De novo formation of an aggregation pheromone precursor by an isoprenyl diphosphate synthase-related terpene synthase in the harlequin bug.

Insects use a diverse array of specialized terpene metabolites as pheromones in intraspecific interactions. In contrast to plants and microbes, which employ enzymes called terpene synthases (TPSs) to synthesize terpene metabolites, limited information from few species is available about the enzymatic mechanisms underlying terpene pheromone biosynthesis in insects. Several stink bugs (Hemiptera: Pentatomidae), among them severe agricultural pests, release 15-carbon sesquiterpenes with a bisabolene skeleton as sex or aggregation pheromones. The harlequin bug, Murgantia histrionica, a specialist pest of crucifers, uses two stereoisomers of 10,11-epoxy-1-bisabolen-3-ol as a male-released aggregation pheromone called murgantiol. We show that MhTPS (MhIDS-1), an enzyme unrelated to plant and microbial TPSs but with similarity to trans-isoprenyl diphosphate synthases (IDS) of the core terpene biosynthetic pathway, catalyzes the formation of (1S,6S,7R)-1,10-bisaboladien-1-ol (sesquipiperitol) as a terpene intermediate in murgantiol biosynthesis. Sesquipiperitol, a so-far-unknown compound in animals, also occurs in plants, indicating convergent evolution in the biosynthesis of this sesquiterpene. RNAi-mediated knockdown of MhTPS mRNA confirmed the role of MhTPS in murgantiol biosynthesis. MhTPS expression is highly specific to tissues lining the cuticle of the abdominal sternites of mature males. Phylogenetic analysis suggests that MhTPS is derived from a trans-IDS progenitor and diverged from bona fide trans-IDS proteins including MhIDS-2, which functions as an (E,E)-farnesyl diphosphate (FPP) synthase. Structure-guided mutagenesis revealed several residues critical to MhTPS and MhFPPS activity. The emergence of an IDS-like protein with TPS activity in M. histrionica demonstrates that de novo terpene biosynthesis evolved in the Hemiptera in an adaptation for intraspecific communication.

Evaluation of Ten Alternative Treatments for the Management of Harlequin Bug (Murgantia histrionica) on Brassica Crops.

Harlequin bug (Murgantia histrionica) poses a significant threat to cruciferous vegetable crops, leading to economic losses and challenges in sustainable agriculture. This 2-year field study evaluated the efficacy of exclusion netting and selected biopesticides in controlling harlequin bug populations in a field-grown broccoli crop. Treatments included an untreated control, industry standards Azera and Entrust, and ProtekNet mesh netting. Additionally, three commercial essential oil treatments including Essentria IC-3, Nature-Cide, and Zero Tolerance were tested along with two bokashi fermented composting products BrewKashi and Oriental Herbal Nutrient (OHN). During both the first and second year of the study, none of the commercially produced essential oil products or bokashi products were effective in controlling harlequin bug or preventing leaf scars. Conversely, ProtekNet consistently provided the highest level of protection against harlequin bugs of all stages as well as leaf damage scars; it also provided the largest broccoli head width and highest yield. Entrust showed similar results compared to ProtekNet, both with the control of harlequin bug life stages and with leaf scars. These findings indicate that both ProtekNet and Entrust are effective organic alternatives for managing harlequin bug on broccoli, while the selected essential oil and bokashi products do not appear to be effective.

Low Tunnels Reduce Insect Populations, Insecticide Application, and Chewing Insect Damage on Brussels Sprouts.

Low tunnels covered with spun-bonded fabric (row covers) provide season extension for vegetable production and also afford a physical barrier against airborne insects and other non-soil pests. Brussels sprouts, Brassica oleracea L. group Gemmifera (Brassicaceae), is a popular vegetable in local markets in Virginia; however, unprotected field production is severely affected by insect pest infestation. This study's objective was to determine the level of protection low tunnels provide against insect infestation and leaf herbivory injury. The experiment was conducted at the Virginia Tech Eastern Shore Agricultural Research and Extension Center in Painter, Virginia. The experimental design was split-plot with polyethylene soil mulches (white or black) as whole plot factors and production systems (low tunnel or open field) as subplot factors. In this study, low tunnels reduced insect infestation and chewing herbivory leaf injury to Brussels sprouts. Compared to an unprotected open field, infestations of lepidopteran insects and harlequin bug, Murgantia histrionica (Hahn) (Hemiptera: Pentatomidae) were reduced on plants under low tunnels. However, aphids (Hemiptera: Aphidae) infestation occurred under low tunnels in fall. There was no effect of color mulches (white or black) and no interaction between tunnel and mulch color on insect infestation and chewing injury. Fewer insect infestations and feeding injury indicate that low tunnels can be an effective management tool for sustainable vegetable production.

Oncopeltus-like gene expression patterns in Murgantia histrionica, a new hemipteran model system, suggest ancient regulatory network divergence.

