For Release July 20, 1999

June Bugs and Grubs

by Chuck Otte, Geary County Extension Agent

Sometime last week, homeowners started noticing large flying objects in their yards and around their trees. At first glance these large buzzing insects appeared to be bumblebees. Well, chock one up for insect mimicry. Upon landing, these large buzzing bumblebee acting insects turned out to be the Green June Beetle.

While the presence of this large beetle can be startling, especially if there are five or six or fifty flying around your yard, they are essentially harmless to humans. They will tend to fly at you and may try to land on you but they really just have one thing on their minds, sex! They are trying to find a mate and then the females are trying to find a good place to lay eggs.

Like all of the May and June beetles, the eggs hatch into white grubs. The larvae of this particular June Bug feeds on decaying organic matter. The adult, when not preoccupied with sex, feeds on developing fruit and can become a problem on apricot and peach crops and sometimes even on melons. Normally there are not enough of them and they are not around long enough to be a serious problem, BUT their less noticeable cousins that appear a little earlier in the summer can be a real pest in lawns.

The Southern Masked Chafer and the May or June Beetle are the adult forms of white grub species that can be very devastating to lawns. Some of these species have a one year life cycle, some have a three year life cycle. Fortunately the egg laying for both species occurs at about the same time. Control is most effective when the grubs are small and close to the surface which is in late July and August for all the damaging species.

I do not like to treat lawns for grubs unless there is a known problem. Most all lawns will have a few grubs. A few grubs are not a problem, but when your lawn has more than about a dozen per square foot you will probably start to see problems, especially if it turns hot and dry in July and August.

The most visible sign will be areas of the turf that just die out. Unfortunately we also have active disease problems that may give a very similar look. Go out and grab the dead grass in your hand and pull gently. If it’s disease problems the grass blades will easily come off in your hand, breaking off at ground level. If it’s a grub problem the grass blades will not easily come out of the crown. If you cut a little section of the turf you may find that it will then pull back easily and you will probably find grubs feeding right under the roots. If you are seeing damage and can find active grubs then you have sufficient reason to treat. If you don’t see symptoms and if you haven’t had a grub problem, don’t waste your time with a preventative treatment. I can show you a lot of lawns that look fine and have never been treated for grubs so don’t be pressured into a "just in case" application.

There are a couple of steps that you need to do to maximize the effectiveness of the control treatment. One application per season is adequate if done at the right time, but I do recommend treating two or three years in a row. If it has not been raining, water the lawn thoroughly before the application. After the insecticide has been applied, water again with enough irrigation to wash the chemical into the top three or four inches of soil. The chemical has to get down to where the grubs are feeding to do any good. Grubs can be a destructive nuisance, but many lawns never have to be treated. If you have a problem, now is the time to get busy controlling it. If you don’t have a problem, spend your time staying cool!


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