Friday, September 7, 2012

Home stretch!

I think many of you are either harvesting or getting ready for it.  We harvested our Chardonnay and Merlot yesterday. (Of course most of them are damaged due to our fungicide trial, but there are a few left...)

It seems like we are expecting some rain over this weekend.  The question is what to do in terms of the last minute disease management.  If you have clean vineyard without major rot issues, and you only have only a few days to go, you probably not need to take action. 

If you have clean vineyard, but you still have more than 10 days to go, it may depends on the condition of the berries.  If you notice any wounding on berries (by birds, hornets, sun damage, etc), then you may want to consider captan before this rain because many of late season rots take advantage of these wounds.  If you have nice clean berries, then, you may able to wait and see.

If you have some rot issues, again captan is a nice tool.  It is effective against variety of pathogens, and it has a very short PHI (0-day) (but remember that REI is 48-72 hours, depends on the formulation).

If you have some downy mildew issues, it is probably a good idea to mix a phosphonate (phosphorous acid, such as Prophyt, Agri-Fos, etc, 0-day PHI) with captan.  Sine we have experienced a frequent rain events and humid nights that were very conducive for downy mildew development in the past few weeks, please make sure to scout your vineyards for downy mildewIt tends to appear on younger leaves on the top of the canopy first.  You may or may not see yellow "oil spot" on the top surface of the leaves, so, make sure to flip leaves over to look for downy mass of spores.  I know you are probably focused on your clusters now, but leaves are also important!  Downy mildew cannot get to berries at this time of the season, but heavy infection on leaves can defoliate leaves.  Your vines will need these leaves to mature berries and also to store carbohydrate for winter survival. 

The vine on the right hand side is defoliated due to lack of protection against downy mildew.  You don't want this to happen to your vines!



Monday, September 3, 2012

Today's disease risks

After yesterday's post, Winchester area received measurable rain.  ;)  The estimated wetness duration was 14 hours with 72F.  It was long and warm enough for Botrytis and Downy mildew.  

It looks like we are expecting a few more rain events in next few days due to the effect of a tropical depression Issac.  We will see...

Sunday, September 2, 2012

disease risks from today's rain

We are having a very humid day today in Winchester area.  There have been several rains passed since early morning, but only a few of them were enough to be recorded at weather station (it need to be more than 0.25 cm/0.01 inches).  Plus, even though the RH has been high, it was not higher than 70% in most of the day.  Thus, if anything, there were a low risk for downy mildew infection event.

I imagine many of you are preparing for harvesting now.  I am hoping not seeing too many rains!

Monday, August 27, 2012

Disease risks from yesterday/today

There were two wetness hours recorded yesterday through today.  One happened around 6AM with 6 hours of estimated wetness with 66F, and the other happened around 5PM with 22 hours of estimated wetness with 69F.  Thus, we had infection events for downy mildew and Botrytis.

Once again, our recent conditions (warm and humid nights) are favoring downy mildew pathogens to produce spores.  Please keep eye on younger leaves (upper part of the canopy) to catch their early development.  Severe downy mildew infection can cause defoliation, and you do not want to that to happen at this time of the season.

Also, these extensive humid conditions also call for Botrytis and other late season rots.  Canopy management to promote air circulation and bird management can be a very useful tool to deal with late season rots.  That also reminds me to mention about Spotted wing Drosophila (SWD).  We do have some isolated cases of SWD in VA vineyards this year.  Please keep eye on this newly introduced fruit fly.  If you have a concern on SWD, please contact Dr. Doug Pfeiffer (dgpfeiff@vt.edu).

Tuesday, August 21, 2012

Risk events for today.

We received a showed yesterday afternoon, and it resulted in about 7.5 hours of estimated wetness duration with an average temperature of 65.5F around Winchester area.  It was an infection event for downy mildew and Botrytis, and it was a potential infection event for black rot and Phomopsis (Note: these two diseases are of relatively minor importance at this point of the season).  Once again, I see the risk of downy mildew remains high.  Please scout your vineyards (especially for younger leaves) often to catch early development of downy mildew.

  (note: the East of us received a considerable rain over the weekend, but we did not. i.e., other Northern VA area might have one more risk events.)  

Saturday, August 18, 2012

Disease risks from yesterday

Yesterday's shower brought about 7.5 hours of estimated wetness duration with an average temperature of 71F around Winchester area.  It was an infection event for downy mildew and Botrytis, and it was a potential infection event for black rot and Phomopsis (although these two diseases are of relatively minor importance at this point of the season).  Once again, I see the risk of downy mildew remains high.  Please scout your vineyards (especially for younger leaves) often to catch early development of downy mildew.

Around this time of the season, I am often asked about the potential impact of a fungicide application on wine quality.  There were several studies where authors detected chemical residues on the must.  It is often practiced to avoid application of sulfur and copper 3-4 weeks prior to the harvest.  It would be relatively easy to do when we have a dry condition, but sometimes (like in 2011), we may just need to do whatever we can to secure yield.  For example, a good air circulation (= canopy management) around clusters is very important.  For late season rots (sour rot, ripe rot, Botrytis and other general rots), captan is often used, and Switch is labeled for both Botrytis and sour rot.

