Early Blight

Class: Fungi

Common Name

Early blight

Scientific name

Alternaria solani

Potential Hosts

Members of the solanaceae family, but mainly found on tomato, potato, eggplant, and okra

Who am I?

When it comes to tomato and potato plants, early blight is one of the most prevalent fungal diseases in the world. Early blight can be found wherever tomatoes and potatoes are cultivated. The pathogen, Alternaria solani, can survive on plant debris that were left behind in fields. Additionally, several weeds serve as potential sources of infection.

An early blight infection is likely to occur during periods of warm and humid weather. The fungus is able to penetrate plant tissues through cuticle, stomata, and injured tissues. Symptoms can be seen within several days after the initial infection. Generally speaking, the infection starts on older leaves causing typical concentric necrosis rings. As the disease progresses, a formation of yellow halos can occur around the spots. When left untreated, the infection leads to substantially dry canopies and deformed and unmarketable fruits.

Control measures


Working with resistance cultivars: Not all tomato and potato varieties have the same early blight resistance.

Sanitation: Make an effort to clean and maintain your fields’ close surroundings from weeds as often as possible.

The sooner the better: It’s easier and more cost effective to overcome early blight and control it during the initial stage of infestation. Make it a routine to monitor the field regularly and search plants for the presence of the above symptoms on a weekly basis.

As with any moisture-favoring disease, various agro technical measures can be taken during crop growth to reduce the chances of an infection and spread:

Improve air circulation: In closed structures, promote the drying of foliage and shorten the duration of wetting periods by introducing net curtain vented areas.

Proper soil drainage: The presence of standing water will promote the spread of late blight.

Cover the ground with polyethylene sheets to reduce water evaporation from the soil.

Conventional (chemical)

The following are fungicides used in one or more parts of the world: chlorothalonil, iprodione, difenoconazole, cymoxanil, famoxadone, azoxystrobin, thiophanate methyl, pyraclostrobin, tebuconazole, mancozeb, and maneb.


It is difficult to manage early blight organically. Growers should be aware of the risks they take by choosing organic methods and invest time in cultural control measures. Though, Trichoderma polysporum and various Bacillus species are reported to have some capabilities to control early blight.

Caution and careful notice should be taken when using any plant protection products (insecticides, fungicides and Herbicides). It is the grower’s sole responsibility to keep track after the legal uses and permissions with respect to the laws in their country and destination markets. Always read the Instructions written on the label and in any case of contradiction work with accordance to the product label. Keep in mind that information written on the label usually apply only to local markets. Pests control products intended for organic farming are generally considered to be less effective in comparison to conventional product. And so one must keep in mind that when dealing with organic, biologic, and to some extent a small number of conventional chemical products that a complete eradication of a pest or a disease will often require several iterations of a specific treatment or combination of treatments.

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