Where Have All the Japanese Beetles Gone?

- Written by Steve Toth, NC Cooperative Extension Specialist 

http://blogs.extension.org/mastergardener/2011/09/28/answering-minnesota-japanese-beetles-in-minnesota-2011/

It is late June and so far I have not seen any Japanese beetles. I have a couple reports from around North Carolina and even reports that they are emerging in Maryland. So I guess they are trickling out but populations seem to have gotten lower and lower in the past several years. For three years in a row we have had severe droughts during the time Japanese beetles are ovipositing. They need moist soil so their eggs do not dehydrate and so tiny young larvae can borrow into the soil. Droughts have restricted successful reproduction to only well irrigated areas.

So keep an eye out and remember a few key things. Japanese beetle traps do not offer any protection to landscape plants and may actually attract more beetles on to your property so hang them in your neighbor’s yard. Likewise, treating a lawn for Japanese beetles grubs will not reduce defoliation of plants on that property since beetles fly in from great distances. Long-term protection for landscape and nursery plants can be achieved a neonicotinoid insecticide such as imidacloprid (e.g., Merit, Marathon II) or acetamiprid (Tri-Star). A new product with extremely low vertebrate toxicity but good efficacy for a number of pests including Japanese beetles is Acelepryn (chlorantraniliprole). For more information on the biology and management of adult Japanese beetles in nurseries and landscapes consult the insect note at http://www.ces.ncsu.edu/depts/ent/notes/O&T/flowers/note147/note147.html.