From Fox Weather by way of CA Avocado Commission, hot weather is forecast for mid- to late- June
This is a time to make sure that trees are adequately hydrated prior to the heat spell. Once trees start losing water through transpiration, it's hard for them to absorb water and heat stress and sunburn damage can result. The trees need to be fully water, so that they can continue to transpire to cool themselves during the heat spells.
Be sure shade is available on demand when the temperature is below 80 degrees F, shade must be provided at all times when the temperature exceeds 80 degrees F, as close as practicable to where employees are working;
Shade must be provided to all employees on a rest or meal break,except those who choose to take a meal break elsewhere (editor's note: provision of shade as usual may not be consistent with social distancing recommended by various COVID-19 guidance; ag employers implementing heat illness shade requirements can ensure adequate shade consistent with social distancing requirements by staggering meal and rest breaks, but additional shade may be necessary);
Fresh, pure, and suitably cool water must be made available in sufficient quantities (replenishment is permissible) to allow each employee to drink one quart per hour;
Water is to be provided as close as practicable to location of work;
Employees must be trained about heat illness and the Cal/OSHA Heat Illness Prevention (HIP) Standard before they work in conditions where they might be exposed to heat;
Supervisors must be additionally trained in HIP compliance procedures, emergency responses, and ensuring effective communication to facilitate emergency response.
A written copy of your HIP program in English and the language understood by the majority of the employees and be available to employees and Cal/OSHA inspectors on request — this is the most frequently-cited part of the HIP standard — and probably the most easily-avoided HIP citation!
Remember: When temperatures exceed 95 degrees, employers must implement “high heat” procedures, including a mandatory 10 minute break every two hours (meal and rest periods can serve as these breaks, but if employees work beyond eight hours or waive meal or rest periods, you must still ensure the mandatory rest break occurs).
30-Day Weather Outlook for May 31, 2020, to June 22, 2020
Summary- The prevailing pattern is a high pressure ridge from N California westsouthwest or southwestward. Cold fronts coming S through California will tend to extend southwestward from southcentral-S California to the area SW – W of S California.
A long-lived pattern of troughing or low pressure will continue from southwest of Central California to about 25N then extend west toward Hawaii.
The MJO is showing a slow increase in activity over the next two weeks.
CFSDailyAI and CFSv2 suggest some rains primarily in northern California and the Sierras, and into Siskiyou Mountains and southern Oregon at times.
It is early for monsoonal showers and thunderstorms (TSTMS). However, the presence of upper lows may begin to bring tropical moisture northward into SOCAL and the Sierras, despite the lack of a usual summer monsoonal pattern.
Potential Dates of Precipitation (from Fox Weather's CFSDAILYAI system):
Salinas Valley-San Luis Obispo Co- S SierraNV:
Salinas Valley Showers: 6/2-3. Hot spells 6/4, 6/8-9, 6/11-12, 6/14-17, 6/22-27.
San Luis Ob/Edna: Hot spells 6/6, 6/9, 6/12, 6/15-17, 6/20-27th, 7/1.
Southern California Citrus/Avocado Area, San Luis Obispo Co to San Diego Co:
Southern California Citrus/Avocado Area: May 31-June 15.
Santa Barbara, Ventura to San Diego Co: No rainfall of consequence.
Hot spells:
Santa Barbara Co: 6/6, 6/12. 6/16-17th, 6/22-26th.
Ventura Co: Hot 6/16-17th, 6/22-26th.
San Diego/Orange: Hot 6/16-17, 6/22-26.
Summary – June 15 – July 15… In Northern and Central California, Hottest: 6/14-17, 6/22,27, 7/1-2.
San Luis Obispo Co... Hottest periods 6/15-17, 6/22-27.
Southern California… Shallow marine layer and hot inland. Hottest: 6/16-17, 6/22-26, 7/1-3.
Seasonal Outlook July 15 – August 31... Northern and Central California overall pattern…. Near normal rainfall (minimal). Above normal temperatures occur during all of July and all of August. Usual thunderstorms (TSTMS) in the central and N Sierra and Plateau.
