March 2015 Tasklist for Pistachios

By Bob Beede, U.C. Farm Advisor, Emeritus

Hoorah APG!
The American Pistachio Growers, with tremendous sponsor support from their processor members and allied industry, hit another grand slam with an outstanding annual conference full of valuable industry information and fun. The conference was standing room only with over 900 attendees. Congratulations to the entire APG staff for exceptional organization and execution. The Gala dinner at the Miramar Marine Air Station proved to be as patriotic as it was tasty. What a treat to visit with the young American men and women who keep us safe at night. We can quickly forget how dangerous a world we now live in. Watching night maneuvers in preparation for landing giant warships on carriers bobbing at sea serve as a good reminder. Standing inside a Fighter Town Hornet hanger certainly made the National Anthem sung by the talented and beautiful Miss California extra meaningful.

The APG has grown from 351 members in 2008 to 627 members in 2014. The truly impressive aspect of this organization is its “collective heart.” Individual farmers and processors have joined together toward the common goal of telling the American Pistachio story to domestic and international customers. They have succeeded in sharing the health message of pistachio consumption; 67 percent of those randomly polled indicated an awareness of the nutritional benefits of pistachios. Combined with the efforts of Paramount Farms, pistachio sales will need to increase by about 14.5 percent annually to absorb the one billion pound crop anticipated by 2020.

Season Preview
The actual numbers vary by date of inquiry, but the bottom line is that we are bracing ourselves for yet another dry season. As of February 10, the statewide snowpack is only 25 percent of normal, down from 50 percent in December, due to warm temperatures in January. Unfortunately, the promising December storms were followed by a near-rainless January, which is historically our wettest month. December rains pounding the northern part of the state did little to replenish the depleted Central Valley reservoirs. However, they have allowed water transport into the San Luis Reservoir, which is critical for Westside growers. Insufficient rain means another year of heavy reliance upon groundwater, now at its lowest level in recorded history. This all adds up to the fact that everyone has to do what they can to optimize application rather than waste what a fellow farmer is in desperate need of. The risk of groundwater overdraft does not strike home until your pump starts throwing only a half pipe. Let’s hope and pray that more rain is on the way, even though it means a wet spring. Below is a table comparing the storage capacity for several key reservoirs as of February 19, 2015. Their current level is contrasted to the past two years, which shows we have about half as much stored water this season as we did in 2013.

Water Storage Comparison for 2015, 2014 and 2013, and the 15-year average
as of February 19 for each year. Storages listed as Millions of Acre-feet.

CVP Reservoir (Capacities) 2015 Percent of 15-Year Average 2014 Percent of 15-Year Average 2013 Percent of 15-Year Average
Shasta (4.552) 2.546 78 1.659 56 3.424 112
New Melones (2.420) 0.604 42 1.047 67 1.624 100
Don Pedro (2.03) 0.865 61 1.054 74 1.399 98
Folsom (0.977) 0.552 104 0.286 54 0.557 112
Millerton (0.520) 0.191 56 0.206 70 0.303 98
San Luis Reservoir (0.966) 1.249 74 0.335 46 0.709 94
Pine Flat (1.0) 0.152 30 0.184 36 0.316 62

These numbers illustrate how dependent we have become on annual rainfall, and how rapidly our present storage capacity is depleted by an increasingly thirsty California when it does not rain!

In preparation for years such as this, the California pistachio industry initiated water research 25 years ago. Led by Dr. David Goldhamer, UC Extension Specialist, we studied season-long irrigation at 0, 25, 50, 75, and 100 percent ETc, as well as temporary reductions from full ETc at the three main stages of pistachio development: bud break to shell hardening (Stage I); late-May to late-June, when neither shell or kernel growth is occurring (Stage II); and late-June to harvest when kernel growth and shell splitting takes place (Stage III). We refer to these carefully managed reductions in water application as Regulated Deficit Irrigation (RDI).

From these trials, we learned that pistachio, unlike almond, will tolerate a season of little to no water. In fact, the trees that received only rainfall water were still alive and sparsely foliated after THREE years of dryland farming! The trees extracted about 3.5 inches of water per season measured in the top 20 feet of the profile. Almond trees would not survive these conditions nor extract water from such depths. Now, it would take a couple years to rebuild the fruiting structure on these trees, but at least they survived and you did not lose your principal. This experiment was done at Kettleman Pistachio Growers in cooperation with Donnie Rose. The soils are high quality there, so salinity was not a factor in this experiment.

