Abstract
Postharvest diseases are a major problem in guava crops as the symptoms normally appear during fruit ripening. This study aimed to detect and characterize the temporal dynamics and spatial patterns of the most important guava diseases in orchards with and without removal of crop residues as a sanitation practice. The experiment was conducted in an orchard of ‘Pedro Sato’ guavas, over two consecutive seasons, and data were collected from the flowering to the fruit ripening stage. In immature guavas treated with paraquat and ethrel, Colletotrichum spp. was detected from the 5th day of incubation. Anthracnose was detected in flowers at incidences higher than 50 % and black spot in fruit larger than 5.5 cm in length. The monomolecular and the exponential models provided the best fit to anthracnose and black spot incidence progress curve data, respectively. Both diseases showed a predominantly random spatial pattern in the orchard. The removal of crop residues reduced the rate of disease progress in at least one season, and was effective in reducing the areas under the quiescent disease progress curves (AUDPC) of anthracnose. Anthracnose incidence increased from 57 to 96 % and black spot from 1 to 48 %, respectively, at fruit maturation levels 1 and 3. A negative correlation was found between disease incidence and the color of the fruit skin (°h). Fruit harvested during the later maturation stages showed higher incidence of the diseases. Due to the wide distribution and early infection of quiescent diseases, starting at flowering, preventive management should consider disease monitoring and removal of crop residues.
Highlights
Guava is a highly perishable fruit and is, more susceptible to postharvest diseases
The removal of crop residues reduced the rate of disease progress in at least one season, and was effective in reducing the areas under the quiescent disease progress curves (AUDPC) of anthracnose
The major postharvest diseases affecting guava are anthracnose, caused by Colletotrichum spp., and black spot caused by Guignardia psidii Ullasa and Rawal (Fischer et al, 2011)
Summary
Guava is a highly perishable fruit and is, more susceptible to postharvest diseases. Once the skin of guava becomes edible, the presence of pathogenic injuries, even a small spot, can compromise fruit quality and make the product unfit for marketing. Such damage can occur during harvesting but subsequently, such as in packing houses, and at the grocery wholesaler, retailer and consumer stages. The major postharvest diseases affecting guava are anthracnose, caused by Colletotrichum spp., and black spot caused by Guignardia psidii Ullasa and Rawal (Fischer et al, 2011). Anthracnose and black spot are defined as quiescent diseases because the pathogens infect the fruit before harvest and remain latent until maturation when physical and physiological changes in the fruit favor pathogen development (Prusky and Lichter, 2007). Senescence is induced in herbicide-treated fruit and the symptoms are expressed
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