Japanese beetles remain frustrating

Phil Pellitteri, UW-Extension Insect Diagnostician
Department of Entomology
College of Agricultural and Life Sciences

Phil Pellitteri talks about the continuing Japanese beetle invasion.




3:07 – Total Time

0:13 – Japanese beetle likely to spread more
0:54 – What to do with them
2:12 – Life cycle of the Japanese beetle
2:30 – Natural defenses slow to help
2:57 – Lead out


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Sevie Kenyon:
What about the Japanese beetle this season?

Phil Pellitteri: I think the things we can easily expect are that we continue to see it in new areas of the state. It’s picked up as far north as Barron County on the west side and up into Oconto County on the east side. If you have not dealt with this insect before, when it starts to become active it will present some problems that you just have never had to experience. They’re a bright metallic green beetle with brown wing covers, and maybe the size of your little fingernail. You will start to see activity on grapes, roses, on raspberries, but technically it can feed on over 300 species of plants so we’re even talking about Birch trees and Linden trees and Purple Leaf Plums.

Sevie Kenyon: And Phil, what do you do if you get an infestation of these beetles?

Phil Pellitteri: The frustrating thing about this insect, aside from it being active for two months, is that most of the time when it’s attacking the plants in your back yard it’s flying in from down the road. Most of the time we find that the grubs, which are a turf pest, are not necessarily in the local lawns, they’re coming in from areas down the road and this makes it very difficult. Lots of materials work against them but the materials that you put on as a foliar treatment only last for about a week at best. So, under heavy populations you’re forced to treat a lot of the susceptible plants numerous times which is just not what most people would think about good gardening and it really takes the fun out of things. There are systemic insecticides that can be poured on the roots that the plants will uptake and the advantage of the systemics is that they will last for a whole season but the dilemma with the systemics is that you got to get them on early because they often need to be available to the plant at least 3 to 4 weeks before the Japanese beetles come on. You know, some of the problems, like for raspberries, just about the time we’re ready to harvest them the beetles show up and although we got products that work, anything we use are going to delay harvest because we have to follow the preharvest intervals of the particular products. As I said, it’s a very frustrating insect to deal with.

Sevie Kenyon: And Phil, can you give us a little thumbnail sketch of the life cycle of this insect?

Phil Pellitteri: One generation a year. The adults tend to lay their eggs in very lush sodded areas and then they go through their transformation and then we see the adults typically about the 1st of July but again this year with the dynamic they’re expected to be a week to ten days early would not surprise me one bit.

Sevie Kenyon: Are there any natural predators available?

Phil Pellitteri: One of the interesting phenomena that we have witnessed in Wisconsin and seen in some other states is areas where they have been established for more than 10 years we’re seeing a natural decline in the populations. This we suspect might have something to do with some natural diseases that are often moving in too. So, it honestly has made life considerably better but, unfortunately, it’s still an insect that you have to deal with and so even with these natural controls life is much better before Japanese beetles show up than after.

Sevie Kenyon: We’ve been visiting with Phil Pellitteri, Department of Entomology, University of Wisconsin, in the College of Agricultural and Life Sciences, Madison WI and I’m Sevie Kenyon.

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