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Funded Project |
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Funding Program:
IPM Enhancement Grants |
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Project Title:
Insecticide susceptibility and esterase activity in the redbanded stink bug |
Project Directors (PDs):
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Lead State: TX Lead Organization: Texas AgriLife Research |
| Undesignated Funding: $29,925 |
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Start Date: May-01-2013 End Date: Apr-30-2014 |
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Pests Involved: Red banded stinkbug (Piezodorus guildinii) |
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Site/Commodity: Texas/Cotton |
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Area of Emphasis: Chemical Control |
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Summary:
The redbanded stink bug (RBSB), Piezodorus guildinii has emerged as a serious pest of soybeans in Texas (TX) and Louisiana (LA) and threatens soybean production in the southern states of the US. For 2011, we estimated losses due to RBSB on the Upper Gulf Coast of Texas as at least $11.5 million, while in LA losses could easily top $100 million annually. RBSB feeds directly on reproductive plant parts causing direct yield losses and reducing seed quality. It is currently the most damaging stink bug species in soybeans. In addition, it is less susceptible to traditionally available insecticides and has been responsible for the significant increase in the amount of insecticides used in LA and TX soybeans in recent years. Multiple applications of an organophosphate (acephate) to control RBSB have raised concerns of resistance development in RBSB populations in TX and LA. As this species is relatively new compared with other stink bugs in US soybeans, little is known about its biology, ecology, and management. Preliminary research suggests that the RBSB has become the most abundant stink bug species in TX and LA soybeans. The proposed study will determine susceptibility of RBSB populations to insecticides with different modes of action using vial bioassays and field trials. In addition, we plan to determine esterase activity levels in RBSB populations to explore a potential resistance mechanism against organophosphates in this pest. Data from insecticide susceptibility studies and esterase assays will be useful for selecting better insecticides for control of RBSBs and for resistance monitoring.
Objectives: 1. To determine susceptibility of RBSB to insecticides using glass-vial bioassay and efficacy of insecticides using field trials. Deliverables: Toxicity of candidate insecticides will be evaluated in the laboratory using glass-vial bioassays. Data from the glass-vial bioassays will determine baseline levels of susceptibility to pesticides and provide basis for resistance monitoring. Results from the insecticide field trials will help determining alternative products with best performance against RBSBs ultimately to help recommend potential new products for RBSB control. 2. To determine esterase levels in RBSB populations as possible resistance mechanism against organophosphate insecticides Deliverables: Esterase assay will provide information on esterase activities in different RBSB populations and will also establish the correlation between enzyme activity level and biological response of RBSBs. Direct survey of enzyme activity levels in field populations will provide informative data for resistance monitoring and strategic management. |
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Final Report: |
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Non-technical summary and Results Redbanded stink bug (RBSB), Piezodorus guildinii (Westwood) is a relatively new pest of soybean, Glycine max (L.) Merr. in the southern US. Invasion by this neotropic pentatomid has been responsible for a significant increase in the amount of insecticides applied in soybean threatening development of insecticide resistance in RBSB. This study was conducted to generate baseline data on insecticide susceptibility levels in current RBSB field populations. RBSB adults collected from commercial soybean fields were used in glass vial bioassay to determine LC50 values for pyrethroids (bifenthrin and cyfluthrin), neonicotinoids (thiamethoxam and imidacloprid), and an organophosphate (acephate) using technical grade materials. In addition, a small plot field trial was conducted to determine the efficacy of some commonly used pyrethroid, neonicotenoid and organophosphate formulations against RBSB. Glass-vial bioassays generated LC50 values of 0.76 µg/vial for bifenthrin, 0.18 µg/vial for cyfluthrin, 2.32 µg/vial for thiamethoxam, and 1.07 µg/vial, for imidacloprid after 4h of exposure. When RBSBs were exposed to acephate for 4h in vial bioassay, no more than 20% of mortality was recorded preventing the calculation of LC50 while after 24 hours of exposure a LC50 of 2.84 µg/vial was generated. Results from the field trial found significant reduction in numbers of surviving RBSBs one day after treatment (DAT) in all insecticide treatments except acephate when compared to untreated plots. While at 12 DAT, all insecticide treatments including acephate showed significant reduction in numbers of RBSBs. Results from both laboratory bioassay and field trial showed that RBSBs are more susceptible to neonicotinic and pyrethroid insecticides than to the organophosphate acephate, which took longer time to show RBSB mortality. We are currently analyzing esterase activity data. Results from both insecticide field trials and esterase activity essays will be reported in a peer-review publication |
