they test corn forage yield under severe corn rootworm pressure. Fun fact: if you plant a mixture of corn and pumpkin (Cucurbita pepo L) it will attract corn rootworm beetles! Thus, the experiment involved planting the corn-pumpkin mixture one year to use that plot the next year, now full of rootworm larvae, to test effectiveness of the insecticides. The experiment was otherwise pretty similar to the others: plant a grid of two hybrids treated or not with different pesticides, then measure various things at different stages of growth. The results were, again, mixed. While the insecticide treatments (including clothianidin) seemed to decrease root damage, they didn’t explain variations in dry matter yield. Basically none of the differences between experimental plots were terribly significant and clothianidin is not clearly an improvement. The authors do note that wireworm and seed corn maggot were likely not present in sufficient numbers to greatly affect plant density so the only pest of interest was the rootworm.

A Couple More Studies, Please?

I truly haven’t found that many studies look specifically at yield: lots showing various pesticides affect pests, but not what the yield effects are. One I haven’t read10 yet, again suggests inconsistent yield results, but in the absence of pests. Another11 seems to tantalizingly have some interesting results12.

So I don’t really know much yet about this question! The answer so far seems to be “it depends and maybe only under severe pest pressure”. If you read some of those pest pages from university agricultural extension programs (or google about the pests), you find advice on how to measure pest pressure to decide whether to use controls for particular pests.

Next Up?

I don’t promise to post on this in any particular schedule. There’s a paucity of data on some questions so I may not get to some of them at all. There is a body of research of the effects of neonicotinoids on bee species (which so far is a bit less worrisome than the activists would claim, though still pretty worrying) so there will be some posts on that. I haven’t looked much at the choices available to farmers or whether ease of use affects popularity. Regional data on pest pressure seems to be scattered and somewhat unavailable but I should try to collect some. Considering the social pressure to “do something” about the bees, this is a topic that clearly needs more investigation.


  1. Jeschke, P., Nauen, R., Schindler, M., & Elbert, A. (2011). Overview of the Status and Global Strategy for Neonicotinoids. Journal of Agricultural and Food Chemistry, 59(7), 2897–2908. doi:10.1021/jf101303g. PubMed.

  2. Andersch, W., & Schwarz, M. (2003). Clothianidin seed treatment (Poncho®) – the new technology for control of corn rootworms and secondary pests in US-corn production. Pflanzenschutz-Nachrichten Bayer, 56, 147–172. PDF. 2 3

  3. Cox, W. J., Cherney, J. H., & Shields, E. (2007). Clothianidin Seed Treatments Inconsistently Affect Corn Forage Yield When following Soybean. Agronomy Journal, 99, 543–548. doi:10.2134/agronj2006.0170 Abstract, PDF 2

  4. Cox, W. J., Shields, E., & Cherney, J. H. (2007). The Effect of Clothianidin Seed Treatments on Corn Growth following Soybean. Crop Science, 47, 2482–2485. doi:10.2135/cropsci2006.12.0810 Abstract, PDF. 2

  5. Cox, W. J., Shields, E., Cherney, J. H., & Cherney, J. R. (2007). Seed-Applied Insecticides Inconsistently Affect Corn Forage in Continuous Corn. Journal of Agronomy, 99, 1640–1644. doi:10.2134/agronj2007.0104 Abstract, PDF 2

  6. Can you imagine how mind-blown a farmer from the 1500s would be if you told him that you could weigh some stuff and measure some other things and tell him about how much milk his cows would produce? There’s even a spreadsheet freely available (warning: slow loading Excel).

  7. After looking into this topic, it’s easy to see why production of beef and dairy are two of the largest greenhouse gas sources: there’s a lot of energy going into growing animal feed even when the cows are just eating corn plants straight out of the field.

  8. I’m hoping to improve in this area. How hard could statistics really be?

  9. Apologies for the possibly excessively long summary (“get to the results!”) but there’s lots of interesting things you need to know … and I left out a lot! Go read those papers!

  10. Wilde, G., Roozeboom, K., Ahmad, A., Claassen, M., Gordon, B., Heer, W., Maddux, L., et al. (2012). Seed Treatment Effects on Early-Season Pests of Corn and on Corn Growth and Yield in the Absence of Insect Pests. Journal of Agricultural and Urban Entomology, Journal of Agricultural and Urban Entomology, 24(4), 177–193. doi:doi: 10.3954/1523-5475-24.4.177 Abstract

  11. Maa B L, Melochea F,and Weia L. (2009). Agronomic assessment of Bt trait and seed or soil-applied insecticides on the control of corn rootworm and yield. Field Crops Research, 111(3), 189-196. doi:10.1016/j.fcr.2008.12.006 Abstract.

  12. At some point, I will be a bit less shy about contacting authors. I suspect there’s a lot of information, not just non-open journal articles but databases and search engines I don’t know about, that’s just not easily available to a non-expert.

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