October 2016 - Pistachio Task List

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

Harvest Wrap up: By the time you read this, another hectic harvest will be in the bag, and you are now pouring over your grade sheets to assess the outcome of all your hard work. The word on the street is that at least 800 million pounds were brought to processors this season.

Early harvested nuts had navel orangeworm levels at one percent or less, and then it steadily rose, just like we have told you for decades, to reach an average of 2.6 percent on September 26. One factor that may have contributed to the NOW problem is malfunctioning pheromone-confusion dispensers. Apparently, changes in the propellant resulted in varnishing of the nozzle and reduced pheromone emission. This is not the case with all dispensers in all orchards, so please do not make this statement the universal reason for your insect damage. It is, however, something you should investigate if mating disruption was not as effective this year. I still believe mating disruption is our future, just like winter sanitation is the cornerstone for a sound NOW management program.

I cannot bring myself to discuss navel orangeworm one more time in this month’s task list. I feel like no one wants to listen anymore. Readers wishing to revisit this subject can review last month’s task list, and every one prior to it. Managing NOW is a PROCESS, NOT AN EVENT! You cannot get behind. If the industry averaged 2 percent NOW this season, it would mean that 16,000,000 pounds would be thrown away! Obviously, processors are not going to eat that financially, so it will come out of your paycheck.

October is a good month to sample the nuts left in the tree to see how infested they are. These nuts are the beginning of the overwintering population. Shaking them onto the ground early, to enhance their degradation, will reduce NOW survival. October foliar treatments have also reduced their survival. October is also a good time to look for Gills mealybug, which is typically treated in mid-June.

There were lots of orchards with low split percentages this season. Although I reviewed factors affecting split percentages last month, I will repeat them this month, since it is now a hot discussion topic. Research by Vito Polito, U.C. Davis Plant Sciences Department, indicates shell splitting is caused by the physical expansion of the kernel rather than development of an abscission zone. Split nut percentages are affected by all of the following: low boron and zinc, insufficient water from July 1 to harvest, excessive cool weather during the growing season, time of bloom, and heavy big bug damage during kernel filling when nuts show no symptoms. Growers with poor split percentages need to examine their irrigation program during stages 1 (shell development) and 3 (kernel filling).

Research by Dr. David Goldhamer shows that split percentages can be improved by inducing regulated plant stress during Stage 1. If you typically have good split percentages, the gain from Stage 1 stress is primarily water savings. There is no question water stress during Stage 3 reduces split percentages. Compare your applied water to the following average water use: July is 9.8 inches, August is 8.3 and the first two weeks in September is 2.8 inches. It is highly possible, especially on high saline soils, that you are applying the correct amount of water, BUT it is not infiltrating! I found lots of orchards dry at 24 inches in July due to this. So, remember there are TWO periods in which to apply gypsum, and EACH ONE is for a different reason! Apply gypsum in the fall and early winter if you need to leach sodium from your root zone. Adequate low-salt water must also be applied to displace and leach the sodium. Apply gypsum in June when the soil begins to “tighten up” and the addition of free calcium increases pore size and water intake.

In addition to inadequate nutrition (zinc and boron), it is my professional opinion that the time of bloom and pollination affect split percentages at harvest. In high chill years, pistachio trees have the potential of pushing and blooming early, PROVIDING the weather is favorable. When spring temperatures are warm, bloom occurs early and sharply. This, in my opinion, allows for more uniform nut development and size since they all begin at about the same time. But when spring temperatures are cool and erratic, I believe nut size and expansion reflects this. Consequently, some nuts pollinate late and experience different developmental weather than those setting earlier

Young Trees: Budding in young trees usually stops by about September 10. Forcing fall buds greatly increases the risk of frost damage by depleting stored food spent on new growth. This potentially deadly practice is becoming more common with Golden and Lost Hills buds because they require a slightly bigger rootstock diameter to accept the larger bud shield than Kerman. Hence, trees are being budded later, and the temptation is to “beat the odds” and push them late into the fall. Instead, after the buds take, begin slowing vegetative growth by cutting back on the water. How you decide to handle your newly budded trees is your call, but the number of young orchards suffering from fall cold damage has increased markedly in recent years because the trees are being pushed too late.

