Project : USDA ARS

ARS Home » Northeast Area » Beltsville, Maryland (BARC) » Beltsville Agricultural Research Center » Invasive Insect Biocontrol & Behavior Laboratory » Research » Research Project #439455

Research Project: Sustainable Insect Pest Management for Urban Agriculture and Landscapes

Location: Invasive Insect Biocontrol & Behavior Laboratory

2021 Annual Report

Objectives
Objective 1: Discover, characterize, develop and/or promote field adoption of pheromones and other behavior-modifying semiochemicals of key vegetable and fruit insect pests such as cucumber beetles, crucifer flea beetles, stink bugs, squash bugs, and spotted-wing drosophila. Objective 2: Characterize and evaluate native and non-native biological control agents for management of key vegetable pests such as stink bugs, squash bugs, & leaf-footed bugs. Objective 3: Decipher genomes, biochemical and molecular processes of invasive insect pests in order to mitigate damage by crop and landscape pests, such as stink bugs, gypsy moth, and other invasive species. Objective 4: Discover and develop microbial and molecular-based biopesticide agents for control of invasive forest and crop insect pests such as gypsy moth and true bugs, and including model species for evaluation. Objective 5: Utilize molecular approaches to enhance plant defense against destructive insect pests by manipulating the plant defense pathways and insect microflora with a focus on cole crop pests such as those of cabbage and broccoli.

Approach
The project brings together a research team with diverse expertise for multiple approaches to insect management. The proposed project will focus on control of key insect pests in small farms, urban gardens and landscapes, both organic and non-organic. Biobased integrated pest management approaches to be developed will include: (i) discovery and deployment of natural insect attractants and repellents; (ii) conservation and augmentation of beneficial insects; (iii) pest-specific microbial controls [bacteria (including Bacillus thuringiensis strains and Chromobacterium spp.) and baculoviruses]; and, (iv) crop genetic resistance using molecular-based gene discovery. Research will target insect pests that cause major damage to key crops such as cucurbits and cole crops, although other important crops such as small fruit, beans, and potatoes may receive attention for specific problems. Research will also include insect pests that cause major damage to woody plants in the urban landscape. The combination of semiochemical approaches, biological controls, molecular techniques, and crop resistance, will offer a range of non-chemical tactics useful to integrated pest management strategies for major pests in small farms, urban gardens and landscapes.

