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How to Manage Pests
UC Pest Management Guidelines
Pear
Pear Sawfly (Pear Slug)
Scientific name: Caliroa cerasi
(Reviewed 2/07,
updated 3/08)
In this Guideline:
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The pear sawfly, commonly known as pear slug, is not a true slug but
resembles one because it exudes a slimy olive green coating over its slug-shaped
body; it is actually the larvae of a sawfly. Pear slugs overwinter as pupae.
Adult sawflies emerge in spring and are small (about 0.2 inch or 5 mm), shiny
black, wasplike, flying insects.
Female sawflies lay eggs in the upper surface of leaves, preferring the
leaves in the upper portion of the canopy. Newly hatched larvae are white with
a yellowish brown head, turning completely yellow when mature. Soon after they
start feeding, however, they cover their bodies with the slimy coating that
makes them appear almost black. When mature, the larvae are about 0.5 inch
long; the anterior end of the body is wider than the rest of the body. They drop to the soil to pupate. There
are two generations a year with the second generation generally being larger in
number than the first and quicker to develop from egg to pupa.
Pear slugs skeletonize foliage by removing all leaf tissue except
the fine network of veins. Damage from both generations can reduce fruit size
at maturity. If the second generation causes extensive defoliation of trees,
bloom may be reduced the following spring.
Pear slug is often under effective biological control, but in recent
years it has become an increasing problem in mating disruption orchards where
broad-spectrum cover sprays are no longer used but populations of natural enemies may not have adequately
reestablished.
In
backyard trees or organically managed orchards, if a potentially damaging
population develops, washing the tree with water from a garden or sprayer hose
will dislodge them without disrupting parasites and predators.
Organically
Acceptable Methods
Biological control and sprays of the Entrust formulation of spinosad
are organically acceptable methods.
Monitoring
and Treatment Decisions
In orchards with a history of pear sawfly, start looking for eggs in
top shoot samples in April. Continue monitoring top shoots from 20 trees per
orchard for larvae throughout the growing season and after harvest. Spot treat
localized infestations in these orchards to prevent them from spreading. For
more information regarding sampling for additional pests during the growing
season, see SAMPLING DURING FRUIT DEVELOPMENT and POSTHARVEST SURVEY.
| Common name |
Amount to Use |
R.E.I.+ |
P.H.I.+ |
| (trade name) |
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(hours) |
(days) |
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| When choosing a
pesticide, consider information relating to impact
on natural enemies and honey bees
and environmental impact. Not all registered pesticides are listed. Always read label of product being used.
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| A. |
SPINOSAD |
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(Entrust)# |
1 oz/acre |
4 |
7 |
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(Success) |
3.5 oz/acre |
4 |
7 |
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MODE OF ACTION GROUP
NUMBER1: 5
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COMMENTS: Do not apply more than 29 oz/acre/year of Success or 9 oz/acre/year of Entrust. |
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UC IPM Pest Management Guidelines: Pear
UC ANR Publication 3455
Insects and Mites
L. G. Varela, UC IPM Program, UC Cooperative Extension Sonoma County
R. B. Elkins, UC Cooperative Extension Lake County
R. A. Van Steenwyk, Insect Biology, UC Berkeley
C. Ingels, UC Cooperative Extension Sacramento County
Acknowledgment for contributions to Insects and Mites:
C. Pickel, UC IPM Program, UC Cooperative Extension Sutter/Yuba counties
P. W. Weddle, Weddle, Hansen & Associates
P. Chevalier, United Ag Products, Ukiah
B. Knispel, Pest Control Adviser, Upper Lake
T. Lidyoff, Purity Products, Healdsburg
G. McCosker, AgroTech, Kelseyville
B. Oldham, Ag Unlimited, Ukiah
D. Smith, Western Farm Service, Walnut Grove
J. Sisevich, AgroTech, Kelseyville (retired)
B. Zoller, The Pear Doctor, Inc., Kelseyville
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