Chapter 4 Spider Mites
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(1986); Jindra et al. (1991); Osborne et al. (1995); Fischer and Leger (1996); Sampson et al. (1996); Wilson et al. (1996); Gillespie et al. (1998); Rott and Ponsonby (2000a, b). Chemical control Chemical control of spider mites is becoming more and more difficult due to the rapid development of resistance in mites and the decrease of the number of registered acaricides for use. For example, clofentezine resistance in T. urticae was recorded in Australia in 1987 after mites in Queensland greenhouse roses had been exposed to 40 applications of clofentezine over a ten-month period; clofentezine resistance in this strain was extremely high (>2,500X) and conferred high level cross-resistance to the chemically unrelated compound hexythiazox. However, some chemicals appear to be less susceptible to resistance development in mites. T. urticae was subjected to four, six or 15 times of artificial selection of resistance to abamectin and no increased resistance to the pesticide was detected; abamectin is one of the most widely used chemicals in greenhouses. However, development of resistance of T. urticae to this pesticide has now been reported in some populations. Chemicals and methods for control vary greatly depending on level of mite resistance, crop and environmental conditions, and the availability of registered material in different countries. No general recommendations will be given here. Interested readers should study the references suggested here and are advised to consult local pest control advisers in plant protection or pest control organizations. References & suggested further reading. Green et al. (1984); Hoy and Conley (1987); Jensen and Mingochi (1988); Dong (1990); Richter and Schulze (1990); Papaioannu-Soulioti (1991); van de Veire and Degheele (1992); Aguiar et al. (1993); Herron et al. (1993); Szwejda (1993); Zhang and Sanderson (1995); Rossi and Conti (1997); Jacobson et al. (1999); Szwejda (1999); Makundi and Kashenge (2002). Integrated control More and more greenhouse pests are now under integrated pest management (IPM) programmes and T. urtiace is one of these. The key to the success of IPM programmes is careful monitoring of pest populations and the application of control measures only when necessary. That is, control measures are applied only when spider mite densities exceed the action threshold. In IPM programmes, the use of pesticides is minimized and the use of biological control and other environmentally sound methods are encouraged. It is important that chemical control, when it is used, should be integrated with other control methods such as biological control.