Spinosad is a secondary metabolite produced by the fermentation of the soil actinomycete "Spinosad", with macrocyclic Spinosad spinosyn A and spinosyn D as its active ingredients. It is widely used to control lepidopteran and dipteran pests, as well as leafhoppers, on over 150 crops, including cotton, with particularly good efficacy against lepidopteran pests.
1.Mechanism of Action of Spinosad
Spinosad has excellent penetrability and exhibits good stomach poison and contact action against pests. It acts on insect nicotinic acetylcholine receptors (nAChR) and also affects insect gamma-aminobutyric acid receptors (GABAR), thus killing pests. Spinosad is effective against lepidopteran, dipteran, tsioptera, and coleopteran pests, and has relatively low toxicity to mammals and aquatic organisms.
2.Why do the same Spinosad products have such different effects?
First, Spinosad is a bio-fermentation product, and the potency of the active ingredient greatly affects its efficacy. Spinosad is a bio-fermentation mixture, mainly composed of Spinosad A and D types. When the (A+D) ratio is roughly equal, the higher the potency α value (A/D), the higher the activity.
Second, insufficient dosage. Many products marketed are based on marketing concepts. Insecticide components have corresponding median lethal doses (LD50) for different targets. Insufficient dosage not only fails to kill insects but also increases the target's resistance to the active ingredient. Due to the high cost of Spinosad raw material, many products on the market use low actual dosages, often using it as an adjuvant or synergistic ingredient.
Third, different processing methods lead to vastly different efficacies. Many factors affect the efficacy of a product. Spinosad has relatively low solubility in water and requires processing before it can be absorbed and utilized by plants/pests. Besides the purity of the active ingredient, the particle size and uniformity of the product, the type of adjuvants, wetting agents, spreading agents, etc., during the formulation process also play a crucial role in the efficacy of the drug.
