![]() It is important to alternate between fungicide modes of action in order to limit the risk of developing fungicide-resistant Botrytis strains. Use only those fungicides that have been proven effective in research trials and apply them at the full labelled rate at seven-day intervals. Botrytis is best managed preventively and that includes using fungicides prior to a damaging outbreak. It is very likely that fungicides will need to play a central role as growers look to hold their crops due to Michigan’s “Stay Home” order. While these strategies are helpful, they are often not enough to eliminate gray mold during Michigan’s spring damp weather complete with overcast skies and fungicides may be needed.Ĭhoose effective fungicides, use their full rate, and apply often. Limit watering whenever possible and water at a time of day when the foliage can dry quickly. Relative humidity can also be reduced by slightly increasing the temperature via heating. Improving air flow to reduce relative humidity is also important. Sanitation reduces the spore load by removing dead and dying plants, leaves and flowers from greenhouse production areas. Preventing and controlling gray mold relies on a multi-pronged approach including cultural and chemical controls. ![]() Elements of the storm include overcast, chilly, wet weather, and maturing floriculture crops with flowers. There are times in the spring when Michigan growers face a perfect storm for a Botrytis outbreak. Dead tissue in the plant pot or on the greenhouse bench or floor can support gray mold and spore production. Botrytis usually becomes established and produces spores on older leaves near the moist soil surface and under the plant canopy and flowers. Small leaf spot symptoms may quickly combine into large blighted areas under high relative humidity and wet conditions. ![]() Penetration of the plant by Botrytis can be direct or indirect through natural openings or wounds. Infection requires water, which is needed for spore germination. Botrytis spores move by air and are carried to healthy plants where new infections begin. Flowers are especially prone to infection by the gray mold and when the infected petals fall to the foliage, leaf infections result. This pathogen infects many greenhouse ornamentals and is considered the second most important plant pathogen in the world.Ĭommon disease symptoms include leaf spots, blight and stem cankers with the fuzzy gray mold being a key way to identify the Botrytis culprit (Photo 1). The high relative humidity and lack of air circulation often found beneath the plant canopy are especially ideal for the pathogen Botrytis cinerea, commonly called gray mold. Sanitation is usually enough to manage these diseases on healthy established plants.The greenhouse environment provides ideal growing conditions for both plants and plant pathogens. Stem cankers, sunken discolored areas, can cause twisting and even death of the stem. These spots can be round and circular or irregular in shape. Ongoing sanitation, fall clean up and better weather is usually enough to keep this disease under control.Ī bit more information: Several other fungal diseases can cause spots on the leaves and stems of peonies. Only clean up during dry weather as moisture helps spread the blight. Remove infected parts and place in a paper bag for disposal. Look for the fuzzy gray growth and small black specs on the dead tissue. The bud blast and flower blights we see here may also occur on mums, dahlias, dogwood, geraniums, hydrangea, marigolds, and sunflowers. The disease attacks a variety of ornamental and edible plants and often is specific to the plant part infected. This fungal disease is most common in cool rainy as well as humid weather. Managing Botrytis Blight in the Gardenīrown buds that fail to open on peonies and some roses, especially the white and pink flowered varieties are likely the result of Botrytis Blight also known as Gray Mold. Your browser doesn't support the HTML5 video tag.
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