Friday, August 16, 2019

A list of short PHI materials + reminder on downy mildew

I heard from many that their fruits are ~2 weeks ahead of "average" season, and some early cultivars are already harvested in the southern VA. I should have posted this earlier, but it probably is still applicable to many of us, so, here is a list of fungicides with PHI (Pre-Harvest Interval) equal or shorter than 7 days.  (the list is the same as in 2018, I did not see any additional material with PHI >= 7 days. If I missed any, please let me know.) I cannot cover every single fungicide out there, but I tried to cover common ones. Winemaking considerations can influence fungicide uses close to the harvest too. Make sure to communicate with your winemaker(s) if they have a preference on the use of fungicides, especially copper, sulfur, and captan (I listed several copper materials because they have different PHI or REI.)

For fungicides to be used on cultivars that have more than a month to go, please refer to my previous post.

Please make sure to rotate mode of action. For instance, Botrytis pathogen is well known for quickly developing fungicide resistance, and this pathogen can be resistant to multiple fungicides. I prefer to see a mode of action to be used twice or less per season, especially when we deal with Botrytis (with an exception of fungicides with FRAC code starting with "M"). In addition to proper leaf removal and chemical approach, wound management is very important to reduce the risk of Botrytis. Managing the source of wounds such as insects (esp. grape berry moth), or birds, or powdery mildew at early in the season, can positively impact Botrytis management. Also, I should note that sour rot pathogens also go after wounds.

At Winchester, the night time relative humidity has been very high, above 95%, for four nights in a row. In addition, we have been observing the rapid development of thunderstorms, pretty much every day in the past few days. These conditions favor downy mildew development because downy mildew pathogen prefers to produce spores under dark, humid conditions. Then spores will be spread via rain.



At this point, you do not need to worry about downy mildew infection on clusters; however, they can still infect leaves. Often time, you will initially see infection on the top of the canopy because younger leaves are more susceptible than older ones. Losing the top leaves and laterals are not a big deal; however, once the infection gets severe, it can defoliate many leaves rather quickly (as in the picture below). If you start to lose older leaves, it can affect the maturing process. Since many of us have been having a relatively dry season, you probably do not need to spray expensive materials, but it is probably not a bad idea to use captan or copper or phos acid in your next spray. (but once again, please consult with your winemaker about the last spray of captan or copper that they would like to see. Often time, we say it is better to avoid captan or copper or sulfur within a month of harvest.)


Good luck with the rest of the season!


Wednesday, July 17, 2019

Berry touch/bunch closure disease management reminders

Our Chardonnay clusters are getting larger and berries are starting to touch each other. It feels a bit early, but here are grape disease management reminders at berry touch/cluster closure stage.



Botrytis gray mold: The best management practice is canopy management. Botrytis pathogen likes high humidity, thus, the poorly managed canopy that traps humidity will help them to thrive. This pathogen also needs wounds to develop spores, thus, grape berry moth and other insects plus birds need to be managed too.

There is a number of Botrytis materials such as Rovral and Meteor (FRAC 2), Elevate (FRAC 17), Vanguard and Scala (FRAC 9), Luna Experience (FRAC 7 plus 3), Kenja (FRAC 7), Miravis Prime (FRAC 7 plus 12), Switch (FRAC 9 plus 12), etc. Botrytis pathogen is well known for its ability to develop fungicide resistance, so, please rotate FRAC codes!!

QoI fungicides (FRAC 11) are no longer the effective material for us due to the development of QoI-resistant Botrytis isolates throughout Virginia. Pristine (FRAC 11 plus 7) has been compromised as well. The next timing of application for Botrytis management is at veraison.

Ripe rot and bitter rot: At this point of the season, captan (M4) and QoI (Strobirulin, FRAC 11) fungicides are good options. In addition, we found that Switch (9 plus 12), copper (M1), tebuconazole (3), Aprovia (7), and Ph-D (19) are somewhat effective. However, none of these materials consistently provided satisfactory suppression of ripe rot when we applied these materials by itself in a series of field studies. Thus, please mix two FRAC codes, especially if you have ripe rot issues in the past. The timing of applications will be the same as Botrytis.

Sour rot: A tank mix of the insecticide zeta-cypermethrin (Mustang Maxx) and the antimicrobial hydrogen dioxide (OxiDate 2.0) before a symptom appears (before veraison) to suppress the fruit fly population is the key. In NY, there are reports of Mustang Maxx-resistant fruit flies, thus, please do not overuse it. Two applications should be sufficient. If you don't have OxiDate, Switch also lists sour rot (suppression only), and other broadspectrum fungicides such as captan and copper, probably have some efficacy too.

Speaking of sour rot, please take a short survey below. We try to gain more information from growers so that we can come up with research priorities. It will be closed in 5 days, so, please participate today. It is not only for Virginia. Thus, if you grow grapes in other states or country, we need your opinion too!

Sour rot survey (will open a new window)

Monday, July 8, 2019

Sour rot survey

My colleagues and I are seeking information on sour rot so that we can develop research priorities (and hopefully obtain grants). Many of us suffer from sour rot (remember the last season?), and we need to get our heads together. If you could fill in this short survey, we really appreciate. It should not take more than a few minutes to complete. It is not just for Virginia, so, please feel free to complete the survey if you grow grapes outside of Virginia.

Sour rot survey (will open a new window)

Thank you!!

Downy mildew reminder



Of course, once I mentioned the lack of rainfall, we (i.e., northern VA) were hit by a series of rain. To make things more complicated, we had at least three consecutive nights of warm and humid (RH > 90%) condition prior to the rains. Humid nights encourage downy mildew pathogen to produce spores, and rains will splash spores to healthy tissues. Thus, the risk of downy mildew during recent rain events was very high. (Note: Central VA also had two humid nights in 7/5-7/6 at the Charlottesville airport, but the chance of rain is not high until this Thursday.)

