Introduction

In order to prevent herbicide damage in young trees, especially from postemergence herbicide, standard pomological practice is to apply white latex paint to the bottom 2 to 3 feet of trunk of newly planted trees, before applying herbicides. While this may provide some level of protection, research to support this practice is lacking. In order to assess the efficacy of white latex paint in mitigating herbicide damage, a field experiment was conducted in Arbuckle, CA to evaluate the impacts of latex paint on herbicide injury in young almond trees.

 

Methods

To conduct this experiment, second-leaf almond trees were grouped into three categories: old paint (9-week old), new paint (2-day old), no paint (hardened-off for 9 weeks), and cartons. On June 20^th, 2019 treatment combinations of different rates (see treatment table below) of glyphosate (Roundup PowerMAX), glufosinate (Rely 280), or a tank mix of both were applied. Each treatment combination had 4 replicates.

 

Herbicide applications

Herbicide applications were made using a CO₂ backpack sprayer at 35 psi, and a spray volume of 20 gallons/acre. A single nozzle was held 18 inches from the trunk, moving vertically (from top to bottom) for one second on both the eastern and western side of the trees.

Herbicide Treatments
Top Label Rate	3x Label Rate
Glufosinate- 1.5lbs/ac	Glufosinate - 4.5lbs/ac
Glyphosate- 2.75lbs/ac	Glyphosate - 8.25lbs/ac
Glufosinate + glyphosate- 1.5 + 2.75lbs/ac	Glufosinate + glyphosate- 4.5 + 8.25lbs/ac

 

Trunk protection

In 2017, the block used to conduct this experiment was planted with greenhouse-grown trees. Each tree came with preinstalled cartons. Nine weeks before the herbicide applications for this experiment took place, the cartons for the “no paint” and “old paint” treatments were removed for the first time, exposing green bark. Valspar interior latex paint diluted 50:50 with water was then applied using a painter's mitt to the group of trees in the old paint treatment. This also allowed for the no paint treatment to harden off for nine weeks prior to the herbicide application. Two days prior to the herbicide application, the cartons for the new paint treatments were removed for the first time (again, exposing green bark) and painted. The cartoned treatments in this experiment never had their cartons removed.

Trunk Protection

Old Paint (9-week old paint)

No Paint (hardened-off for 9 weeks)

New Paint (2-day old paint)

Carton

 

Evaluations

Evaluations across three categories of tree stress were taken on a weekly basis, starting three weeks after treatment (WAT) to allow symptoms to develop.

1. Trunk damage: Assessments made from 3WAT-5WAT quantified the number of individual gumming sites on each trunk (see Figure 1). No further trunk gummosis was observed starting five weeks after the herbicide applications.

Rating scale--Trunk Damage
1	0 – 10 Individual sites
2	11 – 20 Individual sites
3	21+ Individual sites

 

2. Canopy stress: Evaluations were taken from 5-8WATassessingthedegreeofinterveinalchlorosis,mottledchlorosis, spotting,stackedinternodes, necrosis and stem die back.

   Rating scale--Canopy Stress
   1	Coming out of stress, exhibiting new growth.
   2	Damage, new growth may be present but injured.
   3	Leaf drop and further necrosis; no new growth present.

3. Defoliation: Ratings were taken from 5-8 WAT assessing the degree of defoliation for each tree (see Figure 2).

Rating scale--Defoliation
1	Less than 25%
2	25-50%
3	Greater than 50%
4	Complete defoliation

 

Results

Preliminary results indicate that paint as a trunk protection method may not provide significant protection from glyphosate or glufosinate. Tree stress caused by trunk-applied herbicides was lowest in most treatments with no paint at all, which suggest that hardening of the bark is key to mitigating herbicide damage in young trees. Examples of treatment combination results shown in images and graphs below.

 

Trunk damage:

Five weeks after herbicide treatments, data from the top-of-label-rate tank-mix application showed a 22% increase in trunk damage in trees with old paint, and a 4% increase in damage in trees with new paint, when compared to trees with no paint.

 

 

Canopy stress:

Eight weeks after treatment, the label rate tank-mix applications showed a 29% increase in canopy stress in trees with old paint, and a 14% increase in damage was observed in trees with new paint, when compared to trees with no paint.   

 

Defoliation:

Eight weeks after treatment, the high rate (3x) tank-mix applications showed a 40% increase in defoliation in trees with new paint, and a 20% increase in defoliation was observed in trees with old paint, when compared to trees without paint that were allowed to harden-off for 9 weeks.

 

  

Figure 2b (old paint)

Figure 2. These three images demonstrate the level of defoliation observed 5 weeks after the high rate tank-mix applications were made. Arranged in order of stress response severity: new paint (2a, above) exhibiting the highest level of defoliation, old paint (2b, above), and no paint (2c, below).

