FITNESS OF TETRANYCHUS URTICAE KOCH (ACARI: TETRANYCHIDAE) ON DIFFERENT SOYBEAN CULTIVARS: BIOLOGY AND FERTILITY LIFE-TABLES

The quality of the host plant affects the life-history traits of plant-feeding arthropods. The effect of several soybean cultivars on the fitness of Tetranychus urticae was assayed by determining developmental time and fertility life-table parameters for mites on leaf discs at 25 +/- 1 degrees C, 70 +/- 10% relative humidity and 16 : 8 light : dark photoperiod. Immature developmental time was significantly longer on LWK and Gorgan 3 than on the other cultivars, whereas total fecundity per female was higher on Gorgan 3 than the other cultivars. There were significant differences among the forms of the survival curves of mites on the cultivars. Statistical comparisons of the jackknifed intrinsic rate of natural increase, generation time, doubling time, and finite rate of increase, suggest unsuitability of the cultivars LWK and Gorgan 3 as hosts for the development of two-spotted spider mite. No significant difference was observed for the net reproductive rates among the cultivars. The lower population rate of the mite could be the result of antibiotic resistance in the cultivars LWK and Gorgan 3.