| Now is the time to scour for bagworms |
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| Written by Craig Everett, OSU Program Asst./Horticulture |
| Saturday, 02 June 2012 07:28 |
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Bagworms (Thyridopteryx ephemeraeformis) have hatched in Northwest Ohio and are starting to feed. Bagworms were very numerous last year in Wood County, as well as in other areas of the state. Heavy populations were noticed on arborvitae, spruce, and some deciduous trees, mainly maple. Although stripped branches of deciduous trees releafed this year, defoliated branches of arborvitae, spruce, and other needled evergreens did not come back. The problem with common names of insects is that bagworms are often confused with other insect pests such as tent caterpillars and webworms. Bagworms build individual diamond-shaped bags of leaf tissue, which hang all over the plants, that the caterpillar lives in until pupation. Bagworms are actively feeding right now. Small grayish, black-colored worms just emerged from last year's bags. They are so small that you will not notice them without careful inspection, but they have begun to feed upon whatever leaf material is present. Unfortunately, they are usually not noticed until significant damage is done. Because young larvae migrate to the tops of trees and shrubs, look in these areas for early infestations. Do not wait to treat. You can manually pick the small bags off and kill them, but they are hard to find at this stage. When many small bagworms are present and feeding, an insecticide may be needed to prevent serious damage. The best time to apply an insecticide is while the larvae are still small (less than 1/2-inch long). Small larvae are more vulnerable to insecticides, and feeding damage is relatively minor. Carefully inspect susceptible landscape plants. Young bagworms are hard to see at first; look closely for the small, upright bags which have the appearance of tiny ice cream cones made of bits of plant material. In a few weeks the caterpillar will change from a larval (caterpillar) stage to a resting (pupa) stage. Later this year they will emerge from the pupa within the bag as either wingless, nearly legless females or furry, black, winged males. The females remain in the bag, but the males leave it behind in search of females to mate with. Females lay nearly 500 eggs per bag and then die. The bag serves as overwintering protection for the eggs that will hatch normally in June when the Northern Catalpa tree is in flower or phenologically at 816 growing degree days. Insecticides recommended for controlling bagworms include Bacillus thuringiensis kurstaki (sold as Dipel or Thuricide), cyfluthrin (Tempo), bifenthrin (Talstar), carbaryl (Sevin) and spinosad (Conserve). Insecticide sprays are effective against the young larvae but bags that are 3/4 inch long or longer are very difficult to control. The bacterium Bacillus thuringiensisi is effective on young caterpillars, but the material must be ingested - so thorough plant coverage is essential. Spinosad is very effective and works by contact and ingestion. Cyfluthrin, trichlorfon, and carbaryl are recommended for larger larvae but again thorough coverage is essential. Be sure to read and follow all pesticide label directions. |
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