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How to Manage Pests
UC Pest Management Guidelines
Prune
Mealy Plum Aphid
Scientific name: Hyalopterus pruni
(Reviewed 6/06,
updated 4/09)
In this Guideline:
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DESCRIPTION OF THE PEST
Wingless mealy plum aphid adults are pale green or whitish green with three
dark green, longitudinal stripes on their backs. Their bodies are covered with
a white mealy wax. The winged form has a dark thorax and transverse bands on
the abdomen. After overwintering in the egg stage near the bases of buds, the aphids hatch during
bloom and develop into wingless adults. They will have from 3 to 13 generations
on prunes. Then winged adults appear in June and July as warm weather
approaches, and they migrate to reed grass or cattails. Wingless aphids that
remain on vigorous growth of trees throughout the summer will not be capable of
laying overwintering eggs in fall. Only the offspring of the winged adults that
return to prune trees in fall lay the overwintering eggs.
This aphid builds up in large numbers on the
undersurface of leaves in spring and causes leaves to become slightly curled and stunted. High populations can devitalize the tree, retard
growth, and reduce sugar content of fruit. Honeydew dropping on fruit can cause fruit cracking.
Several natural enemies are important in the
control of aphids in the orchard, but aphid populations often require
treatment. The best indicator of populations is orchard history. The best time
to treat is during the dormant or delayed dormant period. If aphids are a
chronic problem in the orchard, apply a treatment early in dormancy; otherwise,
sample during dormancy to determine the need to treat as
described below. Spring treatments may also be made. After harvest, a zinc
sulfate application will provide zinc to the trees as well as hasten leaf fall.
Without the leaves on the tree, the aphid life cycle is disrupted. Zinc sulfate
(36%) applied at 10-20 lb/acre can be applied in early to mid-October to help
in this process.
Biological Control
There are many natural enemies that feed on leaf
curl plum aphid; however, fruit size may still be reduced and curled leaves
will not uncurl after aphids are suppressed. The recent introductions of Aphidius
transcaspicus has led to substantial levels of parasitism of
this aphid. Important predators include: lady beetles, green lacewings, brown lacewings, syrphid flies, and soldier beetles.
Organically Acceptable
Methods
Biological control and sprays of narrow range oil
or neem oil are organically acceptable methods of controlling this pest.
Monitoring and Treatment Decisions
If aphids are a chronic problem, a treatment in
late fall/early dormancy (November 1) is a very effective way to manage these
pests and is less likely to create water quality problems caused by pesticide
runoff than treatments applied during the rainier season in January and
February. If leaves are still on trees at this time, aphids and parasites can
be present. Oil treatments are not recommended at this time because they are
very damaging to parasite populations and not effective for aphid control.
Dormant monitoring. If the November 1 treatment is not applied, be
sure to monitor during dormancy. (For more information, see DORMANT SPUR SAMPLE.) If dormant monitoring indicates treatment is
necessary, two applications of oil at bloom can be used in orchards where a
dormant/delayed dormant treatment is not required to manage scale problem.
Parasites are not active at bloom, and they are not affected by the bloom oil
sprays.
Spring monitoring. If aphids have been a problem in the past or if a
dormant or delayed dormant application was not applied, monitor leaf curl plum
aphid in spring along with mealy plum aphid. Follow the monitoring guidelines
in SPRING/SUMMER MONITORING to determine if treatment is necessary.
