False Chinch Bug in Potato, Mustard Greens, and Sweet Corn

Bill Hutchison & David Ragsdale, Dept. of Entomology, Univ. of Minnesota, St. Paul, MN

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The false chinch bug, Nysius raphanus Howard, has not previously been a common pest problem in Minnesota. However, during the past week, we have received several calls about infestations in potato and mustard greens (e.g., Arugula "lettuce"). This insect has a wide host range (mustards, solanaceous, beets, cotton, and even pine tree seedlings), and may not be limited to potato or mustards in your vegetable program. Last year, we had an outbreak on sugarbeets in southern Minnesota, and samples this week have also come from ornamentals. As indicated by the photograph, the adults are similar to other true bugs within the order Hemiptera; however, they are quite different from the common chinch bug, Blissus leucopterus, a common pest of corn and sorghum (usually south of MN), whose host range is primarily limited to feeding on grass species.

Weather conditions this spring have apparently been favorable for false chinch bug development. In Minnesota, we believe the adults may have recently moved into vegetable crops from drying weeds in the mustard family, such as penny cress. In some cases, very high densities of adult false chinch bugs were present on the crop, with many adults crawling over the plants, and some "swarming" activity observed. Adults and nymphs have piercing-sucking mouthparts, and do not appear to leave any distinguishing marks on the foliage. However, leaves on infested plants, and especially on young plants, were turning brown and stems of potato have wilted because of the large amount of sap being withdrawn. As of June 25, over 700 ac of potato had been treated in MN. In potato, the only products we recommend at this time is Thiodan (endosulfan) or Monitor (methamidophos), applied with ground equipment using high volumes (40 gal/acre). Initial attempts at using dimethoate and one pyrethroid (Baythroid) in potato did not provide adequate control. We have very limited efficacy data for this pest and must rely on what works on other crops. It appears that insecticides with long residual activity are needed to control this insect. The literature is replete with statements that this insect is difficult to control, possibly because of constant reinvasion by individuals from surrounding vegetation.

** Since the first printing of this article (June 2001), we have also received reports of this insect attacking sweet corn. Young (early whorl) sweet corn should be checked carefully. Again, we have no efficacy data for this pest. In sweet corn, if one of the pyrethroids does not provide control, consider using Lorsban 4E (organophosphate). Although Lorsban has a 35 day pre-harvest interval (phi), this may provide a reasonable alternative to pyrethroids (update 7-19-01; W.D. Hutchison).**

For more information, see: False chinch bug: http://ccvipmp.ucdavis.edu/insects/lettucepests.html

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
Cindy Tong, Department of Horticulture, University of Minnesota, c-tong@tc.umn.edu
Production Editor: Suzanne Wold, Department of Entomology, University of Minnesota, woldx018@tc.umn.edu

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Last Revised August 1, 2001
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