When populations are high, soil insecticides can protect developing pods and prevent losses of several hundred pounds of peanuts per acre. But, rootworms are not common in sandy, well drained fields, and applications of soil insecticides in those fields often do not pay. Mid-season pests like corn earworm and potato leafhopper are also fairly common problems in Virginia peanuts. In our experience, it has been very rare to find a field where corn earworms, even though they eat some peanut leaves, have caused yield reductions. Most insecticide treatments do not result in increased yields.
Potato leafhopper can be another story.
Last season, we had a field experiment where leafhoppers reduced yields by an average of 431 pounds per acre, compared to treatments that kept populations in check. However, we also see many cases where fields are treated for leafhoppers when only the leaf damage, 'hopper burn', is present but the hoppers themselves have migrated to some other location. Those treatments do not result in any yield advantage. These insect management decisions are not simple or easy to make. We have developed a lot of information over the years to help producers make them.