 

 

Conclusion:

Preliminary results indicate that in most treatment combinations, old and new paint as trunk protection methods did not reduce tree stress caused by trunk-applied herbicides. Allowing the bark of young almond trees to harden off for at least nine weeks reduced herbicide damage. The most efficacious trunk protection option for young almonds trees is to install a carton, though remember when cartons are eventually removed green bark may be present and susceptible to herbicide injury. Therefore, as the trees mature and cartons are removed, allow the bark on trunks of trees to harden off to minimize herbicide damage.

 

Between PG&E's public safety power shutoffs and a lack of precipitation, October was an interesting month for foothill ranchers. Many areas received a germinating rainfall in mid-September; most of that new grass withered in an October that saw only 0.02 inches of rain in Auburn. And while many operations are used to having irrigation water turned off in mid-October, the lack of rain and multiple blackouts by PG&E made getting drinking water to livestock a challenge. Last week, I sent a survey to area ranchers to help get a handle on the impacts from the public safety power shutoffs. While I'm still collecting data (if you're a rancher and have not yet participated in the survey, click on this link: http://ucanr.edu/oct19livestockwatersurvey), I wanted to share some preliminary results.

To date, 39 people have completed the survey. Most respondents receive water from the Nevada Irrigation District; an equal number use groundwater. Many operations use water from more than one source. Most of the operations responding are in Placer County, although a number of operations raise livestock in more than one county. Of those responding, 41 percent purchase winter water from their water district(s).

Here are more details on the responses so far:

If you haven't yet participated in this survey, go to this link: http://ucanr.edu/oct19livestockwatersurvey

Orietta Gianjorio

You've heard of "all systems are go."

In this case, "all systems are sweet."

The UC Davis Honey and Pollination Center will host a Sensory Evaluation of Honey Course, Thursday through Saturday, Nov. 7-9 in the Robert Mondavi Institute (RMI) on the UC Davis campus.

The three-day certificate course covers "everything in the world of honey," says director Amina Harris. It takes place from 9 a.m. to 5 p.m. each day in the RMI Sensory Building.

Attendees will taste, discuss and analyze approximately 40 varieties of honey from across the globe to hearing the latest in bee sting allergy research, Harris says. "The focus is on tasting honey using both the well-known Italian method taught at the Registry of Experts in Bologna alongside our own UC Davis research tasting protocols and techniques."

Amy Myrdal Miller

Capsule information on some of the instructors:

Joyce Schlachter, director of Food Safety and Quality, Crockett Honey, Tempe, Arizona. She worked in the honey business for 12 years. She audits honey processing facilities in foreign countries, and works with U.S. authorities, including Customs and Border Patrol in identifying fraudulent honey shippers.

Amy Myrdal Miller, nutritionist and owner of Farmer's Daughter Consulting, Sacramento.  She is an award-winning dietitian, farmer's daughter, public speaker, author, and president of Farmer's Daughter® Consulting, Inc., an agriculture, food, and culinary communications firm.

Chef Mani Niall of Mani's Test Kitchen "Baker of the Stars." Niall is a professional baker and the author of two cookbooks, "Sweet and Natural Baking" and "Covered in Honey." Mani has traveled the U.S. and Japan, presenting varietal honey cooking demos for culinary students for the National Honey Board.

Orietta Gianjorio, member of the Italian Register of Experts in the Sensory Analysis of Honey. She is a professional taster, sommelier, and international judge of wine, olive oil, chocolate and honey. She launched her career in sensory evaluation 18 years ago at the Italian Sommelier Association.

Among the other instructors:

• Suzanne Teuber, M.D., a UC Davis professor in the Department of Medicine, who focuses on allergies
• Hildegarde Heymann, a world-renowned professor of sensory science, will explain exactly how our sensory apparatus works. (See more)

The introductory course uses sensory evaluation tools and methods to educate participants in the nuances of varietal honey, Harris says. Students will learn about methods of evaluation, stands and quality in this certificate program. It's geared for anyone interested in learning how to critically taste and assess honey. Using standard sensory techniques, packers, chefs, beekeepers, writers, food manufacturers, honey aficionados will learn about the nuances of varietal honey.

Extension apiculturist Elina Lastro Niño of the UC Davis Department of Entomology and Nematology faculty and director of the California Master Beekeeper Program, will provide an update on UC Davis bee research from 11:30 a.m. to 12:15 p.m. on Friday. (See program)

A few openings remain. The fee is $799 for the three-day course.Contact Amina Harris at aharris@ucdavis.edu for more information. 

Citrus trees emit volatile organic compounds (VOCs), or odors, that are the end products of plant metabolism. Researchers can measure the VOCs emitted by a plant and create an “odorprint”. Pathogens, such as the bacterium CLas that causes huanglongbing (HLB), affect plant metabolism and alter the odor profile of the plant. Thus, the odor profile can be used to detect HLB-infected trees.

What happens once an odorprint shows the presence of HLB? Visit the Research Snapshot to learn more.

 

 

 

About Research Snapshots

We have developed short, descriptions of research projects that aim to help in the fight against HLB. These projects include traditional breeding and genetic engineering to create resistant citrus varieties, psyllid modification, using other organisms to deliver HLB-resistance genes, and early detection of the bacterium in trees.