The label is the law. Rates and restrictions below are taken from the product labels listed under Sources. Your product's own label governs; read it before you mix or apply. Mixing calculator · Disclaimer
- Active ingredient
- Bacillus thuringiensis subsp. aizawai strain ABTS-1857 (fermentation solids, spores and insecticidal toxins)
- Chemical class
- Microbial insecticide; IRAC Group 11A, microbial disruptors of insect midgut membranes, which covers Bacillus thuringiensis strains and the insecticidal proteins they produce.[2]
- Mode of action
- IRAC Group 11A: Microbial disruptors of insect midgut membranes: Bacillus thuringiensis subsp. aizawai[2]
- Signal word
- XenTari Biological Insecticide Dry Flowable: Caution[1]
What happens after caterpillars eat it
The label says larvae stop feeding within an hour of eating a lethal dose and die within several hours to 3 days. They turn sluggish and discolored, then shrivel and blacken.[1]
There is no waiting period before harvest on the label, though it notes that individual states may set their own pre-harvest intervals.[1]
Where aizawai fits among Bt strains
IRAC lists aizawai, kurstaki, israelensis and tenebrionis together in Group 11A. It notes that Bt products aimed at different insect orders can be used together without hurting resistance management, and that rotating certain Bt products may help.[2]
Where it is used
Treat while caterpillars are young and actively feeding on exposed leaves, before the crop is damaged. Larvae must eat the deposit, so smaller worms die faster.[1]
Cover both sides of the leaves evenly. On hard-to-wet plants such as cabbage, the label suggests adding a spreader-sticker approved for growing crops.[1]
Repeat sprays every 3 to 14 days depending on plant growth, moth activity and rain. Use the higher rates and shorter intervals under heavy pressure.[1]
Don't mix more than you can use in 3 days. After chemigation, avoid irrigating the treated area for 24 to 48 hours so the spray isn't washed off.[1]
Products and registrations
| Product | Registrant | EPA Reg. No. | Active % | Formulation | Signal word |
|---|---|---|---|---|---|
| XenTari Biological Insecticide Dry Flowable[1] | Valent BioSciences LLC | 73049-40 | 54.0% | dry flowable | Caution |
Label rates
| Product | Use | Pests | Rate |
|---|---|---|---|
| XenTari Biological Insecticide Dry Flowable | Vegetables (including cabbage-family and leafy greens), fruit, nuts and field crops | Loopers, imported cabbageworm, diamondback moth, hornworms, armyworms, cutworms, Heliothis | 0.25–2 lb product per acre[1] 1/4 to 1 1/2 lb per acre for most listed caterpillars and up to 2 lb for armyworms and Heliothis. One 1 lb bag covers 4 acres at the lowest rate or half an acre at the highest. |
| XenTari Biological Insecticide Dry Flowable | Flowers, bedding plants and ornamentals | Loopers, tobacco budworm, omnivorous leafroller, diamondback moth, oleander moth, azalea caterpillar | 0.25–1.5 lb product per acre[1] Armyworms on ornamentals can take up to 2 lb per acre. Azalea caterpillar is a ground-application-only use. |
| XenTari Biological Insecticide Dry Flowable | Forest, shade and sugar maple trees and ornamentals (not California) | Gypsy (spongy) moth, bagworm, cankerworms, fall webworm, tent caterpillars, spruce budworms, tussock moths | 0.25–1 lb product per 100 gallons of water[1] For a small sprayer, that works out to 1/2 teaspoon per gallon at the low end and 2 teaspoons per gallon at the top. Mist blowers use the same pounds in 10 gallons of water. |
Safety and environmental hazards
People
Signal word CAUTION: harmful if inhaled or absorbed through the skin and causes moderate eye irritation. Handlers wear long sleeves, long pants, waterproof gloves and a particulate respirator, since repeated exposure to microbial proteins can cause allergic sensitization.[1]
Pets
Keep unprotected people out of treated areas until sprays have dried, and store the bag dry, out of sunlight and where children can't reach it.[1]
Bees and pollinators
The XenTari label carries no bee warning, but it does say the product is toxic to the green lacewing and to a predatory mite, Galendromus occidentalis.[1]
Fish and water
Toxic to aquatic invertebrates. Don't apply directly to water or where surface water is present, and keep rinse water out of streams and ponds.[1]
Common questions
- How much XenTari per gallon of water?
- The label's small-volume table gives 1/2 teaspoon per gallon for a 1/4 lb rate, up to 4 teaspoons per gallon for a 2 lb rate per acre or per 100 gallons.[1]
- Is XenTari approved for organic growing?
- Yes. The XenTari Dry Flowable label is marked for organic production.[1]
- Will Bt aizawai kill beetles or aphids?
- No. The label limits it to listed caterpillars, the larvae of moths and butterflies, and they must eat treated plant surfaces to be affected.[1]
Sources
- U.S. EPA Pesticide Product Label System, “XenTari Biological Insecticide Dry Flowable label, EPA Reg. No. 73049-40 (EPA-stamped, May 3, 2022).” www3.epa.gov/pesticides/chem_search/ppls/073049-00040-20220503.pdf (accessed 2026-10-06)
- Insecticide Resistance Action Committee, “IRAC Mode of Action Classification Scheme, Version 11.5 (Feb. 2026).” irac-online.org/documents/moa-classification/ (accessed 2026-10-06)