Economic comparison of phytophthora root rot control methods

Abstract

The economics of strategies for control of root rot on chile (or chilli) peppers ( Capsicum annuum) caused by Phytophthora capsici were analysed. The strategies investigated were alternate-row irrigation, every-row irrigation and chemical treatments with alternate-row irrigation. The chemical treatments were metam-sodium, copper sulfate and metalaxyl. Three years of data, 1989–1991, were analysed for green chile, and four years of data, 1988–1991, for red chile. The linear programming model results indicated that, to maximize returns to fixed resources without regard to risk, all resources should be allocated to every-row irrigation in 1989 and 1990 and when yields across all 4 years are considered. In 1988 and 1991, the yield benefits of alternate-row irrigation justified the cost of building the borders, although in 1988 every-row irrigation was not evaluated. For green chile, the optimal strategy was alternate-row irrigation in 1989, 1990, 1991 and when yields across all years are considered. The quadratic programming model showed that to reduce variance of returns in red chile production, alternate rows should be watered and copper sulfate applied via the irrigation water. To reduce variance of returns in green chile production, alternate-row irrigation with metalaxyl is recommended. Sensitivity analysis conducted on chile prices and labour and chemical costs showed that the optimal farm plans were insensitive to changes of 15% above and below the market prices and costs.