Effect of Postharvest Treatments on Stemphylium Rot of Papaya

Abstract

On the inoculation site, a small block Glazener, J. A., Couey, H. M., and Alvarez, A. 1984. Effect of postharvest treatments on of agar with fungus (2 X 2 mm) was Stemphylium rot of papaya. Plant Disease 68:986-988. placed on 1) a slash wound made with a razor blade, 2) a pinpoint wound made The size of lesions caused by Stemphylium lycopersici on papaya (Carica papaya) fruits was with an insect needle, and 3) an affected by type of wounding, fruit maturity, duration of postharvest hot-water treatment, and unwounded area. In the experiments duration of cold storage. A hot-water immersion treatment resulted in larger lesions than a comparing spray and immersion treathot-water spray. Susceptibility to infection increased with increasing maturity. ments and effect of incubation time, two wounded and two unwounded sites were inoculated on each fruit. Fruits were A storage disease occurred on fruit of days of incubation at 25 C. Controls incubated in moistened plastic bags for 48 papaya (Carica papaya L. 'Kapoho received the same treatment with hr, then the plastic bags were removed Solo') when refrigerated during transport omission of a hot-water incubation. The and the fruit stored in vented plastic bags to distant markets (1). Affected fruit had experiment was replicated six times. in fiberboard boxes at 10 C for 0, 1, or 2 round, black, velvety lesions surrounded Papaya fruits were harvested in early wk. Each sample consisted of 10 fruits. by a maroon ring. The causal fungus was morning and used in experiments the After refrigeration, the fruits were left at identified as Stemphylium lycopersici same or following day. Fruits were room temperature for another 5 days Yamamoto (1). selected visually in the colorbreak, one- before measuring the lesions. All Conditions permitting infection of quarter ripe, and one-half ripe stages and experiments were replicated five or six papaya fruit by S. lycopersici are not well measured individually at the inoculation times. All experimental data were understood. Couey and Farias (5) found site with a Hunter colorimeter stan- evaluated by analysis of variance. A splitan increase in the incidence of dardized with the white master standard plot technique was used where necessary Stemphylium sp. after hot-water (LL = 92.50; aL = -0.9; bL = -0.1). A (2). Frequency of infection of the immersion. In our study, hot-water heat treatment was given by either unwounded fruit sites was analyzed by treatments of fruit at various levels of running the fruit through a hot-water calculating the G statistic as described by maturity and lengths of refrigeration spray (54 C) with equipment similar to Sokal and Rohlf (8). were compared for their influence on that used by Hundtoft and Akamine (6) diameter of S. lycopersici lesions. or immersing the fruit in a hot-water tank RESULTS