Progress report for GNE24-316
Project Information
In agriculture, the mutualisms that ants and other predatory insects share with plants that produce extrafloral nectar (EFN) is understudied1. Extrafloral nectaries (EFNs) are structures that some plant groups produce that secrete nectar for the purpose of attracting omnivorous insects in exchange for protection from herbivores2. Ants are the most important insect group involved in this interaction, but other predatory insects visit EFNs and provide protection2,4. Conservation biocontrol is the concept of promoting habitat on farms that is attractive and hospitable to native beneficial insects, which provide essential services like pollination and pest removal. I aim to contribute to the knowledge of using EFN-producing plants as a means for conservation biocontrol in organic New England agroecosystems. Here, I outline a project designed around cucurbits using management practices common among organic farmers in Massachusetts. I used partridge pea, an EFN-producing wildflower, as a companion plant in cucumber plantings. During the summer of 2025, my colleagues and I collected insect community, plant damage, and harvest data throughout the growing season, and compared these data across blocks containing combinations of the above treatments (including a weedy fallow block). Preliminary results show that there was no significant effect of partridge pea presence in cucumber yield. Importantly there was no negative effect of partridge pea on cucumber yield, whereas our weedy fallow treatments had significantly lower cucumber yield than our mulched control plots. Sample processing and data analysis of insect communities from our traps is still ongoing, which will give us crucial information on how our companion plant treatments influenced populations of beneficial and pest insect populations in cucumber. Information gained from studies like mine will build on our understanding of the plant-protecting activities that abundant omnivorous insects like ants provide, which may be a useful tool for farmers dedicated to sustainably growing food. My outreach component consisted of two parts: 1) utilizing and dispersing informational materials provided by the Xerces Society while hosting informational booths at local farmers markets and 2) insect collection and education events with a summer youth program (Recreation Worcester) in various urban parks in Worcester, MA.
- Examine the effects of EFN-producing companion plants on insect communities associated with organic cucumber plantings in New England.
- Determine how EFN-producing companion plants influence the presence of pests, crop damage, and yield of cucumber plantings.
- Determine whether companion plants influence crops with and without their own EFNs differently.
The purpose of this project is to expand our current understanding on the utilization of plants that produce extrafloral nectaries (EFNs) as a tool for conservation biocontrol in organic vegetable systems. Extrafloral nectar evolved to reward omnivores like ants with sugars in exchange for defense against herbivory2,7. While ants are the primary mutualist, other beneficial predators known to feed on EFNs and reduce herbivory include parasitoids, beetles, lacewings, and even spiders2,4. Past studies have indicated the use of EFNs as a promising method of recruiting beneficial predatory insect abundance in agroecosystems, but their efficacy is highly dependent on a farm’s management practices, crops, and the surrounding ecosystem1. Therefore, I explored methods of using native EFN-bearing plants to harness the behavior of local ants and other predaceous omnivores to advance pest control for organic growers in New England.
Partridge pea (Chamaecrista fasciculata - hereafter PP) is an EFN-producing legume native to the Eastern US that is highly attractive to predatory and pollinating insects. The use of this plant in agroecosystems is understudied, but they have great potential for enhancing the beneficial arthropod community in an area8. Here, I focused on cucumber (a non-EFN cucurbit), which is popular among organic farmers in New England. I used PP as a companion plant treatment alongside cucumber and assess its effect on insect community dynamics and cucumber yield. The combination of plants in this system are good study candidates for this project. Cucumber is host to two major pests of economic concern to New England farmers: striped cucumber beetles (Acalymma vittatum) and spotted cucumber beetles (Diabrotica undecimpunctata howardi), which vector bacterial wilt that can cause up to 20% yield losses if left unmanaged by farmers9. Partridge pea intercrops may attract parasitoids and generalist predator insects (like ants) that could assist in controlling the populations of these beetles and their subsequent damage - which is what I aimed to assess.
There is an increasing societal demand for organic produce and less reliance on chemicals in food production10,11. In addition to consumer concerns, the use of broad-spectrum insecticides also harms non-target beneficial organisms like pollinators and predaceous arthropods12. Utilizing the prey-regulating ability of the predatory insects could help us mitigate crop damage, while reducing our reliance on these chemicals. Releasing lab-reared biocontrol organisms is common but is expensive and releasing species outside their native ranges can negatively non-target arthropods, especially endangered local species13,14. I would like to expand on this concept and learn more about the possibilities of enhancing local beneficial insect populations via the attraction of EFN-producing plants native to New England.