BACKGROUND: Much has been learned about basic biology from studies of insect model systems. The pre-eminent insect model system, Drosophila melanogaster, is a holometabolous insect with a derived mode of segment formation. While additional insect models have been pioneered in recent years, most of these fall within holometabolous lineages. In contrast, hemimetabolous insects have garnered less attention, although they include agricultural pests, vectors of human disease, and present numerous evolutionary novelties in form and function. The milkweed bug, Oncopeltus fasciatus (order: Hemiptera)-close outgroup to holometabolous insects-is an emerging model system. However, comparative studies within this order are limited as many phytophagous hemipterans are difficult to stably maintain in the lab due to their reliance on fresh plants, deposition of eggs within plant material, and long development time from embryo to adult. RESULTS: Here we present the harlequin bug, Murgantia histrionica, as a new hemipteran model species. Murgantia-a member of the stink bug family Pentatomidae which shares a common ancestor with Oncopeltus ~ 200 mya-is easy to rear in the lab, produces a large number of eggs, and is amenable to molecular genetic techniques. We use Murgantia to ask whether Pair-Rule Genes (PRGs) are deployed in ways similar to holometabolous insects or to Oncopeltus. Specifically, PRGs even-skipped, odd-skipped, paired and sloppy-paired are initially expressed in PR-stripes in Drosophila and a number of holometabolous insects but in segmental-stripes in Oncopeltus. We found that these genes are likewise expressed in segmental-stripes in Murgantia, while runt displays partial PR-character in both species. Also like Oncopeltus, E75A is expressed in a clear PR-pattern in blastoderm- and germband-stage Murgantia embryos, although it plays no role in segmentation in Drosophila. Thus, genes diagnostic of the split between holometabolous insects and Oncopeltus are expressed in an Oncopeltus-like fashion during Murgantia development. CONCLUSIONS: The similarity in gene expression between Murgantia and Oncopeltus suggests that Oncopeltus is not a sole outlier species in failing to utilize orthologs of Drosophila PRGs for PR-patterning. Rather, strategies deployed for PR-patterning, including the use of E75A in the PRG-network, are likely conserved within Hemiptera, and possibly more broadly among hemimetabolous insects.

Immature stages of Murgantia histrionica (Hemiptera: Pentatomidae).

Immature stages of Murgantia histrionica (Hemiptera: Pentatomidae) are described using light and scanning electron microscopy. Specimens of all life stages of M. histrionica were collected on Peritoma arborea (Cleomaceae) in Palm Springs, California. Specimens were observed in light and scanning microscopies, imagens taken and described based on specimens and photographs. We provide images of the eggs and immatures in light microscopy, and SEM of the eggs and first and fifth instars. Eggs of M. histrionica are barrel-shaped, white, with brown band and circular spot; the corium surface carinated, forming hexagonal cells; carinae irregular apically. The nymphal color pattern; the reflexed lateral margins of pro- and mesothorax; and the scattered punctuation of the tegument are a combination of characteristics enabling M. histrionica identification in its nymphal stages. The eggs of M. histrionica are similar in shape, color, and size to other Strachiini genera, such as Bagrada, Eurydema and Stenozygum. Among the Strachiini, the correct identification of M. histrionica based on immatures is possible by the shape of the head and pronotum, overall size of immatures, and coloration patterns.

Color Preference of Harlequin Bug (Heteroptera: Pentatomidae).

Harlequin bug, Murgantia histrionica (Hahn), is an important pest of Brassica crops in the southern United States. Regional populations are highly variable and unpredictable from farm-to-farm, and therefore accurate monitoring of activity would greatly improve IPM decision-making and the timing of control tactics. To our knowledge, there is no monitoring device or proven trapping system for this pest. We contribute new knowledge of harlequin bug visual ecology, which will aid in the development of an effective trap. In both lab and field color choice experiments, harlequin bug adults and large nymphs responded positively to green and black colors, and statistically less frequently to yellow, white, purple, or red with the exception of adult females, which were most attracted to red and green in the lab, but green and black in the field. We conclude that future trapping devices for harlequin bug should be green or black in color.

A Transcriptome Survey Spanning Life Stages and Sexes of the Harlequin Bug, Murgantia histrionica.

The harlequin bug, Murgantia histrionica (Hahn), is an agricultural pest in the continental United States, particularly in southern states. Reliable gene sequence data are especially useful to the development of species-specific, environmentally friendly molecular biopesticides and effective biolures for this insect. Here, mRNAs were sampled from whole insects at the 2nd and 4th nymphal instars, as well as sexed adults, and sequenced using Illumina RNA-Seq technology. A global assembly of these data identified 72,540 putative unique transcripts bearing high levels of similarity to transcripts identified in other taxa, with over 99% of conserved single-copy orthologs among insects being detected. Gene ontology and protein family analyses were conducted to explore the functional potential of the harlequin bug's gene repertoire, and phylogenetic analyses were conducted on gene families germane to xenobiotic detoxification, including glutathione S-transferases, carboxylesterases and cytochrome P450s. Genic content in harlequin bug was compared with that of the closely related invasive pest, the brown marmorated stink bug, Halyomorpha halys (Stål). Quantitative analyses of harlequin bug gene expression levels, experimentally validated using quantitative real-time PCR, identified genes differentially expressed between life stages and/or sexes.