Effect of Mulch Color and Spinosad Sprays on Thrips Population,Size and Quality of Sweet Onion(Abstract)

摘要

Production of sweet onions for the PA Simply Sweet~R Program is a newer option for growersseeking to diversify their farming operation.Control of onion thrips,the main insect pest on this crop,isa concern because of resistance issues.Two varieties of onion were planted on three mulch colors;afterthrips populations developed half of each plot was sprayed with spinosad.Counts of thrips per leaf werehighest on white mulch on two separate counts prior to spinosad application.There was no differencebetween black and silver on the first count while silver was lower than black on the second.Visualdamage was lowest on silver mulch for both counts;black was not different than white on the first countbut was lower on the second.After spinosad treatment there were no differences in thrips populationsbetween mulches.Onions grown on silver mulch had the highest soluble solids while those grown onblack were lowest.Onions grown on white plastic had intermediate values and were not different fromthose grown on black or silver mulch.There was no effect of mulch color on average bulb size."Expression" had higher numbers of thrips per leaf on the first count but was not different from "Candy"for other measurements.Spinosad application reduced thrips populations and damage rating on thepost-spray rating but did not affect soluble solids or average bulb weight.