*Please inquire the availability for this product. Δ2-Avermectin B1a is an irreversible base degradation product of avermectin found in animal treated with avermectin and in the environment. Δ2-Avermectin B1a is formed by rearrangement of the naturally-occurring Δ3-group to the 2-position. Although less active than the parent, Δ2-avermectin B1a is nonetheless active in the at 1 ppm.