If your concern is downy mildew or powdery mildew, you can also spray only on foliage (i.e., avoid spraying fruiting zone by closing nozzles), since your berries have developed resistant.
  

Wednesday, August 15, 2012

Downy mildew reminder

Since last week, we are having several nights where relative humidity is very high (>90%) (e.g., 8/9-10, 8/13-15).  This condition favors downy mildew fungus to produce spores.  Unlike others, this pathogen can cause disease after a short rain (90 min at optimum conditions).  Thus, some of short showers we are having here and there this week may be long enough as an infection event for downy mildew.  For example, yesterday's short shower event was probably long enough for downy mildew to spread.  Also, please keep in mind that these showers are often geographically nonuniform and you might have had a longer wetness event.

At this point, a phosphonate (aka phosphorous acid, such as Prophyt) is a good option to control downy mildew.  Some people prefer to include captan to add more forward protection.  The target of this late season application is to keep foliage healthy in order to help berries to mature, and also to accumulate carbohydrates for winter survival.  Your berries are not susceptible to downy mildew at this point.

Thursday, August 9, 2012

Disease risks Aug 5-6

There was an estimated leaf wetness event occurred Aug 5-6 with 13 hours with an average temperature at 73° and 0.41 in. rain.  It was an event for downy mildew and Botrytis (+ Phomopsis and black rot).

(Sorry for the delayed posting.  I am at a conference.)

Wednesday, August 1, 2012

Disease risks from yesterday and hail damages

Yesterday's storm brought more than 2-inches of rain, and resulted in approximately 12.5 hours of wetness with an average temperature of 69F.  It was an infection event for downy mildew and Botrytis (and Phomopsis and black rot, but they are less important at this time of the season, unless you have on-going Phomopsis issue).

The other thing yesterday's storm brought was hails.  We saw a minor, but obvious damages from the hail.  Often time you will see random holes on leaves, clacks on berries, and sometimes, necrotic scars on canes.  Please see the pictures below.


The question is what will be the consequence of these wounds on berries.  It depends on a few factors.  If we have a nice hot day like today, these damaged berries more likely to be dried out; however, if we have another prolonged rain event, it can introduce Botrytis and other late season rots.  It may also depends on how much sugar is available on these berries.  The more sugar they contain, the higher the risk of rot pathogens to come in since some of them like high sugar environment.  If you have a risk of rots, you can consider applying captan and/or one of Botrytis materials.


Veraison and rain...


Our Merlot and Chardonnay hit veraison over the weekend.  We placed bird netting and thinking about to spray for Botrytis, and here we received a strong storm followed with a long wetness period.  I will update once this wetness period finishes.

Monday, July 23, 2012

Disease risks from this weekend

A rainy weekend brought our area two estimated wetness periods (19h with 73F, and 20h with 64F), plus additional 30h+ hours of high humid condition (RH>90%) (note: some of you might have ended up with 50+ hours of wetness period.  We only had about 3 hours where RH dropped below 90% on Saturday).  The wetness periods were infection events for Phomopsis, black rot, downy mildew, and Botrytis.  (note 2: your vines should be over with a critical period for berry infection for black rot and downy mildew.)

In addition, the extensive humid condition probably favored downy mildew spore production.  As you know, severe downy mildew infection can cause defoliation.  If you are debating whether you should apply a downy mildew material or not, you can scout for downy mildew symptoms.  At this time of the year, it tends to show up on younger (= upper part of the canopy) leaves because these are more susceptible than older leaves.

At this point, people often use Phosphonates (Phosphorous acid, Prophyt, etc) material which can provide both protective and kick-back activities.  It is often applied with captan to increase the protective activity.  The alternative is Ridomil with Copper, but please note that it has 42-day PHI.  If you are looking for a protective material for downy mildew, you can use Revus (Revus or Revus Top, 14-day PHI), Ziram (21-day PHI), Captan (0-day PHI), Ranman (30-day PHI), Pristine (14-day PHI) etc.  (Note 3: Pristine may or may not provide you a good control against downy mildew since QoI resistance is commonly found in VA).

Thursday, July 19, 2012

Effect of yesterday's storm

Thunderstorms went through yesterday in Winchester area; however, air was dry (RH<80% even during the rain), and the sun came up soon after that, thus, leaves were probably dry soon after the rain.  It was probably not a disease risk event.  We are expecting to see more rain this afternoon.

Tuesday, July 17, 2012

Read and follow the label

Someone in MN lost his 40,000-square-feet lawn by a misapplication of herbicide.  I think this is a good reminder for us all to read and follow the label.

Disease event from yesterday (Update)

The second rain event on Sunday night ended up with about 10.5 hours of estimated wetness with an average of 70 F.  It was infection event for Phomopsis, black rot, downy mildew, and Botrytis.

Also, we had another warm and humid (RH >95%) night.  As I mentioned the other day, these conditions are favored by downy mildew pathogen to produce spores.

Monday, July 16, 2012

Disease risks from this weekend

It looks like we have thunderstorms every weekend!

