Thanks for the question.

Looking at the leaf pictures you sent, the most striking characteristic is that the holes on the leaves generally occur between leaf veins. This situation is known as “skeletonization”. This is a strong indicator that your horse chestnut tree was attacked by adult Japanese beetles (Popillia japonica). For whatever reason, they are especially common in the Metro Area this year. As you are witnessing, the adults feed between the major leaf veins. This leads to the remaining tissue turning brown, falling out, and producing a lacy appearance.

Moving forward, these are my thoughts and suggestions:

1). For a large, established, otherwise healthy horse chestnut, although the damage you see appears alarming, it is primarily cosmetic. Mature healthy trees can tolerate considerable Japanese beetle feeding without lasting injury. In other words, the tree is not in any immediate danger. While these damaged leaves may not be replaced this year (2026), and barring a 2027 outbreak of Japanese beetles, the tree should show normal foliage next year.

2). If you wish at this time, knock or handpick beetles into a container of soapy water on the branches you can reach. Morning or evening is easiest because the beetles are less active. Repeat daily while substantial numbers remain. If you are so inclined you could remove the damaged leaves, but this would simply be to improve the overall appearance of the tree.

3). There are traps available under the guise of “pheromone traps”. DO NOT USE them. They will simply attract more beetles to your poor tree.

4). Insecticides such as Neem oil could be used but, in your situation there really is no need to do so. I suspect that most of the adult beetles have now mated and laid eggs in the soil. These adults will soon, if not already, have died.

For further information on these and related points, see:

https://extension.umn.edu/yard-and-garden-insects/japanese-beetles

https://www.mda.state.mn.us/plants-insects/japanese-beetle

https://www.lakevillemn.gov/DocumentCenter/View/2948/Japanese-beetle-brochure?bidId=

The major question remaining and one that is very difficult to answer at this point (early August 2026) is if there will be a 2027 beetle attack upon your tree. Just be prepared to pay close attention to the tree’s leaves once they appear in 2027. At the first sign that there is leaf damage, application of an insecticide would be appropriate.

Good luck. Please get back to us with any additional questions. Thanks for using our forum.

Thanks for the question.

Looking at the leaf pictures you sent, the most striking characteristic is that the holes on the leaves generally occur between the various leaf veins. This situation is known as “skeletonization”. This is a strong indicator that your horse chestnut tree was attacked by adult Japanese beetles (Popillia japonica). For whatever reason, they are especially common in the Metro Area this year. As you are witnessing, the adults feed between the major leaf veins. This leads to the remaining tissue turning brown, falling out, and producing a lacy appearance.

Moving forward, these are my thoughts and suggestions:

1). For a large, established, otherwise healthy horse chestnut, although the damage you see appears alarming, it is primarily cosmetic. Mature healthy trees can tolerate considerable Japanese beetle feeding without lasting injury. In other words, the tree is not in any immediate danger. While these damaged leaves may not be replaced this year (2026), and barring a 2027 outbreak of Japanese beetles, the tree should show normal foliage next year.

2). If you wish, knock or handpick beetles into a container of soapy water on the branches you can reach. Morning or evening is easiest because the beetles are cooler and less active. Repeat daily while substantial numbers remain. If you are so inclined you could remove the damage leaves, but this would simply be to improve the overall appearance of the tree.

3). There are traps available under the guise of “pheromone traps”. DO NOT USE them. They will simply attract more beetles to your poor tree.

4). Insecticides such as Neem oil could be used but, in your situation there really is no need to do such. I suspect that most of the adult beetles have now mated and laid eggs in the soil. These adults will soon, if not already, have died.

For further information on these and related points, see:

https://extension.umn.edu/yard-and-garden-insects/japanese-beetles

https://www.mda.state.mn.us/plants-insects/japanese-beetle

https://www.lakevillemn.gov/DocumentCenter/View/2948/Japanese-beetle-brochure?bidId=

The major question remaining and one that is very difficult to answer at this point (early August 2026) is if there will be a 2027 beetle attack upon your tree. Just be prepared to pay close attention to the tree’s leaves once they appear in 2027. At the first sign that there is leaf damage, application of an insecticide would be appropriate.

Good luck. Please get back to us with any additional questions. Thanks for using our forum.