![]() ![]() These plants should not be moved from their initial location, but should be placed gently into bags and sealed to prevent conidia from being released. Hostas that have severe cases of disease (lesions covering 50 percent of the leaves and with lesions all the way down the petioles) should be discarded. Dead tissue should be disposed of at a landfill. Diseased and senescent leaves should be collected and put into an enclosed trash container, as Botrytis still can produce conidia on dead tissue. If leaves fall to the ground of the shade house or onto the potting medium, these should be removed, as this tissue is still a suitable host for infection if the environment is wet and humid. Botrytis can thrive on living and dead tissueand it is therefore important, where practical, to remove leaves that are diseased or senescent (mature). This should be done on calm days to avoid excessive agitation of diseased leaves. Plants that already are affected should be isolated from tolerant varieties to reduce the amount of inoculum exposure to these plants. Sanitation practices are important management techniques for the control of botrytis blight. Botrytis conidia will not germinate on dry leaves and will be unable to infect plant tissue and reproduce. In addition, containers should be spaced far enough apart to promote air circulation and allow leaf drying to occur. In shade houses, if plants are being watered overhead, the irrigation should be timed to allow plants to dry before evening. Relative humidity should, if possible, be maintained below 85 percent by promoting conditions that enhance air circulation to prevent the formation of condensation on leaf surfaces. Therefore, preventing the accumulation of free moisture for extended periods on leaves is critical to Botrytis management. Like many other plant diseases, botrytis blightrequires free moisture on the leaf surface to proliferate. If conidia land on a leaf of a susceptible species of Hosta, but the environment is not favorable for infection, they may survive for up to three weeks and potentially infect and cause lesions even after the plants have been sold. In both fields and shade houses, Botrytis conidia are released in the atmosphere from mid-morning to mid-afternoon, coinciding with a rapid decrease in relative humidity. There clearly are differences in susceptibility among varieties, but these do not follow any particular characteristic of the plant, such as leaf texture, variegation or leaf size.īotrytis reproduces asexually by conidia (spores) that can be released and dispersed by plant agitation, such as wind, grower activity, irrigating, spraying pesticides and during harvest activities. In hostas, it appears the age of plants is not a factor in Botrytis infection. The lesions can spread down the leaf petiole and sometimes can be found beneath the soil surface. The dark fungus often can be seen on the underside of the lesion, especially early in the morning when the leaves are still wet. As the lesions mature and increase in size, rings can be seen within the lesions, which appear cinnamon to dark tan in color. In hostas, immature lesions appear mostly as water-soaked spots that increase in diameter to become circular spots with dark halos around the outside. In the presence of inoculum, when conditions are favorable for development of Botrytis and the plant is susceptible, botrytis blight can occur. In commercial nursery fields and shade houses, the practice of growing plants close together creates a humid environment, which is ideal for the development of botrytis blight. ![]() This year, the weather has been conducive for infection with the common plant pathogen Botrytis cinerea ( view photos). Check the label of any pesticide referenced to ensure your use is included. Editor’s note: This article is from the archives of the MSU Crop Advisory Team Alerts. ![]()
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