Central Tuber Crops Research Institute, Trivandrum
1. Present Address: Entornologist Project Directorate (Pulses) I.A.R.I., Regional Station Kanpur - 208 024
Tetranychid spider mites are serious pests of cassava crop particularly during dry months of December to April in Kerala. Two replicated field experiments we:e conducted during 1976–77 and 1977 78 to study the effect of mite infestations on tuber yield of cassava in 3 varieties. Two mite populations i. e. low population and high population were maintai-ned in the first year trial and three mite populations i. e. low. high and medium in the sec9nd year trial the differences in tuber yield in first year trial showed 1hat plots maintai-ned with low mite population gave 21.37, 20.39 and 22.83 percent increase in tuber yield in comparison to the plots maintained with high mites population in cultivars H 2304, H 97 and M 4, respectivety the difference were significant at 5 percent level.
In the second year experiment the percent increase in tuter yield in low mite popula-tion plots recorded was 41.52. 46.77 and 19.44 over high mites population plots whereas per-cent increase in yield in case of medium mite population maintained plots over control (high population) was 16.66. 25.71 and 15.18 in the cultivars H 2304, H 97 and M 4, respectively. The difference in tuber yield between high and low mite population levels were significant for all 3 varieties but between medium and high mite populations the diffe-rences in yield were nonsignificant in H 2304 and H 97 but were significant in M 4 cultivar.
