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Caterpillars have emerged as a significant pest of industrial hemp, Cannabis sativa, in Alabama this first growing season. While we have found multiple caterpillar species on hemp throughout the season, the primary pest causing damage this late is the corn earworm, Helicoverpa zea. The majority of corn throughout the state has begun to dry or is harvested so hemp provides an attractive alternative for adult moths looking to lay eggs.

Corn earworm in hemp flower

The larval form of the corn earworm moth is the damaging life stage. We did see stem and leaf feeding earlier in the season, but currently, larval feeding on the flower buds is causing the most damage. In addition to yield loss, the wounds caused by feeding make the plant vulnerable to bud rot. This further reduces the quality and yield of the plant. This makes hemp grown for CBD oil especially susceptible to corn earworm damage.

Chemical Control

Alabama Department of Agriculture and Industries (ADAI) recently approved several products for pest control in hemp (Table 1). While these are now legal to apply, it is important to keep in mind that caterpillars are best controlled when they are small. Most pesticides will have little to no effect on bigger caterpillars. Chemical control should be used as a last resort, as proper fertility, irrigation, and sanitation should all be prioritized over pesticides. Please see Pesticide Use in Hemp from Alabama Extension for more information.

 

Table 1: Approved Products for Pest Control in Hemp

Current as of September 24, 2019
Brand NameEPA NumberPesticide TypeActive 1Percent
Agree WG70051-47InsecticideBacillus Thuringiensis Ssp. Aizawai50
Beetlejus! For Ornamental and Vegetable Pests88347-3-56872InsecticideBacillus Thuringiensis Ssp. Galleriae76.5
Bt Bacillus Thuringiensis Ready-to-Use70051-113-4InsecticideBacillus Thuringiensis Ssp. Kurstaki9.83
Crymax Bioinsecticide 70051-86InsecticideBacillus Thuringiensis Ssp. Kurstaki40
Deliver Biological Insecticide 70051-69InsecticideBacillus Thuringiensis Ssp. Kurstaki85
Dipel DF Biological Insecticide Dry Flowable73049-39InsecticideBacillus Thuringiensis Ssp. Kurstaki54
Dipel Pro DF Biological Insecticide Dry Flowable73049-39InsecticideBacillus Thuringiensis Ssp. Kurstaki54
Gnatrol WDG Biological Larvicide 73049-56InsecticideBacillus Thuringiensis Ssp. Israelensis 37.4
Javelin WG Biological Insecticide70051-66InsecticideBacillus Thuringiensis Ssp. Kurstaki85
Leprotec89046-12-88847InsecticideBacillus Thuringiensis Ssp. Kurstaki14.49
Monterey B.T.70051-106-54705InsecticideBacillus Thuringiensis Ssp. Kurstaki98.35
Monterey B.T. RTU Ready-to-Use70051-113-54705InsecticideBacillus Thuringiensis Ssp. Kurstaki9.83
Mosquito Bits Quick Kill6218-73InsecticideBacillus Thuringiensis Ssp. Israelensis 2.86
Safer Brand Caterpillar Killer for Trees Shrubs and Vegetables Concentrate II70051-106-42697InsecticideBacillus Thuringiensis Ssp. Kurstaki98.35
Summit B.T.I. Granules 6218-86InsecticideBacillus Thuringiensis Ssp. Israelensis 2.86
Summit Biological Caterpillar & Webworm Control 70051-106-6218InsecticideBacillus Thuringiensis Ssp. Kurstaki98.35
Thuricide Bt Caterpillar Control 70051-106-829InsecticideBacillus Thuringiensis Ssp. Kurstaki98.35
Thuricide N/G70051-53-59807InsecticideBacillus Thuringiensis Ssp. Kurstaki70
XenTari Biological Insecticide Dry Flowable 73049-40InsecticideBacillus Thuringiensis Ssp. Aizawai54
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