A field experiment with nematicide treatment revealed potential sugarcane yield loss caused by plant-parasitic nematodes in Okinawa, Japan

Sugarcane yield in Japan has continuously decreased by 17% over the past 20 years. The objective of this study was to quantify the sugarcane yield loss caused by plant-parasitic nematodes (PPN) under field conditions in Japan. We set up 15 plots in a sugarcane field in Kitadaito, Okinawa, and assigned them to nematicide-treated (fosthiazate, 3 kg (×0.7) and 7.5 kg (×1.7) per ha) and non-treated control plots in 5 replicates. Initially, the numbers of lesion nematodes (Pratylenchus zeae) did not differ significantly among the three treatments, but were significantly lower in ×1.7 fosthiazate than in the control after 3 and 5 months. Sugarcane yield in 12 months was significantly higher by ca. 15% in both the ×0.7 and ×1.7 nematicidal treatment (55 t/ha) plots than in the control (48 t/ha) plots. The results implied that the lesion nematode may suppress the number of tillers in the early stage, resulting in yield reduction.