INVIVO INHIBITION OF ESTERASE AND ACETYLCHOLINESTERASE ACTIVITIES BY PROFENOFOS TREATMENTS IN THE TOBACCO WHITEFLY BEMISIA-TABACI (GENN) - IMPLICATIONS FOR ROUTINE BIOCHEMICAL MONITORING OF THESE ENZYMES

Insecticide-resistant populations of the tobacco whitefly, Bemisia tabaci (Genn.), lost over 90% of esterase activity and approximately 20% of acetylcholinesterase activity after treatment with 500 g/ha profenofos under field-simulated conditions. A more detailed study showed that esterase activity was completely inhibited within 2 days in insects confined on single cotton leaves treated with 50 g/ha profenofos (LD10) thereby preventing their discrimination from susceptibles which normally have low activity. However, esterase activity recovered sufficiently within 3 days when insects were transferred from the treated to untreated cotton leaves, thus enabling their correct classification as resistant. The inhibition/recovery profile for acetylcholinesterase closely followed that of the esterase system. © 1991.