Beetles nibbling away at plants

GARDEN Q&A

Garden Q&A

July 22, 2006|By JON TRAUNFEL AND ELLEN NIBALI | JON TRAUNFEL AND ELLEN NIBALI,SPECIAL TO THE SUN

How can I keep these yellow fuzzy things from eating my bean plants?

Bean plants can tolerate up to 20 percent defoliation before yield is affected, but Mexican bean beetles will defoliate entire plants if left unchecked. Crush all yellow egg masses, the fuzzy yellow larvae, plus the adults which look like coppery ladybugs.

For severe infestations, use insecticides such as rotenone, neem or pyrethrum. Immediately after harvest, destroy infested plants. Next spring, you could also try covering your seedlings with floating row cover to prevent overwintering adults from feeding and laying eggs.

This spring I planted roses. Now I see black leaf spots, and the roses have lost almost all their leaves. I sprayed with insecticide and fertilized, but they still look terrible. What else can I spray?

Black spot disease produces black fungal spots edged with yellow. Eventually, infected leaves turn yellow and fall off. Applying fungicide now will not cure an infected leaf, but it will prevent new infection. To protect bees, don't use a fungicide combined with an insecticide.

How often you spray will depend on weather and the susceptibility of your rose variety. You may need to spray only in especially wet summers. If you need to spray every two weeks for good protection, try alternating between surface and systemic fungicides. Avoid overhead watering that can spread spores.

Next spring, monitor your roses closely and, when the first spot appears, dispose of the leaf and spray with a fungicide. If your roses get black spot badly every year, consider replacement with an improved rose variety. Look for roses labeled not only "resistant," but "highly resistant." Insecticides and fertilizers will not correct a disease problem. Always pinpoint the culprit before you waste time and money spraying.

Checklist

Use a sharp knife to carefully remove squash vine borers from the lower stems of squash and pumpkin plants.

Don't water your lawn during hot, dry weather. Cool season grasses naturally go dormant this time of year and recover in late summer.

Jon Traunfeld, regional specialist, and Ellen Nibali, horticulture consultant, work at Maryland Cooperative Extension's Home and Garden Information Center, which offers Maryland residents free gardening information. Call the center's "hotline" at 800-342-2507 (Monday through Friday, 8 a.m.-1 p.m.) or e-mail plant and pest questions through the Send a Question feature at hgic.umd.edu.

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