Location:2019 Annual Report
Objective 1: Determine risk across landscapes to improve management of pests such as spotted wing drosophila by understanding their behaviors (i.e., host range and preference, dispersal). Obj. 1.1: Describe flight parameters and energy used in flight of spotted wing drosophila. Obj. 1.2: Compare effects of temperature and sugar feeding on spotted wing drosophila. Objective 2: Develop biological control strategies for pests such as spotted wing drosophila, brown marmorated stink bug, and azalea lace bug, using commercially available and endemic natural enemies and habitat conservation. Obj. 2.1: Study endemic natural enemies of spotted wing drosophila, and pupation habits of spotted wing drosophila. Obj. 2.2: Study endemic natural enemies and using the volatile methyl salicylate for brown marmorated stink bug. Obj. 2.3: Study endemic natural enemies, augmentative release and methyl salicylate for azalea lace bug. Objective 3: Develop RNAi technology to control pests such as spotted wing drosophila by finding and evaluating target genes, and developing large-scale production methods. Obj. 3.1: Identify potential RNAi target genes from spotted wing drosophila. Obj. 3.2: Evaluate RNAi impact(s) on development of spotted wing drosophila. Obj. 3.3: Develop large-scale dsRNA production methods. Objective 4: Develop receptor-based drug discovery for pests such as spotted wing drosophila by finding and evaluating insect neuropeptides and receptors to disrupt critical physiological signals in the pests. Obj. 4.1: Cloning and functional expression of the specific G-protein coupled receptors from spotted wing drosophila and other pests. Obj. 4.2: Develop receptor-based screening method.
Objective 1 includes studying spotted wing drosophila (SWD) on a flight mill or other suitable arenas and measuring their nutrient reserves, such that basic flight parameters and energetics can be obtained. For SWD, its movement across landscapes may be influenced by its ability to find resources in the surrounding habitat and temperature and nutrient stores. Objective 2 includes surveying the endemic natural enemies present that attack important pests such as SWD, brown marmorated stink bug (BMSB), and azalea lace bug (AzLB). Trials will determine if the release of predators or use of attractive plant volatiles can improve control of these pests in nursery and fruit crop fields. Objective 3 will identify genes in SWD for RNAi targets, and measure the impact on treatment on SWD longevity and activity. Also, a large-scale method to produce dsRNA will be tested using E. coli with inserted vectors. Objective 4 will screen G-protein coupled receptors that are important in the development or adult stages of SWD, and will clone and test expression of them.
Towards Sub-objective 2.1, research continued on biological control of spotted wing drosophila (SWD). The parasitic wasp, Pachycrepoideus vindemmiae, lays its egg in the pupa of SWD and kills it. ARS researchers in Corvallis, Oregon, are making releases of these wasps in organic blackberries and raspberries planted within hoop houses. The success of these wasp releases is being assessed by monitoring SWD abundance and parasitism rates in hoop houses with and without releases. For Sub-objective 2.2, research continued on biological control of brown marmorated stink bug (BMSB). The Samurai wasp is an effective parasitic wasp of BMSB in its native range of Asia. Now that this wasp has spread to the United States, ARS researchers in Corvallis, Oregon, are developing ways to enhance the Samurai wasp in the field. Out of several floral species that were tested on extending the longevity of the wasp, buckwheat flowers were the most successful. Work is continuing with other floral species and ways to extend the persistence of the Samurai wasp in the field by providing a ‘banker system’ where BMSB eggs are consistently available so that the parasitoid can always lay their eggs and multiply in the field. Towards Sub-objective 2.3, research continued on enhancing biological control of azalea lace bug. Green lacewings are commonly occurring predators of azalea lace bugs. ARS researchers in Corvallis, Oregon, are testing several combinations of herbivore-induced plant volatiles, which turn on chemical plant defenses as well as attract natural enemies, to determine if the green lacewing can be recruited to rhododendrons infested with azalea lace bugs. Supplementation with silicon is also being tested to determine whether rhododendrons absorb this element and if the incorporation of silicon into plant tissues will have a negative effect on the azalea lace bug population. Finally, rhododendron cultivars are being tested to determine if some are more attractive to azalea lace bug than others. Research continued to evaluate RNA interference (RNAi) impact on the development (i.e. fecundity or mortality) of SWD. RNAi is a convenient tool to identify and characterize biological functions in organisms and has become an alternative to chemical insecticides as a biologically based control agent. This promising technology has the potential to avoid many problems associated with conventional chemical insecticides. ARS scientists in Corvallis, Oregon, synthesized and purified dsRNAs (RNAi material) for 30 genes of SWD using an in-vitro system. These were injected into the adult flies with a nano-injection system under a microscope and monitored their potential impacts. From this, a specific RNAi target was identified that had a 60 percent mortality rate on the fly (Sub-objective 3.2). For RNAi application to be practical for growers to use in insect pest management, there needs to be a system for producing double-stranded RNA (dsRNA) in large quantities. ARS researchers in Corvallis, Oregon, inserted recombinant L4440 plasmid vectors into E. coli strain HT115 cells to produce dsRNA (Sub-objective 3.3). This microbial-based dsRNA production system provides a more practical application by producing dsRNA in bacteria that can be ingested by insects. This has potential for making applied RNAi technology a feasible option for pest management in field applications. For Sub-objective 4.2, research continued to treat SWD with phage peptides to reduce their biological activities and/or longevity. New genomics/proteomics technologies allow us to screen functionally new receptor-based targets, such as neurohormones and G-protein coupled receptors (GPCRs). Insect neurohormones and their receptors are more than 90 percent of total insect hormones. They are activated by a wide variety of stimulants, including light, odorant molecules, peptide and non-peptide neurotransmitters, hormones, growth factors and lipids, and control a wide variety of physiological processes, including sensory transduction, cell–cell communication, neuronal transmission, and hormonal signaling. GPCRs are membrane embedded proteins, also known as 7-transmembrane receptors. ARS researchers at Corvallis, Oregon, established a novel receptor interfering (receptori) technology using an insect cell-based expression system and phage displayed peptides to screen bioactive small peptides for the SWD control.
