Self-regulating weed control through the enhancement of beneficial ground dwelling invertebrates

Self-regulating weed control through the enhancement of beneficial ground dwelling invertebrates

Summary

The first year of the proposed project was undertaken. Pitfall traps were used to access the invertebrate community and seed cards were used to determine their effect on weed seed removal. The second year of data will be collected this summer/fall. In addition the laboratory choice study is in progress and will determine if weed seeds removed are species specific thereby facilitating a dominance shift in the weed community. All work has been overseen and approved by my research committee including Dr. Robert Gallagher (cropping systems ecologist), Dr. Shelby Fleischer (agroecosystems entomologist), Dr. Jonathon Tooker (agroecosystems entomologist), Dr. Tomas Carlo (seed ecologist) and Dr. Timothy Leslie (entomologist with carabid expertise).

Objectives/Performance Targets

Objective 1: Determine if the integration of legume green manure crops into reduced tillage cropping systems will enhance the diversity, abundance and activity of the beneficial ground dwelling invertebrate community, and thereby the pest management services with respect to weed seed predation.

The first year plots were established and data was collected. However the reduced-till organic plots were not viable. The weed density was significantly higher than in other treatments and it was decided to cease data collection in these plots. Pitfall trap data and seed card data was collected from 4 reps of each of the other plot types. Currently beetles captured over the summer/fall are being indentified and weed seeds eaten are being quantified.

Objective 2: Determine if weed seed ‘debits’ from the soil seed bank by invertebrate seed predators are weed species specific, thereby facilitating a shift in the weed community composition.

Beetles were captured over the summer/fall via pitfall traps and are being reared in the laboratory. Experimentation indentifying weed seed preference among Harpalus pensylvanicus has begun in the lab. Unfortunately other beetle species being reared in the lab died in significant numbers as result of either cannibalism or predation. As such, experimentation with another species will not be completed until more beetles are captures next field season. Preliminary analyses of VOC’s being released from the weed seeds by GCMS have begun.

Accomplishments/Milestones

The first year of data collection is completed. Pitfall traps were opened in the field twice in July, twice in August, and once in September. In conjunction with the traps being opened, seed cards were placed in the field at these same times. In addition much of the lab work examining weed seed preference of the beetles is well underway. Largely, the project progressed as expected. It appears that all carabid identification and seed data analysis should be completed before the end of winter. The only area that has progressed slightly slower than anticipated is the laboratory work with beetles. Although the Harpalus species of beetles were quite easy to rear other species were not as robust in the lab. After some examination and separation it appears that the Pterostichus sp. may have been preying upon other species as well as cannibalizing their own. Next year species will be separated in the laboratory accordingly.

Impacts and Contributions/Outcomes

It is early in the work to project but initial data suggests that corn yield and weed density were quite similar among the different treatment types. The integrated no-till system is undoubtedly a more sustainable system and if current data trends hold true, it is a viable system that could save farmers money while supporting environmental health. This treatment received considerably fewer inputs than some of the others and the similar weed control result is believed to be a result of the enhancement of the ground beetle population. Initial data analyses have shown around a 2-fold increase of beetles in these plots versus the conventionally tilled organic plots. The results can illustrate to farmers that the potential for cheaper and safer weed control is a real possibility. The proposed outreach of the project will take place in the summer of 2011. However some of the initial data and ideas have been presented to students at middle schools as part of the GK-12 NSF program which I am involved.

Collaborators: