Dr. Grow: Summer issues are watering and beetles

Wednesday, June 23, 2010
Japanese beetles are feeding on local landscapes. (Fred Lynch)

Judging from conversations with gardeners, there are two major issues affecting gardeners in Southeast Missouri at present. These issues are water -- or the lack thereof -- and Japanese beetles. I have written about both within the last year, but because of the concern, I thought I would touch on the subjects again.

Gardeners often look at plants that are wilting and automatically assume that they need watering. Don't make this assumption. Plants wilt because the roots are not absorbing water fast enough to replenish water lost through transpiration from plant leaves. This can be caused by the lack of water in the soil or from plant roots that are rotting because of overwatering. If roots are rotten because of constant overwatering, they cannot absorb water fast enough to replenish water lost through transpiration.

If you see a plant wilting on a hot and windy afternoon, check the soil. The key to determining when to water is to let the soil tell you when to water, not the plant. If it is dry, water the plant. If the soil is wet don't be tempted to water the plant.

The Japanese beetle infestation in the area seems to be getting more severe. My friend Dr. Sven Swenson lived in Knoxville, Tenn., when the invasion hit that area several years ago. According to him, the population continued to climb for several years before the numbers of beetles began to level off. In other words, get used to dealing with them.

Several pesticides, such as carbaryl, permethrin, bifentherin, malathion and neem oil, can be used to effectively kill the adults feeding on flowers and foliage. If you live in a highly infested area, you may have to spray on an as-needed basis, often weekly.

Judiciously placed traps may attract the feeding adults away from your favorite rosebush. On the other hand, if you live in a highly infested area, the traps may actually increase the population in your landscape. In this case, one trap by itself will not give the results that you want.

Currently Japanese beetles are feeding, mating and laying eggs in the soil under your landscape and lawn. These eggs will hatch within a few days, resulting in an infestation of grubs. For best control, apply imidacloprid to your lawn in late August. This will reduce the chances of root damage to the plants in your landscape this fall and next spring.

Inspect your landscape on a weekly basis. Early detection will help you save a lot of time, money and effort.

Send your gardening and landscape questions to Paul Schnare at P.O. Box 699, Cape Girardeau, MO 63702-0699 or by e-mail to news@semissourian.com.

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