March Orchard Management Considerations

It is finally looking a little bit like spring outside! Almond bloom is winding down, prune bloom will be picking up, and there are even some tasks the walnut growers can do to stay on top of things. Long term forecasts still predict some wet patterns moving through in March, so if you have standing water in your orchard, refer to DPR’s exemption for certain fungicide applications to evaluate your options. Below are some orchard tasks to keep in mind for almonds, prunes, and walnuts.

All Crops: 

Almonds: 

  • As bloom winds down, make sure you maintain communication with your beekeepers so bees can be removed in a timely fashion. Be mindful of spray practices – just because your trees are no longer blooming doesn’t mean bees aren’t still foraging in the area.
  • Start planning your nitrogen budget for the upcoming season. An initial estimate of nitrogen needs can be based on an average crop year for your almond block. Nitrogen management tools based on UC research can help your planning. Approximately 20% of the year’s predicted nitrogen needs should be applied in late February or March.
  • San Jose Scale (SJS) traps should be hung by now (late February). Crawler treatments with OPs should be timed approximately 600-700 degree days (DD) after the biofix (male flight); treatments with IGRs should be timed closer to 400 DD from the biofix.
  • Navel orangeworm egg trap.

    Navel orangeworm egg trap.

    Hang navel orangeworm (NOW) egg traps, and peach twig borer (PTB) pheromone traps by March 15.

  • If scab or rust was a problem last year (rust was an issue for many growers), monitoring should begin about two weeks after petal fall. Overwintering scab twig lesions typically begin to sporulate in April. If subsequent rain is expected, initiate control.
  • If shot-hole fruiting bodies were found in the orchard in fall 2016, select a fungicide with shot-hole activity for a petal fall 2017 application. If no fruiting bodies were found in the orchard last fall, there is no need to spray for shot-hole unless disease symptoms (fruiting bodies) are found on new leaves after bloom.
  • Extended wet, cool weather during full bloom into petal fall can lead to green fruit rot.  If a rainy pattern moves back through, select fungicide(s) for full bloom application that controls this problem (caused by up to three organisms). FRAC Group 3 fungicides do not provide good, consistent control of green fruit rot.

 

Prunes:

  • Your bees should already be ordered by now, so if they aren’t lined up now is the time. Generally, you want to install one hive per acre.
  • Check the uniformity of your irrigation system and perform maintenance before the system is needed for frost protection, orchard cooling at bloom, or the irrigation season starts.
  • Have your air-blast sprayer ready to apply bloom fungicides. Check calibration and do general maintenance (check sprayer filters, replace nozzles as needed, etc.)

    San Jose Scale (SJS) colony on old prune wood.

    San Jose Scale (SJS) colony on old prune wood.

  • If San Jose scale (SJS) dormant treatments were not applied, not effective, and/or SJS pressure is high, treatments targeting the late spring crawler stage can be effective. Pheromone traps need to be placed ASAP if not out already. Apply crawler treatments 600-700 degree days after biofix (defined as males caught on consecutive trap checks).
  • If it’s cold at bloom, a closely mowed orchard floor minimizes frost risk. A closely mowed orchard is warmer than one with tall weeds/cover crop. Freshly disked soil is the coldest.
  • If it’s hot at bloom, consider irrigating to wet the orchard floor, and as much as the first foot of soil. Evaporation of this water provides some small temperature reduction (usually just a degree (oF) or two). Run water when temperatures reach 70-75oF and shut off when they drop below those temperatures.
  • Plan for brown rot fungicide sprays if bloom weather is wet. In a wet bloom, two sprays (green bud and full bloom) are recommended. One spray at 40-50% bloom effectively controls brown rot in year with no rainfall, but there’s a risk of brown rot infection when wetness is from dew. Flowers are susceptible beginning at green bud. Alternate fungicide classes (FRAC numbers) if spraying more than once.

    Mealy plum aphid colony.

    Mealy plum aphid colony.

  • Russet scab develops when there is significant rainfall during and immediately after bloom. Consider spraying captan or chlorothanil (Bravo/Echo) at full bloom to reduce scab at harvest.
  • While we’re on the topic of bloom sprays, don’t forget about these tips for honey bee safety.
  • If aphid control measures were not taken during fall or winter, two oil sprays (4 gal/acre) at bloom can be effective against mealy plum aphids and leaf-curl plum aphids if applied 7-10 days apart at 1.5 mph. Oil should not be applied with or shortly before/after captan, chlorothalonil or sulfur because the combination can be phytotoxic.
  • Monitor for peach twig borer (PTB) during and after bloom. Chewing damage on buds during bloom indicates PTB activity and may warrant treatment.

 

Walnuts:

  • Check the uniformity of your irrigation system and perform maintenance before the irrigation season starts.
  • Codling moth traps should be put out in the next week or so to establish the first biofix. Check traps twice each week until biofix (moths found on consecutive trap check AND sunset temperatures above 62°F) and weekly thereafter. After biofix, begin accumulating degree days to track development and inform application timing(s) if population densities necessitate treatment. Many effective mating disruptants are available (aerosols, hand-applied, flowables) and are becoming more affordable due to improvements in formulations, release rates, and release intervals. If using mating disruption, hang or apply disruptants ahead of historical biofix in your orchard.

 

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