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Funded Project

Funding Program: Regional IPM Grants (S-RIPM)

Project Title: Revising management programs for the rice stink bug in southern rice

Project Directors (PDs): Michael Joseph Stout [1] Natalie Hummel [2] Don Groth [3] Krisanna Machtmes [4]

Lead State: LA Lead Organization: Louisiana State University Agricultural Center

Cooperating State(s): Arkansas, Missouri, Texas

Extension Funding: $59,988

Research Funding: $60,898

Start Date: Aug-19-2009 End Date: Aug-18-2012

Pests Involved: rice stink bug

Site/Commodity: rice

Summary: The rice stink bug, Oebalus pugnax, is the most important late-season insect pest of rice in the southern United States. 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 both the level of infestation and the stage of grain development at which feeding occurs. Feeding by rice stink bugs can result in reductions in both yield and grain quality, but, 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. Management programs for the rice stink bug throughout the south are outdated and inadequate, and there is a compelling need for re-evaluation and revision of all aspects of the rice stink bug management programs used throughout the south. This need can be summarized in five points: First, insufficient information on the incidence and severity of stink bug infestations and on insecticide use patterns is available to generate precise estimates of economic impacts of stink bugs; second, the insecticides used against rice stink bugs (pyrethroids and methyl parathion) are damaging to the environment and/or human health, and heavy use of these insecticides may be leading to the development of insecticide resistance; third, the economic thresholds used to guide applications of insecticides were generated using varieties, market conditions and agronomic practices that are now obsolete, and recent evidence from Texas strongly suggests that these thresholds should be substantially higher; fourth, there is a need for further evaluation of neonicotinoid insecticides, which are less damaging to the environment and have longer residual activities than currently used insecticides; and fifth, there is a need to begin to evaluate nonchemical alternatives for stink bug management. The overall goal of the proposed research is to improve rice stink bug management programs in southern rice-producing states by updating the thresholds that guide applications of insecticides, by facilitating the anticipated adoption of neonicotinoid insecticides, and by educating stakeholders with respect to these changes. Pre- and post-study surveys will be developed and delivered to stakeholders in the South to assess the current status of rice stink bug management programs and (after the proposed funding period) to evaluate the rate of adoption of new recommendations. Data on the acute toxicities of pyrethroids and methyl parathion to rice stink bugs will be generated to assess if insecticide resistance is developing in populations of stink bugs in areas of heavy insecticide use. Rice stink bug density-damage relationships will be characterized to allow the generation of revised economic thresholds for stink bugs, and the influence of rice variety on stink bug damage will be 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 will be 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. Successful completion of the proposed objectivesnotably, 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. Objectives: Objective 1 (research/extension): Evaluate current management programs for the rice stink bug. Objective 1a. Characterize regional variation in stink bug management practices. As noted above, management programs for the rice stink bug in the south are similar in their broad outlines, but some regional variation does exist. An incomplete understanding of this regional variation hinders region-wide efforts to improve management programs. A survey will be developed and delivered to stakeholders in the beginning of the funding period to assess the current status of management programs. Obective 1b. Investigate possible development of resistance to methyl parathion and pyrethroids in stink bug populations. Heavy reliance on pyrethroids and methyl parathion may be leading to the development of insecticide resistance in rice stink bug populations. Acute toxicities of a pyrethroid and methyl parathion will be compared among populations of stink bugs from areas of light, moderate, and heavy usage of insecticides. These data will be compared with each other and with data obtained in 2001 and 2002 to investigate the possible development of resistance. This objective will help evaluate the sustainability of current patterns of insecticide use. Objective 2 (research). Revise economic thresholds for insecticide use against the rice stink bug. In light of recent work which indicates that economic thresholds for stink bugs should be much higher than current thresholds in Texas, there is a clear need for reevaluation of thresholds in a second region. The research in this objective is designed to 1) determine if current thresholds are too low in Louisiana and 2) to obtain bug density-rice damage relationships that can be used to calculate new thresholds for Louisiana. Objective 2a. Estimate the efficiency of sweep-net sampling for rice stink bugs. Only two disparate estimates of the efficiency of sweep-net sampling are available in the literature. An estimate of sampling efficiency will be needed in order to relate density damage data (Objective 2b) to sweep net catches. Objective 2b. Characterize the relationship between rice stink bug density and damage to rice. Stink bugs at various densities will be confined to rice using cages to characterize the relationship between stink bug density and quantitative and qualitative damage to rice. Objective 2c. Calculate revised economic thresholds for Louisiana. Economic thresholds will be calculated based on data generated in Obj. 2b. Comparison of these thresholds with those published recently in Texas should give an indication of the overall applicability of new thresholds across the southern region. Objective 2d. Compare impact of stink bug feeding on different rice varieties. The impact of damaging levels of stink bugs (as determined in Obj. 2b) on three commercial varieties will be compared, to determine the potential contribution of plant resistance to stink bug management programs. Objective 3 (research) Evaluate alternative insecticides for stink bug management. Objective 3a. Compare the efficacy and residual activity of dinotefuran and clothianidin with the efficacy and residual activity of pyrethroids. Preliminary evidence from several states indicates that dinotefuran and clothianidin (both neonicotinoids) are as effective as pyrethroids, and may actually have longer residual activities. Further work will be carried out to determine optimal rates, timings, and use patterns. Objective 3b. Investigate the effectiveness of tank mixes of neonicotinoid insecticides and fungicides for control of late-season pests of rice. Because the neonicotinoids may have longer residual activities, it may be possible to apply tank mixes of neonicotinoids and fungicides at 50-70% heading and achieve adequate control of both stink bugs and fungal diseases. Tank mixes would allow growers to reduce costs associated with application of pesticides, making pest management more cost effective. Objective 4 (extension) Implement revised recommendations. Objective 4a. Prepare and disseminate educational materials. The adoption of new insecticides (if registered during the funding period) and new thresholds for insecticide use will represent a significant departure from past practices. Changes to existing recommendations will be delivered to stakeholders by a variety of means. Objective 4b. Conduct demonstration trials of new products and new thresholds. Once new insecticides are registered, replicated demonstration trials will be conducted at multiple locations throughout Louisiana. These trials will compare the new products to old products to demonstrate increased efficacy or residual activity of products. Also, new thresholds will be compared to old thresholds in side by side field comparisons. Objective 4c. Evaluate changes in practices used by farmers, consultants and other stakeholders. This evaluation will be accomplished by developing and delivering poststudy surveys to assess changes in insecticide use patterns and adoption of recommendations that result from this study.

