It is not uncommon for a farmer to save some of their wheat or rye crop in a grain wagon for seed to plant their next crop in the fall. Once their wagon is full, it will be shoved into a barn or shed for the rest of the summer until it is needed in the fall. Occasionally, when they return to retrieve their seed, they discover that the wheat or rye has been infested by Indianmeal moth (Plodia interpunctella) and possibly other stored grain pests as well. The activity of these grain infesting insects results in reduced germination potential and/or seedling survivorship requiring an increased seeding rate to compensate for the damaged seed.
Indianmeal moth is the most likely grain infesting insect to discover the stored seed in a grain wagon for a short period of time. How quickly it will discover the grain varies on where the nearest source of the moths is located and weather conditions amenable to moth flights.
There are several products that can be used to protect the seed grain until it is needed for planting. Since Indianmeal moth is of greatest concern, one can target both the caterpillar and the moth. A grain surface “cap out” treatment can be employed to the wagon load of grain because the main route of entry that Indianmeal moth uses is through the open top of the wagon. A “cap out” treatment is to apply the insecticide to the exposed surface of the grain and mixed into grain 4 inches deep. Indianmeal moth caterpillars can be controlled by products containing the active ingredient Bacillus thuringensis abbreviated Bt (e.g., Biobit HP, Dipel DF and Javelin). Other products labeled for Indianmeal moth caterpillars which may also deter other grain infesting insects contain pyrethrin (Pyronyl), Spinosad (Sensat), and s-methoprene (Diacon-D IGR).
If one places staves over the open wagon to be able to cover it with a tarp, one could hang a no-pest strip that releases the insecticide dichlorvos (2,2-dichlorovinyl dimethyl phosphate) (e.g., Nuvan ProStrips, Hot Shot No-Pest Strip) into the air under the trap. The trap must be tied down to trap the insecticide over the grain. The active ingredient Dichlorvos is excellent for managing flying insects including Indianmeal moth adults.
For insects that might crawl up the outside of the wagon and wheels, several products could be employed similarly as they would be used to treat the outside of a grain bin. These products include deltamethrin (Centynal), pyrethrin (Pyronyl), and cyfluthrin (Tempo SC).
Before using any insecticide be sure to read the product’s entire label and follow the instructions for appropriate dosages.