There are a number of materials can be used for protection: captan (FRAC = M4), mancozeb, ziram (FRAC = M3), Revus, Forum (FRAC = 40), Zampro (FRAC = 40 plus 45), Ranman (FRAC = 21)). Mancozeb products have the 66-day PHI, but ziram's PHI is 21 days. Another good option is a copper (FRAC = M1) material, which is more economical than other materials. Copper has good efficacy against downy mildew, and tends to do well under frequent rain condition. There are several newer copper materials that cause fewer phytotoxicity issues even on relatively copper sensitive cultivars (e.g., Cueva, Champ, etc). If you have already having downy mildew issue, use copper, ziram, or captan as the backbone of your spray program.

Both a phosphite material (FRAC = P07) such as Prophyt and Phostrol, as well as Ridomil products (FRAC = 4 plus M3 (MZ) or + M1(Copper)) have a kickback activity against downy mildew (i.e., it can stop the ongoing infection process). Ridomil MZ contains mancozeb, so, we cannot use it at this time of the season due to its 66-day PHI. Ridomil Gold Copper has a 42-day PHI, so, you may able to use it, depending on the cultivar. Please note that Ridomil is known to have resistance issues, thus, let's limit the use of Ridomil to twice a season at the most. We also have seen multiple Revus-resistant isolates in VA.

So what to do, if you are not sure your previous fungicide application was sufficient (e.g., applied more than 10-14 days ago and/or received more than 2 inches of rain)? 

Options are:
A) a phosphite or Ridomil Gold Copper plus captan or ziram
or
B) a phosphite or Ridomil Gold Copper plus Revus/Forum or Zampro or Ranman. 

These mixes provide both protective and kick-back activities. 

Friday, July 5, 2019

A quick reminder about powdery mildew

It depends on where you are, but in northern VA, we are having relatively "dry" weather this summer. We have some rain events here and there, but overall, the air is humid, but not wet. Such a condition promote powdery mildew development, so, I just want to provide a reminder on powdery mildew management.

(Powdery mildew symptom on a cluster: the picture was taken this morning)

Powdery mildew pathogen thrives under shaded condition  (i.e., overcrowded canopy). Thus, canopy management is a very important aspect of powdery mildew management.

Chemical management options: Sulfur (FRAC = M2) is an economical option. Copper (FRAC M1) works too, but compared with sulfur, copper seems to be slightly less effective. Other options are: DMI fungicides (e.g., Rally, Elite, Mettle, Rhyme, etc, FRAC 3), Quintec (FRAC 13), Vivando (FRAC 50), Luna Experience (FRAC 7 plus 3), Topguard EQ (FRAC 11 plus 3), Rhyme, Kenja, and Aprovia (FRAC 7), Torino (FRAC U6), etc. Please make sure to rotate FRAC groups. Try to limit the use of a particular FRAC group to twice a season with an exception of FRAC group starts from M.

Fungicide resistance issues: QoI (FRAC 11, e.g., Abound, Flint, etc.) = widespread in VA. I would not count on the QoI material for powdery mildew management. Quintec (FRAC 13) = limited occurrences, but there is a recorded case in VA. There is evidence of DMI-resistant powdery mildew isolates in VA, thus, please do not overuse or rely heavily on DMI products.

If you have an outbreak that cannot stop, please use sulfur or copper (i.e., do not spray the material with FRAC group starts with a number). Also, Kaligreen, Armicarb, and other potassium bicarbonate (FRAC M) are effective; however these materials tend to be expensive. Stylet oil (FRAC M) can be used on on-going powdery mildew too; however, please note that you cannot mix (or use within 14 days) oil and sulfur (the same is true with oil and captan).

Wednesday, June 19, 2019

Quick reminder: 66-day PHI for mancozeb products

Just a quick reminder about the 66-day PHI for mancozeb products. If you are thinking about harvest at the end of August or early September, we are getting very close to the limit.

You can switch to captan or copper, but these two cannot control black rot, thus, you may need to add a DMI or QoI fungicide for black rot. At least in our area, it has been dry (relatively speaking) so, depends on where you are, you may or may not need to be concerned about black rot. I see black rot on leaves sporadically in my vineyards, but not in the level I need to be greatly concerned.

Thursday, June 13, 2019

Handout from yesterday's VVA meeting

It was very nice to see you all at the meeting. Here's the content of my handout.

Seasonal grape disease updates
For VVA Summer Technical Meeting at Stone Tower Winery
12 June 2019
Mizuho Nita
nita24@vt.edu
Grapepathology.blogspot.com

The critical period for cluster infection: Grape clusters are sensitive to infection by powdery mildew, downy mildew, and black rot from the time of bloom to 4-6 weeks after bloom. The length of this critical time depends on the cultivar, 3-4 weeks for American grapes (V. labrusca),  5-6 weeks for French grapes (V. vinifera), and somewhere between the two for hybrids. Please make sure that you have good coverage during the critical period. In a typical year, once we pass the Fourth of July weekend with a clean canopy, we can relax a bit. We are a week or two ahead of “normal” year, so, you may able to relax sooner this year.

