Is this black rot

[harleydmn]

I think it is but need suggestions on what to do now. Should I trim everything back , keep on spraying? I was using champ every. 14 days. Need to learn so this don't happen next year


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[djrockinsteve]

Those grapes yes have black rot. Black rot comes from inside the grape from the vine. Completely destroys entire crop in a week. Once it appears it's too late. Spreads by wind and rain to uninflected vines.

You need a good spray program of Pristine, Captan and Manzate.

I lost all of my grapes 3 years in a row until I learned what I was dealing with and how to treat it. Doing good now.

 

[grapeman]

Those first two pictures are textbook examples of black rot. The infection on the leaves is often the source and spreads to the grape blooms and leads to the grapes like you show. Be sure to remove all affected clusters and destroy to the source of pathogens. The most critical time to spray is pre-bloom, bloom and early post bloom. Champs is not all that effective and 14 days is stretching the spray interval especially during wet weather.

 

[harleydmn]

Well, I guess I have learned the hard way. Thanks djrockinsteve for sending me the spray program, now to wait till next year for my first harvest.

 

[peaches9324]

Those first two pictures are textbook examples of black rot. The infection on the leaves is often the source and spreads to the grape blooms and leads to the grapes like you show. Be sure to remove all affected clusters and destroy to the source of pathogens. The most critical time to spray is pre-bloom, bloom and early post bloom. Champs is not all that effective and 14 days is stretching the spray interval especially during wet weather.

what do you suggest he uses to avoid future outbreaks?

 

[grapeman]

Mancozeb (such as Manzate) and Pencozeb products are very effective a preventing Black rot. Rally and Elite have some post infection effectiveness, but is limited to about 72 hours after infection.

The following is right out of the NY/ Penn State IPM booklet available for use online or buying a copy. This is from 2010 when I posted it at Winepress.us so this exact thing is no longer online. You can look for the current copy of the NY/PA guide online.

BLACK ROT is one of the most serious diseases of grapes in the eastern United States. Although relatively easy to manage with the aid of conventional fungicides, it has the potential to cause substantial crop loss in wet <BR clear=all>years. Fruit rot is the most damaging phase of the disease, but all green tissues of the vine are susceptible to infection.



Infected leaves develop relatively small, brown circular lesions surrounded by distinct dark margins; black, pimple-like fruiting bodies ("pycnidia") are scattered within these spot-like lesions. Black, elongated lesions on petioles (leaf stems) may cause affected leaves to wilt and drop. Large, black, elliptical lesions on infected shoots may contribute to breakage by wind. The disease is most common and damaging on berries. These are chocolate brown when first infected, but soon become dark brown with numerous black, pimple-like pycnidia on the surface. They eventually shrivel into hard, black raisin-like mummies, most of which remain firmly attached to the berry stem.




The black rot fungus overwinters primarily in mummified fruit on the vineyard floor or in mummies retained within the vine. It can also overwinter within cane lesions when these develop. Rain triggers the release of infective spores from all sources, and infection occurs if susceptible tissues remain wet for a sufficient length of time, which depends on temperature (Table 3.1.1). Spores within cane lesions are available for infection starting at bud break; however, the majority of overwintering spores in most vineyards (those within mummified fruit on the ground) first become available about 2–3 weeks after bud break, reach peak levels about 1–2 weeks before bloom, and are usually depleted within one to several weeks after the start of bloom, depending on the season. However, in years with dry spring weather when only a few rains occur, the fungus does not discharge all of its spores as early as usual, and significant spore discharge may extend several weeks beyond bloom if this is when rains finally develop.



CAUTION: Most mummified fruit remain firmly attached to the berry stems and are not removed by machine harvesting. When these are not dropped to the ground during dormant pruning operations, they will produce large numbers of spores within the canopy throughout the period of berry development the following year. Research has shown that this prolonged period of high spore production, combined with the closeness of the spores to newly-developing berries, significantly increases the pressure for berry rot. Therefore, removal of mummies from the canopy is a critical component of black rot management programs.