This proposal is part of my dissertation at Clark University, where I study the roles of ants in agroecosystems. The experiment outlined here is part of my third chapter, where I aim to run field experiments using cultivation methods common among organic farmers in Massachusetts. For the summer of 2024, I conducted my first set of trials for this chapter by utilizing PP as a companion plant alongside an EFN-producing cucurbit vegetable: zucchini. The purpose of this study was to determine if the inclusion of an EFN companion plant will attract and bolster the local ant/beneficial arthropod community and cause a spillover effect onto the EFNs of the crops themselves. Due to limitations in budget and labor, this study took place in a single plot at one site. The analyses from 2024 are in progress as I continue to process analyze data for this 2025 project. The experiments outlined in this proposal took place during the summer of 2025, and were not simply an extension of my 2024 dataset, rather they focused on a new crop, included a weedy fallow treatment, and took place in larger plots at two separate sites.
Our findings will provide cucurbit growers with new information on this understudied and potentially effective chemical-free alternative to pest control and enhance our current understanding of the mutualism between plants that produce EFNs and the organisms they reward in exchange for defense. To date, there has not been an extensive study on the employment of ants as biological control in cucurbits via intercropped EFN recruitment1. As our population expands, food security issues will become more common, especially in developing regions of the world where factors like climate change and poor soil quality are likely to hit the hardest15,16. Developing new conservation biocontrol practices will reduce the need for costly pesticides and horticultural practices that create high barriers of entry that may dissuade people from underrepresented groups from starting their own farms. Any work that supports local farmers improves the surrounding community, helps eliminate food deserts in poor areas, and is a step toward phasing out our reliance on large food distribution corporations that we currently rely heavily on for produce.
Cooperators
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Research
Study area
This field experiment took place in Massachusetts on two sites. I utilized 0.20 acres at both sites for this study (Fig. 1), which allowed for ample space between treatment blocks and a mowed perimeter. For the summer 2024 season, I worked with a land manager in Spencer, MA (Ronald Audette in the cooperators listed here) and I continued to utilize this space in 2025, which they are allowing me to use for free. A board member of the Grafton Land Trust (Paul Grady in our cooperator section) allowed me to use part of their pasture that they manage for the same purposes. Farms in Central MA share common pests and beneficial species, yet each farm has slight variations in their insect community composition and management strategy (personal observations 2022-2025).
Cucumber is the focal crop of this study. I constructed 24 equally-sized blocks at each site acting as individual replicates (Fig. 2). Each block was 3 x 5m, allowing for multiple rows of crops and companion plants with space for 3m mowed buffer areas between blocks to reduce the interactions among blocks of different treatments. One block consisted of one 5m long central crop row and an equal-length treatment zone on one side (Fig. 3). In a randomized block design, these blocks received one of three possible planting treatments, with four replicates of each treatment x crop combination: 1) control treatment only surrounded by weedy fallow, 2) bare mulched ground, 3) cucumber with PP (Fig. 4). For all analyses, the sample size equals the number of experimental units being sampled (48). I treated all rows with the same watering regimes. The experiment will end three weeks after peak cucumber harvest.
Treatment justifications
Cucumber was chosen as the focal crop because it is an economically important vegetable for organic farmers in our area. The weedy fallow control treatment is necessary in order to use as a reference point for unmanaged habitat that acts as refuge for local arthropods, and compare to a planting intentionally selected for its properties as an insectary crop17,18. The bare ground treatment allows me to compare our treatments to conventional cucurbit production (e.g., weedless). Partridge pea was chosen as the companion plant treatment due to its great potential as an understudied attractor of beneficial arthropods8. Additionally, PP is a legume which can be utilized for soil nitrogen fixation, and its flowers are highly attractive to native pollinators (personal observations 2022-2024) which may prove an additional benefit of increased fruit set for cucumber.
Objective 1
I aim to determine the effectiveness of EFNs as attractors of ants (Fig. 5), other predators, as well as pollinators (Fig. 6). I addressed this objective by collecting herbivore and ants/beneficial arthropods to determine their density and diversity among treatments. Insect presence (both pests and predators) on cucumber plants during morning observations was minuscule this year, so I instead decided to focus on traps for estimating insect populations rather than in-person observations and vacuum sampling. Insects were collected throughout the growing season using various methods to obtain a representative sample of the insect community from each block. These methods included pitfall traps, sticky cards, and baited traps (tuna/honey). Additionally, we we able to include bee bowls (multicolored bowls with soapy water to attract and capture various pollinators) as a trap type (Fig. 7). Collecting and preserving insect specimens this way is beneficial as I can identify individuals much further down taxonomically than with visual observations. I recorded environmental variables known to influence insect communities during each sampling date, including: soil temperature, soil moisture, soil pH, soil compaction, air temperature, air humidity, overhead canopy cover, precipitation, and plant volume. These environmental factors are necessary to record because each may vary by block and site, and accounting for them in analyses is crucial.
