Effects of Transplanting Dates and Insecticide Frequency in the Control of Thrips tabaci Lindeman (Thysanoptera:Thripidae) on Onion (Allium cepa L.) in Sokoto, Nigeria

rTwo factors, transplanting date and insecticide frequency were combined to evaluate their effects in reducingpopulation of thrips and yield of onion. Transplanting was done at monthly interval from November throughMarch, while spraying was done fortnightly, starting from three weeks after transplanting (WAT) to nine WAT (3, 5, 7 and 9) using knapsack sprayer at 18.67g a.i./ha. Results showed that early transplanting done inNovember and December had fewer thrips than the subsequent ones. At 7 WAT, late transplanting made inFebruary had up to 191 thrips/plant and< 1 in the early transplants. First spray was effective in reducing thrips byabout 76% and second and subsequent sprays were less effective. There was significant difference betweentreatments (P<0.05) in spray at 4, 6, 7, 9 and 10 WAT and the bulb yield of onion. The yield showed that twosprays produced up to 52.53 t/ha, nearly doubling the control plots with 31.6 t/ha. November transplant producedup to 60 t/ha and December transplant 51.82t/ha in three-insecticide spray. The average weight of bulbs fromplots with 2 sprays and control plots were 238 g and 155 g, respectively