|
How to Manage Pests
UC Pest Management Guidelines
Pear
Pear Psylla
Scientific name: Cacopsylla (=Psylla) pyricola
(Reviewed 2/07,
updated 3/8)
In this Guideline:
|
|
Pear psylla is one of the most serious insect pest of pears because
of its ability to develop resistance to
insecticides and vector the pathogen that causes pear decline.
Overwintering pear psylla adults are
somewhat darker and larger (0.125 inch or 3 mm) than summer adults (0.08 inch
or 2 mm). Adults hold their transparent wings rooflike over their dark to reddish brown bodies
when at rest; they resemble tiny cicadas. A dark spot on the top middle edge of
both wings helps to distinguish pear psylla from other psylla. Tiny, elongated
yellowish eggs,
which are barely visible without a hand lens, are laid on or near fruit spurs
starting in late January or early February. As buds open, females lay eggs
along midribs and petioles of developing leaves or on stems and leaves of
blossoms. Pear psylla nymphs pass through five instars, four of which are
almost completely encased in honeydew. When first hatched, the tiny nymphs are
yellow with red eyes and black antennae. The third stage is yellowish green and
the fourth greenish brown. The fifth instar is called the hardshell stage and
it is dark with prominent wing pads.
Generally, pear psylla is a greater problem on European varieties
than on Asian varieties. Pear psylla damages pears in several ways. Loss of
crop and tree vigor, and sometimes loss of trees, can occur from pear decline
disease, caused by a phytoplasma organism that psylla injects into pear trees.
Pear decline has varying effects on the trees depending on variety, rootstock,
quality of the growing site, and pear psylla numbers. Honeydew, produced by
psylla nymphs as they feed, drops onto fruit. A black sooty mold grows on the honeydew and the fruit skin russets, which downgrades fruit for
fresh market use. Psylla feeding and injection of a toxin into the tree causes
portions of the leaf blade to blacken, and leaves to yellow and sometimes fall.
Growth and productivity of the tree can be severely reduced for one or more seasons.
Pear psylla management in California is aimed at holding psylla
populations at low levels throughout the year. Populations that are allowed to
reach high levels become difficult to control, especially if they migrate in
fall. Use one or two dormant sprays to reduce populations to no more than 1
psylla per 100 beat-tray samples by the time trees break dormancy. If the
overwintering adult population is adequately reduced before egg laying starts
in late January or early February, the population can usually be kept low
throughout the foliage season by petroleum oil, applied alone or added to
sprays for other pests, and by natural enemies. If overwintering psylla adults
produce eggs before the dormant spray is applied, however, a higher base
population is present all season. This makes control difficult because when
generations overlap, all life stages are present, and not all stages are
susceptible to chemical treatments. It is essential to keep populations low through
summer and after harvest to prevent migration of adults in fall. If substantial
numbers of adults overwinter outside the orchard and migrate in after
application of dormant sprays, success of the management program will be
limited.
Biological Control
There are many naturally occurring
predators and parasites of pear psylla including green lacewings, brown lacewings, and minute pirate bugs.
Nonselective codling moth materials destroy many of these beneficials,
resulting in outbreaks of this pest. Orchards in a codling moth mating
disruption program generally have greatly reduced levels of pear psylla. In
addition, some codling moth materials and some psylla materials destroy mite
predators and chronic mite problems will develop. Although predators and parasites do not provide complete
control in commercial orchards, they may maintain psylla populations below
economically damaging levels when supplemented with a year round program of oil
treatments. Predation is probably occurring when top shoot samples show only
one to several psylla nymphs per infested shoot; in the absence of effective
predation there are apt to be 10 or more psylla nymphs on a shoot because each
female psylla lays 10 to 20 eggs at a time.
Cultural Control
To reduce the effects of pear decline, use
Winter Nelis, Old Home X Farmingdale, or Pyrus betulaefolia seedlings for rootstock and maintain pear psylla populations at low levels.
Organically Acceptable Methods
Organically acceptable methods include
biological and cultural control and sprays of approved oil, insecticidal soaps,
azadirachtin, and kaolin clay.
Monitoring and Treatment Decisions
Psylla control is best accomplished in
the dormant season,
but if psylla have dispersed out of the orchard and into areas where they won't
be treated, dormant control becomes more difficult. Monitor psylla populations
year round to predict and prevent outbreaks and movement of adults from the
orchard.
- In December, monitor overwintering adults with 100
beating tray samples (each beat sample consists of three taps).
- Beginning in February monitor eggs by sampling 100
fruit spurs. (For additional information, see DORMANT/DELAYED-DORMANT SAMPLING.)
- At bloom, monitor nymphs and eggs by clipping one
flower cluster from the top and one from eye level of 50 trees (100 total) and
counting nymphs and eggs on the cluster. (For additional information, see SAMPLING
AT BLOOM.)
