Comparative effects of systemic insecticides on cotton and associated arthropod populations under dryland and irrigated regimes
Field studies were conducted in 1989 and 1990 to evaluate the effect(s) of systemic insecticides (Temik 15G®, aldicarb; Thimet 20G®, phorate, and Furadan 15G®, carbofuran) on cotton, and its associated arthropod fauna under irrigated and dryland cropping systems. One rate of each insecticide was used at planting. In-furrow water application was made in the treatments with irrigated regime according to Gypsum Block-Resistance Meter readings. Arthropod population (pests and beneficial) was low in both years during the field study, resulting in the lack of significant difference due to treatment effect. Other factors held constant, response of the cotton plant was directiy associated with the treatment applied. Insecticide application-water regime combinations had significant effect on most growth and reproductive parameters measured. Earliness and yield were subsequently affected by the combination treatments. Fiber quality was not affected by treatments. In an adjunct laboratory study using in vitro cotton tissue-cultured calli, several rates of the same insecticides were used. Observations were made on cell phenology and quantified by visual ranking. Cell phenology was altered. This observation was also true for cell growth resulting in difference in fi-esh and dry weight production. Stimulatory effect was observed mostly in the lowest and moderate rates of any of the insecticides applied, while inhibition was found in the highest application rates.