KC Gardens

Your garden hosts good bugs and bad bugs, including one that’s eating up rose leaves

By Dennis Patton

Damage from rose slugs.
Damage from rose slugs. Submitted.

When we hear the word insects our first thought is something bad. But there are a number of good guys active in the landscape.This week let’s take a look at an insect that is causing damage and one that comes to our rescue.

The bad: Rose slug

This insect has been skeletonizing rose leaves for several weeks in the Kansas City area. Interesting enough this green caterpillar-looking insect is not really a caterpillar. Caterpillars are the larvae stages of moths or butterflies. What you’re seeing on roses is really the larval stage, or technically a slug, of a group of insects called sawflies.

Close examination of this small, half-inch larva will reveal very fine, hairlike spines in clusters. Young larvae will remove the green layer of a leaf leaving behind a clear material. As the larvae mature, they make holes in the leaf and eventually may consume all but the major veins of the leaf.

Since these insects are not caterpillars, commonly used products like BT, found in Dipel and Thuricide, will not be an effective treatment. These insecticides are favored by many gardeners as they are considered organic. The best control and still organic may be a strong jet of water which will dislodge the slugs and make it difficult for them to return to the plant. Other effective treatments include insecticidal soap, horticultural oils, spinosad, and permethrin.

The good: Lady bugs

Both the adults and the larvae of the ladybird beetle are beneficial and do not feed on plants but rather on other insects including aphids, mealybugs, whiteflies, scale insects and the eggs of various other insects. Lady bugs or ladybird beetles are now active in the landscape. Our office gets a number of calls each year with people wanting to kill one of the most beneficial insects.

So if you see these insects, do not spray. The larval form looks like a very small alligator-shaped insect. Larvae are covered with spines, about 3/8-inches long, and black with orange markings. Once you have seen the larvae it is easy to remember.

Scouting the garden is a great way to spot insect populations that may be developing. Even though our first thought is that a bug in the garden may be bad, remember, there are more good bugs than bad ones.