Research Accomplishment Reports 2010

Effects of Prey Biodiversity on Pest Regulation by Generalist Predators

J.D. Harwood
Department of Entomology

 

Non-Technical Summary

Increased acreage of low-input, sustainable and organic agriculture can enhance biodiversity of predator and prey populations, with a concomitant reduction in pesticide application. However, the changing structure of arthropod populations may have profound effects on food web processes and ecosystem functioning. We have a very poor understanding of the consequence of these changes relative to integrated management of pests in agriculture; enhanced biodiversity can promote natural enemy population growth, but conversely may divert predators from feeding on target pests and towards alternative food sources. This research will therefore focus on identifying the structure of arthropod communities in agroecosystems, and the consequence of biodiversity on foraging dynamics of arthropod predators.

2010 Project Description

Research in Kentucky is continuing across a range of different cropping systems (winter wheat, corn, alfalfa) to further understand the role of generalist predators in biological control. This research includes the training of four graduate students and two postdoctoral research associates. This research seeks to better understand the mechanisms of foraging and, crucially, how diversity impacts ecosystem services provided by these natural enemies.

In addition to the utilization of molecular biology techniques to better address these questions, behavioral and ecological field experiments are being integrated into research projects that provide complimentarity to the molecular approach.

A major thrust of the project is the development of alternative management practices that promote predator diversity that can translate into reduced pest impacts across crops.

Research also continues to optimize molecular detection protocols for the study of food web ecology (published in Molecular Ecology Resources) as well as documenting the significance of pollenivory in an important group of natural enemies, the Linyphiidae (published in Arthropod Plant Interactions).

2010 Impact

(1). Pollenivory in spiders. Dietary diversification, including consumption of plant tissues, can enhance the fecundity of generalist predators resulting in improved control of pest prey. However, documentation of such a phenomenon in spiders is rare despite their foraging behavior placing them in contact with such a food source. Published research revealed the high capacity for pollenivory to occur in spiders and, crucially, the likelihood for high interception frequency of pollen under field conditions.

(2). Aphid falling rate and spider interception. The restriction of aphid reestablishment onto plants by epigeal predators represents a critical component of integrated pest management. It is therefore necessary to quantify the falling rates of aphids in order to better understand the role of ground-based predators. This study examined falling rates of aphids and revealed high (up to 70% of the population) falling rates per day. This has important implications for pest management and biological control in winter wheat and other agricultural systems.

(3). Food limitation in spiders. Understanding the food availability to generalist predators forms a critical part of pest management approaches. This study examined diel and seasonal variation in prey availability and revealed significant levels of food limitation to linyphiid spiders. Additionally, significant variation in availability of prey over a diel cycle was evident, revealing clear trends for prey availability in the field.

(4). Molecular characterization of sampling techniques. Molecular tools that characterize the structure of complex food webs and identify trophic connectedness have become widely used in recent years. However, these approaches are also subject to error due to inappropriate sampling methodology. In a technical advance, the likelihood for misinterpretation of food web connections was examined under field conditions and revealed to be insignificant thereby validating vacuum suction sampling for molecular gut content analysis.

(5). Field Guide to the Slugs of Kentucky. A booklet was published that documents the status and basic biology of slugs in Kentucky. Although the primary focus is on Kentucky, this publication has relevance across most states east of the Rockies.

2010 Publications

Peterson, J.A., Romero, S., Harwood, J.D. (2010). Pollen interception by linyphiid spiders in a corn agroecosystem: implications for dietary diversification and risk assessment. Arthropod-Plant Interactions, 4, 207-217.

Chapman, E.G., Romero, S., Harwood, J.D. (2010). Maximizing collection and minimizing risk: does vacuum sampling increase the likelihood for misinterpretation of food web connections? Molecular Ecology Resources, 10, 1023-1033.

Jaramillo, J., Chapman, E.G., Vega, F.E., Harwood, J.D. (2010). Molecular diagnosis of a previously unreported predator-prey association in coffee: Karnyothrips flavipes Jones (Thysanoptera: Phlaeothripidae) predation on the coffee berry borer. Naturwissenschaften, 97, 291-298.

Kerzicnik, L.M., Peairs, F.B., Harwood, J.D. (2010). Implications of Russian wheat aphid, Diuraphis noxia (Kurdjumov), falling rates for biological control in resistant and susceptible winter wheat lines. Arthropod-Plant Interactions, 4, 129-138.

Romero, S., Harwood, J.D. (2010). Prey utilization by a community of linyphiid spiders: variation across diel and seasonal gradients. Biological Control, 52, 84-90.

Thomas, A.J., Mc Donnell, R.J., Paine, T.D., Harwood, J.D. (2010). A Field Guide to the Slugs of Kentucky. University of Kentucky Agricultural Experiment Station Publication SR-103. 34 pp.