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Here They Come

Posted by Richard Hentschel -

Japanese Beetles are about to show up in our area. They have already shown up in Southern Illinois and expected in Central Illinois next week. We should begin to see them about a week later during the first week or so in July. That's the bad news. The good news is that we should expect to see fewer beetles, courtesy of the drought of 2012. Since they do not read the journals, you may see some early ones in your landscape ahead of the major invasion. They are not scouting out a food source for the others, just there earlier!

The female Japanese Beetles prefer moist soil to lay their eggs in and we did not have much of that last year in mid to late July when they lay eggs in our area after having feeding heavily on their favorite plants and found a mate to start the egg laying process. Two things happen at egg laying time that influences how many beetles we could expect to see. The drier the soil, the longer it takes for the female beetle to dig the hole where she deposits the eggs. The other thing is that it takes soil moisture to allow the recently laid egg to swell and hatch into the larvae stage.

The part of this story is that for the grub larvae to be developed enough to survive, there needs to be over ten inches of rainfall. For those location that did receive a lot more water last summer through irrigation, Japanese beetle emergence numbers will be about the same as in previous years.

 

 

 

Japanese Beetles are general feeders and as young adults really like turf and smartweed. Some of their favorite plants are linden trees and ornamental roses, with an appetite for a much wider diet in the landscape the older they get. The beetle does not just find a suitable host to feed upon and stay there. The beetles will feed for three to four days and move on to another host plant. There feeding on the leaf causes those cells that they do not eat to die and turn brown, later the dead cells fall from the leaf leaving irregular shaped holes. On linden leaves they skeletonize the leaf just leaving the veins in place. If you have lots of beetles and they are feeding on linden, they will line up like a "British square" and march down the leaf, feeding as they go.

There are a variety ways to handle the beetles. Hand picking works if the numbers are small. Using a bucket with soapy water is the next step. Hold the bucket under a branch full of beetles and give the branch a quick hit. The beetles will defensively let go of the plant and fall away right into the bucket. If the need is to make a pesticide treatment, carbaryl works well and will need to be reapplied every few days as you see beetles show back up and should be applied the first time as soon as you see feeding start. There are the newer systemic insecticides that can be used too. This maybe the year not to routinely apply a grub control product to the lawn until you know that the beetle larvae are numerous enough in the lawn to warrant a treatment. Read the label for any pesticide you chose to be sure you are mixing, applying, disposing of the product correctly. Most problems of a treatment failure can be traced back to being in a hurry and not following the label instructions.

 



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