Friday, May 27, 2016

Quick reminder about black rot

I noticed that some of our 'Cheloir' vines are in trace bloom and also it has quite a bit of black rot. As I suspected, the cold rains we received were long enough for pathogens beyond Phomopsis to be able to infect vines. If you have not seen black rot lesions on leaves and shoots, the pictures below are good examples. If you click on them, it should open a larger picture. Please note the small dots on these lesions. These are fruiting bodies that contains spores.

Once again, most of us will be seeing bloom in the near future, and it will be a start of critical period for so many diseases. Please be on top of your game (shoot thinning, canopy management, and of course, fungicide applications). Mancozeb, as well as both DIM and QoI fungicides are very effective against black rot pathogen. Looks like we are expecting some rains again next week!

Black rot on leaves
 Black rot on shoots and rachis

Friday, May 20, 2016

Seasonal updates and notes

1) What to do this and next week
It looks like we have a window today for application, and after the rains over the weekend, next week looks good too. Right now, I am not too concerned about powdery mildew because it has been too cold and wet for this disease; however, next week will be nice and dry (I hope!) Thus, if you are concerned about powdery, you may need to add powdery mildew specific material (Quintec, Vivando, Torino, Luna Experience, etc) for your next application. Of course, something like Luna would be good for black rot, so, you may want to hold off until at bloom application (which may happen soon for people in the south)

Also, make sure to cover for downy mildew too. Although temperature has been low, with all the rain we received, I have a feeling downy mildew pathogen can cause infection. I would use a phosphonate material (Prophyt, Phostrol, etc) at this time of the year so that I can keep the use of a big gun (Ridomil product) for at bloom application, if needed.

As usual, please rotate mode of action (= FRAC code), and keep the use of newer materials (i.e., anything other than mancozeb, captan, zirum, copper and sulfur) to less than three times a season. Limiting the use to twice is even better! A phosphonate can be used more than 3-4 times per season, but don't over use it either. Tank mixing a newer material with a broad spectrum material will help too. This is for management of fungicide resistance, which is the reason why I cannot recommend QoI for downy mildew any longer.

2) At bloom application
Due to the spring frost events,  some of cultivar may ended up having a mix of shoots from the primary and secondary buds, thus, chances are they will bloom at different timing. Please make sure to cover for both blooms. At bloom protection is very important for so many diseases!

3) Phomopsis (note the yellow specks on the picture above)
Yes, we have seen it. The weather is too conducive for Phomopsis development this year. It would be very difficult for anyone to stop it. A good news is that unless it infects rachis or damage the shoot to the point it cannot grow, most of the time, damages from Phomopsis is not as critical than other fungal diseases, such as powdery mildew. However, it is one of more difficult to manage disease, once it gets out of hand, and it can also cause fruit rot. Please make a note (literary) of where (or which vines) you found Phomopsis this year.  Chances are, you will find them again on the same spot in the future because Phomopsis resides in old infected cane and cordon tissues. If it limited to a certain part of your vineyards, you may want to consider doing a spot treatment next year. Mancozeb, Zirum, captan, and phosphonate are effective materials, and QoI and SDHI materials are also effective too. Since none of them have kick-back activity against Phomopsis, nothing much we can do about the infection already happened; however, make sure to keep these materials in your tank mix so that you won't suffer from Phomopsis fruit rot.

4) Luna Experience
As I mentioned back in February, Luna Tranqulity is no longer available for grape. Also, Luna Experience received a new supplemental label for a slightly higher rate of application (click here to download for your record keeping). Please keep in your mind that Luna Experience (and Pristine) has a 5-day REI for cane work (12 hours for all the other activities).

5) Notes from NJ Twilight meetings
Thanks for those of you who attended NJ Twilight meetings last week. Here are notes from the meeting. 1) Fungicide updates and 2) Virus research updates.

That's it for today! Hopefully, we can enjoy better weather soon!

Sunday, May 15, 2016

Bloom time disease management considerations

Due to many rain events and relatively cold weather, it looks like we are somewhat back in truck in terms of the growth stages. When shoots are about 10-12 inches long (i.e., right now), downy mildew, powdery mildew, and black rot tend to show up. Then, at bloom time, flowers and young berries will be susceptible to these diseases, and young berries are susceptible until 4-6 weeks after bloom.  In addition, Botrytis, ripe rot, and bitter rot can cause infection on flowers.  Yes, it is a lots of diseases to think about. What you need to think about is which disease(s) have been the major issues at your vineyards. The disease history of your vineyards tends to repeat itself.

Downy and black rot management depend on weather condition.  I have seen cases where downy or black rot developed prior to bloom under wet conditions, and this year would be such a case, if you could not keep up with the protection. If you have concerns on downy or black rot, think about the use of a DMI or QoI material for black rot, and Phosphite (= Phosphorous acid) or Metalaxyl (Ridomil) product for downy mildew.  Revus, Zampro, and Ranman, can provide a very good protection against downy mildew. Based on the past few weeks of rain events and a trend of warm humid nights we observed, it would be a nice idea to think about downy mildew, since these humid nights can promote spore production of the downy mildew pathogen.   

As for powdery mildew, I prefer to start powdery mildew management (i.e., the use of a DMI or other newer materials such as Quintec, Vivando, Luna, etc.) at pre-bloom application in our plots due to heavy powdery mildew pressure at our plots. It seems to reduce the cases of cluster infection for us.  However, please note that in my vineyards, our trials tend not spray as often as many of you.

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 probably does not have many issues with Botrytis, especially if the canopy is well maintained.  Bloom time is important for Botrytis management because this fungus can infect flower and flower debris, and come back later when berries are maturing.

Warm weather conditions help development of ripe rot and bitter rot.  Both of them cause infection from bloom to harvest; however, you do not see actual rots until near harvest.  It is very similar to Botrytis in this regard.  Additional issue here is that both diseases can change the flavor of wine.  If you have seen ripe rot or bitter rot, it would be a nice idea to protect flowers with mancozeb, captan, Ziram, or a QoI.

For Botrytis, ripe rot, and bitter rot, please keep in your mind that early season powdery mildew management can become important to prevent these diseases.  These pathogens are very good at infecting through wounds (plus, the flower infection of Botrytis requires wounds to become rot); thus, scars, which will turn into opening of the skin, caused by powdery mildew infection on young berries can be the ideal targets for them.

Lastly, please keep in your mind about fungicide resistance issues.  You can locate FRAC code on the fungicide label (or you can take a look at our Pest Management Guide).  Even if two products are different in names or came from different companies, if they have the same FRAC code, they are basically the same in terms of fungicide resistance management.  Please rotate the FRAC code.  For newer materials such as DMI (or SI) or QoI or SDHI, my recommendation is not to repeat the application more than two times, and limit the use of it to no more than three times a season. Less number of application is better for fungicide resistance management.