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Some Ecological Studies and Economic Injury Levels of the Leafhopper (Idioscoppus Clypealis (Leth.)) on Mango (Mangifera Indica (L.))
Dissertation Abstract:
The ecology and economic injury levels (EIL) of Idioscopus clypealis (Leth.) were studied in May 1984-June 1986 in Central Visayas, Philippines. This pest was found to be the most destructive species of mango leafhoppers. Under natural conditions (untreated), the population fluctuation of the pest was influenced by the stage of panicle development, but under different insecticide pressure, it was more affected by the efficacy of insecticide application.
The treatment decision lines for sequential sampling on leafhoppers were: d = 1.820n ± 2.6801. Some preying mantis and four species of spiders fed on the nymphs of I. clypealis.
The most attractive light to adult I. clypealis was natural color. Its attractiveness increased with the increase in wick size, especially during dark nights.
Leafhoppers reduced mango yield. The panicles were susceptible ti infestation at all stages of development. Using multiple linear regression equation, Y = 5.09 + 10.39X1 + 10.18X2 + 9.38X3 + 9.60X4, percent yield loss could be determined for any leafhopper density at any stage of panicle development. Likewise, yield per panicle could be computed following the multiple linear regression equation: Y = 0.3652 - 0.0407X1 - 0.0405X2 - 0.0373X3 - 0.0344X4.
The values of the field EIL of I. cypealis in the firs cropping were 4.21, 4.30, 4.45, and 4.55 adults per panicle at 2, 10, 18, and 26 days after flower bud break (DAFBB), respectively, while in the second cropping these were 4.79, 4.88, 5.06, and 5.18 adults per panicle in the same order or an average EIL of 5.
The control threshold level (CTL) of the same pest in the first cropping for cyfluthrin were 1.86, 1.90, 1.96, and 2.01, while permethrin + piperonyl butoxide were 4.00, 4.08, 4.23, and 4.32 adults per panicle at 2, 10, 18, and 26 DAFBB, respectively. In the second croppingm these were 2.29, 2.32, 2.42, and 2.47 fir cyfluthrin and 4.76, 4.86, 5.04, and 5.15 adults per panicle for permethrin + piperonyl buoxide in the same order. The average CTL in two croppings was three leafhoppers per panicle.
Based on statistical and economic analyses, cyfluthrin was recommended to control leafhoppers. This insecticide offered the highest net benefit and marginal rate of return (MRR) ranging from 157 to 230 percent in two croppings. Permethrin + piperonyl butoxide may also be used since its MRR was more than 40 percent. Such consideration is valuable to the farmers, managers, and industry.
