Will a hard winter mean fewer pests this year? I’m not holding out much hope. It all depends whether you believe the path to redemption lies in ordered hygiene or dynamic balance. In favour of hygiene, the cold will have cleaned things up; a lot of aphids will have perished and leaves and roots harbouring disease will have been killed, thus breaking the disease-carrying bridge between seasons.
Unfortunately my experience of cold winters past is that any benefit will be short lived. Taking an ecological “balance” perspective, this is easily explained. Most pests that make a meal of our crops are also a meal for someone else: aphids are eaten by ladybirds, lacewing and hover fly larvae and parasitized by certain wasps, slugs are eaten by carabid beetles and toads and predated by nematodes. Red spider mites are controlled by the predatory mite phytoseiulus. Unfortunately these farmer friendly “beneficial” organisms will have also suffered in the cold; in fact they tend to be more affected by the cold than the pests (not only do many die, the survivors get dopey and less hungry).
Some pests always survive and, after a cold winter, there are fewer predators to keep them in check. As pests tend to get going sooner and breed faster, a cold winter might be expected to result in a higher population peak before the predators catch up. Hence cold winters may help the hygiene approach to pest management (as propounded by pesticide salesmen) but are not much help to those looking for balance.