Cover Crops for Enhancing Cherry Orchard Habitat for Beneficial Invertebrates

Progress report for GW21-225

Project Type: Graduate Student
Funds awarded in 2021: $30,000.00
Projected End Date: 12/31/2023
Host Institution Award ID: G225-22-W815
Grant Recipient: Oregon State University
Region: Western
State: Oregon
Graduate Student:
Major Professor:
Dr. Sandy DeBano
Oregon State University
Major Professor:
Dr. Christopher Adams
Oregon State University Mid-Columbia Agricultural Research and E
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Project Information

Summary:

The Mid-Columbia Basin is the dominant cherry production region in Oregon, producing approximately 80% of the state’s cherries. When new orchards are planted, the ground under young trees is typically left bare. However, planting cover crops in new orchards may provide habitat for diverse beneficial invertebrates (hereafter “beneficials”), some of which play key roles in pest control. When cover crops are planted, producers must decide on a seed blend to use, despite scarce information on how different blends influence beneficials. Adjacent natural lands also likely harbor beneficials, which can provide additional pest-control services to nearby orchards.

This study is examining how communities of beneficials are influenced by different cover crop blends, both in fallow orchard habitats (no trees - just cover cropped), newly planted orchards and adjacent natural habitats. We are currently sampling beneficial and pest invertebrates in three broad habitat types associated with orchards including: 1) new orchards - ranging from no cover crop to grass-dominate cover, to mixed forb/grass cover, 2) mature orchards, and 3) natural habitat fragments.

Once we finish fieldwork, labwork, and data analyses, our results from the project will be shared with producers via two extension publications and presentations at farm fairs in Hood River and Hermiston in the summer of 2023. We will convey results with the scientific community at conferences and in peer-reviewed publications. Finally, results will be shared with the public in a series of educational videos to be released on YouTube. This project addresses several “critical needs” identified by a 2018 working group on sweet cherry production in Washington and Oregon. Several members of the working group have indicated support for this project (see letters of support).

Project Objectives:

Research Objectives:

  1. Inventory non-pollinator beneficial invertebrates in orchards and natural habitats in the Mid-Columbia Basin and examine habitat characteristics associated with their distribution and community composition.
  2. Determine the ability of different cover-cropping regimes (no cover crop vs. grass dominant cover crops vs. a grass and forb mixed cover crops) to enhance beneficial invertebrate communities.
  3. Investigate the ability of different cover-cropping regimes to reduce the abundance of three common pest taxa (spotted wing drosophila (SWD), aphids, and leafhoppers).

Education and Outreach Objectives:

  1. Share research results about beneficial invertebrates, the value of adjacent natural habitat fragments, and project outcomes related to the use of cover crops in cherry orchards with fruit producers in the Columbia Basin.
  2. Present project results to the scientific community via conference presentations and publications in the primary literature.
  3. Create targeted educational content related to beneficial invertebrates designed to connect urban audiences to sustainable agricultural research and practices.
Timeline:

Prior to grant awarding, we will conduct initial site surveys and collect preliminary data (summer 2021). After preliminary data collection, invertebrate samples collected during 2021 will be sorted and organized to the lowest taxonomic level possible from September 2021 until the official start date of the grant on January 1, 2022. Preliminary data collection will help us refine our methods, identify any potential hiccups, and ensure that full data collection goes smoothly once grant funds have been awarded.

We plan on beginning the project in January of 2022 and are requesting a start date of January 1, 2022. Once grant funds have been awarded, we will begin purchasing materials for field collections set to happen in the spring and summer of 2022. Once supplies have been purchased, we will spend January and February preparing the multi-component, plant volatile lures, SWD sphere traps, other field equipment and ironing out fieldwork plans. Field collections will occur from the April 2022 until August of 2022. Following field collection, all invertebrate specimens will be pinned, sorted, and identified to the lowest taxonomic level possible. We will begin with identification of specimens from the cover-cropping trials (15 sites) and anticipate finishing with these specimens by November 2022. Finishing all invertebrate identification will likely take until December 2022.

