25 Jun 2024
Citrus Black Spot

The Effects of Postharvest Treatments and Sunlight Exposure on the Reproductive Capability and Viability of Phyllosticta citricarpa in Citrus Black Spot Fruit Lesions

Citrus black spot (CBS) is caused by Phyllosticta citricarpa, which is classified as a quarantine organism in certain countries whose concerns are that CBS-infected fruit may be a pathway for introduction of the pathogen. This study evaluated the reproductive capability and viability of P. citricarpa under simulated conditions in which the whole fruit, peel segments, or citrus pulp with CBS lesions were discarded. Naturally infected ‘Midknight’ Valencia orange and ‘Eureka’ lemon fruit, either treated using standard postharvest sanitation, fungicide, and wax coating treatments or untreated, were placed into cold storage for 5 weeks (oranges at 4 °C and lemons at 7 °C). Thereafter, treated and untreated fruit were incubated for a further 2 weeks at conditions conducive for CBS symptom expression and formation of pycnidia. The ability of pycnidia to secrete viable pycnidiospores after whole fruit and peel segments or peel pieces from citrus pulp were exposed to sunlight at warm temperatures (±28 °C) and ±75% relative humidity levels was then investigated.

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25 Nov 2018
Botrytis cinerea

Rind distortion of lemon caused by Botrytis cinerea Pers

R. A. Fullerton, F. M. Harris & I. C. Hallett
(1999) Rind distortion of lemon caused by Botrytis cinerea Pers, New Zealand Journal of Crop and Horticultural Science.

The infection process by Botrytis cinerea Pers on lemon fruits (Citrus Union (L.) Burm.), and development of rind distortion are described. Infections occur on juvenile fruitlets soon after petal fall from hyphae growing over the surface of the fruit from adjacent colonised flower debris. The hyphae form compact infection cushions at their tips. There is a collapse of epidermal cells and several layers of underlying cells in the vicinity of the infection cushion, leading to the formation of small necrotic pits on the surface of the fruit. As the fruitlets grow, there is generalised hyperplasia in a zone up to 20 cell layers deep in the region of the necrotic pits, leading to conspicuous outgrowths on the fruit surface.

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