The occurrence of fiveTetranychusspp. (Acari: Tetranychidae) in New Caledonia and their responses to acaricides

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Abstract
Five of the seven Tetranychus spp. found in New Caledonia are of actual or potential economic importance, and observations were made on the occurrence of these species. Tetranychus neocaledonicus was the most widely distributed, being found on 42 species of tropical plants and on two temperate hosts, but it was not recorded where pesticides were regularly applied. Tetranychus ludeni was recorded along the west coast, mostly on cultivated plants including some which had been sprayed. Tetranychus Iambi and T. marianae were found on tropical hosts including cultivated plants, but never in sprayed areas. In contrast, T. urticae was restricted to sprayed situations and was only recorded on cultivated plants and weeds growing within 40 km of Noumea; it was the major mite pest of commercial crops in the island. Laboratory testing of six acaricides against three New Caledonian strains of T. urticae and a susceptible strain showed that the New Caledonian strains were highly resistant to dimethoate, profenofos, monocrotophos and methidathion. Two were also highly resistant to dicofol while the third was moderately resistant (x18). The three strains were susceptible to cyhexatin. The relative toxicities of the six acaricides to the susceptible strain of T. urticae and the other four species were similar, indicating that these four were susceptible.