Insect Causes for Lacking Flowers, by Jeff Rugg


Q: I have read your column and would like to add your answer to the question why the rose plant has not flowered again despite new branches. You mentioned that it could be the type of rose or the lack of fertilizer.

I had this problem in New England too and found that I had a mosquito (a tiny flying insect that you can’t really see) invading the newly forming bud. After the first blush, you suddenly see no more flowers, but if you look closely, you can see a dried or dead bud on the new branches. You will need to spray for the insect or use a systemic insect repellent. I also tried blue cups next to the plant that had been sprayed with cooking spray inside and out. This seems to work too, but the systemic stuff is better.

A: You are right. The rose mosquito is a tiny insect that most people won’t even notice. The adult is a mosquito, and the larva is a tiny larva that is only about a millimeter long. The lifespan in summer is very short, only about two weeks. The female lays eggs on the side of the bud at the end of the branch that will become the flower. The larvae eat the bud. There can be a dozen larvae in a single bud. They mostly fall out of the bud to pupate in the ground, but some can pupate in the bud as well. The last group in autumn remains dormant until the following spring.

Once the mosquitoes are in a flower bed of roses, they won’t go until the controls are used. A systemic insecticide applied early in spring and applied throughout summer is the best control. Viewing the ends of all rose branches and pruning any affected branches should be done every few days. All the branches with black leaves at the end have already had the mosquitoes that are now in the ground or have already grown out. In the fall, the top few inches of mulch or soil should be removed and replaced.

In contrast to the rose mosquito, which apparently only attacks roses, the tobacco budworm attacks many types of crops as well as ornamental flowers and vegetables. The adult is a one inch long moth that is nocturnal. It lays eggs on crops like alfalfa, cotton, soy, and tobacco. It damages chrysanthemums, gardenias, geraniums, petunias, marigolds, zinnias and many others. Cabbage, okra and tomatoes are also infected.

The caterpillar is mostly nocturnal. They prefer to eat flowers and flower buds, but they will eat leaves when there are no flowers to eat. They are striped yellow-brown with many tiny spines. There may be four or five generations per year in the south, but they are not hardy and do not survive northern winters. They are found in the northern states each summer when the moth moves with the wind.

If your plants are missing the flowers, inspect them at night to see if you can find the caterpillar. If you find them, just take them off and kill them. There are some natural parasites and wasps that infest the caterpillar, but if the infestation is severe, an insecticide containing Bacillus thuringiensis will help. It’s best to apply insecticides at dusk when the caterpillars are more active.

Email questions to Jeff Rugg at [email protected] To learn more about Jeff Rugg and to read articles by other Creators Syndicate writers and cartoonists, visit the Creators Syndicate website at