California agriculture experienced a nearly three percent increase in the sales value of its products in 2012. The state's 80,500 farms and ranches received a record $44.7 billion for their output last year, up from $43.3 billion in 2011 and $37.9 billion during 2010. California remained the number one state in cash farm receipts with 11.3 percent of the US total. The state accounted for 15 percent of national receipts for crops and 7.1 percent of the US revenue for livestock and livestock products. Exports totaled $18.18 billion in value which represents an eight percent increase over the previous year.
California's agricultural abundance includes more than 400 commodities. The state produces nearly half of US-grown fruits, nuts and vegetables. Across the nation, US consumers regularly purchase several crops produced solely in California.
California's top-ten valued commodities for 2012 are:
- Milk — $6.9 billion
- Grapes — $4.449 billion
- Almonds — $4.347 billion
- Nursery plants — $3.543 billion
- Cattle, Calves — $3.299 billion
- Strawberries — $1.939 billion
- Lettuce — $1.448 billion
- Walnuts — $1.349 billion
- Hay — $1.237 billion
- Tomatoes — $1.170 billion
Please see complete statistics for 2012, reproduced as PDF files below, or use the link in the right column to access this report and others on the NASS website.
I recently went out to an avocado orchard on sandy soil that had had sudden leaf drop after a Santa Ana condition. The problem is that the orchard had had an ongoing leaf blight problem that had been accentuated by two years of drought and with the Santa Ana more pressure had been put on the trees. This is a condition that has become more and more pronounced over the year and with little rainfall is going to be something to watch out for this coming irrigation season.
Stem and leaf blights are symptoms that appear for various reasons – high rainfall or humidity, spray burn, chewing insect infestation. Here in California we can add other causes, such as drought and salinity burn. These conditions can cause wounding of leaf and stems allowing entry of fungal spores that can cause leaf and stem dieback. This condition is most common near the coast where weather conditions can change from mild and low temperatures to extremely high temperature with winds, such as the Santa Anas or the Sundowners in Santa Barbara. Leaves suddenly dry out, causing cracking either at that time or when they are rehydrated with irrigation. This allows spore entry into the wounds and permits the pathogen to grow in the dead tissue. Symptoms appear 7 – 10 days after the stress. These are decay fungi that create these spores and they are the ones that cause decay of dead tissue on the ground. So their spores are everywhere.
The greater part of a tree is dead – the woody part of the branches and trunk. And it is dead tissue that these fungi are feeding on. Most trees will limit the growth of the fungus by sealing off the infection with gums of various sorts. In that case, the disease is limited and you may only see a leaf or small branch dying back. In mature trees it is possible to see a small branch here and there that has died back, but the bulk of the canopy is still green. It has been called “salt and pepper syndrome”, because of that speckled appearance. In the case of young trees with their smaller root systems and a lesser ability to seal of the disease process, a whole tree can die.
Since this is a severe water stress or salt stress induced problem, the most important management issue is to watch the weather forecasts predicting unusual hot, dry weather and make sure the trees are adequately irrigated going into the stressful period. Shallow rooted trees like avocados are more prone to dry out rapidly in these high water demand situations, but it can be occur in other trees (citrus, apple, peach) and shrubs if the weather conditions are severe enough. With poor leaching due to low rainfall, this can be more of a problem
The only solution to the symptoms is to cut out the diseased parts to prevent its further spread. Once the disease starts spreading, the fungus can produce copious amounts of spores, which in the case of avocado can cause cankers and rots on the fruit.
Some symptoms of leaf blight. Spots that progress into marginal necrosis can occur or just general necrosis.
The talk of drought and water restrictions in the State has created a time for serious decisions. What can be done with avocado citrus trees that have been invested with time and money when there are allocations of water? Although this article is addressed to subtropicals specifically, the guidelines are generally applicable to all fruit trees.
Irrigation systems and scheduling
One of the surest, although not necessarily the cheapest, ways of managing with a decreased amount of water is to improve its application and scheduling. Insure that equipment is working properly, that nozzles are not plugged or worn, that pressures in the irrigation blocks are uniform, that leaks are repaired, and that no runoff or deep percolation are occurring. Many Resource Conservation Districts have Mobile Labs that can help make a system evaluation.
In the Ventura area, oranges use about 30 inches of water per year, however , the monthly amount varies with weather. Applying water in the amounts and at times for optimum production can be improved by using tensiometers. A gauge reading near 40 centibars has been recommended for the one foot tensiometer. The three foot tensiometer can be used to determine the amount of moisture stored in the lower horizon and to determine whether the irrigation was effective, whether the irrigation water infiltrated down to that depth.
