Location: Insect Behavior and Biocontrol Research2012 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 wiil 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 all the major goals of 6615-22000-025-D 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 genetically modified fruit fly strains whose females fail to develop outside of artificially permissive conditions and so allow production of all-male cohorts for Sterile Insect Technique (SIT) programs. Molecular techniques were under development to induce new genetic combinations into insect endosymbiotic bacteria that will eventually allow the transformation of male parasitoids into more useful females. Such experiments will lead to the effective field release of genetically modified control agents. The migrations of the fall armyworm were described across a broader range and target areas for their area-wide management have been identified. Work continues on applying biological control to these "hot-spots." Migration of fall armyworms from overwintering sites is being used to model the effects of climate change on the distribution 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 internationally. 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, but it is important to discover if pest species exploit the same resources. Surveys identified flowering plants that are relatively attractive to parasitoids but unattractive to Lepidoptera.
1. New genetic modifications yield "sexing strains" in fruit flies. Mass releases of sterile males are a widely used means to control pest fruit flies, but released females do not contribute to control and may absorb the attentions of the sterile males. Conditional-Lethality, where a released insect's offspring die when certain environmental conditions prevail, is a means of eliminating females early in their development and so provide the additional benefit of reducing rearing expenses. A conditionally-lethal strain of the Caribbean fruit fly was created through genetic modifications whose females survive on a diet supplemented with tetracycline, but suffer 100% embryonic lethality in its absence. The genetic constructs involved will serve to improve the efficacy of control programs that protect U.S. agriculture from not only fruit flies but also from other potentially invasive pests.
2. Migration of pest moths modeled. Mitochondrial haplotype frequencies from different fall armyworm strains in southern Texas, Florida and the Caribbean allow migratory boundaries to be identified at a previously unattainable resolution. Seasonal and annual variations can then be correlated with meteorological event to develop air transport models capable of explaining and predicting migratory events, which in turn can be examined under different climate change scenarios. This year surveys and collections of fall armyworm for the mapping of migration pathways were expanded into 15 additional states in the central and northern U.S. and into two provinces in Canada. Models of insect migration will warn growers of impending pest problems and focus control efforts on the relatively small, and therefore vulnerable, source-populations.
3. Genetic transformation of Wolbachia. A transposon based genetic transformation system for Wolbachia was designed and is under development. The recovery of integration mutants is based on mutagenized bacterial stimulating the expression of green fluorescent protein (GFP) in the host cell. The ability to genetically transform the insect endosymiotic bacteria, would allow the development of the thelytokous (all-female) parasitoid strains for augmentative biological control and "cytoplasmic incompatibilities" in fruit flies as an alternative means of sterilization in the Sterile Insect Technique (SIT). Such novel biologically-based controls offer new means to control pests on an area-wide basis and reduce insecticide use around the world.
4. Avoiding the amplification of moth pests. Flowering plants when added to agricultural environments can increase/concentrate natural enemies, but such plants may also provide shelter, food and alternative hosts to pests. While there is a growing body of information on how to sustain parsitoids, the equally important impact of landscape modification on pest Lepidoptera is more poorly studied. The ability of plants to attract moths was compared to their attractiveness to hymenopteran and dipteran parasitioids. Species were identified that provided the most benefit at the least cost; i.e., were highly attractive to natural enemies and relatively unattractive to Lepidoptera. Incorporation of these plants, many of them native and requiring little input, could be part of an integrated pest management program designed to protect crops, especially those grown under organic regimens.
5. Floral lures for cabbage looper moth monitoring. Cabbage loopers and other pest caterpillars constituent a major problem for numerous row and vegetable crops. Many adult moths readily feed on nectar and are attracted to a range of flowers. Using chemicals identified from known nectar sources, several compounds were compared to pheromones commonly used to monitor cabbage-looper populations. Several floral chemicals were more effective. These highly attractive chemicals can increase sensitivity of current monitoring methods leading to optimized timing of pesticide applications and better protection of crops.
6. Detection and monitoring of hidden red palm weevils in urban palm trees. The sounds made by invasive palm weevils as they move and feed within trees were further characterized. It is now possible to distinguish the sounds produced by early-juvenile weevils from background noises or the sounds produced by non-pest insects in and on the palms. This allows the development of acoustic technologies to detect the otherwise invisible pest which can be used to monitor for red palm weevil introduction and/or identify trees that need to be treated or destroyed. Use of this technology will enable earlier detection of infestations, reduce the number of trees that might be cut unnecessarily and limit indiscriminate insectide use.
Cicero, L., Sivinski, J.M., Rull, J., Aluja, M. 2011. Effect of larval host food substrate on egg load dynamics, egg size and adult female size in four species of braconid fruit fly (Diptera: Tephritidae) parasitoids. Journal of Insect Physiology. 57(11)1471:1479.