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Threshold‐based spraying decision programmes for the red spider mite T etranychus marianae on eggplant
Author(s) -
Reddy G. V. P.,
Kikuchi R.,
Bautista J. R.
Publication year - 2013
Publication title -
journal of applied entomology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.795
H-Index - 60
eISSN - 1439-0418
pISSN - 0931-2048
DOI - 10.1111/jen.12007
Subject(s) - biology , spider mite , horticulture , pest analysis , economic threshold , mite , randomized block design , integrated pest management , chemical control , toxicology , botany , agronomy
The red spider mite, T etranychus marianae M c G regor ( A cari: T etranychidae), has been an important pest of eggplant S olanum melongena L . ( S olanaceae) and other vegetables in the M ariana I slands. 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 ( S un‐spray 6 E , 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 ( Y igo and I naranjan) in G uam ( 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.