| Tomato, Outdoor - Disease Control |
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Disease ControlNOTE: For the disease control products listed below, one product trade name and formulation is provided for each active ingredient (common name) as an example of rates, days to harvest (dh), REI, and special instructions. In many cases there are other products available with the same active ingredient. Please see Table 22 and Alphabetical Listing by Trade Name for more information on products with the same active ingredients. Grey Mold (Botrytis)Grey mold is a commonly found disease of tomato and is particularly damaging in greenhouses where the relative humidity is high. The pathogen infects leaves, stems, petioles, and fruit. “Ghost Spots” develop when the pathogen invades the fruit then ceases growth prior to causing decay; the resulting white to yellow rings make fruit unmarketable. Injured transplants can develop gray mold infections of the stem which girdle the plant and cause plant death. Reduce plant wetness by avoiding overhead irrigation. Fungicides are useful in protecting fruit; a diversity of fungicides with different modes of action must be used as Botrytis commonly develops fungicide resistance. See: Leaf Spots. Leaf Spots: Early Blight (Alternaria solani) and Septoria leaf spot (Septoria lycopersicum)Early blight and Septoria leafspot are very destructive of tomato. Both diseases may occur together. Plow under plant debris after harvest. Rotate away from tomatoes for at least two years. Provide optimum nutrition throughout the season. If planting in an area with a history of either disease, begin fungicide applications before disease is evident, usually when first fruit are half grown or approximately the first week of July. Follow fungicide intervals recommended by a disease forecasting system (TOM-CAST) if weather and forecast data are available in your region.
boscalid (Endura): 2.5-3.5 oz/A. (0 dh, REI12h, Group 7). mancozeb (Dithane F45): 1.2-2.4 qt/A.(5 dh, REI 24h, Group M3). mandipropamid plus difenconazole (Revus Top): 5.5-7.0 fl oz/A. (1 dh, REI 12h, Groups 40 & 3).Addition of a spreading/penetrating adjuvant is recommended. pyraclostrobin (Cabrio EG): 8 to 12 oz/A (0 dh, REI 12h, Group 11). Apply at the first sign of disease and reapply after 7 to 14 days if necessary. Apply only six applications per season or 96 oz/A. Do not rotate with other strobilurins such as Quadris. Anthracnose (Colletotrichum species)Anthracnose is a problem on fruit when it ripens on the plant, but the fungus can also invade the stem tissues resulting in premature death. Roatate crops such that non-host crops are grown at least very other year. Control weed hosts. Stake plants or use mulch to reduce fruit contact with soil. Avoid overhead irrigation. Harvest fruit regularly to avoid excessively ripe fruit. Apply fungicides according to a disease forecasting system (TOMCAST). boscalid (Endura): 2.5-3.5 oz/A. (0 dh, REI12h, Group 7). mancozeb plus zoxamide (Gavel 75DF): 1.5 to 2 lb/A (5 dh, REI 48h, Groups M3 & 22). Apply at 7 to 10 day intervals when conditions are favorable for disease development. Add Latron surfactants to improve performance. mandipropamid plus difenconazole (Revus Top): 5.5-7.0 fl oz/A. (1 dh, REI 12h, Groups 40 & 3).Addition of a spreading/penetrating adjuvant is recommended. pyraclostrobin (Cabrio EG): 8 to 12 oz/A (0 dh, REI 12h, Group 11). Apply at the first sign of disease and reapply after 7 to 14 days if necessary. Apply only six applications per season or 96 oz/A. Do not rotate with other strobilurins such as Quadris. Late Blight (Phytophthora infestans)Late blight has not been common in New England but when it occurs it can be very destructive. Protectant fungicides are a key tool for management; however, many strains of Late Blight have become resistant to mefenoxam. When resistant strains are present, early blight fungicides will give as much protection against late blight as mefenoxam combinations. Several forecasting systems can be used for identifying Late Blight infection periods. Avoid the use of overhead irrigation. Promptly plow under old tomato fields after harvest. Eliminate cull piles and volunteer plants of both tomato and potato. Some resistant cultivars are available. fluopicolide (presidio): 3.0-4.0 fl oz/A. (2 dh, REI 12h, Group43). Must be tank mixed with a fungicide with a different mode of action. mandipropamid plus difenoconazole (Revus Top): 5.5-7.0 fl oz/A. (1 dh, REI 12h, Groups 3 & 40).The addition of a spreading/penetrating type adjuvant is recommended. Powdery MildewPowdery mildew is a relatively new disease of tomato in the Eastern United States. It is more common in the greenhouse than in the field, but in either case it can cause early plant senescence and reduced yields. Powdery Mildews are obligate parasites and survive on overwintering tomato, alternate weed hosts, or perhaps as sexual fruiting bodies. Promptly plow under tomato crop debris after harvest. Control volunteer tomatoes and Solanaceous weeds. White Mold, Sclerotinia Blight (Sclerotinia species)Sclerotinia survives for years in the soil and is particularly destructive to ground tomatoes. Many vegetable crops are hosts. Rotate with corn or other grass species. Do not plant seed that is contaminated with sclerotia (survival structures). Encourage