Controlling Budworms on Geraniums and Petunias
By Bob Chapman
Geraniums, petunias, corn and other plants are often attacked by the tobacco budworm. They make your geraniums and petunias their personal restaurant. These worms are the larvas of a brown moth. They are very destructive and you need to understand the life cycle and habits in order to eradicate them.
Life cycle of the budworm.
The budworm pupates in the soil in winter, burying itself 6-12 inches deep. The dull-colored moth emerges in April-May, flying at dusk. After mating, the female lays eggs on your petunias, geraniums or corn, usually one to a bud, cornsilk or flower. The greenish, translucent eggs hatch in 2 to 10 days into tiny worms hardly big enough to see. They quickly enter the bud or flower. At maturity they can be anywhere from a half-inch to two inches in length. The mature worm drops to the ground, burrows into the soil and then pupates for three weeks. Following pupation, it emerges as a moth. There can be as many as seven cycles per year, especially during hot summers. Thus gardeners have to be on the alert all summer to avert disaster.
Sneaky rascals.
These worms are clever, hiding in the daytime from prying eyes and hungry birds. They prize the buds and blooms of geraniums, petunias and the Flowering Maple (Abutilon). When there are no more buds to eat, the worms will start eating the leaves. They prefer the young, tender petunia blossoms and, as on the geraniums, will start eating the leaves when the blossoms are gone.
First sign of infestation.
- Geraniums. Often the first sign of an invasion of the worms is when the geranium bud fails to open all of its flowers. Instead of a full display you will see just a part of the cluster open, the rest are missing or withered in appearance. With geraniums they have the habit of boring into the side of a bud and eating out the middle of the flower bud, leaving a characteristic hollow shell. They have the ability to change color to match the material they are feeding on. Thus if they eat red geranium buds the worm will have a reddish cast to it.
- Petunias. The first sign of an invasion of your petunias is a small hole in the middle of the blossom. And very soon all the blossom is eaten and your petunias have the appearance of having no blooms at all. They are voracious eaters. They eat almost constantly when they get to the size that you can see them.
Additional sign to look for.
In addition to the sudden failure to bloom and the holes in the buds or leaves, look for the brown or black pellet like droppings of the worm on the leaves. This is a sign that the budworm is present on your geraniums or petunias.
Controlling the budworms.
You can control the budworm by spreading granules of Easy Gone Systemic Rose and Flower Care around the desired plants for six weeks of protection from the voracious budworm.
If you prefer a natural method, spray the geraniums or petunias thoroughly with Bt,(Bacillus thuringiensis), a bacteria that attacks the worm. As soon as the worm eats the flower, leaf or bud sprayed with Bt it stops eating, but it takes a few days for it to die. Be aware that Bt has little residual effect and must be used frequently and regularly to control the worms. You have to keep a sharp eye for the young worms and spray the plant immediately.
Bob Chapman is a well-known professional gardener and landscape contractor. Currently retired, Bob now spends his time contributing many free-lance garden articles and columns, and is a much sought after lecturer and horticultural consultant.
Since 1987, Bob has appeared as a regular columnist for the San Jose Mercury News. Besides the Mercury, his writings have appeared in the San Diego Tribune, Sacramento Bee, Fresno Bee and the Times Newspaper Group. He is the 1991 winner of the Quill and Trowel Award of the Garden Writers Association of America for the best newspaper gardening article in North America.
Bob majored in Ornamental Horticulture at Cal-Poly, San Luis Obispo. He also served as a member of the Professional Gardeners Association.