Semiochemicals come under biochemical pesticides which include insect
attractants, repellents, sex pheromones and kairomones. Semiochemicals are chemical signals produced by one organism usually by insects which results in behavioural
change in an individual of the same or different species. The most widely used
commercially available semiochemicals are insect sex pheromones. Sex pheromones
are very successful to control adults by causing mating disruption. Mass trapping
using sex pheromones to manage flying insects especially lepidopterans and
coleopterans are very useful in IPM programs.
11.4 Biopesticides Derived from Bacteria
Bacterial pesticides are broadly classified into three categories
1. Obligate pathogens: These pathogens require special conditions and media for
growth reproduction and sporulation. They have a very narrow host and most of
them are spore formers. They are ideal for biological pest control programs. They
have good stability. For example: Bacillus papillae and B. lentimorbus cause
milky disease in white grub populations.
2. Facultative pathogens: Facultative pathogens do not require special conditions
for growth, reproduction and sporulation. They are less virulent than obligate
pathogens. Two categories of facultative pathogens are crystalliferous and
non-crystalliferous. Crystalliferous bacteria produce proteinaceous crystals
responsible for its toxicity. These are mostly spore formers. They have a wide
host range. The bacterium B. thuringiensis berliner is a crystalliferous spore
former commercially exploited as the biocontrol agent.
3. Potential pathogens: Potential pathogens can easily be cultured on artificial
media and have a wide host range. It can infect insects even at small doses
(<10,000 cells) and has a broad host range, e.g. Pseudomonas aeruginosa and
Serratia marcescens used against root-knot nematodes and Phyllophaga
blanchardi used against coleopteran pests. The non-invasive and non-spore
forming nature of these pathogens limits them as promising biocontrol agents.
Microbial biopesticides from bacteria successfully used in mass multiplication
are Bacillus popilliae, B. thuringiensis, Clostridium bifermentans, Pseudomonas
alcaligenes, Pseudomonas aureofaciens, Saccharopolyspora spinosa, Serratia
entomophila and Streptomyces avermitilis. B. thuringiensis and Bacillus sphaericus
are harmful to lepidopterans, dipterans, coleopterans and hymenopteran pests. The
insecticidal properties of this bacterium lie during the spore formation phase. During
sporulation, Bt produces specific crystal protein (Cry I-IV and Cyt) which is harmful
to the target pests. Table 11.1 enlists the B. thuringiensis subspecies and its toxin
used against various pests. The B. thuringiensis based pesticides commercially
available to control various pests (Gelernter and Schwab 1993) are presented in
Table 11.2.
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attractants, repellents, sex pheromones and kairomones. Semiochemicals are chemical signals produced by one organism usually by insects which results in behavioural
change in an individual of the same or different species. The most widely used
commercially available semiochemicals are insect sex pheromones. Sex pheromones
are very successful to control adults by causing mating disruption. Mass trapping
using sex pheromones to manage flying insects especially lepidopterans and
coleopterans are very useful in IPM programs.
11.4 Biopesticides Derived from Bacteria
Bacterial pesticides are broadly classified into three categories
1. Obligate pathogens: These pathogens require special conditions and media for
growth reproduction and sporulation. They have a very narrow host and most of
them are spore formers. They are ideal for biological pest control programs. They
have good stability. For example: Bacillus papillae and B. lentimorbus cause
milky disease in white grub populations.
2. Facultative pathogens: Facultative pathogens do not require special conditions
for growth, reproduction and sporulation. They are less virulent than obligate
pathogens. Two categories of facultative pathogens are crystalliferous and
non-crystalliferous. Crystalliferous bacteria produce proteinaceous crystals
responsible for its toxicity. These are mostly spore formers. They have a wide
host range. The bacterium B. thuringiensis berliner is a crystalliferous spore
former commercially exploited as the biocontrol agent.
3. Potential pathogens: Potential pathogens can easily be cultured on artificial
media and have a wide host range. It can infect insects even at small doses
(<10,000 cells) and has a broad host range, e.g. Pseudomonas aeruginosa and
Serratia marcescens used against root-knot nematodes and Phyllophaga
blanchardi used against coleopteran pests. The non-invasive and non-spore
forming nature of these pathogens limits them as promising biocontrol agents.
Microbial biopesticides from bacteria successfully used in mass multiplication
are Bacillus popilliae, B. thuringiensis, Clostridium bifermentans, Pseudomonas
alcaligenes, Pseudomonas aureofaciens, Saccharopolyspora spinosa, Serratia
entomophila and Streptomyces avermitilis. B. thuringiensis and Bacillus sphaericus
are harmful to lepidopterans, dipterans, coleopterans and hymenopteran pests. The
insecticidal properties of this bacterium lie during the spore formation phase. During
sporulation, Bt produces specific crystal protein (Cry I-IV and Cyt) which is harmful
to the target pests. Table 11.1 enlists the B. thuringiensis subspecies and its toxin
used against various pests. The B. thuringiensis based pesticides commercially
available to control various pests (Gelernter and Schwab 1993) are presented in
Table 11.2.
242
M. Rajamani and A. Negi