Blight

What is Blight? It is simply a rapid and complete chlorosis, browning, then death of plant tissues such as leaves, branches, twigs, or floral organs. There are many types of fungal and bacterial blight. It is caused by a fungus-like organism which spreads rapidly in the foliage and tubers or fruit of potatoes and tomatoes in wet weather, causing collapse and decay. It is also common in trees, fruits, rice, and grass.

Symptoms of Early Blight Leaves Initial symptoms appear as 1-2mm black or brown lesions and under conductive environmental conditions the lesions enlarge and are often surrounded by a yellow halo. Stems Lesions occurring on stems are often sunken and lens-shaped with a light-center, and have the typical concentric rings.

How to Prevent Blight In many cases sound cultural practices that maintain potato and tomato plants in good health and will keep early blight losses below economic levels. Controlling volunteers and weeds, as nightshade and horsenettle which serves as alternative hosts for the disease, prior to planting the new crop will help to reduce the risk of transmission of disease. Ensuring seeds or transplants are pathogen free before placing out in the field and rotating fields to non susceptible host crop will also help to reduce build up of inoculum in the soil. Complete Blight resistance does not exist yet.

How to control a Blight outbreak Early blight control is based on crop rotation, removal and destruction of crop debris from previous crops, staking, mulching, and timely application of fungicides. Staking keeps foliage and fruit from contacting the soil surface. Mulching cuts down on "soil splash" onto lower parts of the plant. Plastic, or organic mulches (pine straw or even newspapers) are equally effective. Application of fungicides is also generally needed for early blight control; chlorothalonil, maneb, and mancozeb fungicides.