Summer Yard Crashers
Written by: Kyle Babicky, Certified Arborist WI-0889A
The Fourth of July holiday is a day that we often spend enjoying beautiful summer weather outside with family and friends. You may have spent the holiday weekend sitting on the patio, and soaking in sunshine. While the Fourth of July is a day to celebrate our freedoms, it is also closely correlated with the emergence of a frustrating landscape pest. Japanese Beetles.
Japanese beetles are an insect that feeds on leaf tissue. Their timing each year can vary. Adult beetles usually emerge in early to mid-July. Their feeding ramps up the latter half of July through August, and into September. Some of their favorite foods include lindens, roses, crabapples, and birches. These favorites can experience heavy defoliation in some years. Many other species are also affected.
A tree completely defoliated by Japanese beetles will almost always have new, healthy leaves the following spring. However, repeated defoliation can weaken a tree, setting it up for borer insects or other issues. You may want to take measures to retain healthy leaves moving forward if you’ve experienced Japanese beetles feeding on your trees.
There are two treatment options to combat these pests:
- One treatment is applied as a soil drench. Tree roots absorb this product and move it throughout the plant. This provides systemic control of Japanese beetles. One exception is that this product cannot be used on Lindens.
- The other treatment is a foliar spray on the leaves. This will kill the beetles on contact, and also have a residual effect to limit feeding from additional beetles coming in for a period of time. The product used for this treatment has been shown to limit negative impacts to pollinator insects.
There are two Japanese beetle control questions commonly asked by clients:
Will treating lawn grubs help with Japanese beetle control on the trees? It is true that the larvae stage of Japanese beetle is a lawn grub that can cause turf damage. However, lawn grub treatments will not reduce the adult beetle feeding on your trees. Even if you could eliminate every lawn grub from your yard, Japanese beetles are very strong fliers and will come in from a wide area.
Should I use the Japanese beetle traps? We do not recommend using traps. The University of Wisconsin Extension states that traps just attract more beetles due to the pheromones used. The traps may give the illusion of being effective when they fill up with beetles. However, the results are negated or even worsened by attracting more beetles to the yard.
Your Wachtel Tree Science arborist would be happy to answer your questions on these frustrating pests. Please don’t hesitate to call us if you think your trees or shrubs are having issues with Japanese beetles!