Questions About Biological Worm Spray (Bacillus thuringiensis var. kurstaki)

I get many questions regarding the use of biological caterpillar (worm) spray. There are many misconceptions about how this valuable tool is used. Let’s clear the air! Bacillus thuringiensis var. kurstaki or Bt was discovered back in 1901. The name of the bacteria was given in 1911. I’ll not bore you with the rest of the history.

Suffice it to say, due to the use of synthetic pesticides, many were concerned about the toxicity and environmental issues. Fast forward to the 1980s. Bt became essential as an alternative to toxic pesticides. The effectiveness of Bt is remarkable to say the least. The bacteria with its crystalline toxins attack the gut of caterpillars and destroy the creature from within. When used on a frequent basis, it is almost 100% effective. It is totally safe for humans, pets, birds, fish, pollinators and beneficial insects. Bt may be sprayed up until the time of harvest!! Bt is no longer viable or effective after continued exposure to ultra-violet light and water.

The greatest misconception involves the insertion of the Bt genetic material into the seed germ. The Bt GMO* ready corn or potatoes has Bt as an internal mechanism to kill caterpillars. The agri-business companies use other genetic materials (from other bacteria and viruses) to potentiate the Bt gene. This really is scary stuff!!!

The externally sprayed Bt material is completely safe. It is not systemically part of the plant. Whereas, a Bt GMO* ready crop has the insecticide in all parts of the plant. This GMO creation was made for convenience and to save money. No one can say for sure what are the long term effects!!!

I started using Bt in 1978. Up until that time, my broccoli plants were full of caterpillars. I remember being served some broccoli, only to find dead worms on my plate. Ugh, nasty! Once I used Bt, there were no more worms!!! It really does work!! Plus, it is very cost effective and safe to the environment.

*GMO – Genetically Modified Organism – “A GMO is a plant or animal that has been genetically modified through the addition of a small amount of genetic material from other organisms through molecular techniques. Currently, the GMOs on the market today have been given genetic traits to provide protection from pests, tolerance to pesticides, or improve its quality. Examples of GMO field crops include Bt-potatoes, Bt-corn, Bt-sweet corn, Roundup Ready soybeans, Roundup Ready Corn, and Liberty Link corn.” University of Kentucky Entomology


6 thoughts on “Questions About Biological Worm Spray (Bacillus thuringiensis var. kurstaki)

    1. Kelly,
      Purchase on-line as Dipel Pro DF or a garden center/ professional garden supply in your area. This product is available in a one pound bag. Please follow the label.
      Thank you for visiting Papa’s Gardens. Please share with your gardening friends.


    1. Thank you for visiting Papa’s Gardens and adding us to your blogroll. We will be adding new posts as the heat is keeping us restrained from gardening.


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