Predator-prey interactions in a high residue, reduced tillage agroecosystem

Predator-prey interactions in a high residue, reduced tillage agroecosystem

Summary

Many studies have noted the significance of reduced tillage and increased crop residue to the generalist predator community in agroecosystems. However, many of these studies have assumed their benefit to levels of predation and biological control without actually measuring them (Letourneau and Bothwell 2008). As such, we will monitor both the early-season pests and predator communities in an organic reduced tillage system, in which cash crops are no-till planted at three different dates into a heavy mulch layer created by managing a winter cover crop with a roller-crimper. Additionally, we will conduct predation assays to help estimate potential levels of predation. By evaluating both pest and beneficial arthropod communities, and conducting predation assays, we can better understand how reducing tillage in a cash crop – cover crop rotation may benefit organic growers in managing pests, and provide information to support grower decision-making about whether adoption of these practices for their tangible benefits to on-farm sustainability will be advantageous.

Objectives/Performance Targets

Objective 1: Characterize the beneficial and early-season pest arthropod community in a high cover crop residue environment associated with a reduced-tillage organic feed grain rotation.
Completed: A rigorous set of sampling of the arthropod communities at the ground level was been conducted in 2013. This included pitfall trapping at two points for each cash crop treatment (before and after cash crop planting) and once in wheat, as well as assessment of the Lepidopteran and slug populations at the ground level in the cash crops.
To be completed: Identification of the captured arthropods and analysis of data.

Objective 2: Determine the effect of three cover crop management and cash crop planting dates on the arthropods in a reduced-tillage organic feed grain rotation.
Completed: The sampling described above proceeded in two cash crops (corn and soybean) planted at three different dates.
To be completed: Identification of the captured arthropods and analysis of data.

Objective 3: Determine the relationship between the arthropod community and early season crop damage and plant population in a reduced-tillage organic feed grain rotation.
Completed: Crop damage assessments in corn and soybean.
To be completed: Analysis of data to find patterns between arthropod activity and crop damage.

Objective 4: Determine the potential impact of generalist insect predators on populations of early-season pests associated with a reduced-tillage organic feed grain rotation.
Completed: In-field predation assays to determine level of predation on live waxworms (to serve as proxy for Lepidopteran pests), in-field day- and night-time observations of waxworm baits to identify primary arthropod predators.
To be completed: In-laboratory assessment of feeding damage of waxworm baits (waxworms have been frozen until identification may proceed. Analysis of data to determine patterns between arthropod activity, in-field predation, and cash crop damage.  

Objective 5: Provide opportunities for the exchange of information with organic growers about this production system and its effects on beneficial and pest arthropods.
Ongoing.

Accomplishments/Milestones

January – May, 2013: Purchased supplies in preparation of the field season; final planning for field work and practice of methods (e.g. night-time observations of arthropod activities); prepared data sheets and finalized experimental design.

March – Mary, 2013: Co-taught a course in Field Crops Entomology to approximately 25 undergraduate students at Penn State, discussed in brief my project and the impacts on beneficial arthropods.

May, 2013: Hired an undergraduate student to assist with fieldwork and processing of field samples in the laboratory. Immediately began training.

May – August, 2013: Conducted fieldwork associated with my project with the help of the assistant. Fieldwork was conducted mostly as designed, with an additional trapping period prior to control of the cover crop. Otherwise, trapping of arthropods, observations of arthropod activity, and assessments of crop damage have proceeded as planned (Objectives 1-4).

August – Present: Samples of arthropods captured in the field are currently being processed in the lab, with the help of the field assistant. Samples have been cleaned and are ready for preliminary sorting by the assistant, after which I will proceed with the arthropod identifications. It will likely take the entire Spring semester to complete this process.

November, 2013: Attended the Entomological Society of America annual meeting. I did not present, but was able to obtain helpful information from other studies that might inform my own work (not NESARE funded).

Ongoing: Attending planning meetings and further finalizing 2014 schedule for outreach and extension. To date, there may be an opportunity to present at the Pennsylvania Association for Sustainable Agriculture annual meeting in February, and I will present at the 2014 Penn State Sustainable Cropping Systems Triad Symposium in March.

With the additional sampling period added to assess the impact of the living cover crop on arthropod activity, as well as the addition of in-field observations, it was difficult to coordinate the fieldwork schedule. The increased sampling effort meant that I required support beyond that I had originally proposed (I hired one field assistant with my NESARE grant), and if it weren’t for the time volunteered by others, this part of the project would not have been possible. It became apparent pretty early on in the field season that a great deal of hard work would be necessary to complete everything. Additionally, the weather was interesting this year, which may result in unusual arthropod patterns. In looking at the samples briefly, so far, it does seem like there will be some interesting and significant differences between my treatments, addressing Objectives 1-4.

Impacts and Contributions/Outcomes

This year was particularly busy with fieldwork, with fewer opportunities for extension. In my interaction with others throughout the year, however, it does seem as though people are interested in arthropod conservation in agriculture and the potential benefits to the agroecosystem. I suspect that with the coming year and in the generation of my own data in meeting the above objectives, I will have many opportunities in 2014 to discuss my project. I hope to complete an extension piece as soon as my data from 2013 will allow, so that I can further share the results of my work.

Collaborators: