may-jun-2019

IN YOUR ORCHARD TIME TO CONSIDER With late bloom and cool spring temperatures, hull split looks like it could be later than average, pushing back timings for critical practices to bringing in a high quality crop. Tracking nut development and monitoring pest and beneficial insect/mite levels in individual orchards will help time practices to deliver the best possible quality crop. Irrigation Maintaining good orchard moisture status through kernel fill is vital to steady crop development while reducing the risk of mite flareups (where abamectin hasn’t been carefully used early). How can you tell if an orchard has “good moisture status” ? Pressure chamber readings in well-irrigated orchards should run between -9 and -11 bars when daytime orchard weather reaches 100 to 105 degrees Fahrenheit with 20 to 30 percent relative humidity levels. Information on pressure bomb use in almonds is available, free, from: anrcatalog.ucanr.edu/pdf/8503.pdf. Once kernel fill has completed, research and experience has shown that a little targeted stress – a known level for a short time – can be helpful. Moderate water stress (targeting -15 bars in a -14 to -18 bars stem water potential window) beginning at the initiation of hull split and running for approximately two weeks reduces hull rot and can produce more uniform timing of hull split within trees and orchards. Once the two weeks of moderate stress have passed, return to full irrigation until harvest cut off. This practice is referred to as Strategic Deficit Irrigation (SDI). To arrive at moderate water stress by the very initiation of hull split, reduced watering (shorter timing for each irrigation, NOT fewer irrigations) should begin weeks before. In heavier soils under sprinkler irrigation, that could mean four to five weeks before the very beginning of hull split, while it could be just a couple of weeks ahead of that timing on sandier soils with drip irrigation. Track orchard water status with the pressure chamber and adjust irrigation set length as needed to make sure that the intended stress is reached by the initiation of hull splitting, but no more than the -14 to -18 bars target window. If you can keep pressure chamber readings above -18 bars and all other orchard factors are “in the green,” yield will not be impacted. If you have the ability to irrigate different varieties differently, apply this targeted water deficit to Nonpareil first, then the pollinizer(s) as they reach kernel fill and approach the start of hull split. Why go to all this trouble ? There are at least three good reasons. 1) Moderate water stress significantly reduces hull rot. Along with careful nitrogen fertilization and carefully timed and sprayed fungicides, this is the way to most effectively control hull rot. Hull rot reduces current and future cropping and means more winter sanitation work as infected nuts don’t shake off. 2) Tighter hull split window (time from first splitting nut to 100 percent split) could mean shaving time (a day or two) off shake timing, helping reduce navel orangeworm (NOW) damage. Can a day or two of advanced shake really make a difference in NOW damage ? Yes, under high NOW pressure with insecticide coverage running out, worm damage can increase by half to two percent per day. 3) Water savings of up to four acre-inches have been measured in field research using SDI at hull split. Navel Orangeworm At this point of the season, careful insecticide application(s) and timely harvest are the primary tools to minimizing damage and income loss. Only after hull split begins can current crop almonds can be located by a navel orangeworm (NOW) female looking for a spot to lay her eggs. Early spray timing for newer, longer lasting insecticides (Altacor ® , Intepid ® , etc.) is recommended by researchers. Once blanks begin splitting on the orchard edges, the sound nuts in those edges should be just days behind. An edge spray – driving the sprayer around the orchard and spraying in with half the sprayer nozzles open – helps protect the those vulnerable nuts while the rest of the orchard progresses to hull split. Once blank nuts in the orchard are splitting, it’s time to spray the orchard. Getting across the orchard as quickly as possible is critical to 4 2 A L M O N D F A C T S