Tomato Plant Diseases

Troubleshooting Tomato Plants

Fusarium wilt

The earliest signs of Fusarium Wilt in Tomato plants is the drooping and subsequent yellowing of the lower leaves on one stem. These symptoms may appear on only one side of the plant. Yellowing and wilting of the leaves occurs, and the plants may eventually die.

If the stem is cut , plant tissues under the surface are frequently discolored brown. Favored by soil temperatures around 80 F, and a low soil pH, Fusarium wilt is more common in southern latitudes. Verticillium wilt , which is indistinguishable to the eye is more prevalent in Northern regions.

There is no actual proven cure for Fusarium. It remains in the soil for multiple seasons - up to a decade. It is difficult to completely eradicate it. But there are measures that you control it.


With both Fusarium wilt and Verticillium wilt drooping and subsequent yellowing of the lower leaves occurs and the plants may eventually die. The leaf veins will brown, followed by the shoots browning and lower leaf drop. Leaves higher up turn a dull green in color and the edges curl upwards.




1. Be sure to use only sterile Potting Soil when starting your own seedlings.

2. Raising the Soil pH helps to keep it in check.

3. Resistant Varieties - Use resistant varieties. Seed packets and sometimes seedlings are labeled with resistance codes to various diseases. Tomato Disease Resistance Codes for Fusarium can be found on the packet as well as the catalog. F = Fusarium Wilt - FF = Fusarium, races 1 and 2 - FFF = Fusarium, races 1, 2, and 3



Verticillium wilt

Verticillium wilt closely resembles Fusarium wilt, only a laboratory diagnosis can sufficiently distinguish between the two. Verticillium wilt starts with a general or blotchy yellowing of the lower leaves and a wilting of younger shoots when exposed to direct sunlight. Initially, the wilted shoots will recover over night.

The leaf veins will brown, followed by the shoots browning and lower leaf drop. Leaves higher up turn a dull green in color and the edges curl upwards. Plants are stunted and defoliated with only the growing tips remaining green. The fruits are small and sunscald easily. The branches tend to be less erect than those of healthy plants, giving Verticillium-infected plants a prostrate appearance. When the stem is cut open, the plant tissues are generally a murky brownish near the base of the plant.

I could tell you to use disease-free seedlings and or seeds, but that would like closing the barn door after all the animals got loose. Once you have a wilt on the Tomatoes there is no magic wand or spray to get rid of it. Fungicides intended for the control of leaf blights have no effect on wilts which are internal infections.


Remove and destroy all wilted plants and all debris of tomato and other susceptible crops at the end of the growing season {Do not put them in the compost heap, this will only serve to perpetuate the disease}.

Other susceptible crops are peppers , eggplants, potatoes, raspberries and strawberries

Crop Rotation - Rotate in a four year cycle with non susceptible crops, the fungi that causes wilt survive for many years in the soil and Verticillium as well as Fusarium fungus will attack many other plants.

Use wilt resistant varieties -resistant tomato varieties are labeled V (for Verticillium) and F (for Fusarium). These disease resistance designations are shown in reputable seed catalogs both paper and online.

Tomato Spotted Wilt Virus

Spotted wilt is caused by the tomato spotted wilt virus {TSWV} - no rocket science there. Spotted Wilt or TSW will greatly reduce the quantity and quality of the harvest. More than 150 plants are effected by this virus. Pepper ,lettuce, eggplant, cauliflower, celery, spinach, pea, dahlia, sweet pea, nasturtium, chickweed, poppy, lily, orchid, chrysanthemum, cineraria, mallow, etcetra.

Thrips transmit this virus. They acquire TSWV as larvae and later transmit it.

Spotted Wilt symptoms vary widely, The first symptoms are orange flecks or a bronzed appearance of young leaves. Leaf spots may appear target-like as in early blight. Older leaves turn brown, droop and wither. Younger shoots may develop dark streaks, dieing back on the ends . Raised yellowish spots develop on green fruits. As the tomatoes ripen, these spots become more prevalent with rings of yellow or brown alternating with green and later pink or red. Similar diseases have slightly different symptoms. Vascular wilts do not have the orange spots on the leaves, or circular bulls eye spots on the fruits.


Avoid proximity to plants {Weeds are plants too} that can serve as hosts for this virus. It is important to control weeds, especially chickweed and which serves as a place for the virus to overwinter. In the spring, these weeds become a major source of the virus. Do not grow tomatoes near lilies or dahlias or other ornamentals either in or outdoors.

Reflective Mulch will reduce, but not eliminate losses from Tomato spotted Wilt . Management of Thrips will also reduce, but not eliminate TSWV

Thrips develop rapid resistance to common pesticides , so a pesticide rotation is necessary.

