Gardening Tips: Controlling Bagworms
Some insect and disease problems are so rare that when they appear it can be hard to identify the problem and its solution. Problems such as these leave us scratching our heads. Other problems are so frequent and common that we almost take for granted that they will pop up year after year. However, just because these problems tend to recur year after year does not mean that they are untreatable. Let’s look at bagworms for one example.
Bagworms are an insect pest of many trees and shrubs, including Leyland cypress, arborvitae, junipers, and wax myrtle. Bagworms hatch in May or June and begin to spin a cocoon-like bag around themselves using a silk thread. Gradually, they begin to incorporate some foliage that they have removed from the plant into their bag as a means of camouflage. As the worm grows, the bag that surrounds it grows accordingly. While a single bagworm will not harm a plant noticeably, a sever infestation can cause near complete defoliation in as little as a year or two. Additionally, bagworms occasionally cause breakage in twigs, due to the heavily wrapped layer of silk attaching the bag to the branch tips. This type of damage is called “girdling”.
In August and September, the now adult bag worms emerge from their bags and search for a mate. After mating, the female bagworm will lay its eggs back inside the bag from which it emerged. The eggs will survive overwinter inside the bags and will emerge in the spring.
Control of bagworms will differ depending on the amount of bagworms present in a given area. The bags are simple to remove by hand or with scissors or pruners, and if there are only a few present, this is the best management strategy. After removal, the bags can simply be crushed or sealed inside a garbage bag. In order to interrupt the life cycle of the pest, removing the bags from the plant is important, because even after the adults have emerged from the bags, they are likely filled with eggs waiting to hatch the following year.
For larger infestations, removal of every bag is not always practical. In such cases, spraying a pesticide may be necessary to prevent large defoliation. To decide whether or not to spray a pesticide, you’ll have to decide how much damage you are willing to tolerate, and consider how badly damaged the plants have been in past years. Usually the amount of damage caused by bagworms does not justify use of pesticide, but of course every situation is different. Both carbaryl (Sevin)and Bacillusthuringiensis (often referred to simply as Bt, commercially available under the name Dipel, among others), can be used for control, and are most effective early in the summer when the bagworms are young. As always, follow the directions on the label of any pesticide product you use for safety and best results.
On Saturday June 24th, the Roanoke Valley Farmers Market will be celebrating Dairy Month, by hosting Dairy Day at the market. Dairy products such as cheese, ice cream, milk, and dips will be highlighted and Cooperative Extension will offer cooking classes and free food samples. The Roanoke Valley Farmers Market is open on Rt. 158 in Roanoke Rapids every Saturday from 8 to 3, and in Halifax outside the AgriculturalCenter every Wednesday form 8 to 5.
Matthew Stevens is the horticulture extension agent for HalifaxCounty Cooperative Extension. If you have any questions about this article or other aspects of your home gardening, please contact Matthew at 583-5161 or .