Interaction of the fluctuation of the population density of sweet potato pests with changes in farming practices, climate and physical environments: A 11-year preliminary observation from South-Kivu Province, Eastern DRCongo

Sweetpotato is a major food security crop grown in eastern Democratic Republic of Congo. Its production is however limited due to high prevalence of pests and diseases among other abiotic and biotic factors. A study was designed to aid understanding the knowledge of farmers about pests and their perception about climate variability impacts, as well as documenting the phenology of sweetpotato pests (pest population dynamics) in relationship with weather factors. The paper aimed at determined which climatic factors may be used as best predictors of the different status of pest populations (declines, outbreaks). Farmer based data was obtained using a semi structured questionnaire administered to several of farmers. Population dynamics of sweetpotato pests were monitored year-round from 2005 to 2015 in South Kivu province, eastern DRCongo. Field monitoring (visual counts) observations (population dynamic of different soil-dwelling and surface dwelling arthropods visiting sweetpotato fields) combined with a survey of farmers’ knowledge on sweetpotato pests and their practices in the management of these pests in South- Kivu Province were conducted for 11 years. Monitoring (with field observations and counts) was carried out in fields under different farming practices (monocropping and inter-cropping) in sites located at different altitudes. Similarly, data for climatic factors, for the same period, were collected from Lwiro Research center. Regression models were applied to understand the linkages between environmental factors (rainfall and temperature) and pest population dynamics. The results indicated that different varieties (local and improved ones) of sweetpotato are grown three times (3 seasons) per annum under various cropping systems (sole crop, mixed crops) in various agroecological zones at different altitudes. Various arthropod species visit the crop at its different stages of development including classically known pests (Acraea acerata, Cylas spp.) or as vectors of diseases (Bemisi tabaci, Aphis spp.). The results indicated a high fluctuation in the population density of different pests. The change in the population dynamics were characterized by gradual increase in the populations during rainy seasons followed by decline during dry seasons (hot months of the year). Significant (P