Southern California: San Luis Obispo Co, Santa Barbara Co, and Ventura to San Diego Counties east through Los Angeles to San Bernardino, Riverside and Imperial Counties…. Our latest guidance is suggesting a hot period in N and Northcentral California during mid-July, but near normal behavior of the marine layer at the SOCAL coast and valley areas. Although cloud amounts should be about normal, temperatures will drift above normal due to warmer sea surface off SOCAL and Baja. Weak troughs and upper lows will intermittently develop and deepen the marine layer as is normal for summer.
Looking further ahead into Sept – Nov, Dry and persistently warmer than normal conditions develop during the late Sept through Nov Santa Ana season.
A UC Riverside-led team has created a chemical to help plants hold onto water, which could stem the tide of massive annual crop losses from drought and help farmers grow food despite a changing climate.
“Drought is the No. 1 cause, closely tied with flooding, of annual crop failures worldwide,” said Sean Cutler, a plant cell biology professor at UC Riverside, who led the research. “This chemical is an exciting new tool that could help farmers better manage crop performance when water levels are low.”
Both wheat plants were subjected to drought, but only the plant on the right was treated with OP.
Details of the team's work on the newer, more effective anti-water-loss chemical is described in a paper published today in Science. This chemical, Opabactin, is also known as “OP,” which is gamer slang for “overpowered,” referring to the best character or weapon in a game.
“The name is also a shoutout to my 10-year-old at home,” Cutler said.
An earlier version of OP developed by Cutler's team in 2013, called Quinabactin, was the first of its kind. It mimics abscisic acid, or ABA, the natural hormone produced by plants in response to drought stress. ABA slows a plant's growth, so it doesn't consume more water than is available and doesn't wilt.
“Scientists have known for a long time that spraying plants with ABA can improve their drought tolerance,” Cutler said. “However, it is too unstable and expensive to be useful to most farmers.”
Quinabactin seemed to be a viable substitute for the natural hormone ABA, and companies have used it as the basis of much additional research, filing more than a dozen patents based on it. However, Quinabactin did not work well for some important plants, such as wheat, the world's most widely grown staple crop.
When ABA binds to a hormone receptor molecule in a plant cell, it forms two tight bonds, like hands grabbing onto handles. Quinabactin only grabs onto one of these handles.
Cutler's team searched millions of different hormone-mimicking molecules that would grab onto both handles. This searching, combined with some chemical engineering, resulted in OP.
Reduced water loss visible in tomato after treatment with OP. Thermal imaging shows increased leaf temperature (right), which equates to less water loss.
OP grabs both handles and is 10-times stronger than ABA, which makes it a “super hormone.” And it works fast. Within hours, Cutler's team found a measurable improvement in the amount of water plants released.
Because OP works so quickly, it could give growers more flexibility around how they deal with drought.
“One thing we can do that plants can't is predict the near future with reasonable accuracy,” Cutler said. “Two weeks out, if we think there's a reasonable chance of drought, we have enough time to make decisions — like applying OP — that can improve crop yields.”
Initial funding for this project was provided by Syngenta, an agrochemical company, and the National Science Foundation.
Members of the research team included others from UCR, the Medical College of Wisconsin, Utah State University, and PRESTO Japan Science and Technology Agency, as well as Shizuoka, Tottori, and Utsunomiya universities in Japan.
Cutler's team is now trying to “nerf” their discovery.
“That's gamer speak for when a weapon's power is reduced,” Cutler said.
Whereas OP slows growth, the team now wants to find a molecule that will accelerate it. Such a molecule could be useful in controlled environments and indoor greenhouses where rainfall isn't as big a factor.
“There's times when you want to speed up growth and times when you want to slow it down,” Cutler said. “Our research is all about managing both of those needs.”
Coastal California is a hard environment to decide when to irrigate. Fog and rain vary from season to season and day to day. Depending on the proximity to the coast and elevation, average rainfall in Ventura is about 18 inches. That is the average of some years when we get over 40 inches with those when we get 4 inches. Below average is more the norm than above that figure. Late rains into June can happen, but the latest significant rains can also happen in January. So what is average? And based on rainfall, how do you know when to irrigate?
May grey/June gloom adds to the confusion of what might be an appropriate irrigation cycle. That cool, moist, low wind condition fog reduces water use by plants. Fog drip also adds soil moisture that the plant can use. But, as soon as the fog lifts, the wind kicks in and sucks out the soil moisture.
