Are you having trouble getting your basil to grow and flourish this year? Many people who have grown bountiful, trouble-free basil crops year after year are now finding it difficult or even impossible to get their basil plants to thrive.
These gardeners and growers haven't lost their green thumbs: their basil is probably being impacted by a disease called Basil Downy Mildew which is devastating basil crops across the United States as well as in countries across the globe. This disease made its first documented North American appearance in 2007 and has been causing basil crop failures ever since. It affects farmers and gardeners alike, and it looks like it is here to stay.
How Can I Tell if My Basil Has Downy Mildew?
the first signs of downy mildew are a yellowing or sunburned appearance on some of the plant's leaves which can easily be confused with nutrient deficiency or sunburn. In the fullness of time, this yellowing is followed by greyish, downy-looking spores on the undersides of the plant's leaves. These spores are very distinctive and are a pretty sure sign that your plants have been infected with downy mildew.
Downy mildew can infect plants from the moment the emerge, so even very young basil sprouts or seedlings may can already be suffering from the disease.
How Does Basil Downy Mildew Get into My Garden?
According to organic crop specialist Dr. Eric Sideman, downy mildew spores survive year round in warm climates and can become windborne and travel very long distances that way. Downy mildew spores may also be present on seeds as well as travel to your area on basil leaves or plants being sold in grocery stores or garden centers. Once they make it into your garden, the spores can survive for many years in your soil, even if your area has a cool climate.
What Should I Do if My Basil Plants Get Downy Mildew?
If your plants become infected with downy mildew, it is just about impossible to eradicate the disease. Once the disease takes hold, even fungicides won't provide much help to the plants. Therefore, the official recommendation for what to do if your basil plants have downy mildew is to simply pull the plants out and dispose of them. Cornell University keeps tries to keep track of reports of basil downy mildew outbreaks, no matter where they occur--even if the outbreak is in a home garden. If your basil plants have downy mildew, you can report it to Cornell by using their online form at http://vegetablemdonline.ppath.cornell.edu/NewsArticles/BasilDowny.html#Report
Is There Any Way to Increase My Chances of Having a Successful Basil Crop?
Like many other types of mildew, downy mildew thrives in dark, moist environments. Accordingly, growers have had some success growing the plants under 24 hour lights in a greenhouse setting. Home growers with a greenhouse or maybe even an Aerogarden type indoor unti may want to try this method.
Fungicides (both conventional fungicides and those approved for organic growers) can be somewhat effective at limiting the damage caused by this disease, but they must be applied before an infection occurs and then at intervals throughout the growing season. Initial research indicates that fungicides are unlikely to be able to completely prevent this disease, though they will reduce the amount of damage that plants suffer. Still, any mildew on a basil leaf is unappetizing, so fungicides aren't necessarily the best solution for a basil downy mildew outbreak.
Most varieties of basil, including ornamental basils and Thai basils are very succeptible to basil downy mildew. However, basil varieties with some resistance to downy mildew are being developed. One of the first to hit the market is Eleonora, a pesto type basil.
Growing a variety of basil that shows some resistance to this disease as well as making sure that your plants have plenty of air flow and light are some good bets for increasing the odds of getting some basil harvested from your crop.