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How to Manage Pests
UC Pest Management Guidelines
Grape
Grape Leaffolder
Scientific name: Desmia funeralis
(Reviewed 6/06,
updated 6/06)
In this Guideline:
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Moths of
the grape leaffolder are almost black, with two white spots on the forewings
and two white stripes across the abdomen. Larvae are translucent but appear
greenish because ingested leaf tissue shows through the body wall. Small black
spots, located above the second pair of legs, are present on later instar
larvae. This helps distinguish them from omnivorous
leafroller.
Grape leaffolders have three generations a
year (about April-May, June 15-July 15, and August). After overwintering as pupae,
moths emerge in April or May and lay flat, elliptical eggs singly on either the upper or lower surface of the leaf. Many are deposited
against the leaf veins on the underside of the leaf. After hatching, larvae
feed between two webbed leaves for about 2 weeks. Then each pale green,
translucent larva rolls a leaf edge and feeds from the inside on the leaf edge. Larvae turn darker green as a
result of this leaf feeding. If disturbed, larvae wriggle vigorously and drop
to the ground without a silken thread. Mature larvae construct a separate leaf envelope on the edge of a leaf in which they pupate.
Grape leafroller can reduce leaf surface by constructing leaf rolls and
by leaf feeding. Twenty percent leaf reduction can be tolerated 1 month after
fruit set in the San Joaquin Valley. Even more leaf
damage can be tolerated later. However, third generation damage can be severe enough
to cause complete defoliation,
which leads to sunburned berries, soft fruit, and direct berry feeding by
leaffolder larvae.
Parasites play an important role in keeping grape leaffolder below a
level that will cause damage. There seems to be no correlation between the past
season's population and the current season's first generation nor with the
population density that may develop later. Treatment of the first generation is
rarely needed. However, inspect and judge each brood as to its potential to
cause economic damage.
Biological Control
Several parasites attack grape leaffolder. Among the most common is the
larval parasite Bracon
cushmani. After stinging and paralizing leaffolder larvae, female B.
cushmani lay from one to several eggs on
the body of leaffolder larvae. Bracon cushmani larvae feed externally and, after completing their development, pupate next to the consumed host. Parasitism by this parasite frequently reduces
second and third generation populations to below economic levels. In addition
to B. cushmani, several other hymenopteran parasites and at least
two species of flies parasitize leaffolder. Generalist predators such as lacewings and
spiders also attack grape leaffolder larvae.
Organically Acceptable
Methods
Biological control and sprays of Bacillus thuringiensis and the Entrust formulation of spinosad are organically acceptable methods.
Monitoring
and Treatment Decisions
Grape leaffolder can be
monitored along with other pests following the procedures in MONITORING
CATERPILLARS. If grape
leaffolders are present in the vineyard or have been a problem in the past,
plan to treat at bloom. Otherwise, monitor for the characteristic group feeding
of young larvae between leaves. As larvae begin making rolls, examine the
vineyard every 2 to 3 days to detect a greater than expected increase. Record
results on a monitoring form .
Unroll leaves to check for parasitism. Populations tend to be spotty
and defoliation of a few vines used for raisin or wine grapes can probably be
tolerated; however, table grape should probably be treated. If treatment is
warranted, treat as soon as a few rolls are noticed from the generation being treated
because small larvae are more easily killed than older instars. Usually
treatments applied for grapeleaf skeletonizer and omnivorous leafroller will
also control grape leaffolder.
| Common name |
Amount/Acre** |
P.H.I.+ |
| (trade name) |
|
(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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| A. |
CRYOLITE |
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(Kryocide) 96WP |
6–8 lb |
30 |
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(Prokil Cryolite) 96 |
6–8 lb |
30 |
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MODE OF ACTION: An
inorganic (Group 9A)1 insecticide.
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COMMENTS: Restricted
entry interval: 12 hours. Wine, table, and raisin: 2
applications maximum. Ground application only. If used on wine grapes or
grapes that may be sold to a winery for export, observe their restrictions on
applications. Cryolite is a stomach poison that must be ingested by the
leaffolder to be effective so good coverage is essential and best timing is before leaf rolling begins. Do not apply more than 20 lb/acre/year. |
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| B. |
SPINOSAD |
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(Entrust)# |
1.25–2.5 oz |
7 |
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(Success) |
4–8 oz |
7 |
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MODE OF ACTION: A
microbial (Group 5)1 insecticide.
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COMMENTS: Restricted
entry interval: 4 hours. Apply when eggs first hatch to target the young
larvae. A stomach poison; most effective when ingested. Heavy infestations
require a second application in 4 or 5 days. to protect honeybees, apply only
during late evening, night, and early morning when bees are present in the vineyard. |
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| C. |
METHOXYFENOZIDE |
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(Intrepid) 2F |
10–16 fl oz |
30 |
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MODE OF ACTION: An
insect growth regulator (Group 18)1 insecticide.
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COMMENTS: Restricted
entry interval: 4 hours. An insect growth regulator that affects
lepidopterous larvae only. Must be ingested; most effective when applied to young caterpillars. |
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| D. |
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: Restricted
entry interval: 4 hours. Only effective against young larvae. A stomach
poison that must be ingested by the leaffolder to be effective; good coverage
is essential. Has a short residual so is most effective when applied 3 or 4 days before leaf rolling by the main brood. |
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| E. |
METHOMYL* |
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(Lannate LV) |
0.75–1.5 qt |
Raisin/Table: 1 |
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(Lannate) 90SP |
0.5–1 lb |
Wine: 14 |
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MODE OF ACTION: A
carbamate (Group 1A)1 insecticide.
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COMMENTS: Restricted
entry interval: Check with county agricultural commissioner. Do not feed treated
grapes to livestock. Disruptive to predators of mites, parasites of leafhopper and may contribute to mealybug outbreaks as well. |
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| F. |
CARBARYL* |
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(Sevin) 80S |
1.25–2.5 lb |
7 |
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(Sevin) 10% Dust |
20–25 lb |
7 |
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MODE OF ACTION: A
carbamate (Group 1A)1 insecticide.
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COMMENTS: Restricted
entry interval: 12 hours. May encourage mite outbreaks; do not use where mites are a chronic problem. |
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UC IPM Pest Management Guidelines: Grape
UC ANR Publication 3448
Insects and Mites
W. J. Bentley, UC IPM Program, Kearney Agricultural Research Center, Parlier
L. G. Varela, UC IPM Program, Sonoma County
F. G. Zalom, Entomology, UC Davis
R. J. Smith, UC Cooperative Extension, Sonoma County
A. H. Purcell, Environmental Science, Policy and Management, UC Berkeley
P. A. Phillips, UC IPM Program, Ventura County
D. R. Haviland, UC IPM Program, Kern County
K. M. Daane, Kearney Agricultural Research Center, Parlier
M. C. Battany, UC Cooperative Extension, San Luis Obispo County
Acknowledgment for contributions to the insects and mites section:
J. Granett, Entomology, UC Davis
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