1. Unit for Environmental Sciences and Management, North-West University, Potchefstroom, South Africa
2. Agricultural Research Council-Tropical and Subtropical Crops, Mbombela, South Africa
3. Agricultural Research Council-Plant Health and Protection, Queenswood, South Africa
4. Department of Zoology, University of Johannesburg, Johannesburg, South Africa
5. Laboratory of Tropical Crop Improvement, University of Leuven, Leuven, Belgium