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How to Manage Pests
UC Pest Management Guidelines
Apple
San
Jose Scale
Scientific name: Diaspidiotus (= Quadraspidiotus) perniciosus
(Reviewed 8/06,
updated 8/06)
In this Guideline:
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Female San Jose scales give birth to living young that emerge from
under the edge of the scale covering. These tiny yellow crawlers wander in a random fashion until they find a suitable place to settle.
Immediately upon settling, the crawlers insert their mouthparts into the host
plant and begin feeding and secreting a white waxy material (white cap stage); eventually the waxy covering turns black and is known as the black cap stage. Later the covers turn various shades from gray to black.
San Jose scales overwinter predominantly in the black cap stage,
although in mild years some adult mated females may also survive. In late
January, these nymphs resume their growth. Immature male and female scales are
indistinguishable until the first molt. At this time, the male scale covering
begins to elongate, while the female's remain circular. Males molt a total of
four times. Following the final molt, adult male scales emerge from the scale covering as tiny, yellow winged insects. They mate
with the females who remain under the scale covering. After about 2 months,
crawlers begin to emerge from the females, usually in April; peak emergence is
generally in early May. There are usually four generations a year. Summer
generations overlap and crawlers are present throughout summer and fall.
If heavy scale infestations are left unchecked, trees may be
seriously damaged, resulting in reduced vigor, thin foliage, cracked or dying branches,
and the eventual death of the tree. Young trees may be killed before fruiting.
Infested fruit develop a reddish purple ring surrounding each spot where a scale settles.
San Jose scale is the most common and the most damaging of the
scales found in apple orchards. Dormant season treatments are the key to
controlling this pest. The only other effective treatment time is in May.
Natural enemies can contribute significantly to control when not disrupted by
insecticides.
Biological Control
Natural
enemies that feed on San Jose scale include two predaceous beetles: the twicestabbed
lady beetle,
Chilocorus orbus, and another
small beetle, Cybocephalus
californicus. A number of small chalcid
and aphelinid wasps parasitize this scale. These predators and parasites may be helpful in reducing
scale populations, but insecticides used during the growing season for other
pests can disrupt this natural control and scale populations increase rapidly.
Organically Acceptable Methods
Biological
control and approved oil sprays are organically acceptable methods, but San
Jose scale is rarely a pest in organic orchards.
Monitoring and Treatment Decisions Degree-day calculator Degree-day table
Monitor for San Jose scale during the dormant period by checking
prunings to make sure scale hasn't developed in tree tops. Also check fruit at
harvest for the presence of scale.
Due to the damage potential of this pest, annual dormant sprays
are recommended in most areas. Oil sprays work the best on the black cap stage,
so apply them in early January. Control heavy populations of San Jose scale by
applying an insecticide plus oil spray during the delayed dormant period.
If inadequate control is achieved with the dormant spray,
treatments are also effective when applied soon after the emergence of the
crawlers in May. Use pheromone traps in
March to monitor for male San Jose scale flights and double-sided sticky tape
for monitoring crawlers in April and May. Time a treatment, using a 51°F lower
threshold and 90°F upper threshold, for 600 to 700 DD after the beginning of
the male flight or 200 degree-days after crawler emergence begins.
| Common name |
Amount to Use |
P.H.I.+ |
| (trade name) |
(conc.) |
(dilute) |
(days) |
|
| When choosing a pesticide, consider
information relating to the impact on natural
enemies and honey bees and
environmental impact.
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| DORMANT |
| A. |
NARROW RANGE OIL# |
6 gal |
1.5 gal |
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MODE OF ACTION: Contact including smothering and barrier effects. |
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COMMENTS: Check with certifier to determine which products are organically acceptable. |
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| DELAYED DORMANT
|
| A. |
NARROW RANGE OIL |
6 gal |
1.5 gal |
|
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MODE OF ACTION: Contact including smothering and barrier effects. |
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. . . PLUS . . . |
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PYRIPROXYFEN |
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(Esteem) 0.86EC |
Label rates |
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(Seize) 35WP |
4-5 oz |
— |
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MODE OF
ACTION: An insect growth regulator (Group 7C)1 insecticide.
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COMMENTS: Apply from delayed dormancy through pink bud. |
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. . . OR . . . |
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CHLORPYRIFOS* |
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(Lorsban) 4EC |
Label rates |
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MODE OF ACTION: An organophosphate (Group
1B)1 insecticide.
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COMMENTS: Avoid drift and tailwater runoff
into surface waters or choose alternative materials. Chlorpyrifos has been
found in surface waters at levels that violate federal and state water quality standards. |
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. . . OR . . . |
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ESFENVALERATE |
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(Asana XL) |
Label rates |
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MODE OF ACTION: A pyrethroid (Group 3)1
insecticide.
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| B. |
METHIDATHION* |
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(Supracide) 2EC |
6–12 pt |
0.75–1.5 pt |
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MODE OF ACTION: An organophosphate (Group
1B)1 insecticide.
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COMMENTS: Apply before blossoms open or injury may occur. |
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| CRAWLER TREATMENT |
| A. |
DIAZINON* 50WP |
4 lb |
0.75–1 lb |
21 |
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MODE OF ACTION: An organophosphate (Group
1B)1 insecticide.
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COMMENTS: Avoid drift and tailwater runoff into surface waters or choose alternative materials. |
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| B. |
NARROW RANGE OIL# |
6 gal |
1.5 gal |
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MODE OF ACTION: Contact including
smothering and barrier effects. Check with certifier to determine which products are organically acceptable. |
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UC IPM Pest Management Guidelines: Apple
UC ANR Publication 3432
Insects and Mites
J. L. Caprile, UC Cooperative Extension, Contra Costa County
L. R. Wunderlich, UC Cooperative Extension, El Dorado County
P. M. Vossen, UC Cooperative Extension, Sonoma and Marin counties
W. W. Coates, UC Cooperative Extension, San Benito County
H. L. Andris, UC Cooperative Extension, Fresno County
L. G. Varela, UC IPM Program, Sonoma County
W. J. Bentley, UC IPM Program, Kearney Agricultural Center, Parlier
Acknowledgment for contributions to the insects and mites section:
C. Pickel, UC IPM Program, Sutter and Yuba counties
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