Asiatic Garden Beetle control - Ask Extension
Hello. We have struggled with Asiatic garden beetles starting around this time of year for the last several years. They particularly love our cherry t...
Knowledgebase
Asiatic Garden Beetle control #872862
Asked June 12, 2024, 6:54 PM EDT
Hello. We have struggled with Asiatic garden beetles starting around this time of year for the last several years. They particularly love our cherry trees and viburnum. I’m wondering what the pest control strategies are these days. I covered the cherry last year with a net, but it’s getting a little too big for that. We strongly prefer organic methods. I am considering Spinosad and pyrethrin. I have also heard that using Nematodes might help in the long run as well. Any advice would be greatly appreciated. Thank you!
Washtenaw County Michigan
Expert Response
Asiatic Garden Beetle (Maladera castanea) can be damaging to plants and I understand your concern. It is not likely to be effective to target the immature (grub) stage with nematodes. Although the grubs are susceptible to some species of entomopathogenic nematodes, controlling the grubs in your yard may not have a big impact on the numbers of adult beetles that you see on your plants. The adults will fly long distances to reach a preferred food source. Insecticides with the active ingredient spinosad(s) are also not known to be an effective management tool for this insect.
If it is not practical to net your plants, hand picking the adult beetles can be a good option. They can also be knocked off into a bucket of soapy water with a stick or brush.
Products with the active ingredient pyrethrins would likely have the ability to kill the beetles on contact, but they would also kill many beneficial insects, so please keep that in mind. Products with the active ingredient Bacillus thuringiensis subsp. galleriae (strain SDS-502), can be used to protect plants from beetles with less risk of harm to beneficial insects. This active ingredient must be consumed by insects in order for them to receive a lethal dose, and it only affects insects in the order Coleoptera (beetles). Sprays may have to be applied frequently in order to protect plants from injury. Extreme caution should be taken if insecticides are used on or near flowering plants, to prevent harm to pollinators. Remove blossoms before applying pesticides to flowering plants and apply the product in the evening when pollinators are less active. The product label will contain additional instruction for its use that will ensure that you are using it in compliance with state law and in a manner that will ensure its effectiveness, your safety, and the safety of others.
If it is not practical to net your plants, hand picking the adult beetles can be a good option. They can also be knocked off into a bucket of soapy water with a stick or brush.
Products with the active ingredient pyrethrins would likely have the ability to kill the beetles on contact, but they would also kill many beneficial insects, so please keep that in mind. Products with the active ingredient Bacillus thuringiensis subsp. galleriae (strain SDS-502), can be used to protect plants from beetles with less risk of harm to beneficial insects. This active ingredient must be consumed by insects in order for them to receive a lethal dose, and it only affects insects in the order Coleoptera (beetles). Sprays may have to be applied frequently in order to protect plants from injury. Extreme caution should be taken if insecticides are used on or near flowering plants, to prevent harm to pollinators. Remove blossoms before applying pesticides to flowering plants and apply the product in the evening when pollinators are less active. The product label will contain additional instruction for its use that will ensure that you are using it in compliance with state law and in a manner that will ensure its effectiveness, your safety, and the safety of others.
