The rice stink bug, Oebalus pugnax, is the most important late-season insect pest of rice in the South.
Adults and nymphs of this insect remove the contents of developing rice grains using their piercing-sucking mouthparts. The nature and extent of damage from stink bug feeding depends on the level of infestation, the stage of grain development at which feeding occurs, and perhaps other factors such as rice variety and weather.
Feeding by rice stink bugs can result in reductions in both yield and grain quality. However, at infestation levels typically found in commercial rice fields, reduction in grain quality is probably the more important type of damage.
Reduction in grain quality takes the form of “pecky rice” (chalky, discolored areas around feeding sites). Growers are penalized by mills for high incidences of peck; moreover, pecky rice is more likely to break during the milling process, leading to a lower percentage of whole grains in milled rice.
Rice stink bug management programs are in need of re-evaluation and revision. Recently, Mike Stout (professor at the LSU AgCenter) led a regional proposal to revise the rice stink bug management program in the South. This is a multi-state effort with entomologists and a plant pathologist from Arkansas, Missouri, Texas and Louisiana participating.
Our research and Extension project is beginning at a critical time of change in rice stink bug management. Economic thresholds that are currently in use were generated using varieties, market conditions and agronomic practices that are now obsolete.
Recent evidence from Texas strongly suggests that these thresholds should be substantially higher. In other words, fewer insecticides sprays should be applied in most situations. Furthermore, new chemistries with longer residual times and better environmental profiles are now available for use in some southern states.
Unfortunately, we have recently documented that repeated use of pyrethroid insecticides may be leading to the development of insecticide resistance.
Recent research has also started to reveal some non-chemical alternatives for stink bug management. Research and Extension efforts are needed to see if these alternatives are a good fit in the southern rice production region.
Our three-year proposal was selected for funding by the USDA southern region IPM center. The overall goalof the project is to improve rice stink bug management programs in southern rice-producing states by updating the thresholds that guide the application of insecticides, by facilitating the anticipated adoption of neonicotinoid insecticides, and by educating stakeholders with respect to these changes.
We are evaluating the acute toxicities of pyrethroids to rice stink bugs to assess the onset of insecticide-resistant rice stink bugs populations in areas of heavy insecticide use. Rice stink bug density-damage relationships are being characterized to allow the generation of revised economic thresholds for stink bugs, and the influence of rice variety on stink bug damage is being investigated, as a first step in understanding the potential role of plant resistance in rice stink bug management programs.
The efficacies and residual activities of dinotefuran and clothianidin (two neonicotioids) against the rice stink bug are also being evaluated.
Finally, the feasibility of tank-mixing a neonicotinoid and a fungicide and applying the tank mix at early stages of rice heading will be assessed soon.
Successful completion of the proposed objectives — notably, integration of new, higher thresholds and new insecticides (if clothianidin or dinotefuran is registered during the funding period) into management programs — will result in programs that are more cost-effective and less damaging to the environment and human health than current programs.
Our work as a regional team will produce results that will be useful across the Southeast.
You can follow our progress at the Louisiana rice insects blog: www.louisianariceinsects.wordpress.com.