1. Efficacious biological control of spotted wing drosophila. Spotted wing drosophila is a serious economic pest of small fruits and cherries. While biological control is a non-toxic alternative, it is a challenge for growers to know which biological approaches to use. ARS scientists in Corvallis, Oregon, led a collaborative effort with scientists from California, Delaware, Georgia, and Michigan, in reviewing more than 75 articles on biological control to provide a comprehensive and usable database on the effectiveness of biological control agents. This database is available online at the Journal of Integrated Pest Management and enables growers to select efficacious biological control agents to manage economically important insect pests.
2. Non-toxic sugar-based control for spotted wing drosophila. Spotted wing drosophila is an economic pest of fruits and commonly managed by chemical insecticides which have negative impacts. ARS scientists in Corvallis, Oregon, are developing a sugar formulation to kill this pest that is non-toxic to humans. They tested various formulations of erythritol, mixed with sucrose or low doses of a compound (patent pending), and demonstrated that it kills the fly by starvation and causing water imbalance. This erythritol formulation can be an insecticide used alone or combined with conventional or biological insecticides to enhance their efficacy. The compound can be used by companies to produce a non-toxic insecticide or used by growers as part of their integrated pest management program.
3. Control of azalea lace bug with non-toxic alternatives. The azalea lace bug is an economic pest of azaleas and rhododendrons. Landscape managers need softer control methods to use in areas with high public exposure and runoff to waterways. ARS scientists in Corvallis, Oregon, in collaboration with scientists in Oregon, found that water sprays were effective at dislodging adults and nymphs from leaves, and subsequent predator releases controlled hatching lace bugs. Also, this pest was found to have three generations per year, overwinter primarily in the egg stage, and egg hatch occurred in April/May. Growers and managers can use water sprays in their landscapes and nurseries, and time their management practices to target first egg hatch.
4. Bacteria-based double-strand RNA (dsRNA) production. RNAi is a new technology that can provide species-specific control by blocking replication of critical genes in the target pest. However, large-scale application requires mass production of dsRNA, which can be very costly. Therefore, ARS scientists in Corvallis, Oregon, developed a microbial-based production system for providing large quantities of dsRNA. The isolation methods to obtain dsRNA from crude and purified bacterial cultures were determined and evaluated. This production method can potentially generate ample dsRNA for a biologically-based pest management tool for growers.
5. Convenient rearing of the beneficial samurai wasp. The brown marmorated stink bug (BMSB) is a worldwide pest that attacks over 200 different types of host plants. The samurai wasp is a natural enemy of the stink bug; they help lower this pest population by colonizing (laying their own eggs inside of) stink bug eggs. The downside is that in order to mass-rear samurai wasps, a large quantity of BMSB eggs need to be readily available, which can be a laborious process. ARS scientists in Corvallis, Oregon, in collaboration with other scientists in Oregon, found that frozen stink bug eggs can be conveniently used for rearing large numbers of these beneficial insects without detriment to the health or size of the ensuing colony. This will result in the ability of practitioners to easily rear large numbers of samurai wasp colonies in order to protect key agricultural crops from brown marmorated stink bug damage.
6. Screening of bioactive peptides on pest slugs. In Oregon, both native and invasive species of slugs attack a broad spectrum of agricultural industries including seed production, field crops, and horticultural nurseries. The cost of bait applications, replanting, and direct loss of plants is estimated to cost the seed industry over $50 million per year. ARS scientists in Corvallis, Oregon, discovered small peptides (5-7 amino acids) having detrimental effects on pest slugs, such as the gray garden slug. The result of these findings will lead to the development of a biologically-based approach in the next generation of control methods for pest slugs.
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