Grower perceptions of biotic and abiotic risks of potato production in South Africa

Abstract

Growers' surveys took place in all sixteen potato growing regions of South Africa in 2013 and 2014. The agro-ecological climate of these regions is diverse and potato is produced in rainy or dry seasons, in winter or summer seasons, or year round. Growers were asked how often in ten years crops suffered more than 25% yield losses due to extreme weather events related to precipitation events such as hail, floods and droughts, and to temperature-related events such as frost and heat waves. Simultaneously they were asked their opinion about occurrence and severity of diseases caused by potato viruses, fungi and bacteria and pests such as nematodes, tuber moths, aphids and leaf miners. Weather related hazards resulted in losses over 25% virtually each year in the Gauteng growing region due to hail, frosts and floods; losses occurred less than once every five years, for example due to extremely high temperatures, in the Sandveld area where growers take a risk by producing potatoes in hot summers. Regarding the biotic factors, every pest or pathogen assessed was reported to occur on at least one farm in each growing region. Countrywide the lowest frequency of 50% was recorded for powdery scab whereas the insects tuber moths, leaf miners and aphids were reported most frequently, by between 88% and 98% of the growers. The complex of silver scurf and black dot resulted in the greatest yield losses in all growing regions, followed closely by tuber moth, early blight and the blackleg / soft rot disease complex. Yield losses due to potato virus Y, potato leaf roll virus and aphids were not reported as being very severe. When the growers' perceptions of severity of biotic factors were accumulated, significant differences between the regions appeared, with the Eastern Cape most prone 1

Seed Potato Production Practices and Quality of Farm Saved Seed Potato in Kiambu and Nyandarua Counties in Kenya

“…Similar findings were reported by [19] revealing insect pests as the second most important problem after diseases in seed potato storage. However, [45] reported that potato tuber moth to be the most lethal pest unlike cutworms as reported in this study. In addition, [46] reported potato aphids as the most lethal field pests especially in the spread of viral diseases.…”

“…Pest attack leads to poor crop emergence and low plant stand count thus lowering yields [19]. Storage pests such as potato tuber moth can lead to reduction in marketability of the harvested produce, seed and yield losses [15,45].…”

Disease risk perception and diversity of management strategies by farmers: The case of anthracnose caused by Colletotrichum gloeosporioides on water yams (Dioscorea alata) in Guadeloupe

“…The protective effect of varietal admixture was nevertheless lower when admixture grain was too fine. Indeed, while use of varietal admixture or multi-lines can decrease pathogen epidemics, especially with regard to soil-borne diseases or splash dispersed fungi (Mundt, 2002;Trutmann et al, 1996), a too fine grain in admixture can translate in inefficient plant protection when admixture is at the individual plant level, since susceptible plants may thus grow within pathogen average dispersal distance (Gigot et al, 2014;Skelsey and Newton, 2014;Garett and Mundt, 1999), and our results suggest that fine scale varietal admixture are indeed associated with increased reports of anthracnose (Farmers' experience of anthracnose is lower when admixture is practiced in blocks and rows compared to when varieties are planted haphazardly or alternated one after the other). Admixture and cultivation of other species were rather expected effects of acknowledged beneficial practices (Mulumba et al, 2012), and they definitely seem to fit in a set of potentially sustainable strategies against the disease, provided the admixture grain be greater than dispersal ability of Colletotrichum.…”

“…Trutmann et al, 1996). and is usually dealing with preventive action upon the soil/climate correlates of disease (Sherwood, 1997;Trutmann et al, 1996). Some studies have also demonstrated that misattribution of disease symptoms could translate into inefficient actions and fail to prevent onset of epidemics (Kiros-Meles and Abang, 2008).…”

“…When a disease is observed to correlate to external causes (e.g., climate events such as rains), disease management may evolve (e.g. Trutmann et al, 1996). and is usually dealing with preventive action upon the soil/climate correlates of disease (Sherwood, 1997;Trutmann et al, 1996).…”