- Author: Brooke Jacobs
The Fruit and Nut Research and Information Center just released a new booklet developed in collaboration with University of California faculty, Cooperative Extension Specialists and Advisors, and the California Pistachio Research Board.
Over the past two years I scoured through file cabinets, slide trays and microfiche (do you remember those?) in the UCD Shields Library basement to compile a collection of pistachio deficiency symptoms photographs. This collection was bolstered by a unique series of images from the dissertation of Dr. Valdemar Gonzalez-Reyna, a graduate student with Dr. Kay Uriu in the Department of Pomology in 1986. As a graduate student Dr. Gonzalez-Reyna conducted a series of controlled greenhouse experiments to characterize the symptoms of individual nutrient deficiency in pistachio. His images are combined with images from the R. Beede (UCCE Advisor emeritus, Kings County), Dr. Brown (Professor, Dept. of Plant Sciences, UCD), and Dr. Ferguson (UCCE Specialist, Dept. of Plant Sciences, UCD) taken at field calls throughout the state and later verified with leaf nutrient analyses.
It is our hope that the images and descriptions available in this booklet will provide a valuable companion to leaf and soil nutrient analyses in diagnosing potential nutrient deficiencies in pistachio. To get a free copy of the booklet contact your local Cooperative Extension Farm Advisor. This project was developed with funding from the California Pistachio Research Board.
Authors:
Dr. Valdemar González-Reyna
Professor Emeritus, Instituto Nacional de Investigaciones Forestales, Agricolas y Pocuartas, Coahuila, Mexico
Robert Beede
Farm Advisor Emeritus, University of California Cooperative Extension, Kings County, CA
Dr. Louise Ferguson
Extension Specialist, University of California Cooperative Extension, Department of Plant Sciences, UC Davis, CA
Dr. Patrick Brown
Professor, Department of Plant Sciences, University of California, Davis, CA
Dr. Brooke Jacobs
Associate Specialist, Fruit and Nut Research and Information Center, Department of Plant Sciences, University of California, Davis, CA
- Author: Brooke Jacobs
University of California (UC) Cooperative Extension Advisors and Specialists have received an overwhelming number of inquiries from the press and growers regarding the effects of the current drought on California tree crops. To address these questions I will be posting several blogs over the next few months which highlight relevant research conducted by UC Professors, Cooperative Extension Specialists, and Farm Advisors.
Foliar spray research in walnut and almond
Dr. Bruce Lampinen (UC Cooperative Extension Almond and Walnut Specialist) has been conducting applied tree crop research for over 15 years in California. Beginning in 2005 he became interested in understanding the effects of foliar clay mineral (kaolin) sprays on walnut and almond nut quality and tree physiology. Kaolin sprays are typically advertised to manage pests, reduce sunburn, and minimize water stress by lowering leaf temperatures. Dr. Lampinen conducted a series of experiments in almond (Nonpareil variety) and walnut (Howard, Chandler, Vina and Tulare varieties). His research team compared trees sprayed with commercially available kaolin foliar sprays and unsprayed control trees. They carefully measured many aspects of tree growth and physiology including photosynthetic rate, light interception, water use, and stem water potential. Overall, Dr. Lampinen's research yielded four conclusions regarding the use of foliar sprays to reduce sunburn or drought stress:
1) Sunburn temperature threshold for walnuts is 1220F. Although air temperatures never exceeded 122oF (50oC), hull temperatures over 122oF were observed in nuts fully exposed to afternoon sun. Temperatures above this threshold were most common in the south west section of trees due to increased light exposure at the time of day when air temperature is greatest.
2) Foliar sprays consistently lowered leaf temperatures resulting in increased water use. Trees sprayed with kaolin had lower leaf temperatures mid-day. As a result, the natural response of individual leaves to close stomata during dry, hot summer afternoons and prevent water loss was over-ridden. Some trials indicated that overriding the natural response of leaves to dry and hot conditions resulted in greater tree water use, potentially inducing water stress.
3) At the orchard level the rate of sunburn damage did not differ between trees sprayed with kaolin and untreated control trees. The primary determinant of sunburn was the location of individual nuts within the tree. Nuts in the south west quadrant of a tree had the highest levels of sunburn.
4) Foliar sprays did not significantly increase yield in any of the experiments. Occasionally yield in large, healthy trees was reduced when sprayed with kaolin. Although the effects of foliar sprays varied among experiments from neutral to negative, they did not result in a significant increase in yield. Occasionally, in large healthy trees with canopy light interception greater than 80%, foliar sprays reduced yield significantly.
Links to relevant publications and research reports:
B. Lampinen, K. Kelley Anderson, S. Metcalf, and C. Negron. 2006. Effects of kaolin clay particle film on leaf temperature, nut temperature and sunburn susceptibility in walnut. Walnut Research Report.