Downy mildew: Rainfall is not as intensive as the last year (knock on the woods!), but there are enough to drive downy mildew (plus we all probably have more than the typical amount of inoculum due to the last year). There are a number of materials can be used for protection: captan (FRAC = M4), mancozeb, ziram (FRAC = M3), Revus, Forum (FRAC = 40), Zampro (FRAC = 40 plus 45), Ranman (FRAC = 21)). Both a phosphite material (FRAC = P07) such as Prophyt and Phostrol, as well as Ridomil products (FRAC = 4 plus M3 (MZ) or + M1(Copper)) have a kickback activity against downy mildew (i.e., it can stop the ongoing infection process). Please note that Ridomil is known to have resistance issues. Luckily, we have not seen it in VA, so, let’s keep it that way. Please limit the use of Ridomil to twice a season at most. We also have seen Revus-resistant isolates in VA too.

Another good option is a copper (FRAC = M1) material, which is more economical than other materials, has good efficacy against downy mildew, and tends to do better under frequent rain condition. There are several newer copper materials that cause fewer phytotoxicity issues even on relatively copper sensitive cultivars (e.g., Cueva, Champ, etc). If you have already having downy mildew issue, use copper, mancozeb, and captan as the backbone of your spray program.

Also, downy mildew tends to come back as the temperature goes down at the end of the summer (i.e., the last half of August). Lower temperature causes the relative humidity at night to go up, and it may end up with dews, which is an ideal case for downy mildew pathogen to produce spores and infect new leaves. Thus, make sure to use a material for downy mildew to protect your vines later in the summer.

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.

Powdery mildew: Powdery mildew pathogen thrives on shaded leaves (i.e., overcrowded canopy). We have a fair number of options for powdery mildew management. Sulfur (FRAC = M2) is an economical option, and there is a range of products with different modes of action (= FRAC group). Examples are: DMI fungicides (e.g., Rally, Elite, Mettle, Rhyme, etc, FRAC 3), Quintec (FRAC 13), Vivando (FRAC 50), Luna Experience (FRAC 7 plus 3), Topguard EQ (FRAC 11 plus 3), Rhyme, Kenja, and Aprovia (FRAC 7), Torino (FRAC U6), etc. Please make sure to rotate FRAC groups. Try to limit the use of a particular FRAC group to twice a season with an exception of FRAC group starts from M. Also, please note that you can not mix (or use within 14 days) oil and sulfur (the same is true with oil and captan).

Unfortunately, we have widespread of QoI (FRAC 11, e.g., Abound, Flint, etc.) fungicide resistance powdery mildew isolates in VA, so, I would not count on the QoI material for powdery mildew management. Also, there is evidence of DMI-resistant powdery mildew isolates in VA, thus, please do not overuse or rely heavily on DMI products.

Botrytis gray mold: Development of Botrytis depends on what type of varieties you grow, as well as your canopy management strategies. White-fruited varieties with tight cluster architecture tend to be more prone to Botrytis. I.e., a red-fruited variety with loose clusters have fewer issues with Botrytis, especially if the canopy is well maintained. Since Botrytis pathogen likes high humidity, poorly managed canopy that traps humidity will help them to thrive. Bloom time is important for Botrytis management because this fungus can infect flower and flower debris, and come back later when berries are maturing. There is a number of Botrytis materials such as Rovral and Meteor (FRAC 2), Elevate (FRAC 17), Vanguard and Scala (FRAC 9), Luna Experience (FRAC 7 plus 3), Kenja (FRAC 7), Miravis Prime (FRAC 7 plus 12), Switch (FRAC 9 plus 12), etc.

As with powdery mildew, QoI fungicides (FRAC 11) are no longer the effective material for us due to the development of QoI-resistant Botrytis isolates throughout VA. Pristine (FRAC 11 plus 7) has been compromised as well. Botrytis pathogen is known to develop resistance to fungicides very quickly, so, please make sure to rotate FRAC groups! The next timings of application for Botrytis management are: at bunch closure (to make sure the materials gets to the inside of clusters), and veraison.

Also, research from Penn State showed that when Botrytis infect flowers, symptom development requires wounds on the berry skin. One of the causes of wounds on grape berry skin is powdery mildew which damages skin cells to cause splitting. Grape berry moth also causes wounds on the berry skin tends to show up in the vineyards around this time of the year. Unlike diseases, you can wait until you see webbing on the clusters to make a decision on spraying against grape berry moth.

Ripe rot and bitter rot: Unfortunately, we do not have a lot of options against them. Mancozeb (M3), ziram (M3), captan (M4), and QoI (Strobirulin, FRAC 11) fungicides are currently recommended. In addition, we found that Switch (9 plus 12), copper (M1), tebuconazole (3), Aprovia (7), and Ph-D (19) are somewhat effective. However, none of these materials consistently provided satisfactory suppression of ripe rot when we applied these materials by itself in a series of field studies. Moreover, we documented that resistance to the QoI fungicide is common among ripe rot pathogens in VA. 

Thus, if you have a severe case of ripe rot, what I recommend is the use of mancozeb as long as the 66-day PHI allows, plus add a QoI or Switch or Aprovia or tebuconazole at bloom. Then use either copper or captan (0-day PHI for both) or zirum (21-day PHI) and mix with a QoI (14-day PHI) or tebuconazole (14-day PHI) or Switch (7-day PHI)  for the latter part of the season. (Aprovia has a 21-day PHI.) We have resistance issue with the QoI fungicides, so, do not apply by itself. I am still recommending the QoI as a mixing partner since we are dealing with several different fungal species, and some are still sensitive to the QoI. The timing of applications will be the same as Botrytis, so, include ripe rot material when you apply for Botrytis.

