Abstract
Two 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
Highlights
1.1 Importance of onionThe common onion, Allium cepa L. is a vegetable crop of commercial importance throughout the world
The effect of 2 sprays was seen in 2002/2003 season where there was an increase in population of thrips from 26.3 to 190.7/plant (7WAT) after the effect of spray had subsided from 5-6 weeks after transplanting (WAT)
The effects of the insecticide sprays did not appear to last more than 7 days in the suppression of thrips population after they were applied whether in one, two or three sprays
Summary
The common onion, Allium cepa L. is a vegetable crop of commercial importance throughout the world. The crop ranks second in importance after tomato among the vegetables in Nigeria. It is grown mainly for its bulb, which is used almost daily in every home (Amans et al, 2000). The bulb onion is normally harvested at the start of the dormant period (Brice et al, 1997). Onion can be grown under a wide range of climatic conditions, but they do best in a mild climate without excessive rainfall or extreme temperature. They require cool, moist conditions for early growth, followed by warm, drier conditions for maturation, harvest and curing (Purseglove, 1992)
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