There were a few line of rains went through Winchester area, and two risk events were observed.  One was on Saturday morning with 8.5 hours of wetness with 68F, and the other one is on-going from last night with 5+ hours with 70F.  The first one is a risk event for black rot, Phomopsis, downy mildew, and Botrytis. 

I will update for the second event, but from the look of outside, the humidity may drop very soon.

These rains (or high humidity) during night time promote downy mildew to produce its spores.

Wednesday, July 11, 2012

Disease risks from this weekend

Rain fall in 8-9 July resulted in 15 hours of estimated wetness event with an average temperature of 72F.  It was infection event for Phomopsis, black rot, Botrytis, and downy mildew.

Due to a series of rains we received over last two weeks or so (including a few nasty storms), I started to see downy mildew development in our experimental vineyards.  Please keep eye on them.  We are most likely done with the critical time for berry infection, but it can still cause disease on leaves.

Thursday, July 5, 2012

Disease risks from this weekend

There were two storms on Monday and Wednesday went through Winchester area, but these were too short to count as disease events.

Only potential exception is downy mildew, which can cause disease in a short time (90 min or so); however since air dried out very quickly after the storm, these probably did not count as downy mildew disease risk events.

Monday, July 2, 2012

Another storm...

Winchester area received precipitations from another storm that started shortly after midnight.  It was approximately 8 hours of wetness with an average temperature of 68F.  It was infection events for Phomopsis, black rot, and downy mildew, and a borderline case for Botrytis infection.

It looks like we have a chance of a thunderstorm (30-45%) almost every day this week.  Hopefully next ones are not as bad as previous ones.

Sunday, July 1, 2012

Disease risks from this weekend

Winchester area received a severe storm in lat Friday night, and that brought us an estimated 11 hours of wetness with an average of 68F.  It was risk events for Phomopsis, downy mildew, black rot, and Botrytis.

Nothing major, but we had some damages on our vineyards due to the storm.  I hope your vines were OK.

According to the radar, it looks like another storm will pass through tonight.  We will see...

Monday, June 25, 2012

2012 version of home garden fungicide list

Finally, I had a time to update a list of fungicides for home garden grape production.  This updated list contains name of fungicide products that you can purchase from home garden centers or online stores.  (By the way, I am surprised that you can purchase fungicides from Amazon...)  It also contains a table of efficacy against common grape diseases.

I have noticed that there are so many variations of the products, so, I listed only a few.  The other thing I noticed was that in many cases, the companies pre-mix other pesticides, such as an insecticide that you may not need.  Please make sure to read the label carefully.  Your label should have grape listed as a target host, if not, there may a reason behind it.

Note: The list has been updated once again on 6/26/12

Saturday's disease risk event

Oops, this one slipped out from my mind over the weekend!  I calculated the value, satisfied, and forgot to upload!

In anyway, from Friday night, we had a wetness event of 15 hours with average of 65F.  It was an infection event for downy mildew, Phomopsis, black rot, and Botrytis.

Most of us are probably close to the end of the critical period for cluster protection, and probably planning for (or even finished) the third cover after bloom, which is typically the last critical period spray. Hopefully, you are having a clean vineyard up until this point so that you can relax a bit after next spray!

Tuesday, June 19, 2012

Recent disease risk events

Most of VA started a week with a rainy Monday.  At Winchester, the first estimated wetness period started 5 AM Monday morning, lasted until 3 PM (10 hours) with an average temperature of 64F.  The second one started from 6 PM and lasted until today around noon (18 hours) with an average temperature of 64F.  Both were risk events for Phomopsis, black rot, downy mildew, and Botrytis.

Some of you may remember that I was concerning about lack of diseases in our experimental vineyards at the VVA summer technical meeting ;).  Sure enough, I start to noticing a rapid development of powdery mildew on some of border vines, and downy mildew is on its way too!  It reminds me how quickly these pathogens can spread.

Some of early varieties are at bunch closure.  If you have a variety that is susceptible to Botrytis, this would be a good spray timing to deliver a material into the cluster.

Wednesday, June 13, 2012

Downy mildew gallery

Here's some of downy mildew symptoms (on Vidal).
1) On upper leaf
2) Underside close-up
3) On young berries

 4) Up-close and personal

You can find more pictures of downy mildew (and other diseases) from the link listed on the left-hand side of this blog.  Click on a disease name of your interest, and it will bring up past posts about the disease.

Disease risks 11-13 June

Winchester area received quite a bit of precipitation (1.4 inches) from a series of rain event starting from the 11th of June.  We had two wetness periods 14 hours with 69F and 12 hours with 66F.  These were risk events for downy mildew, Phomopsis, black rot, and Botrytis.

We have been rating diseases in our treatment plots for three weeks now.  So far what I see most is downy mildew and a little bit of powdery mildew and black rot.  It makes sense to me to see many downy mildew infections due to recent wetting events and relatively humid nights we had in latter part of May.  I have heard from some growers that they have issues with downy on leaves and clusters.

