Black Rot Help Needed

[djrockinsteve]

Been battling black rot for years now and can’t get it under control. Wind up losing half or more of my grapes.

My current spray program-
Western Pennsylvania

May 15, Captan (dry) .4 oz/ gal.
May 29, Daconcil (liq) 2 tbs./ gal.
June 6, Captan .5 oz per gal.
June 15, Daconcil 2 tbs. / gal.

Black Rot appears.

June 17, Captan 1.0 ounce/ gal.

I spray top, bottom, in/out/up/down and spray leaves and clusters.

We have rain virtually everyday and humidity.

I even trim back vines to keep it open for air to circulate under.

Vines are Brianna, two wire.

Any help is appreciated.

 

[srcorndog]

Black rot: Rain also makes black rot pathogen very active, Mancozeb works well, but if you see leaf symptoms already, adding a QoI (FRAC = 11, e.g. Abound, Flint, etc) or a DMI (FRAC = 3, e.g., Rally, Mettle, etc) or a SDHI (FRAC = 7, e.g., Aprovia, Luna, etc) for black rot is probably a good idea. The DMI has a better kick-back action (i.e., can reach-back a few days) than the QoI, and we do not have a data on SDHI in terms of the kick-back action. Please note that both captan and copper do not have good efficacy against black rot.

 

[Stressbaby]

My non-expert opinion is that you need to start earlier with a different regimen. I've been following this schedule with good results: http://plantpathology.ca.uky.edu/files/ppfs-fr-s-20.pdf
I use sample 1 (for hybrids). Missouri, zone 6a, so probably not more than 1/2 or 1 zone from you. It's also been VERY wet here.

 

[Masbustelo]

If I'm reading this study correctly, you need to be doing leaf pulling, using Sevin, and Serenade max in your regimen. https://www.michiganwines.com/docs/Research/08schilder2.pdf

 

[Masbustelo]

Here is a second study. https://www.canr.msu.edu/news/dont_let_bunch_rots_ruin_your_grapes

 

[Cynewulf]

I’m in Northern Virginia and also deal with heavy disease pressure, including black rot. I’m in my third year and feeling like I’m finally getting it under control. Others here will have a lot more expertise than me, but I do know that Captan is ineffective against black rot and it doesn’t look like Daconil is either. I found that out the hard way the past two years. Mancozeb has been very effective for me so far this year and isn’t too expensive on Amazon. I’m about to switch over to Captan (downy mildew), sulfur (powdery mildew), and Immunox (black rot). This blog from a Virginia Tech grape pathologist has been very helpful and the following link has a useful template he made. http://grapepathology.blogspot.com/2019/03/2019-version-of-fungicide-application.html?m=1

It looks like Penn State also has a grape pathologist that you might try contacting for advice even more specific to your local area: https://agsci.psu.edu/research/ag-experiment-station/erie/grapes.

I too think you probably also will need a more aggressive spray schedule.

 

[wxtrendsguy]

I have a commercial vineyard in eastern PA and am a licensed pesticide applicator...now repeat after me.....CAPTAN DOES NOT WORK TO CONTROL BLACK ROT! If you are raising grapes in most of the eastern USA and fighting Black Rot you should always be using Manzate. Start at 2 lbs/ac when shoot growth is 1-3" and repeat every 7-10 days depending on precipitation patterns. Once you reach June increase to 4 lbs/ac. Keep track of how much you spray as you cannot go over 24 lbs/ac for the year. Now you also need to add something to control powdery mildew as long as temperature remain below 85-90F. Hotter than that and PM is usually not an issue. You can use Quintec which is very effective but since you are growing Brianna do not use sulfur as they can be sensitive. In early July you will make your last Manzate spray as you will be getting close to the 66 day PHI, replace Manzate with Rally, Immunox, Elite and or several others, by late July you are pretty much done with the need to worry about Black Rot. Also once done with Manzate you can not forget about treating for Downy Mildew, so now introduce Captan, phosphorous acid and others to treat DM. Carry that out for the rest of the season and your grapes should be free of most fungal disease.

 

[BigH]

Daconil/chlorothalonil is not labeled for use on grapes.

According to the midwest fruit spray guide, Captan offers "Fair" control for black rot. You need to spray something that offers "Good" or "Excellent" control. Agree with others that Manzate/mancozeb should be the cornerstone of your spray program. It offers "Excellent" control for black rot. Rally, Abound, Sovran, and Ziram do as well. I spray all of those in a rotation. I have made my last Manzate spray due to its hefty PHI.

 

[Dennis Griffith]

Immunox is another consideration that is effective on black rot and is labeled for grapes. It also has a shorter PHI (14 days), so you can use it closer to harvest. Remember that mancozeb has a 66 day PHI. With the wet season we are having, you may need to try several products, but keep an eye on the PHI for each. Captan does have a short PHI, but would be more effective of other fungi (as noted earlier). I also include Serenade (1 day PHI) as it will help build resistance to fungus.

 

[wxtrendsguy]

Remember Vinifera grapes become immune to black rot infection 5-6 weeks after bloom and hybrids are usually 4-5 weeks. Thus if bloom is in mid June (now) you can pretty much stop treating for black rot by late July.

 

[user 36973]

Also once done with Manzate you can not forget about treating for Downy Mildew, so now introduce Captan, phosphorous acid and others to treat DM.

Totally agree. I've repeatedly been burned by late season DM on my cayuga grapes. They are bullet-proof during the spring but very susceptible in the late summer.

I've also started tank mixing phosphorous acid with Captan for to help with the pH lowering which makes Captan more effective as well as the corrective effect of any growing DM.