Water moves from the soil, though the roots, up through the plant stem and through the leaves. It's pulled by the conditions outside the leaf. The longer the air outside the leaf is dry, windy and warm, the more water is pulled out of the plant. And then the plant pulls it out of the soil to replace the water lost from the plant. It's called the cohesion-tension theory of water movement. Water molecules stick together and pull themselves along, the way a train locomotive pulls a string of freight cars. This happens whenever the conditions outside of the leaf are “drier” than inside the leaf. It happens in the winter and summer, when the soils are cold and when they are warm. It's a passive, physical process.
When plants lose water through their leaves, it's called transpiration. It's mediated by stomata in the leaves. These openings or pores are similar to the pores in our skin. People lose water off their skin and it's called evaporation or sweating. Water loss from leaves is similar to water loss from skin.
Evaporation from the skin and from leaves cools the surface. This cooling helps prevent heat stress. The leaf and skin both act as radiators. When this water loss stops, both plants and humans can go into heat stress. So water loss has an important function in both plants and humans. For plants, the stomata also need to be open in order to take in carbon dioxide to make sugar by way of photosynthesis.
The weather factors that drive water loss – water that needs to be replaced or the bodies begin to into heat stress – are the mount of light (day length, cloud cover), relative humidity (it dries faster when air is dry and it's slower when it's humid – think desert versus Florida), and windy (more wind, more drying). When water can't be delivered fast enough to the leaf, it wilts, when the human body starts drying out, the skin wrinkles and dries out. In both cases, water needs to be taken in to reverse the loss.
Temperature is important in water loss, but not as important or as much as the other drivers or humidity, day length and wind. When it's cold, leaves and skin both dry out – think freeze-drying, a very successful process for removing water from fresh food to make a light, backpacking food. Often humans respond more to temperature than these other driving factors of water loss. If it's cool, it's not necessary to irrigate the trees. A common grower refrain is, “it's winter, I don't need to irrigate.” After five years of drought, we know better about winter irrigation.
However, this “winter and it's cool, so it's not necessary to drink water while working outside” refrain is common, too. And this can be a real human health problem. Dehydration is something serious and we should all be aware of the need to drink water during these cool, windy days of spring.
Heat stress and irrigation are both more complicated than just being aware of the weather, but below are some helpful guidelines from Cal/OSHA to follow to avoid heat stress in humans. Hey, also might not be too far off for plants, as well.
Plants lose water through their leaves and it's called transpiration. People lose water off their skin and it's called evaporation or sweating. When a plant stops losing water and when people cant produce enough sweat to cool off, both overheat. The weather influences that drive this water loss - water that needs to be replaced or the bodies begin to go into heat stress - are the amount of light (day length, cloud cover), relative humidity (it dries faster when air is dry and slower when humid - think desert versus Florida), and windy (more wind, more drying). Temperature is important, but not as much as these other drivers. Think freeze-drying - a very successful process for removing water from food. Often humans respond more to temperature than these other factors and figure, when it's cool. it's not necessary to water their plants, themselves or their workers.
Heat stress is more complicated than this, of course, but below are some helpful guidelines to follow to avoid heat stress:
https://www.dir.ca.gov/dosh/heatillnessinfo.html
Cal/OSHA HEAT ADVISORY
When employees work in hot conditions, employers must take special precautions in order to prevent heat illness. Heat illness can progress to heat stroke and be fatal, especially when emergency treatment is delayed. An effective approach to heat illness is vital to protecting the lives of California workers.
California law requires employers to identify and evaluate workplace hazards and take the steps necessary to address them. The risk of heat illness can be significantly reduced by consistently following just a few simple steps. Employers of outdoor workers at temporary work locations must be particularly alert and also plan for providing first aid and emergency medical services should they become necessary. All workers should be accounted for during and at the end of the work shift. Heat illness results from a combination of factors including environmental temperature and humidity, direct radiant heat from the sun or other sources, air speed, and workload. Personal factors, such as age, weight, level of fitness, medical condition, use of medications and alcohol, and acclimatization effect how well the body deals with excess heat.
Heat Illness Risk Reduction
1. Recognize the Hazard. There is no absolute cut-off below which work in heat is not a risk. With heavy work at high relative humidity or if workers are wearing protective clothing, even work at 70oF can present a risk. In the relative humidity levels often found in hot areas of California (20 to 40 percent) employers need to take some actions to effectively reduce heat illness risk when temperatures approach 80 F. At temperatures above 90 F, especially with heavy work, heat risk reduction needs to be a major concern.
