By way of Ventura grower Sandy Hedrick. This is a compilation of nights of "firing" done by Farm Advisor Bob Brendler from 1923 to 1988 that was collected by Terry Schaeffer of The Fruit Frost Service. Can you imagine over 70 nights of freezing temperatures when the smudge pots had to be lit? Now we don't normally "fire" the pots, but use water and wind more commonly. And it's only for a few nights at the most during the winter. In the "old" you couldn't plant avocado or lemon east of Sycamore Rd, just east of Santa Paula. Now there are avocados planted in Fillmore. And apple bloom erratically out there for lack of chill hours. And in summer it's getting too hot to grow strawberries even on the coast because with temperatures above 80 deg there is poor pollination.
Brendler loved weather information and irrigation issues. He was the first person in the Ventura office to use a computer and he was the oldest Advisor in the office at the time. The weather data chart was the first type of chart that could be done on a computer.
Do you think something has changed? By the way Terry is still running a private weather service for growers in Ventura.
Click on the link: Temp Chart002
We are creatures of habit and when we see the effects of a treatment, we can often persist in seeing the same or similar symptoms and assuming the cause is the same. In a recent case, a newly planted ‘Pixie' orchard, planted in August had gone into an old ‘Valencia' ground. The trees went through an adjustment period, but still didn't look sprightly in the fall. The grower applied a hand application of urea on the rootball that within 10 days had caused the trees to go into a salt swoon. Meaning, they got too much fertilizer that burned them. The grower seeing the effect, immediately started the sprinklers, but the damage was done. Several months later the trees had either died or were still lingering, but hanging in there. The trees were still coming out of winter, but the trees hadn't perked up. It was a dry winter and some of the yellowing was due to underirrigation, that overall yellowing from lack of nitrogen and the leaves were curled. But the assumption was still that the trees were recovering from the salt burn from the urea.
Looking more closely at the trees, something else was odd about some of the trees that were continuing to die. The leaves suddenly wilted. Getting down on hands and knees and digging around the roots, there were few roots and ………………………….a tunnel. A gopher had been at this tree and the lack of roots were probably due to Phytophthora root rot. Looking around there were some old ‘Valencias' that had been hit by gophers and there were gophers mounds and runs all over the place.
So, young trees planted in the heat of the summer into root rot ground with gophers waiting in anticipation that had been salt burned in a year with little rainfall. A lot of causes for trees that generally weren't happy – triste, as they say in French.
So what are the lessons here? Avoid old citrus ground when planting with citrus, and if you can't make sure, don't plant in a stressful period. Phytophthora loves stressed trees and adding lack of rainfall an gophers and salt, just heightens the stress. Make sure to get the irrigation right. Don't irrigate them to the schedule of the older trees and start them off on one of the phosphite materials.
Wilted, yellow leaves from lack of water and Phytophthora
Gopher chewing on stem
Gopher run and lack of roots from Phytopthora and gopher
Gopher mounds in planting area
Older Valencias dead and dying from Phytophthora and gophers
Water woes are probably not going to go away, so readup on how to best manage water at this new blog.
- Author: Rachael Long
Guest post from Rachael Long, UC Cooperative Extension Farm Advisor, Yolo County
The Yolo County Flood Control and Water Conservation District (YCFC) is an agency that supplies water to farmers in northern California. The agency is at the forefront of innovative efforts aimed at banking groundwater by diverting flood waters into their unlined canals. This gives flood waters time to infiltrate soils and recharge groundwater.
Using a water right permit that they recently obtained from California's State Water Resources Control Board, flood waters from recent storms are being captured from Cache Creek as it enters the Sacramento Valley. YCFC recently opened their lateral gates, allowing the flood waters to...
Groundwater wells can fail in many ways. Sometimes the water table sinks below the level of the well. Sometimes minerals cause buildup in well systems. And, sometimes, wells get clogged with lots and lots of microbes.
Microbes can form large, jelly-like mats that lead to well failure from what is known as biofouling. Biofouled wells can be both expensive and technically challenging to repair. There are even times that repair is not possible and replacement is the only option. In Washington State, for example, researchers have encountered well pipes completely clogged by mats of bacteria....
California's Sacramento-San Joaquin River Delta region, commonly referred to simply as the Delta, is often described as a unique part of the world. Although it is located between two big urban centers – the greater Sacramento and San Francisco Bay areas – the Delta can feel like another world altogether.
This is something Michelle Leinfelder-Miles, a farm advisor with UC Agriculture and Natural Resources, knows well. She comes from a sixth-generation farming family in San Joaquin County and, after accepting her position several years ago, was happy to return “home”...
