SHORT-TERM AND LONG-TERM ECONOMIC-IMPLICATIONS OF CONTROLLING CRENATEBROOMRAPE (OROBANCHE-CRENATA FORSK.) IN BROAD BEAN (VICIA-FABA L.) UNDER VARIOUS MANAGEMENT STRATEGIES

An economic model is described and used to investigate the short-and l ong-term implications of controlling crenate broomrape (Orobanche cren ata Forsk.) infestations in broad bean (Vicia faba L.) under different management strategies. These include no use of herbicide, applying he rbicide once after an infection severity (IS: number of emerged broomr ape m(-2)) greater than or equal to 0.1, and applying herbicide every year. Crenate broomrape population evolution was affected by initial I S (ISo) at the time of implementing the strategy, regardless of the ma nagement strategy adopted. Non-application of herbicide was satisfacto ry when initial infection was very low (ISo less than or equal to 0.1) resulting in average annualized benefits (AB) of about 600 and 505 US $ ha(-1), after 3 and 9 years for early sowing dates, respectively. A pplying herbicide once did not control parasite populations adequately and could only represent an acceptable low-cost alternative in the lo ng term when IS less than or equal to 1 giving an AB of about 653 and 630 US $ ha(-1) after 3 and 9 years for early sowing dates, respective ly. Annual application of herbicide was the best strategy against broo mrape at any ISo to minimize crenate broomrape populations and obtain maximum net benefits per year regardless of broad bean cropping freque ncy. A sensitivity analysis was performed to determine the effect of c hanging the values of the main economic parameters (efficacy of the he rbicide, expected yield, fixed and herbicide costs). In general, sensi tivity coefficients were between 0.5 and 1, herbicide cost being the p arameter which exerted the least effect on AB in all management strate gies. Generally, an ISo less than or equal to 1 requires broomrape her bicide treatments in all subsequent broad bean crops in order to ensur e economic benefits. (C) 1998 Elsevier Science Ltd. All rights reserve d.