Abamectin is a mixture of avermectins containing more than 80% avermectin B1a and less than 20% avermectin B1b . These two components, B1a and B1b have very similar biological and toxicological properties. The avermectins are insecticidal or anthelmintic compounds derived from the soil bacterium Streptomyces avermitilis. Abamectin is a natural fermentation product of this bacterium. Abamectin is used to control insect and mite pests of a range of agronomic, fruit, vegetable and ornamental crops, and it is used by homeowners for control of fire ants. Abamectin is also used as a veterinary antihelmintic. Resistance to abamectin based antihelmintics, although a growing problem, is not as common as to other classes of veterinary antihelmintics.