In this issue:

ECB and CEW Moth Flight Update

Cabbage Looper Alert

Soybean Aphid Update

Cowpea Aphids Arrive, in Alfalfa

Business Planning Guide Available

Swedish Machine for Fresh-Market Growers

Cabbage Looper Alert!

Bill Hutchison, Dept. of Entomology, University of Minnesota, St. Paul

Cabbage looper (CL) infestations are increasing, and CL is the most damaging and difficult cabbage pest to control. Cabbage looper is one of our Midwest pests that migrates from southern U.S. states each year, usually in early July. Moths have been laying eggs for the past 2 weeks. Larval infestations (see photo, left) are now common in the Twin Cities area, and some have exceeded treatment thresholds (see Table, below). During the past week, we have observed a dramatic increase in looper infestations in Apple Valley and at Rosemount (Dakota Co.). Looper infestations in untreated check plots now have egg and larval infestations of 13% and 8%, respectively.

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So far this year, Diamondback Moth (DBM) and Imported Cabbageworm (ICW) infestations have been relatively low. As in past years, we have found very high levels of DBM parasitism (80%).	Diamondback pupa (top) and adult (bottom)
With CL and ICW, there is usually significant natural larval mortality in the 1st and 2nd instar (i.e., <1/4 to 3/8 inch size). Our experience over the past 7 years has shown it is best to wait about 4-5 days after the eggs begin to hatch, and re-sample to verify that the larval infestations is >10%; if so, then spray at this time, and re-check fields in 5-7 days.
Egg lay and larval infestations for both CL and ICW can be expected to continue to increase. Fields should be monitored 1-2 times/week to determine infestation levels of CL, ICW, and DBM. Diamondback moth larval infestations are at 10-20%. However, parasitized diamondback pupae have been found and parasitism rates can reach up to 90%, which should hold populations under threshold. Treatment decisions should therefore be based primarily on the presence of the cabbage looper, the most damaging of the three pests, and ICW. Thresholds are also dependent upon the plant growth stage. The thresholds listed in the table above have worked well in recent IPM implementation studies at Rosemount and Apple Valley, Minn.	Imported cabbageworm larvae

Control: Many insecticides are now labeled for the larval pest complex on cabbage and the related cole crops. The following table(click here to view), based on data collected in 2000, provides a good overview of some of the control provided by several registered insecticides. As expected, the pyrethroids (Warrior and Capture in this data set) provide good control of the entire pest complex. SpinTor (spinosad) is one of the new reduced-risk products that also provides reasonable looper control, yet also conserves more beneficial insects (e.g., for aphid control, etc.), compared with the pyrethroids. Dipel ES is one of the conventional Bt (Bacillus thuringiensis) products that provides reasonable control, if applied often enough (every 5-7 days for looper control). Dipel should still have organic certification (but check local certification lists). Note: Recent research on CL and DBM resistance management, in collaboration with Dr. T.-X. Liu, Texas A&M University, confirmed that both pests in Minnesota, continue to be susceptible to Warrior and Avaunt insecticides.

For more efficacy data on the cabbage insect complex, see the October 22, 1999 article at: http://www.vegedge.umn.edu/mnvegnew/vol1/cab1014.htm

See also the cabbage pest fact sheet at: http://www.vegedge.umn.edu/vegpest/colecrop/cclist.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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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 directions of the manufacturer

Last Revised August 7, 2003.
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