- During fruit development take weekly shoot samples:
one from the top and one from eye level of 20 trees per block. Examine 5 leaves
per shoot for pear psylla nymphs, eggs, and honeydew. As the season progresses,
sampling can eventually focus on the top shoots because psylla will become
concentrated on the new growth at the tops of trees where good spray coverage
is hardest to achieve. (For more information regarding sampling for other pests
at this time, see SAMPLING DURING FRUIT DEVELOPMENT.)
- At harvest, examine 200 fruit per bin from 5 bins per
orchard (or 20-acre block in large orchards) for a total of 1,000 fruit. (For
additional information on this sample, see HARVEST FRUIT SAMPLE.)
- After harvest, collect one top shoot and one eye level
shoot from 20 trees and examine 5 leaves on each shoot for psylla eggs and
nymphs. Count the number of shoots infested. (For additional information, see SAMPLING
AT BLOOM.)
Dormant season. Each winter make one or two dormant oil sprays to
reduce overwintering populations to no more than one adult psylla per 100
beating tray samples. If there are an average of two or more adults per 20 beat
samples, apply at least one dormant treatment. If there are more than 50 adults
per 50 beat samples, two treatments will be needed.
Growing season. Use the following control action thresholds to
determine if treatments are necessary during the growing season.
CONTROL ACTION THRESHOLDS |
Bloom: |
2+ flower clusters with eggs per 100 clusters |
Fruit development: |
1+ top shoots with psylla per 20 top shoots |
Postharvest: |
5+ top shoots with psylla per 20 top shoots |
Common name |
Amount to Use** |
R.E.I.+ |
P.H.I.+ |
(trade name) |
(conc.) |
(dilute) |
(hours) |
(days) |
|
The following materials are listed in order of
usefulness in an IPM program, taking into account efficacy and impact
on natural enemies and honey bees. When choosing
a pesticide, also consider information relating to environmental impact.
|
|
DORMANT |
NOTE: All orchards should be treated. |
A. |
NARROW RANGE OIL# |
8 gal |
1.5–2 gal |
4 |
0 |
|
. . . or . . . |
|
DORMANT FLOWABLE EMULSION |
6–8 gal |
2–3 gal |
4 |
0 |
|
. . . or . . . |
|
DORMANT PLUS |
6–8 gal |
3–4 gal |
4 |
0 |
|
MODE OF ACTION: Contact including smothering and barrier effects. |
|
COMMENTS: Apply during warm, sunny weather from leaf fall to
start of egg laying for best results. Do not apply oil in the dormant season
until root zone is wet from rain or irrigation. Apply oil in late morning when
dew or rain has dried from the bark. Do not apply oil after a period of
drying wind or extreme cold. Oil kills adult psylla but does not control
eggs. It does discourage egg laying for about 1 month, however. For narrow
range oil, check with your certifier to determine which products are organically acceptable. |
|
JUST BEFORE EGG LAYING
|
NOTE: Make this
treatment only after an earlier oil spray has been applied and post treatment
monitoring counts show more than 5 psylla/100 beats or pretreatment counts
were about 70 to 100 adults/100 beats. If an application of abamectin and oil is planned for petal fall, this treatment is not necessary. |
A. |
ESFENVALERATE* |
|
(Asana XL) 0.66EC |
9.6–19.2 fl oz |
7.3–12.8 fl oz |
12 |
28 |
|
MODE OF ACTION GROUP NUMBER1: 3 |
|
COMMENTS: These rates may be applied only in the dormant to
prebloom period. Esfenvalerate at low rates may no longer be effective where
psylla have developed tolerance to this material as a result of frequent use
at higher rates. Check control results by monitoring. For dilute spray, apply
150-250 gal/acre but don't apply more than 19.2 fl oz/acre/treatment. Provide
100-ft buffer zone from any sensitive aquatic site. Make application when the wind speed is between 3 and 10 miles per hour. |
|
. . . PLUS . . . |
|
NARROW RANGE OIL |
|
(Supreme) |
4 gal |
0.75–1 gal |
4 |
0 |
|
. . . or . . . |
|
DORMANT FLOWABLE EMULSION |
8 gal |
2 gal |
4 |
0 |
|
MODE OF ACTION: Contact including smothering and barrier effects. |
|
|
B. |
KAOLIN CLAY# |
|
(Surround) |
Label rates |
4 |
0 |
|
MODE OF ACTION: Unknown. An inorganic insecticide. |
|
COMMENTS: Apply prebloom; may cause mite outbreaks when used later in season. |
|
PETAL FALL |
A. |
NARROW RANGE OIL |
|
(Supreme, Superior) |
4 gal |
1 gal |
4 |
0 |
|
MODE OF ACTION: Contact including smothering and barrier effects. |
|
COMMENTS: Use if control is not obtained during the dormant
season. The supreme type of superior oil has given better control than other
superior oils. Add one of the insecticides at the rates listed below when
more than 3 clusters/100 clusters in the green tip to tight cluster sample
are infested. Repeated applications of oil at this time may cause tree injury. |
|
. . . PLUS . . . |
|
ABAMECTIN* |
|
(Agri-Mek) 0.15EC |
10–20 fl oz |
2.5–5 fl oz |
12 |
28 |
|
MODE OF ACTION GROUP NUMBER1: 6 |
|
COMMENTS: Most effective timing for this spray is at petal
fall; can be combined with a fire blight spray. Adults that survived the
dormant spray have laid most of their eggs by this time. This spray targets
young nymphs as they hatch or as they feed. Generally, this spray follows a
dormant application of oil. Maximum of 2 applications/season but to avoid the
development of resistance to this material, apply abamectin only once per year. Apply with ground equipment only. |
|
. . . or . . . |
|
PYRIPROXYFEN |
|
(Seize) |
4-5 oz |
1-1.25 oz |
12 |
45 |
|
(Esteem) 0.86EC |
16 fl oz |
4 fl oz |
12 |
45 |
|
MODE OF ACTION GROUP NUMBER1: 7C |
|
COMMENTS: An insect growth regulator that targets egg hatch.
