Sanet:

One of my colleagues pointed out to me that, in addition to the effect of the Bt corn pollen on wild butterflies like monarchs, this also has implications for the use of refugia in attempting to delay the development of resistance to Bt in corn crop pests.

The point of having refugia (plantings of corn which are not Bt-transformed or treated with Bt -- they can be treated with other insecticides, in which case they must be much larger, or they can be treated with no insecticide at all) is to have a supply of caterpillars of European corn borer and other corn lepidopteran pests (e.g. corn earworm and fall armyworm) that are not exposed to Bt and thus not under selection pressure for resistance. This susceptible population is supposed to swamp any rare genes for resistance to Bt. The assumption has been that these rare genes for resistance would be recessive. That assumption was called into question by the article in Science last week.

The assumption that these caterpillars would not be exposed to Bt in the refugia is called into question by this new article, pointing out that the Bt-transformation is expressed substantially in the pollen. This Bt pollen would be all over the plants in the refugia (which are supposed to be planted close to the Bt corn to ensure mating between the resistant and susceptible moths). During the stages when the caterpillars are feeding out on the plants (as opposed to tunneling within the stalk) they would be eating this pollen along with plant material. Thus, they would be exposed to variable doses of Bt (the very thing the high-dose strategy is supposed to avoid). Also, corn earworms feeding in the silk might be exposed to variable doses of Bt pollen stuck on the corn silk (and maybe in the pollen tubes growing down the silk?) So, another assumption on which the deployment strategy for Bt-corn was based may be wrong.

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