Determining the yield loss/injury relationship between the rice billbug (Sphenophorus pertinax Olivier) and rice (Oryza sativa L.) as influenced by rice cultivar

The rice billbug (Sphenophorus pertinax Olivier) is the key weevil pest of furrow-irrigated rice FIR across the Midsouth. Female S. pertinax deposit eggs into feeding holes near the base of the plant where larvae will emerge and destroy vascular tissues. Larval injury in rice prevents grain-fill of developing panicles leading to direct yield loss. This injury (aka ‘whiteheads’) is identical to injury caused by stem borers (Family: Crambidae) which has shown to be influenced by cultivar in recent literature. Experiments in this study were conducted to determine the impact of cultivar on S. pertinax injury and to define the yield loss relationship associated with S. pertinax. Small plot field research was conducted at the H. Rouse Caffey Rice Research Station in Crowley, LA, in 2024 using cultivars ‘Addi Jo’ (tolerant) and ‘CLL17’ (susceptible) compared to ‘PVL03’ and ‘RT7521FP’ (industry relevant). Rice was also tested under protected vs unprotected conditions in a split-plot design with four replications. Adult feeding injury (dead tillers) was monitored throughout crop development beginning at 3^rd-4^th tiller and larvae injury was assessed once at early-booting stage. Whiteheads per m² were assessed at 100% heading and rice was harvested at grain maturity with a whole-plot harvester, adjusted for 14% grain moisture. Data was subjected to GLMM in SAS using PROC GLIMMIX and means were separated using Tukey’s HSD (α=0.05). A yield loss relationship was determined by regressing number of dead tillers and whiteheads against rough rice yields (kg/ha). H₀=cultivar will not influence insect injury or yield loss regression.