Cold temperatures and pest populations
The cold winter thus far has prompted many folks to ask what the influence of these temperatures might be on insect and slug populations. It certainly is the case that harder winters will knock back the populations of some pest species--bean leaf beetle, cereal leaf beetle, and slugs are three that jump to mind; it would be expected that populations of these pest species to be lower than usual come spring. (For slugs, their survival is also influenced by the amount of snow on the ground, higher amounts of snow insulate against colder temperatures.)
But, as for most issues with insects, it is difficult to generalize and the influence of cold winter temperatures on the majority of crop pests we face is not very predictable. For example, many insect pests that we face (e.g., potato leaf hopper, black cutworm, armyworms) are migratory and come to Pennsylvania from southern states; therefore, our local weather will not influence their arrival much—their local overwintering conditions matter more.
For pest species that have arrived more recently, there is a relatively poor understanding of the influence of winter temperatures on their populations. Brown marmorated stink bug, for example, seems to have higher mortality the colder it gets, but their overwintering site likely influences their survival. If stink bugs are able to find just the right overwintering spot that keeps them cold but not too cold they will probably make it through the winter. For an even newer pest like kudzu bug, which is on the verge of being in Pennsylvania, everyone will find out together how well they survive the cold temperatures.
When spring arrives, to understand local pest populations and be certain of what is in your fields, growers will need to rely on regular bouts of scouting—get out in the field and see what is active! The best approach will be to watch fields closely, talk with others to learn what they are seeing, and stay tuned here for reports of pest activity.