Brassica rapa (rape) seed extracts protectants to wheat grains atainst the lesser grain borer rhizopertha dominica (F.)

摘要

Extracts from Brassica rapa seeds were used as a surface treatment on wheat grains as a protection against Rhithopertha dominica (F.) (Coleoptera). The solvents used for extraction were petroleum ether, choroform or acetone. Pet-ether extraction wasthe most effective on protecting treated wheat grains against the insect (Lc_50=10.4) followed by 12.3 and 14.1 ml/kg for extracts by chloroform and acetone respectively. The tested extracts at the two levels uses Lc_50's and Lc_95' reduced the percentage of F_1 progeny. All extracts at the Lc_95's values gave a bioresidual activity in killing R.dominica adults up to 4 weeks for pet-ether and acetone extracts, while this activity continued till 7 weeks when chloroform was used. Extracts with the solvents tested seemed have adverse effect on germination treated wheat grains. Meanwhile, the percentages of water absorption of treated grains did not vary considerably with different concentrations of extracts applied after 1, 5, and 24 hrs. Besides, all tested extracts have a slight affect on the amount of a, b and total chlorophyll.