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Revised

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Four insecticides were evaluated for their effect on onion seed production in Yuma County where two species on thrips (western flower and onion) were present in seed fields. Visual differences between treatments resultant from onion thrips damage was 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. Only Ammo and Capture treatments increased seed yield as the Lorsban treatment was thought to repel bees which are needed for pollination. Pyrethroid treatments yielded 40% more than the untreated check. Damage from onion thrips to onion seed in Yuma County is conservatively calculated to currently be at least $1.1 million annually.

Onions treated at the 2-leaf stage of growth with the 3rd leaf just beginning to emerge with postemergence herbicides bromoxynil (Buctril®) and oxyfluorfen (Goal®) exhibited slight injury at 11 days after treatment (DAT) but had recovered to show no injury at 1 month after treatment (MAT). Annual yellow sweetclover (Melilotus officinalis) was the predominat weed in the test site and early ratings showed that Goal at 0.25 lb a.i. /A and Goal plus Buctril gave marginally acceptable control at 80 %. Buctril alone did not control clover. At 1 MAT, the clovers had recovered from the initial injury and the level of control had declined to become unacceptable.