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Vegetable Gardening

potato blight on greenhouse tomatoes

11 years ago

It has been a cursed growing season for me as most of my orchard was frozen out for the first time in over 20 years of harvesting fruit here- now this.

Blight on tomatoes has never been a problem for me until the plants are out of the green house, which I always delay as long as possible and plant them in waves to get a full season of harvest.

Last year I decided to use chlorathalinil in a reduced spray schedule spraying maybe 3 times at 2 week intervals after taking plants out of the green house. This seemed to increase productivity considerably.

However, I've never needed anything for plants in the green house, but this year there are yellow areas on leaves of all my plants that look like they must be blight and not normal die-back. I've been growing tomatoes for 40 years, 25 in the east coast, and I've learned the distinctive look of blight damage.

I don't know if there's any advice anyone can give- all my plants appear infected. I guess the only thing to do is go out and buy plants and start over.

I'm wondering if anyone else in this region is suffering similar problems with their greenhouse tomatoes or if I've been picked out for special punishment (gallows humor).

I'll have to figure out how to disinfect the green house, but that's an issue for later on.

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Comments (2)

digdirt2
11 years ago
Well this is more a discussion for the Growing Tomatoes forum than here and you will find much more information there. But as a fellow greenhouse grower I feel for you so I will hit some of the high points.

First Late Blight (aka "potato blight"), is cause by the airborne fungus p. infestans and is quite rare (but not impossible) indoors. Further it is characterized by dark black (rather than yellow) areas on the leaves AND the stems and trunk. It is always almost immediately fatal to the plant with total plant failure within a few days. Per Cornell Univ. there have been no verified reports of Late Blight in the northeast so far this year.

Early Blight (a. solani) is characterized by yellow leaf damage in a bulls-eye pattern and is not fatal to the plants although it does affect production so replacing the plants would be recommended if early enough in the season. And EB has been VERY active in many parts of the country already this year.

Then of course there is Alternaria and several other tomato diseases which many also mistakenly lump under the label "blight".

But all except Late Blight will respond to the use of Daconil (chlorathalinil) so I'd sure give it a try. I'd strip off all the affected foliage, spray the healthy foliage well, and transplant a few test subjects deeply and monitor them for new growth before pitching all the plants.

As for disinfecting the GH, summer heat if you turn off the vent/fan system and let the temps rise will take care of much of it and then hose down the entire place with a 1:10 diluted chlorine bleach solution.

Good luck.

Dave
alan haigh
Original Author
11 years ago
Sorry, it was a mid-diagnosis on my part. Went to photos and it is another fungus altogether caused by humidity in the greenhouse and temps that haven't been high enough to activate my fan over the last couple of weeks. Never saw it as bad as this year so symptoms look much different.

Hopefully plants will be fine as I get them out doors, meanwhile I've reduced the temp that will activate the fan.
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