Following data collection, we will begin analyses and manuscript preparation. Preliminary data analyses on Research Objectives #2 and 3 will be completed by January so results can be presented at the Annual Orchard Pest and Disease Management Conference in Portland, Oregon held during the week of January 9th, 2023. After this conference, efforts will switch to remaining data analyses and manuscript preparation.

Most extension and education efforts will be conducted during the summer and fall of 2023. Extension events with producers in the Mid-Columbia Basin will be held following cherry harvest in August 2023. We plan on delaying presentation until after harvest so as to present results at a time that is more convenient to producers who are likely too busy during harvest to attend such events. In early August of 2023, results from Research Objective #1 will be presented at the Ecological Society of America conference. The final extension event that we will conducted related to this project will be at the Annual Hermiston Farm Fair in late November 2023. We plan on submitting both planned manuscripts for publication between October and December of 2023.

For a more detailed, graphical timeline, see the Figure 4.

Figure 4: Project timeline. Gantt chart displaying major project check points beginning with preliminary work planned for the summer of 2021 and ending with the end of the grant in 2023. Solid black bars represent continuous or ongoing work. In places where bars are broken, work will be conducted periodically as indicated in the chart.  Blue is preliminary work, orange is research objectives, green is education and outreach objectives and yellow is major grant deadlines.

 

Cooperators

Click linked name(s) to expand/collapse or show everyone's info
  • Dr. Andony Melathopoulos
  • Mike Omeg - Producer
  • Dave Meyers

Research

Materials and methods:

Overview

We are addressing the following objectives with our research:

  1. Inventory non-pollinator beneficial invertebrates in orchards and natural habitats in the Mid-Columbia Basin and examine habitat characteristics associated with their distribution and community composition.
  2. Determine the ability of different cover-cropping regimes (no cover crop vs. grass dominant cover crops vs. a grass and forb mixed cover crops) to enhance beneficial invertebrate communities.
  3. Investigate the ability of different cover-cropping regimes to reduce the abundance of three common pest taxa (SWD, aphids, leafhoppers).

This study is being conducted in cherry orchards owned and operated by Orchard View Farms Inc., orchards owned and operated by High Rolls Ranch.  and in adjoining natural, oak-scrub habitat. Mike Omeg (producer on project team) is the Director of Business Operations at Orchard View Farms Inc. We are also cooperating with Dave Meyers (owner and operator of High Rolls Ranch) to conduct some sampling on several of his properties.  We are sampling beneficial invertebrates (predators and parasitoids) and pests (SWD, aphids, and leafhoppers) in three main habitats associated with cherry orchards (Figure 1). The three habitat types are: 1) mature orchard; 2) new orchards; 3) natural habitat. We identified and established 5 sites that are "mature orchards" that are in active production, 15 sites that are "new orchards" that contain young - not yet productive trees or no trees, and 5 sites that are "natural habitat" that are adjacent to orchards. The 15 "new orchard" sites range considerably in the type of cover crop mixes used include sites that were not planted (bare ground), sites planted with grass dominated cover crops, and sites planted with grass/forb blends of cover crops. The specific cover crop mixtures used in each site ranges in the proportion of forb seed included in the seed mix. A map of all sites established in 2022 can be seen below in Figure 2. Several sites that were originally located in 2021 had to be moved. The updated locations are included in the map below. 

Updated Figure Sampling Schematic
Sampling schematic for sites used in cherry orchard sampling.

Figure 1. Treatment types and general sampling schematic for sampling beneficial invertebrate communities in cherry orchards and adjacent natural habitats. This figure is updated from our original proposed sampling schematic. For a updated, detailed, site specific sampling schematic, see Figure 3 below.

Figure 2: Map of sampling sites.
Figure 2: Map of all sampling sites used in 2022 sampling.
Detailed site sampling schematic.
Figure 3: This image shows a site specific sampling schematic. We altered our sampling scheme from the originally proposed schematic based on preliminary findings in 2021 fieldwork.

Objective 1: Inventory non-pollinator beneficial invertebrates in orchards and natural habitats in the Mid-Columbia Basin and examine habitat characteristics associated with their distribution and community composition.