If you have an issue with downy mildew or concerned about the risk from recent rain event, both Ridomil and Phosphonate (Phosphorous acid) products have a kick-back activity (= able to stop on-going, but not established, infection).  Since resistance against Ridomil products is known to develop among downy mildew pathogens, so, if you have an on-going major downy mildew issue, it is probably better to use a phosphonate + captan (or mancozeb, if the PHI allows you) combination.

Saturday, June 2, 2012

Disease risks from yesterday

I guess it is typical of Winchester area.  I was monitoring radar regularly for the entire afternoon, watching lines of thunderstorms moving toward northeast over many part of VA; however, our area only received rain from 7 PM to 9 PM or so (~0.6 inches).  The estimated leaf wetness period was 6 hours (RH did not stay high due to the wind) with an average temperature of 62F.  It was a light infection event for Phomopsis, and also an infection event for downy mildew.

Thursday, May 31, 2012

Disease risks from yesterday's rain

Thunderstorm and rain event started around 5PM on 29th resulted in about 10 hours of estimated leaf wetness event with an average temperature of 68F.  It was an infection event for Phomopsis, black rot, downy mildew, and Botrytis.

It seems that many of us are experiencing uneven flowering this year.  For example, some of our Merlot is almost BB size while others are still in bloom.  If that is the case for you make sure to protect bloom against Botrytis.  Also as you are aware, from bloom to 4-5 weeks after bloom is a critical period for black rot, downy mildew, and powdery mildew berry infection.  It is very important to protect your clusters around this time of the season!

Tuesday, May 29, 2012

Disease risks from the weekend

It did not rain much at my place (about 10 miles East of the station), so, it did not register to my mind, but Winchester area received a series of thunderstorms on Sunday night.  It stared rain around 10AM and an estimated leaf wetness period was 10 hours with an average temperature of 64F.  It was a risk event for Phomopsis, black rot, downy mildew, and Botrytis.

Thursday, May 24, 2012

Disease risks from today's rain

Winchester area received rain from a thunderstorm last night around 7:30PM.  An estimated leaf wetness period is 14.5 hours with an average temperature of 63F.  It was a risk event for Phomopsis, black rot, downy mildew, and Botrytis.

Our Chardonnay is in full bloom and Merlot is about 60-70% bloom now.  Hopefully this weather won't affect fruit set.

Wednesday, May 23, 2012

Disease risks from today's rain

Winchester area received a series of thunderstorms from around 11PM last night.  It accounted for a 11 hours of estimated leaf wetness event with an average temperature of 60F.  It was risk event for Phomopsis Black rot, downy mildew, and Botrytis infection.

Also, we are having several warm humid nights in a row due to rains.  Downy mildew pathogen prefers this type of condition for production of spores.

Monday, May 21, 2012

Bloom and disease risks from today's rain

We are about 60-70% bloom on our Chardonnay.  Merlot is still in trace bloom stage.

Winchester area received a series of rains from around 3:00 AM this morning, and relative humidity stayed above 90% until around 3:00 PM.  Thus, we had 12 hours of an estimated leaf wetness period with an average temperature of 63F.  It accounted for black rot, Phomopsis, downy mildew, and Botrytis infection event (note: Botrytis typically takes more time (>15-17 hours of wetness) to infect than the model says).  The forecast is calling for more rain tomorrow and Wednesday.  We will see how it goes.

Tuesday, May 15, 2012

More on Botrytis

I received comments from Anton on the previous post about Botrytis.  He is more concerned about Rovral (=Meteor), Vangard, and Scala than I indicated.

I wasn't very clear on the previous post about how the information has been developed.  There are two components in this story.  One is the probability of having Botrytis with resistance to some of the Botrytis materials.  So far, it seems that probability is very high for Flint (or other QoIs), high for Endura and Pristine, moderate for Rovral (=Meteor), and unknown for Vangard and Scala.  The other component is the level of resistance.  It is high for Flint, moderate to high for Endura, and Pristine, moderate for Vangard and Scala, and low for Rovral. 

The key point that Anton helped me understand today is that even though the resistance level against Rovral is "low", it still means that the labeled rate won't be as effective as it should be.  Thus, if there is a certain percentage of Botrytis which has low resistance to Rovral, it may result in less than optimal control of the disease.  (Note: this is based on on-going research, as Anton obtain more samples, we will get a clearer picture.)

The question is what to do.  I think the bottom line is to make sure you have a good cultural practice to lower the risk of disease outbreak.  Whether the isolate you have in your vineyard is resistant or not, if the infection conditions were not met, it cannot cause disease.  Also, make sure to rotate the mode of action.  When you rely on one mode of action, you are helping development of a resistant isolate.  Scouting is important as well.  If you see any signs of failure of spray material, please contact either Anton or me.  Anton has a very simple sampling kit for Botrytis.  Another important piece of the puzzle is your sprayer.  Make sure to maintain and calibrate your sprayer so that you can have a good consistent coverage of fungicides. 

Disease risks from today's rain and a little bit about Botrytis

There are still a chance of an afternoon rain, but here are estimated disease risks from rains from yesterday to this morning.  We had about 16 hours of an estimated leaf wetness period with an average temperature of 63F.  It was infection events for Phomopsis, black rot, and downy mildew. 