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, 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. Not all registered pesticides are listed. Always read label of product being used. |
|
DORMANT |
A. |
PHOSMET |
|
(Imidan) 70W |
2.12 lb |
1 lb |
3 days |
7 |
|
MODE OF ACTION GROUP NUMBER1: 1B |
|
COMMENTS:
Apply with a buffer to lower solution pH to 5.0. Apply as early as November 1st
even though all leaves may not be off trees. Has fewer impacts on beneficials
and water quality then other materials listed. This low-label rate and early
timing provide effective control and reduce the risk of runoff into
waterways, mitigating concerns of surface water pollution. Early applications
may not be effective for peach twig borer and are not effective for San Jose scale control. |
|
B. |
DIAZINON* 50WP |
1 lb |
0.5 lb |
24 |
21 |
|
4EC |
1 pt |
0.5 pt |
24 |
21 |
|
MODE OF ACTION GROUP NUMBER1: 1B |
|
COMMENTS:
Apply as early as November 1st even though all leaves may not be
off trees. This low-label rate and early timing provide effective control and
reduce the risk of runoff into waterways, mitigating concerns of surface
water pollution. Early applications may not be effective for peach twig borer and are not effective for San Jose scale control. |
|
C. |
ESFENVALERATE* |
|
(Asana XL) |
3 oz |
1.5 oz |
12 |
14 |
|
MODE OF ACTION GROUP NUMBER1: 3 |
|
COMMENTS:
Apply as early as November 1st even though all leaves may not be
off trees. This lower-than-label rate and early timing provide effective
control and reduce the risk of runoff into waterways, mitigating concerns of
surface water pollution. Pyrethroid residues remaining on bark will continue
to affect mite predators long after application, increasing potential for
spider mite infestations. Lower rates and/or early timing may not be
effective for peach twig borer and are not effective for San Jose scale control. |
|
DELAYED
DORMANT |
A. |
THIAMETHOXAM |
|
(Actara) |
3–4 oz |
0.75–1 oz |
12 |
14 |
|
MODE OF ACTION GROUP NUMBER1: 4A |
|
COMMENTS:
Direct treatment or residues on blooming crops and weeds are highly toxic to
bees. Remove (mow, disc, etc.) blooming ground cover before treatment. Apply
prebloom or postbloom but not from swollen bud to petal fall. Do not apply
less than 2 oz or more than 5.5 oz/acre/application or exceed 8
oz/acre/season. This chemical is listed on the EPA reduced risk to the
environment. Repeat applications of any neonicotinoid insecticide (imidacloprid-
Provado; thiamethoxam - Actara) can lead to resistance to all neonicotinoids. Alternate neonicotinoids with
an insecticide that has a different mode of action to help delay the development of resistance. |
|
B. |
PHOSMET |
|
(Imidan) 70W |
2.12 lb |
1 lb |
3 days |
7 |
|
MODE OF ACTION GROUP NUMBER1: 1B |
|
COMMENTS: Apply with a buffer to lower solution pH to 5.0. |
|
C. |
IMIDACLOPRID |
|
(Provado) 1.6F |
4–8 fl oz |
2 fl oz |
12 |
0 |
|
MODE OF ACTION GROUP NUMBER1: 4A |
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COMMENTS:
Repeat applications of any neonicotinoid insecticide (imidacloprid-
Provado; thiamethoxam - Actara) can lead to resistance to all neonicotinoids. Alternate neonicotinoids with
an insecticide that has a different mode of action to help delay the development of resistance. |
|
D. |
ESFENVALERATE* |
|
(Asana XL) |
3 oz |
1.5 oz |
12 |
14 |
|
MODE OF ACTION GROUP NUMBER1: 3 |
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COMMENTS:
Pyrethroid residues remaining on bark will continue to affect mite predators
long after application, increasing potential for spider mite infestations.
Lower rates may not be effective for peach twig borer or San Jose scale control. |
|
E. |
LAMBDA CYHALOTHRIN* |
|
(Warrior) |
2.56–5.12 fl oz |
0.64–1.28 fl oz |
24 |
14 |
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MODE OF ACTION GROUP NUMBER1: 3 |
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COMMENTS:
Residues remaining on bark may continue to affect mite predators long after application, increasing potential for spider mite infestations. |
|
BLOOM |
A. |
NARROW RANGE OIL# |
4 gal |
— |
4 |
0 |
|
MODE OF ACTION: Contact including smothering and barrier effects. |
|
COMMENTS:
Apply in 100 gal water/acre. Oil must contact aphids to provide control.
