Location: Insect Behavior and Biocontrol Research2021 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.
Over the life of the project, the efforts of the Insect Behavior and Biocontrol Research Unit in Gainesville, Florida, resulted in significant progress and the proposed objectives for all of the major goals of “Improved Biologically-Based Methods for Insect Pest Management of Crop Insect Pests”: 1) TRANSGENIC STUDIES, 2) PARATRANGENIC STRAIN DEVELOPMENT, 3) ACOUSTIC DETECTION, 4) TRAP DEVELOPMENT, and 5) EFFECTS OF CLIMATE CHANGE ON FALL ARMYWORM MIGRATION PATHWAYS were largely fulfilled. Initially, major progress was made by researchers in Gainesville, Florida, Objective 1, to understand the stability of genetic sterile male strains for Sterile Insect Technique (SIT). The rates of mutation in genetic elements used to create tetracycline-suppressible sterile males were characterized as a critical step in determining the long-term usage of these strains. After screening 1.2 million zygotic progeny under non-permissive conditions for embryonic lethality (tetracycline-free diet), heritable survival to adulthood was discovered demonstrating breakdown of the genetic elements. Additionally, an initial transcriptome analysis of early embryos Oriental fruit fly was completed along with an analysis of the role of the micro-RNAs in early embryonic male sex-determination. Objective 2, researchers in 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. The gene editing system can be used to alter various pesticide resistance genes and the effects studied to find mechanisms to avoid or reverse pesticide resistance. In vitro cultured insect cells infected with the endosymbiotic bacterium Wolbachia were microinjected into larvae of the fall armyworm and the Mediterranean flour moth to establish infected strains to be tested for use in Incompatible Insect Technique. The bacteria persisted to the adult stage and were vertically transmitted from the females to offspring. Gene editing was used to create mutations that disrupted and tagged toxin-transporter genes with introduced fluorescent protein markers. Decreased sensitivity to bio-toxins was found in these mutant strains. Objective 3, researchers in Gainesville, Florida, used acoustic technology to monitor the time course of mortality for stored product pest insects placed in hermetically sealed containers. This procedure enables realistic assessments of treatments 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. A prototype acoustic-based mating-disruption trap for the Asian citrus psyllids was constructed incorporating multiple yellow sticky traps containing green light-emitting diodes (LEDs) previously identified by others to be highly attractive to the psyllids. The traps and LEDs were strung on a mating disruption vibration exciter system. The system is ready for testing in citrus groves. Objective 4, researchers in Gainesville, Florida, used the optimal paint pigments to determine enhance attraction of Asian citrus psyllids to conventional yellow sticky traps for monitoring of low-level populations of this pest that vectors the pathogen causing citrus greening disease. These results provide potential for enhancement of current surveillance capabilities for this vector species. Studies on the relative importance of intensity versus the hue of reflected light on attraction of Asian citrus psyllids and corn silk flies were field tested to examine enhancement of responses to the colors. Electrophysiological studies were conducted on the Asian citrus psyllid and two species of corn silk flies to identify photoreceptors contributing to the vision of these insects. Detailed laboratory assays revealed attraction of the Asian citrus psyllid to ultraviolet light-emitting diodes (LEDs) as well as ultraviolet-reflecting pigments which led to using ultraviolet pigments to enhance an attract-and-kill application. An optimal combination of yellow paint and volatile attractants were used to enhance visual traps as well. Traps using multiple modes of stimuli are being prepared for field deployment. Objective 5A, previously developed systems to monitor fall armyworm migration were employed by researchers in Gainesville, Florida, to assess the recent introduction of fall armyworm into Africa and its subsequent spread. 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. Simulations corroborated the spatial distribution and mixing of Texas and Florida source populations defined by genetic haplotypes. Air transport modeling was also used to project fall armyworm movements in Africa, southeastern Asia, the Caribbean, and South America, with the results used in combination with field sampling and genetic analysis to better understand fall armyworm migration behaviors to assess the recent introduction of fall armyworm into sub-Saharan Africa and its subsequent spread in Asia. In this study an international collaboration of scientists provided genetic analysis information on the migratory potential, strain behavior, and invasion history of the pest in Africa, which is critical for future efforts to monitor, predict, and control the spread of this invasive pest in the Eastern Hemisphere. The findings provide insights into invasive moths relevant to understanding similar events in the United States. Objective 5B, a pheromone blend with novel components for fall armyworm was assessed that demonstrated increased attraction of fall armyworm adult males to pheromone traps which will lead to increase trap capture and improve monitoring. Additionally, field assessments of the establishment of a fall armyworm specific parasitoid were made for use as biocontrol agents of this pest moth.