Understanding host relationships between invasive species and their non-native hosts has important economic and ecological considerations. The red clover casebearer moth (RCCB), Coleophora deauratella Lieneg and Zeller (Lepidoptera: Coleophoridae), is an invasive red clover seed pest introduced to Canada in the 1960’s. RCCB larvae feed on developing seed from June to late August then overwinter in crop debris. RCCB can cause seed yield losses of ≥80% in second-year seed stands of red clover. There are no registered pesticides for RCCB. Both larvae and adults have been reported in alsike clover fields but little damage is seen on these plants, and female moths display lower fecundity on alsike clover. The purpose of this research was to compare the larval abundance and development of RCCB on red clover (Trifolium pratense) and alsike clover (Trifolium hybridium). I also wanted to compare moth species diversity and larval abundance in red and alsike clover seed crop fields and volunteer clover patches. In addition, host quality was assessed by rearing field-collected larvae on laboratory-grown clover flower heads and observing growth and development. No larvae were recovered from alsike clover fields or volunteer alsike patches, while 338 larvae were recovered from red clover fields and volunteer patches. Larvae reared on alsike clover had a 30% mortality rate during the rearing period, while larvae reared on red clover had a 5% mortality rate. More weight was gained by larvae reared on red clover (mean weight gain= 0.00438 grams, n=19) compared to larvae reared on alsike clover (mean weight gain= 0.00274 grams, n=109, t = -2.9093, p= 0.01407). This suggests that the difference in damage and fecundity may be due to lower host quality.
