Effect of Pruning and Trellising of Tomatoes on Red Spider Mite Incidence and Crop Yield in Zimbabwe

Red spider mite, Tetranychus evansi Baker & Prichard, is a relatively new pest of tomato ( Lycopersicon esculentum ) in Africa, accidentally introduced into southern Africa around 1980. Since then, the species has spread and was recorded for the first time 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 trellising 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 treatments. Unpruned and untrellised plots had 37.7 and 30.2 mites per leaf, respectively, in Mutoko, while the pruned and trellised plots had 4.6 and 17.3 mites per leaf. In Muzarabani, mite densities were 4.8 in the pruned and trellised plots, and 4.6 in the 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 incidence, less fruit rots and a reduced damage in fruits. Pruning and trellising resulted in additional profit of US$ 18,780 per hectare at Mutoko.La petite araignée rouge, Tetranychus evansi Baker & Prichard accidentellement introduite en Afrique Australe vers 1980 est une peste relativement nouvelle pour la tomate ( Lycopersicon esculentum ) de l&apos;Afrique. Depuis lors l&apos;espèce s&apos;est répandue. Elle a était enregistrée pour la première fois au Kenya en 2001. L&apos; International centre of Insect Physiology and Ecology (ICIPE) ensemble avec le National Research Institutions and southern Africa sont entrain de développer des méthodes de contrôle intégrées pour cette nouvelle peste. Les effets de la taille et du treillage sur l&apos;incidence et le contrôle de la peste aussi bien que les dommages et les rendements de la tomate étaient évalués en des endroits du Zimbabwe ou la production de la tomate est importante: Mutoko et Muzarabani. Les pratiques considérées simples ou combinées n&apos;avaient pas d&apos;effets sur l&apos;infestation initiale. Le niveau des dommages et le développement de la population sont devenus apparents dans les dernières tapes de la plante à Mutoko. A Muzarabani la population d&apos;araignée est restée faible durant toute la saison et ne montra aucune différence significative due au traitement (p