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How to Manage Pests
UC Pest Management Guidelines
Walnut
Dormant Monitoring
(Reviewed 12/07,
updated 12/07)
In this Guideline:
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Monitor during the dormant period to determine the need for a spring
treatment to manage populations of walnut scale, frosted scale, European fruit
lecanium scale, San Jose scale and European red mite.
How to monitor:
- Examine
scaffolds, limbs, branches, and prunings for the following pests : walnut scale, San
Jose scale, frosted scale nymphs, and European red mite eggs.
- If
they have been a problem in the past, monitor for European fruit lecanium
scale.
- Look
for evidence of parasitization as
characterized by emergence holes in the body of the dead, mature scale. A high
level of parasitization may keep populations down, thus eliminating the need
for treatment.
- Map
out areas of concern for spring monitoring and possible treatments.
Treatment thresholds:
Walnut scale: Natural
enemies usually can be relied on to keep walnut scale from causing damage. If
scales are present but a high degree of parasitization is observed, treatments
will not be needed.
Frosted scale: If you find
5 or more nymphs per foot of last year's wood throughout the orchard and less
than 90% parasitized nymphs, treatment is warranted.
European fruit
lecanium scale: Same as
frosted scale.
San Jose scale: If you find
5 or more black caps per foot of last years wood and less than 90% parasitism,
treatment is warranted.
European red mite: No
damage threshold levels are available to determine when to treat. Avoid treating
low-to-moderate levels of European red mites because they can be important in
maintaining predators of other mites.
IMPORTANT LINKS
![[UC Peer Reviewed]](/IMAGES/logo-ucpeerreviewed.jpg)
UC IPM Pest Management Guidelines: Walnut
UC ANR Publication 3471
General Information
C. Pickel (Crop Team
Leader), UC IPM Program/UC Cooperative Extension, Sutter/Yuba counties
J. E. Adaskaveg, Plant Pathology, UC Riverside
J. A. Grant, UC Cooperative Extension, San Joaquin County
J. K. Hasey, UC Cooperative Extension, Sutter/Yuba counties
R. P. Buchner, UC Cooperative Extension, Tehama County
K. K. Anderson, UC Cooperative Extension, Stanislaus County
W. J. Bentley, UC IPM Program/ Kearney Agricultural Center, Parlier
W. W. Coates, UC Cooperative Extension, San Benito County
R. B. Elkins, UC Cooperative Extension, Lake County
W. H. Krueger, UC Cooperative Extension Glenn County
D. Light, USDA, Albany, CA
M. V. McKenry, Kearney Agricultural Center, Parlier
A. Shrestha, UC IPM Program/Kearney Agricultural Center, Parlier
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