Equally important to survival, under extreme water deficits, is the response of pistachio to RDI, by which as much as a foot of water can be conserved with little short-term implications to crop quantity or quality. Table 1 provides a brief summary of the impacts of water stress at the different stages of crop development. I know many of you are not fans of RDI because of the difficulty in replenishing soil water content in time to meet the high water demands of Stage III. However, many growers now have no choice, and some will only have enough water this season to keep trees alive, let alone make a crop. Understanding and sharing the RDI data with your pistachio neighbors is also beneficial to preserving the remaining groundwater in your area. Quite honestly, I see the need for a little more “collective heart” mentality in farming neighborhoods when I see orchards full of water consuming weeds and cover crops. Water is at a historic low, folks!

Dr. Goldhamer’s team research suggests that 7-10 inches of water can be saved with RDI with no impact on fruit yield or quality; either for this or subsequent seasons. This can be accomplished by irrigating at 50 percent percent of potential ETc from mid-May through late-June (Stage II). This is after the attainment of full shell size and before rapid growth of the kernel.

Growers needing to reduce water use by MORE than 7-10 inches must stress the trees more severely during other times of the season. This will reduce yields of marketable product due to smaller nuts, less crop load, less splitting, and more split nuts left in the tree after shaking. These more severe RDI regimes are built on the principle that from early-July through harvest, the trees are most sensitive to stress.

To reduce seasonal ETc by 16-20 inches, irrigate at 50 percent percent ETc through mid-May, then 25 percent percent through early-July, 100 percent percent from July through harvest, and 25 percentpercent ETc postharvest. Additional RDI strategies to save even more water are shown in Table 2. As you can see from the table, as much water as possible is retained for Stage III, the most water sensitive stage of crop development. Reductions in shell splitting, increased blank nut production, and greater difficulty in crop removal will be proportional to the percentage of full ETc applied during this critical period. RDI is also highly DEPENDENT upon being able to refill the effective root zone to field capacity BEFORE the beginning of kernel expansion in late-June (shown in Fig. 1).

Regulated Deficit Irrigation is not for everyone. Reduction in applied water greater than 7-10 inches does reduce shoot growth and nut size, and above average irrigation skill is required to properly execute this “controlled plant stress.” However, if you do not have enough water, then ya gotta FIGURE IT OUT!

Table 1. Impacts of SEVERE water stress during the growth stages of pistachio.

Table 2. Regulated deficit irrigation schedules to minimize the effect of applied water in amounts less than full ETc.

Figure 1. Onset of pistachio kernel expansion in late June, Stage III

Chilling Update
I have written about this extensively in the last two newsletters, so refer to them to get caught up to this month’s comments. Dr. Katherine Pope, UC Farm Advisor, Yolo County, suggests that 58-60 chill portions are needed to completely satisfy the Kerman pistachio rest requirement, using the dynamic model, which considers negating warm daytime temperatures. Depending upon your location, the automated weather stations suggest that 52-60 chill portions have been received. Growing regions north of Merced generally appear to have greater chill portions that the southern region. However, Woodland, just east of Davis, reports only 55 chill portions. This anomaly reinforces the need for a simple weather station on every ranch. From the phone calls I received, my guess is that a high number of growers applied dormant oil to assist in rest satisfaction this season. My impression is also that growers have gotten the message about how important it is to properly apply the oil at no faster than 2 mph. I have committed myself to visit several locations in Kern County with Carl Fanucchi to gage the impact of oil treatment under various timings and chill portions. I will report what we see in upcoming task lists. Warm weather at bud break can partially overcome marginally insufficient chilling. Growers should also be sure to have some moisture in the root zone prior to bud break. This, in my opinion, aids the tree in initiating bud break under marginal rest conditions, because water availability is another trigger for the promotion of growth.

