Host preference and suitability of grasses for Oebalus pugnax.

The rice stink bug, Oebalus pugnax (Fabricius) (Hemiptera: Pentatomidae: Carpocorini), though graminaceous, discriminates among its numerous host grass species. This could represent a feeding preference, it could be related to host suitability for growth and development. To clarify the role of host grass discrimination, two laboratory studies were conducted: (1) free-choice tests to evaluate preferences of O. pugnax among 11 wild host grass species found in three rice-producing counties of the central Mississippi Delta (MS, USA), and (2) no-choice tests to evaluate the impact of rice (Oryza sativa L.), junglerice [Echinochloa colona (L.) Link], and dallisgrass (Paspalum dilatatum Poir.) (all Poaceae), on the development of O. pugnax from second instar to adult. In the free-choice test, four experiments were conducted, each with four sets of host grass species and observed 1, 2, 4, 8, and 16 h after release in cages. Approximately 4 h was necessary for O. pugnax to settle on preferred host grasses. Oebalus pugnax showed a feeding preference for junglerice over all 10 other grass species. Bahiagrass, Paspalum notatum Flueggé, was the least preferred. The no-choice tests showed significant effect of host grass species on O. pugnax mean development time of nymphal survival to adults. Survival of nymphs was lower and mean development time was longer on dallisgrass compared to rice and junglerice. Knowledge of O. pugnax rate of growth and development on host grasses could be useful in the future development of rice integrated pest management strategies.