Tuesday, September 30, 2008

Powdery Mildew Flagshoots - UPDATE 30/9/2008

A Powdery Mildew Flagshoot - Spring 2007.


Flagshoots grow from buds that were infected with Powdery mildew when they were formed last season. The shoots are covered in Powdery spores which then spreads onto unprotected foliage. Flagshoots are rare & hard to detect but check areas of your vineyard where you have found disease before.

We normally detect flagshoots in October, or November as the vine canopy begins to close over.
Tagging flagshoots for checking the next season is good practice.
Experience shows that Powdery finds are usually located close a tagged find from last season. Pictured we have checked the area where we found the flagshoot in 2007 and it looks clean.

Friday, September 26, 2008

Under Vine Slasher Demonstration



An effective under vine slasher.

 

I saw this demonstrated today at Ralph Mottillo’s Bethany block. It is made by Ledgard Pruning Systems. I see a lot of potential in this for our region and wanted to share it with you. Weed control holds organics / bio / sustainable back. It cost the earth in labour (and/or diesel), and it is hard to justify not using knockdown weed control which is quick and easy.


This invention could change that.


Imagine slashing your under vine weeds during winter, then either doing a summer cultivation pass or using an organically registered mild herbicide to control the rest. Next week we are treating Ralph’s block with a herbicide called ‘Slasher’ – an organic acid - which has BFA registration pending. If it works on the small stubble left behind we might just have an alternative to conventional herbicide that fits economically... (Now all we have to do is off set the carbon we burn by using the tractor).

Under vine slashing could work well in conventional vineyards, e.g. let them get weedy in winter, break up the soil etc, then under vine slash. Let the weeds spring back for 2-3 weeks, then as you get weed regrowth use a low rate of herbicide to take out the small weeds. Much easier to control than the monsters we normally go after.

 

Food for thought.

 

Under vine slashing makes organic / biodynamic / minimal input farming much easier and gives growers a valuble alternative to herbicides.


The slasher travels at 4km/hr at 1,500 rpm which is a significant advantage over cultivation methods which need high revs and slow speed (therefore have higher labour costs and burn more diesel).

Another advantage over undervine cultivation you are not relying soil moisture levels in order to control weeds. When you cultivate and the soil is too wet you create hard pans, too dry dust bowls.

What do you think?

Thursday, September 25, 2008

Organic Powdery Mildew Control in McLaren Vale

Powdery mildew on surface of a vine leaf.

Thoughts by James Hook



I am not a promoter of strict organic farming, although I see many advantages in taking techniques that are used and adapting them to conventional farming. There are positives to organic farming however these positives need to be balanced with the drawbacks. For example like organic farming has some techniques that require high-horsepower tillage equipment which uses diesel at a high rate. Conventional farming can do the same job, by using a synthetic product with a low powered four wheeled motorbike which is very efficient.

However, I can see the chemical treadmill that conventional farming has gotten us on. One of the key ways to break this cycle is to learn about the problem you are facing and combat it with knowledge rather than safety spraying.

The number one disease in McLaren Vale, Powdery Mildew, can be beaten with organic techniques.

When are grapes most susceptible to powdery mildew infection? The answer is from the beginning of flowering to the end of fruit set. Consequently the most critical time to spray against powdery mildew is from the beginning of flowering to the end of fruit set. Four weeks after the beginning of flowering (i.e. after bunch closure) is the last stage of susceptibility to powdery and generally does not pose a threat because the fruit is highly resistant to infection. After this point only leaves and bunch stalks can get infected.

Powdery Mildew is a slow creeping disease that is limited by sunlight. The best natural defense is keeping your vines open to sunlight. Open canopies that let sunlight into the fruit zone inhibit its growth naturally; these same open canopies have the advantage of suiting A grade red wine production. Open canopied red grape varieties have much less chance of developing Powdery Mildew infections than white varieties that require shading to stop sunburn.

By putting these two pieces of information together, Powdery doesn’t like sunlight and your vines are at most risk during flowering, we can make a conclusion on how best to control the disease.

You will have a much better change of organic control if you run your vineyard with techniques to let sunlight into the developing flowers and bunches. You will have a much better chance of control is you try organics on high quality red wine grapes with open canopies. If you are trying organics on whites try to keep sunlight in the bunch zone until the fruit is naturally immune.

Covercrop of the Year?