Final Report:

Results From report submitted by the PI to USDA CRIS report system PROGRESS: 2009/09 TO 2010/08 OUTPUTS: Farmers are kept abreast of the results of this study through producer meetings and field days. PARTICIPANTS: Lead PIs, Michael J. Stout and Natalie Hummel, Department of Entomology, LSU AgCenter. Co-PIs: M.O. Way, Texas A&M, John Bernhardt, University of Arkansas, Kelly Tindall, University of Missouri, Don Groth, LSU. Grant funds supported a graduate student, Bryce Blackman, who conducted the described research as part of his Ph.D. project. TARGET AUDIENCES: Rice producers in the southern U.S.. Rice producers in the U.S. and globally. Agricultural scientists interested in integrated pest management. PROJECT MODIFICATIONS: Nothing significant to report during this reporting period. IMPACT: 2009/09 TO 2010/08 The management program for the rice stink bug has not been revised for over 20 years, and all current components of the program (sampling methods, thresholds, and insecticides) are outdated. In addition, alternative management tactics such as plant resistance and biological control are in need of further study and development because they play no part in the current management program. This three-year project represents a collaboration between major rice-growing southern states designed to revise and update of the entire rice stink bug management program. Several aspects of the current management program were investigated in 2010 in small-plot field experiments and greenhouse/laboratory trials. Acute toxicity bioassays proved further evidence for incipient resistance to pyrethroids in areas in which multiple pyrethroid applications are typically made to rice fields. Cage studies using different densities of stink bugs were conducted as a first step in the re-evaluation of thresholds for insecticide use against the rice stink bugs. A mark-recapture experiment showed that sweep net sampling captures only 15 to 20% of stink bugs present in plots. Several alternatives to pyrethroid and organophosphate insecticides were evaluated against the rice stink bug, including formulations of thiamethoxam and dinotefuran. Small-plot studies showed the efficacies of these products to be comparable to the efficacy of a widely used pyrethoid, but no evidence for longer residual activities for these alternative products was obtained in greenhouse experiments. Small-plot field studies were conducted to evaluate the interactions of planting date and rice variety on rice stink bug population densities and damage (peck). Significant differences among varieties were found. In the first year of the collaborative project, a graduate student has been recruited to conduct the proposed work. A Section 18 application for Tenchu (active ingredient, dinotefuran) was submitted to the EPA and we anticipate that Tenchu will be available for the 2011 growing season, increasing the options available to farmers.

Outcomes N/A

Impacts From report submitted by the PI to USDA CRIS report system The management program for the rice stink bug has not been revised for over 20 years, and all current components of the program (sampling methods, thresholds, and insecticides) are outdated. In addition, alternative management tactics such as plant resistance and biological control are in need of further study and development because they play no part in the current management program. This three-year project represents a collaboration between major rice-growing southern states designed to revise and update of the entire rice stink bug management program. Several aspects of the current management program were investigated in 2010 in small-plot field experiments and greenhouse/laboratory trials. Acute toxicity bioassays proved further evidence for incipient resistance to pyrethroids in areas in which multiple pyrethroid applications are typically made to rice fields. Cage studies using different densities of stink bugs were conducted as a first step in the re-evaluation of thresholds for insecticide use against the rice stink bugs. A mark-recapture experiment showed that sweep net sampling captures only 15 to 20% of stink bugs present in plots. Several alternatives to pyrethroid and organophosphate insecticides were evaluated against the rice stink bug, including formulations of thiamethoxam and dinotefuran. Small-plot studies showed the efficacies of these products to be comparable to the efficacy of a widely used pyrethoid, but no evidence for longer residual activities for these alternative products was obtained in greenhouse experiments. Small-plot field studies were conducted to evaluate the interactions of planting date and rice variety on rice stink bug population densities and damage (peck). Significant differences among varieties were found. In the first year of the collaborative project, a graduate student has been recruited to conduct the proposed work. A Section 18 application for Tenchu (active ingredient, dinotefuran) was submitted to the EPA and we anticipate that Tenchu will be available for the 2011 growing season, increasing the options available to farmers

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