Thrips-transmitted Tomato spotted wilt virus: a constant threat to agriculture in Georgia

Summary

Thrips-transmitted Tomato spotted wilt virus (TSWV) severely affects the production of peanut, tomato, pepper, and tobacco in southeastern United States. Over 800,000 acres are planted each year with the four crops. The crops are valued at well over one billion dollars annually. TSWV is also listed as one of the top ten most destructive plant viruses Worldwide. Though a precise and recent estimate is not available, in Georgia alone, tens of millions are lost due to TSWV annually. Our vector biology program conducts extensive applied research on management of thrips and TSWV, as well as basic research aimed at understanding thrips and TSWV interactions. A most recent concern has been whether there are other thrips transmitted viruses besides TSWV in Georgia.

Situation

TSWV has been a major impediment to peanut, tobacco, and vegetable production since its introduction to the Southeast since the 1980s. There was no available resistance to TSWV back then and losses >90% were common. Due to intense breeding efforts, a number of genotypes displaying optimal levels of TSWV resistance in vegetables and moderate levels of field resistance in peanut have been released. However, in peanut, they still cannot function as standalone options. Due to which, peanut growers besides planting resistant cultivars, rely on applying pre-plant insecticides to manage thrips and TSWV. With the impending withdrawal of the most commonly used broad-spectrum insecticides, such as Temik, peanut growers are seeking alternatives. Concerns (insecticide resistance) have arisen due to the use of alternatives as well. The mechanism of resistance to thrips and TSWV in peanut is unknown, and impacts of using field-resistant genotypes on virus transmission, ecology, and epidemiology are unknown. Though substantial information exists on thrips-Tospovirus interactions, knowledge on these interactions from genetic and molecular standpoints is still nascent.

Response

For the last five years we have been conducting numerous field and laboratory experiments to identify viable alternatives to carbamate and organophosphate insecticides with funding from USDA-NIFA, USDA-NIFA- SRIPM, National Peanut Board, and Georgia Peanut commission. Neonicotinoids have been identified as viable alternatives. The availability of genotypes with moderate levels of field resistance than the previously available cultivars has provided us with more flexibility. We are currently evaluating the compatibility of these second- and third-generation peanut cultivars/genotypes with newer narrow spectrum insecticides, reduced inputs (Seeding rate), and cultural tactics. The neonicotinoid inefficacy has become a concern lately, and is being addressed in our laboratory. A spectrum of experiments was conducted to examine the interactions of TSWV-resistant genotypes with the virus and its vector. These interactions were examined in depth further using transcriptomics at a molecular level. Routine testing is being conducted to monitor the presence of other thrips-transmitted viruses, and also how TSWV is evolving over time and it's potential impact on host resistance.

Impact

Annual losses due to TSWV extend to tens of millions of dollars. However, in recent years, the losses have been considerably low mainly due to Planting TSWV-resistant cultivars and their integration with cultural and chemical tactics. To address the impending loss of some of the effective insecticides in peanut, we conducted research to identify alternatives. Our research from 2011 through 2015 identified a number of newer insecticides with reduced non-target effects and potential to suppress thrips populations and TSWV incidence. Our research also indicated that these new insecticides were indeed compatible with planting of second/third-generation peanut cultivars. Our experiments with various seeding rates indicated that it would be possible to reduce seeding rates of these cultivars without compromising yield benefits. We are incorporating some of these tactics in the Peanut Risk Management Index – a tool that is regularly used by growers to mitigate risks associated with spotted wilt. Neonicotinoid inefficacy has become a recent concern; our laboratory is examining issues such as residual toxicity and insecticide resistance to address those concerns. Our knowledge on how thrips and TSWV interact with each other at a molecular level has also increased substantially. Thrips transcriptomes have been or will be made available through a public database-National Center for Biotechnology Information (NCBI). This information will be available to scientists who work on thrips and tospoviruses Worldwide. This will help further research on vector-pathogen interactions on multiple aspects. Ultimately, downstream research could help design next-generation management tools for thrips and TSWV aimed at increasing sustainability and profitability in peanut and vegetable production in Georgia and elsewhere. Routine monitoring for other tospoviruses helps us to be proactive and prepare for new and emerging problems that may impact our peanut and vegetable industry.

State Issue

Agricultural Profitability and Sustainability

Details

• Year: 2016
• Geographic Scope: State
• County: Tift
• Program Areas:
  • Agriculture & Natural Resources