Japanese Beatle Damage on River Birch - Ask Extension
My 4 yr old trees were damaged by Japanese Beetles last summer. Lots of small dead branches (twigs) but leaves budding out at the ends of branches. I ...
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Japanese Beatle Damage on River Birch #831039
Asked May 20, 2023, 10:03 AM EDT
My 4 yr old trees were damaged by Japanese Beetles last summer. Lots of small dead branches (twigs) but leaves budding out at the ends of branches. I can trim the small dead parts of the branches. In late summer last year I put down a grub control product but unsure if that will help. Some of the lower branches look terrible with just a few leaves. Can I cut the lower branches off now. The branches are approximately 3/4 inch circumference as they are just a few years old. I did sprinkle Bio Advanced Tree and Shrub Protect and Feed early this spring. Will this help? Or what product can I put down now? It pains me to look at the trees and want to do something that will save these young trees (I have 2). Thanks for your help! Also I have not experienced any grass damage from the grubs.
Wright County Minnesota
Expert Response
The product you listed says it will kill Japanese beetles up to 12 months. It contains imidicloprid which is a systemic treatment. Unfortunately it also kills good insects like bees. This is not a problem unless the trees are flowering. In the future you may wish to time the treatment after the birch flowers in May. Using a slow release fertilizer like this will help the trees recover.
Pruning birch trees in the spring can further stress trees that are damaged because they release sap. It is best to prune them in the fall. Dead branches can be pruned out anytime.
https://www.gardeningknowhow.com/ornamental/trees/birch/cutting-back-birch-trees.htm
That product does not solve the grub issue. They are most likely breeding in the lawn. The best time to treat the grubs is when they are small and near the surface in late July through August. Do not treat the lawn unless you see actual grub damage. The following websites give additional information.
https://extension.umn.edu/yard-and-garden-insects/japanese-beetles
Pruning birch trees in the spring can further stress trees that are damaged because they release sap. It is best to prune them in the fall. Dead branches can be pruned out anytime.
https://www.gardeningknowhow.com/ornamental/trees/birch/cutting-back-birch-trees.htm
That product does not solve the grub issue. They are most likely breeding in the lawn. The best time to treat the grubs is when they are small and near the surface in late July through August. Do not treat the lawn unless you see actual grub damage. The following websites give additional information.
https://extension.umn.edu/yard-and-garden-insects/japanese-beetles
Thanks so much for the wealth of information. Angie Ambourn also reached out with information.
Bonnie Inforzato
Bonnie Inforzato
Saint Michael
On May 20, 2023, at 9:30 AM, Ask Extension <<personal data hidden>> wrote:
You are welcome.
