Diazinon resistance

Recently, a P450 clone was prepared from phenobarbital induced, diazinon resistant, house flies (18). While the amino acid sequence near the heme-binding site is conserved compared to others, the house fly gene was assigned a new family, P450VI, because its overall amino acid sequence was insufficiently similar to any previous family. Several forms of P450 are known to exist in the house fly (19.20). 

A nnmber of other examples are known in which genetically based resistance was dne to enhanced detoxication of OPs. These include malathion resistance in some stored product pests owing to high carboxylesterase activity, and resistance of strains of the housefly to diazinon due to detoxication by specific forms of a glutathione-S-transferase and monooxygenase (Brooks 1972). 

Control of cattle ticks has followed a similar transition from broad spectrum organophosphates to more selective agents with novel mode of action. In 1956 diazinon (81) was introduced into Australia as the first organophosphate for tick control. Evidence of OP resistance was first detected in 1963 and in 1966 chlordimeform (84) was demonstrated to control the OP-resistant strains. 

Pregnant rats showed embryotoxic and teratogenic resistance to Diazinon, whereas Beagles showed a high incidence of stillbirths at 1, 2, or 5og/kg/day administered per os. 

It should be clear to us that the development of resistance is always to be expected to any insecticide we may choose to apply, but it is not inevitable. DDT stayed effective against the European corn borer for at least 15 years (Table VIII) and there are several other examples, including diazinon and the western corn rootworm in Nebraska. Some of the species of beneficial insects which formerly suffered from insecticide damage, such as braconid parasites, lady beetles, mayfly nymphs and honeybees, have now developed certain tolerances, while several of the Phytoseiid mites which feed on the plant-feeding spider mites are becoming as resistant as their prey to OP s and carbamates. 

Forgash, A.J. and Rily, R.C., Mechanisms of resistance in diazinon-selected multi-resistant Musca domestica, /. Econ. EntomoL, 55, 544,1962. 

Yang, R.S.H., Hodgson, E., and Dauterman, W.C., Metabolism in vitro of diazinon and diazoxon in susceptible and resistant house flies, j. Agric. Food Chem., 19,14,1971. 

Lewis, J.B. and Sawicki, R.M., Characterization of the resistance mechanisms to diazinon, parathion and diazoxon in the organophosphorus-resistant SKA strain of house flies (Musca domestica L.), Pestic. Biochem. Physiol., 1, 275,1971. 

The so called external insecticides coat the surface of the plant and have more or less penetration power (e.g., azinphos-methyl and -ethyl, dichlorvos, diazinon, malathion, parathion-methyl, and -ethyl). Others, called systemic insecticides, penetrate the plant tissue, are transported by the sap, and diffuse within the plant (e.g., dimethoate, mevinphos, omethoate, vamidothion). Mites have developed a resistance to OPPs, most of which are no longer marketed as acaricides. OPPs are now found in products developed to treat plants, soil, buildings, and foods. 

SABOURAULT, C., GUZOV, V.M., KOENER, J.F., CLAUDIANOS, C., PLAPP, F.W., JR., FEYEREISEN, R., Overproduction of a P450 that metabolizes diazinon is linked to a loss-of-function in the chromosome 2 ali-esterase (MdalphaE ) gene in resistant house flies. Insect Molec. Biol, 2001, 10, 609-618. 

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