The potato leafminer was introduced into South Africa in 2000. Initially
severe yield losses of up to 70% were experienced by potato farmers in the
Sandveld region. After the registration of a few insecticides, the problem
subsided during the following years. However, during some seasons the problem
seems to become serious again; insecticides apparently are not always able to
control the leafminer satisfactory. The potato leafminer attacks nearly all
vegetables, but on potato it is particularly severe (Read more...)
The tomato leafminer, Tuta absoluta, originally from South America, was
reported for the first time from South Africa in August 2016. Tuta absoluta is
mainly a pest of tomato. Other crops that act as secondary hosts include
potato, eggplant, Capsicum peppers, and Cape gooseberry. The risk that Tuta
absoluta poses to these secondary host are currently uncertain. In South
Africa, Tuta absoluta is better known under its scientific name than under its
common name. (Read more...)
Sweet Potato Weevil
Sweetpotato weevil, Cylas formicarius (F.) is known as the most important insect pests which, attack sweetpotato plants. The weevil attacks all parts of the plant, adults feed directly on vines, and larvae tunnel into the roots, causing extensive damage both in field and storage. The larvae when entering the flesh of the sweetpotato stimulate the production of substances that spoil the flavour and appearance of the cooked sweetpotato.
Furthermore, the pest damage the sweetpotato roots while the crop is growing as well as during storage. In the field the insect lays eggs on the stems and on exposed roots. Although chemical and cultural control are currently been used, at present, biological control is an attractive option in agriculture due to reduction in use of agro-chemicals which are associated with resistance development and environmental concerns. Beauveria bassiana, a virulent pathogen found to control the banana weevil, was tested in field trials at the ARC for control of the sweet potato weevil (Cylas sp.).
The product used was EcoBb and is commercially available. The results showed that spraying the plants every 2 weeks with EcoBb for four months after planting at a rate of 10 g/100 litre water, provided as good control as sprays with registered chemical Deltametrin.
Beauvaria bassiana can thus be considered by producers is an environment-friendly control method for sweet potato weevil.
Contact: Dr Diedrich Visser
Hlerema, I.N., Laurie, S.M. and Eiasu, B. 2017. Preliminary results of biological control of the sweet potato weevil using Beauveria bassiana in South Africa. Open Agriculture 2:595-599.
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