In August, we noticed hundreds of bees and flies swarming in and under my...
In August, we noticed hundreds of bees and flies swarming in and under my son's corkscrew willow tree. We finally figured out that the flying insects and sticky mess in and around the tree were due to a massive infestation of black aphids (about 1/16"-1/12" long, some with red spots at the tail end). We tried knocking them out of the tree with a hard spray from the garden hose, based on some silly suggestion that they wouldn't be able to climb back up into the tree. There were as many or more in the tree the next morning. We've tried local treatment with premixed insecticidal soap, and have tried dousing the entire tree with insecticidal soap concentrate by hose-end sprayer and hand pump multiple times. The affect on the bugs seems negligible at best. We've even tried spraying the ground around the tree. In some ways the problem has gotten worse. The aphids are either dispersing or the problem is due to those that have been knocked from the tree, but they are crawling up every stationary object in the yard. They don't appear to be climbing the other trees and plants in the yard. Instead, they cover the wall of there garage, under the tree, the stone benches out away from the tree, the tables and chairs on the patio, the outer surface of yard waste bags, even people, if you stand still too long. And, as fast as we kill them, they reappear. We don't, however, see lines of them crawling on the ground on their way to the surfaces they end up on. So, where are the reinforcements coming from. I should add that killing them is easy but a messy proposition because, if you're not careful, their blood stains everything dark purple. We've read that the next line of attack is imidacropid (I think that's spelled right), but we're leery of applying it because of all the environmental and exposure warnings, the fact that this is a small yard with close by neighbors, and a general aversion to the products. Do you have any suggestions on how to address this infestation? Thanks, Jeff Toth
Neem oil and insecticidal soaps generally work on aphids. Was the soap solution you tried containing pyrethrins? Pyrethrins have a lower environmental impact then imidacloprid, and are effective against aphids. An imidacloprid, product, which is a systemic insecticide would be the next step to control the infestation. If you use this product, follow the labels and wear the proper protective equipment. Use the dosage on the label for woody ornamentals. This product will affect pollinators, however it is not a flowering period for the tree. Following the label instructions correctly will minimize the impact on pollinators. You can contact a pesticide applicator if you do not feel comfortable applying this
I appreciate the information. There are a few things we don't understand, however.
Why are the aphids expanding their territory and moving from the willow tree to every stationary, vertical or raised horizontal surface like the garage wall, benches, patio furniture, porch door, even people (if they stand still too long)?
And, we can't figure out where they're coming from. They just appear on all these surfaces but there's no trail of bugs on the ground. Are they coming up from under ground or floating on the air?
How do you deal with them away from the tree?
Jeff and Janice Toth
Aphids can have multiple life cycles over a season, especially when it is warm weather. Multiple treatments may be needed to control new aphids hatching.
For additional questions, I would contact David Shetlar, he is an OSU entomologist who may be better able to answer these questions, and confirm that they are aphids. His contact is: