Phyton Corporation 1 7 Things to Stop Botrytis Seven Things to Stop Botrytis (Gray Mold)
Are you doing all you can?
It’s that time of year again—spring—
when botrytis mold spores thrive and
multiply, showing up as gray fuzzy
patches on your plants, threatening to
wreak havoc with your crop and your
bottom line. This aggressive fungus
isn’t fussy. It can strike almost every
type of plant— ornamentals, fruits,
vegetables, and herbs are all
susceptible to gray mold, especially
the young and tender ones, as well as
Botrytis cinerea sporulation on a ripe strawberry. the recently wounded. It feeds on
dying or dead plant material, like flower Photo by Scott Bauer. USDA, http://www.ars.usda.gov petals, and thrives under cool, wet
conditions. It spreads rapidly: through the air, through the water, and via tools and
equipment. And it’s fast. It can germinate and infect a plant in a short five to eight hours, its
effects visibly apparent within a few days.1 When you consider that 60,000 botrytis spores can
inhabit a piece of plant tissue no bigger than your little fingernail, and that it only takes one
solitary spore to infect a plant, then you know this is a disease you can’t afford to ignore.2
Here are seven things you can do now to help stop botrytis or gray mold:
1) Give your plants some air. A tight canopy is like a golden invitation to botrytis
spores. Space your plants out as much as possible to allow for good air circulation, which
will help keep their surfaces free of excess moisture. Removing the lower leaves from plants
located in overly shaded areas will also help keep the air flowing around them and prevent
moisture build-up.3
2) Sanitation is key. Remove dead or dying tissue from plants and the soil. Heavily
infected plants should be removed (if possible, wrap them in wet paper towels or newspaper
to keep spores from migrating); likewise, trash/cull piles should be covered with plastic and
removed from the site promptly.4 Do not store garbage cans containing plant debris inside
the greenhouse; simply opening the lid could unleash a torrent of spores. Be mindful of petals
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goes for plant debris lying on benches or walkways.5 Use hand sanitizers as much as possible.
Treat pruning shears and knives with disinfectant after pruning, and consider using two
pruners at a time, alternating pruning with disinfecting the tool as you work.6 (To disinfect
cutting tools, you can use X3 at the rate of 0.25 ounces per gallon or 25 ounces per 100
gallons. Soak tools in the solution for at least two minutes.)
3) Be gentle with your plants. Since botrytis seeks out wounded tissue, broken
stems, and damaged leaves, it’s important to avoid injuring your plants. Don’t leave
large stubs when youtake cuttings or otherwise cause damage.7 Prune in the early
afternoon so that leaf-cut wounds will dry quickly.8 Treat infected lesions promptly.
4) Water in the morning. Water-based irrigation or spray operations should be done in
the morning so that plant surfaces will dry as the temperature rises during the day. Avoid
using overhead irrigation, and do not use spray operations in the late afternoon or on cloudy
days. The main idea is to avoid practices that will promote prolonged wetness on plant
surfaces.
5) Watch the humidity. Keep the relative humidity (RH) within a preferable range of 80
to 85%. Exchanging the air by turning on the heat and opening up the vents for 5 to 10
minutes can be very effective in lowering RH. Any reduction in RH can significantly help
prevent botrytis. Venting heated air carries moisture up and away from your plants and out
of your greenhouse. The short period of time it takes to do this does not use a lot of energy,
yet it will yield enormous benefit by removing the moisture from the air that would
otherwise settle on your plants.9
6) Use fans to reduce moisture. For best results, use fans that produce horizontal air
flow, which helps maintain more even temperatures and reduces condensation-producing
cold spots.10
7) Use a fungicidal treatment in the spring and fall, when conditions are favorable for
gray mold to develop, and/or at the first sign of infection. A favorite among growers for the
treatment of botrytis, Phyton 35 (or Phyton 27) can be used to stop botrytis and many other
fungal infections throughout your crop rotations. Because it is much easier to prevent a
disease than it is to cure it, using a fungicide as a preventative measure is a much more costeffective and efficient method to control this disease.
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To prevent botrytis infestation, use Phyton 35 (or Phyton 27) every 7 to 10 days at the
lower (preventative) rate shown on the label.
To cure botrytis infestations that have already appeared on your plants, always use
Phyton 35 (or Phyton 27) at the highest labeled rates. Do not exceed the labeled rates
due to risk of phytotoxicity.
Note that while Phyton 27 can be used effectively as a fungicide on your ornamental crops,
only Phyton 35 is labeled for use on edible plants.
Final points
Botrytis, which is most active when the temperature hovers between 55° and 75°F, is most
rampant in the spring and fall. During these seasons, it is essential you monitor your crops
closely for any sign of this fast-growing disease, which will first appear as a white growth that
quickly turns gray, or it may show up on flowers as light or dark brown spots. Gray mold can
live year-round in the greenhouse. Spores are often found on the outside of seeds and can
remain dormant on plant surfaces for up to three months (or in some cases, the life of the
plant).11 By following an integrated plan that includes the above practices, you can
significantly reduce your crop exposure to botrytis.
1
Dr. Siva Sabaratnam, “Botrytis Blight & Stem Canker of Greenhouse Tomato, Biology & Disease Cycle
of Grey Mould (Botrytis cinerea)," British Columbia Ministry of Agriculture,
http://www.agf.gov.bc.ca/cropprot/botrytis.htm (accessed April 13, 2014).
2
Gary W. Moorman, “Botrytis or Gray Mold,” Penn State College of Agricultural Sciences,
http://extension.psu.edu/pests/plant-diseases/all-fact-sheets/botrytis-or-gray-mold (accessed April 13,
2014).
3
Sabaratnam, “Botrytis Blight & Stem Canker of Greenhouse Tomato.”
4
Ibid.
5
Josh Gibson, Sarah Williams, and Francesca Peduto Hand, “Botrytis Gray Mold in Greenhouse Floral
Crops,” The Ohio State University, College of Food, Agricultural, and Environmental Sciences,
http://ohioline.osu.edu/hyg-fact/3000/pdf/Botrytis_Gray_Mold_HYG_3070_2014.pdf (accessed April 13,
2014).
6
Sabaratnam, “Botrytis Blight & Stem Canker of Greenhouse Tomato.”
7
Moorman, “Botrytis or Gray Mold.”
8
Sabaratnam, “Botrytis Blight & Stem Canker of Greenhouse Tomato.”
9
Dr. Robert L. Wick, “Botrytis Blight of Greenhouse Crops,” University of Massachusetts Amherst, The
College of Natural Sciences, Agriculture & Landscape Program, Greenhouse Crops and Floriculture
Program,https://extension.umass.edu/floriculture/fact-sheets/botrytis-blight-greenhouse-crops(accessed April
13, 2014).
10
Ibid.
11
Moorman, “Botrytis or Gray Mold.”
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