Occurrence of Large Nematode Populations in Irrigation Canals of South Central Washington

Abstract

Studies carried out during the 1965 season at Prosser, Washington showed the presence of large numbers of nematodes in irrigation water. Water samples were collected with a depth adjustable sampling tube and nemas were extracted using modified screening and Baermann funnel techniques. Efficiency of the method was inversely proportional to the volume of water sampled. Distribution of nematodes within a canal was random as they did not concentrate in any portion of the canal and no tendency for them to settle out of flowing water was detected. Population densities in the Sunnyside and Roza Canals ranged from approximately 25 to over 200 nemas per gallon (3.775 1) of water, depending upon the date of sampling. Estimates from these data indicate that from 2 to 16 × 109 nematodes per day were carried past a given point. Plant parasitic nematodes generally accounted for 10-20% of those extracted from irrigation water with the highest concentration of these nemas occurring during mid-season in the Sunnyside Canal.