It is the time of year you have all been waiting for, that is, dealing with that “infamous” of insect pests known as the bagworm. Throughout Kansas, bagworm eggs have hatched and the young caterpillars are out-and-about feeding on both broadleaf and evergreen trees and shrubs. Bagworms were first considered a pest of conifers but over the years they have expanded their host range to include a number of broadleaf plants, including: rose, honeylocust, and flowering plum.
Most calls on how to control bagworms come in during late-July to early-August when damage appears. Bagworms are difficult to control when they are that large. They are much easier to kill while small.
Bagworms overwinter as eggs inside the dead female’s bag. Young larvae normally hatch and emerge during mid- to late-May in Kansas. Now would be a good time to scout for bagworms. Wait to use control measures until mid-June as earlier sprays may miss those who emerge from the bag later than normal.
The key to dealing with bagworms when using insecticides is to apply early and frequently enough in order to kill the highly susceptible young caterpillars that are feeding aggressively on plant foliage. Older caterpillars that develop later in the season, in the bags are typically more difficult to kill with insecticides. In addition, females feed less as they prepare for reproduction; thus, reducing their susceptibility to spray applications and any residues.
However, make sure the bagworms are present by looking for a miniature version of the mature bagworm. Also, check to be sure the bagworms are alive before spraying. Predators and parasites can sometimes naturally control this pest.
Insecticides commonly used for controlling bagworms include: acephate (Orthene); permethrin (38 Plus Turf, Termite & Ornamental Insect Spray; Eight Vegetable, Fruit & Flower Concentrate; Garden and Farm Insect Control); bifenthrin (Bug Blaster II, Bug-B-Gon Max Lawn and Garden Insect Killer); lambda-cyhalothrin (Spectracide Triazicide, Bonide Caterpillar Killer); spinosad (Conserve; Natural Guard Spinosad; and Captain Jack’s Dead Bug Brew).
Spinosad is an organic control that is very effective on this pest. Thorough spray coverage of foliage is essential for good control with any of these products.
Alicia Boor is the Agriculture and Natural Resources agent with K-State Research and Extension – Cottonwood District. Contact her by email at aboor@ksu.edu or call 620-793-1910.
