Caterpillars making a meal of oak leaves

GARDEN Q&A

September 01, 2007|By Ellen Nibali and David Clement | Ellen Nibali and David Clement,Special to The Sun

A gang of caterpillars is taking out the leaves on one branch of my oak tree. It's too late for gypsy moths, and there's no tent or web, so what are they?

Orangestriped oakworms are extremely gregarious. These caterpillars of a native moth start out as pale-yellow larvae and eventually become black and yellow-orange striped. They have two short black spines, like antennae, behind their heads.

Typically, they feed on one branch at a time and don't do enough damage to merit chemical control. You can manually remove those within reach. Horticultural oil or Bt can be used on young ones.

Individual stalks of my veronica, ageratum and now mums are dying and falling over. How can I keep this plague from spreading to my whole garden?

Hot weather can trigger Southern blight fungus in a whole host of plants, including herbs, annuals, perennials and vegetables. Stems or entire plants can wilt and collapse.

Look for white, threadlike mycelium of the fungus at the base of the plant or on adjacent soil. Also check there for round, tan reproductive parts called sclerotia that look like mustard seeds. Typically, this fungus does not kill roots.

Cut off any infected plant parts, and the plants should be able to regenerate next year.

Checklist

Have trees inspected by a licensed arborist if they have fleshy, shelflike fungal structures on their trunks.

Avoid the temptation to buy bargain fruit trees this fall. They may be stressed and of poor quality. Fruit trees tend to grow better when planted in the spring.

Ellen Nibali is the horticulture consultant and David Clement is the regional specialist at Maryland Cooperative Extension's Home and Garden Information Center, which offers Maryland residents garden- ing information at 800-342-2507 or through the "Send a Question" feature at hgic.umd.edu.

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