Bull. Spec. CORESTA Congress, Harare 1994, p. 98, P 14

The effect of temperature and host plant on the tempo of development and reproduction of Tetranychus evansi

DU TOIT C.L.N.
Tobacco and Cotton Research Institute, Rustenburg, South Africa
T. evansi was first recorded in the Republic of South Africa on tobacco in the Barbeton district during the 1986/87 growing season, from where it spread to all the major tobacco producing areas. In certain areas tobacco is damaged every year by the tobacco spider mite while in other areas it occurs only during hot dry years. To explain this phenomenon, the effect of temperature and host plants in the vicinity of the tobacco on the development and reproduction of the mites was investigated. The effect of mainly Solanaceous host plants and different constant temperatures on the daily egg production of the females and the development time from egg to adult stage were measured. The average number of eggs laid per day and the longevity of the females were strongly influenced by the host plants. The highest average of 15,75 eggs per female per day was measured on potato leaves. On tobacco leaves 11,62 eggs per female per day was the highest average obtained. As the temperature increased from 20°C to 35°C the average egg production increased. The host plant as well as the prevailing temperature had a marked effect on development time. The rate of development increased as the temperature increased from 20°C to 30°C. The results of this research indicated that high temperatures benefit this mite and that some Solanaceous plants are more effective host plants of Tetranychus evansi than other members of the family.