Virginia Grape Disease Updates

Thank you again for those of you who showed up at the vineyard meeting. As I mentioned in the previous post, information I presented can be downloaded from here too. In Winchester, it rained again after the previous post. It started from 2:15pm and lasted until 19:55pm; however, relative humidity was near 100% until now (9:15 am, 4/30/2009), and there were almost no wind until 6:20am, thus, chances are that leaves did not have a chance to dry out. Average temperature was about 47F, and a total precipitation was about 0.24 inches. Temperature was little lower than the requirement for Phomopsis infection and powdery mildew ascospore discharge event. However, with combination of rain in the morning of 29th, it might be enough for powdery mildew ascospore discharge. Hopefully, this rain event was not good enough for Phomopsis and we do not need to worry about it (at least for now... local weather forecast does not look promising). At the same time, I'm aware that Madison cou...

As of noon yesterday (4/28/09), our Chardonnay was 100% bud break with more than 50% of them with lower two leaves unfolded. Some were as advanced as the picture. Cabernet sauvignon varied with vines, but some were close to 70% bud break with a few buds with lower leaves unfolded, and others were about 30%. This morning, we had a shower (~0.08 inch from 6:40 am to 8:45 am, average temperature was around 52F). The rain was short, but RH has been fairly high after the rain, thus it may be enough for Phomopsis to cause light infection; however, considering how dry we have been, it may not have much activity by this fungi to initiate spore production and release. This rain was little shy for condition for powdery mildew fungi to release its spore (ascopsore) to the air (it requires 0.1 inch or more plus 2.5 hr of wetness at >50F) . We are expecting series of short rain events in next few days. I'll keep track of them as much as I can. I'm heading to a vineyard meeting...

Wow, we had another above 90F day here in Winchester. As of noon today, Chardonnay was 100% bud break with about 50% of them had fully expanded lower leaves. Cabernet sauvignon was about 30-50% bud break (variable with vines), some with fully expanded lower leaves. We are still expecting rain from tomorrow night to Wednesday. (60% chance of precipitation) This is an example of cutworm damaged leaf. Surprised to see it coming up with half a leaf gone, though.

As of noon today, Chardonnay was about 90-100% bud break; some are with fully expanded basal leaves. Cabernet sauvignon was about 15-20% bud break. I won't be surprised to see 100% bud break tomorrow on Cab sauvignon at this rate (the forecast is again in 90's).

We had a beautiful Saturday here in Winchester. Temperature high was above 90F and as you would expect, vines are pushing their buds. As of noon, Chardonnay was about 10-15% bud break and Cabernet sauvignon was still in bud swell, but buds became larger than previous few days. We'll see what happens tomorrow. We are expecting slight chance of rain on Wednesday and Thursday. It seems these are isolated thundershowers, thus, I'm not sure it will be enough duration and amount of rain to be concerned about Phomopsis infection. But as I mentioned in the notes , it takes only 4 hours under the optimal condidtions (temperature between 60-70F) for Phomopsis fungus to cause light level of infection. And this fungus starts to be active around this time of the year. If you had Phomopsis in previous years, this fungus can survive for several years and produce spores from infected older canes and trunks. Thus, even if you didn't see Phomopsis problem last year, you may still...

We have seen some damage due to climbing cutworms on Chardonnay. Since I'm not an entomologist, I'll refer to Dr. Pfeiffer's page for the description of the insect. Virginia Tech's grape diseases and insects in vineyards has spray recommendations for cutworms. Some chemicals listed in the guideline can be harmful to beneficial insects such as bees which are very active right now with apple blossoms. Please refer to the label before you apply it. When you are in doubt, please consult local extension agents.

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.

We ended up having 70's pretty much a whole day, and as you guessed, buds are swelling even more. And I found one bud actually broke. This is only one out of so many, but others will follow soon. We are having warm rain events, and it seems continue on for next 2-3 days. Hopefully others stay put during this rain event. Cab sauvignon, on the other hand, is still holding off. Some buds are start to swell.

Buds are swelling! We recorded 80's today. Cab. sauvignon is still tight, but Chardonnay started moving. We are suppose to have low 50's tomorrow. Hopefully it will slow down a bit. (I need more time to prepare for the season!) I've been receiving questions about Phomopsis control lately. As you know, once Phomopsis is established in your vineyard, you will need to manage it year after year. I'm preparing a short note for Phomopsis for the up-coming vineyard meeting (4/29). I think I can share it in here in the near future for those of you who can not make it to the meeting.

Buds look still tight. It has been fairly cold winter and spring so far, but we are expecting 60's and 70's during next few days. We'll see what happens.

Testing the email posting function.  Hope it works.