MN Fruit & Vegetable IPM News - Vol. 3, No. 6

Pest pressure in most crops continues to remain relatively low in the Rosemount, MN (Dakota Co.) area. Pest pressure in cabbage (heading stage) has remained below threshold with 30% of plants with single diamond back moth larvae (DBM). As in previous years, we continue to see almost no imported cabbage worm larvae in large acreage cabbage fields. Although we did not detect any cabbage looper (CL) in our official samples, we did find 2 medium CL larvae on cabbage plants. This indicates that the population is very low but is present. With the relatively early arrival of potato leafhopper (PLH) and corn earworm (CEW) this year, both migratory insects in Minnesota , it is not surprising that CL would show up a little early. We typically expect CL in Minnesota during the 1^st week of July. Therefore, scouting efforts may need to intensify to pick up potential early infestations at these lower levels (see Cabbage Looper Fact Sheet).

We continue to see the influence of the weather on IPM and pest migration this week as the population of PLH increased in Minnesota after the weekend storms moved through the state. In alfalfa, populations increased from 5/50 sweeps on 6/15, to 20/50 sweeps on 6/19. This increase is related to migration as no nymphs had previously been detected in alfalfa. Similarly, in snap beans, we had an increase in PLH from 4/50 sweeps on 6/12 to 35/50 sweeps on 6/19. For PLH, it is critical to monitor fields frequently because of the potential for populations to increase or decrease rapidly based on weather systems moving through an area. (see Potato Leafhopper Fact Sheet)

Low levels of CEW and European corn borer (ECB) continue to be caught in pheromone and black light traps across the state. Early planted sweet corn that is approaching tassel and 1^st silk should be monitored closely as these plantings will be highly attractive as field corn and late-planted sweet corn are still vegetative. With sweet corn IPM, timing is everything, so make sure you are prepared to make management decisions before 1^st silk arrives. We have observed a light infestation (<5%) of ECB (2^nd instar) in emerging tassels of sweet corn; degree-days through 6/20 are currently at 825 indicating the start of the treatment window for 1^st generation ECB. Also, by 825 degree-days, approx. 90% of the first-generation moths should have emerged, indicating the end of the flight. Growers in the south central and western Minnesota , however, should continue to monitor ECB flights for he univoltine strain of ECB, with peak emergence in July (see Moth Flight Data Page). For the most recent, comprehensive guidelines on Sweet Corn IPM, see the New Publications article (this issue of the IPM Newsletter ).

Striped cucumber beetle (SCB) populations continue to increase in the Rosemount area this week. Populations increased this week to 2.3/plant in an untreated plot of cucumbers that were starting to vine. In a treated area in the same field that had received 2 pyrethroid sprays, populations were at 0.15/plant. This emphasizes that your monitoring program should continue even after several applications of insecticide have been made to confirm the product is working and that a re-infestation has not occurred. (see Striped Cucumber Beetle Fact Sheet)

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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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