![]() ![]() ![]() A timer could be set to activate the fans. In greenhouses with fans, the fans should be activated and operated for a few minutes and then the heater turned on to bring the air temperature up. Cooler air coming in from the outside will have lower relative humidity. The warm air will rise and escape from the greenhouse through the vents. Warm air will hold more moisture than cool air. John advises, in greenhouses with vents, the heat should be turned on and the vents opened an inch or so. Neither practice alone is as efficient as both combined.Īccording to John Bartok, University of Connecticut Extension Professor-Emeritus, the method and time it takes for heating and venting will vary according to the heating and ventilation system in the greenhouse. Heating is necessary to bring outdoor air up to optimum growing temperature, and increases the capacity of the air to carry moisture, thus avoiding condensation. Ventilation allows the exchange of moist greenhouse air with drier air from outdoors. Heating and Venting Greenhouses to Lower Humidityĭuring cool times of the year, when a greenhouse is being heated, another practice to reduce humidity is to use a combination of ventilation and heating.Water just enough to prevent excess water on the floor, and water early enough in the day to allow plant surfaces to dry before evening reduces humidity and will help manage Botrytis. Increasing plant spacing to provide a less dense canopy will also help by allowing more air circulation and better fungicide coverage. Using drip irrigation or watering plants at the base instead of sprinkling or watering overhead will help to prevent Botrytis and many other leaf spot diseases. The key to suppressing Botrytis is to keep the plant canopy dry, especially from dusk until dawn. ![]() Once Botrytis develops, it cannot be effectively controlled with fungicides alone. Botrytis appears most often in spring and fall, because warm days followed by cool evenings result in condensation on plant surfaces. Colonization of plant tissues takes place at a wide range of temperatures, but 60-75☏ is optimum. Spore germination and infection depends on a film of moisture for 8 to 12 hours, relative humidity of 85% or greater, and temperatures 55-65☏. Like other fungi, Botrytis has a range of temperature and relative humidity that is necessary for spore germination, infection, and disease development. Prolonged periods of cool, cloudy weather create an ideal environment for Botryis infections during production in a full greenhouse or out in the field. The fungus will also colonize dead or dying tissues anywhere conditions are right- in greenhouses, the field, packing sheds, coolers or during shipping. During storage and shipping, Botrytis causes blight or blast on leaf and flower buds. These less obvious symptoms show as tan colored spots on leaves or cankers on stems that can eventually cause entire branches of plants to wilt, while the rest of the plant appears healthy. During production, blossom and bud blight often precede and lead to infections on leaves and stems. Petals of badly infected flowers stick together and become matted. Aging flowers are particularly susceptible. The fungus becomes established in flower petals and appears as irregular, enlarged, water-soaked or tan spots that eventually produce fuzzy gray fungal growth. Flowers petals provide an excellent food source for the production of spores. Signs and SymptomsĪlthough Botrytis attacks plants and flowers at any stage, tender new growth and aging or senescent tissues are preferred. Botrytis is often referred to as gray mold because it produces abundant fuzzy gray spores on the surfaces of infected tissues. There are several species of the fungus Botrytis, but Botrytis cinerea has the largest host range. Botrytis is one of those problems that can occur at any time conditions are right. ![]()
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