Novel strategies for sustainable management of citrus rust mite, Phyllocoptruta oleivora (Ashmead) (Acari: Eriophyidae) in Texas

The citrus rust mite (CRM), Phyllocoptruta oleivora (Ashmead) (Acari: Eriophyidae), has been for over half a century the most economically important pest affecting citrus production in Texas. Its feeding causes conspicuous injury to the fruit leading to blemish and discoloration of the fruit rind. Affected fruit are unattractive and lose their cosmetic appeal. Heavy infestations early in the season can reduce fruit size, thus significantly affecting citrus production. However, because citrus produced in Texas is essentially destined for the fresh fruit market, the citrus rust mite is particularly important limiting factor to profitability because of the blemish it causes to the fruit. Grower surveys clearly indicated that CRM is the priority pest in Texas, with at least half of the orchard pest control costs directed at this pest. Although no citrus species is known to be resistant to CRM, comparative studies showed that grapefruit is more suitable for the development of CRM compared to sweet oranges. The softer leaves of grapefruit may result in this higher performance of CRM on this host plant. All citrus cultivars grown in Texas are susceptible to citrus rust mite, and there is no known source of resistance. A number of natural enemies are recorded feeding on citrus rust mite in Texas, but due to the high reproductive potential of the mite favored by the subtropical climatic prevailing in south Texas, natural enemies are unable to maintain citrus rust mite population below an economic threshold.;The use of chemical miticides is the only management strategy that can provide satisfactory control of citrus rust mite population in south Texas. Traditionally, growers scout for mite population and once a certain population level is reached, they decide to spray. However, this reactive approach provides temporary control of the mite in citrus orchards. Since citrus orchards are evergreen vegetation that allows the survival and reproduction of the mite year round, effective control will require targeting citrus rust mite when its populations are at their lowest and weakest in orchards. Citrus rust mite densities are lowest during winter. This dormant control approach has been termed as 'proactive' spray. This study was undertaken to investigate the importance of CRM from growers' perspectives, and to develop a novel, proactive approach for managing the citrus rust mite by testing the efficacy of proactive spray in the control of citrus mite.;Results of the proactive spray program indicated that early sprays of citrus orchards are the best management strategies for reducing CRM densities, infestation and damage levels in citrus orchards. Thus, for the same chemical input, early sprays increased the economic returns relative to post-bloom spray initiations. We also tested the efficacy a newly developed insecticide Movento (a.i. spirotetramat) in the control of CRM. Movento is developed by Bayer CropScience and has some good miticide effects on CRM although in the field the residual control did not exceed 4 weeks.