I will then use data generated from these traps to calculate ant, generalist predatory beetle, parasitoid, and pollinator richness and abundance. I will use linear mixed models to examine how these measures of diversity are impacted by treatment groups and environmental variables. I will use Non-metric Multi-Dimensional Scaling (NMDS) analysis to compare insect community composition between treatments, sites, and based on environmental differences.
I predicted that PP will increase abundances of generalist omnivores like ants and beetles on focal crops, as well as parasitoid wasps/flies whose adults feed on EFNs, and that crop damage will be lowest and yield highest in this treatment8. I also predicted that weedy fallow treatments will provide plant structure and serve as a refuge for predatory insects, but will not be as attractive as the PP blocks - and therefore this treatment will have lower beneficial insect diversity than the PP treatment.
Predictions regarding aphids
Ants are known to tend aphids in exchange for honeydew, which increases aphid numbers on plants. However, I do not predict that enhancing ant populations via EFN companion plants will be an issue regarding aphids in my study system. Aphids, while present on cucumber and zucchini, are not the main cucurbit pest of concern in New England. Acalymma vittatum is the most damaging pest of cucurbits growing in our region19, and I have witnessed the effects of this pest firsthand when conducting my first two seasons of samples across organic farms in Massachusetts. Net economic impacts of ant-aphid mutualisms are highly context dependent, but studies in other systems have shown positive effects of honeydew-farming ants that drive away other arthropod pest groups from plants harboring aphid colonies20. Lastly, EFNs and flowers of my companion plants are highly attractive to local wasps that parasitize aphids, as well as voracious aphid-eaters like hoverflies, ladybeetles, and lacewings5,8.
Objective 2
I plan to determine if EFN-bearing companion plant presence results in less crop herbivory and higher yield compared to controls. Here I will compare crop yield and leaf damage/disease among the treatments described above. I quantified leaf damage by scoring a subsection of each plants’ leaves by level of damage, as well as noted if different diseases may be present in each plant based on leaf symptoms23. The inclusion of these categories is important, as different types of damage indicate different pests/disease. Schifani et al., 2020 also suggested that the presence of ants on experimental pear trees lowered necrotic damage caused by a fungus, via antimicrobial secretions from visiting ants. Therefore, recording the percentage of plants infected with disease will provide useful information. Lastly, I will use yield data to conduct a cost-benefit analysis to determine if the materials required to install/maintain these companion plantings are worth it to a farmer.
Currently, leaf damage and yield analyses have been completed. I calculated yield by obtaining total crop mass at the end of the season and will consist of two measurements: 1) total crop harvest biomass, and 2) marketable yield (total biomass minus unmarketable fruit). I obtained biomass by weighing produce as it was harvested. I then used linear mixed models using leaf damage scores and yield as response variables, block treatment as a fixed effect, and include sample date, environmental factors and site as random effects to analyze the data. For the cost-benefit analysis, I will subtract the labor ($/hour of work setting up and maintaining treatment zones) and materials (e.g., seeds, mulch) utilized to maintain each treatment from the total yield at the end of the season. I will then use a single-factor Anova to compare differences in yield (response variable) across treatments.
I hypothesized that the recruitment of predators to EFN companion plants will influence the marketable crop yield and tissue damage in a system. I predicted that when compared to control blocks, there will be an increase in marketable crop yield and lower host plant tissue damage from herbivores when PP are present. This is because PP will likely attract higher numbers of generalist predators (like ants) that I hypothesized are important in removing the most damaging pests in cucurbits (e.g., A. vittatum, D. howardi)21,22.For the cost-benefit analysis, I predicted that the yield gains from PP will outweigh the overall cost of materials (e.g., seeds) and labor to include these plantings when compared to the management that goes into maintaining control blocks.
Objective 3
For my last objective I plan to determine if the presence of EFNs on the crops themselves has an impact on the insect communities that are associated with each and whether there is a synergistic effect of EFN-bearing companion plants on these two crop types. I will accomplish this by comparing the insect communities across crop types sampled between the 2024 (zucchini) and 2025 (cucumber) seasons and their respective treatments and sites. The collection methods and data used to address this objective are the same as the above Objective 1.
