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Effect of Insecticides, Species and Nitrogen Fertilizer on Insect Infestation and Yield of cotton
Thesis Abstract:
The study was conducted to determine the effects of insecticides (Termik 10G and Azodrin), species diversity (cotton alone, cotton with mulch, cotton with peanut, cotton with weeds) and nitrogen fertilizer (ammonium sulfate) on insects infestation and yield of cotton. The experiment was performed at the Central Experiment Station, UPLB, College Laguna from January to May 1975, using the aplit-split plot as the experimental design.
Result showed that Temik was effective only against the sucking insects for 9 weeks, but it also made the plants more susceptible to the chewing insects owing to habitat differentiation between the aphids and the larvae. On the other hand, Azodrin was effective only against the chewing insects and only for weeks. A faster resurgence of the larvae was observed on the sprayed plots, especially at higher concentration of the insecticide. Furthermore, Azodrin-treated plots exhimited greater vegetative growth, hence lower seed-cotton yield.
Increasing species diversity did not diminishe insect infestation. High yields of seed-cotton were obtained with mulched and weeded cotton. Plant competition depressed yields of cotton when unweeded or intercropped with peanut.
Application of nitrogen fertilizer increased seed-cotton yield but made the plants more susceptible to insect infestation.
Based on actual expenses and returs, losses were registered in all treatment combinations, except when peanut was used as an intercup. Losses increased with increase in application rates of insecticide and nitrogen.
First and second-degree interactions among the main treatments were observed only once throughout the period of study , hence these could not be used as basis for the best treatment combinations to adopt.
