This is a journal of my vegetable gardens. Skippy was my first dog and he thought the garden was his, even though I did all the work. Now Suzie and Charley follow in his footsteps. We're located near Boston (USDA zone 6A). I have a community plot, a backyard vegetable garden, fruit trees, berry bushes, chickens, and bees. I use sustainable organic methods and do my best to grow all of my family's vegetables myself.

Wednesday, July 25, 2012

late blight

I just got back from spraying my tomato plants. We had a little rain yesterday and I've been spraying with a copper fungicide after every rain to protect against late blight. My plants look really good this year, so I'm hoping for a good harvest before the blight comes in.

The latest info on tomato blight is at this site:

Late blight was spotted early this year, July 3, in some commercial tomato fields near my garden and in other parts of the New England. But it seems that it isn't spreading very rapidly.

A couple weeks ago, I sent out this notice to gardeners in our Community Garden.


Bad news – On July 3, Late Blight was confirmed on tomato plants near us (Middlesex County MA). This is a very aggressive pathogen that can kill an entire field of tomatoes or potatoes within a few days.

As you may remember, we had a terrible year at the Belmont Victory Gardens with Late Blight in 2009. It affected the whole garden and the entire NE region with devastating effects for commercial growers.

We would like to ask you to do the following:
-    Please read some of the links and information on the bulletin board (we will post photos and info soon) to learn about Late Blight and how to identify it.
-    Check your tomato and potato plants carefully for Late Blight and report it immediately to me if you find any (UMASS extension service like to follow locations of outbreaks and fellow gardeners will also like to know). If you find damage that looks like late blight it must be removed from the Gardens and disposed of at home in your trash. Do not compost it! Late Blight spreads very quickly and it is important to do what we can to contain spread of the pathogen.
-    To protect your plants from infection (especially important in shadier and low lying areas):
o    Remove leaves at the bottom of tomato plants to increase airflow
o    Increase airflow around potatoes and tomatoes by trimming nearby plants, removing weeds, removing vines from fences, and keeping the paths mowed
o    Spray tomatoes and potatoes before every rain with a fixed Copper fungicide spray that is organic approved.

I walked through the Belmont gardens today and checked tomatoes and potatoes in many plots. I did not see any Late Blight, but did not have time to check all gardens. Actually, I think the tomatoes and potatoes look really good this year. There is a bit of Septoria leaf spot around as usual, which is a less aggressive fungus that causes small brown spots and yellowing from the edges of the leaves on both tomatoes and potatoes, but not much.

In my garden, I removed the Septoria damaged tomato leaves and disposed of them in my trash at home. I will be spraying with a copper fungicide soon. This is available at Hillside Garden Center as a powder or spray. Geno recommends a spray combination of Rotenone (also organic) and copper that is available at Agway in Waltham.

Some helpful links: (lots of good photos here to learn how to identify Late Blight)

Our Yahoo and Facebook sites and are good places for conversations and advice. Also feel free to email me.

Coordinator, Belmont Victory Community Gardens



Anonymous Anonymous said...

You said, "Spray tomatoes and potatoes before every rain with a fixed Copper fungicide spray that is organic approved."

It should be, "Spray tomatoes and potatoes AFTER every rain with a fixed Copper fungicide spray that is organic approved."

With the off and on rain coming up the next couple days I would resist the urge to spray until at least Saturday or when drier weather is expected.

Happy Gardening!

July 25, 2012 4:37 PM

Blogger kathy said...

It’s interesting that you specify to apply AFTER a rain. The advice I had was from a very good gardener with commercial and home experience. He's convinced that application in the dry weather BEFORE rains is needed to protect against fungal spores that travel during during periods of damp moist weather. He also said reapplication is needed again before the next rain, because the rains wash off the Copper.

The product I was using (the bottle is gone now), Ortho Disease B Gone, label reads “Repeat at 7 to 10 day intervals for as long as needed. Reapply after rain.” I now have Bonide Copper Fungicide and its label says “Tomatoes: Apply at 4-14 day interval throughout the growing season”. There is no mention of reapplication before/after rain.
I checked a few websites for extra information. Some say apply after rain, some say before, some say use a regular application schedule. I think this may be a chicken-and-egg thing, since AFTER one rain is BEFORE the next rain. Arrgg. The UMASS Amherst Vegetable Program recommendations sound good to me. Being local and the same as the Bonide label instructions.

Though the labels do not mention it, my understanding is that the spray needs to dry on the leaves, so it should be a dry, still day when the spray is applied.

Missouri Vegetable Growers Association “Water is necessary for most fungal spores to infect a leaf or stem and for the splash dispersal of many spores. Therefore apply fungicides before a rain if it appears that the fungicide will have a chance to dry before the rain. It is not necessary to apply fungicides again after every rain. Most modern fungicides have a good sticker and will persist through rains pretty well. Some fungicide labels will have specific instructions for applying the product before a rain.”

Michigan State University Extension “The challenge is to apply sprays before rainfall events.”

Cornell University Extension “At this time, most copper fungicides are labeled for use every 5 to 10 days or ‘as needed depending on disease severity’. However, more frequent applications generally are not considered necessary, even following rain, because these products are formulated with adjuvants that help keep them on foliage. It is especially critical where copper is being applied frequently to test soil regularly to ensure this is not resulting in an unacceptable accumulation of copper. Before applying copper more frequently than every 5 or 7 days it is advisable to confirm with the certifier that this is permissible.”

UMASS Amherst Vegetable Program “Maintain fungicides at least at 10 day intervals (shorter if conditions grow more favorable, the field is close to an outbreak, or weekly SV is >4 and rain >1.2 inches.” “Apply late blight specific fungicides in affected fields and nearby fields on a regular basis according to a disease forecast model (Blight Cast) until tomato harvest is complete. Shorten spray interval when disease pressure is high or environmental conditions remain favorable for the late blight pathogen (cool and wet).”

I'd love to hear more advice.

July 27, 2012 4:15 PM


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