The content of this article in our Technical Ag section was prepared by Paulina Sepúlveda, an Agronomic Engineer of Chile Institute of Agricultural Research (INIA) in Rayentué for www.inia.cl. The content was revised and republished by FreshFruitPortal.com
Symptoms of gray mold in table grapes are visible in various aerial organs of the plant, flowers, tender shoots and berries from veraison to harvest and also postharvest.
Infected flowers do not set and remain attached to the rachis, the remains of which may remain attached to the pedicel, favoring infection. The berries acquire a brown coloration and may fall or remain as foci of infection. A soft and watery rot develops in berries.
Initially, a brown coloration and loose skin are evident. A brown-gray mold is observed covering the surface of the berries and may penetrate internally. The mycelium has the ability to actively penetrate other berries, forming Botrytis "nests" that can involve the entire bunch.
It is a disease whose conidia are spread by wind and water. Secondarily it is spread by contact between diseased and healthy berries, forming "nests".
It occurs saprophytically on mummified fruit or decaying plant material at field level. It also survives as mycelium on dormant bark and buds. It can resist adverse conditions in resistant structures called sclerotia on vine shoots and petioles.
Control measures should be done in the critical periods that are flowering, to lower inoculum load and then between veraison and harvest, through the integration of several methods. An appropriate use of fungicides together with cultural management can efficiently control the disease. It is recommended to remove and destroy plant material in the field that may harbor inoculum of the pathogen.
Since the fungus has a great capacity to develop resistant races, it is necessary to carry out an adequate rotation of fungicides to maintain their effectiveness over time.
In the case of fungicides with mixtures of active ingredients, their use is increasingly limited, due to the fact that a maximum of four or five active ingredients are tolerated in destination markets.
Active ingredients registered in major export markets include Fenexamid, Iprodione, Tebuconazole, Boscalid, Fludioxonil and other fungicide mixtures.