Influences of habitat-level crop diversity on community dynamics of pentatomids and their parasitoids in New Jersey

Progress report for GNE22-306

Project Type: Graduate Student
Funds awarded in 2022: $15,000.00
Projected End Date: 05/31/2025
Grant Recipient: Rutgers University
Region: Northeast
State: New Jersey
Graduate Student:
Faculty Advisor:
Anne Nielsen
Rutgers University
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Project Information

Project Objectives:

I conducted a small pilot study in 2022 and a larger-scale, comprehensive field study that began in 2023. Here are the objectives for the larger field study:

  1. Determine how landscape variables—such as the percent of forest, corn, soybean, orchard, etc. in a 3-km radius, edge density, and landscape evenness—predict abundances of two stink bug species—the invasive brown marmorated stink bug (BMSB) and the native beneficial spined soldier bug (SSB)—on New Jersey peach orchards.
  2. Determine how landscape variables—such as the percent of forest, corn, soybean, orchard, etc. in a 3-km radius, edge density, and landscape evenness—predict egg mortality of stink bug eggs due to parasitoid wasps and arthropod predators.
  3. Identify to species all parasitoid wasps that successfully (hatched out) and unsuccessfully (unemerged) parasitized deployed BMSB and SSB eggs using DNA barcoding and available parasitoid sequence libraries. Then, compare species richness and evenness of parasitoid assemblages that parasitized BMSB and SSB eggs.
  4. Monitor spread and establishment of Trissolcus japonicus, a non-native parasitoid wasp that has co-evolved with BMSB in their native range of Asia, on NJ peach orchards via deployment of BMSB and SSB eggs.

The purpose of this project is to understand how landscape impacts the abundance of pentatomids—or stink bugs—and enemy-associated egg mortality of their eggs by parasitoid wasps and arthropod predators. This project is applicable to sustainable agriculture because it will inform management strategies to increase ecological pest control of Halyomorpha halys, the brown marmorated stink bug (BMSB). BMSB is an invasive insect from Southeast Asia that was first detected in Pennsylvania in the 1990s. It is a major agricultural pest of fruit, vegetable, and row crops, including peach and soybean, and causes agricultural and nuisance problems in 9 of the 13 states and territory incorporated in Northeast SARE.

In addition to BMSB, we also studied Podisus maculiventris, the spined soldier bug (SSB), which is a native arthropod predator which preys on a number of pests, including corn ear worm, tobacco hornworm, and even early instars of BMSB. We investigated how BMSB and SSB vary in seasonal abundances and responses to different landscape patterns by trapping both insects using both passive (pheromone-baited traps) and active (sweep-netting and visual surveys) monitoring techniques.

We will monitor pentatomid population levels while simultaneously monitoring their egg-parasitoids with sentinel egg masses laid by lab-maintained colonies. We will retrieve sentinels from the field and monitor for successful (adult parasitoid emerges from egg) and unsuccessful (partially developed parasitoid in egg) parasitism, as both result in the death of the host. We will identify parasitoid species with identification keys and molecular forensics. Additionally, we will note evidence of egg predation in sentinel egg masses, although it will not be possible to ascertain which predator species is responsible for damage, so our analyses will focus primarily on parasitoids.

Using ArcGIS spatial analysis, I will uncover which habitats are positively correlated with high egg mortality of BMSB. I suspect a high proportion of natural land, orchards, and mixed annual crops around orchards will result in higher biological control of BMSB in the form of egg mortality, while proportion of urban, corn, and soybean habitats will negatively contribute to egg mortality. These results would suggest that crop diversification and preservation of natural land contribute positively to pest control.


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Materials and methods:

2022 Pilot Field Study

I collected data over two weeks in August 2022 from two peach, two soybean, and two forested habitats in southern New Jersey (Fig 1). There, I trapped for BMSB, SSB, and brown stink bug (BSB), Euschistus servus, a native pest using pheromone baited traps. I also deployed colony-laid egg masses of these three stink bugs. I collected these egg masses after 3 days in the field.

Map of study sites for 2022 pilot study.

Figure 1. Map of study sites for 2022 field study.

Egg masses were then placed in tight-fitting petri dishes and placed in 25°C incubators. Stink bug nymphs and parasitoids emerged and died in the dishes, and after 6 weeks, the petri dishes were frozen at -20 for later egg dissection and egg fate determination (Figure 2).

