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How to Manage Pests
UC Pest Management Guidelines
Apple
Omnivorous
Leafroller
Scientific name: Platynota
stultana
(Reviewed 8/06,
updated 8/06)
In this Guideline:
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Omnivorous leafroller larvae are light-colored
caterpillars with dark brown or black heads. When mature, they are about 0.6 inch (1.5 cm)
long and have two slightly raised, oblong, whitish spots on the upper surface
of each abdominal segment. Abdominal segments may have a greenish brown tinge.
Larvae pupate inside a webbed shelter. Adults of the overwintering generation
emerge in March. They are small,
dark brown moths,
0.38 to 0.5 inch (9-12 mm) long with a dark band on the wing and a long snout. Eggs are
laid in overlapping rows that resemble fish scales. The first generation of
eggs usually is laid on weed hosts, and adults from this generation emerge in
May or June to lay eggs in orchards on leaves and fruit. Larvae have the
characteristic behavior of wriggling backward when disturbed and dropping from
a silk thread attached to the leaf or fruit surface.
This
pest has two to four generations per year depending on climatic conditions.
Omnivorous leafrollers are more common in interior valleys and southern
California mountain orchards, especially those next to vineyards, than in
orchards in coastal areas or at higher elevations of the Sierra Foothills.
Omnivorous leafroller larvae often web leaves into rolled protective
shelters while feeding. They feed on leaves and on the surface of fruit,
sometimes webbing one or more leaves to the fruit for protection. They chew shallow
holes or grooves in the fruit surface, often near the stem end. The damage is
similar to that caused by orange tortrix. Larvae feed where fruit are touching,
so entire clusters can be damaged.
Omnivorous leafrollers commonly develop on host plants outside the
orchard and move into the orchard in early summer. Infestations often are
spotty, making monitoring difficult. Throughout the season, watch for
leafrollers when monitoring other pests.
Biological
Control
A number of parasites, including species of Macrocentrus,
Cotesia (Apanteles), and Exochus, attack
omnivorous leafroller larvae. General predators such as lacewings, Phytocoris, assassin
bugs,
and minute pirate bugs may
feed on eggs and larvae. Preservation of natural enemy populations is an
important part of keeping leafroller numbers low. Use selective materials that
are least disruptive of biological control when treating other pests.
Cultural Control
Remove fruit mummies and destroy both the fruit and
potential overwintering weed hosts, such as horseweed, common lambsquarters, little mallow, curly dock, and legumes, by clean cultivation.
Organically Acceptable
Methods
Biological and cultural control along with applications of Bacillus
thuringiensis and the Entrust formulation of spinosad are organically
acceptable.
Monitoring
and Treatment Decisions Degree-day calculator
Degree-day table
Begin monitoring by placing pheromone
monitoring traps in the orchard by mid-February in the San Joaquin Valley to establish the
biofix for the first flight; biofix is the first night moths are consistently
caught in traps over the period of several nights. First generation omnivorous leafrollers
are most likely to appear on weeds or cover crop; treatments for this first
brood are probably not necessary and are likely to be ineffective. From the
first biofix, accumulate degree-days (DD) to estimate what the onset of the
second flight will occur. Use a lower threshold of 48°F and an upper threshold of 87°F. (For assistance in calculating degree-days, see "Degree-days " on the UC IPM Web site). It takes about 1168 DD for omnivorous leafroller
to develop from egg to adult. As the start of the second flight nears, be sure
to have fresh trap liners and lures in place. When the second flight biofix is
determined by trap catches, begin accumulating degree-days. Research in the central
San Joaquin Valley indicates that the optimum single treatment timing is
between 700 and 900 DD after the start of the flight. Monitor the fruit closely
for signs of damage. No treatment threshold values are available.
| Common name |
Amount to Use |
P.H.I.+ |
| (trade name) |
(conc.) |
(dilute) |
(days) |
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| When choosing a
pesticide, consider information relating to the impact
on natural enemies and honey bees and environmental impact.
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| A. |
SPINOSAD |
| |
(Entrust)# |
2-3 oz |
0.5-0.75 oz |
7 |
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(Success) |
6–10 fl oz |
2–3.3 fl oz |
7 |
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MODE
OF ACTION: A microbial (Group 5)1 insecticide.
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COMMENTS: To prevent
the development of resistance to this product, rotate to a material with a
different mode of action after treating two consecutive generations. Do not
apply more than 3 sprays/season directed at leafrollers. Do not apply more than 9 oz/acre/crop of Entrust or 29 fl oz of Success/acre/crop. |
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| B. |
BACILLUS THURINGIENSIS ssp. KURSTAKI# |
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(various products) |
Label rates |
— |
0 |
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MODE OF ACTION: A microbial
(Group 11.B2)1 insecticide.
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COMMENTS: Least
harmful to beneficials. Bt is a stomach poison and must be consumed by the
leafroller; therefore it is most effective when applied during warm, dry
weather when larvae are actively feeding. Most effective against young
larvae. Requires more than 1 treatment; apply second application 7–10 days after first. |
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| C. |
METHOXYFENOZIDE |
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(Intrepid) 2F |
16 fl oz |
— |
14 |
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MODE OF ACTION: An
insect growth regulator (Group 18)1 insecticide.
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COMMENTS:
Functions both as an ovicide (when applied to eggs and when eggs are laid on
residues) and as a larvicide (must be ingested to be effective). For each
generation, begin applications at early egg hatch before webbing and
sheltering begin. Make a second application in 10–14 days. Spray coverage is
extremely important. Ground application should use 200 gal water/acre with a
sprayer speed of 1.5 mph. The addition of a spray adjuvant is recommended to enhance spray coverage. |
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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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