Bacterial Canker and Bacterial Wilt.
Use certified plants. Rotate to allow 3 years between tomato plantings. Be sure to use the Clorox seed treatment described in the "Seed Treatment" section to prevent bacterial canker. When producing transplants, in addition to using the chlorine seed treatment, also be sure to treat re-used plant growing flats with chlorine. For staked tomatoes, stakes from bacterial canker infested fields should be dipped into a chlorine solution prior to use. Do not work in plantings while the foliage is wet. In infested fields, pruning and tying will promote spread of disease.
Addition of Actigard 50WG (0.3 oz/A increasing to 0.75 oz/A when plants are full size) plus fixed copper (1.5 lb active/A) to sprays for fungal diseases has reduced bacterial canker symptoms on fruit.
Bacterial Speck and Bacterial Spot.
When producing transplants, be sure to use the Clorox seed treatment described under the "Seed Treatment" section. Use disease-free seeds. Apply streptomycin (Agri-Mycin 17, Agri-Strep) sprays (1 pound per 100 gallons, 1.25 teaspoon per gallon) when the first true leaves appear and continue every 4 to 5 days until transplanting. Streptomycin cannot be used after transplanting.
Rotate to allow 2 to 3 years between tomato plantings. There can be a high risk of developing bacterial leaf spot and/or speck when using southern-produced transplants. Use only certified transplants. Where disease is present or anticipated, do not work in fields when plant surfaces are wet. Apply one of the following beginning shortly after transplanting and repeat every 7 days.
Actigard--0.33 oz 50WG/A, or
copper, fixed -- 1 lb ai/A plus mancozeb (Dithane, Manex II, Manzate, Penncozeb) -- l.5 lb 75DF/A or OLF, or
ManKocide -- 2.5-5 lb 61WP/A, or
Cuprofix MZ 1.75-7.25 lb 52.5DF/A
Postharvest Rots. To prevent rots in green wrapped tomatoes, avoid washing freshly harvested fruit in cold water. Maintain water temperature in flumes and tanks near fruit temperature to prevent movement of bacteria into the stem end of the fruit. Use chlorinated water (minimum 25 ppm) in the flume.
Powdery Mildew.
Greenhouse: Once observed, apply one of the following with thorough coverage of the upper and lower leaf surfaces and repeat at 7-day intervals.
JMS Stylet Oil -- l-2 gal/100 gal, or
Sun Spray Ultra-Fine Spray Oil -- 1-2 gal/ 100 gal
Field: The disease has been observed in unsprayed fields, and has resulted in defoliation. When the disease first appears, apply the following every 14 days:
Cabrio 8-12 20EG/A, or
Nova--2.5-4 oz 40WP/A
Timber Rot (Sclerotinia).
Rotate away from fields where snap or lima beans, peas, lettuce, or cucurbits have been grown. The following biological fungicide has been tested in some states; however, limited information is available on effectiveness in the Mid-Atlantic region. Apply 3 to 4 months prior to the onset of disease to allow the active agent to reduce inoculum levels of sclerotia in the soil. Following application, incorporate to a depth of 1 to 2 inches, but do not plow before transplanting tomatoes to avoid untreated sclerotia in lower soil layers from infesting the upper soil layer.
Contans--2-4 lb 5.3WG/A
Endura labeled for Botrytis Gray Mold control (9-12.5 oz 70W/A) will also help control Timber Rot. However, Endure cannot be used in greenhouse-like structures.
Southern Blight (Sclerotium).
High soil moisture and temperature favor disease development. Long crop rotations with corn and small grains help reduce disease incidence. Additionally, use the following in the transplant
water:
Terraclor -- 3 lb 75WP/100 gal of water or OLF and apply 0.5 pt/plant.
Fusarium and Verticillium Wilts.
Use resistant varieties. A new race of the pathogen has appeared in some regions and has overcome varietal resistance.
Leaf Spots (Early Blight, Septoria) and Fruit Rots (Alternaria, Anthracnose) .