Field Methods

To address Objective 1, in 2021, we conducted preliminary sampling and located 20 of our 25 sample sites. In April 2022, we set up all of our 25 sampling sites including scouting and evaluating the 5 remaining sites that were not used in 2021. Several sites were moved from 2021 locations to accommodate on the ground changes with our sites. We have been monitoring each of these sites monthly since April for beneficial invertebrates. Our original sampling plan included bi-monthly sampling however, sampling periods have each taken well over 200 person hours (typically 2 people working) to complete, thus we reduced sampling to monthly sampling. Based on preliminary data collected in the summer of 2021, we know that this will of sufficient sampling intensity to answer our research questions and complete the objectives outlined above. Sampling bimonthly would not be possible based on the amount of time each sampling period takes. Cumulatively we have conducted approximately 800 person-hours of fieldwork in 2022 for the project and have one more sample period left to complete in August. In between field collections, we have also started processing invertebrate samples in the lab.

During April, May, June, and July of 2022, we collected beneficial invertebrates using four methods. Pitfall traps were used to capture and catalog terrestrial beneficial invertebrates (e.g., ground beetles, spiders). Aerial beneficial invertebrates (e.g., Hymenoptera, lacewings, parasitoid flies) were collected using delta traps baited with plant-volatile compounds known to attract a wide range of beneficial invertebrates (Jones et al., 2016; DuPont and Strohm, 2020), yellow sticky cards positioned just inside (or above) the groundcover layer, and pan traps (yellow, blue, and white fluorescent painted cups filled with water, designed to mimic flowers and attract flower visiting invertebrates). Five baited delta traps, 12 pitfall traps, ten yellow sticky cards, and 15 (5 each of blue, yellow and white) were used during each sampling period in each site (Figure 3). During sampling periods, traps were left open for three days (72 hours) at a time. Longer duration trapping was not feasible due to trap saturation (sticky traps) and rapid evaporation of liquid from pitfall and pan traps. Upon collection, we have stored samples in the lab and have started to sort and pin specimens. Once specimens are sorted and pinned, beneficial invertebrates will be identified to the lowest taxonomic level possible using published dichotomous keys.

Data on environmental and plant community characteristics was also collected at each site.  Environmental variables that have been collected include incident solar radiation at each site (measured using a Solar PathFinder tool), canopy density (measured using a densiometer). Other environmental variables including slope aspect/angle, elevation, distance to nearest natural habitat, and size of habitat fragment will be determined later using GIS software. During April - July, we have sampled plant communities using quadrats, once per month at 17 uniformly spaced points/site (Figure 4). Within each quadrat, the number of blooming stems on each blooming plant species was counted and recorded and woody plant and herbaceous plant height was measured. Photos have been taken of each quadrat for each month (1,700 photos so far) and will be used to assess ground cover composition at a later date. We have also counted all of the trees over 5cm in diameter (by species) inside of a 50 m x 50 m sampling grid. 

Figure 4: Plant Quadrat Examples
Figure 4: Plant quadrats were used to assess plant community composition and plant heights at 17 evenly spaced points in each site.

Statistical Analyses

Beneficial invertebrate communities will be described in terms of abundance and taxa richness, diversity, and community composition. A list of beneficial invertebrate taxa will be generated for each habitat type. Community patterns will be analyzed by sampling period across the season to understand what kinds of beneficials may be expected throughout the growing season in each habitat type. Two analyses commonly used in community ecology, multi-response permutation procedures (MRPP) and non-metric multidimensional scaling (NMDS) (McCune et al., 2002), will be used to evaluate if and how beneficial invertebrate communities vary in each of the surveyed habitat types.

To understand how environmental and plant variables affect natural enemy richness, diversity, and abundance across treatment types, generalized linear mixed models (GLMMs) with repeated measures will be used with natural enemy abundance, richness, and diversity as response variables. Habitat variables and types will be used as explanatory variables in the GLMM models. We will also use total blooming stem count and species richness as an explanatory variable in our GLMM models. GLMMs can handle a broad range of data types and are able to account for repeated sampling efforts within the same sample sites. We will consult with a statistician to ensure that appropriate model forms and statistical distributions are used. To understand how environmental and plant variables influence species composition of beneficials, we will correlate variables with NMDS axes.

