Anthracnose of the Tomato Plant: Identification, Control & Prevention

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Quick Answer: Anthracnose of the Tomato Plant

Anthracnose disease of the tomato plant is a fungal plant disease. It damages the root and fruits of the tomato plant. There is no permanent cure for this disease, but several cultural and chemical methods are now used to check its symptoms.

This is a handy manual on the anthracnose disease in the tomato plant.

Let us get started!

What is Tomato Anthracnose Disease?

The causative fungus for anthracnose disease is Colletotrichum coccodes. This disease is common worldwide. C. coccodes has a wide host range. It is saprophytic and depends on 68 plant species and 19 families belonging to the Solanaceae family. 

It severely harms every part of the tomato plant and lowers its yield and market value.

Anthracnose disease of the tomato plant is soil-born. However, some studies suggest that the disease may also be seed-borne. 

The severity of the disease occurs above 38°C. The germination of the spores on the fruit takes place at 28°C. High humidity, rain, warm temperatures, and water on leaves support the disease development.

The dispersal of sclerotia is through wind, water, contaminated seeds and soil, and infected tools. 

Sclerotia (compact mass of hardened fungal mycelium containing food reserves) germinate on the roots, stems, leaves, and fruits of the tomato plant. It grows and produces conidia. Conidia are the infecting structures of anthracnose.

Conidia develop on leaves and fruits. Within a week, symptoms developed on red and green tomatoes.

The colonies of the Colletotrichum coccodes are darkly pigmented with aerial mycelium, consisting of numerous black sclerotia [fruiting bodies].

The conidia are straight, fusiform, and attenuated at the ends. They produce on the hyphae mat of sclerotia. 

Appressoria are clavate, brown, variable in shape, and help penetrate conidia into parenchyma cells of the tissue. 

How Anthracnose Harm Tomato Plants?

C. coccodes survive in soil debris and infected plant debris. Sclerotia are the resting spores of Anthracnose disease. They remain in the soil for three to four years.

The fungus is also found on the roots of various plants and in water used for crops and open storage tanks. 

The sclerotia produce mycelium or acervuli [asexual structures that gives rise to conidiophores].

Acervuli germinate on green and mature fruits. They reach the plant tissues through the cuticle. They can also take advantage of minor wounds present on mature tomatoes.  

The conidiophores are disseminated by water splashes from rain, overhead watering, and equipment used in the garden. 

The conditions favouring the spread of anthracnose are –

  • Temperatures between 15 and 30°C
  • High Humidity [ 85- 100%]
  • The wetness of plants.

Check out this video for anthracnose disease of the tomato plant –

How to Confirm that Anthracnose is Troubling your Tomato Plants?

The symptoms of the disease are frequently seen on roots, ripe and over-ripe tomato fruits. However, it affects stems, roots, petioles, green fruits, and ripened tomato fruits.

The symptoms of tomato fruits are not prominent until they are ripe. 

Anthracnose Symptoms on Fruits

On fruits, symptoms appear at maturity as tiny light brown lesions, which grow into small, moist, dull, and circular spots. 

As the spots enlarge and reach up to ½ inch in diameter, they become concave and brown. These lesions are sunken. 

These concave dark brown lesions are the spore-producing bodies (acervuli) of the anthracnose disease. These lesions are covered with dot-like spots called microsclerotia.

The grainy texture is observed beneath the skin of the tomato. Various brown spots appear on one tomato fruit. The clusters of such spots fuse and give a rot-like appearance.

Unfortunately, the diseased fruits die within a short period of time.

Anthracnose Symptoms on Roots

Roots develop brown lesions. The cortex of the primary roots may show dark brown lesions that are corky.

The root lesions also show brown, dotted, and black fruiting bodies called microsclerotia.

Roots are weak, discoloured, and might show signs of decomposition.

Anthracnose Symptoms on Stem & Leaves

The base of the stem shows rotting. After the desiccation of the stem, the central vascular cylinder of the cortex appears to be split in half.

Leaves show small, circular spots which are surrounded by a yellow halo. Eventually, the leaf wilts and dies. 

Ways to Control Anthracnose Disease on Tomato Plant

Anthracnose is a destructive disease and can make a plant die within weeks of infection. The control treatment should be done as soon as the first sign of the disease is spotted.

Soil solarization

Soil solarization is the most effective way of checking disease severity. It is an easy, eco-friendly, and economical method of soil treatment.

In this method, the soil is mulched with a layer of plastic sheets and is left undisturbed for a month. It is a heat treatment and, therefore, requires constant sunlight.

The prerequisite for the soil solarization method is to keep the soil wet for at least 10-12 inches deep. 

Fungicide treatment

Fungicide treatment is performed pre-harvesting and during harvesting. The fungicide should contain solutions of carbendazim or thiophanate-methyl for effective results.

Copper-based fungicide is a good alternative to commercially accepted fungicides. However, copper should be used very carefully.  

Always check the instructions before the fungicide treatment.

Check out this video for fungicide treatment-

Using Resistant varieties

Use commercially available resistant seeds. They will reduce the risk of disease development in tomato plants.

Soak the regular seeds in 122-degree Fahrenheit hot water. Put them in cold water and dry them with a paper towel.

Volatile Natural Compounds

Some studies have shown the effectiveness of volatile natural compounds in the reduction of anthracnose symptoms.

Absolute ethyl alcohol, vinegar, chlorine, or origanum oil reduces fungal spore germination in anthracnose disease. They can be used in post-harvesting sanitizing sprays.

Check out this video for anthracnose treatment-

How to Prevent Anthracnose on Tomato Plant

Though there is no way you can recover your tomato once they have developed the infection, you can do some practices to prevent the disease. 

Check out this video for the prevention of anthracnose –

Tips to Prevent Anthracnose

  1. Stake your plants with a wooden rod to provide physical balance and good ventilation to the plants. It is also essential to provide enough spacing between your plants.
  2. Mulch your tomato plants with organic matter. Mulching is a great way to achieve desired distance between soil and plant. 
  3. Gently water the roots of the plant. Avoid watering your plants in the evening. Try to keep the leaves of the plant dry. 
  4. Disinfect your soil using soil solarization before planting any new tomato seeds.
  5. Carefully remove and destroy diseased plants and their roots. Burn all the infected plant debris in a burn pile. Remove all the rotten fruits, and do not let them fall on the ground. 
  6. Rotate your plants every two to three years.
  7. Do not work with the plants when they are wet.
  8. Remove all the weeds before harvesting and after harvesting the tomatoes.

FAQ’s

Do green tomatoes show signs of anthracnose spotting?

No, the green tomatoes develop the disease but do not show the symptoms till they are ripened.

During which season can we expect the early signs of anthracnose?

In late spring, when the temperature is moderate, and humidity is high, sclerotia germinate on leaves and show their developmental signs.

Can tomatoes develop the symptoms of anthracnose after harvesting?

Yes, ripe tomatoes can develop new signs after the harvest.

How can we differentiate between blossom end rot and anthracnose disease of the tomato plant?

Sclerotia, the fruiting bodies of anthracnose, are brightly coloured than dull and sunken black blossom end rot. 

Do disease-free tomato seeds guarantee that they will not develop anthracnose?

No, there is no tomato variety completely resistant to anthracnose.

Summary

I hope this guide will help you identify & managing anthracnose tomato disease.

If you have any tips which I have missed, please drop us a line!