Using linear mixed models, I will examine how insect diversity, abundance, richness, and evenness are influenced by environmental conditions and how they vary across pairwise interactions of crop type and treatment. We will use Non-metric Multi-Dimensional Scaling (NMDS) analysis to compare insect community composition between companion plantings, crops, sites, while accounting for environmental factors.
I hypothesize that insect communities will vary between zucchini and cucumber, and among combinations of their companion plant treatments. I predict that carbohydrate-seeking predatory arthropods that utilize EFNs (e.g., ants, beetles) will be more apt to spill over to and forage on zucchini versus cucumber. The presence of EFN on zucchini will cause those arthropods to spend more time on this crop versus its non-EFN counterpart (i.e., cucumber). For zucchini specifically, I predict that more ants will forage on this crop’s EFNs (and therefore more will be collected from these plants) in “PP only” versus other treatments, as this treatment will attract and host the most ants.
Sharing of data and results
I will publish the results from this study in relevant scientific journals as part of my dissertation, as well as present to (e.g., local NOFA symposiums) and share with (e.g., data reports) farmers, landowners, and groups involved in the outreach presented in this proposal.
Current status
As of this progress report submission in January 2026, the following data has been processed and analyzed: cucumber yield. Leaf damage and disease datasets have been organized but not yet analyzed. Ants from all traps (honey, tuna, and pitfalls) have been identified to species, and I am currently working on transcribing that data to prepare for analysis in Rstudio. Once ant community data analysis is complete, I will begin working on processing sticky card data to estimate differences in the community pests (e.g., aphid, cucumber beetle, squash bug) and parasitoids. Additionally, generalist predatory beetles in pitfalls and pollinators collected in bee bowls are in the process of identification and quantification this semester. As stated above, there were a very small amount of insects patrolling/feeding on our cucumber during observations this year, therefore I decided to drop this method from the daily sampling routine mid-summer. Instead, I chose to rely on our traps to provide estimates of pests within each block. During leaf damage and disease measurements, I recorded the presence and absence of wingless aphids on the underside of each leaf, and include it as a factor in subsequent analyses.
Yield
Marketable yield was significantly higher in control plots than weedy fallow, with partridge pea plots being a non-significant intermediate (LME, p = 0.012) (Fig. 8). There were no significant differences in unmarketable yield between the three cucumber treatments (LME, P < 0.05) (Fig. 9).
Conclusions
From the preliminary harvest and leaf damage results, partridge pea did not have a significant influence on yield or leaf damage in cucumber. However, the presence of partridge pea had no detrimental effects on our cucumber harvest compared to controls, unlike weedy fallow. This implies that the inclusion of partridge pea as a companion plant may be a viable option for a farmer to increase native pollinator services and nitrogen availability (as partridge pea is a legume) while growing cucurbits. As stated in the results section, I am currently in the process of processing and analyzing the insect community data and cost benefit analyses from 2025. Once those objectives are completed, I will be able to make more accurate conclusions about the impacts of partridge pea as a companion plant (i.e., pollinator, predator and pest numbers) in cucurbits.
Education & outreach activities and participation summary
Participation summary:
I conducted two outreach activities throught the summer of 2025: 1) informational booths at local farmer's markets and 2) insect collection and identification workshops at local parks with K-12 students.
Farmer's markets
I reached out to a representative of the Xerces Society and was able to get pamphlets (see attached pamphlet PDFs) sent to us that were tailored toward beneficial insect conservation in the Northeast US. We then set up an informational table (Fig. 10) at four separate farmer's market dates, 3 in Worcester and one in Grafton, MA. At these events, Me and the undergraduate students in our lab educated visitors on what we do at Clark, talked about the importance of insect diversity in agriculture, and described the science behind the project that I outlined in this grant. The pamphlets we handed out described how hobbyists and professional farmers can manage the landscape around their plantings by choosing companion plants that complement their specific crops, as well as how to identify native beneficial insects. The in-person activities I have described here will also benefit the undergraduate students working for us during the summer, as they will encourage them to participate and build on their skills in public outreach as young scientists. Additionally, I will share yield and insect diversity results with local farmers as I gather and analyze our data. I will present the summaries of our results at one of the local symposia held by the Northeast Organic Farming Association (NOFA), as well as publish findings in one of their newsletters free to the public.