The California drought has shined a spotlight on stories of people and communities living without water. Unfortunately, lack of access to clean and affordable water is not a new issue. Water security has been an enduring challenge across the state in wet and dry years alike, particularly for disadvantaged communities. Trying to meet concerns about water availability and affordability with pragmatic action is where things get both complicated and interesting.
One approach that the state has invested a great deal in exploring is known as integrated regional water management. While it is a complex topic, the basic idea is that there are multiple needs for water throughout the...
Street-side stormwater facilities are turning runoff once seen as a nuisance into a resource. Also known as bioretention areas, rain gardens, and bioswales, these small stormwater facilities provide a decentralized approach to alleviating peak stormwater runoff and subsequent flood damages. These are particularly critical functions in cities like San Francisco where the storm and sanitary sewer systems are combined because they help managers to prevent dreaded “combined sewer overflow” events. As a bonus, stormwater facilities have also proved useful in promoting groundwater recharge and filtering pollutants as water percolates through soils.
While street-side facilities are effective in helping to manage...
- Author: Brad Hanson
Brad is a Weed Specialist at UC Davis
As most orchardists and pest control advisors are well aware, glyphosate-resistant weeds have been one of the biggest weed management challenges in California orchard crops for several years.
Depending on where you are located in the Central Valley, your biggest challenges in the glyphosate-resistant weed department are probably one or more of the following winter annual weeds. In the San Joaquin Valley, hairy fleabane and horseweed (also known as mare's tail), dominate. In the Sacramento Valley and in some North coast areas, annual or Italian ryegrass is more common. For an extra challenge, many growers have a mix of several of these, in addition to their other common orchard weed spectrums.
In developing management strategies for these winter annual weeds, we've typically focused our herbicide-based programs on timely applications of preemergence herbicides. Because preemergence herbicides generally work on germinating weed seed or very small seedlings, “timely” applications for these winter annual species usually means getting the herbicide treatments out in late fall or early winter. In normal rainfall seasons, this timing ensures water-incorporation of the herbicide at about the same time as the seeds germinate and, hopefully, good control. Mission accomplished, right?
Recently, we've been seeing new glyphosate-resistant weed challenges that require a different management approach. The species I mentioned a moment ago are all winter annuals, which means they typically germinate and emerge during our cool season and reach a reproductive stage by spring or early summer. However, several recently confirmed (or suspected) glyphosate-resistant species are summer annual grasses. Summer annual weeds typically germinate and emerge as our season warms up in the late spring and early summer and they grow well into the summer before reaching maturity. A few examples include junglerice, threespike goosegrass, and several other glyphosate-questionable species such as feather fingergrass, sprangletop, and witchgrass. So, how do these grasses present such a different challenge?
The challenge with glyphosate-resistant summer grasses is that even though we have a number of good preemergence herbicides that can work very well on grasses, these species emerge long after our typical orchard preemergence herbicide programs are applied. Thus, herbicide programs that are applied during mid-November to mid-February targeting winter annual weeds sometimes fail to control summer annual weeds that emerge in May-July. If spring applications of foliar materials like glyphosate fail because of resistance, problems can quickly become apparent. How can we use our existing preemergence herbicide tools to help address this problem?
To answer that question, it's useful to think about what happens to a preemergence herbicide when you apply it to the soil. Herbicides “dissipate” in soil, a term that encompasses a suite of processes by which the herbicide is either broken down or made unavailable. Chemists use terms like “half-life” to describe differences in dissipation rates but this doesn't exactly get at our interest in weed control performance. From a performance standpoint, it's more useful to think of a herbicide concentration threshold. When the amount of herbicide in the soil solution is above the threshold for a certain weed, it remains effective on that weed. However, dissipation processes will eventually reduce the herbicide concentration below the threshold and the herbicide begins to “break”. The threshold may occur at different levels for different weed species and dissipation rates may vary in different areas of the fields (wet vs dry areas, for example).
So, how do we typically account for dissipation of preemergence herbicides in orchard crops? I tend to think of three general strategies:
Use mixtures of more than one preemergence herbicide
Apply a higher (labeled!) rate of a preemergence herbicide
Use a sequential approach to preemergence programs in orchards.
Mixtures: Using herbicide mixtures, particularly products with different modes of action, is a great strategy for managing and delaying herbicide resistance but doesn't really help in this situation. Because herbicide dissipation rates are affected primarily by the chemistry of the individual herbicide and the environmental conditions, a tankmix will not exactly help extend the residual control beyond what we'd expect from the longest-lasting material. Or, to say it another way: if you mix a short residual herbicide with a long residual herbicide, one will last a short time and the other a long time but the mix will not last longer.
