My aphids are not dying after I treat them!
Editor’s note: This article is from the archives of the MSU Crop Advisory Team Alerts. Check the label of any pesticide referenced to ensure your use is included.
Over the past couple of weeks we have been hearing reports from greenhouse growers that have had aphid outbreaks and that certain insecticides are not working as well as they have in the past. The word RESISTANCE then is mentioned as the reason for the lack of control . Before implicating resistance to a certain insecticide think about the following items.
1. Did you apply the correct insecticide? Is it labelled for aphids?
2. Did you apply the correct rate? Check your math twice to be sure you put enough product in the tank to treat the area you intend to.
3. Are you using a high pressure sprayer? They work considerably better than a fogger for aphids. Aphids tend to be on the undersides of the foliage. Get good coverage.
4. Rotate your Mode of Action of the insecticides you choose to reduce the risk for resistance.
5. Aphids reproduce much faster in temperatures over 75 degrees F. than in a cooler greenhouse. We have seen 85 degrees F. in many greenhouses now. If your interval between aphid sprays is 5-7 days your going to have newly hatched aphids coming out between your spray intervals. Tighten up your intervals.
6. If you still suspect resistance spray half a bench or range where the aphids are with the product you suspect resistance with and spray the other half wit another aphid insecticide. Then observe the mortality differences.
7. Best aphid materials as sprays at this time of the crop cycle are: Aria, Endeavor, Marathon 2, and Orthene.