Temporal progress and spatial patterns of quiescent diseases in guava influenced by sanitation practices

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 5 th 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.

Detection and epidemiological progress of quiescent avocado diseases

“…In the last evaluation, when fruits were in commercial harvest stage, the incidence rates of lasiodiplodia and fusicoccum/neofusicoccum rots were 9.5 and 3.5%, respectively, considering the average of seasons. In 'Pedro Sato' guavas, lasiodiplodia and fusicocum rots were also detected in immature fruits and, similarly to the present study, anthracnose was the most prevalent disease (FISCHER et al, 2017). In some avocado orchards in Chile, the incidence of stem-end rot reached values superior to 20% (SOTO, 2015).…”

“…The initial incidence of anthracnose was high, with 60 and 86% of the open flowers diseased in both crop seasons, respectively (Figure 2). Similarly to avocado, 50% guava flowers showed Colletotrichum spp., reaching 100% fruits of 3cm length (FISCHER et al, 2017). The percentage of conidial germination and appressorium formation for C. gloeosporioides do not differ among guavas of different ages (MORAES et al, 2015).…”

“…Immature guavas treated with paraquat and ethrel showed Colletotrichum conidia after 5-day incubation, i.e. two days earlier compared to control treatment (FISCHER et al, 2017). However, production and commercialization of the herbicide paraquat will be forbidden in Brazil from September 22 nd , 2020 (ANVISA, 2018).…”

“…There is a methodology already available to detect quiescent infection by Colletotrichum spp. in mango (PARAMASIVAN et al, 2009), papaya (SILVA, 2010) and guava (FISCHER et al, 2017), as well as by Botryosphaeria dothidea in apples (VALDEBENITO-SANHUEZA et al, 2005), which consists in treating the fruits with ethrel (ethylene precursor) or paraquat. Ethylene promotes fruit ripening, leading to biochemical and physiological changes necessary for the fungus to pass through the quiescence stage and colonize the fruit.…”

Agricultural and economic characterization of guava production in Brazil

“…However, logistics flow management should be much simplified, theoretically, if periodic rather than continuous pruning is employed. Also, due to the wide distribution and early infection of quiescent diseases in guava, starting at flowering, preventive management should consider disease monitoring and removal of crop residues (Fischer et al, 2017;Prusky and Lichter, 2007).…”