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dc.contributor.authorReddy, Gadi V. P.
dc.contributor.authorKikuchi, R.
dc.contributor.authorBautista, J. R.
dc.identifier.citationReddy, G.V.P., R. Kikuchi, and J.R. Bautista. 2013. Threshold-based spraying decision programs for the red spider mite Tetranychus marianae on eggplant. Journal of Applied Entomology 137: 429–436.en_US
dc.description.abstractThe red spider mite, Tetranychus marianae McGregor (Acari: Tetranychidae), has been an important pest of eggplant Solanum melongena L. (Solanaceae) and other vegetables in the Mariana Islands. The damage due to T. marianae has been severe and caused huge economic losses. Because no threshold levels are available for T. marianae, many growers are applying up to 12 chemical applications per eggplant cropping period. This is not only expensive, but also results in lower yields because of extensive foliar damage and development of resistance in mites to chemicals. To diminish the calendar-based chemical applications and to preclude damage to foliage and fruit quality, this study was undertaken for the development of a threshold level for optimum timing of chemical applications for T. marianae. In the direction of this aim, an attempt was made to generate different threshold levels by applying chemical spray (Sun-spray 6E, 5 ml/l) within 12 h after reaching the threshold levels at 2, 4, 6, 8 and 10 mites/leaf, as well as current recommended calendar-based sprays and non-sprayed control in a replicated block design for the dry and wet seasons of 2010 at two locations (Yigo and Inaranjan) in Guam (USA). Based on T. marianae-infested leaves, incidence of T. marianae and yield levels, the plots sprayed at 2 or 4 mites/leaf in the dry season and 2–8 mites/leaf during the wet season had significantly lower leaf damage and incidence of T. marianae compared with a greater number of mites/leaf in calendar-based sprays and control plots. At the greater threshold levels, the mean yield was significantly reduced in comparison with the mean yield obtained when plots were sprayed at a threshold of 2–8 mites/leaf. Therefore, it is concluded that the optimum threshold chemical spray for T. marianae on eggplant is 4 mites/leaf during the dry season and 8 mites/leaf in the wet season.en_US
dc.description.sponsorshipUSEPA: Strategic Agriculture Initiative/Food Quality Protection Act (FQPA) Grant Agreement # X8-00T32301-0; Pacific Islands Area Conservation Innovation Grants (PIA-CIG) Program, Grant Agreement No. 69-9251-10-880en_US
dc.titleThreshold-based spraying decision programmes for the red spider mite Tetranychusmarianae on eggplanten_US
mus.citation.journaltitleJournal of Applied Entomologyen_US
mus.identifier.categoryLife Sciences & Earth Sciencesen_US
mus.relation.collegeCollege of Agricultureen_US
mus.relation.departmentResearch Centers.en_US
mus.relation.universityMontana State University - Bozemanen_US
mus.relation.researchgroupWestern Triangle Ag Research Center.en_US

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