Spotted Wilt symptoms vary widely, The first symptoms are orange flecks or a bronzed appearance of young leaves. Leaf spots may appear target-like as in early blight. Older leaves turn brown, droop and wither. Younger shoots may develop dark streaks, dieing back not the ends . Raised yellowish spots develop on green fruits. As the tomatoes ripen, these spots become more prevalent with rings of yellow or brown alternating with green and later pink or red. Similar diseases have slightly different symptoms. Vascular wilts do not have the orange spots on the leaves, or circular bulls eye spots on the fruits.

Leaf Roll generally develops in rainy periods. The lower leaves roll upward until the edges touch and become thick and leathery . Leaf roll is predominant in cool wet weather, excessive fertilizer, and pruning are contributory factors.

Sunscald


Multiple examples of sunscalded tomatoes and the ensuing black mold.


Sunscald develops on the side of fruits suddenly exposed to the direct sun, first appearing as a light colored spot on green fruits. It's not really a disease and can not be transmitted from plant to plant, it's basically a sun burned tomato. This spot develops into a blister, and later becomes sunken and whitish with a paper-like surface. Sunscald will occur frequently after pruning of tomato plants.

Once Sunscalded a tomato can not be "repaired" , but its progression can be slowed. You can leave exposed fruit on the vine and cover it with lightweight screen, shade cloth, or straw to protect if from further damage. You can also harvest them and allow them to finish ripening on a windowsill or kitchen counter.

If Scald is a problem in your garden there are a number of routes you can take.

•Don’t over-prune tomato plants, this exposes previously shaded fruits and remaining foliage.

•Traditional stakes and trellising will expose tomatoes to maximum sunlight, promoting sunscald. Cage tomato plants. Caging provides tomato support with very minimal pruning, so foliage can still provide shade .

• Tomato wilts, blights, and leaf spot cause plants to excessively drop foliage, which will expose tomatoes to excess sunlight. Maintain healthy tomatoes, treat problems ASAP.

•When the forecast is for extended hot, dry weather, shield plants with a lightweight screen, shade cloth, or straw to protect tomatoes from over-exposure

Tomatoes with sunscald are okay to eat, so long as Black mold hasn't set in , simply slice off the effected portion.



Tomato Yellow Leaf Curl virus

Tomato Yellow Leaf Curl virus is transmitted by sucking insects - whitefly in particular. It is not transmitted through seed or by external mechanical means. Infected plants will show stunted and erect growth. Early infection can lead to a severe stunting of the plants growth with little or no yield at all. Leaves are smaller than average and curl upward with marginal yellowing, as well as a yellowing of the veins near otherwise healthy appearing sections.

Use virus-and whitefly-free tomato transplants, as well as pepper plants, which are whitefly hosts. Transplants should be treated . Commercial growers can use dinotefuran or bifenthrin for Adults and Oberon for eggs and nymphs. These products are not readily available to the Home Gardener , there are several less potent products, and aphid ~ whitefly sticky trapssticky traps insects are also helpful in controlling populations.

Leaf roll

Leaf Roll generally develops in rainy periods. The lower leaves roll upward until the edges touch and become thick and leathery . Leaf roll is predominant in cool wet weather, excessive fertilizer, and pruning are contributory factors. Leaf Roll has no serious effect on plant growth or yield. Other causes of stress on a tomato plant that can cause leaf roll are

1. Sucking Insects. Such as aphids and whitefly which drain nutrients from a tomato plant. That's the reason the leaves they attack frequently appear yellowish and deformed.

2. Irregular or excessive watering and/or severe pruning can cause a tomato plant to develop thick, leathery upwardly curled leaves . The plant should re-adjust so long as horticultural maintenance is resumed.

3. Herbicide damage particularly from treatments applied to nearby lawns may cause tomato leaves to curl downwards and upwards. In this case, the plant may develop stunted growth, cat-faced fruit, and twisted leaves. If the exposure is minimal, these effects generally aren't apparent, and any damage will be outgrown.

Soil Rot

Soil rot, is caused by the a soil-borne fungus {Rhizoctonia} and generally occurs during rainy periods. A soft brown rot develops, usually on the sides of fruits touching the ground, or where soil is splashed onto them. The spots are sunken, large, and may have a closely-spaced bulls eye pattern . the center of the spot often cracks open. Staking and caging will reduce soil rot by keeping tomatoes away from the ground

Blossom end Rot

Blossom End Rot occurs as a slight discoloration or a severe dark sunken lesion at the blossom end; it is caused by temporary insufficiency of water and calcium and may occur under high temperature conditions when the plants are rapidly growing. Recommended treatment is Blossom End Rot Concentrate Blossom End Rot Spray which is effective in preventing the diseases spread and protecting future fruits.

