Tuesday, May 4, 2010

Troubling Signs In The Vineyard: Time To Call in Disease Sleuth

Approximately 100 vines in the vineyard are showing troubling signs: dormancy; stunted growth; dried baby shoots; discolored yellowish leaves. Managing a vineyard requires being a sleuth to discern what's going on. Four cases, with accompanying photographs, are discussed below. (Click on the photos to enlarge.)

Case #1. Two blocks of 3rd leaf Petit-Sirah vines (about 50 plants) are not putting out shoots along the cordon. To paraphrase Monty Python, are they dead or just resting? It's late in the season for them not to have budbreak. At first, I thought we had burned the vines by applying too much lime sulfur mixed with organic JMS Stylet oil during their dormant spray. (Repeat, the vines were dormant, no green showing when we sprayed in winter.) Pete Anderson, who teaches vineyard management at Mira Costa Community College, assures me that is impossible. (On the other hand, in our backback sprayer the sulfur concentrates at the bottom and I'm sure these vines received an extra fortified dosage.) Pete asked me to clip the "deadwood" of the vines back to see if they are alive, and when I cut the ends of the cordon, I find that the sap is flowing. The vines seem to be alive, and shoots are coming out from the bottom of the trunks. Pete said another possibility is Pierce's Disease (PD), but to my understanding, to test for PD you need leaves, and these vines are not putting out leaves (except some new shoots at the base). At first, I didn't think PD was likely for this block, because it wasn't an area where we had seen many glassy wing sharp shooters (GWSS), which are vectors for the disease (plus, we had administered AdmirePro in the spring to ward off the GWSS). Could a pair of gophers have wiped out the vines? I began to see PD as a real possibility, so I called the San Diego County Dept. of Agriculture and left a message. My call was promptly returned (excellent customer service!) by Ms. Pat Nolan, an expert on PD whom I had heard give an engaging, authoritative lecture on PD at Mira Costa Community College last year. Ms. Nolan suggested I dig up a whole vine with roots intact so that she could run some tests to see what's bothering it. (The picture at left shows the spot where the sacrificial vine came from -- along with its colleagues down the row with no leaves). Mateo dug up the vine in protest saying it was healthy. I drove the vine down to the county office and dropped it off for Ms. Nolan's department to conduct the autopsy.

Case #2. Similar to the above, except that the vines are not dormant. They have put out shoots. However, many of the shoots have wrinkled leaves and are not vigorous. And, the leaf color is not as deep a green as healthier cousins. A whole block (30 vines of Petit-Sirah) looks similar to this. I invited Matt Hand of Southern California Entomology, a disease expert, to come and inspect. He suspects PD, but to be sure, he suggested we test it. I took leaf samples from this vine (shown at left) and brought it to the County for evaluation.

Case #3. Case three involves a row of Tempranillo vines which is the most vigorous row in the vineyard as it is at the bottom of the hill where there is actually some top soil, and, some vines may have tapped into the nutrients and moisture of the leach field. Of 25 vines in this row about 20 are impacted. The signs are little growth (which Mr. Hand calls "witchbrooming"), uneven growth (with shoots concentrated at the center of the vine and not pushing out the ends) and discoloration (which Mr. Hand calls "chlorosis"). This was an area of heavy sharpshooter concentration at the end of last year's growing season, and Mr. Hand strongly suspects PD. I'm preparing the chain saw to cut them down and a crew to dig them out and placing an order to Novavines for replacements. I sent a sample of leaves from the vine shown at left to the County for analysis, just to be sure. (PD can be transferred from an infected vine to a healthy vine by sharpshooters; hence the need to remove infected vines from the vineyard.)

Case #4 is not as clear cut. This involves the Grenache block on the opposite side of the vineyard. Very few sharpshooters have been observed in this area. Yet, to borrow a phrase from Sesame Street, "some of these vines are not like the others." The vine at left is showing slightly off colored leaves, and some very weak shoots. Could the small dead shoots be caused by too much wind? Did compost I place around the vines in Winter rob them of nitrogen? Has a dodgy gopher been attacking the vine unknown to us? Is the vine not getting enough nutrients? Concerning nutrition, it's almost time to take a petiole sample to conduct an analysis of the vine's uptake of nutrients, which is done when the grapes are "flowering." Meantime, to find out if PD could be the cause, I took a sample of leaves from this plant and sent it to the county.

So, you want to be a farmer?


Pete said...

