EFFECT OF PRUNING AND TRELLISING OF TOMATOES ON RED SPIDER MITE INCIDENCE AND CROP YIELD IN ZIMBABWE

摘要

Red spider mite, Tetranychus evansi Baker & Prichard, is a relatively new pest of tomato (Lycopersicon esculentwn) in Africa, accidentally introduced into southern Africa around 1980 Since then, the species has spread and was recorded for the first ti me in Kenya in 2001. The International Centre of Insect Physiology and Ecology (ICIPE), together with National Research Institutions of eastern and southern Africa, are developing integrated control methods for this new pest. The effects of pruning and t rellising on red spider mite incidence and control, as well as damage and yield of tomatoes were investigated in two important tomato production areas of Zimbabwe (Mutoko and Muzarabani). The practices, considered singly or combined, had no direct effect on initial infestation. Damage levels and population development became apparent in the later crop stages at Mutoko, while at Muzarabani, mite population levels remained low throughout the season, and showed no significant (P<0.05) differences between t reatments. Unpruned and untrellised plots had 37.7 and 30.2 mites per leaf, respectively, in Mutoko, while the pruned and trellised plots had 46 and 17.3 mites per leaf In Muzarabani, mite densities were 4.8 in the pruned and trellised plots, and 46 in t he control Chemical control was more effective on the pruned and trellised plots resulting in a yield increase of 60% in both trials at Mutoko, but not at Muzarabani Pruning and trellising at Mutoko resulted in better mite management, less disease incide nce, less fruit rots and a reduced damage in fruits Pruning and trellising resulted in additional profit of US 18,780 dollar per hectare at Mutoko.