Bucks County Cooperative Extension - Over The Fence Newsletter

Japanese Beetle Grubs in Home Lawns

Many of us recall that Japanese Beetle populations were abnormally high in 2005. Beetles fed voraciously on roses, raspberries, Lindens, grapes and their other favorite foods. Why was 2005 such a great year for beetles? Probably because 2004 conditions were excellent for beetle reproduction. Adult beetles emerged early and were active for a long time.

As you may know, after the adult beetles feed on landscape plants they move to turf in July and lay eggs. The eggs hatch and develop into larvae (grubs) which feed on turf. Good soil moisture in July-August plus high beetle populations means good conditions for grub survival. We had all of this in 2004.

The grubs do most of the feeding damage in September and October eating turf grass roots. Lawns often are severely damaged, depending on the grub populations and turf grass growing conditions. Grubs survive winter by burrowing deeper into soil, move back to the surface in the spring, feed a bit, pupate and then emerge as new adult Japanese beetles in June. Then the cycle begins again.

The big beetle populations in 2005 and good soil moisture last July meant lots of turf damage last fall. The abnormally dry September probably made the feeding damage worse, as lawns remained stressed from lack of moisture while grubs ate their root systems. Lawns continued to decline in the dry Spring of 2006 due to damage from fall grub feeding.

What's a homeowner to do? The adult beetle strategy is pretty simple. If you can't stand the feeding damage on your favorite plants, treat them with an insecticide available in garden centers. Beetle traps are just beetle magnets since you catch a bunch but not enough to make a difference. Selfishly, the best situation here is if your neighbor has the traps.

Arborists can handle the big jobs. Arborists (and you) can even do preventative treatments by using soil applied, systemic insecticides now (May). The insecticide imidacloprid (Merit, Bayer Advanced Tree and Shrub Insect Control) is effective against beetles but must be applied about 30 days prior to beetle feeding. It needs to be absorbed by roots and transported to leaves. Beetles are killed by feeding on leaves that have imidacloprid in it. But the wait and see approach is an option.

What about those nasty grubs. Imidacloprid, the soil applied systemic is very effective when applied as a preventative measure. If applied in May or June it even controls some other turf grass insect pests. You can apply it as late as July, during beetle egg laying. It needs to be incorporated by rainfall or irrigation. If you have a history of grub problems or have a zero tolerance for risk, imidacloprid is a good choice. Halofenozide is another preventative soil applied insecticide that can be applied in May-July period and will control grubs that feed in September-October.

However, it is certainly true that every lawn in Bucks County does not warrant preventative grub treatment every year. You can do the "wait and see" approach. If high beetle populations develop in your neighborhood, lay eggs and grub survival conditions are good and you catch all of this in September, you can treat with "curative" insecticides such as trichlorfon (Dylox, etc.) and get good grub control. But you've got to be paying attention. This approach is often a "rescue treatment" for those caught off guard.

The final option is to do nothing. Most years, most lawns will be fine. Perhaps a small grub population develops but turf outgrows the damage. Maybe Mother Nature helps by making grub survival conditions poor in the summer (dry) and conditions for turf recovery in good the fall, (wet).

What about milky spore? If only this biological control were as good as we wished. If just won't cut the mustard in the face of high grub pressure. No harm done if you use it. Many of you have natural population of these soil bacteria already. Most of the folks who apply it and think it is protecting them simply don't have a problem. The "do nothing" approach means you may get clobbered occasionally. You know the risks. You get to re-establish your lawn from scratch.

What can we expect in 2006? Don't be surprised if beetles are back…big time. Conditions in 2005 set us up for a repeat of last year's grub infestations. This is not a prediction; Mother Nature always has a few tricks up her sleeve…but be ready for Beetlemania 2006.

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Master Gardener Corner

The 2006 Southeastern Regional Home Hazardous Waste (HHW) Drop Off Program is scheduled for the following times and locations in Bucks County:

For more HHW information, go to the County website: www.buckscounty.org and in the upper right corner click on "How do I... Recycle in Bucks." This will take you to the HHW information page, where you can find directions, maps, a flyer and a brochure about the program.

The Middletown Grange Fair, Penns Park Road in Wrightstown this year is Wednesday August 16 through Sunday August 20. This year there will be a lot of excitement in the 4-H Building (Building No. 2). Come see the Bugmobile and learn about good bugs. The Master Gardeners will be holding a container garden competition, so come and cast your vote for the best container garden. Bring your children ages 4 to 10 to make small gardening projects at the Master Gardener booth (click here to see more about this).

Penn State has a great series of vegetable fact sheets for the home gardener, including:

These fact sheets can be printed from Penn State's web site. Go to http://pubs.cas.psu.edu/Publications.asp.
Search by Title/description and type in "Growing _____"; entering the vegetable of interest. Or you can call the Extension office at 215-345-3283 and we will mail you a copy.

Penn State also has great publications on growing berries and other small fruit which can also be accessed through the Publications web page. In addition, once those fruits and vegetables are in season, Penn State has a whole series on food preservation techniques. Search the publications web page for "Let's preserve", and view the whole series. These fact sheets can be printed from the web, or ordered through extension.

Scott Guiser, Extension Educator/Horticulture
and
Sue Schneck, Master Gardener Coordinator

May/June 2006