- 22-014_01_Soil-Bioindicators-Guide_web-screen
- 08-005_02_XercesSoc_Farming-for-Pest-Management-brochure_web
- 12-020_03_BumbleBeeConservation_web-print
- 08-006_01_XercesSoc_Farming-for-Pollinators-brochure
- 18-014_02_Natural-Nesting-Overwintering-FS_web
- 15-031_04_HAG_FarmsAgLandscapes_web 22-026_01_NPPBI—Northeast_web
- 16-044_02_MNPL_Northeast_web-print
K-12 student outreach
I worked alongside leaders at Recreation Worcester, a free youth summer program run by our city, to design a curriculum aimed at teaching kids about the importance of native insects and identify the major groups of arthropods they may find while playing outdoors. I created a booklet going over these insect groups, which we printed and handed out to the kids (see attached "Bugs in your backyard" PDF). These events took place at 3 public parks, ranging from ~20-30 kids and a handful of chaperones participating at each. For the activities, we spent ~2-3 hours at each park collecting insects from trees and vegetation with sweep nets, placing them in collection vials, and then passing them around to the kids while educating them about their ecological importance and what interactions they may have with humans.
Project Outcomes
Our preliminary results show partridge pea did not negatively impact cucumber yield when growing alongside them. These results are promising, in that we provide evidence that partridge pea may be a viable companion plant in organic cucurbit systems. However, analyses on the influences that partridge pea may have on the populations of beneficial (predators and pollinators) and detrimental (pests) invertebrates in cucumber plantings have yet to be conducted. Insect community data will inform us the degree to which partridge pea acts as an insectary plant in agricultural systems like this, which farmers may be able to use in making decisions for managing their landscape. Once all analyses are completed, the subsequent reporting of results and main outcomes to the public will be conducted.
Learning reflections
I have yet to conduct the majority of analyses from this project. From what I have completed currently, I have learned that partridge pea produces a high quantity of extrafloral nectar throughout the growing season, which is very attractive to ant workers. Additionally, the flowers of partridge pea seem to be a good resource for attracting native bees During our sampling days our partridge peas had very high bee activity, with dozens of bumblebees, solitary bees, and predatory wasps foraging in each PP-treated block at any given time. Knowing that partridge pea does not significantly reduce cucumber yield like the weedy fallow treatment did, it seems like this plant would be a useful addition for farmers looking to enhance the ecosystem services provided by arthropods from the surrounding landscape in their farm.
In general, I learned a great deal about sustainable agriculture while working on this project. From two summers of tilling, hoeing, mulching, planting, irrigation/repairing drip tape, adding/removing row covers, staying on top of weeding, mowing between rows, and harvesting - I have gained much respect for the farmers that throw aside the conveniences of industrial agriculture. I also learned how much organic farmers care about the health of the land that they manage, and how important it is for them to stay on top of modern research and methods for growing food in a manner that is safe for the surrounding landscape. Thus, the results gained from this study will greatly benefit such farmers looking for novel methods in sustainable food production.
Future research/career directions
For future directions I plan to look into the specific interactions among organisms that take place in these cropping systems. Other components of my dissertation focus on 1) the relationships and fitness impacts between nectar microbes, plants, and ants in agroecosystems, and 2) how ant cuticular hydrocarbons (i.e., the scent trails they leave behind while foraging) influence the behavior of herbivorous insects. In terms of my career, I am interested in continuing in academia and plan to pursue a postdoc position at a university studying plant-insect-microbe interactions.
Assessment of study and outreach
My study was the product of multiple years of planning, and I feel that its design is very sound. This work could not have been completed without the help of the undergraduate students this summer - which were compensated using the funds from this SARE grant. As a PhD student, I do not make much, especially since we do not get paid during the summer when not teaching. This grant supported me and allowed me to put all of my effort into the work I conducted this summer. However, the limits of a 5-6 year dissertation mean that the number of seasons that such a study can be conducted are limited. From the knowledge and experience from other agricultural researchers, I know that the the effects and applicability of results to real-world scenarios of an agroecological study system is highly dependent on location, resources, and time.
Time is an incredibly important factor that influences the effectiveness of something like a cultural/conservation biocontrol method or companion planting treatment, as it may take multiple seasons of the same planting regime to build up beneficial invertebrate communities in the soil and surrounding environment. Insects can also be highly variable from farm to farm in a given geographic region, especially between organic farms whose managers have their own areas of expertise and preferred pest control practices. Therefore, being able to include more sites in this study would have also been useful.
Further study
While out of the scope of my own dissertation, it would be interesting to see what influences partridge pea may have on the community of soil microbes and soil nutritional quality - since they form mutualisms with nitrogen fixing bacteria. Partridge pea are a native legume, and may be more suited to acquiring soil mutualists in their native range of the northeast compared to other non-native legumes grown here like peas and beans. Moreover, these mutualisms may change the chemistry of the soil surrounding the crops that they are planted next to. Future work should study the influences that such alterations may have on the health and quality of the focal crop being produced.