Expected Results

In general, we predict that natural habitat fragments will support the highest diversity and richness of beneficial invertebrates because these habitats typically display a high degree of environmental heterogeneity and because pesticide exposure is limited to drift here, followed by mixed forb/grass cover crop sites (best cover-crop resources for beneficials), then grass-dominated cover crop sites. We expect the lowest beneficial invertebrate richness and diversity to be present in new orchards with bare-ground and mature orchards, as these sites have the heaviest pesticide applications, the least floral resources, and the most homogeneity in environmental variables.

We expect to identify habitat variables that are important for structuring beneficial invertebrate communities in the Mid-Columbia Basin, and that different groups of beneficials may be associated with different combinations of environmental variables. For example, many parasitoids depend on floral resources for food while hunting, so we expect that plant richness and diversity will be related to beneficial invertebrate community composition and that higher plant species richness and diversity will be correlated to more adult nectar-feeding species (Heimpel, 2019). In contrast, other beneficial groups, such as spiders and carabid beetles, may be more associated with physical plant structure and types of soil surface coverage. For example, some common groups of spiders are associated with large amounts of litter (Smith et al., 2019; Smith DiCarlo and DeBano, 2019). We expect multivariate analyses to reveal that cover-cropped sites are most similar to each other while mature orchard, bare ground, and natural habitat sites differ substantially from each other and from cover-cropped sites in multivariate community space.

 

Objective 2: Determine the ability of different cover-cropping regimes (no cover crop vs. grass dominant cover crops vs. a grass and forb mixed cover crops) to enhance beneficial invertebrate communities.

Field Methods

To address Objective 2, we will use a subset of the 25 sites identified in the methods for Objective 1 will be used, including all new orchard sites with varied cover crop regimes (no cover crops vs. grass dominated vs. grass/forb mix), resulting in a total of 15 sites (5 replicates per cover crop regime). Beneficial invertebrates collected in the sampling efforts described above (Objective 1) will be used to understand how each of the three cover-cropping regimes affect abundance, diversity, richness, and community composition of beneficial invertebrates in new orchards.

Statistical Methods

To analyze difference in average abundance, richness, and diversity in each of the three cover-cropping treatments, we will use GLMMs, allowing us to determine which cover-cropping treatment produces highest abundance, diversity and richness of beneficial invertebrates.

We will conduct an indicator species analysis (ISA) to help us identify beneficial invertebrate taxa that are closely tied to certain cover-cropping treatments, allowing us to make specific estimates of what beneficial taxa producers may find if they implement each type of cover-cropping treatment. This will potentially allow producers to create habitat targeted at increasing specific beneficials.

Expected Results

Because adults of many beneficial species rely on nectar, we expect that the mixed forb/grass cover crop treatment will have higher abundance, richness, and diversity of beneficial invertebrate taxa, than the grass-dominated cover crop. We predict that bare ground will have the least abundance, richness, and diversity because of its lack of floral resources or habitat heterogeneity.

 

Objective 3: Investigate the ability of different cover-cropping regimes to reduce the abundance of three common pest taxa (SWD, aphids, and leafhoppers).

 Field Methods

To address Objective 3, we will count pest invertebrates on sticky cards and in other sampling methods employed. SWD will be counted on sticky cards (yellow sticky cards and delta traps) that were deployed in the field. Originally, we had .planned to use sticky ball traps for SWD and bucket traps for aphids but decided to drop these methods sampling methods based on preliminary collections in 2021. Simultaneously, 8 sticky cards (Murphy et al., 2012) will be used per site to sample aphids and leafhoppers (Figure 3). While we had originally planned to sample a random selection of trees from each site for aphids, preliminary sampling revealed that this was not an effective technique. Through multiple conversations with growers and fruit tree entomologists in the region, we also determined that aphids were not a significant concern as a pest as current pest control regimes used to limit other pest species are effective at managing aphids. 

Statistical Methods

We will use GLMM models that use SWD, aphid, and leafhopper abundance as a response variable to investigate if pest abundance is negatively correlated to beneficial invertebrate abundance or cover-cropping regimes.

Expected Results:

We expect that pest abundance will be lowest in mature orchards (because of pesticide application) but expect that within cover-cropping treatments, pest abundance will be lowest in mixed forb/grass cover crop sites, followed by grass-dominated cover crop sites, followed by bare ground sites. We expect pest abundance to be negatively correlated to natural enemy abundance.

