Wheat Crop Killer May Have Met Its Match The wheat stem sawfly is a tiny insect that does devastating damage to wheat plants. Like many insects that kill plants, it is not the adult bug but its larvae that do the damage. The sawfly lays eggs in the stem and its hatchlings devour the plant from the inside as they grow. It is estimate that the yearly loss in wheat across the northern plains states is upwards of $300 million. Scientists developing a new insecticide, called Thimet 20-G, may have found the answer. It works well, but has a glitch: this insecticide can be tricky to apply to crops. In order for Thimet to work, it has to be inside the plant stem at the right time, but be gone from the mature wheat by the time it is harvested. So the chemical must be applied within about an 85-day window. In addition, the new insecticide is harmful to mammals so must be handled with care and buried in the ground about an inch deep so that birds won’t encounter it. Thimet 20-G is what’s termed a systemic insecticide, meaning it needs to be applied to the roots of the plant so it can do its work in the whole system of the plant. By the time the wheat has reached maturity, all traces of the chemical – and the sawfly – are gone.