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

Final Report for ANC92-012

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
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Project Information

Summary:

[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 ncrsare@unl.edu.]

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.

Research

Materials and methods:
Study Sites and Methods

Windbreaks: 15 study sites were selected on private farms or on the University of Nebraska Agricultural Research and Development Center, all in Saunders County, Nebraska. Ten of the sites are windbreak-sheltered, with five of the windbreaks oriented north-south and five east-west, and the remaining five sites have non-woody grass or forb edge vegetation. Eight of the 10 windbreak sites and all of the unsheltered sites are on private farms. The 19 participating farmers are providing study access to their land and information on pesticide and fertilizer use, cultural practices, and other cropping information. Vegetation measurements, collected at each site, include percent canopy cover and ground cover, tree diameter at breast height, and percentage of ground cover in forbs, grasses, litter, slash, or woody plants.

At each site, a 400-m census transect was established along the field edge (woody or non-woody) and two 200-m transects were established to run perpendicular from the edge into the adjacent crop fields (corn, grain sorghum, soybeans). During fall 1992 (October, November), each site was censused two times for preliminary assessment. During 1993, sites were censused four times each during winter (January, February), spring migration (late April, May), summer (June, early July), and fall (September, October), and three times during late summer (late July, August).

Riparian Corridors: 12 riparian study sites were selected in Saunders or Lancaster Counties on private farms or on the University of Nebraska Agricultural Research and Development Center near Mead. Eight sites are woody riparian corridors with varying amounts of woody vegetation within the surrounding agricultural area, and four have primarily non-woody grass or forb vegetation. Eleven of the 12 riparian sites are on private farms and the 11 participating farmers are providing study cooperation and information as in the windbreak study.

Sampling procedures are essentially the same as in the windbreak study. Birds in corridors are sampled using a fixed-width transect along the corridor-field edge. Birds recorded are those seen or heard 25 m into the corridor, or to the outer edge of the opposite side, whichever is less.

Birds in fields are sampled, when weather and field conditions allow, using two parallel, fixed-width transects extending perpendicularly from the corridor into the field. Sampling periods include spring, summer, late summer, fall, and winter. Vegetation measurements are similar to those in the windbreak study.

Research results and discussion:

Objective 1. To determine the impact of tree windbreaks on the distribution and abundance of crop pests and their natural enemies.

The first of objective of this grant was to compare the distribution and abundance of arthropod pests and their natural enemies in agricultural systems with and without shelter from trees and to differentiate trends. Shared natural enemies of tree and crop pests whose abundance could be enhanced through releases or habitat enrichment and crop pests that use windbreaks for harborage or as an alternative source of food were identified by periodically sampling all levels of the system throughout the year. The initial emphasis for studies on natural enemies was on avian and arthropod predators. Some data on small mammalian predators was collected.

Vertebrate natural enemies

Bird populations were sampled in the windbreak, in the adjacent sheltered crop fields, and in the similar crop fields that are unsheltered, using standard bird census techniques. The sheltered and unsheltered crop fields were compared and trends have been identified. From there, we will consider impacts, positive or negative, to the agricultural system and how the system might be managed to minimize the negative and maximize the positive. For example, comparison of vertebrate life history traits and patterns to those of insect pests might allow enhancement of specific vertebrates to help suppress insects damaging to agricultural crops or windbreak trees, and to provide other benefits to the agricultural system.

Abundance and distribution of arthropod pests of corn, grain sorghum, soybeans and cantaloupe and tree pests were evaluated during June through August. Overwintering pests in the windbreaks were evaluated in January. Pest abundance on corn, grain sorghum, soybeans and wheat were censused in the crops at distances of 0, 1/2, 1, 2, 5, and 10 times the height of the windbreak and at the same distances from the edge of the field in the unsheltered plots.

Abundance of western, southern, and northern corn rootworm, and striped cucumber beetle on cantaloupes were assessed using sticky traps. Soybean pests (bean leaf beetles) and sorghum pests were sampled by sweeping the foliage.

Abundance and distribution of arthropod natural enemies (primarily predatory spiders, beetles, and ants) in the trees and crops were evaluated three times while the crop was in the field, using pitfall traps, sweeps of the vegetation, and aerial counts. Sampling sites were located in the windbreak and within the crop at distances from the windbreak of 0, 1/2, 1, 2, 5, and 10 times the height of the windbreak. Sampling sites in unsheltered fields will be equivalent distances from the edge of the field.

During the 1993 field season the abundance of arthropod pests in corn, grain sorghum, and soybeans was sampled in late May, early July and early August. During each sampling period, pitfall traps were set and left out for three days then collected. Vegetation sweeps and branch shakings were performed on the days that the pitfall traps were set.

The weather during the 1993 field season was very unpredictable. Record amounts of rain fell on our study sites and daily high temperatures were below average.

Field Crops: Arthropods collected during the May and July sampling were identified to family, counted and the data analyzed.

Except for three fields, few pests were caught at any of the sites. These sites had high numbers of aphids in the pitfall traps during the July sampling period. These three sites were unsheltered, planted to grain sorghum, and located within one-half mile of each other.

The most abundant arthropod predators in the samples were spiders, carabid beetles, and ants. Spiders were apparently more abundant close to windbreaks and grassy edges. Spider numbers in pitfall traps, branch shakings, and vegetation sweeps, were also apparently higher in the windbreaks that contained coniferous trees such as juniper and scots pine. Two of the windbreaks contained mostly coniferous trees and the data collected from these sites indicate that spider numbers are higher relative to data collected from sites dominated by deciduous trees.

