No abstract

Vegetational diversity in agricultural systems is predicted to reduce herbivore populations, but we observed the opposite effect: higher nymph population densities of a functionally monophagous herbivore, the squash bug, Anasa tristis (Hemiptera: Coreidae) in a vegetationally diverse squash‐bean‐corn polyculture than in a squash monoculture. We examined spatial and temporal aspects of squash bug and predator populations in relation to vegetational diversity. Average colonization, oviposition, and mortality rates for the herbivore were similar in monocultures and polycultures. In the polyculture, however, we found that squash bugs eggs were highly aggregated on plants on the outer edges of plots. Predation was also lower on plants near the edges, allowing the large aggregations of eggs found in the polyculture to escape predation and ultimately produce more squash bugs. Spatial interactions between herbivores and natural enemies may underlie some of the general effects of vegetational diversity on herbivores.

'Aphid Alert' was the name used to identify a series of research and outreach initiatives undertaken from 1992 to 2003, and in some instances since, to address potato virus problems in seed potato production in the Northern Great Plains (NGP) of the USA, in particular northwestern Minnesota and eastern North Dakota. Aphid Alert was adopted from the name of a pest management advisory newsletter sent to Minnesota and North Dakota seed potato growers in 1994, and again from 1998 to 2003. The name found popular acceptance and was applied, even retroactively, to a series of related research/outreach activities. This chapter focused primarily on the areawide aphid-trapping network operated by the University of Minnesota from 1992 to 1994, and again from 1998 to 2003. Data presented here on potato seed lot rejections due to potato viruses were provided by the Minnesota Department of Agriculture Seed Potato Certification Program. Data presented here on aphids (reported as numbers or percentages of total captures) are from the subset of traps that were located in the NGP portion of the network.