One of the common June and July calls we receive regards defoliation of junipers and cypress by bagworms.
A good year for bagworms is almost always a bad year for Leyland cypress and arborvitae, but bagworms attack many trees including pine, spruce, black locust, willow, sycamore, apple, maple, elm, poplar, oak, and birch. In conifers, they attack the buds, causing tips of branches to die. However extensive defoliation and death of the plant is common in extreme infestations.
Bottom line, people are always most concerned with how to kill bagworms. My stock answer is three-pronged.
• Invoke divine intervention; pray there won't be many worms this year!
• Select an appropriate insecticide and apply according to label instructions.
• Pick off and destroy all the bags you can find.
A quick overview of the bagworm life cycle is helpful in understanding their control. Depending on the weather, larvae hatch from overwintering eggs in May or early June. They spin a silken case around themselves and begin feeding, adding silk and leaves to the case or bag as they grow. When the worms are at rest, the bag is attached to a tree limb with a silk thread. When feeding, the worms pull themselves along the limb -- bag and all.
Adults are moths that emerge in late summer. However, only male moths can fly, and their business is to search out females (who remain in their bags). Males enter the bags and mate with females, who then lay 300 to 1,000 eggs in the bag prior to their death. Eggs overwinter in the bags, and larvae hatch the following spring -- which starts the whole darn mess again.
Although this spring has been cool, homeowners with previous bagworm problems should begin scouting for bagworms this month. If worms are found, the entire tree should be treated right away, while larvae are young. Young pests are almost always easier to control than old, crusty ones (perhaps comparing your grandchildren to your spouse?).
For control, I usually recommend Thuricide or a similar brand containing Bt, a natural product containing the bacteria Bacillus thuringiensis. Bt is an effective treatment for bagworms and many other caterpillar defoliators. Caterpillars eat treated leaves, then the Bt begins destroying gut tissue in a matter of hours. Synthetic insecticides effective on bagworms include Sevin and malathion and should be applied according to label instructions.
For other pest control advice, at least the home garden variety, feel free to call our office at 479-271-1060.
-- Neal Mays is an agriculture agent with the UA Cooperative Extension Service in Benton County. Contact him at [email protected]. The opinions expressed are those of the author.
Community on 05/21/2015