In this Issue:

VEGETABLE NEWS

Vegetable Insect Update

GRAPE NEWS

Grape Flea Beetle, Grape Berry Moth, and Multicolored Asian Lady Beetle

STRAWBERRY NEWS

Those Delicious, Risky Strawberries

Strawberry Sampling Data from MDA and Grower Cooperators

APPLE NEWS

Apple Pest Profile: Obliqubanded Leafroller

Apple Scab Infections

Weekly Trap Counts

Insect, Pest Fact Sheets

Apple Pest Profile: Obliquebanded Leafroller (Choristoneura rosaceana)  

From MDA’s IPM Manual for Minnesota Apple Orchards, June 2003

 Obliquebanded leafroller (OBLR) is beginning to show up in pheromone traps throughout the MN apple growing regions. OBLR is an important pest of apple in Minnesota. Native to North America, OBLR attacks apple, pear, cherry, plum, peach, rose, raspberry, gooseberry, currant, strawberry, blueberries, and many weeds. Historically, commercial apple growers in North America have rarely needed to manage OBLR in their orchards. However, periodic outbreaks probably representing secondary pest resurgence, and recent changes in pesticide regulations have raised the status of this pest in many regions. The result is that OBLR is now being monitored by many growers in the United States. This trend is likely to continue as growers reduce the use of broad-spectrum insecticides and time applications more accurately for codling moth and other internal fruit feeders. There are two generations of OBLR per year in Minnesota.

Biology

OBLR overwinter as immature larvae in cocoons on tree bark. The overwintered OBLR larvae resume activity early in the spring. First generation moths start to appear around the end of May (about 490 degree day base 50ºF). The females mate and lay green egg masses. Larvae undergo six developmental stages (or instars). The pupae are usually found in rolled leaves on the tree or on tree bark. Development from egg to adult in orchards may take up to six weeks or more.

Damage

Although damage is primarily to leaves, OBLR (like other leafrollers) does its most serious damage when it attacks fruit. Upon resumption of activity in the spring, overwintered larvae feed on developing buds webbing leaves and floral parts together, hence the name leafroller. Larvae continue to feed on the flowers during bloom and on developing fruit after petal fall. At that time, they begin to feed on both the fruit and the rapidly expanding leaves. They gouge deeply into young fruit. Fruit damage increases as the remaining large larvae feed more on fruit as the season progresses. The most severe damage occurs after petal fall. The larger the fruit before it is damaged, the more likely it is to develop and remain on the tree. In late July, larvae of the summer generation can be found on actively growing terminals inside the canopy and on terminal and older leaves near fruit clusters.

Management

Monitoring: Pheromone traps are available for monitoring OBLR adults. Between 1999 and 2002, studies were conducted to determine the identity of the OBLR population in Minnesota. The results show that the pheromone blend produced by the western strain of OBLR captured a significantly higher number of males than the blend produced by the eastern strain, indicating that the Minnesota populations of OBLR are more related to the western strain. However, trap catch data are unreliable for indicating when sprays are needed as no action thresholds are currently available for the adult stage of this pest.

Sampling for OBLR larvae and infestation should begin at the early petal fall stage. Check five trees, examining 20 bud clusters per tree. On each tree, look for larvae or larval feeding on six clusters on the outside of the tree, six clusters in the center of the tree and eight clusters near the treetop. Treatment is recommended if you find an average of two or more larvae or fresh feeding sites per tree. Pheromone traps should be used to determine when emergence of the summer brood starts; then each week, examine 10 fruit clusters and 10 terminals in the outside, center, and top of five trees per orchard. Treatment is recommended if there is an average of three or more larvae per tree. Michigan State University has developed a degree day (DD) model for OBLR development (Table 1).

Chemical control: Broad-spectrum insecticides will control OBLR in the larval and adult stages. Sprays applied at pink stage or petal fall will prevent damage from the overwintered larvae. In some states, OBLR has become resistant to some pesticides, including organophosphates, so chemicals with a different mode of action may be required to control it. At this time, there are no reports of resistance of

OBLR to pesticides used for its control in Minnesota. Growers should try new materials such as Spintor on leafrollers if they go over threshold. Integrating some of the new pesticides and insect growth regulators (IGR’s) will slow down the development of pesticide resistance.

Other control options: Other materials available for managing OBLR include pheromone mating disruption and application of kaolin spray (Surround). Phermone formulations are commercially available for mating disruption of leafrollers. OBLR pheromone dispensers should be applied before the start of the first flight in June.

Table 1. Development of obliquebanded leafroller*
(Michigan State University model)

Return to index

Co-Editors: Bill Hutchison ( hutch002@umn.edu), Department of Entomology, University of Minnesota, Jeanne Ciborowski, Minnesota Department of Agriculture, Ag. Resources Management and Development Division, and Suzanne Wold-Burkness ( woldx018@umn.edu), Department of Entomology, University of Minnesota

The Newsletter is published weekly from May through August, cooperatively, by the Minnesota Department of Agriculture (MDA) and the University of Minnesota (U of MN). Reports are posted on the U of MN and MDA web sites on Fridays. If you have suggestions and/or comments, please send your contributions by 4 p.m., Wednesday to Jeanne Ciborowski, 651-297-3217, jeanne.ciborowski@state.mn.us , MDA, 90 W. Plato Blvd., St. Paul, MN 55107-2094. You can access the Newsletter at the U of MN web site in htm format at: www.vegedge.umn.edu/MNFruit&VegNews/mnindex.htm and at the MDA web site in pdf format at: www.mda.state.mn.us/biocon/fruitreports/

Partial funding for this publication is provided through partnership agreements with the Minnesota Fruit and Vegetable Growers Association (MFVGA) and the United States Department of Agriculture – Risk Management Agency (RMA). These institutions are equal opportunity providers.

DISCLAIMER

Reference to products in this publication is not intended to be an endorsement to the exclusion of others which may have similar uses. Any person using products listed in this publication assumes full responsibility for their use in accordance with current manufacturer directions.

The University, including the Minnesota Extension Service, is an equal opportunity educator and employer. ©1999-2004 Minnesota Extension Service, University of Minnesota. All rights reserved. Contact copyright@extension.umn.edu for information on reproduction or use of this material.