25 Questions
What is the optimal temperature for the active feeding of insects and ticks mentioned in the passage?
17-18° C
When does the death of phytophages typically occur after treatment with BT drugs?
3-5 days after treatment
What is the waiting period after using BT-based drugs in organic farming?
5 days
What is the primary action of BT-based drugs on phytophages?
Lethal action
What is the main advantage of transgenic plants based on Bacillus thuringiensis compared to the technology of spraying with bacterial preparations?
Continuous production of toxins in every cell of the plant
What does the cultivation of BT plants contribute to, according to world experience?
Expanded range of hosts for toxins
What does Bacillus thuringiensis synthesize that is promising for biocontrol?
An extraordinary variety of insecticidal proteins
What is the focus of plant protection in recent decades?
Biologization and ecologization
What percentage of the total number of permitted drugs are biological insecticides and acaricides?
6.3-6.7%
What are examples of entomopathogenic preparations mentioned in the text?
Bacteria, viruses, and fungi
What is the share of entomopathogenic bacteria, viruses, fungi, nematodes, microbial toxins, and regulators of growth in terms of active substances for future preparations?
About 20%
What is the primary focus of microbiological control in ecosystems?
Microbiological control of the number of harmful organisms
How has the scientific intensity of crop production changed in recent years?
Increased moderately
What is the role of BT in insect control?
Increasing water permeability and rupturing intestinal cell membranes
What is the specific designation for the genes encoding insecticidal delta-endotoxin proteins?
cry
Which type of BT cultures have a wider spectrum of entomocidal action and are promising for drug production?
Exotoxinogenic
What makes the safety of BT and its metabolites widely accepted in plant protection practice?
Toxicological studies
Which group of entomofauna is crystalline endotoxin toxic to?
A narrow group due to low pH requirement for mammalian protein digestion
What is the mechanism by which some BT subspecies inhibit DNA-dependent RNA polymerase?
Thermally stable exotoxins
Which entomopathogen is the most commonly used in the global biopesticide market?
Bacterial insecticides (Bacillus thuringiensis Berliner)
When was the first commercial BT product introduced in the USA?
1958
What is the mechanism of action of BT determined by?
Parasporal toxins (Cry and Cyt) or soluble Vip and Sip toxins
What does crystalline delta-endotoxin have a thermolabile protein structure and is insoluble in water but soluble in alkaline solutions?
Bacillus thuringiensis Berliner (BT)
Where was the first bacterial insecticide, Entobacterin, produced?
Soviet Union
Which complex preparation is effective against leaf-eating pests and some plant diseases and has been created and used in Belarus?
Xantrel
Study Notes
- Entomopathogens, natural elements found in biocenosis, serve as basis for biological preparations against plant pests.
- Bacterial, viral, fungal and other drugs are distinguished based on the nature of entomopathogens.
- Bacterial insecticides and acaricides are derived from entomopathogenic bacilli, with Bacillus thuringiensis Berliner (BT) being the most commonly used.
- BT is a soil, gram-positive, spore-forming bacterium with approximately 90-95% share in the global biopesticide market.
- Over 70 BT varieties effective against phytophages have been identified, with high selectivity, safety for useful entomofauna, fish, and warm-blooded animals.
- First bacterial insecticide, Entobacterin, was produced in the Soviet Union in the early 1950s.
- First commercial BT products were introduced in France in 1938 and the USA in 1958.
- Bactospeine, Foray, Biobit, DiPel and others are well-known commercial products based on BT.
- Complex preparation Xantrel, effective against leaf-eating pests and some plant diseases, has been created and used in Belarus.
- BT is found in various types of soils, on plant surfaces, in leaf litter, and in insect bodies.
- BT isolates are found on different continents and in most countries worldwide.
- BT-based preparations are safe for humans and warm-blooded animals, non-target organisms, and the environment.
- Mechanism of action of BT is determined by parasporal toxins (Cry and Cyt) or soluble Vip and Sip toxins.
- Numerous non-toxic BT virulence factors, such as metalloproteases, chitinases, aminopolyol antibiotics, and fragments imitating nucleotides, affect insects differently.
- Bacteria cause diseases, leading to septicemia and the release of crystalline delta-endotoxin, which degrades under intestinal enzymes to release a true toxin.
- Crystalline delta-endotoxin has a thermolabile protein structure and varies in shape, being insoluble in water but soluble in alkaline solutions.
- Endotoxin causes pathological processes, including structural disorganization of the intestinal epithelium, permitting the bacterium's participation in the septicemia.
Learn about the mechanisms of action of hydrolyzed toxins on insect midgut receptors and the resulting physiological changes. Understand why crystalline endotoxin is toxic to insects but not to mammals.
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