Sour rot: A study from Cornell University reported up to 80% reduction of sour rot when they use a tank mix of the insecticide zeta-cypermethrin (Mustang Maxx) and the antimicrobial hydrogen dioxide (OxiDate 2.0) weekly starting prior to the appearance of sour rot symptoms (~ veraison). You probably do not need to spray weekly, but if your cultivar is prone to sour rot, the fruit fly management before symptom development will be the key. As with fungicides, please rotate the mode of action of insecticide. Switch also lists sour rot (suppression only), and other broadspectrum fungicides such as captan, probably have some efficacy too.

Resources

If you have not, please check my blog (grapepathology.blogspot.com) or Twitter (@grapepathology) or Facebook page (Grape pathology at Virginia Tech), if you prefer them.

GrapeIPM.org: If you have not, please sign up for our new pest management support system. It will help you keep track of pesticide inventory, planning, etc. It is free!

NEWA: Virginia is part of an Agricultural weather network called NEWA (http://newa.cornell.edu/). We have about a dozen weather stations scattered around the state. You can check daily disease and insect pest risks. Please check it out. If you want to join NEWA (i.e., purchase a weather station), please let me know. I am the state coordinator for VA.

Virus kit: VT’s plant disease clinic and I am offering a free virus (grapevine leafroll virus-2 and 3, and Red blotch viruses). Please see me so that I can give you a sampling kit.

Good luck with the rest of the season!!!

Saturday, May 18, 2019

At bloom Botrytis and ripe rot management tips

This is the second part of "at bloom" fungal disease management tips. Please refer to yesterday's post as well.


The spray timings for Botrytis is at bloom, bunch closure, and veraison.  The pathogen has a wide host range and seems to be active throughout the season, but blooming time is considered as a critical timing because the pathogen can infect flowers without showing symptoms.

Please keep in your mind that Botrytis is very well known for its capacity to overcome fungicides.  Thus, a rotation of mode of action groups is a very important aspect of Botrytis management. Mode of action for a particular fungicide can be found as a FRAC code, which you should be able to locate on the label.  Here’s a short list of materials for Botrytis and their FRAC code in parenthesis: Elevate (17), Scala (9), Vangard (9), Switch (9+12), Inspire Super (9+3), Luna Experience (7+3)*, Kenja (7)*, Meteor/Rovral (2), Endura* (7), Pristine* (7+11), Miravis Prime (7+12)*.

The material with an asterisk has a high concern for resistance development. Please note that group 7 is considered a high-risk material. Dr. Baudoin's lab has identified strong evidence of resistance against Endura and Pristine. For the other group 7 materials, such as Kenja, Luna, and Miravis, the way they work is the same as the other group 7 materials; however, chemical companies engineered these materials to be delivered into the pathogen differently, so that these newer materials are different in terms of how the fungicide resistance develops. Thus, it may take a while for our Botrytis isolates to find a way to overcome these materials. However, cases of fungicide resistance for these newer materials are reported in other crops or in lab studies. Thus, I would be very careful about the usage. [Also please note that Aprovia is also a group 7 material, but it does not have a label for Botrytis.]

When you are not sure how to rotate fungicides, please rotate the FRAC code because two different fungicides with two different chemical names may have the same FRAC code as you see on the list above. Also, tank-mixing with other material, such as captan, which has weak to fair activity against Botrytis, will help to lower the risk of fungicide resistance development.  If you think one of the fungicides you are using is not providing sufficient control, please contact Dr. Baudoin or me.

Another management tip for Botrytis is about wounding on berries. Although Botrytis is capable of causing disease by penetrating grape’s fruit skin tissues, it prefers going after wounds. Also, at bloom infection by Botrytis tends to develop into disease when fruit skin is damaged, but when the skin is intact, the risk of disease development will be much lower, according to the study done by a Penn State group. Thus, management of the source of wounds such as insects (esp. grape berry moth), or birds, or powdery mildew at early in the season, can help to manage Botrytis. Moreover, sour rot pathogens also really like going after wounds; so, the same wound management would be the key for the sour rot management as well.

Both ripe rot and bitter rot are considered as warm season diseases, and in fact, people in the south tend to suffer more from these diseases; however, we can find ripe rot in Northern VA year after year.  In addition, I have heard from growers from PA and MD that they are having issues with ripe rot as well. 


Unfortunately, ripe rot, in particular, has been misdiagnosed more than other rots. It shows up as if the berries are sunburned, thus you will see round dark brown lesions on the top portion of an infected berry. The difference from sunburn is that with ripe rot, there would be the tiny dots you will see within the lesion, which are fruiting bodies of the pathogen. As time progresses, the lesion expand into the whole berry, and infected fruits become shriveled raisin-like fruits (please see the picture above). With a severe infection, you may see the majority of berries on a cluster shriveled down. Unlike sunburn, it does change the taste of the fruit and wine. Unfortunately, the change is in the negative direction, and a study showed that a consumer panel could detect only 3% contamination in the mast.

Both ripe rot and bitter rot seem to be able to infect berries from time of flowering to the harvest.  Thus, protection is important, especially if you have experienced issues with these diseases in the past. Mancozeb, ziram (FRAC=M3), captan (FRAC=M4), and QoI (Strobirulin, FRAC=11) fungicides are currently recommended. But due to the 66-day PHI of mancozeb, you may not have enough days remained to spray mancozeb at this time of the season. Based on our lab and field tests, mancozeb, captan, copper (FRAC=M1), tebuconazole (FRAC=3), azoxystrobin (FRAC=11), and Swith (FRAC=9+12) provided some level of efficacy against ripe rot pathogens; however, none of the products provided sufficient degree of control by itself. Also, some of the isolates causing ripe rot are not sensitive to some of those materials. Thus, when it comes to ripe rot managenent, please think of not only a rotaion of modes of action, but also a tank mix of at least two modes of action. The timing of the application will be similar to that of Botrytis: bloom, bunch closure, and veraison.

