11.10.1 Mode of Action
The mechanism of action of herbal pesticides is either by absorption by insect
cuticle, inhalation or by ingestion thus affects the physiology, biochemical pathway
or nervous system of the insects. It affects the respiration of insects by blocking
spiracles leading to suffocation. At the cellular level, it will interfere with the signal
transduction, disturbing ion channel and ion pump of insect membrane. It also
affects the neuroendocrine system of insects and juvenile hormonal imbalance
resulting in malformation of insects. The decrease in adult mating time, reduction
in ovulation, reduced fecundity and egg fertility are other effects. Monoterpenes
present in the essential oil act as neurotoxicant which acts on the acetylcholinesterase
enzyme involved in nerve impulse transmission in insects causing paralysis and
death of the insects. It also interferes with DNA, RNA and protein synthesis
(Fig. 11.7).
11.10.2 Semiochemicals
Semiochemicals are chemical substances produced by the organisms that enable and
mediate communication between the organisms. Basically there are two types of
semiochemicals, namely intraspecific semiochemicals (pheromones) and interspecific semiochemicals (allelochemicals). Pheromones are volatile chemical
substances produced by an organism so as to elicit a reaction or response from the
receiving individual (of same species). The releaser pheromones cause behaviour
change in the recipient. The releaser pheromones include sex pheromones,
Table 11.8 List of commercially available biochemical pesticides
Plant source
Target pest
Commercial name/compounds
Azadirachta spp.,
Nicotiana spp.
Aphis craccivora, Bollworms,
Aphids, Jassids, Thrips, Whitefly,
Leaf folder, Pod borer, Fruit borer,
Leafhopper, Diamondback moth
Essential oils, nicotine,
azadirachtin, salanin, nimbin,
(leaf, seed, kernel) nimbecidin,
bionimbecidin
Chrysanthemum
cinerariaefolium
Lonchocarpus spp.
Ryania spp.
Crawling and flying insects such
as cockroaches, ants, mosquitoes,
termites
Pyrethrium, Rotenone
Ryanodine
Artemisia annua
Helicoverpa armigera
Essential oils from leaf and
seed
Vinca rosea
Helicoverpa armigera
Essential oils from leaf and
seed
Ocimum basilicum
Salvia Officinalis
Aphis craccivora Koch, Agrotis
ipsilon
Essential oils form aerial parts
leaves
Citrus sp.
Fleas, aphids, mites, paper wasp,
house cricket
D-limonene linalool
Schoenocaulonofficinale Bugs, blister beetles fly,
caterpillars, potato leafhopper
Sabadilla dust
Adenium obesum
Cotton pests
Chacals Baobab (Senegal)
258
M. Rajamani and A. Negi
The mechanism of action of herbal pesticides is either by absorption by insect
cuticle, inhalation or by ingestion thus affects the physiology, biochemical pathway
or nervous system of the insects. It affects the respiration of insects by blocking
spiracles leading to suffocation. At the cellular level, it will interfere with the signal
transduction, disturbing ion channel and ion pump of insect membrane. It also
affects the neuroendocrine system of insects and juvenile hormonal imbalance
resulting in malformation of insects. The decrease in adult mating time, reduction
in ovulation, reduced fecundity and egg fertility are other effects. Monoterpenes
present in the essential oil act as neurotoxicant which acts on the acetylcholinesterase
enzyme involved in nerve impulse transmission in insects causing paralysis and
death of the insects. It also interferes with DNA, RNA and protein synthesis
(Fig. 11.7).
11.10.2 Semiochemicals
Semiochemicals are chemical substances produced by the organisms that enable and
mediate communication between the organisms. Basically there are two types of
semiochemicals, namely intraspecific semiochemicals (pheromones) and interspecific semiochemicals (allelochemicals). Pheromones are volatile chemical
substances produced by an organism so as to elicit a reaction or response from the
receiving individual (of same species). The releaser pheromones cause behaviour
change in the recipient. The releaser pheromones include sex pheromones,
Table 11.8 List of commercially available biochemical pesticides
Plant source
Target pest
Commercial name/compounds
Azadirachta spp.,
Nicotiana spp.
Aphis craccivora, Bollworms,
Aphids, Jassids, Thrips, Whitefly,
Leaf folder, Pod borer, Fruit borer,
Leafhopper, Diamondback moth
Essential oils, nicotine,
azadirachtin, salanin, nimbin,
(leaf, seed, kernel) nimbecidin,
bionimbecidin
Chrysanthemum
cinerariaefolium
Lonchocarpus spp.
Ryania spp.
Crawling and flying insects such
as cockroaches, ants, mosquitoes,
termites
Pyrethrium, Rotenone
Ryanodine
Artemisia annua
Helicoverpa armigera
Essential oils from leaf and
seed
Vinca rosea
Helicoverpa armigera
Essential oils from leaf and
seed
Ocimum basilicum
Salvia Officinalis
Aphis craccivora Koch, Agrotis
ipsilon
Essential oils form aerial parts
leaves
Citrus sp.
Fleas, aphids, mites, paper wasp,
house cricket
D-limonene linalool
Schoenocaulonofficinale Bugs, blister beetles fly,
caterpillars, potato leafhopper
Sabadilla dust
Adenium obesum
Cotton pests
Chacals Baobab (Senegal)
258
M. Rajamani and A. Negi