This is Prosper Tall Fescue - a strain of mediterranean fescue grass - which has grown 120cm high. Is it the covercrop of the year? We think it is close.

This has been used to de-vigour this vineyard. Note the use of sacrificial canes as another tool to try and slow the vines down.

Tuesday, September 23, 2008

Weather Damage has started to heal up - UPDATE 23/9/2008

Leaf Botrytis on the margins of grapevine leaves.
Some leaf botrytis is developing. This is only a concern in very rare cases where the developing inflorescences become infected and wither off. This has only been seen by DJ's in Grenache in 2005. 99% of leaf botrytis heals naturally.

Glyphosate Resistant Ryegrass

Glyphosate Resistant Annual Ryegrass
An increasing amount of Resistant Annual Ryegrass has been seen. This shows up as ryegrass plants that have a reduced control or no control at all after they have been sprayed with glyphosate. You may notice several large stands of ryegrass that remain green and healthy.

If you are seeing this problem seek advice. It is important to stop this ryegrass from seeding and increasing next year. If you continue to use glyphosate and increase your rate of application you will only make the problem worse.

The only solution is to with other groups of herbicide, like Alliance (Combination of Amitrole and Paraquat), or grass selective herbicides (Fulisade).





Wednesday, September 17, 2008

Weather Damage - UPDATE 17/9/2008


The most significant weather damage from this weeks high winds have been found in the vineyard sites that were exposed to westerly winds. In McLaren Vale this was Seaview, Sellicks and Tatachilla and the areas near the Gulf of St Vincent like Maslins Beach.

If your vineyard has been hit with weather damage it is important not to panic spray. Many growers will worry about leaf botrytis developing. The damage you see now will heal with calm, warm weather. If wet weather occurs your damage may turn into leaf botrytis, but even this is rarely a significant problem. Leaf botrytis looks harmful but unless it directly causes your vine shoots to snap off, or infects your infloresences (flowers), it is not affecting your harvest.

If you are concerned with your vineyards damage consider using a 'healing' product to improve early season growth. Many growers have been using seaweed based products to improve root growth. These could help your vines recover without using botryticides. Otherwise wait for good weather and strong shoot growth that will occur over the next few weeks.

Monday, September 15, 2008

Hail and wind damage - UPDATE 15/8/2008

During Monday, September 15th, high winds and hail buffeted vineyards. Fortunately 95% of vineyards have only superficial damage as thier shoots were less than 2cm long. Blocks that were past bud burst have torn leaves and some hail scarring as pictured here.

Wind damage will recover quickly if we have calm and warm weather.


Thursday, September 11, 2008

1-2 Leaf Stage EL-5-6 - UPDATE 11/9/2008

Warm temperatures have meant rapid budburst and shoot development. Vineyards on the Piedmount of the Sellicks Ranges (the name is a contraction of the Italian "ai piedi del monte", meaning "at the base of the mountain") near the Victory Hotel, Culley Rd and Ryan Rd are the most advanced. Some Chardonnay is at the 2 clear leaf stage.

Our early feeling are that the vines look to be advancing evenly.

At this early point of the season little can be seen. The four major pest and diseases are very rarely seen so soon after bud burst, if at all.

It is too early for Botrytis and Downy Mildew to start their life cycles. Light Brown Apple Moth can only be found in very low levels in other host plants.

Powdery Mildew over winters in diseased buds - these burst in 3-4 weeks as flagshoots. In our experience only 2-3% of McLaren Vale vineyards have serious issues with flagshoots. The Powdery in most vineyards begins around flowering from Cleistothecia (powdery spores which survive winter like seeds).

Bud mites (pictured) can be seen now. Levels of 1-2% are typical and shouldn't have any effect on your potential yield for this year. The stunted leaf with no growing tip is caused by the mites chewy the bud during dormancy.

Wednesday, September 10, 2008

Greentip EL 4 - UPDATE 10/9/2008

Budburst is when 50% of the block is at or past Greentip (EL 4).

Warm weather has kicked off vine development. Most vineyards appear to be running 4-7 days slower than spring 2007 which was notable warm. Is this a ‘normal’ year? We have dug up some budburst records from 2003 and compared them to this year. From the table below we wonder whether climate isn’t the only reason budburst is getting earlier. As vineyards mature (and crop loads reduce after the 1990’s fruit rush) are they becoming earlier bursting?

How does this compare to what you have observed?