Q. Why is my PCA recommending that we use a soft control program for PTB this year?
A. Dormant sprays will most likely kill any beneficial predators of PTB present in your orchard. Soft pesticides, such as the Bts, are not harmful to bees and other beneficial insects. The mode of action of Bt makes it efficacious against lepidopteran insects with an alkaline midgut. Therefore, Bt cannot harm bees, wasps and other beneficials, or humans and other mammals, since their guts are acid, not alkaline. Your PCA is wanting to preserve beneficial predators so they can help control PTB.
Q. How can I tell if natural enemies are at work in my orchard?
A. Good question. Signs that beneficials have parasitized PTB can be seen when you are scouting their hibernacula. Larva can be found with only the head capsule remaining. The larvae may be found dead with their bodies shriveled. Or you may find the hibernaculum empty. These are all signs of natural control.
Obviously, beneficial predators can only happen in orchards using soft pesticide programs. So start soft with your PTB management programs to ensure the safety of beneficial insects.
Q. Which Bt product should I use?
A. Bt larvicides are made up of a variety of Cry toxins. These Cry toxins are microscopic crystals that are ingested by PTB larvae. In the larval stomach, the Cry crystals are broken down, releasing the toxin and killing the larvae. The Cry 1AC toxin is the most effective Cry toxin against tree and vine pests, such as PTB and OBLR.
Deliver® Bt contains the highest concentration of Cry 1AC toxin on the market, so I recommend its use in your PTB control program.