Population Dynamics and Treatment Strategies of Phytophthora infestans (late blight) in the Mid-Hills of Nepal

The fungus Phytophthora infestans is a major ubiquitous pest in solanaceous crops and causes great damages in the agricultural systems in Nepal. This is especially true in the cash crop orientated areas of the Mid-Hills and the Terai region, where potato and tomato cropping is a prominent income source of the rural population. This fact in combination with cheap and readily available pesticides is responsible for the frequent and perceived over-use of chemical plant protection agents. Based on this background a series of agronomic field trials in the Jhikhu-Khola watershed aiming at the optimisation of P. infestans treatment strategy was conducted. Within the field trials three different treatment strategies comprising both conventional and an alternative IPM approach were tested. Additionally a mathematical model for the simulation of the population dynamics of P. infestans was established, which is based on a universal epidemiological model with further specification for the late blight. The parameter estimation for the model was accomplished with uncontrolled field data. Using this model different treatment strategies were tested by introducing pesticide treatment strategies into the model. Based on both field trials and population dynamics simulation recommendations for an optimised conventional treatment strategy were developed.