Budworm--Bad Bug

Martie Young
Adams County Master Gardener

Budworms may not rival the man-eating plant in the play "Little Shop of Horrors"; but if you grow certain annuals, you may find them just as terribly destructive. If you like growing geraniums, petunias, snapdragons, penstemon, angelonia, nicotiana and many others, you are growing flowers that budworms love to eat. The budworm is a real threat to tobacco crops, too; fortunately for tobacco farmers they have more potent pesticides and better training in using them than the ordinary gardener.

I discovered these worms (also known as the geranium/petunia budworm) last summer in my petunias. I had planted Tidal Wave Silver petunias that had nicely covered a large gardening space. Unfortunately, I soon noticed holes near the flower bases and upon inspection found the worms inside the flowers. Some researching told me I had budworms. Another hint that budworms are present are small black spots on the leaves and flowers. This is frass (or worm poop).

I tried to keep the budworms in check by spraying and squeezing them. When the worms got ahead of me and made a mess of the petunias, I pulled them out and threw them away. This year I decided to replace the petunias with snapdragons and angelonia and hoped that would put me in the clear. Both now have budworms, possibly coming along with the plants when I purchased them from the greenhouse, an interesting fact I discovered while doing some reading.

Budworms also like geraniums, and they have already appeared on my geranium buds. I must blame myself for this because now I’m learning that bringing geraniums in for the winter without changing the soil first can be to blame. But who knew? I have brought geraniums in for the winter for years and never had problems. (Budworm 2 – Geranium blossom devastated by budworms)

Apparently, the biggest factor in the increase in the budworm population is the warm winter we had last year. The insect spends the winter as a pupa about 2 to 6 inches deep in the soil within a packed earthen cell. Even in a very cold winter, the insect can live in a protected area of the soil such as next to a sun-warmed wall or foundation. If the temperature does not drop below 20 degrees, the insect will most likely live and emerge in the spring as an adult in the moth form. The moth has a wingspan of about 1 1/2 inches; the wings are light colored with brown overtones and a few wavy cream colored bands. You may see it flying up from the grass in the evening. (Budworm 1 – Notice how the budworm’s color mimics the geranium stem)

Eggs are laid singly, during early evening, on geranium buds or on leaves of other plants. The larvae that emerge are tiny worms that immediately begin to eat. At this point you may notice some problems--holes in flower buds, ragged blossoms, or no blossoms. As the worm eats, it gets bigger and more noticeable. An interesting factor here is that the worm may take on the color of the flower it is eating. So a purple angelonia will produce a purple worm, a green undeveloped geranium bud, a green worm, a white snapdragon bloom, a white worm, etc. By the way, you may have to squeeze open the snapdragon blossom to see the worm inside.

If you suspect that you have budworms, look for them in the early evening. Once you see the holes, keep looking and soon you will see the worm itself. Budworms are found all over the <?xml:namespace prefix = st1 ns = "urn:schemas-microsoft-com:office:smarttags" / US, and they can produce two or more generations a year. Hand-picking should be done in the home garden.

Tobacco budworm is resistant to most garden insecticides. In addition, using them may kill beneficial insects such as wasps, bigeye bug, damsel bugs, minute pirate bugs, and spiders. If you use an insecticide, look for one with synthetic pyrethrins also known as pyrethoid insecticides. The insecticide known as Bt may be effective on some plants. However, the insect must eat the Bt in order for it to be effective. If the worms have drilled into the bud, they are not eating the Bt. Keep weeds in check by pulling, since the weeds can also be hosts for the budworm.

Another possible remedy for getting rid of budworms would be to rototill your planting areas. Working the soil in the fall is preferable, but spring tilling may crush some of the budworm pupa.

In the fall remember to throw away the soil from potted plants and replace with new potting mixture if you are over wintering plants. Be mindful that any flowers and buds you put in your compost pile may have budworms that will over winter to continue your problem next year. And hope for a very cold winter!

For more information search for geranium/petunia budworm on the Internet and use information from educational sites such as state universities.

Read other articles about controlling insects & garden pests

Read other articles by Martie Young