Can be supplemented with an application in the delayed dormant period as an
ovipositional deterrent. If only one application is to be made, petal fall is
the more effective timing. Do not exceed two applications/growing season. Do
not skip rows during application or apply more than 32 fl oz/acre/season of Esteem or 10 oz/acre/season of Seize. |
|
B. |
THIAMETHOXAM |
|
(Actara) |
4.5-5.5 oz |
1.125-1.375 oz |
12 |
see comments |
|
MODE OF ACTION GROUP NUMBER1: 4A |
|
COMMENTS: Allow a minimum of 10 days between applications; do
not exceed 8 oz/acre/season. Preharvest interval is 14 days when 2.75 oz/acre or less is used and 35 days when more than 2.75 oz/acre is used. |
|
C. |
IMIDACLOPRID |
|
(Provado) 1.6F |
20 fl oz |
5 fl oz |
12 |
7 |
|
MODE OF ACTION GROUP NUMBER1: 4A |
|
MID-MAY/MID-JUNE TO PREHARVEST
|
NOTE: High temperatures suppress psylla populations. |
A. |
NARROW RANGE OIL# |
|
(Supreme) |
4 gal |
1 gal |
4 |
0 |
|
MODE OF ACTION: Contact including smothering and barrier effects. |
|
COMMENTS: Follow Monitoring and When to Treat guidelines. If
oil is applied within 4 weeks of harvest, reduce the rate by 25% for each
week closer to harvest (e.g., 2 weeks before harvest, use 0.5 gal oil/100 gal
water). Check with your certifier to determine which products are organically acceptable. |
|
POSTHARVEST |
NOTE: Sulfur and oil
sprays can be very phytotoxic to pear trees, especially when the weather is hot. |
A. |
NARROW RANGE OIL# |
|
(Supreme, Superior) |
4–6 gal |
1–1.5 gal |
4 |
0 |
|
MODE OF ACTION: Contact including smothering and barrier effects. |
|
COMMENTS: Apply as soon as possible after harvest for best
results. The addition of surfactants, especially plant washes, improves
results but may decrease bloom the following year. Irrigate trees before
spraying. Check with your certifier to determine which products are organically acceptable. |
|
B. |
WETTABLE SULFUR# |
6–10 lb |
— |
24 |
0 |
|
MODE OF ACTION: Unknown. An inorganic insecticide. |
|
. . . or . . . |
|
LIME SULFUR# |
5 gal |
1.25 gal |
48 |
0 |
|
MODE OF ACTION: Unknown. An inorganic insecticide. |
|
. . . PLUS . . . |
|
NARROW RANGE OIL# |
|
(Supreme, Superior) |
6 gal |
2 gal |
4 |
0 |
|
MODE OF ACTION: Contact including smothering and barrier effects. |
|
COMMENTS: Do not apply lime sulfur and oil spray any sooner
than November 1 and only on trees not suffering from moisture stress.
Phytotoxicity may occur any time the weather is hot so watch weather
conditions closely. Check with your certifier to determine which products are organically acceptable. |
|
C. |
AZADIRACHTIN# |
|
(Neemix, etc.) |
Label rate |
12 |
0 |
|
MODE OF ACTION GROUP NUMBER1: 18B |
|
COMMENTS: Can be effective against low populations. Check with
your pest control advisor for the most effective label rates. This is a restricted use material in an organically certified crop. |
|
|
UC IPM Pest Management Guidelines: Pear
UC ANR Publication 3455
Insects and Mites
L. G. Varela, UC IPM Program, UC Cooperative Extension Sonoma Co.
R. B. Elkins, UC Cooperative Extension Lake Co.
R. A. Van Steenwyk, Insect Biology, UC Berkeley
C. Ingels, UC Cooperative Extension Sacramento Co.
Acknowledgment for contributions to the insects and mites section:
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, United Ag Products, Kelseyville
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
B. Zoller, The Pear Doctor, Inc., Kelseyville
Top of page
|