Pest Control Library: Late Blight

Articles→Pest Control Library

By National Gardening Association Editors

Late blight strikes tomatoes and potatoes all over North America at any stage of growth. Irregular gray spots form on leaves. White mold grows on the undersides of these spots. Infected leaves turn brown and dry up. Gray, water-soaked spots on infected fruits later turn dark brown and corky. Infected tubers are covered with brown spots where rot begins. Wet weather with cool nights and warm days favors the spread of the disease. The fungus overwinters in infected plant debris.

Prevention and Control

Fertilize judiciously, as excess nitrogen favors the disease. Avoid overhead watering. Eliminate infected plants with a flame weeder to prevent further spread of the disease. After potato vines die at the end of the season, wait a week before harvesting to avoid infecting tubers. For early harvest, first destroy plant residues with a flame weeder before digging tubers. Copper fungicides such as Bordeaux mixture are effective as a preventive when applied as directed on the product label, and may afford control if applied as soon as infection occurs. It's best not to depend too heavily upon this method of control, as copper can build up in soil to levels toxic to earthworms and microbes.

Photo courtesy of William M. Brown Jr., Bugwood.org

Together with Victory Seed Company:
Victory Seed Company Logo Victory Seed Company has all the seeds you want for your best garden in 2024.

For 25 years, the family-owned Victory Seed Company has provided the highest quality vegetable, herb and flower seeds to families across the country. We are passionate about providing you the best seeds available that give excellent germination, robust plants, and the harvest you want. With a catalog of over a thousand varieties, we have everything, and our prices are the kinds that we'd want to pay. We have hundreds of yesterday's heirloom vegetables, as well as today's award winning hybrid selections. Get to know us by visiting our website and browsing through our online vegetable seed catalog.

This article is a part of our Pest Control Library.
This article is a part of our Pest Control Library.
Member Login:

( No account? Join now! )

Today's site banner is by adknative and is called "Baby Blue Eyes"

This site is protected by reCAPTCHA and the Google Privacy Policy and Terms of Service apply.