Progress Report
Subobj.1A: Discover, characterize & develop aggregation pheromones ARS scientists in Beltsville, Maryland, led field deployment of the previously synthesized striped cucumber beetle aggregation pheromone, vittatalactone, in eight states during 2020. Vittatalactone is attractive to other cucumber pests as well, including its western sister species. Male and female striped cucumber beetles both showed strong dose-response to vittatalactone lures, and a ground-level boll weevil trap was found the most efficient means of capture. Field research during 2021 concentrates on best deployment for pest suppression, including timing, placement, and combination with cucurbitacin-containing baits for an attract-and-kill approach. During field season 2020 in Maryland and South Dakota, trapping of 2 crucifer flea beetle species confirmed the compatibility of the two pheromone components, and the added value of the commercially available plant attractant, allyl isothiocyanate. This is significant for monitoring and possible control of both species in cole crops and canola. ARS chemists in Beltsville, Maryland, made significant progress in developing a new synthesis of the flea beetle pheromone (+)-(6R,7S)-himachala-9,11-diene based on the (-)-a-himachalene obtained by fractional distillation of essential oil. Currently, there is no commercial production; the new synthesis developed is a 2-step process using epoxidation and dehydration reactions; work is underway on optimizing yield. ARS scientists in Beltsville, Maryland, showed that, in addition to the previously identified male-produced aggregation pheromone, Colorado potato beetle females have a pheromone attractive only to males, with field attraction of the same order of magnitude. This 2-way communication demands a different approach for field pheromone deployment against this key potato pest. Efforts are underway to identify the female-produced sex pheromone(s), and with field experiments in different crop environments. Subobj.1B: Develop semiochemical formulations for deployment in pest management Two chemicals deposited by brown marmorated stink bug affect the behavior of parasitoids searching for its egg masses. Results from Delaware and Maryland 2020 field tests by ARS scientists showed the value of tridecane but also the need for improved time-release methods. In 2021, experiments will employ more effective time release, as well as methods capable of detecting potentially deleterious hyperparasitoids recently invasive to North America from Asia. Subobj.1C. Identification of fruit-based attractants in SWD management ARS scientists in Beltsville, Maryland, identified spotted-wing drosophila attractants and repellents. Field tests using the push-pull strategy were conducted in the blueberry fields during field seasons 2020 and 2021. Obj.2: Characterize & evaluate biological control for stink, squash, & leaf-footed bugs ARS scientists in Beltsville, Maryland, studied the host preference of the important egg parasitoid, Gryon pennsylvanicum, on 3 coreid bugs, Anasa tristis (squash bug), Anasa armigera (armored squash bug), and Leptoglossus oppositus (leaf-footed bug), showing the parasitoid may prefer L. oppositus to the two squash bug species in paired choice tests. The parasitoid may thus play a role in suppressing populations of L. oppositus and related Leptoglossus species which are pests of vegetable, fruit and seed crops. Gryon pennsylvanicum may also have host plant preferences that are also under study. Seasonal parasitism patterns of G. pennsylvanicum on squash bug over 6-years show zero to low parasitism in the early season but often high rates during the late summer, suggesting that augmentative releases in May-June could improve biological control. Collaborators at Virginia Tech are undertaking experimental augmentation at multiple locations to determine the value of this method for season-long squash bug suppression. Preliminary field results indicate that synthetic lures based on host cues can improve the efficacy of G. pennsylvanicum against squash bugs; this research is continuing. Subobj.3A: Sequence, assemble, annotate, characterize, & compare reference-quality genomes for hemipteran & lepidopteran pests ARS scientists in Beltsville, Maryland, Montpellier, France, and Hilo, Hawaii, initiated whole insect genome libraries for PacBio-based sequencing of single individual H. halys, Bagrada hilaris, Murgantia histrionica, Podisus maculiventris, and Megacopta cribraria as part of the Ag100 component of i5k http://i5k.github.io/ag100pest. Flow cytometry-based genome size estimates are currently being generated by collaborators at Texas A&M University. ARS scientists in Beltsville, Maryland, collaborated with scientists from Université Laval, Natural Resources Canada, and University of British Columbia researchers to generate full genomes and conduct comparative genomics of European and Asian gypsy moth subspecies, including identification of conserved gene families in the species. Subobj.3B: Comparative transcriptomics for major pest insects ARS scientists in Beltsville, Maryland, analyzed the bagrada bug transcriptome, after a setback when the vendor mixed up original samples but then reprocessed libraries. Bagrada bug's glutathione S-transferase and carboxylesterase genes are being phylogenetically analyzed in comparison with select hemipteran and coleopteran genes. University of Tennessee Health Science Center collaborators will analyze the host's complement of cytochrome P450 genes. ARS scientists in Beltsville, Maryland, and at the Sino-American Biological Control Laboratory, Beijing, China, examined small non-coding regulatory RNAs associated with the beneficial predaceous pentatomid Arma chinensis. A total of 64 small noncoding microRNAs that regulate gene expression were newly identified across five nymphal instars. This information could lead to understanding miRNA potential roles in A. chinensis, valuable to biological pest control. In collaboration with Virginia Tech, ARS scientists in Beltsville, Maryland, characterized a family of seven isoprenyl diphosphate synthase-like genes from the brown marmorated stink bug as to their gene structures, genomic organization and co-expression patterns with other genes. Subobj.4A: Discover & characterize bacteria producing insecticidal toxins ARS scientists in Beltsville, Maryland, made significant progress on genomic characterization of IIBBL Bt collection strains. Full genomes of ca. 30 Bt isolates from the collection were analyzed to determine their cry gene content and multilocus sequence types, the latter allowing attribution to classical serovars, e.g., kurstaki and israelensis. Based on whole-genome alignment methods, one of these isolates is an undescribed species within the Bacillus cereus group with genes encoding apparent novel Cry proteins, with only 40-60% amino acid identity with known Cry proteins. As part of a multi-lab NIFA project to identify and develop Bt toxins effective against the Asian citrus psyllid, genomes of 16 Bt isolates from the IIBBL collection that had been assayed for activity against psyllids were extensively analyzed for genes encoding insecticidal toxins. In collaboration with ARS scientists in Byron, Georgia, the identity of a Serratia isolate obtained from pecan weevil pupal cells was determined by whole-genome alignment methods. The isolate, which inhibits the growth of Beauveria bassiana, was found to be conspecific with S. nematodiphila, symbiont of entomopathogenic nematodes. Subobj.4C: Discover new baculovirus-based biopesticide agents ARS scientists in Beltsville, Maryland, determined genome sequences for 6 alphabaculoviruses, 1 betabaculovirus, and 1 gammabaculovirus. Two alphabaculoviruses and the betabaculovirus isolate were undescribed species. Isolates 185 & 600 (from zebra caterpillar, Melanchra picta) & 1420 (from satin moth Leucoma salicis) were variants of alphabaculoviruses found in bertha armyworm, Mamestra configurata. Isolate 524 was a mixture of two alphavirus variants from cabbage looper (T. ni) and common emigrant (Catopsilia pomona). Isolates 524 & 600 exhibited insecticidal activity against cabbage looper larvae in bioassays, but not diamondback moth, Plutella xylostella. Subobj.4D: Develop molecular-based biopesticides targeting hemipteran & lepidopteran pests ARS scientists in Beltsville, Maryland selected differentially expressed transcripts from Bagrada hilaris as gene targets for the development of dsRNAs to induce detrimental effects in vivo, as well as genes identified as endogenous constitutively expressed in all life stages, to be used as internal controls. Target amplifications were successfully completed, resulting in double double-stranded RNA samples for RNAi injection and feeding studies. ARS scientists in Beltsville, Maryland, participated in the Busseola fusca international research forum led by scientists at Reed College, Portland, Oregon. They developed a comprehensive annotated transcriptome of pest maize stalk borer responsible for massive crop losses in Africa. The assembly and annotation results represented a key step towards identifying candidate genes for the control and mitigation of infestations by B. fusca. Obj.5: Utilize molecular approaches to enhance plant defense against insect pests ARS scientists in Beltsville, Maryland, worked on developing a method for the Identification of cabbage varieties resistant versus susceptible to T. ni (cabbage looper pest) and determining the influence of insect microflora on the infestation response. A bioassay was developed for cabbage infestation, which required staging T. ni larvae on uniformly grown plants, conducting multiple replications, and assaying multiple time points to identify genes that were affected by T. ni. Differential gene expression patterns among infested cabbage varieties will be quantified using RNA-Seq.