Follow a crop rotation that provides at least 2 years without tomatoes or potatoes. Use disease-free transplants and disease-resistant varieties when possible. Fresh market varieties with resistance to early blight include Mountain Supreme and Plum Dandy. Processing varieties with tolerance to ripe fruit rots include Hypeel 696 and H-9423. In fields in mountainous areas, in fields not rotated away from tomatoes, and in late planted fields, begin sprays shortly after transplanting. In all other areas, either follow a regular (7-say) spray schedule begining when crown fruit are one-third their final size, or time sprays based on a locally-verified forecaster such as Tomcast or TomFast. Apply the following fungicides using the alternation pattern described to delay the development of resistant strains of the pathogen to Cabrio, Flint, or azoxystrobin.
chlorothalonil (Bravo, Echo, Equus) -- 2-3 pt 6F/A or OLF (also for gray leaf spot, black mold and soil rot), or
mancozeb (Dithane, Manex II, Manzate, Penncozeb) -- 3 lb 75WP/A or OLF (also for gray leaf spot and leaf mold)
Alternate either one of the above fungicides with one of the following:
azoxystrobin (Quadris--5.0 - 16.2 oz 2.08F/A or Amistar--1.6-2.0 oz 80WDG/A) (Also for buckeye rot and black mold. Do not use near apples, see label for details.), or
Cabrio--8-12 oz 20EG/A, or
Endura--2.5-3.5 oz 70W/A (also for Botrytis at 9-12.5 oz/A), or
Flint--4 fl oz 50WDG/A, (Do not apply near Concord grapes.) or
Tanos--8 oz 50 W/A + protectant fungicide (also for buckeye rot suppression and gray leaf spot)
To provide effective control, one additional application of fungicide is needed after application of fruit-ripening agent.
Late Blight New strains of the fungus that causes late blight are present in the mid-Atlantic region. These strains are agressive on tomatoes and resistant to Ridomil Gold. When palnts are 6 inches tall, apply one of the following protectant fungicides and repeat every 7 days or follow a locally-verified forecaster such as BLITECAST to schedule fungicide applictions:
chlorothalonil (Bravo, Echo, Equus) --1-3 pt 6F/A or OLF, or
Gavel--1.5-2 lb 75DF/, or
mancozeb (Dithane, Manex II, Manzate, Penncozeb) -- 3 lb 75DF/A, or OLF
Once late blight is detected in the area, switch to one of the following translaminar fungicides which can move into and through leaves:
Forum--6 oz 4.18SC/A plus a protectant fungicide, or
Previcur Flex--1.5pt 6F/A plus a protectant fungicide, or
Ranman--2.1-2.75 fl oz 400SC/A plus a protectant fungicide, or
Tanos--8 oz 50 W/A plus a protectant fungicide
Return to the use of protectant fungicides when condithions no longer favor the development of late blight.
Fruit Rot (Pythium and Phytophthora Buckeye Rot).
Apply mefenoxam (Ridomil Gold at 1 pint 4E per acre or Ultra Flourash at 1 quart per 2E per acre) as a soil surface application under the vines 4 to 8 weeks before harvest. Apply broadcast or banded. (see the section on "Calibrating Granular Application Equipment" for the amount needed per acre) Irrigate after application. An alternative to soil application of mefenoxam is to apply the following as a foliar spray beginning when crown fruit are one-third their final size and repeat every 14 days up to a total of 3 times:
mefenoxam/chlorothalonil (Flouronil, Ridomil Gold Bravo)--2 lb 76WP/A, or
Ridomil Gold/Copper -- 2 lb 65WP/A plus mancozeb 1 lb 75DF/A
When conditions favor disease apply one of the following between applications of the above fungicides.
Gavel--1.5-2 lb 75DF/A, or
Tanos--8 oz 50 WG/A
Botrytis Fruit Rot (Gray Mold).
This disease is a problem during the fall in fields with dense foliage and poor drainage. For fall production, select fields with good drainage. Shortly before harvest when conditions are wet and cool, apply the following:
chlorothanolil (Bravo, Echo, Equus) --2-2.75 pt 6F/A or OLF (also very good for late blight), or
Endura 9-12.5 oz 70W/A (also very good for early blight; not for use in greenhouses)
Tomato Spotted Wilt Virus (TSWV)
TSWV can be serious resulting in severely stunted plants. The virus is spread by thrips from ornamental plants (flowers) and weeds to tomatoes. Do not grow any ornamental bedding plants in the same greenhouse as tomato transplants. Control weeds in and around greenhouses. Monitor greenhouses for thrips and begin an insecticide control program once observed. In the field, use of reflective mulch can help repel thrips and can reduce the incidence of spotted wilt.
Information provided is intended for consideration by the user, but is not intended to be a recommendation. Production decisions should be based on consideration of many types of information (scientific, experiential, economic, legal, etc.) available to the user.
Where trade names are used no discrimination is intended, and no endorsement by the Cooperative Extension Service is implied.
Dr. Alan A. MacNab, Professor, Plant Pathology
Penn State College of Agricultural Sciences
211 Buckhout Lab, University Park, PA 16802
Updated: Nov, 2005; EMH
Loaded: Nov, 2005; EMH