Location: Insect Behavior and Biocontrol Research2011 Annual Report
1a. Objectives (from AD-416)
1. Genetics: Identify developmentally significant genes from whole genome and transcriptome sequencing projects that may be targeted or manipulated in transgenic and nontransgenic insect strains for biological control. Test conditional lethal systems using cell death genes and microRNAs targeted to embryos and vital processes in tephritids and lepidopterans and develop germ-line transformation for the cactus moth and Asian citrus psyllid. 2. Detection and attraction: Develop chemical and acoustic detection and attraction systems for pest species and natural enemies: specifically develop trapping systems using floral-derived volatiles to monitor and/or eliminate pest populations and monitor dispersal of augmented parasitoids, detect acoustic signals produced by cryptic/hidden pests for targeted control, and improve detection efficiency through automation. 3. Biological control: Develop strategies for use of parasitoids and predators in IPM of insect pests through behavioral, ecological and physiological studies of their feeding, mating,dispersal and oviposition: Specifically target conservation biological control on overwintering reservoirs of migratory fall army worm and other pests; develop thelytokous strains of fruit fly parasitoids for augmentative biological control, and develop Asian citrus psyllid diets that will facilitate the mass-production of hosts for mass-rearing parasitoids for augmentative parasitoid releases and other forms of biologically-based control; and develop predictive models of pest migration that incorporate climate-change and facilitate the targeting of vulnerable populations.
1b. Approach (from AD-416)
New biocontrol strategies will be based on transgenic strains that confer conditional lethality, so that insects can be mass reared under permissive laboratory conditions, while their offspring die in the field under nonpermissive conditions. The tetracycline-suppression (tet-off) embryonic conditional lethality system consists of an embryonic driver construct and a lethality inducing effector construct both integrated by piggyBac transposition into a host genome. To develop RNA inhibition (RNAi) strategies for the conditional genetic constructs gene homologues will be identified, then inhibitory FAW RNAi constructs will be incorporation in artificial media. Recombinants expressing these constructs will be tested and effective constructs introduced. To precisely target populations of hidden/cryptic pests distinctive spectral and temporal patterns of acoustic signals will be identified. Insect detectability will be optimized by constructing customized attachments or waveguides connecting the sensors to the substrates. Automated systems can be developed that remotely detect, identify, and count specific pests based on the spectral and temporal patterns of signals. An automated system for trapping C. capitata will consist of a lure and a microphone connected to a signal acquisition andanalysis system attached by cable or wireless to a computer. To develop food/host based attractants for opiine braconid fruit fly parasitoids to monitor augmentative releases and to stimulate oviposition volatiles produced by fruit fly larvae, infested fruits and nectar-sourcesare parasitoids to locate hosts, host-habitats and adult food will be identified and formulated into appropriate lures and additives. To develop floral attractants and pheromones for monitoring and/or control of adult lepidopterous pests research will concentrate on phenylacetaldehyde (PAA) plus ß-myrcene, cis-jasmone, benzyl acetate and additional candidate identified by field surveys. Lures will be first tested in flight tunnels and then in the field. To develop thelytokous strains of fruit fly parasitoids for augmentative biological control, Wolbachia-infected parasitoid surveys will be based on the theory that asexual populations are more persistent in biologically less diverse environments. To develop improved control strategies for lepidopteran pests that recruit natural enemies, combinations of resistant crops and plants supporting natural enemies will be compared in the field using sentinel plants and a split plot arrangement of treatments. To predict the spatial and temporal shifts in infestations of migratory noctuid pests that result from climate change and to target controls, genetic markers will be used to identify source populations from which migratory pathways can be derived, and historical changes in these pathways explained with meteorological and climatic data.
