Thursday, March 27, 2014

CropWatch End of Season Notes #V14.

KEY NOTES FOR THE FUTURE


This issue completes the tenth season of CropWatch McLaren Vale. As the CropWatch editor James Hook poses the following questions to of what could become more important over the next ten seasons.

INCREASED NEED FOR BIO-SECURITY


Ten years ago the weed species growing in vineyards were different. Undervine weed management has changed. Glyphosate herbicide resistant Wild Radish (Raphanus raphanistrum) has developed in Western Australia agricultural scientists believe that it will become established in South Australia either by the transfer of seed or by resistance developing independently here. Wild Radish has the potential to become a major weed in McLaren Vale if this occurs. In another ten years will herbicide resistant weeds be commonplace? Currently in the district the summer weeds Caltrop (Tribulus terrestris), Three Corner Jack (Emex australis) and Lincoln Weed (Diplotaxis tenuifolia) are spreading. Each season fresh infestations are occurring in new sites. Will they have spread across the entire region? The Mediterranean Fruit Fly outbreak in Sellicks Beach this year has highlighted how the introduction of exotic pests will complicate the logistics involved in contractor operations and the grape harvest. What would happen if Mediterranean Fruit Fly or worse Phylloxera lead to the introduction of permanent quarantine?

CLIMATE INSTABILITY


The 2014 growing season presented significant challenges to successfully ripening a crop at yields that are economically sustainable. Can you adapt your business to extreme weather events if they become more common? The season had started out wet with average winter rainfall, 300-350mm, but this soon turned into a dry season with effectively no rainfall after November.

There were positive impacts on vineyards (the dry spring kept disease levels low and the spread of Powdery Mildew and Downy Mildew from neglected vineyards was limited) but also negative impacts (increased reliance on irrigation and  possibly links to this seasons long flowering capfall period). Summer conditions were significantly warmer than average with two heatwaves through January which tested the limits of grapevine tolerance to extreme heat. Equally damaging were extremely high speed winds which reduced berry set, stripped leaves and reduced the size of canopies and increased the level of fruit exposure. Can you reduce the damage that heat and wind did to your vines if and when these conditions become more common?

ROW ORIENTATION


Will we need to change or trellis configuration and row orientation to best weather climate extremes?Tropical rain is more likely under current climate monitoring. Will McLaren Vale experience longer, hot, dry summers broken up by intense rain? How do we limit resulting berry splitting and the risks of Botrytis?

LOW INPUT SPRAY PROGRAMMES


With an unstable climate and more tropical rain can we continue to refine our organic, biodynamic and low input conventional farming?

Many growers are successfully using reduced sprays inputs, in terms of both number of applications and the rate of agrochemicals applied, compared to a decade ago. Spray unit technology has greatly improved. Downy Mildew outbreaks are an infrequent occurrence with only one vintage since CropWatch began where it has had any significant effect on the regions fruit (2011). Using weather stations and using CropWatch as a regional information service has enabled a targeted approach to preventing Downy Mildew from building up to outbreak levels.    

While reduced input sprays are generally working well but may have some unforeseen consequences. Why is Rust Mite bronzing to leaves increasing? Do we need to keep spraying after Christmas to keep mite levels lower during March? If we are protecting our own vines less how do we deal with neglected vineyards if we have wet, high pressure seasons? The 2011 vintage did have disease spreading between vineyards.

ROOTSTOCKS AND VARIETY


What rootstock and variety configurations do we need to deal with climate instability? Can we grow white varieties of wine grapes to be financially sustainable? Or is McLaren Vale going to be a 100% red wine region in ten years time?

No comments: