Any malathion you have stored on your farm is still legal to apply in the short-term. However, be aware that grain that has been treated with malathion may not be acceptable to some processors. Before you apply malathion to a bin or commodity, check with your grain buyer to make sure your application meets their standards. The key to grain management is prevention. First, some questions you need to answer.
Some insects are primary pests, i.e., they attack undamaged grain and develop inside kernels.
Primary feeders are important because they not only cause direct damage, but also provide holes into kernels and fine material so that other insects, secondary pests, can infest the grain. Most other stored grain pests are secondary pests. Thus, the presence of weevils in your grain is of double concern. Answering these questions requires you to sample with a grain trier or a set of probe traps. At temperatures of 60 F or less, reproduction of grain insects drops off.