Buckeye Rot

Copper Containing Bactericides are used to treat Buckeye Rot, Bacterial Spot, and Bacterial Canker

It maintains a "protective" coat on the foliage and fruit. Few strains of the pathogens are resistant

Buckeye Rot is caused by a fungus with a fancy Latin name {Phytophthora parasitica}. The fungus lives in the soil. Disease is most prevalent in poorly drained fields and in regions subject to prolonged periods of warm wet weather.

Buckeye Rot causes rots of tomato and related plants such as pepper and eggplant. The earliest symptom is a browning or grayish green water-soaked spot where the fruit has touched the soil. "Buckeye" bands are generally present within the infected area.

Bacterial Spot, and Bacterial Canker can reach epidemic levels during warm wet weather. Bacterial speck thrives during cool moist conditions. Bacterial spot can cause moderate to severe defoliation, blossom blight, and lesions on developing fruit. Bacterial speck also causes these symptoms but is usually not as severe as bacterial spot.

Bacterial Spot, produces circular scabby spots on immature fruits and on leaves. Tomatoes as well as Sweet peppers are effected. The bacterium is seed-borne and is often carried on diseased transplants. It can also occur in certain weeds . It overwinters in soil and on old tomato vines and pepper plants. Bacterial spot is favored by warm temperatures , high humidity, long dew periods, and driving rain.

Bacterial Spot produces circular greasy scabby spots on immature fruits and on leaves. Tomatoes as well as Sweet peppers are effected. The bacterium is seed-borne and is often carried on diseased transplants. It can also occur in certain weeds . It overwinters in soil and on old tomato vines and pepper plants. Bacterial spot is favored by warm temperatures , high humidity, long dew periods, and driving rain.

Bacterial Speck produces tiny brown circular specks. These specks are slightly raised and may occur on fruit or leaves. Tissues next to the fruit specks are slow to ripen. The bacterium is seed-borne. Infection by bacterial speck is favored by temperatures of 65 to 75 F, dew and high humidity; disease development is favored by temperatures of 55 to 77 F.

copper based fungicidesCopper Based Fungicides provide partial disease control. Apply before rainfall and repeat at 2 week intervals when cool and moist conditions prevail.

Bacterial Canker causes wilt, vascular discoloration, scorching of leaf margins, and lesions on fruit. The organism is seed borne and can survive for short periods in soil, greenhouse structures, and equipment and for longer periods in plant debris. It is rare and can devastate a garden. Treatment and prevention is the same as speck and spot.

Tobacco Mosaic causes leaves to be mottled light and dark green. The plants are generally stunted and the leaves rough. The tomatoes do not always show symptoms but may be reduced in size and ripen unevenly.

Fungicides are not effective in controlling Tobacco Mosaic, there are no known efficient chemical treatments that protect plants from this virus. Control of tobacco mosaic virus depends on reducing and eliminating sources of the virus and limiting its dissemination by insects.

Cucumber Mosaic , Early symptoms are yellow, bushy and stunted plants. Later symptoms are similar to tobacco mosaic except that leaves are frequently elongated, narrow, and distorted to form a "shoestring" effect.

Most Disease problems can be greatly Reduced with a combination of practices that include:

1. ] Purchase vigorous, healthy plants from a reputable supplier. Tomatoes, being susceptible to diseases,viruses and insects, some varieties have been bred or hybridized to be resistant to certain pests.

Resistance to these pests is usually listed on the plant label or seed packet using the following abbreviations:

V = Verticillium Wilt

F = Fusarium Wilt

FF = Fusarium Wilt race 1 and 2

N = Nematode

T = Tobacco Mosaic Virus

A = Alternaria (Early Blight)

TSW = Tomato Spotted Wilt

Organic Gardener's Handbook of Natural Pest and Disease Control - ISBN-13: 978-1605296777

Remember that resistance to these problems does not mean they are 100 % immune, good cultural practices are still important.

2.]Crop Rotation in your garden planting area

3.] Remove and destroy all plant refuse in the fall and use deep cultivation to bury any remaining refuse.

4.] Do not place diseased plants in the compost heap, as this will only serve to carry bacterial or fungal infestation into the next growing season.

5.] Avoid over watering . Use surface watering methods. Do not handle plants when the vines are wet.

6.] Weeds compete with vegetables for soil moisture and nutrients and also serve as hosts for insects and disease carrying bacteria and fungus. Control weeds in and around the garden .

7.] Control insect pests such as aphids, which are known to transmit diseases from plant to plant.

8.] Use plastic ororganic mulches to reduce disease and blossom-end rot problems.

9.] Choose a sunny location for your tomatoes. Leaf disease problems are much less likely to occur in a sunny location than in a shady one.

10.] Apply recommended fungicides according to label directions at the first sign of leaf spot diseases

11.] Remove abnormal or unhealthy appearing plants as soon as they are observed. To reduce the spread of suspected diseases wash hands and tools with a mild detergent after handling suspect plants.

 




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