File Name: tomato diseases and treatment .zip
Tomato Disease Guide
Diseases are a major limiting factor for tomato production. Diseases can be classified into two groups. The first are those caused by infectious microorganisms that include fungi, bacteria, viruses and nematodes.
These diseases are contagious and can spread from plant to plant in a field, often very rapidly when environmental conditions are favorable.
The second group includes those caused by non-infectious physical or chemical factors, such as adverse environmental factors, nutritional or physiological disorders and herbicide injury. Non-infectious diseases cannot spread from plant to plant; however, the distribution of the disease may be quite uniform and extensive if an entire planting was exposed to the adverse factor. It is critical for effective disease control to recognize the difference between infectious and non-infectious diseases, and the type of microorganism causing an infectious disease be determined.
For example, use of a fungicide to control a non-infectious disease, such as blossom-end rot, is a wasted expense that will not correct the problem. This Fact Sheet is intended to aid vegetable producers in recognizing the symptoms of common tomato diseases caused by fungi. Fungi are the most common cause of infectious plant diseases and can be very destructive.
Often, symptoms of diseases are non-typical or confusing. It is a good practice to submit samples of diseased plants to the OSU Plant Disease and Insect Diagnostic Laboratory for an accurate diagnosis, particularly when a new disease is encountered. Control of tomato diseases is best if all available methods i. Cultural practices are aimed at avoiding disease or delaying its occurrence.
It is critical to start with disease-free transplants because many infectious diseases may be carried on tomato seed. Crop rotation is another cultural practice for reducing losses from plant diseases. It is important to remember that vegetables such as pepper, eggplant and potato should be avoided in rotations with tomatoes. These crops are susceptible to many of the same diseases. Cultural management of the crop will also influence what diseases may develop.
Tomatoes allowed to spread on the ground will develop more soil rot problems, while fruit on staked or trellised plants will be exposed more to sunscald. Tomatoes irrigated by sprinkler systems that wet the foliage and fruit are more likely to develop disease problems than those watered by drip or furrow systems. Planting disease-resistant varieties is probably the most effective and economical method of disease control.
Disease resistance can be utilized to solve current problems or to prevent a disease from increasing. Fortunately, many excellent tomato varieties have been developed with resistance to one or more of the common tomato diseases. Strains of the Fusarium wilt fungus have developed that can overcome previously resistant varieties. Chemical control is sometimes necessary because resistance is not yet available for some important diseases. The registration status, rates, timings and method of application of fungicides often change.
Consult the current Extension Agents Handbook of Insect, Plant Disease and Weed Control E or the local county Extension educator for the latest recommendations for chemical control of tomato diseases. Wilt diseases are caused by pathogens that invade the vascular system xylem tissue and disrupt water flow through the plant.
Fusarium wilt is the major wilt disease of tomato in Oklahoma. Verticillium wilt is easily confused with Fusarium wilt, but has not yet been reported in Oklahoma. The first symptom is usually a yellowing of the lower leaves, which gradually wilt and die. Symptoms may first occur on only one side of the plant Figure 1. The disease progresses up the stem until all of the foliage is killed and the plant dies. If stems or petioles from wilted areas of diseased plants are cut, a reddish-brown discoloration can be seen between the pith center of the stem and the outer green part of the stem Figure 2.
The fungus survives and persists indefinitely in field soil. The fungus is also seedborne and is thought to spread long distances in this manner. The disease is most serious in sandy soils and at temperatures between 80 F to 90 F. Soils become infested by planting infected transplants and from movement of infested soil by wind and water erosion or on farm implements.
Control: Growing tomato varieties resistant to Fusarium wilt is the most effective means of control. Improved varieties and hybrids are available that have resistance to races 1 and 2; and 1,2 and 3. Resistant varieties can become susceptible to Fusarium wilt through time when they are intensively cropped on the same site. For example race 3 has been reported in other states where tomatoes are intensively grown.
Crop rotation should be used in conjunction with varietal resistance to maintain sustainable control and limit the development of new races. Figure 1. Fusarium wilt—Initial symptoms are yellowing and wilting of branches and later, entire plants photo courtesy R.
Gardner, North Carolina State University. Figure 2. Fusarium wilt—Internal discoloration of stem. Southern blight can be a devastating disease of tomatoes in Oklahoma.
The southern blight fungus has a wide host range attacking more than species of plants that include common weeds and crop plants. The initial symptom of southern blight is a rapid wilting of the entire plant. A water-soaked lesion on the stem near the soil line rapidly expands, turns brown and girdles the stem. A white mold mycelium eventually covers the stem lesion and surrounding moist soil. Sclerotia are first white, later becoming brown, and resemble mustard seeds.
