Aphids are sap-sucking organisms. Neem (Azadirachta indica), a systemic insecticide, should help protect your crop.
Neem oil is not an instantly effective insecticide. Spraying it on crops does not result in the immediate elimination of harmful insects and pests. The oil’s action on the pests and insects is through their hormone system, affecting their metabolism. On ingesting the oil, Insects stop eating and cannot breed, propagate, and proliferate, breaking their lifecycle. In time, the pests die, and the entire colony disappears. Pest eggs are also not able to hatch, and the larvae are not able to molt.
Chewing and sucking insects only get impacted by neem oil. The action of neem is selective, with destruction restricted to only this variety of pests. Neem oil acts slowly, unlike fast-acting chemical insecticides, but the action is long-lasting. The quantities of neem oil required are also much smaller, and the insecticide action takes place at deficient concentrations.
Neem oil is a very powerful antifeedant and insect repellent. The oil is especially susceptible to ultraviolet light. The oil, in the diluted form, can be applied to the soil. The insecticide travels into the plant body with water and nutrients, providing long-lasting insecticidal properties to the crop. The insecticidal action takes place in situ. An insect may take a bite or two of such plants but then stop due to systemic impact.
Azadirachtin forms 90% of neem oil insecticide. Salannin, another substance obtained from neem, is a powerful repellent deterring pest from biting on plants that otherwise they would love to feed upon. The deterrent action is more powerful than the synthetic chemical called “Deet” (N N Diethyl meta toluamide). Deet is an ingredient in most of the insect repellents commonly found in the market.
The biopesticide action of neem commences when an insect larva feeds on the plant. The active molecules in neem—azadirachtin, salanin, and melandriol—cause an anti-peristaltic wave in the alimentary canal in the insect, causing a vomiting sensation that forces them to stop feeding.
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