An egg mass with parasitoid wasps that have hatched

Figure 2. Trissolcus japonicus wasps that have hatched from a BMSB egg mass.

Egg fates included stink bug nymph emergence, parasitoid emergence, predation (chewing or sucking), unemerged parasitiod, unemerged nymph, and unemerged unknown. These fates were further classified into egg mortality due to natural enemies (parasitized/predated) and other. I compared egg fate by habitat and species using binomial GLMMs.

2023-2024 Landscape Study

I collected data over 10 weeks from June-August 2023 at 15 different peach orchards in central and northern New Jersey. I narrowed my research to two stink bugs, BMSB and SSB. I monitored stink bug abundances at orchards using pheromone-baited traps, visual sampling, and sweep-netting. Eggs of the two stink bug species were prepared and deployed following the same methods as in the 2022 field study (Figure 3).

Deploying an egg mass in a peach orchard

Figure 3. Deloying an egg mass in the field.

Egg masses were handled in the same manner and egg fates were categorized using the same categories as in the 2022 pilot study. Remaining unemerged eggs that are marked “unknown” may have resulted from unsuccessful parasitism. I am in the process of separating each unemerged egg, extracting DNA from these samples, sequencing the DNA, and using barcoding to identify when unsuccessful parasitism took place. This will be a long endeavor, as I have hundreds of eggs to separate and perform molecular analyses on.

Additionally, we are in the process of analyzing the landscape data. I ground-truthed all agricultural land in a 3km radius of my 15 field sites during August and September 2023. Now, I am training an AI image classifier in ArcGIS Pro to recognize crop type from satellite imagery so I can calculate percentages of different habitat types in the surrounding landscape of my study sites (Figure 4).

Work in ArcGIS Pro

Figure 4. Training the Image Classifier Tool in ArcGIS Pro.

Research results and discussion:

2022 Pilot filed study

Egg mortality due to parasitoids and predators was highest in soybean for all three species of stink bug (Fig 2). Parasitism and predation was highest for SSB and lowest for BMSB, which is unfortunate given the role that these two insects play in agricultural production. However, it must be noted that the sample size for the egg masses of each host species in each habitat was quite small (3-6), as this was a pilot study.

Egg mortality from natural enemies (EMNE) of stink bugs in different habitats

Fig 2. Percent of egg masses with egg mortality due to parasitism or egg predation across species and habitats. =

Stink bug-parasitoid trophbic linkages

Fig 3. Parasitoid species associated with eggs of the three different stink bugs. Thickness of line shows strength of association. Dotted line indicates that only non-successful parasitism was observed with a particular parasitoid-stink bug pairing.


2023-2024 Landscape Study

I am in the process of going through the over 500 egg masses that I deployed during the summer of 2023. At each of my 15 peach orchard sites, I deployed between 14-15 BMSB and 19-21 SSB egg masses. I do not yet have results from this project to report.

Participation Summary
18 Farmers participating in research

Education & Outreach Activities and Participation Summary

2 Workshop field days

Participation Summary:

Education/outreach description:

Results from my 2022 pilot study was shared with research scientists at the Entomological Society of American Eastern Branch conference in March 2023. My talk was titled ‘Trophic interactions of native and invasive stink bug and their parasitoids depend on habitat context.’ Additionally, I shared these results and my 2023 fieldwork plans at an Ecology & Evolution Graduate Program student seminar in April 2023.

Emma Waltman presenting at 2023 Entomology Society of America Eastern Branch

I plan to share eventual results of the 2023 with growers electronically as a blog post on Rutgers Plant & Pest Advisory Bulletin. Additionally, results of this project will be published in a peer-reviewed research article that I aim to submit fall 2024.

I have planned an outreach project, as well. I am in the early stages of designing an educational poster and brochure about integrated pest management and conservation biological control. I will ask the participating growers of my study to hang the poster in their farm store, and I will distribute the brochures at farmers markets to consumers and to patrons of pick-your-own operations in summer 2024.

Project Outcomes

4 Farmers reporting change in knowledge, attitudes, skills and/or awareness
2 Grants applied for that built upon this project
2 Grants received that built upon this project
$4,500.00 Dollar amount of grants received that built upon this project
Any opinions, findings, conclusions, or recommendations expressed in this publication are those of the author(s) and do not necessarily reflect the view of the U.S. Department of Agriculture or SARE.