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Project description

Importance of Bracon cushmani in the suppression of obliquebanded leafroller. (06BC014)
Program UC IPM competitive research grants program
Principal
investigator
K.M. Daane, Environmental Science, Policy, and Management, UC Berkeley
Host/habitat PistachiosıAlmondıApplesıPearsıWalnutsıBerriesıNut TreesıTree Fruits
Pest Obliquebanded leafroller Choristoneura rosaceana
Discipline Entomology
Review
panel
Biological Controls
Start year (duration)  2006 (Two Years)
Objectives Study life history traits of Bracon cushmani (Hym. Bracondiae) to determine its potential as a parasitoid of obliquebanded leafroller (Lep. Tortricidae).

Test the augmentative release of Bracon cushmani in pistachio orchards.

Project
Summary
Obliquebanded leafroller (Lep.: Tortricidae) is a widely distributed, polyphagous pest. Parasitoids provide some suppression, however, parasitoid effectiveness and species composition vary among regions and crop systems. We found that a newly associated parasitoid, Bracon cushmani (Hym.: Braconidae), can suppress obliquebanded leafroller in pistachio. Bracon cushmani is a well-known parasitoid of the grape leafroller, although little is know about its biology. We will study the parasitoid's life history traits to determine its potential as a biological control agent. Information on temperature development will be used to compare parasitoid efficiency in different crop systems. We will test inoculative releases as a control method using developed insectary colonies.
Second-year
progress
California pistachios are attacked by a variety of insect pests. Recent crop loss from navel orangeworm and obliquebanded leafroller larvae has redirected management decisions and insecticide applications to these moth pests. To improve available control tools, we are studying a parasitoid of the obliquebanded leafroller -- a braconid wasp (Bracon nr sp. cushmani). In some pistachio orchards this parasite provides excellent obliquebanded leafroller control. Initial results from laboratory studies show Bracon prefers larger OBLR larvae (3rd to 5th instars). Each parasitoid deposited about 140 eggs (range 110-214) over a 22-day oviposition period (range: 14-34 days). The parasitoid develops from egg to adult in about 10 to 12 days, with the pupal stage requiring the longest period. In the field, parasitized OBLR are very evident because the eggs and larvae develop externally, and the parasitized moth larva remains on the pistachio leaf. Most eggs are laid during the two weeks of the adult's life. We are using this information to determine how to best manipulate the parasitoid in the field. Initial augmentation trials in a commercial pistachio block released 150 adult Bracon per acre in July. Parasitism within three weeks of the release was high (greater than 60%), with the remaining OBLR dead. Studies in 2008 will determine if this beneficial wasp can establish and overwinter in the pistachio orchard, resulting in lowered obliquebanded leafroller densities.

First-year
progress
California pistachios are attacked by a variety of insect pests. Recent crop loss from navel orangeworm and obliquebanded leafroller larvae has redirected management decisions and insecticide applications to these moth pests. To improve available control tools, we are studying a parasitoid of the obliquebanded leafroller -- a braconid wasp (Bracon nr sp. cushmani). While commonly known as a parasitoid of the grape leafroller in vineyards, in some pistachio orchards this parasite provides excellent obliquebanded leafroller control, as well. Initial results from laboratory studies, show Bracon prefers larger OBLR larvae (3rd to 5th instars). Each parasitoid deposited about 140 eggs (range 110-214) over a 22-day oviposition period (range: 14-34 days).

The parasitoid develops from egg to adult in about 10 to 12 days, with the pupal stage requiring the longest period. In the field, parasitized OBLR are evident because the eggs and larvae develop externally, and the parasitized moth larva remains on the pistachio leaf. Most eggs are laid during the two weeks of the adult's life. We are using this information to determine how to best manipulate the parasitoid in the field. Initial augmentation trials in a commercial pistachio block released 1,000 adult Bracon per acre in June and July. We were able to recover the parasitoid in August and September collections. Collections in 2007 will determine if this beneficial wasp can establish and overwinter in the pistachio orchard -- resulting in lowered obliquebanded leafroller densities.

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