Blue Diamond Almond Facts November-December 2021


A dormant/delayed dormant spray , if needed, can help control two significant pests of almond — scale and almond scab. To find out if a prebloom treatment for either or both of these pests is needed, take dormant spur/twig samples beginning in November. Economic thresholds have been developed to aid in decision making. See details on sampling and thresholds for both pests at: almond/Dormant-Spur-or-First-Year-Twig-Sampling-and- Treatment-Guidelines. Oil is important to effective scale and scab control, but consult with an experienced PCA regarding oil use if December and January are dry. Fall/winter weed control could be more of an issue with the early rains this year pushing winter weed growth. Use herbicide(s) that deliver the best control of current weeds in the orchard. Help matching herbicide to weed population can be found in the UC ANR herbicide efficacy tables at: in-Almond-to-Herbicide-Control. To help identify weeds in the orchard, pictures of specific weed seedlings and a weed survey form are available at: m003pcweeds02.html. Preemergent herbicides offer longer lasting weed control with fewer applications compared to post-emergent (“burndown”) herbicides and so should be more cost- effective. Bare soil and incorporation with a small amount (0.25–0.5") of water (rain or irrigation) are needed for best preemergent weed control. Large storms with high rainfall totals are not good for herbicide efficacy as inches of water following spraying can push some amounts of certain herbicides down in the root-zone and below the area near the soil surface where most weeds are found (and controlled with pre-emergent materials). Small rainfall or irrigation events (0.25–0.5") move the herbicide into the soil where it is fixed and not affected by any large rainfall events. Longer lasting weed control with the same rate/acre of preemergent herbicides can be achieved with multiple applications. For example, recent research by Dr. Brad Hanson and his lab showed that sequential applications (December and March) of two lower doses of an herbicide produced longer weed control than the same total rate per

Sweeper blowing leaves from the tree rows ahead of spraying preemergent herbicide. Photo credit: Franz

acre applied once in December. See details of this work in: ? postnum=29080. Young orchards in particular can benefit from preemergent herbicide use. Weeds compete with young trees for water and nutrients and hide harmful rodents (voles and gophers). Only a handful of pre-emergent herbicides are labeled (and safe) for use in the first leaf. Check with your PCA regarding materials, rates and timings, and always read the label ahead of application. Also, see the “Weed management in young orchards” in the Young Orchard Handbook ( Gophers can kill almond trees and do not hibernate. See information on gopher control at: r105600211.html (it’s a cherry IPM page, but gopher biology and control information are the same in almond). Better gopher control is achieved when workers are trained in trapping and baiting. See a how-to video on trapping

practices with Roger Baldwin, UCCE Specialist, at: ? v=iDW0l6eeG0M.

Soils: Salt Management/Infiltration If you haven’t done so already, take soil samples to assess the salt situation in the root zone of different orchards.

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