Japanese beetles (I think) vs raspberries

Asked March 15, 2019, 11:50 AM EDT

Is there something I can do to the soil as soon as the snow is gone to combat raspberry pests? I was told the Japanese Beetles hatch in the ground. (?) I mowed the bushes off last fall so have full access to the patch. Are these two different species... or different stages of the same? How can I stop them this year?

Anoka County Minnesota

1 Response

Thank you for the question. The two photos are of different insects. The first one is an adult Japanese beetle, but I'm not sure what the second insect is so I'll only reference Japanese beetle information in my answer.

Japanese beetles are attracted to many plants including raspberry. Life cycle: Adults emerge from the soil starting in late June or early July, then feed, mate, and lay eggs. Their activity is most intense over a 6-8 week period, and then they gradually die off. Individual beetles live for about 60 days. During that time, females can lay a total of 60 eggs. JB numbers fluctuate from year to year. An important factor influencing their abundance is the soil moisture when they lay eggs (July and August). Eggs and young grubs are very susceptible to dry soils. The regular rains that have occurred the last several summers have been a big factor in the higher numbers of JB.

Physical removal can be an effective method, especially when you are trying to protect a crop you want to eat, although it is not practical in large gardens or for trees. When you remove JB by hand, dispose of them in a bucket of soapy water to kill them. They are heavy and slow so are easy to knock into a the bucket. You can also cover plants with a light weight fabric, like cheesecloth or lightweight white landscape fabric to exclude JB. When using this approach, you will need to cover after the plants have been pollinated, otherwise you won't get a crop. Careful daily observation is key when the plants bloom. Remember that if using fabric, you must securely cover the plant all the way down to the ground to prevent beetles from crawling underneath. If you use any chemical control, read and follow the product label exactly to minimize unintentional environmental side effects to other insects, soil microbes, our water supply, birds and other mammals. You also want to ensure that your raspberries are safe to eat.

Grub control is not advised unless you see areas of your lawn dying from grub feeding. This is because the beetles are capable of flying several miles in search of food and even if you managed to somehow eliminate every beetle or grub from your property, more would fly in from elsewhere.

There are a couple of effective low impact insecticides; Pyola and Neem oil. They can help protect plants from JB, especially if only small numbers are present. However, insecticidal soap, extracts of garlic, hot pepper, or orange peels are not effective.
There are several residual insecticides that are effective, such as carbaryl and permethrin. However, they will probably need to be applied more than once. To protect bees, apply them during late evening after bees are no longer active. The products should be dry by morning when bees become active again. Systemic insecticides are also effective and only need one application but do not apply them to plants that are bee attractive.

Learn more about control methods and how to recognize JB feeding damage in our Extension publication: https://extension.umn.edu/yard-and-garden-insects/japanese-beetles
You may find our information on growing raspberries and dealing with other raspberry pests useful. Scroll down to the "Raspberry" section: https://extension.umn.edu/find-plants/fruit
Thank you for contacting Extension.