Mites injurious to legume crops
1993
Angsumarn Chandrapatya (Kasetsart Univ., Bangkok (Thailand). Faculty of Agriculture. Dept. of Entomology)
Tetranychus hydrangeae Pritchard & Baker is a pest of soybean and mungbean grown at Nakorn Pathom province. Life cycle study of T. hydrangeae indicated that the mite requires 5.7 and 7.8 days to complete its development on soybean and mungbean, respectively. The developmental stages include egg 1.38 and 2.96 days, larval 0.81 and 1.26 days, protronymphal 0.80 and 0.82 days and deutonymphal periods 0.79 and 0.99 days on soybean and mungbean. Three resting stages preceed the protronymph, deutonymph and adult stages require 0.69 and 0.52 days, 0.51 and 0.55 days and 0.78 and 0.73 days, respectively. Both unseminated and seminated females produced male and female offspring as indicated by the sex ratio of 1:0.1 and 1:2.29, respectively. There were no significant different in the female longevity (22-23 days) and the oviposition period (19-20 days) between unseminated and seminated females. However, the unseminated female laid fewer eggs/day (4.01 eggs) and fewer total number of egg/female (74 eggs) as compared to the seminated one (5.36 egg/day and 102 eggs/female). Life table study of T. hydrangeae in the laboratory revealed that this species had the net reproductive rate (Ro) = 42.42, cohort generation time (Tg) = 14.37 days, innate capacity for increase (rc) = 0.26 and finite rate of increase (lambda) = 1.30. Seven pesticides were evaluated against the egg, nymphal and adult stages. Dinobuton, dicofol and amitraz were proved to be effective against all stages. Propargite was also considered for adult stage whereas formothion was good for adult and nymphal stages.
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