Horticulture: Still early to treat bagworms
Many bagworms have hatched and come out of the mother’s bag but we are still a bit early to treat, as we may miss those that are late to emerge. Early June is a good target to treat for these insects. However, make sure you have living bagworms, as sometimes natural predators and parasites provide good levels of control. Look for a miniature version of the mature bagworm. They are still tiny and are about the size of the lead point on a pencil.
Insecticides commonly used for controlling bagworms include spinosad (Conserve; Fertilome Borer, Bagworm, Leafminer & Tent Caterpillar Spray; Captain Jack’s Dead Bug Brew, Bonide Caterpillar Killer), Bacillus thuringiensis (Dipel, Thuricide), acephate (Acephate, Orthene, Bonide Systemic Insect Control), cyfluthrin (Tempo, Bayer Vegetable & Garden Insect Spray) and permethrin (numerous trade names).
Products containing Bacillus thuringiensis (BT) are only effective when used against bagworm larvae while they are still small. Note that spinosad and BT are both organic but spinosad is a more effective product, especially on larger larvae.
Thorough coverage is vital for good control. Most failures are due to the spray not penetrating deep enough in the tree rather than the insecticide not working.
This is the time of year we normally start seeing damage from cabbage worms. The imported cabbage worm is usually the first cabbage worm species to appear and is a fuzzy, elongated green worm. Larvae come from eggs laid by the white butterfly often seen flitting around the plants.
Early control is essential to reduce injury. BT (Bacillus thuringiensis) and spinosad (Borer, Bagworm, Leafminer and Tent Caterpillar Spray;
Captain Jack’s Dead Bug Brew) are effective organic products that are labeled for this pest. BT can be found in Dipel, Thuricide and other similar materials. Direct sunlight deactivates BT quickly so it is helpful to spray late in the day or on a cloudy day.
Conventional insecticides such as carbaryl (Sevin), malathion and methoxychlor are also effective but will kill natural enemies of these pests. Be sure to hit the underside of leaves where insects feed. Note that hitting the underside of leaves is easier when using a dust applied with a duster than when using a liquid spray.