Caterpillars can damage your grapevines

This year we had a couple grapevines attacked. If, like us, you have noticed the leaves look like a net with the tissue missing and only the veins left on the leaves. Under the leaves, you find small black and yellow caterpillars. Your grapes have an infestation of grapeleaf skeletonizers.

The black and white wormlike insects are the larvae of the western grapeleaf skeletonizer. This very common pest to grapes is very common to the Antelope Valley, as well as the rest of California.

Mature caterpillars are about one-half inch long with several yellow and black bands with two purplish bands. The caterpillar also has tufts of long black spines. These spines have a stinging sensation if touched. So be careful in handling the leaves.

The caterpillars first appear, in early summer, and produce three generations, during the year. They eat the underside of the leaves first, followed by eating all the tissue between the veins of the leaves. This causes a skeleton looking damage to the leaves.

A very safe control for grapeleaf skeletonizer is Bacillus thuringiensis, also known as B.t. B.t. is an insect pathogen, which means it makes the insect sick and finally kills the insect.

B.t. is considered completely safe to all people and animals. It is also considered an organic pesticide. It kills most all caterpillars on any plant, including tomato hornworm on tomatoes.

Other chemical pesticides are labeled to control grapeleaf skeletonizer, so be sure to check the label. Since the grapeleaf skeletonizer attacks from the bottom of the leaf, you must be sure to spray the underside of the leaves to control the insect.