Influence of Irrigation on Effectiveness of Nematicides for Management of Columbia Root Knot Nematode on Potatoes

In the Pacific Northwest of the United States of America, the Columbia root knot nematode, Meloidogyne chitwoodi, causes yield reduction and significant numbers of blemished and thus unmarketable potato tubers. Depending on market conditions, an entire field can be declared unmarketable when 5 to 10% of the tubers are found to be blemished. The influence of irrigation on nematicide effectiveness was evaluated in two field trials conducted in a silty clay loam soil with 12% organic matter. Plots were 0.9 m wide by 18 m long arranged in a randomized block design with four replicates per treatment. Nematicide applications were injected into drip irrigation tubing with a piston pump. Treatment effectiveness was monitored via tuber yield and percent tubers with blemish. Nematode population levels were determined from soil samples taken pretreatment and at harvest. Drip irrigation applications of the fumigants metam sodium, 1,3-dichloropropene, oxamyl, and sodium tetrathiocarbonate applied in different volumes of water showed greater effectiveness with increasing volume of water. Of the products evaluated, the carbamate oxamyl was the most effective in reducing tuber blemish and nematode populations.