Location: Insect Behavior and Biocontrol Research2018 Annual Report
Objective 1. Develop new transgenic conditional lethal strains for sexing and sterility in tephritid and drosophilid fruit flies to be used in the sterile insect technique, produce redundant lethality systems for ecological safety, and transgenic technology for emerging pest species such as the Asian citrus psyllid. Objective 2. Develop paratransgenic strains that eliminate the ability of host populations to vector plant disease by using Wolbachia cytoplasmic incompatibility to drive pathogen immunity throughout populations of key pests such as Asian citrus psyllid, glassy-winged sharpshooter, and potato/tomato psyllid. Objective 3. Develop automated acoustic methods for improved surveillance and detection of hidden and invasive pests such as red palm and citrus root weevils and Asian long-horned beetle that will facilitate more rapid information collection/processing by use of big data technologies. Objective 4. Develop improved visual-cue trap systems for surveillance of invasive and outbreak insect pests such as Asian citrus psyllid and corn silk fly, and improve strategies for detecting and predicting the dispersal of these pests by understanding the role of visual and other stimuli in affecting their behavior. Objective 5. Develop predictive models for fall armyworm migration pathways that are shifting due to climate change, and improve area-wide landscape management tactics for these pests by developing cover crop and biological control strategies to control them. Sub-objective 5.A. Develop genetic methods to monitor fall armyworm population behavior and air transport models to describe and predict its migration pathways and potential changes in infestation patterns due to climate change. Sub-objective 5.B. Improve area-wide landscape management tactics by developing cover crop and other strategies to mitigate pest populations such as fall armyworm, and attract or support natural enemies and pollinators.
The experimental approaches to achieve these objectives is multidisciplinary and integrates genetics, ecology, behavior, and engineering to address various stages of control, from molecular genetics leading to autocidal strain development to predicting changes in pest migration in response to global climate change. These approaches will apply, initially, to high priority invasive fruit flies, beetles, psyllids, fall armyworm and corn silk flies, and will include studies for development of molecular genetics methods for gene discovery and manipulation to develop genetically-modified pest strains to suppress wild populations, or eliminate their ability to vector pathogens of plant disease; development of detection and surveillance methods for optimization of acoustic, chemical and visual-cue detectors for detection and surveillance of hidden, invasive and outbreak pests; and biological control studies to develop predictive models to target shifting migrations of noctuid pests in response to climate change, and development of improved area-wide landscape management tactics to mitigate pest populations and attract natural enemies and pollinators.
The research efforts by the Insect Behavior and Biocontrol Research Unit resulted in significant progress towards the five objectives and subobjectives for this project. Major progress was made under Objective 1 to understand the stability of genetic sterile male strains for Sterile Insect Technique (SIT). The natural breakdown of genetic elements used to create tetracycline-suppressible sterile males was characterized as a critical step in determining the long-term usage of these strains. Under Objective 2, gene editing was used in the Indian meal moth and the fall army worm to create mutations in genes that produce transport proteins that are targets of toxin resistance. The gene editing system can be employed to mutate various pesticide resistance genes and the effects studied in order to find mechanisms to avoid or reverse pesticide resistance. Under Objective 3, acoustic technology was used to monitor the time course of mortality for stored product pest insects placed in hermetically sealed containers. This assay enables realistic treatment assessments in situ and provides information that helps farmers who use on-farm storage to predict the time course of insect mortality in different hermetic storage environments under different levels of infestation. Under Objective 4, the optimal paint pigments were determined that enhance attraction of Asian citrus psyllids to conventional yellow sticky traps for monitoring of low level populations of this pest that serves as a vector of the pathogen causing citrus greening disease or Huanglongbing. These results provide potential for enhancement of current surveillance capabilities for this vector species. Major contribution was made under Objective 5A where the previously developed systems to monitor fall armyworm migration were employed to assess the recent introduction of fall armyworm into Africa and its subsequent spread throughout most of sub-Saharan Africa. In this study an international collaboration of scientists led by researchers at USDA-ARS Gainesville, Florida, investigated the migratory potential, behavior, and invasion history of the fall armyworm in Africa, providing information critical to monitor and control the spread of this pest in the Eastern Hemisphere. The findings provide insights into invasive moths relevant to understanding similar events in the United States.