‘A. Rosati, S. Metcalf, R. Buchner, A. Fulton and B. Lampinen. 2006. Physiological effects of kaolin applications on well-irrigated and water stressed walnut and almond trees. Annals of Botany 98 (1): 267-275
‘A. Rosati, S. Metcalf, R. Buchner. A. Fulton and B. Lampinen. 2007. Effects of kaolin application on light adsorption and distribution, radiation use efficiency and photosynthesis of almond and walnut canopies. Annals of Botany 99 (2): 255-263
C. DeBuse, J. Hasey, K. Kelley Anderson, S. Metcalf, L. Contador, B. Stewart, M. Glenn and B. Lampinen. 2010. Kaolin particle clay film effects on physiology, quality, and productivity in Tulare and Howard walnut. Walnut Research Reports.
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- Author: Jodi Azulai
- Posted by: Brooke Jacobs
UC IPM has completed another tutorial about using the degree-day tools on our Web site to go along with Walt Bentley's presentation about degree-days to time insecticide applications in fruit and nut orchards.
Peach twig borer larvae damage growing shoots and their feeding creates shallow channels and surface grooves in the nutmeat. Accumulating degree-days let's you know the best time to manage peach twig borer—when peach twig borer larvae are young and before they have chewed their way into shoots where they're protected from insecticides.
According to the Almond Pest Management Guidelines, put out pheromone traps to determine the biofix:
- Place one peach twig borer pheromone trap per 20 acres (but never less than two traps in smaller orchards) by March 20 in the southern Central Valley and April 1 in northern areas.
- Monitor twice a week to identify the biofix date (when the first male is trapped in April).
- Start accumulating degree-days on the biofix date.
Monitor trees for shoot strikes in mid-April. Make sure strikes are caused by peach twig borer and not Oriental fruit moth. If several strikes are seen in each tree by late April, a spring insecticide application may be necessary. Time it to kill first-generation larvae before the majority of them chew their way into shoots:
- 300 to 400 degree-days after biofix, if applying insect growth regulators
- 400 to 500 degree-days after biofix, if applying conventional insecticides
For more information about peach twig borer see the UC Pest Management Guidelines for almonds. For more information on degree-days visit our degree-day web page.
- Author: Brooke Jacobs
Our second annual Pomology extension course finished with a fun, and only slightly rainy, four day field tour throughout California. Course instructors Professor Ted DeJong (Professor, UC Davis), Carlos Crisosto (Cooperative Extension Specialist) and I drove twelve passenger vans north to Corning, south to Hanford, and many points in between. Thirty of the students from the first week of our course stayed on to tour a wide range of UC experiments, processing and packing facilities, nurseries and orchards.
This year our field tour was jam-packed with help from our UC ANR farm advisors and specialists. I would like to thank the following UC ANR advisors and specialists for contributing interesting and unique stops to our field tour.
- Franz Niederholzer, UCCE Farm Advisor and Director of the Nickels Soil Lab
- Bruce Lampinen, Walnut and Almond UCCE Specialist
- Bob Beede, UCCE Farm Advisor Emeritus
- Mike McKenry, Nematologist Emeritus at Kearney Agricultural Research & Extension Center
- Deborah Golino, UCCE Specialist and Director of Foundation Plant Services
Allan Fulton (Irrigation and Water Resources Advisor) deserves a special thank you for braving the pouring rain to talk to our group about two new almond irrigation experiments he started recently. Thank you Allan!
Below are photos from just a few of our field tour stops. We hope to see you in the class next year! E-mail our registration coordinator Penny Stockdale (pastockdale@ucdavis.edu) right away to reserve a spot.
Bob Beede (UCCE Farm Advisor Emeritus) and Professor Ted DeJong in the pistachio block at the Kearney Agriculture Research & Extension Center
Bruce Lampinen (UCCE Walnut and Almond Specialist) describing ongoing walnut research projects at the Nickels Soil Lab in Arbuckle, CA.
Mike McKenry (Emeritus Nematologist at Kearney Agriculture & Research Extension Center) showing students the results of a large field experiment testing for differences in root structure and size as a result of different fumigation treatments.
Jeff Colombini with Lodi Farming, Inc discussing innovative orchard management practices. Jeff was recently named "Grower of the Year" by the Good Fruit Grower. Congratulations Jeff!
- Author: Brooke Jacobs
We had a fun and intense week in the second annual extension course “Principles of Fruit and Nut Tree Growth, Cropping and Management” at the UC Davis Conference Center. On Thursday morning Professor DeJong (Plant Sciences Department, UC Davis) discussed the process of fruit growth and development with the class. After that Professor Brown (Plant Sciences Department, UC Davis) explained the basics of tree nutrient uptake and fertilization. In the afternoon the class toured Wolfskill Orchard in Winters, CA and had dinner at the famous Buckhorn Steakhouse in downtown Winters.
On Friday Dr. Carlos Crisosto (UC ANR and UC Davis) lead a series of lectures on harvest, fruit maturity and postharvest biology. During Dr. Crisosto's section of the course students had the opportunity to measure fruit maturity and and participate in a sensory panel demonstration.
This week the class is on a field tour of California. More updates to come!
Professor DeJong leading the class visit to Wolfskill Orchard in Winters, CA:
Carlos Crisosto's Friday lecture on fruit quality:
Principles of Fruit and nut Tree Growth, Cropping and Management, Class of 2014!