UPDATE – JULY 22, 2016: Are beetles killing your linden tree? Japanese beetles feed on hundreds of different plants. However, lindens are one of their favorites. Defoliation of well established, healthy lindens (and other varieties) is usually not fatal even though damage can look severe. Defoliation is most harmful to recently planted trees within the past few years and trees in poor health. To help trees recover, the curative treatment process described above is recommended paired with several long deep-root waterings weekly.
Original Article – July 15, 2016
It’s July and Japanese beetles (AKA: “June bugs”) are emerging from their underground lair to begin their adult lives feeding, breeding, and laying eggs. This imposes a 2-part problem when it comes to protecting your landscape lawn and ornamentals. First, adult beetles are feeding voraciously on the leaves of trees and shrubs, causing major foliar damage. Their feeding habits “skeletonize the leaf” as they eat from the inside out. Second, these adults are readying to breed and lay eggs. These eggs hatch into grubs that love to eat the roots of your grass and can destroy your lawn. The time table for this is quick too, so curative and preventative measures should be considered as part of grand strategy. Like any Integrated Pest Management (IPM) program, management consists of properly identifying grubs, analyzing damage thresholds (in some cases, damage may not be a major concern), timing pesticide application appropriately, and monitoring the treated area for results.
These Japanese beetles prefer moist (but not saturated) soil to live and lay their eggs in. Since the weather has been hot and dry this month, irrigated lawns are attracting Japanese and similar beetles like a magnet. Now is the perfect time to secure a curative Japanese beetle treatment for the summer (which we are starting next week) and a preventative grub treatment for the fall. Curative treatments are foliar applications (ie: applied to plant leaves) that target the beetle stage while they feed before they return to the soil to lay eggs. As is the case with all insecticidal products, foliage should be thoroughly treated. The products should be applied in multiple applications to prevent re-infestation. Pesticides should always be used as a last resort and with great care. Pesticides have unintended consequences too, so they should be applied when our beloved honey bees are not foraging. And those wishing for a more organic option are unfortunately out of luck, as these types of applications to control adult beetles are generally ineffective.
Preventative treatments target the grub stage and are generally applied in late spring/early summer for maximum results. Our crews have recently concluded our last preventative treatments for the year. If you have not applied these types of preventative measures in the past, they should be considered for next year. They can, with some success, be applied in September as well if infestations are deemed particularly damaging. Preventative grub treatments, in particular, need to be watered in. Otherwise, they will be foliar absorbed or bound up in thatch.
Given the dry conditions so far this year, if you have an irrigated property, your lawn is going to be a hot bed for grubs. The beetles are attracted to these moist soil conditions and your lot is going to be prime real estate for them. If you did not put a preventative treatment down, you may wish to consider a late summer treatment.
One final note on beetle damage, it helps to know their favorite go-to selections in the salad bar. Japanese beetles in particular love cherry, birch, linden, crabapple, plum, and rose plants. If you have these planted within the landscape, focus your monitoring efforts on these specimens.