Friday, May 17, 2019

At bloom disease management tips

Many people in northern VA are about to see blooms in a few weeks, and I am sure the rest of the regions are about to see bloom very soon.  Bloom is a start of the critical time for cluster infections by downy mildew, powdery mildew, and black rot. Bloom time is also the critical period to prevent Botrytis, ripe rot, and bitter rot, because pathogens of these diseases can infect flower parts and develop symptoms later.

What I recommend often is the use of protectant materials to protect tissues for 4-6 weeks for V. vinifera varieties, and 3-4 weeks for V. labrusca varieties, which should translate into 3-4 sprays for V. vinifera, and 2-3 sprays for V. labrusca.  If you have hybrids, they are somewhere in between, so, 4-5 weeks to be protected.  As usual, please make sure to rotate mode of action (= FRAC) groups.

Since we have experienced rain every weekend (and looks like another rainy weekend coming up), we need to be on top of downy mildew and black rot management. In our vineyards, I noticed that there were several leaves with small lesions of downy mildew.

Protective materials for downy mildew are: Mancozeb (FRAC=M3) [Gavel has mancozeb + zoxamid (FRAC=22)], Captan (FRAC=M4), Fixed copper (FRAC=M1), Revus or Forum (FRAC=40), or Zampro (FRAC = 40+45), or Ranman (FRAC=21)).  (Please note that there is an increasing case of Revus resistant downy mildew isolates in VA. Plus, resistance to Ranman is known among downy mildew pathogens of other crops. Make sure to spray before the rain and rotate!)

Protective materials for black rot are: Mancozeb, QoI (FRAC=11, Aboud, Flint, Pristine, Intuity, etc.), and DMI (FRAC=3, tebuconazole, Elite, Rally, etc). Captan and copper won't work against black rot.

We do have materials with kick-back activities against downy (Ridomil products (FRAC=4), phosphite (FRAC=P07, Prophyt, Phostrol, etc.) and black rot (myclobutanil (FRAC=3, DMI), etc.),. However, they can be effective between infection and establishment of the pathogen (i.e., the day of rain and 3-4 days after). We do not have any eradicant that can kill already established pathogens. Infection on flowers and young fruits can happen very fast. Unless we have a very dry season (which is a rather rare event), this is the time where you have to be proactive. Thus, please protect your vines. Do not wait until you see diseases!

Also please note that recent warm and humid nighttime conditions are favoring spore production of downy mildew pathogen. For example, since 5/1, there were six days with RH near 90% and the temperature was in the 60’s. It is not as threating as in 2018, where at this time of the season, we already had several days of RH > 90% and temperature > 70F, but we still need to be on alert.

In addition to downy and black rot, we need to think of Botrytis, ripe rot, and powdery mildew. (I will cover Botrytis in more details in the next post (probably tomorrow), since this post is getting very long already.)

Here are three examples I thought of considering current conditions.  (Note: I am considering a phosphite (e.g., Prophyt) and Ridomil products, but not listed in the plan.  I will add a phosphite or Ridomil products for downy mildew whenever we have many rain events. Please limit the use of Ridomil products to twice a season for resistance management)

Plan A (my "standard" program)

  • At bloom: mancozeb + sulfur (FRAC=M2) + myclobutanil or another DMI + Vangard (FRAC=9, or other Botrytis material)
  • First cover: mancozeb + sulfur + Quintec (FRAC=13) (or other PM material, such as Vivando (FRAC=50) or Torino (FRAC=U6))
  • Second cover: mancozeb + sulfur + myclobutanil or another DMI
  • Third cover: captan (FRAC=M4) + sulfur + Quintec (or other PM material, such as Vivando or Torino) (Note: if I do not see any evidence of powdery mildew, I may omit Quintec from this spray)


Plan B (if your major concern is downy mildew: note: I will add a phosphite or Ridomil product based on rain condition)

  • At bloom: mancozeb + sulfur + Revus Top (FRAC=40+3) + Vangard (or another Botrytis material) (note: Revus Top contains a DMI, which should provide extra kick against powdery mildew. Also, you can use Gavel for mancozeb to have additional downy mildew material.)
  • First cover: mancozeb + sulfur + Quintec (or other PM material, such as Vivando or Torino) (I may add Ranman to add more protection against downy here)
  • Second cover: mancozeb + sulfur + Revus Top
  • Third cover: captan + sulfur + Quintec (or other PM material, such as Vivando or Torino) (Note: if I do not see any evidence of powdery mildew, I may omit Quintec from this spray)


Plan C (if your major concern is Botrytis and powdery mildew)

  • At bloom: mancozeb + sulfur + Luna Experience (FRAC=7+3, Luna Experience contains a DMI) (Using FRAC=7 will give you an opportunity to use other Botrytis material (say, FRAC=9, 17, etc), if bloom last longer than expected or use these FRAC at the other spray timings (bunch closure and veraison))
  • First cover: mancozeb + sulfur + Quintec (or other PM material, such as Vivando or Torino)
  • Second cover: mancozeb + sulfur + myclobutanil or another DMI
  • Third cover: captan + sulfur + Quintec (or other PM material, such as Vivando or Torino) (Note: if I do not see any evidence of powdery mildew, I may omit Quintec from this spray)


The spray interval depends on the weather conditions; so, I cannot give you a specific number.  However, in general, I would aim for shorter intervals for the bloom, first, and second cover (7 to 12 days), but I may relax a bit for the third and subsequent sprays (10 to 14 days), especially if weather conditions do not favor disease development (i.e., dry).

