Oral Technical Session: Fruit Pathogen Epidemiology

11-O

Effect of inoculum concentration on development of anthracnose fruit rot of strawberry cultivars in detached fruit and field experiments.
B. B. FORCELINI (1), N. A. Peres (1), F. P. Goncalves (2)
(1) University of Florida, Wimauma, FL, U.S.A.; (2) Instituto Agronomico do Parana, Londrina, Brazil

Florida is the largest producer of winter strawberries in the world. Anthracnose Fruit Rot (AFR), caused by Colletotrichum acutatum, can greatly affect production if not controlled. Cultural practices such as the use of certified pathogen-free plants and less susceptible cultivars are important tools for control AFR. The susceptibility of two strawberry cultivars (‘Strawberry Festival’ and ‘Camarosa’) was compared in a detached fruit experiment using six inoculum concentrations (0, 10², 10³, 10⁴, 10⁵ and 10⁶ conidia/ml). The experiment was arranged in a completely randomized design with six treatments (inoculum concentrations) per cultivar and four replications. Fruit were inoculated with a 5-µL droplet and kept in plastic boxes to maintain humidity. AFR incidence was assessed on fruit for 9 days and the experiment was repeated twice. There was a high correlation for the disease incidence from the detached fruit assay and field experiments conducted in the previous season. Disease incidence was lower on ‘Strawberry Festival’ than on ‘Camarosa’ independent of the inoculum concentration. Moreover, the minimum inoculum concentration for symptom development was 10⁴ for ‘Camarosa’ and 10⁵ for ‘Strawberry Festival’. The detached fruit assay allows better control of the environmental conditions and is more practical to perform than field experiments.