Saturday, April 14, 2012

Strawberries and Leaf Spot

If your going to grow strawberries, then you need to learn how to control Leaf Spot, Leaf Blight and Leaf Scorch. I am just beginning to learn. In this post I will focus on Leaf Spot since that is what I am battling.

Source of the following information:

Start of source material:

Fungal diseases of the leaf may occur as soon as the first leaves unfold in early spring and continue until dormancy in the late fall.

The primary damage from leaf diseases is a loss of vigor through reduced leaf area. If outbreaks of these leaf diseases become significant, the plants will become weakened resulting in increased susceptibility to root diseases and winter injury.
The three major leaf diseases that are caused by fungi have a similar disease cycle and are controlled in a similar manner. Leaf spot, leaf scorch, and leaf blight are the most common leaf diseases and they all overwinter in infected dead or living leaves. They all produce spores that spread the disease by causing new infections during moist, warm conditions.

Strawberry plants looked wonderful only a month ago in March when I first removed the winter protection

Little did I know that the fungus that causes Leaf Spot was already present and multiplying

Leaf Spot appears in April

I have since learned that you need to treat strawberry plants with a every 10-14 day regiment of fungicide spraying from the moment you uncover them in spring to the time when they begin to flower. This for me is 3-4 spray events. 

Leaf spot is caused by the fungus, Mycosphaerella fragariae.

Symptoms of leaf spot first appear as circular, deep purple spots on the upper leaf surface. These spots enlarge and the centers turn grayish to white on older leaves and light brown on young leaves. A definite reddish purple to rusty brown border surrounds the spots.

The fungus overwinters as spores in lesions on leaves. The fungus infects the plant and produces more spores in spots on the upper and lower leaf surface that spread the disease during early summer. These spores are spread by splashing rain. Middle-aged leaves are most susceptible. Lesions also develop on stems, petioles and runners.


Leaf spot and leaf scorch are controlled most effectively by the use of resistant varieties. The following junebearing varieties are reported to be resistant to both leaf spot and leaf scorch: Allstar; Canoga; Cardinal; Delite; Earliglow; Honeoye; Jewell; Lester; Midway and Redchief. The ever bearing varieties, Tribute and Tristar, are reported to be tolerant to leaf spot and leaf scorch. There are no varieties varieties with reported resistance to leaf blight. These cultural practices should help reduce infection:
• Remove the older and infected leaves from runner plants before setting.
• Take care in spacing runner plants in matted-row culture.
• Plant in light, well-drained soil in a location exposed to all-day sun and good air circulation.
• Control weeds in the planting. Weeds reduce air circulation and increase drying time for leaves. (Leaves stay wet longer in weedy plantings.)
• Removing infected leaves after harvest (during renovation) is helpful in reducing inoculum and controlling all the leaf diseases.
If leaf diseases are a problem in the planting, fungicides will aid in control. However, the emphasis on control of leaf diseases should be placed on the use of resistant varieties. For the most current fungicide recommendations and spray schedules commercial growers are referred to Bulletin 506-B2, Midwest Commercial Small Fruit and Grape Spray Guide, and backyard growers are referred to Bulletin 780, Controlling Disease and Insects in Home Fruit Plantings. Backyard growers are encouraged to use resistant varieties. This should eliminate the need for using fungicides to control these diseases.

End of source material:

Ok, so that is great information. I can rely on everything it states about what Leaf Spot is, where it comes from, and what it looks like. What it looks like is the most important, the first step to control of a disease that is attacking your crops is to positively and accurately identify what it is. The two pictures above I took this morning, from my own strawberry plants and there can be no doubt what the problem is. It's Leaf Spot that is for sure.

So having said that, it's the part about control in the source material above that I have a problem with. They emphasize control by planting resistant strains. What a bunch of crap. They want you to tow that line because they don't want you to use chemicals in the home garden any more than is absolutely necessary. They want that to be the last resort.

What a bunch of nonsense. That kind of thinking is the fastest way to lose your crops. My feeling is at the first sign of disease break out the biggest baddest gun you have available to you. Apply it fast, strong and often.

Organic? Yea right, I tried that last year when I was at war with Cucumber Beetles and Squash Bugs that were attacking my young Cucurbits. I almost lost everything in that family of plants. The Beetles and Bugs just laughed at the organic sprays I used. The only thing that saved them was that out of desperation I turned to the chemical spray "Seven". Thank God for Seven. I ended up with a decent crop harvest only because of Seven. I will never rely on "Organic" for pest or disease control again.

So back to Leaf Spot...

Needless to say, the first thing that I did after identification is to research what Chemical I should use to battle Leaf Spot on Strawberries. The end result of my research was that there are a plethora of available chemicals that are recommended. Some available to the home gardener, some only available to the professional. I settled on the chemical fungicide Capton. It's a wettable powder, that means it comes in powder form, which can be used as is, or mixed with water to apply as a spray. I intend to use it as a spray. Applying anything as a powder is a pain in the ass, and wasteful. You always end up applying more powder than you need to. Half of it goes to the wind. Sprays are much more controllable.

So to conclude I ended up ordering 5 containers of Capton from the Internet, i.e., I love Amazon. I hit my strawberries with what fungicide I did have on hand in the meantime. I will post in a week or two the results of my battles with this disease.

Just sprayed with fungicide. The fungicide makes a milky spray, you can see it on the leaves after the treatment.

This is a new post...
To follow up, spring of 2012 I had a major infestation of Mycosphaerella fragariae otherwise known as Strawberry "Leaf Spot". Don't know why. What I can tell you is that Capton solved it. After two applications, my plants looked 100% better. After four, leaf spot was gone. Replaced by new wonderful looking growth. Without leaf spot.

Now this year, I experienced NO leaf spot in my strawberry patch. Don't know why. What I can tell you is I did not cover my strawberries last winter. The winter before I did what they recommend, I covered my entire patch, late fall with four inches of straw for winter protection. This past winter I did not do that, I was simply too tired at the end of last year. I hoped I would not lose my entire patch because of laziness. 

I found that the plants stayed green all the way through the worst of the winter. Through the cold,   wind and under snow. Early January they began to turn brown. By early February  all the leaves were brown. I thought the worst. I thought I lost my patch. But by March, they began to produce new growth, new bright green leaves. I was elated. By the middle of April, my patch was back, lush green and strong. I looked closely, I looked with determination, and I could find no indication of leaf spot. 

So I sprayed the entire patch with Captan anyway, except for one row. A week later I sprayed it again, except that last row. Again all I can tell you is this year, I have had no indication of, nor been bothered by Mycosphaerella fragariae otherwise known as leaf spot. Including the last row.

I don't think I will cover my strawberry patch this coming winter.

Update for this year...
Again last fall I did not cover my strawberry plants. And again they seemed to weather the winter cold and snow just fine. There was considerable browning and loss of foliage come spring, when spring finally arrived as we had a long hard winter, but all in all they did just fine and came back lush and green. And again I have not been bothered by leaf spot. Not even a little. Plants are now just starting to flower and I am convinced that not covering them is the way to go. Something to do with covering them encourages leaf spot. The following are a few pictures of this years crop;


  1. Good information. I think I will get some Captan since my strawberries always get spotty.

  2. Good information. I think I will get some Captan since my strawberries always get spotty.