A few others have experienced this problem this Spring. I am going to give a Pest/Disease lecture on 26 May at the San Diego Farm Bureau - would you be able to come?


Graciano said...

Hello Craig,

I have the feeling that it was the combination of Stylet oil and Lime sulfur (Which Lime Sulfur did you apply? I think there was not sufficient agitation of the mixture during the spraying operations, or too heavy a concentration (this last may be the culprit). If I were you, I would cut the trunks close to ground level, but above the graft. I had the same problem with about 60 vines four years ago. However, we do not have any disease problems, except mildew last year. It took me
Over three years to correct the vines an now are even more vigorous, why? I don't have the slightest idea, but are bearing nice clusters. My problem might be totally different to yours, but again, I would cut the trunks and allow three weeks for new growth. Thanks.


Graciano said...

At least try cutting one single vine, if it is heathy, it will regrow for sure. I have been trying to send you the work saving and other tips, but right now I am overloaded with work and taking advantage of the good weatehr after all the rains we had recently. Please let me know of the result from the tests. Thanks.

Pat said...

Nice blog and web site!

I am sending the Grenache and Tempranillo samples to Sacramento for PD testing. They seemed to have the best chance of maybe having a high enough titer of the bacterium in them to be able to detect it. Remember a negative for Xylella at this time does not necessarily mean the vine is free from PD. It means we should retest in July (or Aug. or Sept.). Results should take up to 2 wk. (Sometimes results arrive slowly, especially weeks with Furlough Fridays).

As for the whole vine you sent, I checked the roots for Armillaria and Rosellinia, 2 fungi which cause root and cane rot and did not find them. The root stock is still very much alive, although the top half of the cane was not. I did not see obvious galls of root knot nematode, which can also cause stunting. Will work on it a bit more, but I am leaning towards Pierce’s Disease or something unusual in the environment. (It is cooler than usual this year and many plants are a little slow coming out, but that does not explain the edge burn on the leaves. Did they get a recent heavy application of fertilizer that would have upped the soil salt levels?)

Craig Justice said...

Pat, thanks for your excellent service and rapid response. We have never applied fertilizer to the vineyard (other than compost in some parts this winter). Frank Bons came by today and on the Tempranillo vines noted that the "weaker" parts of the vine (i.e., a thin cordon) were showing symptoms, which he equates with PD. We'll be sure to do our petiole analysis timely to see if the "yellowish" vines are getting the nutrients they need. I certainly don't want to make a mistake by ripping out 50 of the "resting" vines if they could be saved. I've also sent the pictures to Sam at Novavines for his review.

Pat said...

Yes, I would wait for the PD results at the very least. You’ve got a big investment in them and if there is any chance that it is only a chemical toxicity that they will quickly out grow as the weather warms, it would be a shame to lose them. A week or two may make all the difference.

Sam said...

Hi Craig,

Are you seeing any discoloration near the pith of the cordons if you cut off an end?
The pith is the center of the vine, just under the cambium layer, if you cut a vine in half the pith is in the center, normally a light brown color. I ask because I was curious if your vines were possibly suffering from Eutypa die back (dead arm). Eutypa shows up as discolored tissue in the center of the vine, looks like a ¼ pie shape.

Vinogirl said...

Oh dear, they are sad looking vines.
Although a lot of deficiencies can cause chlorosis in the spring I'm not quite sure about the stunted growth. A zinc deficiency would produce a very distinct zig-zag growth pattern in the young shoots, and although your nodes look close together, they do look straight. It seems unusual that it's happening block by block...I'll have to have a think!

Craig Justice said...

The tests for Pierce's Disease and other diseases all came back negative. Interestingly, with time, most of the "trouble" vines seem to have come back and are putting out a good canopy. Thank goodness we didn't yank them all out. Patience is a virtue in the vineyard and in winemaking.

Roberto said...

Hi Craig,

I have about 100 vines with similar problems this spring. I suspect PD but am encouraged by your outcome. Can we meet sometime to talk?

Roberto Espinosa
(619) 772-0156

Craig Justice said...

It is now almost one year later. We "wacked back" the vines during pruning to one cane in many instances, and in the other instance to two or three buds at the base. We only lost about 2 vines. I doubt Pierce's Disease. I suspect that the vines were somehow damaged during the dormant spray last year (perhaps a little too much Stylet oil?) Those "troubled" vines for the most part are doing well. The Tempranillo block of "troubled vines" have shoots up to the top wire already!