Basil downy mildew Patch#
Basil downy mildew full#

To help home gardeners cope with that, McGrath suggests growing basil in containers that you can bring indoors on rainy days and humid nights. Dew that forms on humid evenings is particularly troublesome because it creates especially favorable conditions, and there’s nothing you can do to prevent it. Try not to crowd plants and avoid getting the foliage wet when watering.

Basil downy mildew full#

Basil prefers full sun and good air circulation. The second line of defense is to keep foliage dry. Other recently released varieties reported to be resistant include Pesto Besto and variants on Prospera with different leaf types. Sweet basil varieties that have shown good resistance in trials that McGrath has conducted on Long Island include Prospera and Amazel, as well as resistant varieties developed at Rutgers University: Devotion, Obsession, Passion and Thunderstruck. Sweet basil is more susceptible than spice types such as lemon or cinnamon basil. The first line of defense is to grow varieties that are resistant to the disease. While there’s no vaccine for basil downy mildew, there are practical steps both commercial growers and gardeners can take to reduce the devastation. Urban crops are not immune, as McGrath regularly receives reports of symptoms on basil grown high up on city apartment balconies.

High humidity common during Northeast summers also favors infection. “It’s not easy to escape basil downy mildew because the spores are so well dispersed by wind,” said McGrath. What makes the disease so devastating is that these spores can quickly spread far and wide on the wind to infect plantings miles away. But before they do, the undersides become covered with copious amounts of dusty brown spores. The leaves soon turn entirely brown and fall off. While not harmful to eat, infected leaves lack the full flavor and deep green color of healthy leaves. (See images in slideshow below.) This is sometimes misdiagnosed as a nutrient deficiency. Leaves on infected basil plants turn yellow between the veins. It hopscotched through Europe and then jumped to Florida in 2007 (likely through contaminated seeds) the fall before McGrath found it on Long Island. It was first noted in Uganda in 1932, but wasn’t reported again until 2001 in Switzerland. “Knowledge about where and when a disease occurs is important for management,” said McGrath.īasil downy mildew is caused by Peronospora belbahrii, a fungus-like oomycete, one of a group of microorganisms that includes some of the biggest threats to global food security and natural ecosystems. Since that season, McGrath has been on a mission to help growers and gardeners fight the disease, enlisting their help to track and limit its spread. The color did look a little brownish, likely due to spores he didn’t notice on the underside of the leaves.” Wind speeds spread “And I also wondered about the batch of pesto my husband made and froze while I was away. “But I was scientifically intrigued by the quick spread of this new pathogen in the United States. “It was sad to see what had been a beautiful basil crop rendered unusable by this new disease,” she said. The culprit: basil downy mildew - an imported plant disease that had recently arrived in the U.S. And the grower’s crop was totally unmarketable. By the time McGrath returned home, she discovered the basil in her own garden was infected. McGrath was attending a scientific meeting in Europe when a colleague forwarded a concerning email from a Long Island herb grower. But that is exactly what happened to Meg McGrath, a plant pathologist based at Cornell’s Long Island Horticultural Research and Extension Center, in August 2008.

Basil downy mildew Patch#

Nothing spells disappointment more during pesto-making season than visiting your basil patch only to find your carefully tended crop ravaged.