Have you been patiently waiting for the blossoms on your petunias and geraniums? Do you see buds that never open? If so, tobacco budworm is probably the culprit. Tobacco budworm is one of the many different caterpillars that attack desirable plants. The front wings of the adult moth have a wingspan of 1 1/2 inches, are light green, and crossed by 4 light oblique bands. The moths emerge in the spring and deposit their eggs singly on the underside of the leaves. The eggs hatch on the underside of the leaves and the tiny larvae make their way to the buds and crawl down among the unfolded leaves. The folded leaves protect the caterpillars from natural predators and from the controls we apply.
The mature larvae are 1 1/2 inches long and are generally pale green to rust in color. They pupate in the soil, and there are several generations each year.As the name implies, tobacco budworm is a serious pest of tobacco. This would cause us little concern in Utah except that it attacks many other crops. The most affected victims are petunias and geraniums, but it also attacks ageratum and nicotiana. It also breeds on and attacks some weeds, including ground cherry and related plants.
This pest has been a problem for many years. Early-day growers used a little boy/big boy team to fight the pest. The little boy placed a small handful of warm soil in the growing bud of each infested plant. This caused the budworm to leave its hiding place in the folds of the leaves. The big boy followed closely and killed the budworm before it moved out of danger. This process was labor intensive, but it still works just as well as it did before the development of insecticides.
The budworm is difficult and exasperating to control. The first step in good control is to inspect the plants prior to planting them in your garden. Look for eggs on the undersides of susceptible plants and for signs of feeding on the blossoms or the leaves.
Injury to blossoms is usually noticed when they do not appear (the worm eats them before they bloom). Research indicates the pest is difficult to control with many common insecticides. Orthene is probably one of the most successful for home gardeners, but requires repeated applications and thorough coverage. A better, organic solution in my opinion is Bacillus thuringensis or Bt, sold as Dipel or Thuricide. This product is very safe to use and provides effective control when directed against the newly hatching insects. The larger stages of the worms are seldom, if ever, killed. Start the control program when blossoms appear on transplants. Control weeds near the garden to prevent insects from using them as a breeding site.
American, Siberian and Chinese elms as well as zelkova trees are attacked by the elm leaf beetle. It was accidentally introduced in the Eastern United States about 1834. Utah was spared infestation from the pest until 1963. As is the case with many pests, it was introduced where it has no natural enemies and the beetle became a serious problem.
The adult is about 1/4 of an inch in length and yellow or olive green in color with black stripes. The adults emerge from their winter hiding places about the time the elm trees get their leaves in the spring. The prolific females lay as many as 800 yellow, lemon-shaped eggs on the underside of the leaves. The adult beetle chews holes in the leaves as they migrate from the lower to the upper branches. The larvae, by contrast, feed by scraping the underside of the leaf away and cause the leaves to dry and turn brown. The larvae feed for about three weeks, then form the pupal stage. A second generation of beetles generally appears later in the season. This pest only threatens the tree's health when the defoliation occurs year after year.
Controlling the pest is often difficult and frustrating. Chemical control depends on early detection of infestations and spraying to prevent large numbers of beetles from developing. Sprays are most effective if done on a neighborhood or community basis to prevent re-infestations from unsprayed trees. In addition to the damage done by feeding on the trees, the insects become a disagreeable household pest when they move indoors seeking shelter in the winter. Good building practices prevent entry of the pests.
Sevin, methoxychlor, or Orthene are all effective against the beetle, but most home owners lack the equipment to spray large trees. Organic controls are more difficult. Insecticidal soap is effective, providing it contacts the insect. Another control is to remove unwanted elm trees. Siberian elms, particularly, become very weedy and unwanted trees in vacant areas that often serve as breeding sites. New biological insecticides are being tested against this pest, but are not yet available for homeowners to apply.