Virginia Grape Disease Updates

It looks like our Chardonnay buds are swelling, which probably means that growers in the south and central Virginia either start to see bud break. Then the forecast is calling for rains next week. I guess it is a typical Virginia spring. One of the diseases you need to consider soon after bud break is Phomopsis cane and leaf spot. It causes minor leaf spots, which are more evident to our eyes, but necrotic lesions cause more critical damage on shoots and rachis. It also causes berry rot; however, it is not common with wine grapes because of our spray programs. Some cultivars, such as Viognier, Cabernet Sauvignon, and Seyval Blanc, are more susceptible to Phomopsis than the others. Phomopsis spores can cause infection requires water, and Phomopsis spores can germinate in a relatively cooler environment (the upper 40s). This pathogen tends to produce spores in spring from previously infected canes and cordons. Thus, springtime rain events are ideal for the development of Phomopsis. It is...

Our Chardonnay is about to break buds. It is about 2 weeks ahead of "normal" year, whatever it means at this point... One of the diseases you need to consider soon after bud break is Phomopsis cane and leaf spot. It causes minor leaf spots, which is more evident to our eyes, but the more critical 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.  (Typical shoot symptoms) 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 vital to protect young tissues when they come out from the older canes and trunks. Since shoots will proliferate quickly, you may need to spray 1-2 times against Phomopsis, depending on how much rains we receive...

(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. Ho...

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 ...

Our Chardonnay and some of the hybrid vines are in bud swell stage as of this week, and others are tagging along.  It looks like we will see bud break very soon with warmer temperature (but next week should be cooler). 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 takes a while to establish in the vineyard. It may take 5-6 years for Phomopsis to become ...

Some shoots of our vines are about to reach the second catch wire, but I saw many that were still about 10-12 inches too. It looks like series of rain during the month of April drove developments of black rot and Phomopsis. Although it was not severe, I found several vines with leaf lesions of black rot, and a few vines with Phomopsis. Tan-colored lesions are symptoms of black rot. If you click the image, it will open a larger file where you can observe fruiting bodies (tiny black specks) within these lesions. It is a bit difficult to see, but, please note the holes on the upper picture (in the blue circled area). The lower picture shows more characteristic leaf spots of Phomopsis cane and leaf spot. For management tips, please refer to my  around bloom disease management consideration post.  Please remember that clusters will be susceptible to black rot from bloom to 4-5 weeks after bloom. Looks like Winchester area is expecting chances of rain on Friday, M...

Our Chardonnay and some of the hybrid vines are in bud swell stage as of this week, and others are tagging along.  It looks like we will see bud break very soon with warmer temperature coming up next week. 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 takes a while to establish in the vineyard. It may take 5-6 years for Phomopsis to b...

Our 7-yr old Chardonnay vines are in bud swell stage, and others are tagging along.  It looks like we will see bud break in a week or two. One of diseases you need to consider this time of the year is Phomopsis cane and leaf spot .  It causes minor leaf spots, but more importantly, it can cause necrotic lesion on shoots and rachis.  It also causes berry infection; 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 coverage for these diseases are also working as management of Phomopsis, especially later in the spring/summer. Phomopsis takes a while to establish in the vineyard; however, once it is established, it is difficult to get rid of this disease.  Some varieties, such as Viognier and Seyval blanc, are more susceptible to Phomopsis than others.  Phomopsis tends to become noticeable as a vineyard gets older becaus...

Our young Chardonnay vines are in bud swell stage, and others are tagging along.  It looks like we will see bud break in a week or two. One of diseases you need to consider this time of the year is Phomopsis cane and leaf spot .  It causes minor leaf spots, but more importantly, it can cause necrotic infection on shoots and rachis.  It also causes berry infection, which is not common with wine grapes because of our spray programs.  Materials for black rot and downy mildew are often effective against Phomopsis, thus, coverages for these diseases are also working as management of Phomopsis, especially later in the spring/summer. Phomopsis tends to appear as a vineyard gets older because this disease takes a while to establish in the vineyard; however, once it is established, it is difficult to get rid of this disease.  Some varieties, such as Viognier, are more susceptible to Phomopsis than others.  The fungus survives in canes and trunks that were ...

We had a short shower event last evening; however, it was short and relative humidity did not stay high for a long time.  Thus, it was not a major disease infection event, except, probably downy mildew, since it only take about 90 min under optimal condition. Speaking of downy mildew, we have seen the beginnings of downy mildew in our experimental vineyard. Although our last application of mancozeb was only 10 days ago, rain events and humid nights probably promoted their development. At the beginning, you will see yellow circular discoloration on upper surface of the leaf.  Please note that sometimes insect can cause similar symptoms. However, if you flip over, you will see tiny white growth (please click the picture to access to a higher resolution file).  This won't happen with an insect damage. Please scout your vineyard, and if you see similar symptoms, it is probably a good idea to incorporate some of fungicides with kick-back activity.  In fact, we ...

Our 5-yr old Chardonnay is about 50% bud break stage as of today. At this time of the year, the number-one concern is Phomopsis cane and leaf spot. They produce spores on old infected cordons and trunks during the spring, and they can infect tissues even if temperature during a rain event is in 40s. Only option we have against this disease is a protective application of fungicide, such as mancozeb, captan, and Ziram. A QoI fungicide such as Abound and Pristine are also effective; however, I would recommend keeping them for the later part of the season.  Since they can be active under cold rain event, my recommendation is to protect even when shoots are about 1-3 inches long. The decision to spray for Phomopsis also depends on the history of the vineyard. The vineyard with previous history of Phomopsis tends to carry the same issue year after year.  You are probably wondering about the risk of Phomopsis from this week's rain.  At our vine...

