Project : USDA ARS

ARS Home » Southeast Area » Gainesville, Florida » Center for Medical, Agricultural and Veterinary Entomology » Insect Behavior and Biocontrol Research » Research » Research Project #439207

Research Project: Improved Biologically-Based Methods for Management of Native and Invasive Crop Insect Pests

Location: Insect Behavior and Biocontrol Research

2022 Annual Report

Objectives
Objective 1: Develop genetically modified (GM) strains by transposon and CRISPR/Cas-mediated transgenesis for improved SIT in fruit fly pests, and new DNA delivery systems to apply this technology to a wider range of insect, including emerging pest species (e.g., caribfly, mexfly, medfly, spotted-winged drosophila). Objective 2: Develop strains of moths transinfected with Wolbachia that produce males with strong cytoplasmic incompatibility for use in the Incompatible Insect Technique (IIT) to reduce pest populations of fall armyworm and corn earworm. Objective 3: Develop CRISPR gene editing in pest moths (e.g., Indian meal moth, fall armyworm, gypsy moth) that target genes critical for acquired biopesticide resistance using both whole insects and cultured insect cells. Objective 4: Develop improved surveillance and detection methods for hidden and invasive pests (e.g., red palm and citrus root weevil, Asian long-horned beetle, Asian citrus psyllid, and stored product insect pests) that incorporate automated collection, processing, and analysis of insect acoustic signals and behavioral activity. Objective 5: Develop improved surveillance of invasive and outbreak insect pests (e.g., corn silk flies and kudzu bug) using visual-cue traps, and improve strategies for detection and prediction of such dispersing pests by understanding the role of visual and other stimuli affecting specific behaviors. Objective 6: Improve area-wide landscape management tactics by developing conservation biological control strategies to mitigate pest populations and attract or support natural enemies (e.g., against fall armyworm). Objective 7: Combine genetic methods with air-transport and climate modeling to describe and predict the distribution and behavior of agricultural pests to facilitate the mitigation of migratory source populations and to identify locations at high risk for infestations by invasive species such as fall armyworm, corn silk fly, soybean looper, Old World bollworm, and corn earworm.

Approach
Research conducted by the Behavior and Biocontrol Research Unit at the Center for Medical, Agricultural and Veterinary Entomology has historically been focused on the development of novel technologies that improve the cost-efficiency of traditional pest control strategies as well as provide environmentally benign alternatives to the use of chemical pesticides. The goals are to improve crop productivity while reducing the environmental impact and costs of pest management. The proposed research integrates different levels of biology that range from the genetic modification of pest insects to generate novel and improved variations of Sterile Insect Technique (SIT) strategies, the manipulation of pest endosymbionts to develop Insect Incompatibility Technique (IIT) strategies, the optimization of acoustic, olfactory, and visual cues to improve pest surveillance and disrupt pest behavior, the application of climate and air transport models to project pest distribution and migration patterns, and the development of landscape strategies for sustainable mitigation of pest populations. This multidisciplinary structure encourages innovation and facilitates synergism between projects. Anticipated accomplishments will initially apply to the control of high priority invasive fruit flies, beetles, psyllids, moths, and corn silk flies through new biologically based methods for pest control, improved capability to monitor pests, and better projections of pest movements to more effectively target the time and place of treatments. The impact will be higher productivity at lower cost for domestic agriculture and new and improved tools to detect and control emerging native and invasive pests.

