We are always getting questions from growers like you across North America and the globe, so we closed out the year on the Vineyard Underground podcast with a Q&A episode. Fritz answered questions on topics ranging from pre-pruning to disease prevention for 2024 and all things in between.
Check out these three featured questions from the episode and tune into vineyardundergroundpodcast.com/vu035 to hear the answers to all seven of the grower questions covered in this episode.
How much pre-pruning can I do before the final pruning, and how early can I get started with that pre-pruning?
The timing of pre-pruning in vineyards depends on the vineyard size. If the pruning process typically takes four to six weeks, pre-pruning should be done approximately 8 to 10 weeks prior to bud burst. It is best to factor in some additional time in case the weather is not conducive to pruning. In the Northern Hemisphere, pre-pruning usually begins sometime in late December or early January. This aligns with the objective of ensuring the vines are in full dormancy before any cutting takes place. It is important to consider the movement of carbohydrates and other substances in the vines’ canes and tissue, as these accumulate in storage organs such as trunks, cordons, and roots. We want to be sure the vines are dormant when we begin pre-pruning.
While large-scale vineyard operations that require maximum time during the dormant period for pruning may need to start pre-pruning in December, it is generally recommended for most growers to wait until January.
When/how do you recommend applying pre-bud burst sprays of products like lime sulfur to knock down disease inoculum?
Fritz recommends applying lime sulfur for dormant spray in vineyards approximately two to three weeks before bud burst. Once the vineyard has been pruned, proceed with the lime sulfur spray according to the labeled rates. The application should primarily target the dormant wood, including the spurs where powdery mildew or anthracnose spores may have overwintered. It can also be sprayed on the trunk. If using multiple nozzles on each side of the sprayer, it is best to aim them at the trunk or the top part of the trunk nearest to the fruiting zone, as well as along the cordon, spurs, and fruiting zone.
In Fritz’s practice, he prefers to apply lime sulfur after a good rain event in spring. This is because the rain event releases spores, particularly during warmer conditions, and applying lime sulfur afterward helps destroy some of those released spores. However, if a rain event is not available or if waiting is not preferable, it is best to apply it before bud swelling and bud burst, as lime sulfur can be toxic to leaves and developing young shoots.
What are your suggestions for fungicides besides Topsin M for vine cuts and wounds?
Aside from Topsin M, there are alternative products available in the market for pruning wounds as protectants against trunk diseases. It is encouraging to know an increasing number of organic products are becoming effective, with VitaSeal being a prime example. VitaSeal is a polymer that can be either painted or sprayed on the pruning wound, forming a physical barrier that prevents fungal diseases from penetrating into the wood.
Moreover, biological products like Biotam are gaining popularity, with the University of California at Davis even conducting studies on its efficacy. Bio-Tam is a combination of two Trichoderma (fungal) species that colonize the pruning wound and compete with potential pathogens that could infiltrate it. Surprisingly, Bio-Tam outperformed some conventional fungicides in terms of protecting pruning wounds in a study by UC Davis. Perhaps a combination of such products or using only one could work, but it is worth looking into sealants and biological protectants like Bio-Tam.
If you want to learn more about the questions and answers from this blog, check out https://www.vineyardundergroundpodcast.com/vu035.