Please note that I was saving my DMI and Quintec (or Vivando, or any other new powdery material) usages for the critical period, thus this is the only time I spray these materials. If you have already used these materials, please rotate with another FRAC group.

I would like to use a mancozeb product around bloom and critical because it has activities against multiple pathogens including pathogens for black rot and ripe rot. Captan and copper are not as effective as mancozeb when it comes to black rot management. The third cover may become too close to the 66-day PHI, so, you need to be careful with the usage of a mancozeb product.

Of course, the examples above are just examples, and there are many other options.  For example, there are many materials available for both downy and powdery mildew management in recent years.  Please refer to our PMG for more details. A link to 2019 PMG is located on the right-hand menu of this blog (or at the bottom, if you access here with your smartphone or tablet)

Sunday, May 5, 2019

Early season fungicide application reminders

It has been another rainy weekend (1.5 inches so far and still counting), and looks like next weekend will be wet again... Hopefully, this year won't as wet as the 2018 season...

Hopefully, you can provide good protection before the rain, but even if you did, rain more than 1-2 inches can wash the material away from the canopy. Dr. Annemiek Schilder at Michigan State University has a great article about rain and wash off of fungicide. Her work suggests that although only a 0.04 inch of rain can wash a certain percentage of a material from the leaf, it takes about 1-2 inches to actually having a negative effect on the efficacy since the rate you apply is typically much higher than the threshold for the efficacy of the material.
Downy mildew symptoms on the upper leaf surface

When we have the next chance of application, what material(s) should we apply? I think many of us are about 2-4 weeks away from the bloom, so, the major concern is downy mildew. If you think you have missed the window (e.g., there were more than 2 inches of rain from the last application of a fungicide against downy mildew, or it has been more than 10 days from the previous application and you were not able to cover before 1-2 inches of rain), it is probably a good idea to have a phosphite material (FRAC = P07) such as Prophyt, Phostrol, etc. It has a kickback activity against downy mildew (i.e., it can stop the ongoing infection process). While you are at it, it probably a good idea to mix with a protective material (e.g., captan (FRAC = M4), or mancozeb, ziram (FRAC = M3), or Revus, Forum (FRAC = 40), or Zampro (FRAC = 40+45), or Ranman (FRAC = 21)).  (Please note that there is an increasing case of Revus resistant downy mildew isolates in VA. Make sure to spray before the rain!)

If your vines are within two weeks of bloom, it is probably better to include mancozeb plus a QoI (FRAC = 11, e.g. Abound, Flint, etc) or a DMI (FRAC = 3, e.g., Rally, Mettle, etc) for black rot. There is a difference between the QoI and DMI in regards to their kickback activity against black rot. In between them, the DMI is known to have a better (i.e., reach out longer) kickback activity than the QoI. So if you are in doubt about black rot, a DMI maybe a better option.

Ridomil products (FRAC = 4 + M3 (MZ) or + M1(Copper)) have excellent kick-back activity against downy mildew. Typically, I recommend the use of phosphite as noted above because Ridomil products have known fungicide resistance issue. Thus, Ridomil products could be a good option if you are concerned about a lack of coverage, and you want to have a very good material to stop the on-going infection. Please make sure not to spray too many times. Although you could apply up to four times according to the label, my recommendation is to limit the use of it to twice a season. We have too many fungicide resistance issues in our state, and the overuse (and misuse) of a product is the most likely cause. Also, although Ridomil MZ has mancozeb, the concentration of mancozeb will be less than our typical recommendation (3 lb/A). You may want to adjust it by adding mancozeb (to meet 3 lb/A) or other a material(s) to cover black rot.

The other potential scenario is that you have applied materials just before the recent rain events, so, you might not be too concerned about the missing window, but you want to have an insurance against the upcoming rain event(s). In such a case, a copper (FRAC = M1) material might be a good fit. It is more economical than other materials, has good efficacy against downy mildew, and it tends to do better under frequent rain condition. There are several newer copper materials that cause fewer phytotoxicity issues even on relatively copper sensitive cultivars (e.g., Cueva, Champ, etc). Another option is captan (FRAC = M4). Both copper and captan material are not effective against black rot, so, if your vines are near bloom, make sure to have mancozeb plus a QoI or a DMI for black rot.

One of the reasons why I mention about copper and captan is because of the use limitation of mancozeb. In addition to the well-known 66-day PHI, there is a limitation in the amount of mancozeb can be used for each year, which is about 19 lb per acre per year. (Please refer to the label for the specific number for your product.)

Lastly, just because we have many rains, it won't stop powdery mildew. Make sure to have a powdery mildew material (sulfur, FRAC = M2, or others) in your tank-mix.

Friday, April 19, 2019

Phomopsis disease management reminder


(Phomopsis leaf spot (plus a lesion of black rot), please note the shoot behind the leaf is showing some necrotic lesions which are also caused by the same pathogen)

One of the diseases you need to consider this time of the year is Phomopsis cane and leaf spot.  It causes minor leaf spots, which is more obvious to our eyes, but the more important damage is caused by necrotic lesions on shoots and rachis. It also causes berry rot; however, it is not common with wine grapes because of our spray programs. Materials for black rot and downy mildew are often effective against Phomopsis. Thus, the fungicide coverage for these diseases is also working as management of Phomopsis, especially later in the spring and early summer. Some cultivars, such as Viognier and Seyval Blanc, are more susceptible to Phomopsis than the others.

