Premature Apple Fruit Drop: Associated Fungal Species and Attempted Management Solutions

Abstract

The aim of this research was to determine the incidence and possible causal pathogen(s) of premature apple fruit drop (PAFD), and also to assess some fungicides for controlling the disease organisms, in order to promote a sustainable system in orchards. The prevalence and natural incidence of apple fruit drop in cv. Anna was assessed during the 2017–2018 growing seasons in Nubaria and Cairo–Alexandria regions, Egypt. Phytopathogenic fungi were isolated from dropped fruit, and four fungicides, pyraclostrobin + boscalid, difenoconazole, carbendazim, and thiophanate methyl, were tested against the diseases in vitro and under naturally occurring infections in the field. Several phytopathogenic fungi, including Alternaria alternata, Cladosporium cladosporioides, Fusarium semitectum, and Penicillium spp., were associated with apple fruit drop. A. alternata was the most frequently isolated fungus occurring during the investigation. Pathogenicity tests confirmed that the maximum percentage of apple fruit drop was noted when petioles and fruits were inoculated with mixed fungal pathogens using branch sections with fruit. In vitro tests showed that the fungicides had a variable effect against the fungal isolates depending on the concentration used. All fungicides completely inhibited the growth of A. alternata, C. cladosporioides, and F. semitectum at 400 mg·L−1. Under naturally occurring infections, thiophanate methyl applied at fruit set had the greatest effect (81.68%) against PAFD, followed by difenoconazole (73.76%), pyraclostrobin + boscalid (70.29%), and carbendazim (66.34%). The results indicated that PAFD may in part be a result of diseases caused by certain phytopathogenic fungi, which could be controlled using a number of fungicides applied at the beginning of fruit set.

Resistance against phomopsis leaf blight disease induced by potassium salts in strawberry plants

“…Likewise, potassium phosphates proved to be effective against phytopathogenic fungi (Arslan 2015;El-Fawy and El-Said 2018). Yet, until recently, such safe salts have not been reported as management solutions for several apple diseases in Egypt (Youssef and Roberto 2020). The inhibitory mechanisms of bicarbonates were explained in terms of hydrogen ion concentration effect of the salts which demonstrated a profound inhibitory effect on sclerotia and conidia germination of Sclerotium rolfesii and S. fuliginea, respectively (Punja and Grogan 1982;Homma et al 1981).…”

Application of Plant Extracts to Control Postharvest Gray Mold and Susceptibility of Apple Fruits to B. cinerea from Different Plant Hosts

“…To evaluate the susceptibility of apple fruits to different plant host isolates of B. cinerea , the number of infected lesions caused by strawberry B. cinerea and apple B. cinerea on apples treated with extracts was counted at 7 and 9 DAI, and disease incidence was calculated using the formula adjusted based on Youssef and Roberto [ 48 ]: disease incidence = (number of infected lesions/total number of assessed lesions) × 100.…”

Apple production systems and post-harvest management across selected locations of North Shewa Zone, Ethiopia

“…This indicated that there is a huge amount of loss of production due to fruit drop, which in turn could be associated with poor handling of the plants. The common causes of fruit drop are mainly poor nutrition, diseases attack, poor tree pruning, and inaccurate irrigation [39][40][41][42] . As indicated above in Tables 5 and 6, poor nutrition, and tree management are the most common futures across the study locations.…”