Plants wilt despite watering

BACKYARD Q&A

July 23, 2000|By JON TRAUNFELD

Q. My yellow squash and cucumber plants are wilting even though I water them every other day. I looked for the squash borer (which I've dealt with in years past) but see no sign of holes in stems. Is there some disease causing the wilt?

A. Yes, your plants are probably infected with bacterial wilt disease, which is spread by cucumber beetles. You may notice individual stems wilting during the day and recovering somewhat at night. The disease spreads through the plant's vascular system causing plants to collapse. The only remedy is removal. You can safely compost dead plants because the disease overwinters in the gut of cucumber beetles, not in the infected plants. Prevent this fatal disease next year by protecting seedlings from cucumber beetle feeding. 'County Fair' is a pickling cucumber with resistance to bacterial wilt disease.

Q. Our family and the neighbors have been overrun in recent weeks by a beetle that eats flowers, gathers around outdoor lights and is a general nuisance. They are not Japanese beetles, but they are the same size -- tan with black marks. Is this a new pest? How damaging is it? When will it go away?

A. Sounds like you're experiencing an unusually large, localized outbreak of the Oriental beetle, an imported pest that has been in Maryland for a number of years. The adults are active now, as you have observed. But they only cause minor damage to plant flowers. They mate in June and July. Eggs are then inserted into the soil, where larvae hatch out and overwinter. The larvae do feed on the roots of cool-season turfgrasses, so look for signs of damage next year -- patches of dead grass that pull up easily and have no roots.

Q. I'm very concerned about two dogwoods in my front yard that seem to be dying. Several limbs have no leaves at all and I see brown patches on many of the remaining leaves. A friend suggested this is the dreaded discula disease. On top of that, the trees get a bad case of powdery mildew almost every year. Is it worth trying to rescue these poor trees?

A. A lot depends on the value of the trees to you. Are the trees a focal point for your landscape? Do they have sentimental value? It's likely that discula anthracnose is killing your trees. The prognosis is bleak if the disease has already entered and killed large branches. Dogwoods are not expensive to remove and replace compared with larger trees. To try to salvage the trees, you will need to remove the dead branches during dry weather as well as any water sprouts that grow along the trunk and main branches. Rake up and dispose of fallen leaves and apply a labeled fungicide this fall when the leaves change color and again next spring at budbreak. Powdery mildew is a persistent problem that can be controlled with horticultural oil sprays.

THIS WEEK'S CHECKLIST

1. Sow snap beans, cucumbers and squash for a September harvest.

2. Cicada killer wasps are large, ground-dwelling insects you may notice buzzing around your yard. They look menacing but are only harmful to cicadas. They should be left alone.

Backyard Q&A is by Jon Traunfeld, regional specialist for the Home and Garden Information Center, Maryland Cooperative Extension Services of the University of Maryland. For additional information on these questions, or if you have questions of your own, call the center's hot line at 800-342-2507, or visit its Web site at www.agnr.umd.edu / users / hgic.

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