3. Progress Report
Progress was made in the all the major goals of 6615-22000-025-00D Biologically-Based Technologies for Management of Crop Insect Pests in Local and Area-Wide Programs, identification of pest populations and their dispersal, discovery of new biological control agents, their mass-rearing and release. In particular, research advanced the creation of genetic modifications that can induce fruit fly male sterility for Sterile Insect Technique (SIT) programs, but which do not require debilitating irradiation of released males. Technology for inducing new genetic combinations through viruses was transferred to a number of other laboratories, and a new means of adding genes to the body of an insect has been developed. In collaboration with APHIS, a genetic marker that identifies a fruit fly as mass-reared and sterile was found to be stable in a number of trap types. Such experiments will lead to the effective field release of genetically modified control agents. The migrations of the fall army worm were described in finer detail and target areas for their area-wide management have been identified. Work continues on applying biological control to these “hot-spots”. Migration of fall army worms from overwintering sites is being used to model the effects of climate change on the distributions of pests. Chemical attractants are not useful in some situations where pests are hidden and immobile, such as when they infest, grain or wood, but their presence can still be discovered through the sounds they make as they feed. Acoustic pest identification techniques continue to be applied domestically and overseas and Aruba/Curacao. Fruit fly parasitoid host-based oviposition stimulants were identified which could improve production in mass-rearing facilities. Conservation biological control is enhanced by providing food and shelter for natural enemies and continuing surveys have demonstrated that certain plants provide food and alternative hosts for both insect predators and parasitoids.
1. Identifying the origin of migratory moths. Targeting and then controlling migratory populations of the fall armyworm at their source requires discriminating between two host strains that can only be distinguished by a difficult and expensive molecular technique. A new method was developed for strain identification using a nuclear gene that avoids the need for DNA sequencing. It was used to demonstrate the presence of the two strains in Argentina and was more accurate than the alternative analysis. This new method is being applied to migration studies in the U.S. and will facilitate development of strategies to monitor, predict, and ultimately control the movements of these highly mobile pests.
2. RNAi for gene silencing. The ability to silence, turn-off, genes critical for digestion and other critical body functions in insects requires an efficient delivery of RNA “interference” molecules. Five new, highly susceptible target genes were identified in the corn earworm and fall armyworm. Vectors, molecular constructs that can deliver interfering RNAs, were made and tested for efficacy. This is a first step in the production of highly specific pesticide, one that would have no effect on humans, beneficial insects or any other organism.
3. Detection and monitoring of hidden red palm weevils in urban palm trees. Acoustic methods were implemented in Curacao and Aruba for use in monitoring programs against the red palm weevil. Techniques were developed that successfully distinguished the motion and feeding of the beetle from background noises and the sounds produced by many of the other nonpest insects commonly present in the trees. Use of these methods will enable faster inspection of palm trees and reduce the numbers of trees that might be cut unnecessarily.
4. New genes for lethality in fruit flies. Mass releases of sterile males are a widely used means to control pest fruit flies, but the radiation that sterilizes males often damages their sexual performance as well. Conditional-Lethality, where a released insect’s offspring die when certain environmental conditions prevail, is a promising substitute for traditional sterility. A successful conditional-lethality strain for the Caribbean fruit fly was created that survives on a diet supplemented with an antibiotic, tetracycline, but suffers 100% embryonic lethality in the absence of the antibiotic. The genes involved will serve to improve the efficacy of control programs that protect US agriculture from not only fruit flies but also from other potentially invasive pests.
5. Conservation of parasitic flies. Pests can be suppressed by increasing or concentrating natural enemies, and one means of providing them shelter, food and alternative hosts is to add non-crop plants to agricultural environments. While there is a growing body of information on how to sustain parasitic wasps, the equally important parasitic flies are virtually unstudied. Plants were identified that attracted particular families, subfamilies and even genera of such flies. Incorporation of these plants, many of them native and requiring little input, could be part an integrated pest management program designed to protect crops, especially those grown under organic regimens.
Nagoshi, R.N. 2011. Artificial selection for developmental rates in fall armyworm (Lepidoptera: Noctuidae) and its implications on the design of feeding studies. Annals of the Entomological Society of America. 104(1):88-94.