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Tragedy in the Garden- Late Blight!

Tragedy in the Garden- Late Blight!

I had to do something horrible this year, I pulled all of my tomato plants!   They got hit by late blight and became a big, ugly  mess.  The only gift in it was that I did not have much space for a fall garden and it opened up some space for broccoli and cauliflower.  I have heard of lots of people getting late blight. The climate of the west county is perfect for blight to thrive in, 70’s and high humidity are its perfect climate, which is what this summer with dense fog and cool days has been.  I think it is much more rare as you go inland, but when I googled it I read of many places throughout California struggling with it, it seems to have become much more pervasive in the last few years.

When gardeners on the West Coast refer to "blight", they usually mean the disease called "late blight", caused by Phytophthora infestans. This disease is famous as the cause of the Irish potato famine in the 1800’s. Phytophthora infestans is not a fungus or a bacterium or a virus. It belongs to a group of organisms called "protists", although they are still commonly referred to as "fungi". They are also called "water moulds" because they thrive and produce spores under humid, moist environment and cause infection only when free water is present on the plants. (fog on the leaves!)

In tomato, the first symptom on plants is often a brown/black lesion on the stem or petiole. Leaves develop large brown/black blotches, often starting at leaf margins. In humid weather and in early mornings, a fuzzy mould can often be seen on the underside of the brown/black blotches or on the stem lesions. This fuzzy growth contains structures called sporangia containing spores of the pathogen. On tomato fruit, infection causes a brown/black, leathery rot.

 My tomato plants started with the leaf blotches and then the stems started to have sections of brown, which grew.  Eventually the majority of the plant just looked dead, that is when I finally gave up and pulled them.

Sometimes if you get a heat wave, tomatoes can out grow the blight and you can get tomatoes.  This year that did not happen. 

Blight moves in the wind and water, it also can live in the soil of our mild winter areas. 

 Things to do to prevent blight:

1)   Rotate the location of your tomatoes, which you should do with all your crops.

2)   Water with drip, overhead water is the worst thing you can do if there is blight around.  ( Which is what I did, my drip system stopped working and I overhead watered a few times, and down they went).

3)   Leave space between the plants for good airflow.

If you have had blight, what you should do:

1)   it is highly recommended to pull out the plants immediately so they don’t spread to your neighbors.

2)   Rotate the location of your tomatoes, and consider putting them into a raised beds, plants in raised beds seem to get blight less.

3)   Clean up all the plant debris, and don’t let any wild potatoes overwinter.

There is really nothing you can do once you have it, some people recommend spraying with copper if the conditions are prime for blight but that is only for prevention, it doesn’t do much once you have the disease.  

If you are wondering if you have late blight, this website had some good pictures: http://www.tomatoville.com/showthread.php?t=19658 

Or just google late blight in tomatoes and you can see lots of photos.


One last thing, you can still plant fall salad greens, lettuce and beets.  It is almost too late to plant broccoli, cabbage, cauliflower.  Kale and chard from starts will probably do well.  Remember it is the shortening day length that slows down the growth not the temperature.  By the end of September our days are too short for most of the fall vegetable crops to get established.  (except fava beans and garlic which should be planted in October!)