Soil moisture sensors are great tools to aid in irrigation management. They provide feedback on the movement and depth of moisture within the soil, providing the ability to identify the proper duration of irrigation. Proper use relies on a thorough understanding of the soil characteristics of the orchard, which include soil type, water holding capacity, and salinity level.

     Sensors can be used to help schedule irrigation. Timing of irrigation usually occurs when moisture levels drop below certain trigger points at varying depths. These points are different for every soil and sensor type and require in-field calibration to help reduce unwanted plant stress. Calibration can occur by comparing sensors readings to plant stress responses (e.g. Pressure chamber readings) or to a “feel” test to determine how much water is still available to the plant.

Glufosinate drift can cause trunk damage to young almond trees. Photo courtesy of Brad Hanson, UCCE Weed SpecialistGlufosinate drift can cause trunk damage to young almond trees. Photo courtesy of Brad Hanson, UCCE Weed Specialist

     Glufosinate (Rely 280 and other trade names) usage has increased over the past year due to the increase supply and availability of generics. This herbicide has been shown to be very effective in controlling glyphosate resistant weeds, including fleabane, marestail, and goosegrass and has an important role in orchard weed control.

Gumming of the tree trunk caused by experimental glufosinate application. Photo courtesy of Brad Hanson.Gumming of the tree trunk caused by experimental glufosinate application. Photo courtesy of Brad Hanson.

     One concern of glufosinate usage is plant safety. Accidental applications of glufosinate to the trunk of one to three year old almond trees can cause damage. Field observations and studies by Brad Hanson (UC Weed Specialist) have shown that gumming and a sunken canker can occur three to four weeks post herbicide application. This canker is distinctively different from Phytophthora, band canker, and bacterial canker as there is more consistency of symptoms across the field (i.e. a pattern in symptom occurrence). Within affected trees, symptoms include origination of the irregular shaped canker being above the soil line and in a similar location on multiple trees, the lack of a “sweet” smell, and amber gumming.
     Although the damage appears to be a severe issue, most observed damage has resulted in slightly smaller, mis-shaped trunks. Within a few years – and usually by the first harvest -affected areas appear to be compartmentalized by the enlarging trunk and are rarely visible. Tree loss has not been observed in normal drift incidences.

     The 2015 California Almond crop has been projected at 1.85 billion kernel pounds, down 1% from last year. Yield is estimated at 2,080 pounds per acre, which is 3% lower than last year.

     The subjective estimate is prepared by the USDA National Agricultural Statistics Service, Pacific Regional Office, and was presented at noon on May 5 in the offices of the Almond Board of California. The subjective reports provide early estimates about the coming crop. The estimate is made by contacting a random sample of growers by phone to provide an opinion of their estimates. This year, responding growers represent 29% of the total bearing acreage, which is estimated at 890,000 acres.

     An objective forecast, based on actual counts and measurements taken in 940 randomly selected orchards throughout the state’s almond growing region, will be released on July 1.

     A lot of excitement this past week with the passing storms. Some large thunderstorms passed through Merced Co. dropping some hail and rain. As with any thunderstorms, rainfall totals vary. A few calls have yielded some concerns which are highlighted below.

'Nonpareil' kernels almost completely filled. Photo taken May 4th near Los Banos, CA
"Nonpareil" kernels almost completely filled. Photo taken May 4th near Los Banos, CA

  1. Irrigation for areas with low rainfall totals will most likely still be needed. Use is highly variable depending on the weather, but for the most part, a warm (>80F) sunny day will require 0.25″ of water/acre to maintain full irrigation for a mature block. Cloud cover and cooler temperatures can reduce demand by as much as 1/2. This is using an assumed Kc value of 1.00.
  2. Ants. Fields should be scouted and, if needed, baits should be applied. Baits – since they are growth regulators- must be applied 1 month prior to harvest for maximum effectiveness.  Be mindful that not all ants present within the orchard feed on almonds. A quick trick to distinguish “good ants” from “bad ants” is to throw potato chips or a hot dog near the mound. If consumed, it can be assumed that the colony will also feed on almond kernels. Another trick is to  stomp near the mound to bring ants to the surface. If they swarm out of the mound, are red in color with a black butt and bite, they are mostly likely fire ants. Monitoring and treatment information can be found on this previous post and at the UC IPM Website . Ants often cause more damage than expected. High populations can consume between 1-2% of the crop within four days.
  3. Hail damage. Hail can cause crop loss as it knocks nuts and new growth form the trees. Nuts that are “bruised” may fall 3-5 days after the damage occurred. If the nut remains on the tree, it will typically yield a marketable nut. Several people have asked if they should spray a fungicide to protect the damage nut. Generally, this is not advised.
  4. Crop Development is ahead of last year, and several weeks ahead of normal. Kernel fill is nearing completion in Nonpareils within Merced County, and may be completed in other areas. Plan nitrogen, irrigation, hull-split sprays accordingly.
  5. Sampling of well and canal water. A lot of orchard blocks and irrigation districts are relying on ground water for irrigation. A water sample needs to be submitted for analysis to determine the salt load within this water. Water quality can degrade as the season progresses. Water within canals can also change as decrease snowpack and river flows reduce the amount of clean water. Sample frequently if managing a salinity problem and adjust the leaching fraction as appropriate.