Phytoparasitica (1996) 24, 140-141

Galit Sharabani, D. Shtienberg, Y. Elad, A. Dinoor and H. Yunis (1996)
Development of graymold in sweet basil
Phytoparasitica 24 (2), 140-141
The 17th Congress of the Israeli Phytopathological Society, February 19-20, 1996 (Bet Dagan, Israel), poster
Abstract: The cultivated area of herb plants has increased markedly in recent years in Israel. The leading crop is sweet basil (Ocimum basilicum), most of which is exported, mainly to the European community. Sweet basil is severely infected by gray mold, caused by Botrytis cinerea. The pathogen may develop on the packed bunches during shipment to the target market, resulting in rot of the entire package. However, more severe damage is caused when the pathogen develops in the greenhouse, and during severe epidemics the entire crop may be devastated. The demand for products free of pesticide residues forces the growers to avoid unnecessary application of fungicides for the suppression of gray mold. Many growers do not apply any fungicides and tolerate the losses imposed by the pathogen. The objective of this research was to study the epidemiology of gray mold in order to develop an efficient agrotechnical procedure for its management. Observations of disease development in commercial greenhouses revealed that infections occur on the stem cuttings, soon after harvest. The disease then progresses on the stem, killing all leaves and secondary buds. When it reaches the main stem, at the bottom of the plant, the entire plant dies. It was noticed that disease outbreaks occurred when harvesting was carried out during rainy periods, but not when harvesting was done a few days before or after rains. The reason for this was studied in a set of experiments conducted under controlled environment conditions, in growth chambers and in greenhouses. First, changes in host receptivity to infection, as a function of the time from harvest, were studied. The stem cuttings were highly receptive to infection soon after harvest, but receptivity diminished gradually with time, and by 48 h after harvest most of the stem cuttings we tried to infect with spores of B. cinerea, remained uninfected. Observations under a scanning electron microscope revealed that an opaque layer developed over the cut area within a few hours after harvest. Five days after harvest, the cut area was evenly covered with that layer. Conidia of B. cinerea germinated and penetrated directly to the cut area of the stem soon after harvest, whereas they did not germinate when applied 5 days after harvest. Assuming that optimal conditions for B. cinerea infection prevail in the greenhouse when harvesting is done during rainy periods, and based on the above findings, we hypothesized that refraining from harvesting during rainy days might reduce markedly the incidence of gray mold. This hypothesis was tested in an experiment conducted in an experimental greenhouse. It was found that harvesting 5 days after heavy rains reduced significantly (by 75%) the incidence of gray mold in comparison with plots harvested one day after or during the rains. The conclusion is that it may be possible to reduce the losses induced by gray mold in basil by appropriate timing of the harvests.
(The abstract is excluded from the Creative Commons licence and has been copied with permission by the publisher.)
Database assignments for author(s): Yigal Elad, Dani Shtienberg

Research topic(s) for pests/diseases/weeds:
transmission/dispersal of plant diseases
population dynamics/ epidemiology

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Pest and/or beneficial records:

Beneficial	Pest/Disease/Weed	Crop/Product	Country	Quarant.
	Botrytis cinerea	Basil (Ocimum)	Israel