Disease pressure in an environmentally controlled hydroponic greenhouse is minimal compared to field conditions, but the threat is never completely eliminated. If growers don’t keep a watchful eye on the internal climate, diseases could proliferate rapidly and even devastate the crop.
Greenhouse crops are not typically susceptible to many of the same diseases that threaten field crops. The most common diseases that pose a threat can be detrimental to salability if left unchecked. Gray mold (Botrytis cinerea) is one of those diseases, especially in vegetable production.
What to look for
From geraniums to tomatoes, gray mold has a long list of potential hosts. The initial infection originates on decaying plant parts such as fallen flower petals or leaves and stems. A noticeable gray-brown furry mold will develop on decaying parts while small white rings may appear on fruit. With the ability to also attack any above-ground parts, the infection may be difficult to detect until the damage has already been done. Gray mold develops under cool (65°F-75°F) temperatures, high humidity, and free-standing water, which can easily occur if the greenhouse environment is not properly monitored. These conditions can also stress plants and can lead to greater disease susceptibility.
How to prevent
Preventing gray mold ultimately comes down to maintaining an appropriate environment and greenhouse cleanliness. Perform monthly checks to be sure all fans and vents are working properly and be sure to clean up plant debris on a daily basis. Gray mold spores survive in the debris, waiting for the perfect conditions to germinate and wreak havoc. If motors break, shutters stick, or clouds come out, an unsuspecting grower could end up with gray mold in no time.
CropKing offers a variety of products to aid in the prevention and control of gray mold. Green-Shield is a disinfectant and algaecide used to disinfect greenhouse structures, tools, floors, benches, etc. and is longer lasting and less irritating than bleach. Oxidate 2.0 is a broad-spectrum fungicide/bactericide/algaecide used to disinfect plant parts for preventative and curative applications. With no residue or REI, Oxidate 2.0 can be applied up to the day of harvest.
CropKing also offers a variety of fungicides labeled for the control of gray mold. Mycostop is a biofungicide that can suppress gray mold and increase growth and yield in diseased and healthy plants. Cease is another biofungicide that can suppress gray mold and double as an effective seed treatment. Green Cure and Milstop are salt-based fungicides that act as desiccants to dehydrate the gray mold fungus. These fungicides are all OMRI listed and they can be applied up to the day of harvest.
Gray mold can be prevented by keeping the greenhouse disinfected, removing plant debris, and maintaining a plant-friendly environment. Should you find yourself in need of assistance, CropKing’s horticultural experts are available to help recommend products and potential solutions.
Photo: G.J. Holmes, California Polytechnic State University at San Luis Obispo, Bugwood.org