How much is too little? Reduced grapevine irrigation does not seemto increase cold hardiness. By Susan McIver


C LISA SCOTT


Spiny seedpods of puncturevine attach easily to a bicycle tire.


vineyard on their vehicle tires. “I can’t get them to stop doing it,” he


said.


Originally from Australia where puncturevine is a serious problem, Martin knows first-hand its potential for damage.


Fruit bins are another means of seedpod transfer.


“An astute worker at a Summerland winery spotted pods attached to the bottom of bins of grapes grown in Oliver. The pods were picked off and the winery remains free of puncturevine,” Scott said.


Sapsford reported on pesticide applications at pre-emergence and early and late post-emergence and on seeding and mulch trials.


Although hesitant to make firm recommendations based on last year’s preliminary trials, Sapsford did say that a number of products show good promise, but none provided 100 per cent control.


The promising chemicals include Alison, Chateau, Sandea and Prism. Trials are being continued this


year.


Seeding resulted in 10 per cent control and mulch in a whopping 90 per cent.


In response to a question about the cost of mulch, Sapsford replied that he used the free green mulch available at local landfills.


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arl Bogdanoff presented the results of studies on the effects of irrigation regimes on grapevine cold hardiness in his plenary address at the 2016 Viticulture and Enology Conference in Penticton.


A viticulture biologist at the Summerland Research and Development Centre,


Bodganoff is well-known for his work on terroir characteristics and cultural management effects on grapes and wine quality.


“It takes only one very low day to cause significant damage,” he said.


The importance of cold hardiness came to the fore during the winter of 2008-09, when temperatures dropped to -


SUSAN MCIVER


Carl Bogdanoff holds tray of small chambers used to measure ice formation in buds at the Summerland Research and Development Centre.


25 C in some vineyards, injuring and killing many vines.


Previous work had shown that spraying the plant hormone abscisic acid (ABA) just after harvest increased cold hardiness by a full degree Celsius. His recent work has focused on whether or not stress induced by reduced irrigation would increase endogenous production of ABA by Merlot vines and improve cold hardiness of buds.


Working at SunRock Vineyard in Osoyoos, Bogdanoff and colleagues compared the control of two emitters per vine with irrigation every three to five days, the usual irrigation practice for the vineyard, with three reduced treatment regimes.


Two test regimes involved removing one emitter at fruit set and replacing it either just after colour change or well past harvest.


The third regime used two emitters releasing water on an alternating basis to test partial root zone drying.


“The emitter on one side would be turned on and then the one on the other side,” Bogdanoff explained.


Leaf gas exchange was measured using a portable photosynthesis system in the field.


Cold hardiness of buds was determined five times throughout the winter by measuring when ice was formed in a programmable freezer in the laboratory. And the results?


“It depends,” Bogdanoff said. Reduced irrigation did not improve cold hardiness.


“But what popped out was that a higher rate of photosynthesis correlated with bud hardiness,” Bogdanoff said.


The effectiveness of irrigation practices on cold hardiness appears to depend on how they affect photosynthesis.


Work is under way to understand more about this finding. British Columbia FRUIT GROWER • Fall 2016


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