As a much beloved and often quoted character from the hit series “Game of Thrones” once said: “Brace Yourselves, recipe Winter is coming”. Considering the winter we’ve had in New Jersey this year, troche he was certainly right. As a matter of fact, it seems that winter might never leave us, as some residents of New Jersey awoke to a covering of snow and/or ice this morning, April 16.
Due to the harshness of the winter, we’ve been peppered with questions about the climate’s effect on pest populations. The most common being “Since winter was so cold, does that mean there won’t be many insects this summer?”
In a word? Nope. Sorry gang, things aren’t that simple. The weather and insect populations have a complex interrelationship that can vary widely depending on the type of insect in question. There’s also the question of the Predator/Prey relationship, if a predatory insect has a hard winter the insects they prey upon will have a higher population. In a way, a cold winter may actually give rise to higher insect populations. Let’s discuss in a bit more detail, shall we?
First things first, let’s deal with our native insects like ants, termites, wasps and mosquitoes etc. These types of insects, which compose our most bothersome outdoor (and sometimes indoor) pests. Since these insects predate humans on this continent they have adapted to this environment and its climate. As a matter of fact, these insects have survived much colder periods, namely The Year Without a Summer (1816) and the period of time known as The Little Ice Age (approx. 1500-1800). Insects native to the North East region of the US have dealt with similar and colder temperatures for millions of years, a little glitch of cold won’t have much of an impact at all. Conversely, these native hymenoptera (ants and wasps) tend to be the predatory insects I mentioned above. Although a brutal winter may cull their population somewhat, as a species they will survive.
Next, and maybe a bit more importantly, would be our resident, commensal insects. The word “commensal” is a Latin derivative meaning “to share our table”. So these pests that quite literally share our table would be things like German Roaches, Bed Bugs, House Mice and the Norway Rat. As the names imply, these pests are not from North America but have been imported from Europe along with the first settlers. Some rodent biologists hold fast to the idea that the first Norway Rats arrived on the Mayflower. The nature of these pests is inextricably tied to the presence of humans and access to our resources. In other words, as long as humans can withstand the climate, then these pests will as well. The majority of commensal pests live indoors in close association with humans and as indoor pests they will have limited or no exposure to the severe weather we’ve endured. To paraphrase the great comedian George Carlin: “No matter what temperature it is in the room, it’s always “Room Temperature””.
The last grouping of insects would be unique in that they are imported pests, but not necessarily commensal pests. Recent arrivals like the Asian Lady Beetle, Asian Longhorned Beetle and the Brown Marmorated Stinkbug have been arriving in North America since the (rather modern) advent of high speed travel and have arrived here within the last few decades. Winter weather’s impact on these creatures is truly hard to discern. For the most part they originate from a comparable climate or ecology but with enough differences to have a significant advantage over our native breeds or varieties. There have already been anecdotal report of the winter killing off Stinkbug populations; one researcher reports losing 80% of his stored research specimens over the winter. On the one hand, these new invaders may have been exposed to conditions they are not adapted to survive, on the other, they may have faced these, or harsher conditions, in their native ecosystem. We would have to look at these insects on a case by case basis.
Understanding the weather or climate’s effects on a group of organisms is a truly difficult task, almost impossible to be gauged at the time of occurrence. Conversely, most population changes due to climate can be identified exclusively through the fossil record. But that would be for insects in nature. Unfortunately for us, the creepy crawlies that reside underfoot will stay right where they are, no matter the weather…