Western Bean Cutworm Information

Western Bean Cutworm: A new insect pest threatens Pennsylvania corn fields
John Tooker

Western bean cutworm (WBC; Noctuidae: Striacosta albicosta) has historically been a pest of dry beans and corn in the Great Plains; however, for some unidentified reason it has been moving eastward. In 2000, it was detected in northwestern Iowa and by 2004 had reached southeastern Iowa and threatened the western edge of Illinois. It was detected in Indiana in 2005 and Wisconsin, Michigan, and Ohio in 2006. By now it has moved farther east and adults have been trapped in central Ohio (Wayne Co.; < 90 miles from the western Pennsylvania border), and in Ontario (right across the lake from Erie County). Adults can be monitored with pheromone and light traps and they look similar to other noctuid moths (see this Iowa State webpage for a comparison of similar looking species: http://www.ipm.iastate.edu/ipm/icm/2007/6-11/wbc.html).

Fig. 1. Distinctive forewing of western bean cutworm.

Western bean cutworm completes a single generation per year. Adult moths fly in mid-summer and females lay eggs on the upper surfaces of corn leaves. As a late-season corn pest, WBC larvae feed on tassels, silks, and developing kernels and can cause severe damage. Control can be a challenge because larvae spend considerable time inside the husk.

To track the population as it approaches and enters Pennsylvania, we had a monitoring program in place from 1 July until the end of August with pheromone traps deployed in throughout Pennsylvania, but weighed more heavily on the western edge. This trapping effort was a joint effort between Penn State and the Pennsylvania Department of Agriculture (PDA) and traps were being checked and maintained by county extension educators and PDA field crews.

As of 1 October 2009: 93 WBC moths captured

Fig. 2. Location of traps that captured WBC moths (as of 1 October 2009).

17 July 2009: The first moth moth was captured in a bucket trap in Lycoming Co. It is surprising that our first moth has been found in the north central portion of PA. This may mean that moths are coming south from Ontario and New York or it could mean that moths are already distributed across PA. I hope further trapping will provide more clues...

19 July 2009: The second moth was captured in a bucket trap in Franklin Co., which is in south central PA bordering Maryland. This capture reinforces the notion that a low population of western bean cutworm moths is scattered across the state. Individuals may have established in previous years or they are entering PA from the west or the north and flying a good distance. It is difficult to say from two trap catches, but the former option seems more likely to me.

20 July 2009: A third WBC moth was captured in a bucket trap in Tioga Co., less than four miles from the New York border. Perhaps moths are coming south from New York, but it is still hard to say with so few captured individuals.

22 July 2009: We have now learned that the first WBC moth in the state was actually trapped on 10 July in Erie County at the Lake Erie Regional Grape Research & Extension Center. Subsequent captures at this site and another in Erie County have resulted in the discovery of 13 more moths. The activity in Erie County makes sense because WBC moths often follow prevailing winds, which can blow directly across the lake from Ontario (where WBC is established) into Erie County.

24 July 2009: We have confirmed capture of four more WBC moths. Two were captured in Forest Co. (one each on 10 and 21 July 2009) and two were captured in Clarion County on 15 July 2009. The position of these two counties in the northwest portion of PA may support the notion that WBC is entering PA from Ontario.

30 July 2009: We have confirmed capture of one more WBC moth. This individual was captured on 15 July 2009 in Washington Co., in southwestern PA. Folks trapping for WBC moths in Ohio have found at least one individual in Monroe Co., which is in SE Ohio, so the expansion of WBC into SW PA likely developed out of a population in Ohio.

10 August 2009: Two WBC moths have been trapped in southern Bradford Co., which is in the northeastern portion of PA, bordering NY. One of these moths looks pretty fresh indicating it may be from a local population. The proximity of Bradford Co. to New York, as well as other trap catches in Tioga and Lycoming counties but not counties to the south, might suggest moths are coming from a more northern population, but this remains to be confirmed.

11 August 2009: Four more WBC moths have been found at a different site in southern Bradford Co. Additionally, one more seems to have been found in Lycoming Co. and a sole individual was found near Wilks-Barre in Lackawanna Co. This pulse of activity certainly contrasts with the trap captures we were getting in July, and raises some questions about the activity period of the moths. What were moths doing between 21 July and Aug 10? I do not have any good answers. The individual from Lackawanna County further supports the notion that the species invade PA at least a year ago, if not longer.

25 August 2009: Forty-five more WBC moths were found in Erie County between 22 July and 18 August. These catches correspond well with increased flight activity in Ontario. The traps in Erie County are not far from the southern shore of the Lake Erie, so it seems that moths are flying across the lake and into Erie County.

31 August 2009: One more moth was captured in Lackawanna County. The flight period of the moths is likely near the end.

16 September 2009: Despite shutting down our trapping network, we are still receiving reports of WBC moths being found. Pennsylvania Department of Agriculture has reported finding single moths in Crawford and Somerset Counties as well as additional individuals from previously active trap locations in Forest and Clarion Counties. Further, an adept ag. professional caught a suspicious-looking moth by hand on 10 Sept in a Lehigh County sweet corn field. And we have a report of a WBC moth being found in the last couple days by a county extension agent while working in a field in Franklin County. All in all the activity period of this moth appears to be greater than previously recognized and it is spread over a greater area. The next goal is to see if we can find any fields with caterpillar damage. Keep your eyes open for any unusual infestations in corn ears.

18 September 2009: A homeowner in Westmoreland County found a WBC moth in his yard. If folks are just running across moths in their yard, they are clearly far more abundant and widespread than we anticipated.

26 September 2009: A county educator found two WBC moths in his yard in Montour County. He had put his pheromone trap in his back yard next to a patch of sweet corn after we stopped our more formal trapping efforts. Clearly, the moths are active later in the year than we thought. We are learning more and more about this new pest species.

WBC Pheromone traps in place: 30 (14 milk-jug traps; 16 bucket [aka unit] traps)

Fig. 3. Bucket trap in Tioga County, PA.

Traps located in the following PA counties:
Armstrong
Berks
Bradford (2)
Cambria
Centre
Clarion
Dauphin
Erie (3)
Fayette
Forest
Franklin
Greene
Indiana (2)
Jefferson
Lackawanna
Lancaster
Lebanon
Lycoming
Mercer (2)
Montour (only the end of the season)
Somerset
Tioga
Warren
Washington
Westmoreland (2)

Trapping efforts in nearby states and Ontario:
Ohio: http://entomology.osu.edu/ag/pageview3.asp?id=1390
Michigan: http://www.msuent.com/insect_info_by_crop/Corn/
Ontario:http://www.cornpest.ca/default/index.cfm/wbc-trap-network/