Whatever reading is used there is no substitute for observation of the trees themselves and the soil.. Use a soil sampler or shovel to verify the depth of water applied. If time clocks are being used, turn them off or at least adjust them frequently enough to accommodate changing weather patterns. Use of CIMIS weather data can aid in correcting schedules to changing weather.
If water applications need to be curtailed, there will be a decline in yield and fruit size. Applying something less than about 75% of tree requirement will give reduced yields not only for this year, but will lead to dieback and low yields for 3 -4 years after. Abandoning the trees altogether will also yield little or no crop and dieback, but the trees will often return to normal yields in 3 - 5 years. If little water is available, it may be best for commercial operators to reduce the number of trees irrigated to those that can receive 85% of their water requirement and abandon the rest, hoping for more water in future years.
Since it is the leaves that are the site of water loss , the best way to reduce water loss is to reduce the amount of leaves present. This is the ideal time to thin an orchard, get rid of those trees that are shading each other and reducing the per tree yield of fruit. This is a good time to topwork trees to better varieties, since the smaller trees will use less water. A good weed management program will reduce competition for water, and mulching the wetted area of the sprinkler will reduce evaporative loss from the soil surface. Once the leaf area is reduced, it is necessary to adjust the irrigations to reflect the decreased need for water.
This is an opportunity to identify the least productive trees in an orchard and cut of water to them. Trees with root rot or frost damage; trees growing on limy/iron chlorosis sites. Trees growing on ridges that receive the full force of the wind and have a lower yield per gallon of water should be considered first. Trees growing on the perimeter of an orchard also will transpire more water for a given amount of fruit. If all trees in the orchard look good, then these perimeter trees should be targets for saving water. If production records have been kept for different blocks of trees, it might be possible to identify low yielding areas that could be sacrificed.
This is an opportunity , as well. Many growers have kept poor producing parts of groves going because it is an emotional issue to cut up a tree. Seize the day and take advantage of the situation.
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I recently traveled to the Malaga area of Spain where there is quite a bit of new planting going on. The industry celebrated its industry in 2002 with the World Avocado Congress and we saw a considerable expansion of the industry then and more has occurred since then. More than 22,000 acres are in the ground. Much of the plantings are occurring on almond and olive ground which have become less profitable. Average grower acreage is similar to that of California's at about six acres per grower.
Production is along the southern coast of Andalucia and Valencia with some produced in the Canary Islands. Although a “Mediterranean” climate, it is both hotter and more humid on average than the California production area. Typically ‘Hass' is harvested two months earlier there than here. Scarcity of water in some areas, although in the Malaga area there are a series of dams and water is not limiting. Labor cost and availability are similar to that in California. Also, unlike California, the fruit snap harvested and any stems remaining are clipped at the packing house. This more efficient harvest system is also used in Australia. A discussion of the method is described in the November 2002, AvoResearch Vol 2, Issue 2.
The industry produces 150 M pounds, the bulk of which goes to France and Germany where they are willing to pay good prices for quality fruit. It is a short drive to Paris and Berlin and fruit arrives in good condition. The bulk of this export market is in France and three export companies dominate this export. Per capita consumption in Spain is only about one pound per year, 3.5 pounds in France and now the US is about 4.5 pounds.
There are over 12 nurseries supplying trees to the industry, but three dominate. As here, growers are looking at high density plantings at as close as six feet apart, in row. They are using the standard varieties , such as ‘Reed', ‘Lamb Hass', ‘Fuerte', ‘Zutano', ‘Bacon', ‘Pinkerton' and ‘Hass', but they are looking at newer varieties, such as ‘Carmen' and ‘Mendez'. There is still a good market for greenskins. They also have several rootstocks that we don't have, such as ‘Atkinson' used in calcareous soil and ‘Albaida' used in situations of Rosellinia fungus. This is a fungus similar to oak root fungus which they don't have as much as we do. Recently a long term trial was initiated evaluating over 10 scion varieties on five rootstocks, including ‘Dusa' which is one of the most popular rootstocks now.
There is Phytophthora root rot there, but it is not as extensive as in our industry. They also don't seem to have much of a problem with black streak, leaf blight, bacterial canker, and stem blight. These are diseases associated with poor water management and poor water quality. Some of the water quality reports I saw were really quite good compared to many of our waters. They do have a problem with Persea Mite which arrived there in 2005. It still is not under good biological control, but I saw an organic orchard that didn't spray, and the damage was acceptable. So something is finally kicking in.
Phytophthora disease control is done as here with mulches and phosphonates. One of the major sources of mulch was shells from the almond industry. With the eclipse of the almond industry, the shells have become very expensive and are going into other products. They are developing a yardwaste collection system, but it is not as close to the avocado orchards as to make it a cheap source.
The latest (2012) Department of Agriculture reports on county agricultural production can be found at