Target Caterpillars With B.t.

It’s an easy decision to buy non-toxic  insect control products for the garden nowadays.  Even big box stores now carry neem oil, pyrethrin, insecticidal soaps, and other plant based  pest control products. While it’s true that these are a much safer choice than synthetic insect killers, these products can suppress such a wide range of insects – both good and bad – that they may not always solve the pest problem in your garden.  Sometimes if natural insect predators are killed alongside the target pests, the target pest can actually resurge and reestablish itself before its enemy can do the same, starting an entirely new pest problem.

The initial pest problem may be resolved but there could be a new one in its place. Bt is a nice option because it targets only pest insects, leaving natural enemies unharmed.

Bacillus thuringiensis (Bt) is a natural microbial pesticide that has the ability to target specific insect pests while leaving beneficial insect predators unharmed. The most commonly commercially sold form of b.t. targets primarily caterpillars, including tomato hornworm, cabbage looper, imported cabbageworm, tent caterpillars, and the diamondback moth. 

B.t. pest control products sold in stores are formulations of naturally occurring microbial organisms taken directly from the wild, and have not been genetically altered by humans. 

The Bt microbe contains two parts: an active spore and a thick-walled storage spore that includes a toxic protein crystal. When Bt is ingested by a larval insect, the walls of the storage spore dissolve, which releases the toxic crystal, destroying the gut wall of the insect, and permitting the active spore to pass into the blood stream, where it multiplies, killing the insect from blood poisoning.

Because B.t. is a stomach poison that must be eaten by the target pest, timing of application is critical. For best results, it should be applied between the time the eggs hatch and the full grown caterpillars move off of the leaves to pupation sites.

Because many caterpillar species hatch and feed on the underside of leaves in their initial stages of growth, it’s crucial to apply the B.t. spray solution to the undersides as well as the tops of plant leaves and stems. Larger caterpillars, of course, eat through both sides of the leaf, so it’s not as difficult to ensure they ingest the poison.  As with most organic pest control products, reapplication aver few days will improve results, and remember that it’s impossible to kill every single insect pest in your garden. It’s actually helpful to leave a few pest insects alive in order to help sustain the population of natural enemy insects.

Always follow the product’s directions carefully, and remember that because B.t. is a living organism, it’s best to mix the solution using purified water or harvested rainwater. Chlorinated and/or hard water can harm the microbes, severely hindering the effectiveness of the product if not rendering it totally useless.