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How to Manage Pests
UC Pest Management Guidelines
Prune
Green Fruitworms
Scientific Names:
Orthosia hibisci, Amphipyra pyramidoides, Xylomyges curialis, and others.
(Reviewed 6/06,
updated 6/06)
In this Guideline:
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Green fruitworms include several species of
caterpillars, all of which are pale green, often with whitish stripes down each
side of the body and a narrow stripe down the middle of the back. Most species
pass the winter as pupae or adults, and have one generation each year.
Green fruitworms eat large holes in young leaves
and fruit during late bloom and petal fall causing fruit to be scarred.
Dormant treatments and bloom time applications for
other pests help keep fruitworm populations under control. Regular monitoring
at petal fall is
important so action can be taken if damaging populations develop.
Biological Control
Certain parasitic wasps (Cotesia
[=Apanteles], Eulophus, Meteorus, and Ophion spp.) help keep green fruitworm
populations under control.
Organically Acceptable
Methods
Biological control and sprays of Bacillus
thuringiensis and the Entrust formulation of spinosad are
acceptable for use on an organically certified crop.
Monitoring and Treatment Decisions
If treatment is necessary, treat at late bloom to
petal fall when larvae are present. View photos to identify caterpillars present during bloom. A treatment threshold of one
worm per 100 fruit clusters per 20-acre block or 1 worm per 50 beat-tray
samples has been developed for pears and probably is applicable to stone
fruits. Bacillus thuringiensis formulations are safe to use during bloom and are
effective on small larvae. If you use other materials, make applications during
or shortly after petal fall. Spot-treat localized infestations. Continue to
monitor for the pest after treatment. If no more young larvae are found, no
more control actions are necessary for the season.
Fruit Damage Sample. In mid-July, take a fruit damage sample to assess
the overall effectiveness of the current year's IPM program and to determine
next year's needs. For more information, see FRUIT EVALUATION AT HARVEST. Record on a monitoring form
the number of fruit infested by larvae, type of larvae present, whether the
damage is surface feeding only or if the larvae penetrated the fruit.
| Common name |
Amount to Use** |
P.H.I.+ |
| (trade name) |
(conc.) |
(dilute) |
(days) |
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| The following materials are listed in
order of usefulness in an IPM program, taking into account efficacy, impact on natural
enemies and honey bees,
and impact of the timing
on beneficials.
When choosing a pesticide, also consider information relating to
environmental impact.
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| A. |
BACILLUS THURINGIENSIS ssp. KURSTAKI# |
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(various products) |
Label rates |
— |
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MODE OF ACTION: A microbial (Group 11.B2)1 insecticide. |
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COMMENTS:
Most effective on small caterpillars. Does not destroy natural enemies Make 2
applications during bloom: the first between popcorn and the beginning of bloom and the second 7–10
days later, but no later than petal fall. Compatible with fungicide sprays, and can be
tank mixed with them. Good coverage is essential. Ground application using a
concentrate rate (80–100 gal water maximum) is preferred. If aerial
applications must be made because conditions do not permit ground application,
a concentrate rate (5 gal or less) is preferred. Fly material on at a height
of about 20 feet over the canopy using appropriate nozzles to allow better deposition on the tree tops. |
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| B. |
SPINOSAD |
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(Entrust)# |
1.71–2.5 oz |
0.43–0.6 oz |
7 |
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(Success) |
6–8 oz |
1.5–2 oz |
7 |
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MODE OF ACTION: A microbial (Group 5)1 insecticide. |
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COMMENTS:
Most effective when applied at petal fall. Apply only during late evening, night, or early morning to avoid injury to honey bees. |
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| C. |
METHOXYFENOZIDE |
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(Intrepid) 2F |
8-16 oz |
2-4 oz |
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MODE OF ACTION: An insect growth regulator (Group 18)1 insecticide. |
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COMMENTS:
Apply at petal fall. Use allowed under a supplemental label. Do not apply more than 16 fl oz/acre/application or 64 fl oz/acre/season. |
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UC IPM Pest Management Guidelines: Prune
UC ANR Publication 3464
Insects and Mites
C. Pickel, UC IPM Program, Sutter/Yuba counties
F. J. A. Niederholzer, UC Cooperative Extension, Sutter/Yuba counties
W. H. Olson, UC Cooperative Extension, Butte County
F. G. Zalom, Entomology, UC Davis
R. P. Buchner, UC Cooperative Extension, Tehama County
W. H. Krueger, UC Cooperative Extension Glenn County
Acknowledgment for contributions to the insects and mites section:
W. O. Reil, UC Cooperative Extension Solano/Yolo counties
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