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How to Manage Pests
UC Pest Management Guidelines
Pear
Mealybugs
Scientific names:
Grape mealybug: Pseudococcus maritimus
Obscure mealybug: Pseudococcus viburni
(Reviewed 2/07,
updated 3/8)
In this Guideline:
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The grape and obscure mealybugs closely resemble each other. Both
mealybugs are most damaging in old trees with rough bark that shelter
overwintering nymphs and egg clusters. Eggs are yellowish to orange and are
laid in a cottony mass. The young
crawlers are orange. Mature mealybugs are about 0.2 inch (5mm) long with dark
purple-gray, somewhat flattened bodies that are uniformly covered with a white
powdery wax. Long caudal filaments along the lateral margin of the body become
progressively shorter toward the head.
Mealybugs occasionally feed in the calyx end of maturing fruit,
which may become soft as the pear ripens. Because mealybugs cannot be removed
with present washing methods, infested lots of fruit are rejected by both
cannery and fresh market handlers. Honeydew is also produced and may cause
russetting on pears and enable a black sooty fungus to grow on the surface,
rendering the fruit unfit for fresh shipment.
Mealybugs are minor pests in pear orchards and only occasionally
become pests when their predators and parasites are unable to keep them below
economically damaging levels. Mealybugs are most damaging in old trees with
rough bark that shelters overwintering nymphs and egg clusters.
Biological Control
At least five species of parasitic wasps attack grape mealybugs in
California. Little research on these parasites has been conducted, but it is
assumed they play a prominent role in regulating populations. The impact of the
different species varies from time to time and place to place. Grape mealybugs
that are parasitized by two tiny wasps, Acerophagus notativentris and Pseudophycus angelicus, have multiple emergence holes that are easily seen
with a hand lens. Ants must be controlled to keep them from interfering with these natural enemies.
Two parasitic wasps, Pseudophycus flavidulus and Leptomastix
epona, have been imported for release against obscure mealybugs but are not
commercially available. To ensure survival of parasites, do not use disruptive
insecticides during the growing season.
The
most effective mealybug predator is a lady beetle called the mealybug destroyer, Cryptolaemus
montrouzieri, which can be found in coastal regions. Cecidomyiid
flies prey on mealybug eggs and small larvae. These predators plus green
lacewings, minute pirate bugs,
and spiders are important in keeping mealybug populations in check.
Organically
Acceptable Methods
Biological control and oil sprays used without chlorpyrifos are
organically acceptable methods.
Monitoring
and Treatment Decisions
Mealybugs can be detected during the dormant season by checking under
bark and in protected places for overwintering eggs or crawlers (see DORMANT/DELAYED-DORMANT
SAMPLING for
information about monitoring other pests at this time).
The
finger bud to
cluster stage is the best time to sample populations to estimate control needs. Collect one
fruit spur from the top and one from eye level of 50 trees (100 total) in a
block and count the number infested with mealybug nymphs (see SAMPLING
AT BLOOM). Continue
looking for mealybugs in the fruit calyx through harvest during the weekly
fruit sample (see SAMPLING DURING FRUIT DEVELOPMENT and HARVEST FRUIT SAMPLE for more information).
Dormant
and delayed dormant oil applications for other pests reduce mealybug
populations but are not adequate to control heavy populations. The best time to
treat is from cluster bud to bloom when crawlers of the first generation become active. Because of prolonged
emergence during June, crawlers of the second generation are more difficult to
control. During the cluster bud to bloom period, treat when four or more
infested spurs are found.
| Common name |
Amount to Use** |
R.E.I.+ |
P.H.I.+ |
| (trade name) |
(conc.) |
(dilute) |
(hours) |
(days) |
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| 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.
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| DELAYED DORMANT |
| A. |
NARROW RANGE OIL |
8 gal |
2 gal |
4 |
0 |
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MODE OF ACTION: Contact including smothering and barrier effects. |
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. . . or . . . |
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DORMANT FLOWABLE EMULSION |
6–8 gal |
2–3 gal |
4 |
0 |
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MODE OF ACTION: Contact including smothering and barrier effects. |
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. . . or . . . |
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DORMANT PLUS |
6–8 gal |
3–4 gal |
4 |
0 |
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MODE OF ACTION: Contact including smothering and barrier effects. |
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. . . PLUS . . . |
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CHLORPYRIFOS* |
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(Lorsban) 4E |
4 pt |
1pt |
4 days |
N.A. |
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MODE
OF ACTION GROUP NUMBER1: 1B
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COMMENTS: For use
during dormant/delayed dormant season only. For best results, delay the
delayed dormant treatment as long as possible. Chlorpyrifos has been found in
surface waters at levels that violate federal and state water quality
standards. Provide 100-ft buffer zone from any sensitive aquatic site. Make
application when the wind speed is between 3 and 10 miles per hour. Avoid drift and tail water runoff into surface waters. |
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| FINGER BUD AND SUMMER |
| A. |
THIAMETHOXAM |
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(Actara) |
4.5-5.5 oz |
1.125-1.375 oz |
12 |
see comments |
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MODE OF ACTION GROUP
NUMBER1: 4A
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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. |
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| B. |
DIAZINON* 50WP |
4 lb |
1 lb |
24 |
21 |
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MODE OF ACTION GROUP
NUMBER1: 1B
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COMMENTS: Apply when
crawlers become active. Addition of 0.5–1 gal oil/100 gal dilute improves control. Avoid drift and tailwater runoff into surface waters. |
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![[Precautions]](/IMAGES/btn-precautions_bul.gif)
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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 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
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