All About Leafy Greens: Common Leafy Green Diseases

Disease is a particularly important consideration when growing leafy greens because – as their name indicates – the delicate leaves are the part of the vegetable you’ll most likely want to eat.

Keep an eye out for any of these common diseases affecting your leafy green crop.

Downy mildew – Most often affecting mustard, collards and kale, downy mildew can kill your plants in just a few days. It first appears as a fluffy white mold on the underside of leaves, with the upper side eventually turning yellow and papery. The disease is transmitted through infected seeds, weeds and other plant debris, or the spores can be blown in from elsewhere. Weeding is key to prevention. If you can’t completely eradicate the weeks, turn them under the soil after harvest. A fosetyl-al based fungicide can be used to control the disease.

Alternaria Leaf Spot – Common in collards, kale and mustard greens, this disease is indicated by tiny dark spots on older leaves. The spots eventually turn black and broaden to two or three inches in diameter. The leaves may eventually display a greenish black or brown fungal mold.The disease can be transmitted on seeds, garden debris or weeds, and spores can be blown in from elsewhere. To prevent alternaria leaf spot, rotate cruciferous crops through the garden, never growing in the same spot others have been grown in the last three years. Start fungicide treatment as soon as signs of the disease develop.

Black Rot Black rot is indicated by bright orange or yellow v-shaped areas on leaf edges, particularly affecting greens like cabbage. Plants infected early display lethargic growth and their veins turn black. Black rot survives in soil for up to a year and is spread most effectively in warm, wet weather. Since there is no effective treatment for black rot, make sure you start off your planting by using disease-free seed.

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