Life parameters of Tetranychus urticae (Acari: Tetranychidae) on six common bean cultivars.

It is well recognized that the quality of host plants affects the development and survival of twospotted spider mite Tetranychus urticae Koch. The life table parameters of T. urticae, on six cultivars of common bean (Phaseolus vulgaris L.) (chiti Khomein, chiti Ks21189, red Akhtar, red Ks31169, white Pak, and white G11867) were studied at constant laboratory conditions (27 +/- 2 degrees C, 70 +/- 5% RH and 16:8 L:D). Total development times of immature males and females were significantly influenced by bean cultivar. T. urticae laid significantly more eggs per day on red Akhtar (16.16) than on the other cultivars. The mean generation time ranged from 23.37 to 34.82 d, and a significant varietal effect was seen. Percentage of egg hatchability oftwospotted spider mite ranged from 88.25 to 94.20%. The highest intrinsic rate of increase, was recorded on red Akhtar (0.269 +/- 0.031) and the lowest value was obtained on white Pak (0.129 +/- 0.048). In addition, net reproductive rate and finite rate of increase of the twospotted spider mite had the highest value on red Akhtar: 62.38 +/- 1.05 and 1.30 +/- 1.02, respectively. The lowest values of these parameters were recorded on white Pak as 26.11 +/- 1.40 and 1.13 +/- 1.10, respectively. Doubling time varied significantly on different cultivars and the lowest and highest values were obtained on red Akhtar and white Pak, respectively. Our findings revealed that white beans (Pak and G11867) were less suitable cultivars, suggesting that they are more resistant to the twospotted spider mite than the other cultivars.