How Weather Effects Yellowjackets

Yellowjackets Thrive in Droughts

Yellowjackets on picnic watermellon
Yellowjackets on picnic watermelon

Yellowjacket populations fluctuate dramatically from year to year. In the Lake Tahoe Basin area of California, we experienced very high yellowjacket populations between 1980 through 1984. Then the number of yellowjackets (and the number of nests we were treating) decreased dramatically. But in 1988, the populations rebounded to very high numbers. In 1989, we experienced a yellowjacket invasion so intense that the recreational sites: campgrounds, beaches etc.– were almost deserted in August and September because of yellowjackets.

Most of California is experiencing a severe drought this year. The weather conditions in California this summer, 2016 are very similar to the weather patterns we saw in the 1988-89 years in the Lake Tahoe area. And sales of Alpine Pest yellowjacket bait stations to California suppliers are running very high when compared to recent years. These factors indicate that this year could be a very large yellowjacket year for California. Oregon, while not as dry as California, was below average for moisture this year, and we saw yellowjacket populations rising last season, so we may be in for a bigger season this year in Central Oregon.

Yellowjackets, especially the ground nesting species, thrive in drought conditions. There are many reasons for this correlation including the fact that higher moisture levels decrease suitable areas for nests and rainy days inhibit a yellowjacket’s ability to hunt for food. In addition there is a nematode (round worm) parasite that attacks the queens in the spring that requires high humidity levels to survive.

Does the current drought cycle in the western states  mean that California, Oregon, Washington, Idaho and Montana are in for a big yellowjacket year? Not necessarily, but it’s certainly something to keep in mind.