Investigating the effect of plant growth stage on the susceptibility to stem borer larval preference in commercial rice varieties

The Mexican rice borer (MRB, Eoreuma loftini) is a major late season pest threat to rice production in the southern United States, causing yield losses of up to 50% in Texas. MRB activity during reproductive stages causes “whitehead” damage, characterized by whitish and empty panicles, contributing to yield loss. Current control relies on Chlorantraniliprole seed treatment, raising concerns about insecticide resistance from overreliance. Host-plant resistance (HPR) offers a durable and environmentally responsive control method. Furthermore, understanding the influence of plant growth stages on resistance/tolerance enhances effectiveness of insecticide application and timing. This study aims to understand the relationship between four rice growth stages (Mid-Tillering, Panicle Differentiation, Booting and Heading) on susceptibility to MRB’s infestation in three rice varieties (PVL03, Jupiter and CLL18). We hypothesize that the susceptibility of rice to MRB damage varies across growth stages and rice varieties, with some varieties exhibiting higher bore success and whitehead formation. Two no-choice greenhouse experiments were conducted in 2024 (GH1) and 2025 (GH2) at Texas A&M AgriLife Research Center in Beaumont – TX. At each growth stage, a 2nd instar larva was placed in main stem nodes, with bore success monitored daily, and whitehead formation and adult emergence recorded weekly. Data will be analyzed using RStudio. Results will be discussed later. By identifying the most vulnerable growth stages and varieties, this research can guide the timing of insecticide applications and contribute to the development of more effective IPM strategies.