Impact of plant seeding rate on stem borer (Family: Crambidae) injury in drill-seeded rice (Oryza sativa L) in Louisiana

Stem borers (Family: Crambidae) are a serious threat to rice production in the US Gulf South, especially from mid- to late-season. These pests bore into rice stems and disrupt the flow of nutrients to the grain, resulting in a bleached panicle or ‘whitehead.’ In heavy stem borer infested regions like Southwest Louisiana and Southeast Texas, growers have historically relied on the insecticidal seed treatment Dermacor X-100 which is the only labelled seed treatment with activity against stem borers. However, reports of reduced performance from Dermacor are becoming more common, raising concerns about its continued effectiveness. Because Dermacor X-100 is applied based on land area, lower seeding rates result in more insecticide per seed but a lower overall plant population, which may limit yield potential. In contrast, higher seeding rates result in less insecticide per seed but may diffuse stem borer injury across more plants, potentially reducing yield loss per unit area. To evaluate the potential yield and stem borer control trade-offs associated with seeding rate, a small-plot, field trial was conducted at the H. Rouse Caffey Rice Research Station in Crowley, LA. Stem borer protected (Dermacor X-100) and unprotected plots were established at 39.2 and 196.1 kg/ha seeding rates in a factorial randomized complete block design with five replications. Whiteheads were assessed at 100% heading and yield data was collected with a small-plot combine at harvest maturity. We tested the hypothesis that seeding rate can influence whitehead densities.