Apply at green tip or popcorn to kill the hatching aphids (hatch generally
occurs in early March). May be tank mixed with bloom time treatments aimed at
peach twig borer and brown rot. Make a second application 10 days later. This
usually coincides with full bloom in most years. Plum trees tolerate oil
treatments better in spring than during full dormancy. Do not apply oil
within 2 weeks of captan or within 30 days of a sulfur treatment. Not all oils are organically acceptable; be sure to check individual products. |
|
B. |
ENDOSULFAN* |
|
(Thionex) 50WP |
See comments |
4 |
7 |
|
MODE OF ACTION GROUP NUMBER1: 2A |
|
COMMENTS:
Label says use 1 lb/100 gallons water or 4–5 lb/acre. Cannot be applied in any situations where runoff may occur. |
|
SPRING |
A. |
DIAZINON* 50WP |
1.5–3 lb |
1 lb |
24 |
21 |
|
4EC |
1.5–3 pt |
1 pt |
24 |
21 |
|
MODE OF ACTION GROUP NUMBER1: 1B |
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COMMENTS:
Avoid drift and runoff into surface waters. Where plums are grown near waterways, do not use diazinon. |
|
B. |
NARROW RANGE OIL# |
6-8 gal |
— |
4 |
0 |
|
MODE OF ACTION: Contact including smothering and barrier effects. |
|
COMMENTS:
Apply in 200 gal water/acre. Oil must contact aphids to provide control.
Harmful to wasps that parasitize aphids. Plum trees tolerate oil treatments
better in spring than during full dormancy. Do not apply oil within 2 weeks
of captan or within 30 days of a sulfur treatment. Not all oils are organically acceptable; be sure to check individual products. |
|
C. |
NEEM OIL# |
|
(Trilogy) 70EC |
2% |
— |
12 |
0 |
|
MODE OF ACTION: Unknown. A botanical insecticide. |
|
COMMENTS: Repeat applications may be necessary. |
|
D. |
THIAMETHOXAM |
|
(Actara) |
3–4 oz |
0.75–1 oz |
12 |
14 |
|
MODE OF ACTION GROUP NUMBER1: 4A |
|
COMMENTS:
Direct treatment or residues on blooming crops and weeds are highly toxic to
bees. Remove (mow, disc, etc.) blooming ground cover before treatment. Apply
prebloom or postbloom but not from swollen bud to petal fall. May cause mite
outbreaks. Do not apply less than 2 oz or more than 5.5 oz/acre/application
or exceed 8 oz/acre/season. Repeat applications of any neonicotinoid insecticide (imidacloprid-
Provado; thiamethoxam - Actara) can lead to resistance to all neonicotinoids. Alternate neonicotinoids with
an insecticide that has a different mode of action to help delay the development of resistance. |
|
E. |
IMIDACLOPRID |
|
(Provado) 1.6F |
4–8 fl oz |
2 fl oz |
12 |
7 |
|
MODE OF ACTION GROUP NUMBER1: 4A |
|
COMMENTS:
Repeat applications of any neonicotinoid insecticide (imidacloprid-
Provado; thiamethoxam - Actara) can lead to resistance to all neonicotinoids. Alternate neonicotinoids with
an insecticide that has a different mode of action to help delay the development of resistance. |
|
SUMMER |
A. |
NEEM OIL# |
|
(Trilogy) 70EC |
2% |
— |
12 |
0 |
|
MODE OF ACTION: Unknown. A botanical insecticide. |
|
COMMENTS: Repeat applications may be necessary. Oil is harmful to parasitic wasps. |
|
B. |
NARROW RANGE OIL# |
6–8 gal |
— |
4 |
0 |
|
MODE OF ACTION: Contact including smothering and barrier effects. |
|
COMMENTS:
Apply in 200 gal water/acre. Oil must contact aphids to provide control. Oil
is harmful to wasps that parasitize aphids. Use a minimum of 6 to 8 gal of
oil in 200 gal water. Good coverage (slow tractor speed) is essential for
best results. Do not apply oil within 2 weeks of captan or within 30 days of
a sulfur treatment or when temperatures are expected to exceed 95°F. Not all oils are organically acceptable; be sure to check individual products. |
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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 Insects and Mites:
W. O. Reil, UC Cooperative Extension Solano/Yolo counties
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