What should I be doing now?
Most importantly, you have to finish pruning, and then get the brush shredded so you can access the orchard and treat the weeds that escaped your pre-emergent treatment. I can tell you from experience that treating SMALL weeds is SO much faster and effective than letting it go until the jack rabbits are hopping around on Pogo sticks! The herbicide rig travels faster, the water volume used per acre is lower, and the kill percentage is so much more satisfying than dealing with 18-24 inch tall vegetation. Tall weeds also consume a lot of water, a precious commodity this season. You have to eventually spray them anyway, so why not kick yourself in the tush and do it now? One added motivation is that gophers feed on these weeds, and they do serious damage to young pistachios. By serious, I mean They kill pistachios--sometimes up to four or five trees in a row. I visited one ranch where voles coming out of the cover crop killed ten acres of trees! OK, the pistachio crop cop has given you a warning!

Now is also an excellent time to perform some bud monitoring for Botryosphaeria. As you walk through the orchard, collect at least one hundred female flower buds and place them in a paper or plastic bag. During your collection, take a stick with you and hit the persisting fruiting rachises on the tree to see if they knock off cleanly at their base, or if a stub is left. If the latter, you had better pull that fruit limb down, or cut if off, and cut into the wood around the base of the rachis to check for black streaks. Discovery of these symptoms suggests that rachis was infected with BOT this past season. Cutting the collected buds in half with a razor blade will help you determine how much BOT is present in the orchard. Buds black inside are often BOT infected, so if you find several in your first sample, you might want to sample one or two more times to get a better average infection level. Yes, I know this is time consuming and boring, but BOT is nothing to mess around with. Infected wood emits inoculum for SIX YEARS, and if you do not get control of it in drier years, it will cause you MAJOR economic loss in wet years. You know what they say about an ounce of prevention? Practice it! While you are out collecting buds, you will also most likely to encounter a bunch of other things needing attention, so feet in the field is good. Be on the lookout for cotton-like masses on the main trunks, which is OLD Gills mealybug activity. Show your workers what this looks like so they can report how much of it they see during pruning and irrigation system maintenance. You should also keep an eye out for soft scale adults on the one- and two-year-old wood. If you find a substantial number, you still have time to treat, but you need to move quickly. Go to the UCIPM Pistachio Web site and read up on your options.

The dry winter demands irrigation prior to bud push for early root growth and hydration of the tree. If salinity is an issue, you still have time to apply high-quality water for leaching. If you have not done it already, get some water in the ground, even if it means delaying shredding of the brush.

Take your crop consultant to lunch and discuss what went well last year, and what needs improvement. The biggest complaint I hear from consultants is that growers spray 7 to 14 days after they write them a recommendation. How do you expect to have clean product if you are responding so slowly to your PCA’s advice? Have you recalibrated your sprayers yet? Want better coverage? Add a second bank of nozzles, based on Dr. Joel Siegel’s coverage research. Also practice the 2 mph Dibble Rule. And switch out your old extended range herbicide nozzles for the new, improved TuboJets. Kurt Hembree, UC Farm Advisor, Fresno County, highly recommends them. Check out his website at: cefresno.ucanr.edu.

It may not be too late for a delayed dormant zinc (Zn) application. Zinc sulfate 36 percent at rates up to 40 lbs. product per acre or 5 gallons of 12 percent liquid zinc per acre can be safely applied up to the early green tip stage (1/4 inch terminal growth). Do not apply if flower buds are expanding. Zinc is so immobile that early-season sprays may prevent deficiency in young shoots for only a month. Research just completed by Dr. Carol Lovatt and me, with Paramount Farming, suggests improved uptake of Zinc Sulfate and Boron when six pounds of L.B. urea are added to the bud swell spray solution and then acidified with citric acid powder to pH 4.5-5.5. Leaf expansion sprays (2 lbs. zinc sulfate per acre, 100 gpa at 50 percent leaf expansion) about the third week in April are the most effective timing for uptake and therefore require much less zinc than delayed dormant treatments. However, treatment at 50 percent leaf expansion will not supplement zinc during bloom when deficiency reduces fruit set. By the way, there is a REASON why this spray is timed at 50 percent leaf expansion! During this period, the cuticular waxes of the leaves have not yet fully developed, so the zinc gets absorbed into the plant tissue, rather than being bound in the wax. You may not need a delayed dormant zinc treatment if you are not in a zinc deficient-prone soil (pH > 8 and/or your soil series is a terrace soil such as the San Joaquin series). Annual application of zinc during the 50 percent leaf expansion period may, in some orchards, be a sufficient maintenance program. Do not get low in zinc. This micronutrient is critical to shoot growth and flower bud differentiation. Once deficient, it can be difficult to get enough zinc taken up into the pistachio tree to resume normal growth. This is especially true of young orchards. I typically find zinc deficiency in HALF the young orchards I visit in the spring. You can lose a year of growth trying to recover from a bad zinc deficiency. That means crop in the seventh year, not sixth.

