The Colorado potato beetle is one of the most dangerous pests of potatoes. It is hardy and quickly becomes insecticide resistant. Russian scientists have studied bacteria that produce a specific toxin, on the basis of which biological products are created to protect plants from pests. It turned out that the addition of spores (dormant forms) of a microorganism to the insecticide destroys the intestinal immunity of the Colorado potato beetle larvae and makes them more susceptible to the toxin. This work was supported by the Russian Science Foundation (RSF) and published in the journal Toxins.
Bacillus thuringiensis (BT) bacteria produce a specific Cry toxin that affects only pests. The substance begins to work only after interacting with the intestinal enzymes of the beetle, disrupting the work of its digestive system and causing starvation.
The pest would have died out long ago, if not for its adaptation mechanisms to BT-based drugs. Intestinal immunity improves, and as a result, bacteria and their toxins cannot fulfill their intended purpose. Researchers at the Novosibirsk State Agrarian University (Novosibirsk) and the Siberian Federal Scientific Center of Agrobiotechnology of the Russian Academy of Sciences (Krasnoobsk) have figured out how to bypass these mechanisms. The combination of protein toxins with spores (a dormant form of bacteria that can activate and multiply inside insects) of Bacillus thuringiensis helps to kill the Colorado potato beetle more effectively.
When a mixture of spores and bacterial toxins enters the body, insects start a system of destruction and neutralization of various toxic substances (detoxification). At the same time, humoral immunity is activated in the intestine, which protects the body from pathogens. However, the researchers found one more feature - when the toxins are combined with spores, the larvae exhibit a strong redox imbalance and the process of damage to intestinal cells as a result of oxidation is triggered. Taken together, this leads to a violation of the antioxidant defense of the larvae and a deterioration in their general health.
“When the toxins are combined with the spores of the bacteria Bacillus thuringiensis, insects die faster, and 30% more Colorado beetles die. The introduction of the developed drugs and technologies will allow filling the market of biorational insecticides with domestic drugs, improving the quality of food products, reducing the pesticide load on the environment and reducing the negative impact on public health, ”said Ivan Dubovsky, the project manager for a grant from the Russian Science Foundation, Doctor of Biological Sciences, Head of the Laboratory biological plant protection and biotechnology of the Novosibirsk State Agrarian University.