Late Blight is a water mold that infects plants and can devastate a farmer’s tomato or potato crops. Knowing how to identify late blight in your garden or field is a crucial skill.

It’s important to always be aware of the spread of late blight. You can monitor current outbreaks of late blight in the US here.

There are fungicides available to treat crops in the attempt to prevent a late blight infection. For organic farmers there is another alternative.

A Word from an Organic Farmer

Local CSA (community supported agriculture) farmer Sara Kurak gives some advice to fellow farmers and gardeners about this enemy of plants. From her experiences at Full and By Farm she has learned that the only organic preventive for late blight is copper. Strange, right? But apparently it works.

“If you haven’t heard the news yet, late blight is back in the area. Showing his ugly mug in Clinton county, as well as south of us. We’ve just started spraying the tomatoes with copper, which is the only approved organic treatment for late blight. Despite it’s being naturally derived, it is still really bad for you to ingest, breath, touch or get in your eyes. We’ll rinse the fruit before the share but you should make sure to wash it carefully before eating […]

Late blight first showed up four years ago in some starter plants in the box stores, and has reappeared each year since. It looks like it may be here to stay. If you have tomatoes, potatoes or eggplants at home check them daily for spores and lesions. Bag up the plants and take them to the dump immediately if you find any signs.” [Sara Kurak from Full and By Farm]

If disease becomes severe it may be necessary to destroy your infected plants to prevent spread to nearby gardens and farms!

“Once 5 to 10 percent of the foliage is infected it is usually not possible to halt the development or progress of the disease. […] Only weather that is very dry and hot, both day and night, might temporarily stop the epidemic. […]

Growers can attempt to salvage apparently uninfected tomato fruit but should be aware that some fruit infections will not become visible for several days. Foliage in such fields should be promptly destroyed to prevent spread to nearby fields or farms.” (Cornell late blight fact sheet)

Late Blight Treatment Steps

Here it is in important step-by-step format:

• Always be on the lookout for signs of late blight!
• If you notice it in your leaves, trim them off infected parts and place them in a plastic bag on site. Don’t carry them to the trash without a bag or you will be infecting more of your garden!
• Throw in trash! Don’t add to compost!
• Notify nearby gardeners and farmers that late blight is in the area.
• Synthetic chemical fungicides–Conventional treatment that will kill the late blight growing in the plant tissue. Must be continually applied.
• Copper fungicide–an organic treatment that is a preventive against late blight. If you already have it in your garden it may be too late to try this option! So listen to the news and as soon you get word that late blight is approaching your area start spraying the preventives.

Have you had any late blight in your fields or garden this summer?

Do you know of any alternate treatments? Or have an opinion on the use of organic vs. non-organic options?

Related articles

• Recognizing Late Blight
• Full and By Farm: Late Blight Update