2. Water. There must be an adequate supply of clean, cool, potable water. Employees who are working in the heat need to drink 3-4 glasses of water per hour, including at the start of the shift, in order to replace the water lost to sweat. For an eight-hour day this means employers must provide two or more gallons per person. Thirst is an unreliable indicator of dehydration. Employees often need ongoing encouragement to consume adequate fluids, especially when the workload or process does not encourage breaks.
3. Shade. The direct heat of the sun can add as much as 15 degrees to the heat index. If possible, work should be performed in the shade. If not, employers where possible, should provide a shaded area for breaks and when employees need relief from the sun. Wide brimmed hats can also decrease the impact of direct heat.
Acclimatization. People need time for their bodies to adjust to working in heat. This “acclimatization” is particularly important for employees returning to work after (1) a prolonged absence, (2) recent illness, or (3) recently moving from a cool to a hot climate. For heavy work under very hot conditions, a period of 4 to 10 days of progressively increasing work time starting with about 2 hours work per day under the working conditions is recommended. For less severe conditions at least the first 2 or 3 days of work in the heat should be limited to 2 to 4 hours. Monitor employees closely for signs and symptoms of heat illness, particularly when they have not been working in heat for the last few days, and when a heat wave occurs.
Rest Breaks. Rest breaks are important to reduce internal heat load and provide time for cooling. Heat illness occurs due to a combination of environmental and internal heat that cannot be adequately dissipated. Breaks should be taken in cooler, shaded areas. Rest breaks also provide an opportunity to drink water.
Prompt Medical Attention. Recognizing the symptoms of heat illness and providing an effective response requires promptly acting on early warning signs. Common early symptoms and signs of heat illness include headache, muscle cramps, and unusual fatigue. However, progression to more serious illness can be rapid and can include unusual behavior, nausea/vomiting, weakness, rapid pulse excessive sweating or hot dry skin, seizures, and fainting or loss of consciousness. Any of these symptoms require immediate attention.
Even the initial symptoms may indicate serious heat exposure. If medical personnel are not immediately available on-site, and you suspect severe heat illness, you must call 911.
Regardless of the worker's protests, no employee with any of the symptoms of possible serious heat illness noted above should be sent home or left unattended without medical assessment and authorization.
7. Training. Supervisors and employees must be trained in the risks of heat illness, and the measures to protect themselves and their co-workers. Training should include:
Why it is important to prevent heat illness
Procedures for acclimatization
The need to drink approximately one quart per hour of water to replace fluids.
The need to take breaks out of the heat
How to recognize the symptoms of heat illness
How to contact emergency services, and how to effectively report the work location to 911.
So a question comes in about a problem with a backyard avocado tree. And it would seem the first question would be about the overgrowth happening at the base of the trunk. This a ‘Fuerte' avocado that is grafted on a seedling avocado rootstock. It's not unusual to see an overgrowth, but this is the most extreme example I have ever seen. So it's basically an incompatibility between the graft and the rootstock. In many cases this is no big problem and trees can live a long time, as this tree has.
But the homeowner wasn't asking about the unusual growth at the base, but the canker that had appeared in the center of the trunk near the base.
This has the classic white sugar exudate that occurs with a wound of any kind in avocado. The sugary sap that contains the unusual mannoheptulose 7-carbon sugar characteristic of the laurel family to which avocado belongs will ooze out of the wound and result in a white crust (Read more about this sugar at: https://www.sciencedirect.com/science/article/pii/S0254629911001372 ).
Anyway, so this backyard tree is in an area that is getting 10 minutes of lawn watering a day. Lawns and avocados don't get along. And avocados don't get along with short, shallow irrigation that result in salt accumulating in the root zone. Which is what has happened here. Salt stress and the result is an infection of bacterial canker (https://ucanr.edu/blogs/blogcore/postdetail.cfm?postnum=7920 ).
It's not fatal in an old tree like this, but it can predispose the tree to root rot. And that's not something that is easy to treat in backyard settings.
University of California Cooperative Extension Ventura County 669 County Square Drive, Suite 100 Ventura, CA 93003 Phone: 805.645.1451 Fax: 805.645.1474
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