How to Manage Pests

UC Pest Management Guidelines

Almond

Dormant Spur or First-Year Twig Sampling and Treatment Guidelines

(Reviewed 3/09, updated 11/12)

Dormant spur or twig sampling is used to determine the need for a dormant treatment to control San Jose scale, European red mite, brown mite, European fruit lecanium, and almond scab, caused by Fusicladium carpophilum (Venturia carpophila). Spurs or twigs are the short green shoots producing the flower buds, and represent twig growth that developed in the previous summer and fall. They have not yet developed bark. Dormant spur samples are taken once a year between mid-November and the end of January.

HOW TO SAMPLE

View photos for identification

• Randomly select 35 to 50 trees from each orchard or plot to be sampled.
• Selecting major scaffolds randomly, clip 2 to 3 spurs or twigs from the inside of each tree's canopy for a total of 100.
• Clip the spur off at the base, making sure to include some old spur wood along with the last year's growth to detect parasite activities on scales.
• Using a hand lens or binocular microscope, examine 20 of the spurs for scales, mite eggs, and scab lesions and record observations in a sampling form. It is not necessary to count the number of individual insects or mite eggs present, just identify the pest or disease and record whether it is present or not.
• Note how many scales are parasitized. A parasitized scale can be distinguished from a live scale by a small hole in the top of the scale covering. Parasitized European fruit lecanium scales turn black. If a large number of scales have been parasitized, minimize the use of insecticides during the growing season and only use those that are not harmful to parasites so that naturally occurring populations will not be destroyed.

TREATMENT THRESHOLDS

1. Randomly select a first set of 20 spurs out of the 100 spurs collected (20/100):
   • If no scab lesions are found, no more spurs need to be examined. For scales and mite eggs, at least 40 spurs need to be inspected to make a treatment decision.
   • For scab, if 4 or more infected spurs out of 20 (20%) are found, treat. For scales and mite eggs, at least 40 spurs need to be inspected to make a treatment decision.
   • If fewer than 4 spurs are infested with scale, mites, or scab, examine the next 20 spurs.
2. Randomly select a second set of 20 spurs (40/100):
   • Add infected spurs from first set to the second set and calculate threshold out of 40 spurs. For scales and mite eggs, if 20% are found, treat. For scab lesion, treat when 10% of spurs are infected. No further spurs have to be inspected.
   • If fewer spurs than the treatment threshold are infested, but more than 1, examine the next 20 spurs.
3. Randomly select a third set of 20 spurs (60/100):
   • Add infected spurs from previous sets to set three and calculate threshold out of 60 spurs. Treat, if the treatment threshold is reached. No further spurs have to be inspected.
   • If fewer spurs than the treatment threshold are infested, but more than 3, examine the next 20 spurs.
4. Randomly select a fourth set of 20 spurs (80/100):
   • Add infected spurs from previous sets to set four and calculate threshold out of 80 spurs. Treat, if the treatment threshold is reached. No further spurs have to be inspected.
   • If fewer spurs than the treatment threshold are infested, but more than 5, examine the next 20 spurs.
5. Select last set of 20 spurs (100/100):
   • Add infected spurs from previous sets to set five and calculate threshold out of 100 spurs. Treat, if the treatment threshold is reached.

To determine treatment thresholds, use the table below, which has detailed treatment threshold information for dormant spur sampling. A sampling form (PDF) is available for download.

Do not combine totals for the two scale species. For example, if 3 spurs out of a sample of 20 are infested with San Jose scale and 3 spurs contain European fruit lecanium, neither has exceeded the threshold and sampling should continue. Treat for brown mite and European red mite if 20% or more spurs are infested.

IMPORTANT LINKS

• Dormant spur sampling form for san jose scale, european fruit lecanium, and mites (PDF)
• Photos of pests monitored with the dormant spur sample

PUBLICATION

UC IPM Pest Management Guidelines: Almond
UC ANR Publication 3431

General Information

F. G. Zalom, Entomology, UC Davis
C. Pickel, UC IPM Program, UC Cooperative Extension, Sutter/Yuba counties
W. J. Bentley, UC IPM Program, Kearney Agricultural Center, Parlier
D. R. Haviland, UC IPM Program, UC Cooperative Extension, Kern County
R. A. Van Steenwyk, Insect Biology, UC Berkeley
Acknowledgment for contributions to Insects and Mites:
R. E. Rice, Kearney Agricultural Center, Parlier
L. C. Hendricks, UC Cooperative Extension, Merced County
R. L. Coviello, UC Cooperative Extension, Fresno County
M. W. Freeman, UC Cooperative Extension, Fresno County

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