Expected Impact for Producers:

One primary reason for low adaptation of sustainable cover-cropping practices is lack of information on the potential costs and benefits of cover-cropping (Daryanto et al., 2019). We expect that this work will generate useable information for producers to make informed decisions about cover-cropping regimes in newly established orchards. We expect this information will include suggestions on how to best plan cover-cropping regimes to enhance beneficial communities in non-productive orchard spaces (e.g., new orchards, natural habitat fragments).

The analysis of beneficial invertebrate communities in natural habitat fragments will likely demonstrate that these areas are useful to growers as source populations of beneficials. The analysis of plant communities in fragments will identify native plants that are strongly correlated to beneficial invertebrate taxa and may be desirable for inclusion in future cover crop seed blends. We expect habitat characteristic analyses to help growers determine where the most robust beneficial invertebrate communities are on their property, allowing for the development of more precisely designed IPM plans the bolster desirable invertebrate populations. In other orchard systems, effectively designed IPM plans have been found to increase worker safety, reduce production costs, and increase biodiversity conservation on farms (Goldberger and Lehrer, 2016).

Finally, and perhaps most importantly, we expect our study to verify that cover crops do not increase the abundance of common pests (e.g., SWD, aphids) and cherry X-disease vectors (e.g., leafhoppers). This is a crucial step to reassure producers that enrolling their EQIP eligible lands in NRCS CIS programs targeting pollinator and natural enemy habitat enhancements will not result in increased pest pressure. If funded, this project is likely to encourage more producers to enroll in these programs and pave the way for future NRCS CIS programs and funding to Oregon farmers.

 

Preliminary Work:

Completed Preliminary Work

In 2020, we sampled flying beneficial invertebrates at two sites for two weeks using delta traps baited with multi-component plant volatile lures (Figure 4) following the methods laid out in Jones et al. (2016). Ground dwelling beneficial invertebrates were sampled concurrently using pitfall traps. Additionally, during fall 2020, cover-crop treatments were planted in 5 new orchards. Half of each orchard was planted with grass-dominated cover crop seed blends and the other half was planted with a more forb-dominated cover crop seed blend. During the summer of 2021, we conducted preliminary fieldwork in 20 out of 25 of our field sites. We tested and evaluated each of the methods planned and refined some of our sampling plans based on this fieldwork. 

Figure 5. a) Delta trap with a multi-component lure, and b) beneficial invertebrates on a sticky card from a baited delta trap. Photos from preliminary methods testing in August 2020.
Research results and discussion:

We do not yet have any results as we have been in the field nearly continuously since the start of the grant period (April - July). We will update results over the course of the next year as we process invertebrates, enter data from field notes, and begin analyses.

While we had originally anticipated releasing several extension style videos before and during the field season that would introduce the project, we are still working on making those videos. We are behind on the videos since field work took longer than expected. We are nearly done collecting footage for the videos and will begin releasing these in September.

We have currently completed field sampling for April - July 2022. Most of our samples our currently stored in a freezer or in alcohol (Figure 6). As we have had time this summer, we have been sorting and pinning invertebrate samples.

Samples stored in alcohol
Figure 6: Samples stored in alcohol waiting to be processed.

We will start generating results this fall and winter as we get data entered and as we get more samples pinned and sorted.

Participation Summary
2 Farmers participating in research

Educational & Outreach Activities

Participation Summary:

Education/outreach description:

We have not yet conducted any outreach activities specifically connected to this grant. Throughout the late summer and fall we will focus on producing extension style videos designed to educate the public about the project. We did present some preliminary data from 2021 preliminary fieldwork to a group of growers, producers, and sustainable agriculture practitioners through the Western Farms for Biodiversity Summit in June of 2022 (Figure 1). This was communicating results from preliminary data and was not specifically tied to this WSARE grant, but it should help build interest in this project and get people interested in seeing our future results. 

Extension Presentation
Figure 1: Title slide of a virtual presentation associated with preliminary research conducted in 2021. This presentation was not connected to this WSARE grant, but will help build interest in the results that come out of this grant.
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.