Knapp, M., Luchen, S.W.S., 2000.
Tetranychus evansi - a new challenge to small-holder tomato growers in southern Africa. XXI International Congress of Entomology, Foz do Iguassu, Brazil: 12-13.
Abstract
Tomato growers in southern Africa (Zimbabwe, Mozambique, Namibia, Malawi, Zambia) have experienced increasing problems with red spider mites in the last years. In most countries the species involved were usually misidentified as Tetrany-chus cinnabarinus or T. urticae. Recent identifications of material collected in the region show that T. evansi is causing the problems. T. evansi is specialized on So-lanaceae, introduced to southern Africa, probably from South America, expending northwards. Only few natural enemies have been found so far (Phytoseiidae, Anthocoridae, Staphylinidae) and identifications are in progress. Results of surveys conducted in Kenya and Zambia clearly show the impact of different spider mite species on tomato production. In Kenya T. evansi is not yet present and we usually find T. urticae on tomato. Only 1% of the Kenyan farmers considered red spider mites as one of their two most important problems in tomato growing. In Zambia the corresponding figure was 27%. Asked more specifically about most important pest and disease problems, 16% of the Kenyans mentioned red spider mites, the corresponding figure for Zambia was 89%. The current control approach is purely use of chemicals. 42% of the Kenyan farmers and 97% of the Zambian farmers apply pesticides for red spider mite control. Many of these chemicals are highly toxic broad-spectrum insecticides and some of them have only limited activity against mites. In Zambia the most common control agent is monocrotophos (49% of farmers applying pesticides) followed by amitraz (39%), and cypermethrin (10%). In Kenya acaricides are more commonly used. Dicofol is used by 42% of the farmers who apply pesticides, followed by bifenthrin (18%) and cypermethrin (16%). Integrated pest management and classical biological control are discussed as alternative strategies to control T. evansi in southern Africa.
