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UC Pest Management Guidelines


Grape leaffolder, Desmia funeralis, larva.

Grape

Grape Leaffolder

Scientific name: Desmia funeralis

(Reviewed 6/06, updated 10/08)

In this Guideline:


DESCRIPTION OF THE PEST

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.

DAMAGE

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.

MANAGEMENT

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 (example form128 KB, PDF).

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 grapes 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.

At harvest check table grapes for grape leafroller damage to assess your management program and prepare for next year.

Common name Amount/Acre** R.E.I.+ P.H.I.+
(trade name)   (hours) (days)
 

  Calculate impact of pesticide on air quality
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. Not all registered pesticides are listed. Always read label of product being used.
 
A. CRYOLITE
  (Kryocide) 96WP 6–8 lb 12 30
  (Prokil Cryolite) 96 6–8 lb 12 30
  MODE OF ACTION GROUP NUMBER1: 9A
  COMMENTS: 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.
 
B. SPINOSAD
  (Entrust)# 1.25–2.5 oz 4 7
  (Success) 4–8 oz 4 7
  MODE OF ACTION GROUP NUMBER1: 5
  COMMENTS: 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.
 
C. METHOXYFENOZIDE
  (Intrepid) 2F 10–16 fl oz 4 30
  MODE OF ACTION GROUP NUMBER1: 18A
  COMMENTS: An insect growth regulator that affects lepidopterous larvae only. Must be ingested; most effective when applied to young caterpillars.
 
D. BACILLUS THURINGIENSIS ssp. KURSTAKI#
  (various products) Label rates 4 0
  MODE OF ACTION GROUP NUMBER1: 11.B2
  COMMENTS: 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.
 
E. METHOMYL*
  (Lannate) LV 0.75–1.5 qt 7 days Raisin/Table: 1
  (Lannate) 90SP 0.5–1 lb 7 days Wine: 14
  MODE OF ACTION GROUP NUMBER1: 1A
  COMMENTS: Do not feed treated grapes to livestock. Disruptive to predators of mites, parasites of leafhopper and may contribute to mealybug outbreaks as well.
 
F. CARBARYL*
  (Sevin) 80S 1.25–2.5 lb 12 7
  (Sevin) 10% Dust 20–25 lb 12 7
  MODE OF ACTION GROUP NUMBER1: 1A
  COMMENTS: May encourage mite outbreaks; do not use where mites are a chronic problem.
 
** Apply with enough water to provide complete coverage.
+ Restricted entry interval (R.E.I.) is the number of hours (unless otherwise noted) from treatment until the treated area can be safely entered without protective clothing. Preharvest interval (P.H.I.) is the number of days from treatment to harvest. In some cases the REI exceeds the PHI. The longer of two intervals is the minimum time that must elapse before harvest.
* Permit required from county agricultural commissioner for purchase or use.
# Acceptable for use on organically grown produce.
1 Rotate chemicals with a different mode-of-action Group number, and do not use products with the same mode-of-action Group number more than twice per season to help prevent the development of resistance. For example, the organophosphates have a Group number of 1B; chemicals with a 1B Group number should be alternated with chemicals that have a Group number other than 1B. Mode of action Group numbers are assigned by IRAC (Insecticide Resistance Action Committee). For additional information, see their Web site at http://www.irac-online.org/.

IMPORTANT LINKS

[Precautions]

PUBLICATION

[UC Peer Reviewed]

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 Insects and Mites:
J. Granett, Entomology, UC Davis

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