Winter Annuals and the Nematode (Soybean Cyst Nematode)

Glenn Nice, Weed Diagnostician, Department of Botany & Plant Pathology, Purdue University

Soybean cyst nematode (SCN) is a widespread problem in soybeans, reported to cause yield losses up to 50%¹. SCN is no stranger to Indiana – it has been reported in at least 82 counties¹. If you are a soybean grower or Ag. Professional who deals with soybeans, chances are you are well versed in SCN impacts and how to reduce populations of SCN, thus reducing impact. The relationship these troublesome nematodes have with winter annuals, however, is not as well known.

Earl Creech and Valerie Mock, graduate students at Purdue University under Bill Johnson, have been studying this relationship between SCN and winter annuals. A web page has been developed presenting research on this relationship: Winter Annual Weed and SCN Management.

Six main alternative hosts have been identified in winter annuals². Purple deadnettle and henbit, two winter annuals from the mint family, have been identified as strong hosts. Field pennycress has been identified as a moderate host, and shepherd’s-purse, small-flowered bittercress, and common chickweed have been identified as weak hosts^{2, 3}. In greenhouse studies, purple deadnettle was found to have even more reproduction of SCN than on susceptible soybeans².

These winter annual hosts are commonly found in Indiana fields in the spring. In a survey conducted in Indiana of fields with SCN, 93% of the fields contained one or more of these winter annual species, some at high densities³. The recommended management practices to reduce SCN populations is to rotate non-host crops with SCN-resistant soybean; however, if these fields have an abundance of alternate hosts present, this would decrease the efficacy of this management technique on the SCN. Controlling these alternative hosts would be an important management practice to try to reduce SCN populations.

For more information regarding SCN and winter annual hosts please see the following references.

Reference:

¹Jamal Faghihi and Virginia R. Ferris. 2006. Soybean Cyst Nematode. E-210-W

²Valerie A. Mock and Bill Johnson. Identification of Six Alternative Winter Annual Weed Hosts for Soybean Cyst Nematode. (pdf file)

³Valerie A. Mock, J. Earl Creech, Bill Johnson, Jamal Faghihi, Virginia R. Ferris, and Andreas Westphal. 2007. Winter Annual Weeds and Soybean Cyst Nematode Management. WS-36. (pdf file)

Click image to enlarge

Figure 1. Purple deadnettle is a strong soybean cyst nematode alternate host.