See:
Greenhouse Plants, Tomato - Gray Mold
Cause The fungus, Botrytis cinerea (teleomorph: Botryotinia fuckeliana), is an opportunistic pathogen that easily invades weak, damaged, or senescing tissue. Typically this fungus causes minor losses but can be a significant problem under environmental conditions that promote the fungus to infect and sporulate. This fungus has a broad host range and is present throughout much of the year in western Oregon. All aboveground portions of the tomato plant can be attacked, but often disease starts on senescing flowers or leaves. Initial infections are important for subsequent spread to healthy, vigorous leaves, stems, and fruit. The fungus will rapidly sporulate (5 to 7 days) on diseased tissues. Spores (conidia) are produced throughout the growing season under a wide range of temperatures and humidity, and stem infections are a durable inoculum source, producing conidia throughout bloom. Cool temperatures (68°F is optimal but the fungus can grow between 50F° and 80°F), high humidity, and free water on plant surfaces favor the disease, as do close plant spacing and irrigation practices that keep plants wet for a longer time. Durable sclerotia overwinter in soil.
Symptoms of ghost spot on fruit result from the fungus' unsuccessful attempt to infect. There is no rot, but fruit is unmarketable.
Symptoms Affected tissue typically dies and takes on a brown coloration. Under high humidity affected tissues are usually covered with fuzzy gray-brown conidiophores and conidia (spores) characteristic of the fungus. Infections often begin on flowers and spread to fruit, leaves, and stems. Leaf lesions rapidly expand to cover the entire leaflet surface. Infection can go into petioles and stems, which, if severely affected, may be completely girdled, killing tissue above the cankered portion. Stem cankers have a distinctive brown and tan target-spot pattern.
Fruit can develop a soft rot that starts at the stem end and can progress into a fruit mummy. Decayed fruit portions take on a whitish coloration and skin may split. The fungus may sporulate in areas of fruit decay. When initial fruit infections abort, typically when environmental conditions are not conducive for the fungus, ghost spots can develop. Ghost spot presents as faint, pale halos (3 to 8 mm in diameter) on fruit. They are white on immature fruit, yellow on ripe fruit. A small necrotic fleck may appear along with the halo. Ghost spots rarely develop further but are a warning that spores are being produced nearby.
Cultural control
- Apply lime to the soil as this can aid in reducing susceptibility of plants.
- Stake plants and manage excessive foliage to encourage air flow and rapid drying.
- Scout regularly for disease.
- Remove dead or infected plant parts such as flowers, leaves, and rotted fruit.
- Avoid overhead irrigation that keeps foliage and fruit wet for a long time.
Chemical control
- Bonide Fung-onil is available for home gardens. H
- Carboxamide (Group 7) formulations are registered for use. Do not make more than two (2) sequential applications before alternating to a labeled fungicide with a different mode of action.
- Endura at 9 to 12.5 oz/A on 7- to 14-day intervals. Preharvest interval is 0 days. 12-hr reentry.
- Fontelis at 16 to 24 fl oz/A on 7- to 14-day intervals. Preharvest interval is 0 days. 12-hr reentry.
- Copper (Group M1) products are not recommended as stand-alone materials.
- Champ WG at 1.06 lb/A on 3- to 10-day intervals. 48-hr reentry. O
- Cueva at 0.5 to 2 gal/100 gal water on 7- to 10-day intervals. May be applied on the day of harvest. 4-hr reentry. O
- Cuprofix Ultra 40 Disperss at 1.25 to 3 lb/A on 5- to 10-day intervals. 48-hr reentry.
- Kocide 2000-O at 1.5 to 3 lb/A or Kocide 3000-O at 0.75 to 1.75 lb/A on 5- to 10-day intervals. 48-hr reentry. O
- Previsto at 1 to 2 quarts/A on 5- to 10-day intervals. 48-hr reentry. O
- Inspire Super (Group 3 + 9) at 16 to 20 fl oz/A on 7- to 10-day intervals. Do not make more than one (1) application before alternating to a labeled fungicide with a different mode of action (non-Group 3 or 9). Preharvest interval is 0 day. 12-hr reentry.
- Miravis Prime (Group 7 + 12) at 9.2 to 11.4 fl oz/A on 7- to 21- day intervals. Do not apply to greenhouse tomatoes. Do not apply more than two (2) sequential applications. Preharvest interval is 0 days. 12-hr reentry.
- Orondis Opti (Group M5 + 49) at 1.75 to 2.5 pints/A on 7- to 14-day intervals. Do not apply more than two (2) sequential applications. Preharvest interval is 0 days. 12-hr reentry.
- OSO 5% SC (Group 19) at 6.5 to 13 fl oz/A on 7- to 14-day intervals. Can be applied the day of harvest. 4-hr reentry. O
- Problad Verde (Group BM01) at 20.5 to 45.7 fl oz/A on 7- to 10-day intervals. Needs 8 to 12 hours of drying time to absorb into treated tissue. Do not make more than two (2) sequential applications before rotating to a labeled fungicide with a different mode of action. Preharvest interval is 1 day. Reentry interval is 4 hours. O
- Regalia Biofungicide (Group P5) at 1 to 4 quarts/A on 7- to 10-day intervals. Does not benefit from the addition of an adjuvant. Preharvest interval is 0 days. 4-hr reentry. O
- Scala SC (Group 9) at 7 fl oz/A on 7- to 14-day intervals. Use only in a tank-mix with another fungicide effective on this disease. Do not apply within 1 day of harvest. 12-hr reentry.
- Trilogy at 0.5% to 1%. Not labeled for use in Oregon. Do not use above 90°F or when plants are under heat or moisture stress. Do not use when foliage is wet as good coverage is essential. Poor control as a stand-alone product. 4-hr reentry. O
Biological control
- Actinovate AG at 3 to 12 oz/A as a foliar spray on 7- to 14-day intervals. 4-hr reentry. O
- Double Nickel LC at 1 to 6 quarts/A on 3- to 10-day intervals. Can be applied the day of harvest. 4-hr reentry. O
- LifeGard WG at 1 to 4.5 oz/A on 7- to 14-day intervals for activating plant resistance. Refer to label for appropriate rate per application volume. Preharvest interval is 0 days. 4-hr reentry. O
- Romeo at 0.45 to 0.68 lb/A on 7- to 10-day intervals starting prior to infection. Preharvest interval is 0 days. 4-hr reentry. O
- Serenade Opti at 14 to 20 oz/A on 7- to 10-day intervals. Applications can be made up to and the day of harvest. 4-hr reentry. O
- Stargus at 2 to 4 quarts/A plus a nonionic surfactant on 7- to 10-day intervals. Preharvest interval is 0 days. 4-hr reentry. O