I think most of us are getting close to or at bloom.  Please remember that a period between bloom to 4-5 weeks after bloom is a critical time for fruit infection by powdery mildew, downy mildew, and black rot.  Also, at bloom, we recommend protection spray against Botrytis because it can infect flower parts and either resides in it or stay with flower debris until later in the season.

Many of you probably remember a report from Dr. Anton Baudoin about fungicide resistance of Botrytis pathogen, Botrytis cinerea.  This pathogen can infect wide variety of hosts and it is known to develop resistance to a fungicide or multiple fungicides relatively quickly.  Thus, Anton is investigating what is happening with Botrytis found on grapes.  He shared his preliminary findings with the Viticulture note earlier this year.

Here's a synopsis: So far, Elevate, Switch, and Rovral (Meteor) are Good, Scala and Vanguard are OK, Endura, Pristine, Flint are in question (i.e., it may no longer provide an adequate control, if you have resistant isolates).  As far as I know, Luna Experience provides a good protection, and the same will go with Inspire super; however, Botrytis component of these two products are in the same group as Endura (boscalid) and Vanguard, respectively, so, it is possible that Botrytis will figure the way out, especially for Luna.  Luna's SDHI component (fluopyram) is different from boscalid, but they are under the same FRAC code (= the same mode of action).  Whether boscalid resistance isolates are resistance against fluopyram or not is still unknown.   Their partner material is a DMI for both Luna and Inspire, but DMI does not provide much protection against Botrytis.

Luckily, Elevate (FRAC 17), Switch (FRAC 9+12), Rovral (=Meteor FRAC 2), and Scala and Vanguard (both are FRAC 9) are in different mode of action groups.  Thus, you can rotate them around.

Also, please keep in your mind that cultural practice can provide many benefits to Botytis management.  A good air circulation within canopy to promote quick drying time and lower relative humidity really works.  Plus, prevention of wounding events (by birds, grape berry moth, etc) is also important.

Wednesday, May 9, 2012

Disease risks from yesterday's rain

Winchester area received rains from 11AM yesterday.  Although rain was over by the evening, the relative humidity stayed high (>90%) until this morning.  Thus, an estimated leaf wetness period was 21 hours with an average temperature of 64F.  It was an infection event for downy mildew, black rot and Phomopsis.  Also, the humid warm night promote downy mildew to sporulate.

Thursday, May 3, 2012

Disease risks from yesterday's rain

Winchester area received a series of rain from the morning to the afternoon yesterday.  Overall, we had 6 hours of an estimated leaf wetness event with an average temperature of 62F.  It was a light infection event for Phomopsis.

In addition, we are having two consecutive nights with a very high relative humidity (>90%) with warm air (>60F).  Downy mildew can produce spores under such conditions.

Wednesday, May 2, 2012

Disease risks from yesterday's rain

Winchester area received a precipitation from 3AM on May 1st, an estimated wetness period was 5 hours with an average temperature of 59F.  It was a low risk event for Phomopsis.

We are having sporadic rain events today as well.  We will see how it goes.

Sunday, April 29, 2012

Disease risks from today's rain

Winchester area received precipitation from around 9:00 PM last night to this morning.  An estimated leaf wetness period was 12 hours with an average temperature of 42F.  Although it was a prolonged wetness period, it did not accounted for disease risks because the observed temperature was too low.

Thursday, April 26, 2012

Early Season Black Rot (revised)

I received three emails from different vineyards (Southern, Northern, and Central VA) with black rot pictures.  Yes, it is a little early for us to talk about black rot, but we had very warm period at the end of March, with rain event (on 24-25th) that are warm and long enough for black rot.  I counted three black rot infection events at our location so far, thus it is not a total surprise to see it.

If you happen to have black rot now, what can you do?  Unlike Phomopsis, black rot pathogen can produce spores after 2 weeks of infection under optimal conditions (> 70F), and if you see the symptoms now, chances are it is ready (or almost ready) for spore production.  Thus, even though we are not in the critical period for berry infection, the spores from this generation will be there for berries.  (yes, it is odd to talk about bloom in the middle of April, but at this rate, it will come soon. Hopefully cooler weather will hold off a bit.  We will see...)

If you only see symptoms on a few vines, then you may ask your crew to go through vineyards (maybe as a part of shoot thinning?) to remove infected shoots and/or leaves and it should reduce the risk of next round of infection.  However, if you have many diseased shoots, this method probably won't work.

If your vines are not close to pre-bloom, you can use mancozeb to provide protection on healthy tissues.  Unfortunately, captan or copper won't provide much efficacy against black rot.  [also, please remember that we do not have any cure for infected tissues, regardless of diseases.]

