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.
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.
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
|Brand Name||EPA Number||Pesticide Type||Active 1||Percent|
|Agree WG||70051-47||Insecticide||Bacillus Thuringiensis Ssp. Aizawai||50|
|Beetlejus! For Ornamental and Vegetable Pests||88347-3-56872||Insecticide||Bacillus Thuringiensis Ssp. Galleriae||76.5|
|Bt Bacillus Thuringiensis Ready-to-Use||70051-113-4||Insecticide||Bacillus Thuringiensis Ssp. Kurstaki||9.83|
|Crymax Bioinsecticide||70051-86||Insecticide||Bacillus Thuringiensis Ssp. Kurstaki||40|
|Deliver Biological Insecticide||70051-69||Insecticide||Bacillus Thuringiensis Ssp. Kurstaki||85|
|Dipel DF Biological Insecticide Dry Flowable||73049-39||Insecticide||Bacillus Thuringiensis Ssp. Kurstaki||54|
|Dipel Pro DF Biological Insecticide Dry Flowable||73049-39||Insecticide||Bacillus Thuringiensis Ssp. Kurstaki||54|
|Gnatrol WDG Biological Larvicide||73049-56||Insecticide||Bacillus Thuringiensis Ssp. Israelensis||37.4|
|Javelin WG Biological Insecticide||70051-66||Insecticide||Bacillus Thuringiensis Ssp. Kurstaki||85|
|Leprotec||89046-12-88847||Insecticide||Bacillus Thuringiensis Ssp. Kurstaki||14.49|
|Monterey B.T.||70051-106-54705||Insecticide||Bacillus Thuringiensis Ssp. Kurstaki||98.35|
|Monterey B.T. RTU Ready-to-Use||70051-113-54705||Insecticide||Bacillus Thuringiensis Ssp. Kurstaki||9.83|
|Mosquito Bits Quick Kill||6218-73||Insecticide||Bacillus Thuringiensis Ssp. Israelensis||2.86|
|Safer Brand Caterpillar Killer for Trees Shrubs and Vegetables Concentrate II||70051-106-42697||Insecticide||Bacillus Thuringiensis Ssp. Kurstaki||98.35|
|Summit B.T.I. Granules||6218-86||Insecticide||Bacillus Thuringiensis Ssp. Israelensis||2.86|
|Summit Biological Caterpillar & Webworm Control||70051-106-6218||Insecticide||Bacillus Thuringiensis Ssp. Kurstaki||98.35|
|Thuricide Bt Caterpillar Control||70051-106-829||Insecticide||Bacillus Thuringiensis Ssp. Kurstaki||98.35|
|Thuricide N/G||70051-53-59807||Insecticide||Bacillus Thuringiensis Ssp. Kurstaki||70|
|XenTari Biological Insecticide Dry Flowable||73049-40||Insecticide||Bacillus Thuringiensis Ssp. Aizawai||54|