Late Blight Alert


Look for the spreading of brown to black lesions on leaves surrounded by a thin halo of brighter pigmentations. Green fruits are more vulnerable to infection and could become marble-brown in appearance and the fruit becomes hard. In high humidity conditions, gray to white “fluff” will appear around the edges of darker lesions.

Who Am I?

Late blight is a fungal disease, has the potential to destroy entire fields, and favours periods of heavy rainfall and high humidity.

Control Measures

Prevention spraying (pre-visible symptoms) is your main strategy. When conditions appear favorable for late blight or such conditions are expected in the upcoming days, spray applications of fungicides (based on one or more of the following generic active ingredients) in 5 – 7 days intervals: chlorothalonil, cymoxanil, dimethomorph, iprodione, azoxystrobin, propamocarb HCL, mandipropamid, copper hydroxide, and sulfate.

*Never perform two consecutive iterations with the same active ingredients.

It is extremely difficult to manage late blight organically. Organic growers should know the risks they are taking and do all they can in the cultural aspect. Though, some copper-based fungicides are considered organic and can be utilized.

*Names marked in red are considered to be highly poisonous to beneficial insects.

*Names marked in green are considered to be organic and IPM (integrated pest management) compatible.

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 of the legal uses and permissions with respect to the laws in their country and destination markets. Always read the instructions written on labels, and in a case of contradiction, work in accordance to the product label. Keep in mind that information written on the label usually applies to local markets. Pest control products intended for organic farming are generally considered to be less effective in comparison to conventional products. When dealing with organic, biologic, and to some extent a small number of conventional chemical products, a complete eradication of a pest or disease will often require several iterations of a specific treatment or combination of treatments.

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