Now is the time to be preventatively spraying your crop for caterpillars. A great product that is naturally occurring and available in OMRI formulations is Bacillus thuringiensis.
Bacillus thuringiensis is a naturally occurring biological broad-spectrum caterpillar control, applied for the prevention and disruption of certain lepidopteran pest's life cycles. A endotoxic crystalline protein is created by the Bt bacterium inside the digestive system that paralyzes the digestive tract.
During the summer months, lepidoptera species such as gypsy moths, cabbage loopers, tomato hornworms, and grape leaf skeletonizers eggs begin to hatch. Their larvae and pupa stage begin heavy consumption of leaf and fruiting material. Using an integrated pest management system that includes timely applications of this biological insecticide will reduce the amount of harm these pests will have on your crop during the flowering stage. This includes a 4-8 week regiment of weekly foliar applications, starting in July. Excrement from these pests can begin to rot in the interior of the flowering hemp buds that can then begin to mold causing negative fungal and bacteria affects to your crop. These species of caterpillars are extremely pervasive during this time of year.
Another benefit to using certain Bt strains is that it is non-toxic to pollinators and other beneficial insects. In combination with pyrethroid insecticides prior to flower formation will also increase the efficacy of this application against pests. We often suggest using beneficial insects prior to any observable pest pressures. Understanding the life-cycles of both pests and beneficials will help determine the best times to apply insecticides that heighten the beneficial insect populations and deter pests populations.
For further reading, check out Cornell University research on B.t.