We’ve had customers call in recent days describing their pre-harvest or harvest conditions as anything from “trying” to “disastrous”.
What follows is a few tips and reminders on coping with a wet harvest:
- Think twice, act once. When you are watching nature wreck havoc with your single annual opportunity to earn a living, it’s very difficult to think things through well. Try not to act spontaneously. Seek advice from those who have more seasons under their belt. Talk to your winery. Sleep on radical measures.
- Don’t get trapped in ‘chemical dependency’. Many growers report “feeling better now that I’ve sprayed something”. There are very few spray options available at this time in the season due to the short WHPs needed. As a general rule if it has a short WHP it has either a very short life on the plant (if it’s gone already it ain’t working no more), or it probably isn’t particularly efficacious anyway.
- There have been lots of calls about spraying PMS. This product is wonderfully efficacious FOR ABOUT ONE HOUR. Our experience with PMS is that it is effective ONLY if nature is on your side. If you spray it and it stays dry for several days after application, so that split and rotten berries raisin well, you will probably save some crop. PMS is a very broad spectrum disinfectant that wipes out beneficiaries and pathogens so rainfall after PMS application seems to allow botrytis and sour rots to invade with much greater rapidity and vigour than before. PMS also seems to degrade skin integrity. We believe these disinfectant type products do have a place under defined conditions as follow:
- A harvest date is set
- Uninterrupted drying conditions are likely in the period from application to harvest.
- There may be an opportunity to apply beneficial such as bacillus subtilis or ulocladium oudemensii immediately after disinfectants to fill the biota vacuum. Unfortunately, there doesn’t appear to be any data so this is just speculation on our part.
- So what does work? When disease pressure is moderate but not at epidemic proportions, cultural controls are your best bet. Get a crew in to chop out rots and splits. If there is the presence of sour rots make sure this is removed entirely (Winemakers can cope with a little botrytis but despair at the presence of sour rots). Focus on a bunch on bunch areas where the canes meet. Get the crew to leaf pluck as they go (gloves on so berries are not fingernail damaged). Run a blower or sprayer through to remove water from inside canopy.
- Remember that it always looks worse on the vine than it does in the gondola. Plant and Food Research have developed a good Application to determine Botrytis severity. It’s called Rot Bot and it’s available from your Application Store. Use it in the same indicator bays on a daily basis to track rot progression. Nothing is more persuasive to bring your harvest date forward than hard data!
- If epidemic conditions exist there are no sprays available that can help you. You just have to remove the rotten fruit as best you can and sit it out. Rarely do inclement weather conditions persist for so long that the entire crop is a write-off.
- To remove or not to remove infected fruit from the vineyard? With large blocks this is often not possible. Get the fruit thrown into the sward in the centre of the row where it will break down as rapidly as possible. Where block size or fruit value allows for removal this may be beneficial but your downwind neighbour is going to be impressed with the festering piles on the boundary! Remember that botrytis and sour rot spores are being continually brought in to the vineyard on the wind so don’t be too anal about this particular bit of vineyard hygiene.
Although we are all getting that same wet weather there is always someone who benefits and this time it’s us the Nurseryman. The abundance of rain and warm weather over the last few weeks have given us late-season growth in the Nursery that we have literally never seen before.
The vines are looking spectacular in the field if you are up this way please do come and see us. And, there are still a few vines available so take a look at the list on our Variety page.
One more thing, we are taking orders for 2018 delivery – tell us now the combination/s you’re after and we’ll graft it for you.
Rex and Donna
Misty Valley Nursery Ltd
0800 444 614