Higher rates: Many, but not all, preemergence herbicide labels have a range rates registered in a crop to account for differences in soils, required level of control, weed spectrums, etc. Within the labeled rate, it stands to reason that given similar dissipation processes, a higher rate will result in the soil concentrations of the herbicide remaining above the efficacy threshold for a longer time than a lower rate. This is generally true and is a common approach when we only have one opportunity to make a preemergence herbicide application. However, I think this is an indirect way to approach the problem of summer grasses in orchard crops.
Sequential approach: In the orchard cropping system, some growers may want to consider using a sequential approach to available preemergence herbicides to tackle problems with glyphosate-resistant summer annual grass weeds. Conceptually, this approach simply moves a portion of the winter preemergence herbicide program to a bit later in the year to late winter or early spring. A preemergence herbicide with activity on summer grasses would be applied along with the grower's spring burndown herbicide program and, thus, would be present in the soil solution much closer to the timeframe when summer grasses begin to germinate and emerge. Importantly, I think this could be achieved in many situations with no significant changes in cost, number of field operations, or negative environmental impacts.
Illustration: An almond grower who typically uses an effective preemergence program (pick your favorite program) applied around the first of December followed by a March “cleanup” treatment with glyphosate may still have difficulty managing glyphosate-resistant grasses. The grower knows that herbicides like oryzalin or pendimethalin (eg. Surflan or Prowl H2O) could help with grasses. Using the higher rate approach, the grower could use a high label rate one of these materials in December with the idea that it will persist long enough to control summer grasses emerging six months later. Using the sequential approach, the grower could move all or part of the oryzalin or pendimethalin component of the program to the March timing to more directly target those summer germinating grasses, possibly at a the same or even lower total application rate.
Who might want to consider a sequential approach? This approach requires a bit of close management attention. First, because incorporation of preemergence herbicides is key to their performance, moving some of this product to late spring will require either timely rain or overhead irrigation capabilities. Growers with solid-set or micro sprinkler systems should have little problem with this, but single- or double-line drip irrigated orchards will need to get a rain and should not delay too late in the spring.
Second, moving all or part of the preemergence grass herbicide to late in the year requires that growers know their weed spectrum. If you know or suspect glyphosate-resistant summer weeds, this may be an approach to consider. You should also have an idea of what weeds you are managing during the winter season too and make sure that your winter program still addresses that part of the weed spectrum.
Weed management in orchard crops is complex and getting further complicated by new glyphosate-resistant weeds. Because of our relatively mild climate and seasonally variable temperature and moisture conditions, we encounter weed germination and emergence in every season. Strategies to manage one fraction of the weeds present in a given orchard may not work equally well for other species. Handling shifting weed problems may require different approaches in order to make the most effective use of existing weed management tools.
The word is getting out. If you have yellowish leaves, cupped/upright and the fruit is small, it may not be Huanglongbing (HLB), but it sure seems like all of my neighbors think so. It could be just lack of water, and in a drought, that could be the most likely cause. But there are other causes of symptoms that might be associated with HLB. Citrus Stubborn Disease causes these symptoms, but also distorted fruit and shriveled, discolored seeds, and bitter fruit like HLB. Under very hot conditions, leaves on some shoots may have misshaped, blunted yellow tips with mottling similar to the nutritional deficiencies seen in HLB. The leaves can have shortened internodes, so there's a bunchy growth habit like in zinc deficiency. Fruit are small, sparse and have early drop. Again, a lot like HLB. Even more so, though Stubborn can cause stunted, thin canopies. Misshapen fruit, though can be caused by bud mites in lemon, chimeras (spontaneous mutations) and Tristeza (a viral disease). Frost damage can add further to the confusion about symptoms that might be associated with HLB.
Citrus Stubborn Disease is a serious disease that leads to reduced fruit quality and yield. It occurs most commonly in oranges, but does show up in other citrus including lemon and mandarin. It's more commonly seen in older trees that were initially propagated with infected tissue, and growing in hot, dry environments. Unlike HLB, it doesn't lead to the death of the tree, just major loss of income. It's caused by a phytoplasma (a bacteria without a cell wall) and is spread by a leafhopper. There are other hosts like mustard and cabbage that can harbor the organism to be spread to new tissue and especially young trees. Warm winters favor the spread of the infected leafhopper, like we have had this winter.
So how do you distinguish between all the possible causes that look like HLB? HLB can be tested for as well as Tristeza. There are no commercial labs that check for Stubborn. It's basically a process of elimination then to decide to test for HLB or to think that the tree has the disease. So, know your trees and their history. Was there a freeze this winter? Know the effects and symptoms of drought and monitor soils and trees for water stress. Check for bud mite. It also takes time from the point of infected Asian Citrus Psyllid invasion to the time when symptoms of HLB start showing up in the tree. So keep your eyes open, but don't assume the worse at this point.
More on Tristeza:
Misshaped fruit from Stubborn
Discolored seeds from Stubborn
Reduced canopy size from Stubborn