Progress Report
Progress was made by ARS scientists at Gainesville, Florida, on project objectives which fall under National Program 304, Component 3, Insects and Mites with activities focusing on Problem 3A, early detection prediction and monitoring of beneficial and pest arthropods; Problem 3B, developing new or improved management tools and knowledge to control arthropod pests; Problem 3C, integrating management strategies to control arthropod pests; and Component 4, Problem 4A, protection of postharvest commodities, quarantine and methyl bromide alternatives and Problem 4B, improving and developing postharvest and quarantine treatments. Under Objective 1, research was continued to discover genes required to construct to genetically modified lines of important fruit fly pests (Caribbean fruit fly, Mexican fruit fly, and spotted wing Drosophila) that can be used for more efficient sterile insect technique strategies of pest control. For Objective 1.1, embryonic expression of specific modified genes in two species of Drosophila have been has verified. For Objective 1.2, further research was conducted to find male sperm specific targets for causing sterilization or mortality. Several targets were verified from Anastrepha suspensa and D. suzukii. Gene-editing conducted to create null mutations for these sequences was initiated to verify their role in male fertility and to identify guide RNAs for a targeted sterility strategy. In support of Objective 1.3, germ-line transformation to locate and utilize dominant temperature sensitive female-specific lethality in A. suspensa was initiated and a gene vector is being developed to result in expression of a gene that will result in female-specific lethality at 29C. No progress was made in Objectives 2 and 3 due to the retirement of a research scientist. Prototypes of detection, trapping, and mating disruption systems for the Asian citrus psyllid were developed for Objective 4. Deep learning algorithms were used to make progress on identification and analysis of differences between male and female vibrational courtship calls of Asian citrus psyllids. Male and females produce variable signals with overlapping durations, amplitudes, and frequencies, however the algorithms helped detect characteristic differences in female frequency and amplitude that changed at end of the call. In environments where many males and females are present on a tree, detection of these differences is important. Characterization of these calls can provide the basis for development of mating disruption strategies. In Objective 5, progress continued with field tests with visual traps that revealed trap color preferences by two species of cornsilk flies when evaluated in corn fields. Volatiles identified from sweet corn varieties were tested in two-choice assays to determine the role of individual and mixtures of compounds in attraction of male and female cornsilk flies. Various food sources and their known associated volatiles were also screened in two-choice assays to determine candidate attractive compounds or sources to serve as attractants for traps in field tests. Candidate extracts for sex pheromones screened for attraction of either sex of two cornsilk fly species revealed attraction and are being further examined. Laboratory assays for evaluation of attraction responses of kudzu bugs were developed and are being used to evaluate both visual and olfactory attractants. For Objective 6, both laboratory and field research provided evidence that the earwig, Labidura riparia, and spider, Oxyopes salticus, are active predators of fall armyworm in spring-planted corn. Specifically, laboratory observations showed that adult earwigs attack and feed on eggs through 4th stage larvae of fall armyworms and spiders feed on both early-stage larvae and eggs. Under Objective 7, significant progress was made on research of genetic markers of the fall armyworm focused on sequences from mitochondria as well as from the triosephosphate isomerase gene. These markers allowed a more refined description of how fall armyworm populations are distributed in both the Western and Eastern hemispheres.

Accomplishments
1. Deep learning algorithms were used to improve detection of the Asian citrus psyllid. The Asian citrus psyllid serves as the vector of the pathogen causing huanglongbing with devastating effects on the Florida citrus industry. The early and accurate detection of the Asian citrus psyllid on young trees and in orchards can facilitate tree protection and targeted control efforts. ARS scientists in Gainesville, Florida, used deep learning methods to identify and characterize differences between male and female psyllid courtship calls. In addition to providing a method of differentiate males and females in infestations, this data has the potential for the development of vibration-based methods of mating disruption for control. Such a behavior-based control approach can help reduce use of pesticides for management of Asian citrus psyllids.

2. Differences in insecticide resistance in fall armyworm populations in the southeastern United States have potentially important consequences for control. Large populations of fall armyworm reported from grazing pastures and hay fields in Louisiana, Mississippi, Texas, and Arkansas, raised concerns of insecticide resistance. Using larval populations collected from different host plants in Louisiana, Georgia, and Florida, an ARS entomologist in Gainesville, Florida, tested the populations using an insecticide contact larval bioassay. Results indicated that fall armyworm populations collected from turf grass in Florida were highly resistant to several pyrethroid insecticides, whereas those populations collected from field corn in Georgia and Florida, and pasture grass in Louisiana were moderately resistant. Our work has shown that synthetic pyrethroid insecticides may not be effective against fall armyworm in pasture habitats.

3. A new introduction of fall armyworm into Africa was identified through the use of newly developed genetic markers. Previous studies by ARS scientists in Gainesville, Florida, demonstrated that only the fall armyworm strain specific to corn and sorghum, was present in Africa, therefore limiting the potential crops at risk of infestation. New studies from these scientists found evidence for a more recent introduction of fall armyworm, indicating that the continent is also at risk for the establishment of the fall armyworm strain specific to millet, alfalfa, and forage grasses. This represents a significantly greater impact of the fall armyworm as a threat for crop production in Africa and thus of heightened concern to African farmers and to U.S. and international aid groups.

4. Pupal parasitoids with potential for cornsilk fly control. Cornsilk flies (Ulidiidae: Tephritoidea) are important economic pests of sweet corn due to direct damage caused by larvae in developing ears of corn. Insecticidal control is limited due to insecticide resistance, withdrawal requirements before harvest and protection of developing larvae under corn husks. An ARS scientist in Gainesville, Florida, evaluated several species of pupal parasitoids for control of cornsilk flies. In this laboratory study, three solitary parasitoid species and two gregarious species were evaluated with all species developing and providing up to 85% mortality of cornsilk fly pupae. Several parasitoid species were also adept in locating and parasitizing pupae buried in different soil types. Pupal parasitoids appear as a promising alternative management tool for this pest group and a means to slow insecticide resistance development.

U.S. DEPARTMENT OF AGRICULTURE

Insect Behavior and Biocontrol Research: Gainesville, FL