For pre-bloom or at bloom spray, you can use mancozeb to protect your healthy tissues and add Rally if needed.  Mancozeb will provide a good protection, and Rally will provide a good kick-back activity (i.e., stop on-going infection after rain).  Since Rally is a DMI (or SI) material, I am assuming that other DMI (such as tebuconazole, Mettle, Revus Top, etc) (note: in the earlier post, I was listing other chemicals by mistake, sorry!) does have a similar kick-back, but I do not think we have a good data for it.  (If I can get a culture going, I will start testing on it this summer.)  The other option is a use of QoIs such as Abound, Pristine, and Reason (note: according to Dr. Baudoin, Reason probably won't do much against black rot).  The QoI's are not as good as DMIs in terms of kick back activities, but it should give you a good protection and some kick-back activities.  If you decided to go with a QoI, please mix with mancozeb since QoIs are more prone to resistance development than many other classes of fungicide.

As usual, the decision to mix a DMI or QoI to the mancozeb spray depends on the weather and also what is going on with your vineyard(s).  If you had powdery mildew issues in the past few years, adding a DMI will also benefit to the control of powdery mildew too.  Also, even if you use mancozeb, a rain storm may wash it off from the tissues.  Then a follow-up DMI application may make sense.  On the other hand, if we end up having a very dry period, and you have not have much powdery mildew in the past, the addition of a DMI or QoI won't be needed simply because the black rot fungus requires water to successfully infect grape tissues.  You still need a material for powdery mildew, but sulfur may be sufficient.

Personally, I prefer to see the use of a DMI around bloom for powdery mildew.  It has a good kick-back activity against powdery mildew and black rot, thus, it makes sense to me to use it for this critical period.  For more detailed discussion on the use of these materials, please refer to my workbook, which you should be able to find it on the right-hand side of this blog.

Also, for the future reference, please make sure to remove your infected clusters out from your vineyard.  Dropping them off to the ground won't do much.  Infected clusters will produce black rot spores that are capable of both airborne and rain splash dispersal for the entire season.


Monday, April 23, 2012

Reminder: Vineyard meeting at Barren Ridge

As Tony noted in his email, we will have a vineyard meeting on this Wednesday.
April 25th  Barren Ridge Vineyards, http://www.barrenridgevineyardsva.com/
                  John and Shelby Higgs
                  984 Barren Ridge Rd., Fishersville, VA 22939
                  Start time:  11:00 am at Barren Ridge

Directions: Take Exit 91 off of I-64 (Fishersville). Turn onto Tinkling Spring Road heading towards Fishersville. Turn left on Route 250 West. Just past the Food Lion turn right on Barren Ridge Road and follow for about 3 miles. The winery is on the left.

Topics – Seasonal disease, insect and vineyard management considerations:  Presenters include Drs. Mizuho Nita and Tony Wolf and others to be arranged. We will meet first at Barren Ridge Vineyards and then visit Afton Vineyards (Robbie Corpora managing) and Cardinal Point Vineyards (Tim Gorman).  We should conclude the vineyard visits by 4:00 pm.
                   
Contact: Michael Lachance, VA Cooperative Extension, Nelson County, 434-263-4035 Lachance@vt.edu

Disease risks from on-goin rain

A series of rain events started around 3:00 PM on 21 April in Winchester area.  We are still receiving some precipitations today, and the relative humidity was high (>90%) all the time.  Thus, so far, we have > 45 h of wetness with an average temperature of 50F.  It has been infection event for Phomopsis and black rot, and potentially for downy mildew.  (The temperature in 22nd and today is low, but when rain started it was in 70's.)  It looks like there are more bands of rain coming in to our area later today.

It has been so dry in our area, so, it was a much needed rain!

Thursday, April 19, 2012

Disease risks from yesterday's rain

Winchester area received a series of rain events from 5:30AM on 18 April.  It lasted about 10 PM.  Since the rain stopped at night, leaf wetness is still on-going (i.e., RH > 90%) as of now (~9AM, makes it 27.5h of estimated leaf wetness), and the average temperature is about 49F.  Thus, it has been an infection event for Phomopsis and black rot. 

Sunday, April 15, 2012

Disease risks from yesterday's rain

There was a very short shower went through Winchester area around midnight last night.  It lasted about 1.5 hrs, the air was relatively dry (~80% RH), and the average temperature was around 53F.  It was too short for disease development.

Tuesday, April 10, 2012

Vineyard meeting tomorrow!

It is just a reminder that we will have a vineyard meeting tomorrow, starting at 11 AM at Horton vineyard and winery, then move to Barboursville.  Tony, Tremain, and I will be discussing about seasonal reminders.

Disease risks from 4/9/12 precipitation

Winchester area received some precipitation last night; however, the length of the rain event was short (30-40 min), the average temperature was low (48-49F), and relative humidity did not stay high due to wind.  Thus, it was not considered as an infection event.  What I observed from the radar was that there are several parcels of rain cloud went through our area, and some of you might have received rain for a longer time period.  Please check your local weather station for more detailed record.

Thursday, April 5, 2012

2012 Fungicide Workbook

Here comes 2012 version of "Workbook for developing an effective fungicide program for Wine grapes in VA" (<- click to download a pdf file).  If you receive Tony's Viticulture Notes, you already have it.

I have been publishing it as a "guideline" in the past, but this year, I decided to format it more like a workbook that helps you plan for the season.  I hope you will find it as a good companion to the PMG (Pest Management Guide from VCE).