1. Migration of pest and invasive insects. The introduction of invasive pest species and/or deleterious traits (i.e., pesticide resistance) into domestic pest populations poses a continuing threat to agriculture. This is exemplified by the recent introduction of fall armyworm into Africa and its subsequent spread throughout most of sub-Saharan Africa. The voracious feeding and long-distance flight behaviors by fall armyworm pose a significant threat to African agriculture and potent problem for the Eastern Hemisphere. ARS researchers at Gainesville, Florida, led an international collaboration of researchers to investigate the migratory potential, behavior, and invasion history of the fall armyworm in Africa, information critical to monitor and control the spread of this pest in the Eastern Hemisphere. The findings provide insights into invasive moths relevant to understanding similar events in the United States.
2. Genetic breakdown of embryonic conditional lethality systems. The stability of genetic sterile male strains for Sterile Insect Technique (SIT) must be validated before long-term usage of these strains. ARS researchers at Gainesville, Florida, collaborated with those at national and international universities to assess the natural breakdown of genetic elements used to create tetracycline-suppressible sterile males. Heritable survivability was discovered in offspring of eleven individuals from >660,000 adults screened under non-permissive conditions for embryonic lethality (tetracycline-free diet). This provides the first data for the frequency (~6 x 10-6 /generation) and genetic basis for primary site revertants of a Tet-off lethality system. These data suggest that there is a finite usage of these genetic sterile male strains.
3. Enhanced attraction of Asian citrus psyllids to visual targets. The Asian citrus psyllid which serves as a vector of the pathogen causing citrus greening disease or Huanglongbing, is one of the most serious citrus pests worldwide with particularly devastating impacts on the Florida citrus industry. While yellow sticky traps are the standard surveillance method and critical for guidance of pest management strategies, they are not effective when psyllid populations are low. ARS researchers at Gainesville, Florida, have determined optimal paint pigments that enhance attraction of Asian citrus psyllids in the laboratory. One pigment enhanced psyllid attraction over the yellow sticky traps in the field when used by researchers at USDA-ARS Horticultural Research Center, Ft. Pierce, Florida. These results provide potential for enhancement of current surveillance capabilities for this vector species.
4. Acoustic monitoring of pest insect mortality. Hermetic storage is rapidly becoming an important method to protect stored products from pest insects on small farms in underdeveloped countries. Insects in the storage bags consume the oxygen and die, but the time until mortality is not well understood by either farmers or scientists. ARS researchers at Gainesville, Florida, in collaboration with international researchers have used acoustic technology to monitor the time course of mortality of pest insects exposed to management treatments. This enables realistic treatment assessments in situ and provides information that helps farmers who use on-farm storage to predict the time course of insect mortality in different hermetic storage environments under different levels of infestation. Farmers who do not yet use hermetic storage will be more likely to adopt the technology, once they know how long it takes for the insects to die.
5. Gene editing of toxin transporter genes moths. Resistance to toxin-based insecticides has become a major issue for biologically engineered crops. ARS researchers at Gainesville, Florida, used gene editing in the Indian meal moth and the fall army worm to create mutations in genes that produce transport proteins that are targets of toxin resistance. Gene editing of these transporter genes resulted in white eyed moths and pesticide Bt resistance. Using this gene editing system, various pesticide resistance genes can be mutated, and the effects studied in order to find mechanisms to avoid or reverse pesticide resistance.
6. Cover crops and intercrops reduce fall armyworm populations. The fall armyworm moth is a major pest of corn and grass in North America. The moth must overwinter in the most Southern regions and then migrate each spring to repopulate the Northern regions. ARS researchers at Gainesville, Florida, have assessed the use of different plants as cover crops and intercrops to reduce fall armyworm populations. Plots of only sunn hemp plants were uninfested with fall armyworm while in plots with the mixtures, only sorghum-sudangrass plants were infested with fall armyworm. Intercropping corn with mixtures of sunn hemp and sorghum-sudangrass showed no difference in the percent of corn plants infested by fall armyworm. These finding suggest that rotation of corn with sunn hemp will reduce the level of pest infestation without the use of chemical pesticides.
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Li, J., Handler, A.M. 2017. Temperature-dependent sex-reversal by a transformer-2 gene-edited mutation in the spotted wing drosophila, Drosophila suzukii. Scientific Reports. 7:12363. https://doi.org/10.1038/s41598-017-12405-4.
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Nagoshi, R.N., Koffi, D., Agboka, K., Tounou, K.A., Banerjee, R., Jurat-Fuentes, J.L., Meagher Jr, R.L. 2017. Comparative molecular analyses of invasive fall armyworm in Togo reveal strong similarities to populations from the eastern United States and the Greater Antilles. PLoS One. 12(7):e0181982. https://doi.org/10.1371/journal.pone.0181982.
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