 It seems that we will observe sunny days with 60-70F for next few days.  Hopefully, the night time temperature won't drop too low.  Our Chardonnay vines are showing a little bit of deformation on leaves, probably due to the low temperature during the night.  Unless we will have more cold nights, it should overcome the stress.  Most of our early varieties (e.g., Chardonnay, Merlot) are in this stage (1-2 inches long).  Please note that the flower cluster is already exposed at this point.  Fortunately, we are not expecting a rain event soon, but at this point, the shoot is susceptible to Phomopsis.  If the fungus successfully infects rachis tissue, it may cause a premature fruit drop later in the season.  The picture on the right was taken last year.  As you can see, a part of rachis became necrotic due to Phomopsis infection, and berries were dropped because the rachis is dead.  The fungus survives in canes and trunks that are ...

We hit 90 F this afternoon.  This warm weather made things go little faster than we would hope.  About 50-60% of our Chardonnay and Merlot are in the stage of bud break, my Cabernet Sauvignon is still holding tight, but I saw Cabernet sauvignon in the other vineyard is about 40-50% bud break stage.  (FYI, last year we hit 50% bud break around 4/25.) Some of us are expecting to see some showers on this Thursday to Friday. It will depend on the history of your vineyard and also the condition of the rain, but if you: 1) experienced severe Phomopsis outbreak in the recent years; 2) see your early varieties are already breaking buds; and 3) are expecting that the rain will sustain for a long time (5-6 hours), then you may need to think about a treatment against Phomopsis. For example, at Winchester, it looks like we have 60% chance of rain from 2 pm Thursday and the temperature is forecasted to be in 70's.  It will be in the same condition until the middle of the ni...

(Today's picture is our friend Phomopsis again! Left side has more spots probably because it is closer to the vine where the fungus survives and produce spores. Spores were rain splashed to the leaf to cause infection.) It seems that pretty much all over Virginia is expecting some type of rain during next few days. I do not know how "30-40% chance of thunderstorm" turns out, but if your last spray was more than two weeks ago and/or your vines have grown a lot from the last application, then you may need to be prepared for these chances of rains. As I noted yesterday, please adjust your spray materials and spray amount based on your vine's growth stage.

Our low was low 40's this morning. It suppose to be warmer tomorrow and I hope that we do not get any frost damage. We'll see. We received several disease samples today which I'd like to share with you. The first one is crown gall. This is caused by a bacterium called Agrobacterium vitis . This gall formation is due to genetic modification caused by the bacterium to the infected grape vine. Sometimes it is only a cosmetic damage, but the gall tissue could girdle the vine and restrict the movements of water and nutrients, then results in the death of the vine. There are some chemicals and biological agent available against gall formation and prevention of the disease, but as far as I know, none of them are very effective as you would expect from other chemical treatments such as fungicides. Removal of the infected vine and then replacing with a certified vine is the common method of management. However, you need to keep in your mind that this bacterium can survive i...

As you may noticed, temperature has been declining since this morning. National weather service is issuing frost advisory from 4 to 9 am tomorrow (Monday) morning for Frederick county. Please check your local weather. Recent series of rain events are providing enough moisture to vines to push their shoots rapidly, and these succulent tissues are sensitive to stresses. If you are the lucky one with one of air circulation systems (propeller etc), this may be the time to use it. Hopefully, your vines won't experience frost damages. Our Chardonnay was about 80% 7-8 leaves unfolded (~10-inch or longer), and Cabernet sauvignon was about 20% 7-8 leaves unfolded (7~10-inch) as of today. (Phomopsis symptoms on a vine in our experimental vineyard, 5/17/09) As for disease concerns, we experienced rains and thunderstorms yesterday from 6:20 pm to 10 pm, then there are light rains here and there until 2 am or so. The relative humidity was above 90% until 3:20 am. Temperature started of...

It has been a very sunny weekend in 70's. I can take this anytime. Last night, RH was 4-50% and temperature was around 64F. I think it was little too dry for downy mildew to be happy. Speaking of disease, I found some leaves and canes showing an initial symptom development of Phomopsis today. We have untreated vines for disease observations, and I'm hoping that these vines will provide us nice cases of diseases throughout the season. The hard-to-see dark spots with yellow hallo are from Phomopsis infection on leaf. If you take a look at shoots, what you see is: Small necrotic spots (around the center) which can be expand later in the season. Dr. Mike Ellis' group at the Ohio State is currently working on the infection process of this fungus. Based on observations on the production of the fruiting structure in my previous experiments, it looks like this fungus can spread underneath the epidermal tissue even if we do not see clear symptoms. At which point the sp...

I noticed several errors and typos, so, I updated " Notes on Phomopsis ". ( Link has been changed, please use this one: 6/2/09 ) In Winchester, Chardonnay is almost ready to bud break, and Cabernet sauvignon is still in bud swell stage.

I've learned that southern and central regions already seeing bud breaks among early varieties. Since early season protection (1-3 inches, no later than 3-5 inches) is a critical timing for Phomopsis management, I uploaded "Note on Phomopsis" which is a part of topics I will be presenting at the next vineyard meeting (4/29/2009). I'm planning to add information about black rot and powdery mildew in the near future to this note, but in the mean time, please take a look at this draft, especially if you have issues with Phomopsis in your vineyard. Hopefully, it will help your decision making.