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In this issue:

European Corn Borer Flight Takes Off

Insect Pest Update

Country-of-Origin Labeling Session
Vol 5 No. 2   June 20, 2003

Insect Pest Update

Eric Burkness and Suzanne Wold, Dept. of Entomology, University of Minnesota, St. Paul, Minn. Images taken by Robert Koch, Dept. of Entomology, Univ. of MN

Bean Leaf Beetle (Ceratoma trifurcata, BLB): Last week we observed BLB feeding on leaves of squash. This is the first time in 14 years that this has been observed. Feeding appears to be limited to the cotyledons, and appears similar to striped cucumber beetle feeding (see images below). Populations of BLB are beginning to decline in snap beans as the overwintering population is completing egg lay and dying.

 
blb feeding on squash blb damage squash

BLB feeding on squash cotyledon

BLB feeding damage on underside of squash cotyledon
   
Striped Cucumber Beetle (Acalymma vittatum, SCB): Populations in cucurbits (squash, cucumber, pumpkins, melons) are low with the first SCB detected on plants in the second week of June. On June 16, samples indicated <0.2 SCB/plant (see cucumber beetle fact sheet for treatment thresholds). In addition to SCB and BLB in cucurbits, Collembola (spring tails) have been observed feeding on plants (see image below). Collembola typically are present in soil, feeding on decaying plant matter, and rarely move to feed upon economically important crops. Again, feeding appears to be mainly limited to cotyledons (see image below), with feeding damage looking similar to SCB feeding. Currently there are no recommendations for managing Collembola on cucurbits. However, Collembola populations have decreased with the drier, warmer weather conditions.
   
collembola collembola damage

Collembola on squash cotyledons

Feeding damage on squash cotyledons by Collembola

   
Seed Corn Maggot (Delia platura, SCM): Second generation of SCM caused a moderate level of damage to snap bean seedlings, with 13% of seedlings in untreated check plots were "snakeheads" (see image, right), where the unifoliate leaves have been clipped off by SCM before plants emerge from the soil. snakehead snap bean

Damage from seedcorn maggot on snap bean resulting in a “snakehead”
   

Potato Leafhopper (Empoasca fabae, PLH): PLH is taking off in alfalfa and snap beans. Sweep counts in alfalfa went from 0.65/sweep on June 11, to 1/sweep on June 13. These levels are below treatment thresholds for maturing alfalfa. However, with most of the alfalfa in the state having been cut in the last 2 weeks, regrowth should be watched closely. If preharvest populations return to fields after cutting, the preharvest population of 1 PLH/sweep is well above the threshold of 0.2 PLH/sweep on alfalfa that is 3" tall.

Sweep counts in snap beans have increased from 0.3 PLH/sweep on June 13, to as high as 4.5 PLH/sweep on June 16. Necrotic lesions on snap bean leaf margins caused by PLH feeding have been observed on snap beans up to the 4th trifoliate stage in Rosemount, MN. Treatment thresholds for PLH in snap bean are 0.5 PLH/sweep up to the 3rd trifoliate, and 1 PLH/sweep for plants at the 3rd trifoliate and larger.

 
Corn Earworm (Helicoverpa zea, CEW): We have not yet observed any CEW in our pheromone traps. We are anticipating an above normal flight of CEW in June, so cooperators are urged to make sure their pheromone traps are set up.
 

For more information about all insect pests of vegetable crops, please view the VegEdge Fact Sheet site at: http://www.vegedge.umn.edu/intro/pestfact.htm

Co-Editors: Bill Hutchison, Department of Entomology, University of Minnesota, hutch002@tc.umn.edu
Jeanne Ciborowski, IPM Program, Minnesota Department of Agriculture, jeanne.ciborowski@state.mn.us
Production Editor: Suzanne Wold, Research Fellow, Department of Entomology, University of Minnesota, woldx018@tc.umn.edu

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Last Revised June 17, 2003.
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