20 Questions
Biological control of harmful organisms is an environmentally safe alternative to chemical effects on ecosystems
True
The orientation of plant protection has changed significantly in the direction of biologization and ecologization
True
The number of biological insecticides and acaricides allowed for use has increased significantly in recent years
False
Entomopathogenic bacteria, viruses, fungi, nematodes, microbial toxins and regulators of growth, development and behavior of insects comprise about 20% of the active substances for creating biological preparations
True
Research in the field of biopesticides is now an extensive interdisciplinary field of science
True
Hydrolyzed toxins in insect midgut cause an increase in water permeability and cell membrane rupture.
True
Crystalline endotoxin produced by Bacillus thuringiensis (BT) is toxic only to a specific group of insects due to the pH conditions of mammalian digestive system.
True
BT produces a variety of insecticidal delta-endotoxin proteins, identified as Cry genes, and cytolytic Crt proteins.
True
Exotoxin inhibits DNA-dependent RNA polymerase and can penetrate the insect's integuments.
True
BT insecticides have been used for decades and are considered safe for the environment and non-resistant to insects.
True
Entomopathogens are not used in biological preparations against plant pests
False
Bacillus thuringiensis is a gram-negative bacterium
False
BT varieties are not effective against phytophages
False
The first commercial BT insecticide was produced in the U.S. in 1958
False
BT-based drugs are not safe for humans, warm-blooded animals, and the environment
False
BT-based drugs are most effective at temperatures below 17-18°C.
False
The waiting period for BT-based drugs in organic farming is 5 days.
True
The introduction of BT cry genes into plants has shown to make the plants resistant to harmful insects.
True
The use of transgenic plants based on Bacillus thuringiensis is associated with a potential environmental risk of direct and indirect negative effects on the non-target biota of the agrocenosis.
True
Certain natural BT strains have been successfully incorporated into the production of bioinsecticides, where the active ingredient is a mixture of spores and crystals.
True
Study Notes
- Entomopathogens, elements of the natural biocenosis, form the basis of biological preparations against plant pests.
- Depending on the nature, bacterial, viral, fungal, and other entomopathogenic drugs are distinguished.
- Bacterial insecticides and acaricides, such as those based on Bacillus thuringiensis Berliner (BT), preserve natural biodiversity and contribute to self-regulation of biocenoses.
- Bacillus thuringiensis is a soil, gram-positive, spore-forming bacterium, famous for its protein crystalline inclusions.
- First discovered in Japan in 1901 by Shigetan Ishiwata as the cause of "sotto disease," a bacterium that caused mass death of silkworms.
- Berliner isolated a BT strain from dead mill fireworm larvae in 1911 and named it Bacillus thuringiensis.
- Over 70 BT varieties effective against phytophages have been identified, with high selectivity, safety, and antifidant, teratogenic, and reproductive properties.
- The first commercial BT insecticide, Sporine, was produced in France in 1938.
- In the former Soviet Union, the first bacterial insecticide, Entobacterin, was produced in the 1950s.
- In the U.S., commercial BT drugs were first produced in 1958.
- Advanced production and application technologies result in various BT-based drugs abroad, such as Bactospeine and DiPel.
- Complex preparation Xantrel, based on BT spore-crystal complex and Bacillus subtilis, is effective against leaf-eating pests and plant diseases.
- BT is found everywhere in nature, allowing for its use in organic farming and its safety for humans, warm-blooded animals, and the environment.
- Mechanism of action: the crystalline delta-endotoxin is insoluble in water but soluble in alkaline solutions. It enters the insect's body, degrades into a true toxin, and causes structural disorganization of the intestinal epithelium, leading to septicemia.
- Non-toxic BT virulence factors include metalloproteases, chitinases, aminopolyol antibiotics, and nucleotide fragments.
- The bacteria cause diseases that disrupt the insects' immune systems, allowing the bacteria to multiply and spread, eventually causing septicemia.
Test your knowledge on how hydrolyzed toxins disrupt insect midgut receptors and cause physiological changes, leading to cell membrane rupture. Explore the differences in toxicity between insects and mammals.
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