If boron (B) was low in August (less than 120 ppm), application of a soluble B (e.g. 5 pounds of Solubor®, 20.5 percent B) in 100 gallons of spray solution per acre in early March (bud swell) is effective in supplying B to developing flowers and pollen for improved fruit set. Boron can also be applied post-bloom at 50 percent leaf expansion (LE). The LE rate is 3 pounds of Solubor in 100 gallons of water per acre. Solubor creates a strongly buffered solution of pH 8.2. If mixed with zinc and copper fertilizers, the tank mixture should be acidified to pH 4.5 to 5.5 with citric acid powder (not phosphoric acid, which precipitates zinc as phosphate) to maintain the uptake of zinc and copper by the pistachio leaf. The best long-term boron correction can be achieved from a combination of soil and foliar treatments applied as a yearly maintenance program. There are a number of boron fertilizer materials containing different amounts of actual B. Consult with your nutrition adviser about which one is best suited to your cultural program. Spring B applications during shoot extension are more effective in correcting current season deficiency than treatments in June or July. Boron is not readily translocated by the tree’s vascular system. Similar to other micronutrients, B is more available in lighter, slightly acidic (6.0-6.5) soil. Soils lighter in texture and low in buffering capacity require the addition of less boron for correction. Applications through drip systems may be reduced by 25-30 percent due to higher efficiency from concentrated treatment. I have had to apply two and sometimes three ounces of Solubor PER TREE to correct deficiency in young trees. That’s 17-25 POUNDS of Solubor per acre. Boron and zinc are equally common deficiencies in young trees. If you let them get deficient, it can take a MONTH or more to get them growing again.

Did you know Nitrogen is becoming a dirty word? That is because the State believes agriculture is applying excessive amounts, and when they ask farmers to show them their method for budgeting nitrogen applications, they cannot comply. Not completing the good agricultural practices survey will come back to haunt you with added regulations on nitrogen management. Remember the “four R’s”: Apply the Right Rate (match demand with supply); apply at the Right Time (apply when the trees are active, and focus most of your N application on kernel filling, when N is in greatest demand); apply in the Right Place (ensure delivery to the active roots, and do what you can to manage variability across the orchard); and use the Right Source (understand the leaching and decomposition characteristics of the N you select). Secondly, remember how much actual nitrogen, potassium and phosphorous are consumed per 1,000 pounds of dry (CPC) weight; 28, 25, and 3, respectively. Hence, a 4,000-pound pistachio crop is only consuming about 112 pounds of actual N per acre, plus another 25 pounds for tree growth. Occasional soil sampling to determine your nitrate nitrogen levels in the root zone will also help guide you in balancing your nitrogen applications. Present thought suggests 10-15ppm nitrate nitrogen is a reasonable number, and 25-30ppm is high. I strongly suggest you sample to see what levels you have both in your soil, and in your water source. A 10ppm nitrate nitrogen level in your water equals 27 pounds of actual N applied per acre-foot!

Crop Quality for 2015?
If growers want to maintain the critical overseas markets, they must commit themselves to the industry goal of producing a high-quality, safe product. Navel orangeworm, aflatoxin, and food safety should be ever-present on your minds. Where does quality begin? AT THE FARM! Commit yourself to this, and keep the pistachio demand high. Crop size for 2015 is anybody’s guess, given the challenges we face. We can still produce lots of clean, yummy pistachios to sell the consumer. We cannot have ANY grower, investor, or absentee landlord disconnecting from our industry’s commitment to quality. Please think of this when you consider ignoring your PCA’s pest management recommendations. Farmers and crop consultants will not want to miss the NOW management meeting scheduled for Tuesday, March 17, at the Tulare Ag-Expo Complex social hall. Both Brad Higbee and Dr. Joel Siegel will be offering their latest information on control of this pest. This meeting is sponsored by your California Pistachio Research Board. Happy Farming!