Phomopsis typically takes a while to establish in the vineyard. It may take 5-6 years for Phomopsis to become noticeable if you start a new vineyard. However, once established in a vineyard, it is difficult to get rid of this disease. The fungus survives in canes and trunks that were infected in previous years, and it can also cause damages on cordons and trunks. During the spring, it will produce spores on the surface of infected tissues, and these spores are splashed by rain onto new shoots or leaves. Luckily, the pathogen (Phomopsis viticola) produces spores mainly during the springtime. Thus, unlike the other diseases we face, there is only one major infection period throughout the season. Because of that, the spread of Phomopsis does not happen rapidly as other grapevine fungal diseases, such as downy mildew.

Phomopsis spores can cause infection under the relatively cooler environment (the upper 40s). Thus, springtime rain events are ideal for Phomopsis to produce spores and cause infection. Unfortunately, we do not have curative fungicides for Phomopsis management; therefore, it is important to protect young tissues when they come out from the older canes and trunks. Since shoots will grow rapidly, you may need to spray 1-2 times against Phomopsis, depending on how much rains we receive.


(Phomopsis can cause small necrotic lesions on shoots)

If rain events are coming into the picture after bud break, mancozeb (FRAC = M3, Penncozeb, Dithane, Manzate, etc.), Ziram (FRAC = M3), and captan (FRAC = M4) are effective protective materials against Phomopsis. In a typical year, one or two applications from 1-2 inch shoot growth will be sufficient, because your downy mildew or black rot applications, which happens in the late spring, will cover Phomopsis. QoI (FRAC = 11), such as Abound and Pristine, as well as SDHI (FRAC = 7), such as Luna Experience and Aprovia, work too. However, you probably don't want to use them this early in the season because you will need these materials for the latter part of the season to control other diseases.  Once again, protection is the only mean of chemical management because no materials are effective after the infection.

The other disease that you may need to consider around this time of the year is Anthracnose, which is more common with a certain hybrid species. Typical symptoms are black necrotic lesions on leaves,  shoots, and fruits, and often time, the black lesion has an ash-colored center, as if you burnt the leaf or shoot tissue with a cigarette. The management strategies will be similar to that of Phomopsis, and Topsin-M (FRAC = 1) is also known to be effective. For more information on Anthracnose, please refer to this link (Michigan State's Extension Website on grape Anthracnose management).

(Anthracnose lesions on a leaf)


Monday, April 15, 2019

2019 season has began

It's approximately 10% bud break on our 10 years old Chardonnay and about 25% on 5 years old Chardonnay. Hopefully, we won't get frosted!!

Saturday, April 6, 2019

Presentation slides from this week's grape disease management workshops

Thank you for attending grape disease management workshops at Loudoun County Extension Office. I really enjoyed the discussions we had. I also appreciate the effort Ms. Beth Sastre puts together for organizing the meeting and translating for 4 hours!!

Click here to download the pdf of the slides I used in the workshop. I fixed some errors, but if you have any questions, please do not hesitate to contact me.

Good luck with the 2019 season!! I will update this blog as the season goes along.

Wednesday, April 3, 2019

Looking for things to do on Friday afternoon? Please join our grape disease management workshop!

Our next grape disease management workshops are at Loudon County Extension Office. Please RSVP with Ms. Beth Sastre (flores69 (at mark) vt.edu).

Por favor Ășnete a nuestro taller de manejo de la enfermedad de la uva! RSVP con la Sra. Beth Sastre (flores69 (at mark) vt.edu).

Thursday, April 04, 2019

Vineyard IPM Program (1 - 4 pm)
Disease management in the Vineyard (in Spanish/en Espanol)
Loudoun County Cooperative Extension office
750 Miller Drive, SE
Suite F-3
Leesburg, VA 20175


Friday, April 05, 2019

Vineyard IPM Program (1-4 pm)
Disease Management in the Vineyard (in English)
Loudoun County Cooperative Extension office
750 Miller Drive, SE
Suite F-3
Leesburg, VA 20175

Monday, April 1, 2019

Presentation slides from PSU Grape disease and insect pest management workshop

Here are my presentation slides from PSU grape disease and insect pest management workshop. Once again, I am looking for crown gall samples from neighboring states.  Please contact me when you have some (dying) vines to spare. I will come and get it. I am planning to visit PA vineyards this summer.

     - I learned some people want to have a file with a larger side size: here is a "1 slides/page" version.



Tuesday, March 19, 2019

Presentation slides from UGA Seasonal vineyard and pest management conference

Here are slides from my presentations at UGA Seasonal Vineyard and Pest Management Conference.

1) Ripe rot research updates

2) Introduction to trunk disease diagnostic aid app and GrapeIPM.org.


FYI: Our next grape disease management meetings are at Loudon County Extension Office. Please RSVP with Ms. Beth Sastre (flores69 (at mark) vt.edu).

Thursday, April 04, 2019

Vineyard IPM Program (1 - 4 pm)
Disease management in the Vineyard (Spanish)
Loudoun County Cooperative Extension office
750 Miller Drive, SE
Suite F-3
Leesburg, VA 20175

Friday, April 05, 2019

Vineyard IPM Program (1-4 pm)
Disease Management in the Vineyard (English)
Loudoun County Cooperative Extension office
750 Miller Drive, SE
Suite F-3
Leesburg, VA 20175

Thursday, March 14, 2019

2019 version of a fungicide application template

Here's a 2019 version of fungicide application template. Please read the footnote for downloading onto your computer or copy to your Google Drive to use it.

This template is designed to be used as a guide. You need to create your own plan based on your vineyard(s)!!

If you have time tomorrow afternoon, please join us for our first grapeIPM.org training session, which will be held at Horton Vineyards from 1 PM. It would be a great excuse to visit Horton to taste their award-winning wines!