Accomplishments
1. Discovery of additional safer pesticides. Over the past twenty years, botanic pesticides have received acclaim and recognition as attractive alternatives to synthetic pesticides for pest management due to their reduced threat to human and environmental health. In 2018 ARS scientists in Beltsville, Maryland, showed a volatile organic compound (VOC), methyl benzoate (MB), from fermented apple juice, exhibited significant insecticidal activity against the invasive fruit-infesting fly, spotted wing drosophila (SWD). ARS scientists in Beltsville showed some MB analogs would kill or repel many insects and non-insect pests in various stages of development, including mosquitoes, bed bugs, fire ants, ticks, flies, moths, and nematodes, by contact or as a fumigant. These MB analogs will provide growers with an environmentally friendly alternative to synthetic pesticides for managing insects and non-insect pests and have great potential to be used as safe pesticides for human protection.

2. Full insect genome for the European gypsy moth subspecies, Lymantria dispar dispar (Sparks et al. 2021) generated, analyzed, and annotated. Gypsy moth North American forest and landscape pest has been the topic of several recent, high-profile news reports because of greatly increased APHIS interceptions of Asian origin gypsy moth egg masses and larvae at U.S. ports around the country. This USDA-lead project involved Canadian Forest Service as well as an international consortium of leading gypsy moth University researchers to produce a genome superior in quality to all known assemblies. It also resulted in an assembly and annotation pipeline that advances the state of the art in insect genomics; this pipeline was used to describe the gypsy moth gene space more thoroughly and accurately than had been done in previous studies and may greatly increase our capacity to identify susceptible genetic targets of biological control agents, identify markers of hybrid European/Asian individuals, and advance comparative Lepidopteran genomics.

U.S. DEPARTMENT OF AGRICULTURE

Invasive Insect Biocontrol & Behavior Laboratory: Beltsville, MD