Major insects affected included tent caterpillars, gypsy moth, jack pine and spruce budworms. In addition, bagworm, spanworm, red-humped caterpillar, cankerworms, and saddled prominent can be controlled with Bt. It does not control sawfly larvae, bees, grubs, maggots, or any adult insects. Application rates vary for different Bt formulations and the target caterpillar, but are normally between 8 and 24 BIU's per acre. In some spray programs, a single application of 24 BIU has been as effective as 2 applications of 12 BIU's.
Most formulations also list recommended application rates in ounces or pounds per acre.
Bt formulations can be applied to foliage in much the same way as synthetic pesticides are applied. Water-based flowable formulations of Bt have recently gained wide acceptance in forest spray programs. ULV applications are more efficient since the aircraft spends more time spraying the product and less time spraying water. Timing of the application and good coverage of the foliage is essential. Bt should be applied to dry foliage and have a droplet size of 75-150 microns.