Richard P. Buchner UC Farm Advisor -Orchard Crops, Tehama County Director Fruit and Nut Notes July 2016 Prepared by Cindy McClain Office Manager/Ag Secretary 2016 - Volume 8 UC Cooperative Extension-Tehama County 1754 Walnut Street, Red Bluff, CA 96080 Phone (530) 527-3101 E-mail: [email protected]Website: [email protected]SACRAMENTO VALLEY REGIONAL SACRAMENTO VALLEY REGIONAL SACRAMENTO VALLEY REGIONAL WALNUT NEWSLETTER WALNUT NEWSLETTER WALNUT NEWSLETTER Full color articles and photos are available on our Website: [email protected]Tipping the Scales to Favor Walnut Quality Walnut Husk Fly Update 2016 In-Season Walnut Production Considerations Selecting the Right Clonal Rootstock for Managing Soil and Pest Problems Are You Pushing Out a Chandler Orchard in the Next Year? ….Call Kat! New Website Resource for Sacramento Valley Tree Crop Production The “SACARAMENTO VALLEY REGIONAL WALNUT NEWSLETTER” is a collaborative effort of walnut research specialists working together to provide Sacramento Valley growers and industry leaders the latest research and information effecting walnut production in today’s changing environment. This newsletter will be published quarterly, be sure to look for upcoming issues!
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SACRAMENTO VALLEY REGIONAL WALNUT NEWSLETTERcetehama.ucanr.edu/newsletters/Fruit_-_Nut_Newsletters... · 2016. 6. 30. · Walnut husk fly (WHF) continues to plague walnut production
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Richard P. Buchner
UC Farm Advisor -Orchard Crops, Tehama County Director
Fruit and Nut Notes July 2016
Prepared by Cindy McClain
Office Manager/Ag Secretary
2016 - Volume 8
UC Cooperative Extension-Tehama County 1754 Walnut Street, Red Bluff, CA 96080 Phone (530) 527-3101 E-mail: [email protected]
Selecting the Right Clonal Rootstock for Managing Soil and Pest Problems Janine Hasey, UCCE Farm Advisor, Sutter, Yuba, and Colusa Counties
1Based on data from ongoing UC and USDA-ARS trials. The disease resistance indicated is only
a comparison between the three clonal Paradox rootstocks and is not necessarily the level of
disease resistance when compared to seedling black or seedling Paradox. 2In field trials with grafted trees, the vigor of the rootstock isn't necessarily reflected in the vigor
of the scion, e.g. sometimes grafted trees on RX1 and Vlach are more vigorous than on VX211. 3 Level of resistance depends on Phytophthora species.
For more information on disease resistance ratings and mechanisms of the Paradox clones, see the
bulletin on walnuts in the nursery trade, how they are propagated and understanding the
terminology, on the web at http://www.sacvalleyorchards.com/walnuts/horticulture-walnuts/
walnut-trees-in-the-nursery-trade/
Managing vigor during training on clonal Paradox rootstocks. Where clonal
Paradox is being planted and conditions will likely lead to excessive vigor (for example, virgin
tree ground, deep loamy soils or high nitrate irrigation water), avoid pushing the growth by over
irrigating or fertilizing. Overly-vigorous growth has led to serious management and training
problems in many new orchards recently. Nitrogen, in addition to what may be in irrigation water,
may not be needed on first or even second leaf walnut trees on clonal Paradox. This can be
confirmed by taking a July leaf sample. Use stem water potential monitoring to keep trees
growing at a reasonable pace by making sure trees are not at or wetter than the baseline at any
time. To slow trunk growth where excessive, keep side shoots longer during the summer.
Standard seedling rootstocks:
1) Paradox. Many growers still prefer seedling Paradox although they are very susceptible to
crown gall disease. USDA/UC researchers developed methods for nurseries to use to prevent
infection by the bacterium during the seed collection phase and other practices which can
alleviate crown gall from developing. See the article “Points to Consider in the Prevention of
Crown Gall” at http://www.sacvalleyorchards.com/walnuts/diseases-walnuts/preventing-crown-
gall/http://fruitsandnuts.ucdavis.edu
2) Black walnut. Many growers have planted black walnut in recent years because it is less
susceptible to crown gall than Paradox seedling rootstock. However, vigor is only moderate
especially on poorer soils, and in UC trials, yields were lower compared to trees on Paradox
rootstocks. Black walnut rootstocks have a place where there are salt problems because they are
more tolerant than Paradox seedlings or clones.
Potential new clonal walnut rootstocks with disease resistance. Over the last four
years, USDA and UC researchers have developed several new clones with potential resistance to
crown gall, nematodes, or Phytophthora. Field performance is being tested and compared to the
standard Paradox clones VX211, RX1, and Vlach in five trials with the local UCCE farm
advisors in Tulare, Sutter, Lake, Glenn and Solano Counties. Stay tuned.
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