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Target audience Our project has already reached the scientific community through presentations of our results at professional scientific meetings. A peer-review publication will be submitted to a journal shortly. Soybean producers constitute another of our target audiences. We have already presented our results to soybean growers at the Annual Field Day in Beaumont Texas. We will reach growers in other regions as well by sending our peer-review publication to IPM agents and extension researchers at soybean producing areas so they can summarize the information in our publication in local bulletins. |
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Activities / Events The results associated with this project have been disseminated regionally and nationally in 2013-2014. Nationally, we talked about the results of this project at the symposium, Emerging Pests in the Southwest and IPM Solutions at the annual meeting of the Southwestern Branch of the Entomological Society of America held in San Antonio, TX. At the regional level, we explained results from this project to soybean producers at the annual field day at Texas A&M AgriLife Research center in Beaumont, TX. My graduate student (who conducted this project) gave a talk based upon results of this project in the Texas Plant Protection Conference in College Station, TX and at the Student Research Week in Texas A&M University. We have recently submitted an invited talk to be given at the annual meeting of the entomological society of America to be held in Portland, OR in November 2014. |
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Outcomes Last year we evaluated efficacy of insecticides against RBSB using field trials and also conducted laboratory bioassays gathering baseline data on RBSB susceptibility to insecticides. Data generated from laboratory bioassays is crucial for monitoring the development of insecticide resistance in RBSB field populations. We have provided base-line data with which one can assess if resistance to Acephate and other commonly used insecticides is developing. Based on our data my laboratory has also proposed the need to test for acephate resistance development in RBSB population at multiple locations. In addition, this year we are conducting esterase assays on RBSB populations collected from different host plants to detect if variation occurs in esterase activity among these populations as a result of different levels of selection pressure from insecticide applications. The results from this research may have implications for resistance management and overall improvement of IPM practices. |
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Publications Publications **= Publication by my graduate students Vyavhare S**, M. O. Way, P. Pietrantonio, and R. F. Medina. Insecticide Susceptibility in Redbanded Stink Bug (Hemiptera, Pentatomidae) Populations in Texas Soybean. Pest Management Science. (In preparation) Vyavhare S**. Establishing and Implementing an IPM Program for the Redbanded Stink Bug, Piezodorus guildinii: an Emerging Soybean Pest in the Southern Region. (A chapter in this PhD dissertation was based on this research project) |
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Impacts Our data provide a benchmark for the future evaluation of insecticide susceptibility of RBSB. As currently no laboratory maintained standard susceptible colonies of RBSB exist, future studies to determine changes in susceptibility can compare back to the values generated from this study. In addition to our glass-vial bioassay data, direct survey of detoxification enzyme activities in field populations will provide a basis for resistance monitoring and strategic management, providing the association between biological response of RBSB to insecticides and enzyme activity level. Our data suggest that the most commonly used insecticide against RBSB (i.e., acephate) may not currently be the most effective one in terms of killing power. This study evaluated the toxicity of some candidate insecticides using glass-vial bioassays. Data from this work provides information to improve insecticide resistance monitoring and insecticide resistance management strategies for RBSB. By providing information on the LD50 of insecticdes other than acephate, this information will aid in the reduction of overall insecticide applications. Reduced insecticide applications targeting RBSBs will ultimately reduce the cost of production and increase producers net income. Finally, reduced insecticide applications in soybeans will benefit natural enemies, the environment and ultimately human health. |
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Other Products / Outputs **= Publication or presentations by my graduate student Vyavhare S**, M. O. Way, P. Pietrantonio, and R. F. Medina. Insecticide Susceptibility in Redbanded Stink Bug (Hemiptera, Pentatomidae) Populations in Texas Soybean. Pest Management Science. (In preparation) Vyavhare S**. Establishing and Implementing an IPM Program for the Redbanded Stink Bug, Piezodorus guildinii: an Emerging Soybean Pest in the Southern Region. (A chapter in this PhD dissertation was based on this research project) Vyavhare**, S. 2014. IPM of the Redbanded Stink Bug. The Annual Meeting of the Southeastern Branch of the Entomological Society of America. San Antonio, Texas. February 2014 Vyavhare**, S. Way, M., and Medina, R.F. Texas Plant Protection Conference, Population Dynamics and Damage Potential of Redbanded Stink Bug (Piezodorus guildinii) in Soybeans. Oral presentation in the grain section. College Station, Texas. December 2013 |
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