RESUMEN

Phlyctema vagabunda is responsible for significant postharvest losses in 'Cripps Pink' apples in South Africa. The first objective of this study was to determine the presence and incidence of P. vagabunda on stored commercial 'Cripps Pink' apple in five major pome fruit growing regions in the Western Cape. As the fungus remains latent until postharvest, the second objective was to develop a rapid molecular detection tool to determine the presence of P. vagabunda on asymptomatic 'Cripps Pink' apples from two commercial orchards. Postharvest disease incidence in 'Cripps Pink' apples in the Western Cape ranged from 0 to 73% in the 2010/2011, 0 to 6% in 2011/2012, and 0 to 30% in 2012/2013 seasons. P. vagabunda spores were also detected on 'Cripps Pink' fruit from December to February and from March to April. In December and January, P. vagabunda spores were detected on the 'Hillieri' crab apple pollinator. The knowledge that P. vagabunda conidia are present on the surface of 'Cripps Pink' apples and 'Hillieri' crab apples during the growing season could be applied to improving current management practices in the orchards.

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RESUMEN

The South African apple industry currently relies entirely on chemical fungicides to control apple scab (Venturia inaequalis). In this study, the effectiveness of sanitation strategies in reducing scab incidence and severity in South African orchards was evaluated. Over three seasons, leaf shredding with no fungicide sprays was tested against a nonsprayed, nonshredded negative control, a positive control that followed a commercial fungicide program, and a combined treatment of a commercial fungicide program with leaf shredding. Two treatment replicates were applied in a randomized block design in each of two orchards. Scab incidence and severity on fruit and leaves were assessed weekly from green-tip until fruit-set in the following spring. Pooled data from the 3 years revealed that fruit scab incidence and severity and leaf scab severity (51, 55, and 39%, respectively, P < 0.05) and leaf scab incidence (33%, P < 0.1) were significantly lower in the leaf-shredding treatment than in the negative control. This is the first study to evaluate the effect of leaf shredding in reducing scab in South African orchards. Results indicate that this treatment is highly effective and should be integrated into scab management strategies in future, but should be customized to suit South African orchard conditions.

RESUMEN

Postharvest decay causes losses to commercial pear industries. The incidence of decay in air and controlled-atmosphere (CA)-stored 'd'Anjou' pear fruit was investigated, and the effect of a prestorage thiabendazole drench on decay in CA-stored fruit was determined. In air storage, bull's-eye rot (31.37%) was most prevalent in 1996, whereas incidence of gray and blue mold (1996 and 1997) and bull's-eye rot (1997) were similar. Mucor, Alternaria, and Coprinus rot levels were low. Incidence of stem-end gray mold (2.58%) was significantly higher than calyx-end (0.73%) and puncture gray mold (0.61%). Incidence of gray mold (2.26%) was higher than all other decay in nondrenched CA-storage, and incidence of other decay types were similar. Incidence of puncture gray mold (1.13%) was higher than stem-end gray mold (0.84%), which in turn was higher than calyx-end gray mold (0.36%) in nondrenched CA-storage. Incidence of gray mold (1.04%) in CA-stored fruit was reduced by a prestorage thiabendazole drench. Drenching reduced stem-end (0.34%) and puncture gray mold (0.40%) but had no effect on all other decay or the total decay incidence. These results support the current recommendations of a single postharvest application of thiabendazole to control gray mold in 'd'Anjou' pear fruit.

RESUMEN

The aims of this study were to examine the sources and population sizes of Botrytis cinerea and Penicillium spp. in 'd'Anjou' pear orchards, packinghouses, and storage, and to determine the relationship between population sizes and postharvest decay. Densities of B. cinerea ranged from nondetectable to 4.0 CFU/cm2 on fruit, nondetectable to 3.1 CFU/liter in orchard air, and nondetectable to 1,167 CFU/g in orchard litter. The majority of packinghouse air and orchard soil samples collected yielded no B. cinerea inoculum. Densities of Penicillium spp. ranged from nondetectable to 2.7 CFU/cm2 on pear fruit, nondetectable to 3.13 CFU/liter in orchard air, nondetectable to 11.8 CFU/liter in packingline air, nondetectable to 3.9 CFU/liter in cold-storage air, 38 to 431 CFU/g in orchard soil, and 131 to 1,128 CFU/g in orchard litter. The mean incidence of gray mold in stored d'Anjou pear fruit ranged from 0.7 to 10.7%. Incidence of blue mold ranged from 0 to 16.5%. Significant positive correlations were observed between decay and fruit surface populations of B. cinerea and Penicillium spp. In conclusion, inoculum levels of these important postharvest pathogens in orchard and packinghouse air, and orchard soil and litter, cannot be used as indicators of postharvest decay; whereas the inoculum level on fruit surfaces may be a useful predictor of decay.

RESUMEN

Botrytis cinerea is responsible for a major portion of postharvest decay in winter pears in the Pacific Northwest. The baseline sensitivity levels (mean EC50 values) of a wild-type B. cinerea population to thiabendazole and iprodione were 6.66 and 0.56 mg/liter, respectively. B. cinerea from commercial orchards not treated with a benzimidazole had significantly lower incidence of resistance (0.59%) to a discriminatory concentration of thiabendazole at 10 mg/liter than did isolates from orchards in which benomyl had been applied for experimental purposes (16.0%), unsprayed control trees in benomyl-sprayed orchards (5.34%), and isolates from packinghouses where thiabendazole was applied as a prestorage drench or packingline spray (3.23%). The mean EC50 value of isolates in the wild-type population was lower than those of resistant isolates from all other sources. High-level thiabendazole resistance (EC50 > 100 mg/liter) was found in 0.20% of isolates from unsprayed commercial orchards, 9.33% of isolates from benomyl-sprayed orchards, and 2.67% of isolates from unsprayed control trees in these benomyl-sprayed orchards. In isolates from packinghouses where a thiabendazole line spray was applied, 1.52% had high-level thiabendazole resistance. All isolates from all pear-related sources tested were sensitive to iprodione at 10 mg/liter. This study provides evidence supporting current recommendations of a single postharvest application of a benzimidazole to control decay caused by B. cinerea, and no application of benzimidazole fungicides in the orchard.