The Action and Characteristics of Abamectin
Abamectin is a disaccharide macrolide compound, a natural product isolated from soil microorganisms, having contact-kill and stomach poisoning action and weak fumigation against insects and mites, no systemic action. But its strong permeation to leaves can kill pests under the skin, and the longevity of residues is long. Its mechanism of action is different from the general insecticide: it interferes with insect neurophysiological activity, to stimulate them to release r- amino butyric acid, which can inhibit arthropods’ nerve conduction, that mites and insect larvae will be paralyzed after contacting with the agent, then no movement or feeding and die after 2-4 days. Because they do not lead to rapid dehydration of insects, its lethal effect is slow. It has direct killing effect on predatory and parasitic natural enemies, but less surface residue in plants, there is slight damage to beneficial insects.
Abamectin can penetrate the leaf tissue after crop spraying, forming a thin walled anther sac within the epidermis cells for long-term storage, so abamectin has long persistence. Its good level shift activity makes abamectin effective on pest mites, leaf miner, leaf miner and borer pests or other sucking insects which other conventional agents are difficult to control. Abamectin easily biodegrade in soil and water, adsorbed by the soil without residue, pollution-free, or in vivo accumulation or persistence of residues, so it is non-polluted pesticide. It can also be decomposed into derivatives with higher activity by soil microorganism.
Effects are different because of different abamectin manufacturers. We know there is a big drawback of abamectin that it is light and very easy to break down in the presence of oxygen, tests show its half-value period is only 4-6 hours after the formation of abamectin membrane； that is，it will completely decompose within eight hours after put into rice fields. The most important way to delay its decomposition is to add UV absorbers or antioxidants (BHA or BHT), while adding antioxidants (BHA or BHT) is more effective than adding UV absorbers. So some manufacturers might have done it, which leads to avermectin decomposition difficulty and shows higher control efficiency.
Some manufacturers may have added organosilicone or something similar into abamectin. In the past, the foliage spreading agent was not allowed to be used with abamectin pesticide because after using it abamectin (including emamectin benzoate) will spread over on the surface of the crop to form a thin membrane, and then break down in sunlight immediately and lose effectiveness. Nonetheless, we can add penetrant. Organosilicone has both penetration and spread function. Abamectin has bad systemic action, ordinary tag toxicity, so it functions mainly through the stomach poison. After fipronil is sprayed onto the leaves, the crop can absorb the agent so that the whole rice plant is in drug liquid. Directly spraying abamectin into leaf borer body to cause death is not so effective. The best action of abamectin is to let leaf borer eat the sprayed poisoned leaf blade and then die, which is the stomach poisoning. So thorough spraying is necessary, and it is best to get each leaf sprayed. Of course, this is impossible. Silicone has a strong penetration and development that only one spray to a small portion of the entire leaf blade will be covered with liquid, so leaf roller which has eaten the poisoning blade covered liquid will get poisoned immediately, slowly dying. Hence，silicone avermectin has great synergies when abamectin provides leaf roller control efficiency.