Marino Lab Research - Agricultural Ecology

Overview: Research in my lab focuses on exploring: 1) Ecology and evolution of entomophily in Splachnaceae mosses, 2) how landscape fragmentation and structure influences the population biology and the interactions between species in agricultural ecosytems, 3) post-dispersal seed predation, and 4) sustainable agriculture.
In agricultural ecosystems, we have explored how landscape structure (complex agricultural landscapes: small field size, many hedgerows and woodlots vs. simple agricultural landscapes: large field size, few hedgerows and woodlots) influences the effectiveness of the natural enemies of weed and insect pests. For example, we have shown (Marino, P.C. and D.A. Landis 1996. Effect of landscape structure on parasitoid diversity and parasitism in agroecosystems. Ecological Applications 6:276-284) that rates of parasitism of the true armyworm, a major pest of cereal crops, were much higher in corn fields in complex agricultural landscapes versus simple agricultural landscapes (6% vs. 21%).

However, this pattern was neither consistent across replicated simple and complex landscapes (Mennalled, F.D., P.C. Marino, S.H. Gage and D.A. Landis. 1999. Does agricultural landscape structure affect parasitism and parasitoid diversity? Ecological Applications (9:634-641) nor was parasitoid abundance and species composition at the landscape level consistent over time (Menalled, F., A.C. Costamagna, P.C. Marino, and D.A. Landis. 2003. Temporal variation in the response of parasitoids to agricultural landscape structure Agriculture Ecosystems & Environment 96:29-35). We have also examined weed seed predation at a landscape scale by comparing weed seed loss in a simple vs. a complex agricultural landscape.

Other studies of post-dispersal weed seed predation have explored the importance of spatial scale with respect to density dependence and the importance of dispersion and the background density/aggregation of seeds on the intensity of weed seed predation. Results of our work ( Marino. P. C., P. R. Westerman, C. Pinkert, W. van der Werf. 2005. Post-dispersal weed seed predation in cereal fields: influence of seed density and aggregation. Agriculture Ecosystems & Environment 106:17-25) suggests that there is considerable temporal and spatial variation in the intensity of seed predation and that the importance of weed seeds in the diet of seed predators changed seasonally such that the presence/absence of density dependent seed predation is likely to be a function of the spatial scale at which densities are either naturally or artificially enhanced.

In other research in sustainable agriculture we assessed the benefits and problems associated with the use of killed mulched cover crops in the humid subtropical regions of the southeastern U.S. The use of killed mulched cover crops was explored as a more sustainable substitute to ozone depleting methyl bromide soil fumigation as a means of weed and insect pest control. Specifically, vegetables were grown under conventional and organic mulch systems and the systems were compared by monitoring weed species diversity and abundance; soil-borne fungal pathogens, nematodes, and root health; populations of pest and beneficial insects, soil fertility levels and N fixation by cover crops, crop yields and quality; and productions costs and labor required. This research has resulted in 3 publications (Keinath, A. P., H. F. Harrison, P. C. Marino, D. M. Jackson, and T. C. Pullaro. 2003. Increase in populations of Rhizoctonia solani and wirestem of collard with velvet bean cover crop mulch. Plant Disease 87:719-725; Harrison, H. F., D. M. Jackson, A. P. Keinath, T. C Pullaro and P. C. Marino. 2004. Broccoli production in cowpea, soybean and velvetbean cover crop mulches HortTech 14:484-487; Pullaro, T. C., P. C. Marino, D. M. Jackson, H. F. Harrison, and A. P. Keinath, 2006. Killed cover crops as mulches for vegetable production: effects on weeds, weed seeds, and pest insects. Agriculture Ecosystems & Environment 115:97-104).