In 1991 and 1992, insecticide trials were conducted on onion and broccoli grown for seed, respectively, near Yuma, Ariz., to evaluate the effects of insects and insecticide treatments on seed production. Four insecticides (Agri-Mek, Ammo, Capture, Lorsban) were evaluated on onions where both western flower thrips [Frankliniella occidentalis (Pergande)] and onion thrips (Thrips tabaci Lindeman) were present. Visual differences between treatment resultant from onion thrips damage were evident within 10 days after treatments were applied at flower opening. Lorsban, Ammo, and Capture treatments provided control of onion thrips based on condition of seed heads. Ammo and Capture were the only treatments that increased seed yield, as the Lorsban treatment was thought to repel bees needed for pollination. Pyrethroid treatments yielded 40% more seed than the nontreated check, which yielded more than Lorsban and Agri-Mek treatments. Four insecticide treatments (Thiodan, CGA-215944, and two rates of RH7988) were evaluated on broccoli seed where green peach aphid [Myzus persicae (Sulzer)] was present. All treatments reduced aphid numbers compared to the nontreated check, with RH7988 providing most control. Seed yields (g/plant) were reduced in all insecticide-treated plots compared with the nontreated plots, although percentage of seed sized larger than 4.5/64” was apparently correlated with increased aphid control. Seed yield per plant was higher from the lower rate of RH7988 than the higher rate. Plants treated with RH7988 had almost 0.5 g/plant more seed sized 5.5/64” than other treatments.
Evaluation of Different Insecticides against Onion Thrips in Onion Seed Production