Tuesday, March 12, 2019

GrapeIPM.org training on March 15th at Horton Vineyards

We will hold a training session for GrapeIPM.org on March 15th (this Friday) at Horton Vineyards (6399 Spotswood Trail, Gordonsville, VA 22942). The meeting starts at 1 PM and closes at 3 PM.

  • GrapeIPM.org is our new online database and risk assessment system which allows you to manage your pesticide records and planning. We introduced it to select growers in 2018, and we are extending the invitation to more growers this year.
  • You can assign multiple vineyards or blocks (whichever you wish to call). 
  • The system has a pre-made list of commonly used fungicides (we are working on insecticide now), thus, what you need to do is pick the one you have in your inventory, and enter in the system's calendar. 
    • If you happen to use not-so-common pesticides, we are working on an interface that allows you to enter your own.
  • You can enter the area to be applied and the size of your sprayer, and the system will give you an estimate of how much you need to mix in your sprayer too. 
  • Once you create your plan, you can export it to a calendar (Google or iCal) to share with your co-workers. 
  • When you complete the spray, you check off, and at the end of the season, you can generate a table that meets the EPA's expectation for your record keeping.
  • There is a function to enter your current inventory. If you use this function, you can check what needs to be purchased when you finish your planning for the year.
  • It also helps tracking your other activities and record (e.g., pruning, weeding, growth stage, disease outbreak, etc). 
  • Also, if you happen to have a vineyard close to one of our weather stations, you can connect to it to obtain recent weather information as well.
  • My research associate, Mr. Robert Burgholzer, who is also a vineyard owner, and I will host the meeting to introduce the system and walk you through the functions. 
  • This system is web-based and mobile-ready (i.e., no app to be installed). Make sure to bring your laptop, or tablet, or smartphone so that you can have hands-on experience!

Sunday, March 10, 2019

Dormant application of fungicide(s)

At this time of the season, I am often asked about an application of fungicide(s) to dormant vines. I totally understand that you want to do something before things get busy.

A dormant application of lime sulfur (10% in our study, or 1% of a newer product called Sulforix in a study done by Dr. Annemiek Schilder at Michigan State Univ.) should be effective against Phomopsis and/or Anthracnose. We also tested cupper, but it was not effective. However, the efficacy of the application is not strong enough to allow you to skip any preventative fungicide applications to be sprayed soon after bud break. (i.e., even with a dormant application, you still need to protect your shoots when they emerge.) With the corrosiveness of lime sulfur, I feel that it is not worse the money and time, plus, it will be another application of a fungicide, which we try to reduce. It is much effective to spray mancozeb or captan soon after bud break. Thus, I would recommend a dormant application of lime sulfur only if you have a serious issue of Phomopsis and/or anthracnose and you need an extra kick to your regular preventative application after bud break.

The dormant application is less likely very effective against downy or powdery because both are called polycyclic diseases with a rapid secondary cycle. Even if you knock down the initial inoculum, they can produce next round of spores rapidly especially under favorable conditions. Also, the winter survival structures of these pathogens are very tough, so, I don't think fungicide application is the best approach.

Tuesday, March 5, 2019

EPA is reviewing captan

Captan, which we use extensively to manage downy mildew, Phomopsis, ripe rot, and other grape diseases, is currently under review by the EPA. In order to keep captan as one of our tools to control grape diseases, please respond to the EPA's registration review page to post your comment (will open the EPA page). With increasing cases of fungicide resistance with newer products in our region, it is very important for the majority of commercial grape growers located east of the Rockies to keep older multi-site materials such as captan to be used as a backbone of the spray program. 
Also, please forward the message to other producers and stakeholders who should respond to the need for this fungicide in our industry. 

Wednesday, February 27, 2019

Upcoming VCE Viticulture meetings

Here is a list of upcoming meetings. Please note that there are two meetings on March 15th. 
GrapeIPM.org introduction and training session will be held at Horton Vineyards from 1:00 PM.


Friday, March 01, 2019

Dormant Pruning Workshop
Hamlet Vineyards, Bassett VA
Free, registration required: 
https://www.eventbrite.com/e/dormant-pruning-workshop-for-vineyard-growers-tickets-55660249304


Thursday, March 7, 2019

Dormant Pruning Workshop and Competition (1pm - 4pm)
English and Spanish speakers welcome
Sunset Hills Vineyard
Free, registration required:
https://goo.gl/forms/sNI1ULt5s3H41y7W2


Thursday, March 7, 2019

Ag Labor Forum
Longwood University


Friday, March 15, 2019

New Grower Workshop
Abingdon Vineyard 
https://www.eventbrite.com/e/new-and-advanced-grower-workshop-tickets-57447751772


Friday, March 15, 2019

A new tool for vineyard management, grapeIPM.org: Introduction and Training
Location: Horton vineyards
Time: 1-4 PM


19-21 March 2019

Eastern Winery Exposition
Syracuse NY
https://easternwineryexposition.com/

Thursday, April 04, 2019

Vineyard IPM Program (1 - 4 pm)
Disease management in the Vineyard (Spanish)
Loudoun County Cooperative Extension office
750 Miller Drive, SE
Suite F-3
Leesburg, VA 20175

Friday, April 05, 2019

Vineyard IPM Program (1-4 pm)
Disease Management in the Vineyard (English)
Loudoun County Cooperative Extension office
750 Miller Drive, SE
Suite F-3
Leesburg, VA 20175

Sunday, February 24, 2019

VVA slides

It was very nice to see you all at the VVA meeting!
Here are the slides from my presentations (in a pdf format).

1) Grape disease management workshop

2) Ripe rot research updates

I will post a list of upcoming VCE meetings in a few days.