Abstract:
A set of daily weather data simulations for 1961 to 2050 were used to
calculate past and future trends in pest and disease pressure in potato cropping
systems at three agro-ecologically distinct sites in South Africa: the Sandveld, the
Eastern Free State and Limpopo. The diseases and pests modelled were late blight,
early blight and brown spot, blackleg and soft rot, root-knot nematodes and the
peach-potato aphid Myzus persicae (as indicator of Potato virus Y and Potato leaf
roll virus). The effects of climate on trends in relative development rates of these
pathogens and pests were modelled for each pathogen and pest using a set of
quantitative parameters, which included specific temperature and moisture requirements
for population growth, compiled from literature. Results showed that the
cumulative relative development rate (cRDR) of soft rot and blackleg, root-knot
nematodes and M. persicae will increase over the 90-year period in the areas under consideration. The cRDR of early blight and brown spot is likely to increase in the
wet winter and wet summer crops of the Sandveld and Eastern Free State, respectively,
but remains unchanged in the dry summer and dry winter crops of the
Sandveld and Limpopo, respectively. Climate change will decrease the cRDR of late
blight in all of the cropping systems modelled, except in the wet winter crop of the
Sandveld. These results help to set priorities in research and breeding, specifically in
relation to management strategies for diseases and pests.
