How to Manage Pests
UC Pest Management Guidelines
(Reviewed 4/10, updated 4/10)
In this Guideline:
Preharvest fruit sampling will
alert you to the need to treat before harvest. (Be sure to check the preharvest
interval of the pesticide if treatment is necessary.) Monitor weekly beginning
at color break (when nectarines start to turn reddish).
How to Sample (View preharvest damage photos for identification)
to 200 randomly selected fresh fruit on the tree (10-20 fruit on 10 trees) by
looking at it on the tree and rotating it slightly to detect damage caused by:
FRUIT EVALUATION AT HARVEST
Take a fruit damage
sample at harvest to assess the effectiveness of the current year's IPM program
and to determine the needs of next year's program; be sure to keep a record for
How to Sample (View harvest damage photos for identification)
Before the sorting
process begins, examine 500 to 1,000 randomly selected fruit from harvest
containers. Plan to sample 500 fruit for each variety unless unexpected damage
is discovered, in which case increase the sample size up to a maximum of 1,000
fruit in order to thoroughly assess the damage. Distinguish damage caused by
peach twig borer, oriental fruit moth, and leafrollers, San Jose scale, stink
bugs, plant bugs, and katydids as well as brown rot, rust, and scab.
Look for the
Larvae or larval feeding from peach twig
fruit moth, or
twig borer: shallow feeding holes. Over time these may appear as scabs.
fruit moth: often small entry holes that may be
difficult to see, especially if brown rot has invaded the site.
tunneling into fruit; shallow holes or grooves in the fruit surface; this
can sometimes be difficult to distinguish from severe thrips
was done just after bloom.
Live or parasitized San Jose
scale and halos or spots on the
Scabs, pits caused by stink bugs, plant bugs,
Silver discoloration on fruit surface caused by
late season thrips feeding.
- Fruit rot. In many cases, this damage may occur
in conjunction with peach twig borer or oriental fruit moth damage or other
Scab lesions on fruit are dark spots and may
have green or yellow halos. They are most commonly on the upper surface and
may merge to form large blotches.
- Rust lesions, which can resemble stink bug
damage but can be distinguished by the presence of spore masses in the lesions,
and lesions are often surrounded by halos.
Powdery mildew scars are raised, scabby patches
of corky tissue.
Record on a harvest
monitoring form the number of fruit infested
by larvae, type of larvae present or, if there are no larvae present, whether
damage is surface feeding only or if the larvae penetrated the fruit. Record
the number of fruit with live San Jose scale, or parasitized San Jose scale.
Record the number of fruit with damage caused by stink bugs, plant bugs,
katydids, and thrips, and note any indication of rust, brown rot, scab, and
UC IPM Pest Management Guidelines:
UC ANR Publication
W. J. Bentley (Crop Team Leader), UC IPM Program, Kearney Agricultural Center, Parlier
K. R. Day, UC Cooperative Extension Tulare County
R. A. Duncan, UC Cooperative Extension Stanislaus County
J. K. Hasey, UC Cooperative Extension Sutter/Yuba counties
S. Johnson, Pomology, Kearney Agricultural Center, Parlier
J. A. Roncoroni, UC Cooperative Extension Napa County
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