I was hoping to get it ready before the season starts, but I missed it by 2 weeks.  Hopefully recent cooler weather holds off disease pathogens!

As noted in the workbook, it is still a work in progress.  If you have any suggestions or comments, please let me know.

I mentioned about uneven development in the last post, but as of this morning, our 4-yr old Chardonnay and Merlot are 100% bud break with some of them are 2-3 inches (4 leaves exposed) stage.  We are also looking for another potential frost event(s) in next two nights.  Hopefully, we will dodge them!

Tuesday, April 3, 2012

Disease risks from 4/2/12 precipitation

Rain from yesterday (4/2/12) started around 9PM on 4/1, and lasted until 2:30AM or so.  The RH was high (>90%) until 3:55AM, thus this was about 7 hours of wetness period with an average temperature of 55F.  That was Phomopsis infection event.


Our 4th year Chardonnay is about 1.5 inch growth (3rd and 4th leaf visible); however, there are noticeable differences among vines.  Some are almost 100% bud break with a significant growth and the others are less than 10% bud break with very minimal growth.

Friday, March 30, 2012

Frost damage from 3/27/12



As of 3/29/12, about 20% of our Chardonnay buds and shoots are showing the injuries from the frost event on 3/27/12.  Damages on Merlot is about 5%.  I hope your vines are OK.

Sunday, March 25, 2012

More discussion on powdery mildew!

I guess both Anton and I tend to work on Sundays...  He send me two nice pictures of flag shoots.
and
As you can see leaf surface is covered with white powder (= mycelium and spores of powdery mildew).

He also mentioned that he has used Armicarb and sulfur together and did not see any phytotoxicity.  Thus, if your intention is to fight against established colonies (whether flag shoots or late in the season), it would be a good combination.  If Armicarb or Kaligreen is too expensive for your budget, a straight sulfur application is the alternative.

The other thing about powdery mildew is the effect of cold temperature.  According to a recent study by Cornell, low temperature (8 hr of below 8C or 46F) stops the powdery mildew activities. This is another reasons why we do not see much activity of powdery mildew relatively early in the season.  Hopefully, we have enough cold (but not freezing) nights ahead of us to stop early season powdery mildew.

Flag shoots symptom of powdery mildew

In reply to the previous post about powdery mildew, Anton (Baudoin of VT) made a very good comment about "flag shoots" of powdery mildew.  This is a case of infection where powdery mildew pathogen survives on buds, and infect developing shoots from the get-go.  The result is infected shoots with retarded growth, hence people call it flag shoots.  You can see a picture from this Australian department of Ag site.

Why this is important? Since it bypasses the ascospore stage, the infection event I mentioned in the previous post will be irrelevant, and you will have conidia in your vineyard from the beginning of the season, i.e., mass production of spores can happen quickly.

Based on conversations I have had with growers in VA, flag shoots do not occur in VA growing conditions, and I have not seen this symptom yet.  This is primarily due to low winter temperatures; however, the winter we had was very mild, plus we had a dry summer (before Irene) to promote powdery mildew in 2010.  Thus, I think there is a chance of flag shoots infection in VA.  Please scout your vineyard carefully, and if you find suspicious shoots, please let either me or Anton know.

What should you do if you have flag shoots?  It will depend on the degree of infection, but if you have many flag shoots, one thing I can think of is the use of a potassium salt product (Armicarb, Kaligreen, etc).  It is a contact material, so, you will need a good coverage (note: probably not a good idea to mix a potassium salt with other products).  Then, you can resume (or start) your regular Phomopsis spray (mancozeb or captan) + sulfur for powdery mildew to protect healthy tissues.

Speaking of Phomopsis, the rain from yesterday also counts as a Phompsis infection event. I forgot to mention it!

Saturday, March 24, 2012

Initial infection event for powdery mildew

Well, it typically won't happen until May or so, but under this weather conditions, you cannot expect the usual trend.  Often time, powdery mildew is common under dry weather because powdery mildew conidia, which are primary spores during summer time, do not require water for infection.  However, ascospores, which are initial inoculums (spores), require water.  More than 1 inch of rain followed by 13 hours of leaf wetness with an average temperature range of 50-80F is required for powdery mildew ascospore infection.  Winchester area received rain starting from 9:15am today, we are having pretty much continuous rain (and it's still going), and the average temperature (at this point) is about 60F; therefore, it counts as an infection event.

If your vines already broke buds, the new growth are susceptible for infection.  Please monitor leaves for powdery mildew to see if it was indeed an infection event for you.  It typically takes about 7-10 days for disease development.

Thursday, March 22, 2012

Bud Break!

Our 4-yr old Chardonnay was about 10% bud break yesterday (the 21st) morning.  Our 4-yr old Merlot was <5% bud break. Older vines are still holding off.

Well, the season has been officially started whether I am ready or not!

Also, I updated the season template based on comments from users.  If you have any comments or suggestions, please let me know.

Wednesday, March 21, 2012

Fungicide planning template 2012

Thanks for those of you attended our first annual grape IPM workshops!  The number of attendee was about 110 people!