Most growers observe an early- to mid-September irrigation cut-off on first- and second-year trees to harden them off. Timing the irrigation cut-off requires knowledge of soil water content, plant vigor, and estimated remaining growing time. It is better to stop them too early than force them too late! September and October is not the time to try and make up for growth lost during the season! It is much safer and smarter to get them to bed alive and then start off with good vigor next spring. Dr. “Z,” our new crop physiology professor at UCD, now has data to SHOW that cutting off the water to young pistachios DOES precondition the trees and make them more cold tolerant. Carl Fanucchi has been telling you this for years, but only wise men listen!

I still recommend growers assist young trees into dormancy with zinc sulfate 36 percent at 40 pounds per 100 gallons of water or 10-15 gallons of liquid zinc; 12 percent in 85 to 90 gallons of water. Liquid 12 percent is manufactured from zinc sulfate dissolved in sulfuric acid. Consequently, it has an acidic pH, which I think does a better job than 36 percent powder. But alas, no data, just opinion! Check with your crop consultant or other experienced growers for their thoughts. Also, I have seen more boron deficiency this year than in the past, so be sure to review your August tissue levels so that you could add some boron to your fall herbicide spray if needed.

In Memorial: I am very sad to announce the loss of Robert “Bob” Petersen on September 15. Bob was one of our pistachio godfathers, and was responsible for development of the budding and the open-vase training system, our industry standard. In addition to being an avid horticulturist, Bob was on the debate, basketball, track and swim teams at Chico High School. He also served as editor of its yearbook. After graduating from Cal Poly San Luis Obispo with an Ag Science Degree, he served his country during the Korean War in the Navy. In 1949, he joined his brothers Fred and Jim as the third generation of Petersen Nursery, Inc., and together they planted their first 20-acre experimental pistachio orchard in Durham, California.

In 1969, Bob formed his own nursery business. Corky Andersen and Ken Puryear introduced him to Leland McCarthy, one of the original Westside farming giants. Leland wanted to plant pistachios in a big way at his Dudley Ridge Ranch south of Kettleman City, and Corky referred him to Bob because of his horticultural expertise and early experiences with this new tree. Thus began the “Westside Pistachio Gold Rush,” with Corky and Ken growing atlantica rootstock, and Bob directing its planting, budding, and tree training. Since there was no one but them, Bob applied his expertise in budding camellias to pistachios. His first budding crew was the Chico High School football team, who Bob personally told me “were the only guys tough enough to work all day out on the westside and follow my instructions.”

Included in this band of brothers were Bob’s two sons, Dave and Steve Petersen, as well as Bill Seaman, and Chris and Craig Wylie. These guys budded trees all day, and then went to Kettleman for a shower and a bed when Kettleman had only one motel and restaurant. Bob was a dad to all of them, and each went on to very successful careers in our industry. They each have their own crazy story to tell of the budding days with Bob.

Bob Petersen was a master at tree training, and he had very specific rules that were to be followed to the letter if you did not want him barking at you. Those wanting to learn were given a good measure of patience. Those wishing to “modify the system” were given the boot! Bob is easily credited with developing over 100,000 acres of our industry personally, and if you include the acreage developed by his sons and protégés, it is at least double that amount!

Bob was a very humble fellow and never wanted center stage. Chris Wylie and I tried several times to do an oral history with him, but he did not think his contribution justified it. Giving Bob the attention he so deserved actually embarrassed him, and thus you felt badly about trying to honor him! I am a better person and horticulturist for having known Mr. Petersen, and I take every opportunity to hang out with the “budding boys” to gather as much “Bob knowledge” as I can. This task list and the successful season I have had helping all of you is dedicated to Bob Petersen, the godfather of pistachio budding and tree training, and a wonderful mentor to many!

That’s all, folks. Happy Farming!