In laboratory conditions (25?1.C and 60?5% r.h.) effects of natural
insecticides spinosad and abamectin on five S. oryzae populations
(laboratory, Sid, Gornji Milanovac, Zabari and Novi Pazar) were investigated.
Both insecticides for all tested populations were applied to untreated wheat
grain at following rates 0.25, 0.5, 1.0 and 2.0 mg AI/kg, subsequently 25
adults were added in each plastic vessels (V=200 cm3) containing 50 g of
treated wheat, in four replicates, for each population tested. Mortality of
weevils was determined after 2-, 7- and 14-days, and the effect on progeny
production was determined 8-weeks from parental exposure. Efficacy of
spinosad and abamectin after 2-days of weevil exposure for all tested
populations and all application rates was <15%. After 7-days of exposure, the
efficacy was ?95% for weevils from Zabari, in wheat treated with 2 mg/kg of
spinosad and abamectin, and for weevils from Gornji Milanovac, only in wheat
treated with 2 mg/kg of spinosad. After 14-days of exposure the efficacy ?95%
was found for laboratory weevils and weevils from Zabari and Gornji
Milanovac, in wheat treated with 1 and 2 mg/kg of spinosad, and for S. oryzae
from Novi Pazar and Sid, in wheat treated with 2 mg/kg of spinosad. At the
same time for all tested populations abamectin at rates of 0.5, 1.0 and 2.0
mg/kg was 94-100% efficien t. No insecticide achieved total (100%) progeny
reduction in tested populations of S. oryzae, while high progeny reduction
(?95%) was found only in weevils which were in contact with wheat treated
with 1 and 2 mg/kg of abamectin. The results showed that for highly efficient
control of different populations of S. oryzae in wheat grain, ?2 mg/kg of
abamectin, and, particularly, spinosad should be applied.
Inheritance of resistance to rice weevil (Sitophilus oryzae L.) in bread wheat (Triticum aestivum L.)