I am still working on the 2012 version of the workbook, and I will publish it by the end of this week.  In the meantime, I would like to share the fungicide planning template for 2012 season, which is a part of the workbook.  Please visit this link (Google Doc, no sign-in required). I won't let you edit on-line; however, you can download it as Excel file.  (I am hoping that we can come up with on-line edit option.  We will see...)  If you prefer to download Excel file directly, please let me know.

Monday, March 19, 2012

Bud swell 2012


Two weeks of 80's and 70's surely moved things forward.  When I checked our Chardonnay buds last week, it was swelling, but was still tight, but now it looks like they are ready to go at any moment. (Note: these are 4-yr old young vines.  Also, sorry for out of focus pictures.  I forgot to take my camera with me yesterday.)

Hopefully, it will go well with a longer than usual growing season, and we end up having early harvest this year!!

The first disease to be concerned is, as usual, Phomopsis.  The best management strategy against Phomopsis is use of a protective fungicide such as mancozeb or captan, since we do not have any material with curative activity.

Also, since we had a warm dry early summer before Irene, many of us saw quite a bit of powdery mildew.  Chances are, we have a plenty of inoculum.  Although we do not typically see powdery mildew until later in the season, with this warm winter, I am not sure what will happen.  I know it is not the best IPM practice, but with given conditions, I think it is a good practice to tank-mix mancozeb with sulfur (2-3 lb/A) to have some insurance against early season powdery mildew.

Sunday, February 26, 2012

IPM workshops + handout from pruining workshop

As I indicated at the VVA meeting, we are planning to have three IPM workshops this year. The dates ended up earlier than what I proposed, but with given warm weather, it may work out just fine...

5 March 2012 at Linden Vineyards
6 March 2012 at King Family Vineyards
19 March 2012 at Loudoun County Fairgrounds. 

We will quickly go over the basic of IPM, and spend most of our time to go over a season to aid you build a template for your spray schedule. We also reserve a time to discuss about the sustainable viticulture workshop. If you are interested in, please RSVP with Tremain Hatch at Thatch@vt.edu, 540.869.2560 ext. 11, since there are limited seating availabilities. It will be a full day workshop (9:30AM-4PM), so, please bring your lunch. 

Also, I prepared a handout for the pruning workshop held at AHS AREC last week.  It covers disease management consideration at pruning time.  If you are interested in, please click here to download a copy. 

Wednesday, February 8, 2012

Grape Pathology Research Report 2011

This is the document I should have included in the VVA handout.  I thought about it, but forgot to include.  If you are interested in the detailed reports of fungicide trials and also our recent activities, please check it out (pdf download).

Monday, February 6, 2012

Handouts from the 2012 VVA meeting

First of all, a (belated) Happy New Year!  I meant to upload some posts in January, but things were bit busy.

Second, thank you for those of you who attended the 2012 VVA meeting.  It was very nice to talk to many of you at the meeting, and I am looking forward to meet you at either IPM workshops (Place and time, TBD, but we are planning to have it at multiple locations at the end of March, please check this blog and also email from Tremain), or in-season vineyard meetings.

Third, I have been asked from several of you to upload a color copy of presentations from the meeting, so here you go.  This link downloads a pdf file from the beginner's workshop, and this link is for a pdf file of the talk about fungicide trials and discussions for 2012 season. (By the way, what I meant by "bee" in the presentation was "yellow jacket" as many of you have pointed out!  ;) )

Next, many of you have asked me about pruning wound protection.  As Tony described in the precious Grape Press, you can apply a product called Topsin-M to pruning wounds because VA has a special label. (i.e., it may not apply to your state, please check with your local extension agents!)  Here's a link to my older post about the use of the product, which also contains a link to the special label.  Please make sure to read the label.  It has a 2-day REI. thus you cannot go back to the vineyard for 2 days. This product will give you a protection against Bot canker which can enter through pruning wound.  Bot canker (caused by several Botryospaheria species) may or may not develop symptoms within a year or two, but there are evidence of long-term effect of this disease complex.  If you are thinking about using it, please consider spray or paint only a part of your vineyard (= leave some part of vineyard untouched), so that you can obtain comparative data.  If you wish, we can even set up a demonstration plot.  Please contact me if you wish to talk about it.

Of course, the fungicide application is not the only measure against Bot canker, and I recommend you to think about alternatives.  The double pruning that Tony described in Grape Press has been shown to very effectively protect your vines, and also I recommend not to prune if you see rains in the forecast.  As with many other fungal diseases, Bot canker pathogens require water to be disseminated and to initiate infection.  Also, if you will give a time for pruning wounds to heal, there should be lower chance of infection.  Thus, it is better to prune when weather is warmer because the wounds tend to heal faster.  In normal winter weather conditions, we probably do not have a high risk around this time of the year because the temperature is very low, but warm temperature we are experiencing and rains we have make me worry about Bot cankers.

Finally, as I mentioned at the meeting, our leafroll survey is about to be done; however, we are still accepting samples.  We found very high number of virus-infected vines from our survey, thus, we would like to know more about them.  If you would like to test your vines for leafroll viruses, please let us know.  Thanks to the VA Wine Board, there will be no fees for testing.