MN Fruit & Vegetable IPM News - Vol. 3, No. 5

The dogwood borer (DWB) is a native pest of apple and other fruit crops in North America . It has only one generation in Minnesota (June-early September). In addition to DWB, the closely-related apple bark borer (ABB), Synanthedon pyri, may also occur in Minnesota orchards.

The adult dogwood borer is black with yellow markings and clear wings. Body length is about 10 mm with a wingspan of 20 mm. In the female, the entire fourth abdominal segment is yellow, while this segment is black with a narrow yellow ring in the male. Eggs are small, oval, light brown with a hexagonal pattern of slightly raised lines. They are laid singly on tree trunks. Larvae are white to cream colored with a reddish head capsule and about 15 mm long when mature. DWB overwinter as larvae in feeding tunnels on tree trunks. The larvae resume activity in the spring. Pupae are brown, about 10 mm long, and enclosed in a silken cocoon covered with frass. Pupal cases are found in the feeding tunnel covered with bits of frass, often remaining at the entrance of the feeding tunnel after adult emergence.

Larvae feed on burr knot tissue in the trunk. This type of feeding is characterized by the presence of brown frass on the surface of infested tree trunks. The dogwood borer rarely attacks a healthy tree with smooth undamaged bark. Injury is commonly observed on size-controlled rootstocks with burr knots (aggregations of root initials) or a heavily callused graft union. This explains why damage is more common in dwarf plantings. It is easy to confuse adults and larvae of DWB and ABB. DWB has a crown of yellow hairs at the back of the head while ABB has mostly dark hairs at this spot. Also, DWB has tufts of black hairs bordered with yellow on the terminal segment, which is completely black in ABB.

Pheromone traps are available for monitoring adult flight.

Male DWB

DWB damage

DWB damage

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ACKNOWLEDGEMENTS

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 Jean Ciborowski, 651-201-6217, jeanne.ciborowski@state.mn.us, MDA, 625 Robert St. North, St. Paul, MN 55155-2538. 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: http://www.mda.state.mn.us/ipm/ipmnews/

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.

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