LOW DOSAGE METHOPRENE TREATMENT OF WHEAT FOR PROTECTION AGAINST STORED-PRODUCT INSECTS AND ASSESSMENT OF THEIR DAMAGE (RICE WEEVIL, INDIAN MEAL MOTHS, BEETLES)

Methoprene at 0.3 to 5 ppm applied to wheat in water or mineral oil was tested as a protectant treatment against five species of stored-product insects. Also, damage by two species was assessed at 0.15 and 5 ppm.;At 3 months, numbers of rice weevils adults decreased as methoprene concentration increased, but at 4.5 months numbers increased and control was not acceptable for any treatment. This was supported by bioassays.;Although red flour beetles (RFB) produced larvae, production of new adults was very low even at the lowest dosage tested.;Saw toothed grain beetles and flat grain beetles (FGB) were effectively controlled. In bioassays 4.5 months after treatment, few FGB adults were produced at 0.3 ppm, although insects were able to pupate in all treatments except 5 ppm.;Lots of 81.6 kg were treated, infested with all five species, stored at 25 (+OR-) 1(DEGREES)C and 65 (+OR-) 5% RH, and then sampled after 3 and 4.5 months for insect population counts. Each insect species was also bioassayed separately.;In bioassays 4.5 months after treatment, production of Indian meal moth (IMM) adults was completely suppressed at 1.25, 2.5 and 5 ppm, and very few were produced at 0.6 ppm.;Methoprene applied in mineral oil was not more effective than that applied in water.;In damage assessment tests, IMM and RFB produced supernumerary larvae; however, most IMM larvae died before 60 days. After 120 days, IMM and RFB produced 24 and 99.3 F1 adults at 0.15 ppm, and none and 5.3 at 5 ppm, respectively.;IMM predominantly damaged whole kernels, and degermed more kernels than RFB. Damage was not reflected in weight of 500 kernels, nor in weight loss in whole-kernel fractions. RFB fed almost equally on whole- and broken-kernel fractions, and produced large quantities of fines.;Grain weight loss due to RFB after 120 days was not affected by treatments (including control), but damage by IMM was: 5 ppm treatment showed lowest loss, significantly different than that at 0.15 ppm and control.