Comments by Dr. Dave Shetlar aka "The Bug Doctor" from Ohio State's Entomology Extension.

What does mild winter mean for insect and mite populations?

As an entomologist, I would think that news agencies would have more to deal with, but it’s also possible that folks are getting tired of “March Madness,” political shenanigans and foreign wars! In any case, I’ve been getting daily requests to predict what this mild winter will do with the insect and mite populations. I’ve gotten to that stage where I’m stating, “I’ll let you know in September what the mild winter did!”
Actually, there is a grain of truth in this statement. Some entomologists are sticking their heads out and declaring that it will be a horrible year for insect and mite problems, yet others are stating that there will probably be no real difference. I’m one of those that believe certain critters will do better, some will do worse, but most will do about the same.

Critters that do better will likely be the solitary bees and wasps that hide in sheltered sites to avoid really cold temperatures. They didn’t need much shelter this winter. Mosquitoes that overwinter as adults are already being spotted and when they emerge during warm nights, there are birds and mammals that can provide them with a blood meal! I suspect that some insects that overwinter as eggs, like the bagworm, may survive better this winter, especially in the northern part of its range. One the other hand, the parasites that attack bagworms will also do better, so surviving bagworms may actually have greater parasite pressure.

Critters that can be hurt by these mild temperatures are those that overwinter in stages and need food when it warms up. The Asian multicolored lady beetles can warm up and go outside, but their aphid food isn’t here yet. This activity can deplete the lady beetle’s fat stores and it may expire from the stress. Honey bees have been flying several times this winter, but if there are no pollen and nectar sources, they can also run out of food stores. Other predators, like ground beetles and spiders can have difficulty if they are warm enough to be active, but prey is scarce.
Though small, potato leafhoppers fly up from southern states to cause crop and tree problems.

Many of our pests are migratory. The black cutworm and potato leafhopper arrive in Ohio on the winds of storm fronts. If the adults of these insects arrive before our crops are in and up, the adults are likely to lay their eggs in alternate locations or they may also die off! Black cutworms appear to prefer laying their eggs in seedling corn, but they will go to turf if this food isn’t available. So, golf course superintendents may see earlier than normal cutworm damage this year and our corn crop may escape damage as the corn plants may be too large when the first generation of cutworms finish their development and look for new locations to lay eggs.

White grubs can do fine in mild winters, but they can also get caught by pupating early, and if the pupae are then subjected to rain-saturated soils, they can suffocate.

Bottom line, this is all speculation. We really have little data on most insects that would confirm whether mild winters are good, bad or neutral for insect and mite populations. I’ll let you know what happened next September!


This article originally ran in the PEST Newsletter, produced by Dr. Dave Shetlar and available for subscription via the Ohio Nursery Landscape Association.