Survey of Pulse Crop Field for Plant-Parasitic Nematodes in the Canadian Prairies.

The distribution of economically significant plant-parasitic nematodes in pulse crops in the Canadian Prairies is relatively unknown. Reports suggested that Ditylenchus dipsaci in yellow pea export was likely the nonquarantine species D. weischeri, a Canada thistle (Cirsium arvense) parasite. To determine if D. dipsaci is found in pulse plants and understand nematode distribution in the Canadian Prairies, a survey was conducted in commercial yellow pea, lentil and chickpea fields in Alberta, Saskatchewan, and Manitoba. Samples of pulse and thistle plants (flowers or pods, stems and leaves) and soil were collected from 94 fields. Nematodes were identified by morphological features and molecular analyses (species-specific PCR, PCR-RFLP, and sequencing of the partial 18S, 28S and ITS of the rDNA gene). High densities of plant-parasitic nematodes - Pratylenchus, Paratylenchus, Helicotylenchus and Telotylenchinae - were found in several fields. Ditylenchus weischeri, a parasite of thistles and not pulse crops, was recovered from 20 fields across Alberta, Saskatchewan and Manitoba; D. dipsaci was found in pods of one yellow pea field in Manitoba. These results confirm the high prevalence of D. weischeri on creeping thistle in pulse fields and the near absence of the quarantine pest D. dipsaci.