Wednesday, May 20, 2015

Eutypa Control - how to limit its spread at pruning time.

  • Control of eutypa dieback can be achieved by protecting wounds from infection by the fungus, Eutypa lata or by physically removing infected wood. 
  • Wounds can be protected with fungicides, paints, pastes and biological control agents. It is also important to time pruning in order to avoid rainfall events and to maintain good sanitation. 
  • Controlling established infections is achieved by removing infected wood and retraining of watershoots from below infection. 
Pruning in wet weather should be avoided and preferably delayed to late winter when wound healing is more rapid and sap flowing.
 
Removal of dead wood from grapevines and alternative hosts in and around the vineyard will reduce the potential inoculum level.
 
The level of infection can be reduced by double pruning, the practice where mechanically pre-pruning is used to leave long spurs in early winter followed by hand-pruning to short spurs in late winter.
 
Contamination of pruning tools is NOT a major means of spreading the disease.

Wound protection

Paints and pastes
The application of acrylic paints and Greenseal paste (containing tebuconazole) are recommended as wound protectants, especially on large wounds. Other treatments such as Gelseal (tebuconazole) and Garrison (cyproconazole + iodocarb) are also effective but are not yet registered for use on grapevines.

Fungicides
Folicur (tebuconazole), Emblem (fluazinam) and Cabrio (pyraclostrobin) are the most effective fungicides tested as wound protectants but are not yet registered for control of eutypa dieback but are registered for other uses in vineyards.

Consult with your winery if you have any concerns about their use.

Use these fungicides at label rate. They can be applied efficiently to pruning wounds with commercial spray machines. It is important to direct nozzles to target the pruning wound zone and use high spray volumes (600 L/ha) to maximise coverage on wounds.

Wednesday, May 13, 2015

Bud Dissection - Q&A

Hi,


I am curious about looking at grapevine buds under the microscope.


Could you also please let me know how many buds you can dissect in an hour, as I have a uni project to do on yield analysis and the number would be of assistance.


Many thanks,

 

Andrew



Dear Andrew,

Almost anyone can learn to dissect buds, but not everyone has the patience to sit down and complete many samples. We use a compound microscope with to eye lenses that give a stereoscopic view of the inside of the bud.  This allows us to assess the internal bud structure and look at the inflorescence primordia which are the structures that develop into grapevine flowers.


Bud Dissection.


We would average two to three buds a minute, therefore it takes us between one and one and half hours to complete a vineyard (30x; 5x bud canes).  We would generally limit ourselves to three vineyards per day to keep our eyes fresh.

 
The time it takes to dissect buds under a microscope varies from variety to variety. Sauvignon Blanc has small buds and small inflorescences which make it the slowest variety to assess. Grenache has large buds and large inflorescences which are the quickest to assess.


Low bud fruitfulness and high primary bud necrosis is linked to vigourous vineyards.

 

Internal bud structure.
We perform dissections to look for low fruitfulness and assess the level of primary bud necrosis.

If we find problems with fruitfulness eg. levels below 1 bunch per bud (inflorescence primordia per bud), or high levels of bud death from primary bud necrosis, we advise growers to change their pruning in the short term and look at their management in the long term.

It is when you find blocks like these bud dissections come into their own as a vineyard tool.

DJ's agronomist Matthew Wilson says,  

"Vineyards with high levels of lateral shoot growth can show low levels of fruitfulness. Primary bud necrosis is often common in vigorous vines and this is contributing to low fruitfulness. If you can catch this before pruning you can take action to prevent correspondingly low yields at harvest."
Primary Bud Necrosis (PBN) note how the centre bud has died but the two secondary buds are viable. This would indicate that secondary buds will burst in place of the larger primary bud.

For more information refer to bud dissection and primary bud necrosis.

Sunday, May 3, 2015

Bud Dissection & Primary Bud Necrosis

DJ's are specialists in grapevine bud dissection. Bud dissections are used for determining bud fertility to estimate yield potential. They can also show the health status of a vineyard by determining the level of  primary bud necrosis. This is when the primary bud is dead, whilst the secondary buds remained healthy. This phenomenon is known as primary bud necrosis (PBN).





Above - Healthy dissected primary buds. A good sign for next season. Primary buds have on average more inflorescence primordia (what develops into your bunches), of a larger size, than secondary bunches.

A bud beginning to die (go necrotic).

Primary Bud Necrosis (PBN). Note how the centre bud has died but the two secondary buds are viable. This would indicate that secondary buds will burst in place of the larger primary bud.

30 bud samples. 

The big question is can you really get insight into next seasons crop only taking 30x buds per position?


Yes you can. The most common fault with bud dissections is in many cases they tell growers information they already know. Their shoots for next season will have between 1.2 and 1.5 bunches on average and they will prune to spurs that have already been set over the last few pruning seasons.

Occasionally blocks will have problems with fruitfulness and have levels below 1 bunch per bud (inflorescence primordia per bud), or high levels of bud death. It is when you find blocks like these bud dissections come into their own as a vineyard tool.

Contact us for more information on how this can apply to your vineyard. e: matthew@djsgrowers.com.au