The presence of the white mycelium and sclerotia at stem base of affected plants are very useful characteristics for identifying southern blight Figure 3. The fungus survives in the soil as sclerotia, which may build to high numbers when susceptible plants are cropped repeatedly. After sclerotia germinate, the fungus must first colonize organic debris near the soil surface before the fungus can cause infection.
The disease is favored by high humidity and soil moisture and warm to hot temperatures 85 F to 95 F. Control: Southern blight is difficult to control when conditions favor the disease and numbers of sclerotia in the soil are high. Crop rotation with a non-susceptible grass crop, such as corn, is the most effective means of reducing numbers of sclerotia and resulting incidence of southern blight. Avoid planting tomato following a very susceptible crop such as cantaloupe or watermelon.
Plant residues should be thoroughly incorporated into the soil prior to transplanting so their presence on the soil surface does not encourage southern blight development. A fungicide program for southern blight may be beneficial. Figure 3. Southern blight—White moldy growth mycelium and basal stem canker. Alternaria solani Early blight is a common leaf-spotting fungal disease of tomato. Extensive defoliation from early blight exposes fruit to sunscald and increases fruit rot. Early blight also attacks stems and fruit.
Foliar diseases are most severe in eastern Oklahoma where rainfall and relative humidity levels support disease development, or wherever sprinkler irrigation is used. Dark brown cankers may develop on stems and girdle stems of seedlings at the soil line.
Stem lesions on older plants usually remain confined to one side of the stem. Leaf symptoms appear on older leaves first and are characteristic of the disease. The leaf area surrounding these spots may turn yellow. Infected leaves eventually turn brown and drop from the plant. Defoliation progresses upward from the lower plant. The fungus survives in the soil by forming resistant spores in association with diseased tomato debris capable of persisting for one year or more.
Infection occurs rapidly under warm, humid conditions. Thousands of spores are produced in spots of infected leaves and are capable of causing more infections. Plants under stress from nitrogen deficiency, heavy fruit load or other factors are most susceptible to the disease. Control: Crop rotation with crops other than eggplant, potato and pepper should be practiced to reduce and delay early blight development. Avoid prolonged wetting of leaves from irrigation or use drip irrigation.
Maintain adequate, but not excessive, soil fertility. A spray program using a recommended fungicide beginning at fruit set and continuing on a 7- to day schedule should be maintained where early blight problems are anticipated.
Figure 4. Photo courtesy M. McGrath, Cornell University. Septoria is a very common foliage disease in Oklahoma that may also attack stems, but not fruit.
The disease first appears on the lower leaves after the plant has set fruit. Leaf spots begin as yellow areas that later become circular with gray centers and dark borders Figure 5.
Tiny black specks may develop in the center of these spots. These are fruiting structures that release spores. Severely infected leaves fall off. Defoliation progresses from the base of the plant upwards and resembles early blight from a distance. However, the larger dark leaf spots with concentric rings of early blight are clearly different from smaller Septoria leaf spots. Loss of foliage may cause fruits to become sunscalded.
Most infection early in the season probably arises from infested plant debris remaining in the soil from a previous tomato crop.
Spores of the fungus are spread by splashing rain. The disease is favored by moderate temperatures and extended periods of high relative humidity.
Tomato Diseases & Disorders
This post may contain affiliate links. If you click on an affiliate link and make a purchase, we receive a small commission at no extra cost to you. Find our full disclosure here. Tomato growers are a passionate bunch. Some of us spend long hours combing over seed catalogs and nursery benches full of plants to select the perfect tomato varieties for our garden. We plant, tend, prune, fertilize , stake, and otherwise care for our tomato plants with a dedication rivaled only by our dedication to our human family.
Diseases are a major limiting factor for tomato production. Diseases can be classified into two groups. The first are those caused by infectious microorganisms that include fungi, bacteria, viruses and nematodes. These diseases are contagious and can spread from plant to plant in a field, often very rapidly when environmental conditions are favorable. The second group includes those caused by non-infectious physical or chemical factors, such as adverse environmental factors, nutritional or physiological disorders and herbicide injury.
Brown Jr. Schwartz, Colorado State University, Bugwood. Bartolo, , Bugwood. State Search:. Site Index Search Got Pests:. About Got Pests? Is It Really a Pest?
tomato diseases pdf tnau
This guide provides descriptions and photographs of the more common tomato diseases and disorders worldwide. For each disease and disorder the reader will find the common name, causal agent, distribution, symptoms, conditions for disease development and control measures. We have also included a section on common vectors of tomato viruses.
Florida tomato production is often challenged by an array of plant diseases promoted by a warm and humid climate.
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