Black rot

[Dad1960]

I have a grapevine I planted about 25 years ago. About 8 years ago it devolved black rot. I sprayed! I tried ripping the infected grapes off. But still this terrible disease persist. Do I need to remove the grapevine and start over? Help!

 

[DirtMechanic]

I have a grapevine I planted about 25 years ago. About 8 years ago it devolved black rot. I sprayed! I tried ripping the infected grapes off. But still this terrible disease persist. Do I need to remove the grapevine and start over? Help!

No. But without a defined enemy you are reduced to a shotgun approach. Trichoderma is combined with Bacillus Subtilis and other active agents against many fungi. The streptomycin family gives at least three antibiotics sold as gardening products. Actinovate for example. But please, take some time to understand that these can kill each other as well as your pathogen. Having a plan is important.

 

[Tetters]

That's all a bit too technical for me. I would dig this out and burn it. Then I'd buy a new plant and stick it in a different place and start again.
Welcome to the forums @Dad1960

 

[DirtMechanic]

That's all a bit too technical for me. I would dig this out and burn it. Then I'd buy a new plant and stick it in a different place and start again.
Welcome to the forums @Dad1960

Or that.

 

[Dad1960]

No. But without a defined enemy you are reduced to a shotgun approach. Trichoderma is combined with Bacillus Subtilis and other active agents against many fungi. The streptomycin family gives at least three antibiotics sold as gardening products. Actinovate for example. But please, take some time to understand that these can kill each other as well as your pathogen. Having a plan is important.

Sounds as if this is not a once and done tactic. Should I expect this type of fungi every year?

 

[DirtMechanic]

Sounds as if this is not a once and done tactic. Should I expect this type of fungi every year?

Warning: this post got pretty long.

Some can be tough. There is this fungus, Choanephora cucurbitarium, I have had for years that gets on the squash flowers and proceeds to kill the fruits. Everywhere it says no known cure. Plant elsewhere, clean the debris etc. Most folks just pull the flower and discard it and the summer squash is ok, but it is wicked fast so its almost a daily effort which can be a problem.

There is a fellow here that pronounces cornmeal to attract natural trichoderma because it is a mycoparasite that eats pathogen fungi. Well I just have to overdo everything so I bought some prepared tricho strains that also had 4 Bacillus strains in the powder, one being subtilus (Bs). I inocculated the rain moistened cornmeal and it stopped Choanephora cucurbitarium dead. As in I have not seen it again and it been a really wet year. Because the preparation I bought had multiple strains of Tricho and Bacillus, I cannot say which was most active but you know what? I almost do not care. It worked. I will get curious and chase it more, as at some point my inquiring mind simply wants to know.

Your black rot came from somewhere, not the plant. Probably some host plants around you. Spores are everywhere in the soil now. People will say plant something it won't eat for several or more years. Thats why @Tetters said burn it. Its just impractical in my mind to do either. Soil has such a large surface area for spores to hide in, and dirt burns poorly! Even betadine drenches or similiar techniques work less well in open soil than in pots or on seedlings.

By way of fighting fire with fire though, using spores to fight spores works, and fertilizing with cornmeal is not an expensive nor time consuming effort.

The bacillus create enzymatic environs hostile to growth. They are usually smaller than fungi and can get into the really tight hidey holes. Some of these embed into the surface of the plants with their enzymatic chemical actions. I plan to study whether some are found capable of infection, that is to say becoming biologically systemic, endophytic, because that would be totally cool. All the systemic fungicides I know about, which is not many really, that would kill your black rot cannot be used on edibles.

The streptomycin family is antibiotic and it blows my mind you can treat a garden with such a product. They use it on people too.

For now though, I am tickled with @Chuck and his organic ways and how well that system of thinking has performed against Choanephora cucurbitarium. That, according to the internet, is hard to do.

You may also find some essential oils give good control, if not a cure. Thyme oil is really good, but the problem I have with contact killers is they just do not stay on the surfaces, or they dilute in soil or are just really labor intensive or expensive. Sometimes inappropriate, as when blended with fertilizer but your need to spray means you over fertilize.

Throw some cornmeal out there and give it a couple moist weeks to get started.


Edit:

I went webbing and found this next bit. There is a 2 month wait on harvest for one of them, mancozeb. Plus, they will probably kill off any organic efforts you have made.

-"When to Apply Fungicides for Black Rot Control

When combined with good cultural practices a good fungicide spray program is
extremely important. Early season control (bud break through bloom) is important to keep the disease from getting established on the leaves and the spreading to the fruit.

Fungicide application should begin when new cane are 3 to 5inches long and should be
repeated on a 7 to 10 day interval through 3 to 4 weeks after bloom.

VERY IMPORTANT NOTE: The period from immediate pre bloom through 3 to 4 weeks
after bloom is the MOST CRITICAL PERIOD for controlling fruit infection by black rot. During this period the fruit are formed and are highly susceptible to infection. Around 3-4 weeks after bloom, the fruit become resistant to infection and no further sprays for black rot should be required. In my research vineyards at Wooster, we consistently get near complete black rot control on fruit with three fungicide application
starting at very early bloom and two more applications an a 10 day interval.
If sprays are not made (missed) or an improper rate of fungicide is used (too low),
especially in the critical period for disease control, you cannot expect to get satisfactory disease control.

What to Apply and How Much

Commercial Mancozeb 75% fungicide is used at 2 tablespoons per gallon of water.
Commercial Nova or Rally (myclobutanil) 40% fungicide is used at ½ teaspoon per
gallon of water.
Homeowner product IMMUNOX FUNGICIDE (myclobutanil) is used at 2 fluid ounces
per gallon of water. Grapes are included on the label with the use recommendations.
Homeowner product BONIDE MANCOZEB 37% Flowable fungicide is used at 5 tbsp per gallon water.

 

[Tetters]

This is a little picture of me trying to look clever . I did try!

Well, I'm with @Chuck on the organic path, because it works. It might take a bit of time and patience, but it's so worth it.