Botrytis cinerea fungus is active in early spring following the winter season when strawberry plants are broken down by natural elements into plant matter. Dormant mycelium, which is another name for fungus bodies, creates very small spores called conidia as soon as the temperature warms and the strawberry plant begins to flourish. The microscopic spores form on the previous year's strawberry crop debris.
The conidia produced are extremely tiny and lightweight so they are easily picked up by gusts of wind and scattered about. This process is similar to the way pollen is carried from one plant to the next by carriers such as bees so plants can reproduce, but the Botrytis cinerea fungus relies on wind to carry spores and ultimately prosper.
The goal of the conidia is to reach strawberry blossoms or strawberry fruit, and each is just as susceptible to the Botrytis cinerea fungus as the next. Strawberry harvesters may not know if portions of their crop are affected by the fungus because infected strawberry flowers may not show symptoms until a mature fruit is created. On some occasions, infected blossoms turn brown.
Moisture is necessary for the conidia to completely infect a strawberry flower and fruit. Moisture is prevalent on plants throughout the day because natural moisture comes from dew, fog and rain. Harvested strawberry fields are watered often, exposing the plant to water when natural water is not present. The infecting process is called germinating, and ideal weather conditions include temperatures around 70 to 80 degrees Fahrenheit.
The Botrytis cinerea fungus typically remains inactive through the green development fruit stage after strawberry blossoms are infected. As the strawberry begins to ripen and turn red, a fuzzy gray patch appears on the fruit. The gray mold is capable of developing while the strawberry is attached to the plant or as the strawberry matures in containers at the grocery store.
The Botrytis cinerea fungus survives the winter months a couple of ways. The fungus can reside inside a mature strawberry fruit that exhibited gray mold but was never picked from the plant. The strawberry falls to the ground and is slightly preserved by winter temperatures. The fungus activates again when the strawberry thaws in the spring. Another way the fungus survives the winter is in old plant debris. The fungus lives inside the plant, and when the plant withers and dies away for the winter, the fungus hibernates inside the plant matter until early spring.