Pycnidia develop within the lesions caused by current season infections and begin releasing a new generation of spores about 2 weeks after infection first occurs. These spores then cause new infections under favorable rainy conditions. Such secondary rounds of new spore release and re-infection are responsible for disease spread, and are the cause of most economic loss when it occurs. Fruit are highly susceptible to infection for the first 2–3 weeks after cap fall. They become progressively less susceptible as they continue to develop, finally becoming highly resistant about 5–8 weeks after bloom, depending on the variety and year. In general, "Concord" fruit appear to become resistant about 1–2 weeks earlier than those of V. vinifera varieties. Thus, the most critical time to control berry infections is during the first few weeks after the start of bloom.



Removal of mummified clusters from the canopy during pruning significantly reduces disease pressure for the coming season; burying mummies on the ground before or soon after budbreak, by cultivation or covering them with mulch, also can contribute to a reduction of inoculum if disease was severe the previous season. All spray products currently approved for "organic" production are weak against black rot, although copper has moderate efficacy if applied very regularly. Therefore, growers of organic grapes should pay strict attention to the above sanitation procedures, because they are the most important defenses against this disease, which can be the "Achilles heel" of organic grape production in eastern viticulture. Cultural practices that open the canopy also are beneficial because they promote drying and improve spray coverage. See Table 3.1.2 for varietal susceptibility to this disease.



Spray Timing:Fungicide applications once were recommended to begin at about 3- to 5-inch shoot growth and continue at regular intervals of 10–14 days until veraison. However, most disease control is provided by the immediate prebloom and first postbloom fungicide sprays, and virtually complete control has been provided in the vast majority of vineyards when these sprays have been followed by a second postbloom application. This second post-bloom application is potentially critical if black rot symptoms are visible on either leaves or fruit at that time, and should be considered prudent in most vineyards if this portion of the season is wet. If severe black rot developed during the previous year, or if the vineyard has a history of consistent black rot development, an additional spray two weeks before bloom may be beneficial, particularly under wet conditions. Because damaging levels of black rot usually result from spread within the cluster, sprays should continue through the end of July if more than a trace level of berry rot is present and weather conditions are suitable for infection (see Table 3.1.1).



Rally (^Nova) and ΔElite provide excellent control of black rot, and are labeled for up to 72 hours of postinfection activity. Recent research indicates that their effective period of postinfection activity is one to several days longer than this, although delaying postinfection applications beyond 72 hr should be employed on an emergency basis, not as a deliberate strategy. The strobilurin fungicides (Abound, Flint, Pristine, Sovran) are excellent protectants but provide only very limited postinfection activity. Mancozeb and ziram are good protectants but are more subject to wash-off than the strobilurins, so must be reapplied more frequently during high-rainfall conditions. Other fungicides should not be relied upon for black rot management. Copper fungicides are the most effective organically-approved materials, but must be applied frequently (e.g., 1-wk intervals) under high disease pressure conditions.

 

[djrockinsteve]

This is my spray program.

Start your spray program when you have 10 inch shoots. Probably May 10th but adjust based upon growth.

May 10
Manzate-3# per acre

May 25th
Pristine-10 oz. per acre

June 5th
Captan-2# per acre

June 15th
Captan-2# per acre

June 25th
Manzate-3# per acre

July 20th
Pristine-10 oz per acre

These amounts are based upon 100 vines per acre. Adjust for your quantity. Mix with enough water to cover all plants.

I spray underneath first then spray top. Any left over spray I spray that evening to use it all.

 

[tatd69]

That is good information for a newbie.


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[peaches9324]

Thank you grapeman for taking the time to post that I appreciate the good info you always put forward your an asset to this forum!

 

[drumlinridgewinery]

Just seen this thanks for the info. and the really nice spray program. Need to do something different next year.

 

[berrycrush]

When you use multiple chemicals, do you use designated sprayer for each chemical? or you use the same container? When two kinds of fungicide are used at the same time, again, do you use different sprayers for each or mix them up and just use one container?

 

[grapeman]

Most fungicides will mix alright. Check the label and you can also do a test mix of small amounts in a jar. If they get along well it will remain a liquid , if not they will likely clump.