How to Manage Pests
UC Pest Management Guidelines
Pistachio
Soft Scales
Scientific names:
Brown soft scale: Coccus hesperidium
Black scale: Saissetia oleae
Frosted scale: Parthenolecanium pruinosum
European fruit lecanium: Parthenolecanium corni
(Reviewed 2/07,
updated 2/07)
In this Guideline:
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DESCRIPTION OF THE PESTS
The brown soft scale is a mottled, yellow-brown color when young,
becoming darker at maturity. It has three to five generations per year and is
often found on the nut. It is flattened and elongated, resembling a football
sliced in half. It is about 0.13 inch in length.
The black scale is
dark brown to black, later becoming more mottled black and brown. It has an
H-shaped ridge on the dorsum. There is generally only one generation per year
in the Central Valley. However, in some years two generations have been
detected.
The frosted scale is
elongated, slightly humped, and has a waxy, white frostlike coating in spring.
It is about 0.25 inch in length at maturity and has one generation per year. It
is found in the warmer interior growing areas.
The European fruit
lecanium is identical to the frosted scale but does not have the frosted coating. High
temperatures early in summer will increase mortality of immature stages of
European fruit lecanium.
Soft scales molt twice
before they reach maturity. The stage just before the adult is frequently
referred to as the rubber stage. In this stage, the scales remain soft,
somewhat translucent and are still susceptible to parasitism. Upon molting to
adults, the shell hardens and becomes opaque.
DAMAGE
In spring, soft scales produce heavy amounts of honeydew, which can
affect photosynthesis by providing a substrate on which sooty mold grows. Moderate-to-high scale populations can
also retard shoot growth and shell splitting. Scales are most common on
vigorously growing trees.
MANAGEMENT
These scales are normally kept under control by native parasites.
Because of the increase in the use of permethrin treatments for true bugs in
pistachio, natural enemies of scales are more frequently destroyed, and soft
scales are becoming more prevalent.
Biological Control
There are a number of effective parasites of these soft scales. Most are
tiny parasitic wasps in the genus Metaphycus. Metaphycus luteolus destroys the scale in its
early instars before it can reproduce or cause substantial injury. This
parasite produces several generations during each scale generation. In
addition, predators, including the predaceous lady beetle,
Rhyzobius (Lindorus) lophanthae, prey on
these scales.
There is a strong
relationship between Phytocoris plant bugs and populations of soft scales. Where Phytocoris plant bugs
are plentiful, scale populations are commonly low. During March and April,
immature adult soft scales and eggs are a primary food source for Phytocoris. In fall, Phytocoris feeds on
second-instar scales that are migrating from the leaves to the woody shoots.
Organically Acceptable Methods
Biological control and oil sprays in the dormant period are acceptable
for use in an organically certified crop.
Monitoring and Treatment Decisions
In early to mid-January,
examine one-year-old fruiting wood for live and parasitized scale. Look at
12-inch dormant shoots that are randomly selected from throughout the
orchard. A light-to-moderate
population in early February would be an average of one to five live scale per
inch of fruiting wood; a heavy population would be an average of 10 or more
live scale per inch. Other factors
to consider when making treatment decisions are the age, vigor, and split nut
percentages. Apply a dormant
treatment from mid-November through February before the scales reach the rubber
stage of development. For optional control, treat frosted scale before its waxy
coating develops, and treat European fruit lecanium before it reaches the
rubber stage in late February.
Depending upon weather
conditions and scale pressure, re-treatment may not be necessary for 3 to 5
years.
| Common name |
Amount/Acre** |
R.E.I.+ |
P.H.I.+ |
| (trade name) |
|
(hours) |
(days) |
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| When choosing a
pesticide, consider information relating to impact
on natural enemies and honey bees, impact of the timing on beneficials, and environmental impact Not all registered pesticides are listed. Always read label of product being used.
|
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| A. |
NARROW RANGE OIL# |
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(Omni Supreme Spray) |
6 gal |
4 |
0 |
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4–6 gal |
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MODE OF ACTION: Contact including smothering and barrier effects. |
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COMMENTS:
No more than 6% v/v solution permitted as a concentrate. Oil application can advance bud break
by 7 to 10 days. Treatments made in Nov.-Dec. have a minimal effect on bloom timing. |
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| B. |
CARBARYL* |
| |
(Sevin) 80S |
5–6.25 lb |
12 |
14 |
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(Sevin) XLR Plus |
4–5 qt |
12 |
14 |
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MODE
OF ACTION: A carbamate (Group 1A)1 insecticide.
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...PLUS... |
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NARROW RANGE OIL |
4–6 gal |
4 |
0 |
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MODE OF ACTION: Contact including smothering and barrier effects. |
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COMMENTS:
Best results are obtained with the addition of the oil to the spray for high
populations. Moderate
populations have been successfully controlled with oil alone. When dormant
oil is applied in January or February, trees bloom somewhat earlier in
spring, and they become more susceptible to frost damage. If dormant oil
applications are made earlier (Nov.–Dec.), the effect on bloom timing is minimized. |
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UC IPM Pest Management Guidelines: Pistachio
UC ANR Publication 3461
Insects and Mites
W. J. Bentley, Kearney Agricultural Center, Parlier
R. H. Beede, UC Cooperative Extension, Kings County
K. M. Daane, Biological Control, UC Berkeley/Kearney Agricultural Center, Parlier
D. R. Haviland, UC Cooperative Extension, Kern County
Acknowledgment for contributions to Insects and Mites:
R. E. Rice, Kearney Agricultural Center, Parlier
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