Identification and distribution of barnyard grass (Echinochloa crus-galli and E. muricata)
Barnyard grasses (Echinochloa spp.) have become increasingly prevalent in agricultural fields of the Prairie Provinces during the past 30 years. The taxonomy and identification of the barnyard grasses has been controversial and difficult. At least two annual species occur as weeds in arable fields; the Eurasian Echinochloa crus-galli and the native E. muricata. Although they are relatively easy to distinguish from other Canadian grass weeds by the absence of a ligule, both exhibit considerable morphological variation and are often confused or simply reported as a single species, E. crus-galli. The two species can be most readily distinguished using characteristics of the mature fertile lemmas and paleas. In E. crus-galli the top of the body of the lemma is broadly rounded with an irregular row of hairs. The short acute tip is abruptly different in colour and texture from the body of the lemma. The top of the lemma in E. muricata gradually and smoothly tapers into a pointed tip, without a sharp contrast in texture, colour or pubescence. An examination of about 100 plants collected in 2006-8 and over 240 herbarium specimens suggests that the Eurasian E. crus-galli is less common in the Prairie Provinces than the native E. muricata. The distribution of the species was found to overlap and the two species were occasionally found at the same site. In order to understand any ecological differences that may be important in their effective management, it is critical to be able to recognize the differences between the species in research and control programs. Inconsistencies in reported behaviours and responses, within Canada and other parts of the world, may be at least in part due to the confusion of these two species.
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