VINEYARD TIPS

During winter pruning plenty of pruning wounds are inflicted on grapevines as a result of manual and/or mechanical pruning. This also includes large wounds where arms are pruned back for renewal. When grapevines are sawed off, the wounds are even larger. Such wounds allow ingress to all the important trunk pathogens which cause premature decline in grapevines by growing in the xylem vessels thereby impeding sap flow. One of the best known and most common trunk diseases is Eutypa dieback.

Control aids

Prevention of infection/wound protection

  • Pruning wounds can be painted with a wound sealant immediately after pruning.
  • Pruning wounds can be painted or sprayed with a biological control agent immediately after pruning. Several products that contain Trichoderma are available.
  • Chemical products such as benomyl and flusilazole are effective for a short period after being painted or sprayed onto the pruning wounds, but lose their effectiveness quickly, especially when it rains.
  • Do not prune when it rains, in view of the fact that spores which infect pruning wounds are released at such times.

Wound sealants

  • Apply with a brush, sponge or aerosol can to fresh wounds (bigger than a 20 cent coin) as soon as possible after pruning.
  • After application sufficient time should be allowed for the product to dry thoroughly, otherwise it will be rinsed off by rain showers.
  • Wash brushes and sponges thoroughly in cold water after each use.
  • The person making the renewal cuts should keep a container with wound sealant and a brush/sponge on hand.
  • Several products are available for these purposes.

woundprotection1
PHOTO 1. An example of a grapevine with Eutypa dieback.
A cross section of a cordon arm with typical symptoms of Eutypa dieback. A large wound caused by arm renewal. Grapevines that are sawn off have large wounds.

Biological control

Trichoderma

  • Trichoderma species are fungi that occur naturally in soil, rotting wood, compost, roots and in plants above the surface of the soil.
  • Trichoderma can be selected as control agents for certain fungal pathogens. They produce toxins and/or enzymes that control the specific pathogen.
  • Trichoderma are living organisms and available as powders and granules.
  • Follow the storage instructions on the label and do not expose to direct sunlight. A new Trichoderma solution must be prepared each day.
  • Use a brush or sponge to paint large wounds with a Trichoderma paste. Grapevines that have been pruned already, can be sprayed with a Trichoderma solution.
  • Trichoderma colonise (grow) so quickly that they eliminate trunk pathogens on the pruning wounds.

Acknowledgements

Dr. Francois Halleen, senior plant pathologist, ARC Infruitec-Nietvoorbij.

James Kruger, Nexus.

Dr. Brendon Neumann, Madumbi Sustainable Agriculture.

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