Abstract

Two factors, transplanting date and insecticide frequency were combined to evaluate their effects in reducing
population of thrips and yield of onion. Transplanting was done at monthly interval from November through
March, 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 in
November and December had fewer thrips than the subsequent ones. At 7 WAT, late transplanting made in
February had up to 191 thrips/plant and< 1 in the early transplants. First spray was effective in reducing thrips by
about 76% and second and subsequent sprays were less effective. There was significant difference between
treatments (P<0.05) in spray at 4, 6, 7, 9 and 10 WAT and the bulb yield of onion. The yield showed that two
sprays produced up to 52.53 t/ha, nearly doubling the control plots with 31.6 t/ha. November transplant produced
up to 60 t/ha and December transplant 51.82t/ha in three-insecticide spray. The average weight of bulbs from
plots with 2 sprays and control plots were 238 g and 155 g, respectively.

This work is licensed under a Creative Commons Attribution 4.0 License.