The lack of uniform infestations of Mexican bean beetle (Epilachna varivestis Mulsant) in field plantings can make selection for resistance in segregating soybean populations very difficult . For this reason, the results from screening F2 plants in the field have been inconsistent. An alternative is to advance F2 plants to the F3 to provide replication at more than one location.
Smith, C. M.; Brim, C. A.; Campbell, W. V.; and Van Duyn, J. W.
"Research Notes: Techniques developed for screening soybeans for Mexican bean
Soybean Genetics Newsletter: Vol. 4
, Article 27.
Available at: http://lib.dr.iastate.edu/soybeangenetics/vol4/iss1/27