Impact of Tree Windbreaks on Distribution of Insect Pests and their Natural Enemies in Sustainable Agricultural Systems

Project Overview

Project Type: Research and Education
Funds awarded in 1992: $0.00
Projected End Date: 12/31/1997
Matching Non-Federal Funds: $168,653.00
ACE Funds: $99,500.00
Region: North Central
State: Nebraska
Project Coordinator:
Robert Wright
University of Nebraska-Lincoln

Annual Reports

Information Products


  • Agronomic: corn, sorghum (milo), soybeans
  • Additional Plants: trees


  • Crop Production: windbreaks
  • Education and Training: on-farm/ranch research
  • Farm Business Management: whole farm planning
  • Pest Management: biological control


    [Note to online version: The report for this project includes tables and appendices that could not be included here. The regional SARE office will mail a hard copy of the entire report at your request. Just contact North Central SARE at (402) 472-7081 or]

    Vertebrate and invertebrate (insect) natural enemies of insects, and insect pests were sampled periodically during 1992-1994 in crop fields (corn, soybeans, grain sorghum, wheat and cantaloupe) sheltered and unsheltered by tree windbreaks. Field margins of these fields and tree windbreaks were also sampled. Crop fields with and without adjacent woody areas with waterways (riparian areas) were also sampled for bird species. Bird species were sampled by standard census observation procedures. Insects were sampled by sweep nets, pitfall traps, sticky traps and tree beating techniques, depending on the habitat. Few birds were observed in crop fields during the winter.

    Bird species diversity and abundance during the winter was higher in habitats with woody borders. Similar patterns were seen during the spring and summer of 1993; bird species diversity was higher in crop fields with woody borders, but bird abundance was not influenced by the presence or absence of woody borders. Similar trends were observed in habitats with woody riparian areas. Of the 64 bird species observed in habitats with tree windbreaks during the spring and summer, 54 species eat insects as either their sole diet or as part of their diet. Arthropod natural enemies and pest species were surveyed in crops and in windbreaks. Except for three unsheltered grain sorghum fields located close to each other that had high numbers of aphids in July, few insects pests were collected in grain crop fields during the summer. The most common arthropod predators were spiders, carabid beetles and ants. Spiders were most abundant close to windbreaks and grassy field edges. Spider numbers were also higher in windbreaks containing coniferous trees compared with sites dominated by deciduous trees.

    Abundance of striped cucumber beetles, southern corn rootworms and northern corn rootworms on sticky traps was similar in exposed and sheltered muskmelon plots. Western corn rootworms were significantly more abundant in exposed plots. More lady beetles and ichnemonid wasps were caught on traps in sheltered plots than exposed plots, especially during June. Few spiders, lacewings, or braconid wasps were caught at either location. Total arthropod abundance in pitfalls was higher in sheltered muskmelon sites than in exposed sites but did not vary in alfalfa. Total annual pest and predator abundance was similar in sheltered and exposed pitfalls in muskmelon and alfalfa plots.

    Abundance of ants, spiders, and carabids, the most common predators, and Orthoptera, the most common pest group, varied with crop, year, month and treatment. Total pest and rove beetle abundance in muskmelon pitfalls and total predator and rove beetle abundance in alfalfa pitfalls varied significantly with month and treatment more than year. Total annual arthropod, pest and predator abundance in muskmelon and alfalfa sweep samples did not vary among sheltered and exposed sites.

    Monthly abundance of total predators in muskmelon sweeps and total pests in alfalfa sweeps varied significantly in more than one year.

    Availability of pests and climatic conditions influenced predator abundance. Total annual arthropod and predator abundance within windbreaks varied with tree species and was significantly higher on pines. Pest abundance varied with month and was significantly higher on pines. Abundance of spiders, ants, lacewings, harvestman, and other predators was highly variable during the year. Availability of prey, foliage and climatic conditions may have influenced predator abundance on trees.

    Project objectives:

    To determine the impact of tree windbreaks on the distribution and abundance of crop pests and their natural enemies.

    To determine the impact on crop yield of pest populations influenced by tree windbreaks.

    Any opinions, findings, conclusions, or recommendations expressed in this publication are those of the author(s) and do not necessarily reflect the view of the U.S. Department of Agriculture or SARE.