No Yellowjackets this summer? - Ask Extension
It's weird: I've lived here in Lane County south of Veneta for 34 years, on 16 acres of mixed white oak + doug-fir forest and grassy pastures, with a ...
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No Yellowjackets this summer? #879026
Asked July 27, 2024, 3:43 PM EDT
It's weird: I've lived here in Lane County south of Veneta for 34 years, on 16 acres of mixed white oak + doug-fir forest and grassy pastures, with a lot of wild blackberries scattered throughout. Of course I mow most of those acres to minimize wildfire risk, so typically stumble over 10 or 20 Yellowjacket nests every year. But this summer, it's been great -- NO NESTS AT ALL! Also, as you would expect, the number of YJs that wander inside the house is an order of magnitude lower -- I've only seen a couple so far this summer.
So my question: have you heard this story (Yellowjackets MIA) from others in Benton or Lane counties? If so, got any ideas why it's happening?
Lane County Oregon
Expert Response
Hi Lloyd,
It's a little early to count your chickens yet. We typically don't notice yellowjackets until their nests reach a certain size, which typically occurs later into August (depending on the species). I am starting to observe an uptick in numbers in my traps and expect we still a few weeks away from them spilling over into our picnics etc.
But there is certainly some evidence of years where yellowjacket pressure is less severe than others. An older study from the 1980s observed that summers with high summer yellowjacket pressure tend to increase with hot and dry springs. What is a hot and dry spring? They defined it as any year when May-July temperatures are 1.4 - 9.3F above average and precipitation is 0.6 to 2.38 inches below average.
Akre, R.D. and Reed, H.C., 1981. Population cycles of yellowjackets (Hymenoptera: Vespinae) in the Pacific Northwest. Environmental entomology, 10(3), pp.267-274.
In Corvallis we had a slight more precipitation compared to the historical average, but also higher than average temperatures. So, it remains unclear what the yellowjacket situation will be come August. Fingers crossed.
It's a little early to count your chickens yet. We typically don't notice yellowjackets until their nests reach a certain size, which typically occurs later into August (depending on the species). I am starting to observe an uptick in numbers in my traps and expect we still a few weeks away from them spilling over into our picnics etc.
But there is certainly some evidence of years where yellowjacket pressure is less severe than others. An older study from the 1980s observed that summers with high summer yellowjacket pressure tend to increase with hot and dry springs. What is a hot and dry spring? They defined it as any year when May-July temperatures are 1.4 - 9.3F above average and precipitation is 0.6 to 2.38 inches below average.
Akre, R.D. and Reed, H.C., 1981. Population cycles of yellowjackets (Hymenoptera: Vespinae) in the Pacific Northwest. Environmental entomology, 10(3), pp.267-274.
In Corvallis we had a slight more precipitation compared to the historical average, but also higher than average temperatures. So, it remains unclear what the yellowjacket situation will be come August. Fingers crossed.
