Orchard Tips from Pistachio Bob

APG is proud to announce a new Pistachio Tasks series from U.C. Farm Advisor Emeritus (retired), Bob Beede. Bob has condensed his monthly pistachio tasks into bulleted tasks/activities that you, as a grower, should be focused on in your pistachio orchard. We hope this information will get you thinking (if you aren’t already) about how to make your pistachio orchard even more productive!

December Tips

  • Complete winter sanitation
  • Assess the quality of chill accumulation. Consider the application of a kaolin- or calcium-carbonate-based “chill enhancement” product to reduce flower bud temperatures. Preliminary studies indicate such products can reduce flower bud temperatures by as much as 10 degrees F. The significance of this reduction depends on the duration and degree to which ambient temperatures exceed the traditionally accepted chill threshold of 45 degrees F. Preliminary studies suggest these chill-enhancement products can increase the effective chill portions by 10 percent. Achieving this level of improvement may require up to three applications at about $70 each. Reapply after major rain events during the two most important months for chill accumulation: December and January.
  • Have the pruning crew lookout for overwintering Gills mealybug (white cottonlike masses) on the main scaffolds. Also, look for soft scale on the one-year-old fruitwood. Go to the UCIPM Pistachio website to learn about their biology and view lifecycle photos.
  • Survey the orchard for blackened old cluster remnants that do not pop off when struck with a stick. These could be Botryospheria infections. Examine limbs up to six years in age for sunken areas. Cut into them to determine if dark tissue is revealed. These are holdover cankers of Botryospheria. Further assessment should be made to determine their prevalence; remove as many of them as practically possible during pruning. Prune two inches beyond the infection margin.
  • Orchards with rising Botryospheria should perform BUDMON sampling. This detects bud infections and predicts the risk for in-season panicle and shoot blight. Instructions can be found on the UCIPM website.
  • Collect mummy nuts left from harvest and assess them for navel orangeworm. This will hopefully motivate you into additional winter sanitation. Destroy the mummies removed from the tree, berm, and tree crotches by mowing or disking.
  • Assess your vertebrate populations and prepare to initiate ground squirrel management in early January.
  • Remove old cartons on second-year plantings. Replace broken stakes. Ensure that the trees are tied BELOW the primary branches to the stake.
  • Pay a visit to the nursery that provides your trees to plant, in the spring, to ensure that the planting material is what you were expecting. Confirm with the nursery which plants they will be delivering. Arrange for tentative delivery date.
  • Perform winter weed management as needed. Eliminate weeds around young trees to prevent voles from feeding in secrecy at the trunk base.
  • Review last year’s pest management program with your crop consultant. Place your order for navel orangeworm mating disruption dispensers.

January Tips

  • As of early December, it has been a very dry winter. It is essential to assess your soil moisture and irrigate if dry. By January, you should have good soil moisture to a depth of three feet. The definition of “good moisture” is dependent upon your soil texture; sandy loam to loam soils should make a ball when squeezed in your hand and then bounced. Clay loam to clay soils, with good moisture, will “ribbon” if you roll it between your index finger and thumb. When these heavy textured soils get too wet, they feel slimy when handled. To assist you in an accurate water-content assessment of the different textured soils, download the file “Irrigation Scheduling for Walnuts-UCANR,” found at cekings.ucanr.edu/files/19006.pdf online. Appendices 1 and 2, at the end of this manuscript, provide U.S. Geological Soil Survey guidelines to estimate the ranges in water content for varying soil texture using the “feel method.” Field observations and limited UC research suggest deciduous trees, with adequate winter soil moisture, respond to chill portions more effectively than dry trees.
  • It still is not too late to install a weather station in your orchard! Access to accurate winter temperature data is becoming more important with the warmer winters. Monitoring temperatures from bud break to shell hardening can also assist you in predicting harvest dates. This data is also highly valuable in supporting a crop insurance claim.
  • January is also not too late to initiate a leaching program for soils that have rising sodium, chloride, or boron levels. The efficacy of a leaching program depends entirely on having water quality that is lower in salinity than your soil. Should you need to leach, now is the time to do it. You should have performed detailed soil sampling in the fall and had a current water quality analysis to design the most successful program. Leaching involves saturating the root zone soil and then applying incremental amounts of additional water to push the accumulated salts past the upper three- or four feet of soil, with the water moving vertically through the profile. I highly recommend you work with an adviser, who is knowledgeable in soils and water, to assess the need for leaching and develop a successful plan of action. Leaching usually involves the addition of amendments designed to increase the available calcium concentration for the displacement of sodium. Rising sodium levels in loam and clay loam soils are especially problematic because they render the soil moisture less available for plant use and limit canopy expansion due to excessive stress.
  • Those weather stations that I have squawked about for years may now be telling you that December was low in chilling. If this is the case, read the December Orchard Tips about the use of “rest enhancement” foliar sprays, which have been documented to reduce flower bud temperatures by 100F. The value of this temperature reduction is theoretically dependent upon how elevated the ambient temperatures are above 450F, which is the traditional threshold for chill accumulation. It is generally agreed that any reduction in flower bud temperature, during warm winters, has some benefit because it reduces the respiration rate of the plant and helps conserve the stored carbohydrates needed for initial bud break and bloom. Review the comments from last month if you need additional information. You can also read a detailed article in the December TASK LIST I published in Pacific Nut Producer Magazine.
  • As of December 12, 2020, it has been unseasonably dry. This has allowed winter mummy shaking and pruning crews to stay on schedule, but many growers have wisely held off applying pre-emergent herbicides that require at least a quarter-inch of rainfall to incorporate. If you are one of those waiting to treat, be sure to have your materials, recommendation, and equipment ready to go, should significant rainfall be forecast. The UC weed scientists say the pre-emergent spray saves money over multiple contact treatments. We are also experiencing more regulations with some of our best post-emergent materials, such as Gramoxone and glyphosate. This makes a post-emergent weed control program more difficult and expensive.
  • Due to the earlier leaf-out date for Golden Hills and Randy, it is recommended that pruning these varieties should be completed by about mid-January. Delaying pruning has resulted in poor leaf out, which has not been associated with inadequate chilling.
  • As mentioned last month, be on the lookout for Botryosphaeria (BOT) during pruning. Evidence of infection is blackened fruit rachises that do not separate cleanly at their base from the branch when hit with a stick. Rachises, whose basal section resists, removal should be inspected for necrotic (blackish) colored tissue beneath the bark that extends longitudinally from the base of the fruit scar. Finding such rachises is cause for greater inspection for dead, blackened fruit buds and sunken areas on limbs two years and older. More information about BOT and its management can be found on the pistachio UCIPM website.
  • Only those growers without any history of navel orangeworm (NOW) should be foregoing the use of Mating Disruption (MD). I know this is “tough talk,” but MD and NOW management is a COMMUNITY EFFORT! The more we can do to suppress the population by winter sanitation and regional MD, the better chance we have of reducing insecticide sprays and delivering pistachios that earn the twenty-cent or greater premium! So, sign up for MD this month while the MD supplies last!
  • Pray for rain! Happy Farming!