rapid soil drying by irrigating in the morning and/or buried drip irrigation. Avoid excessive nitrogen levels and ensure adequate potassium fertility. Soil sterilization with chemical, steam, or heat treatments (solarization) can significantly reduce sclerotia (inoculum) in the soil. Research has shown promise from incorporating broccoli biomass or brassica cover crops and the biocontrol agent, Coniothyrium minitans (Contans). Coniothyrium minitans (Contans): Apply 1 to 4 lb/A in 20 to 50 gal water (REI 4h, Group is not applicable). Spray on the soil surface and incorporate into the top 2” of soil. Fall application is best or 3 to 4 months before planting to allow for the biocontrol agent to infect the sclerotia of Sclerotinia. OMRI listed. Phytophthora Blight and Fruit Rot (P. capsici and Pythium species)Phytophthora fruit infections are called buck-eye rot and Pythium fruit infections, which usualy infect ripe fruit, are called watery rot. To avoid fruit rots, keep plant tops dry by avoiding overhead irrigation or by using buried drip irrigation. Prepare the soil and beds to enhance drainage and avoid planting in low areas. Stake plants and/or use mulches to minimize fruit contact with the soil. Fungicides may be used to control crown, foliar, and fruit infections. See Late Blight. Seed Decay and Damping-OffBuy treated seed. Do not use treated seed for food, feed or oil purposes. Use sterile growing media. Bacterial Canker (Clavibacter), Bacterial Speck (Pseudomonas), and Bacterial Spot (Xanthomonas)Bacterial canker is the most destructive bacterial disease of tomatoes in our region. All three bacterial diseases may be seed-borne or may overwinter in crop debris in the field. Buy hot-water treated seed or seed certified to be free of bacteria. Hot water seed treatment can be done at home. Treat seed for 25 minutes at 122°F. Some lots of seed can be vulnerable to heat treatment. Always treat a small amount of seed (50-100) of each lot before treating the reminder of the lot. See Disease Management. Avoid working in fields when plants are wet. Rotate out of tomatoes for at least two years. Use copper or streptomycin on plants before transplanting. acibenzolar-S-methyl (Actigard): 0.33-0.75 oz/A. (14 dh, REI 12h, Group 21). Apply to healthy, actively growing plants preventively. Plant defense activator. Bacillus species (Serenade, Sonata, Rhapsody, Cease): See labels for specific instructions. (REI 4h, Group N/A). Biological control. basic copper sulfate (Basic Copper 50 W HB): 0.5-1.0 pt/A (0 dh, REI 48h, Group M1) Apply at seven-day intervals when disease first occurs, until night temperatures fall below 60°F. Do not apply in spray solution having a pH less than 6.5. mancozeb plus copper (Cuprofix MZ Disperss): 1.75-7.25/A. (5dh, REI 24h, Groups M1 & M3). Do not apply in spray solution having a pH less than 6.5. Cucumber Mosaic Virus (CMV)Many different strains of this virus occur and the host range includes plants in more than 31 different families. In tomato, the symptoms can be confused with Tobacco Mosaic as well as other virus diseases. The disease is spread by several species of aphids in a nonpersistent manner. Reduce weeds, especially chickweed, pokeweed and milkweed, as much as practical. Insecticides will not control this virus. Isolate tomato fields from cucurbits especially where there has been a history of CMV. Resistant varieties cannot be recommended at this time. Tobacco and Tomato Mosaic Virus (TMV, TomMV)Several strains of TMV exist including the closely related tomato (TomMV) strain. Symptoms on tomato can vary considerably as will the severity of disease and the effect on yield. Either strain can be seed-borne or transferred from previously infected plant debris, weeds, transplants, other crops or workers using tobacco products. Unlike other viruses, TMV and TomMV are easily spread from plant to plant by contact with hands and tools. Insects are not considered to be important vectors. Grow resistant varieties. Control weeds as much as practical. Hands and clothes soiled with tobacco or from weeding can transmit the virus. When working with plants, avoid wearing soiled clothes. Smoking should not be permitted. Wash hands after weeding or smoking. Do not plant susceptible pepper or tomato varieties for at least two years on land that previously had TMV-infected crops. Handle plants as little as possible. Do not allow workers to use tobacco products while working with plants. Tomato Spotted Wilt Virus (TSWV)Do not raise tomato, pepper, eggplant or cauliflower transplants in the same greenhouse as ornamentals. Monitor thrips and control as necessary. Resistant varieties are not available at this time. The host range for TSWV is one of the largest of any virus. Hundreds of plant species are susceptible including many commercial floriculture crops. At this time TSWV is more of a problem on greenhouse crops (ornamentals) than vegetable crops. Wilt (Fusarium and Verticillium)Plant resistant varieties. Pre-plant treatment of soil with effective fumigants will give short-term control but will not completely eliminate the pathogens from fields. Rotate tomatoes with non-host cops such as corn or small grains to lower inoculum levels. Avoid bringing contaminated soil on equipment to new land. |
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