Weevils - Ask Extension
We have weevils eating our raspberry plants and clematis. In the last few days, we have collected dozens. How can we eradicate them?
Knowledgebase
Weevils #875940
Asked July 04, 2024, 2:43 PM EDT
We have weevils eating our raspberry plants and clematis. In the last few days, we have collected dozens. How can we eradicate them?
Wayne County Michigan
Expert Response
Those appear to be two-banded Japanese weevils. Common critters on trees, shrubs, and brambles in backyard plots.
Depending on how much time you have and how big a plot you are maintaining, the two options are to pick them off by hand or apply a foliar insecticide.
To hand pick them, you carry around a cup of soapy water. Pick the weevil and drop it into the cup. Leave them to die in the cup for a day or so then dump them in the trash or somewhere else.
For chemical management, you have several options. Malathion, Sevin, Neem oil, and various pyrethroids all have some level of effect on different beetle species including weevils. The key is make sure you have adequate coverage so they get a good enough dose to be killed.
Depending on how much time you have and how big a plot you are maintaining, the two options are to pick them off by hand or apply a foliar insecticide.
To hand pick them, you carry around a cup of soapy water. Pick the weevil and drop it into the cup. Leave them to die in the cup for a day or so then dump them in the trash or somewhere else.
For chemical management, you have several options. Malathion, Sevin, Neem oil, and various pyrethroids all have some level of effect on different beetle species including weevils. The key is make sure you have adequate coverage so they get a good enough dose to be killed.
Thank you for the prompt response. My understanding is you need to kill the larva in the ground in order to truly eradicate. Is this accurate and if so how do I go about doing that?
The challenge with insects like these is that they tend to have a wide host range. They are feeding on more than just your landscaped plants. Yes, you can help manage them in the spring using a soil drench of imidacloprid under your plants, but they may be emerging from other areas as well. So, that will not eradicate them. It will only help manage them. I would recommend a multi-tiered approach if they are getting bad enough to warrant a strong management strategy.
First would be to do a soil drench as mentioned with imidacloprid in the spring as the plants start growing. Then as the adults start showing up, a foliar spray of insecticide that works on weevils. And as a third option, as you continue to see adults through the summer, you can treat again if you wish or you can pick them off and kill them as you see them. A soap solution in a bottle next to you every time you are out there to spray on the adults you see may be of help, but is not as effective on robust beetles as it is on soft insects like aphids.
First would be to do a soil drench as mentioned with imidacloprid in the spring as the plants start growing. Then as the adults start showing up, a foliar spray of insecticide that works on weevils. And as a third option, as you continue to see adults through the summer, you can treat again if you wish or you can pick them off and kill them as you see them. A soap solution in a bottle next to you every time you are out there to spray on the adults you see may be of help, but is not as effective on robust beetles as it is on soft insects like aphids.
