How to help your roses fend off the problem beetles ahead

Pest damage on our beautiful rose blooms rankles deeply, but it motivates us to take the appropriate actions to put the culprits to rest.

Two types of pest beetles are annual regulars in our San Diego rose gardens, so mark your calendars. Expect hoplia beetles to make their unwelcome entrance in the spring and fig beetles to crash your garden in the summer.

Pests are never welcome, but when we know when they are coming, we can minimize their damage.

Every pest leaves a signature symptom. Regularly monitor for symptoms and you will find the culprit before too much damage is done.

Know the enemy

The hoplia beetle: Chewed-up petals and holes in our rose blooms lead us to suspect that either hoplia beetles or caterpillars are at work. If the damaged blooms are mostly our light-colored roses — the whites, yellows and pinks — and it is early spring, there is a good chance the pests are hoplia beetles. Mercifully, there is only a single generation of these beetles each year.

The hoplia beetle measures about a quarter-inch long. It is mostly brown with a darker head and thorax. The adult is brownish-gray with brown wing covers and a very slightly iridescent silvery underbody. Female beetles lay glossy white eggs in the soil. The whitish larvae are C-shaped with a bulbous posterior. They feed on decaying vegetation and plant roots but do not feed on roses’ roots. They develop slowly, remaining in the larval or pupal stage throughout the winter.

In early spring, when the environmental conditions are right, the adult beetles emerge from the soil and fly to gardens, where they feed on roses and other flowers. They do not feed on leaves, just our beautiful buds and blooms. After feeding for several weeks, they fly back to their egg-laying sites.

In San Diego, hoplia beetles’ onslaught on our roses has a short time span — from late March to early May. But be prepared for an army of beetles. Last year in mid-April, I counted and disposed of around 50 beetles each day in my rose garden. In the first week of May, there were only a few stragglers. Happily, by mid-May, the hoplia beetles were gone for the year.

In the summer, metallic-green fig beetles loudly announce their arrival with buzzing sounds. They zoom into gardens to feast on ripe peaches, figs, apples and roses.

(Rita Perwich)

The fig beetle (also known as the green fruit beetle): In the summer, metallic iridescent green fig beetles loudly announce their arrival with buzzing sounds. They zoom into our gardens to feast on our ripe peaches, figs, apples and roses.

Adult fig beetles are large, measuring up to 1 1/3 inches long. Their habitat is the southwestern United States and Mexico. They have prominent legs and antennae. Some people mistakenly think they are Japanese beetles or June beetles, which are pests found in the eastern United States. Fig beetles mate, and the female lays oval white eggs in the soil just beneath organic matter. The eggs hatch in a week. During spring, larvae mature and pupate in a cell of soil particles. The larval stage is the longest period of their life cycle.

The adults are a menace from late June to early fall, feeding during the day on soft-skinned ripe fruits such as peaches, apricots, plums, figs and apples. Their tastes also include rose petals. Again, there is fortunately only a single generation of these beetles each year.

Take back control

Insecticides are not necessary to get rid of beetles. Using the soapy bucket method pictured here will suffice.

(Rita Perwich)

Throughout the years that I have dealt with both of these types of beetles, I have learned that I have three advantages in capturing them:

• Both hoplia and fig beetles are easy to spot: the hoplias because of the contrast of their dull brown-gray color against the light-colored roses, and the fig beetles because of their bright metallic green color.

• Both varieties of beetles get very focused on feeding, so they don’t see me coming to get them.

• Neither variety bites.

Disposal and avoidance

The soapy bucket method: Add a few drops of detergent to a bucket half filled with water. Drop the beetles into the bucket. When you discover a multitude of fig beetles clustered on one piece of fruit or one rose bloom, cut off the entire fruit or bloom and shake the beetles off into the water. Once in the soapy water, the beetles are captive. They cannot get out.

Insecticides are unnecessary and of little value against these pests and are not recommended.

With fig beetles, remove soft, ripe and mushy fruit from the trees and the ground to keep the pests from being attracted to your garden.

We are often advised to cultivate the habit of being grateful and giving thanks. In our San Diego rose gardens, we can and should be grateful that we do not have Japanese beetles. We can and should give thanks continuously for all the beneficial beetles in our garden: the soldier beetles, ground beetles, rove beetles and especially our very pretty friends, the lady beetles.

Rita Perwich is a member of the San Diego Rose Society, a consulting rosarian and a master gardener with the UC Cooperative Extension. ◆