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- Jun 2, 2021

The Ultimate Beauty of Rose Stamens Can Be Ruined in a Day

by Connie Pelissero, Consulting Rosarian, Marin Rose Society

This is a 2020 AOM winner

Two years ago, I was in quite a quandary over what had happened to my beautiful Lyda rose blooms. While enjoying the evening in my rose garden, I came across a most disturbing situation. The stamens on the Lyda rose blooms were gone… there was a lone bumble bee trying to find some nutrients on the rose and alas, my roses were not going to provide much of a meal this evening. This destruction of the pollen source was a major catastrophe for the many beneficial insects and pollinators that depend on this for their survival. I had never seen this problem before and couldn’t figure out what had happened to the stamens?

The stamen is the pollen producing part of a flower. The stamen is composed of a long filament the supports the anther which is the part of the stamen where the pollen is produced.

The species of the rose determines the total number of stamens. No rose has fewer than five stamens and many have far more. Stamens are usually found in multiples of five. Take a walk in your garden and dissect a few blossoms to discover the wonder of nature.

The next morning, I ventured out in the garden to solve this mystery and find out what was devouring the stamens and all the pollen for the pollinators. Much to my chagrin… there were many small green bugs with black spots.

After researching this new bug that had found my garden, I found out that it was the Western spotted cucumber beetle ( Diabrotica undecimpunctata). Not one but too many to count!!!

I got a plastic cup and filled it with about 1.5 inches of rubbing alcohol and began knocking the little critters into the cup. Ten minutes later, there were too many to even comprehend. Yikes!!! No wonder the stamens were nowhere to be found… My garden had been invaded by these beetles, a new and different challenge for the garden, not the predictable gophers, voles and moles that call my garden “home”.

For the next few days I checked all 100 roses for any sightings of the cucumber beetles.

Now that I have experienced what havoc these nuisance pests can cause, I carefully check the roses and remove any uninvited cucumber beetles from my garden. It is the end of June and I have found only15 beetles in the rose garden this year. A major change from two years ago. So far, they have stayed away from my cucumbers and squash patch too!

In researching the Diabrotica undecimpunctata, I learned that the Western Spotted Cucumber Beetles are found throughout California. They are a serious pest to agricultural food crops. Adult and larval stages can also transmit bacterial wilt and mosaic virus in cucurbits. Cucumber beetles overwinter as adults and lay their eggs in the soil. In the Spring, after hatching, the larvae will remain in the soil for two to four weeks before pupating in the soil. They feed on the roots and tunnel through stems that are located under the soil. They go through three instars to reach maturity. Pupation lasts four to ten days and then the adults (the beetles) emerge to feed, mate and lay eggs. There can be three generations a year in California. It takes approximately six to nine weeks to complete one life cycle.

The adult beetle eats a variety of plants including cucurbits, legumes, corn and grasses. The adults prefer the succulent, tender portions of plants including the flowers and leaves. The rose stamens will provide the perfect delicacy to their diet!

Observe your plants early in the day and remove any cucumber beetles you see. Cucumber beetles like moisture and dislike heat. Be sure to check under blossoms and leaves. I have found that handpicking these pests and depending on the many beneficials that visit my garden brought these pests under control in one season.

Encourage beneficials in your garden which can attack the adult beetle, eggs and larvae on plants or on the soil surface. Tachinid flies, ladybugs, green lacewings, soldier beetles, birds and bats and are just a few of the many beneficials that can keep the pests in your garden under control.

Remember to remove any leaves and other garden debris to reduce the beetle’s possible overwintering sites.