A vegetation survey of all 14 sites was conducted to determine the vegetative composition of the undergrowth at sheltered sites and the total species composition at the grassy or unsheltered sites. The survey determined that most of the unsheltered sites were dominated by smooth brome grass and the sheltered sites were dominated by catnip, smooth brome, and wild violet.

An analysis of tree species was also performed at each of the sheltered sites. The composition varied widely, but overall osage orange, mulberry, hackberry and plum trees seemed to dominate. Juniper and scots pine were present at only two sites, and these sites were within one half mile of each other.

Muskmelon: Abundance and distribution of pests and natural enemies in four muskmelon plots sheltered by multi-species windbreaks was compared to four unsheltered muskmelon plots. The muskmelons were planted in June and the arthropods were sampled in June, July, and August.

Pitfall traps placed at 0, 1/2, 1, 1 1/2, and 2 times the height of the windbreak were used to sample ground searching arthropod predators. These pitfall traps were left in the field for four days and then collected.

Sweep net samples taken at the same distances were used to sample predators and pests on the foliage. Tree pests were sampled by shaking individual branches. Crop pests were sampled by placing three yellow sticky traps (6 by 10 inches) equal distance apart in each muskmelon plot. Traps were collected and reset each week. Pests and natural enemies were counted within three days.

Abundance of striped cucumber beetles, southern corn rootworms and northern corn rootworms on sticky traps was similar in exposed and sheltered 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.

Objective 2: To determine the impact on crop yield of pest populations influenced by tree windbreaks

Growth and yield of corn, grain sorghum, soybeans, wheat and cantaloupe in field plots
sheltered by windbreaks and in unsheltered plots will be collected and correlated with the distribution of crop insect pests and their natural enemies. Ongoing studies at the ARDC are collecting growth and yield data on corn and cantaloupe crops. The pest and natural enemy data will be integrated with this research. Yield and growth data for corn, grain sorghum, wheat, and soybeans plots outside of the ARDC will be collected in cooperation with the growers. These data have been collected but are not summarized or statistically analyzed.

Research conclusions:

Positive Benefits: Woody corridors in agricultural landscapes can help reduce soil erosion, shelter crops from wind damage and desiccation, enhance moisture conservation, and serve as filters for field runoff, important for ground and surface water quality. They also provide wildlife habitat important to a variety of species in intensively farmed landscapes. The woody vegetation and associated wildlife provide recreational and aesthetic benefits in rural areas and may enhance the quality of life for farm families.

Field-edge windbreaks and riparian corridors, which tend to become naturally established with woody vegetation, are among the few woody habitats within the Midwestern farming region.

Some landowners clear the trees and shrubs, in part to increase crop area or to better accommodate farming equipment, but clearing the trees also removes benefits of the woody vegetation. A more thorough understanding of the values of these habitats will enable landowners to make better-informed management decisions about them.

Determination of the bird species and numbers using woody and non-woody corridors and their adjacent crop fields establishes baseline data for evaluating how such areas might be managed to enhance natural enemies of crop pests. Pest insects are susceptible to predation in both the crop field and in the field edge. At field edges, natural enemies can attack pest insects that come to the field edge for some life cycle need or that are blown there by the wind.

Our results indicate that field-edge vegetation benefits a wide variety of bird species, including insectivores and omnivores that likely have value as natural enemies of crop pests.

Further, our results indicate that neo-tropical migrant bird species, many of which are in decline, benefit from the woody vegetation as habitat during migration or for nesting, and the woody vegetation appears generally important to wildlife conservation in this agricultural area.

Herbaceous edges contribute habitat for additional species. Predation pressure on insect crop pests from birds and small mammals, based on predator foraging locations, appears to be highest within 50 m of field edges but occurs throughout fields at least 200m from edges.

Spiders were most abundant next to windbreaks or grassy field edges, and were higher in windbreaks containing coniferous trees such as juniper or scots pine, compared with windbreaks containing primarily deciduous trees. Spiders are generalist predators on a variety of insect pest species.

New Hypotheses: Field edges with woody vegetation, in comparison to non-woody, appear generally to have greater overall species richness (more bird species), more neo-tropical migrant bird species, and generally more individuals (greater abundance). Herbaceous edges, however, provided habitat for species such as dickcissels that do not frequent woody areas.

Bird abundance within the crop fields studied was generally similar regardless of edge type but species composition (which species are present) differed. In fields, bird species richness and abundance appear to be influenced by the edge vegetation present in the overall agricultural landscape and, in some cases, by the edge vegetation adjacent to a particular field.

The edge non-crop habitats are necessary components for most of the natural enemy complex and most were more abundant within 50 m of the edge. Avoiding pesticide application on strips of cropland adjacent to field borders might reduce their harmful effects to predators without increasing economic losses to crop damage. Finally, many of the birds in crop fields with herbaceous edges were species usually associated with woody habitats — shrubs or trees. So, the overall amount or landscape network of woody vegetation in the areas studied may have influenced bird counts in fields without woody edges. It appears that the overall amount or network pattern of a habitat type is an important management variable. Because both woody and herbaceous edges support specific bird species, landscape management plans should consider the amounts of similar habitats, woody or herbaceous, that are available near the respective edge types.

Economic Analysis

Data are being collected on crop yield and grower fertilizer and pesticide use at each site, but are not yet summarized or statistically analyzed. This will contribute to an economic analysis of production systems with windbreaks and those without windbreaks.

Farmer Adoption

Producer Involvement

Producers were involved in planting, maintaining and harvesting crops, and providing information on crop production practices at study sites. A meeting with cooperating producers in February 1994 was used to discuss project results to date, and to get producer input into 1994 field studies.

Participation Summary

Educational & Outreach Activities

Participation Summary

Education/outreach description:

Journal articles

Dix, M.E., Johnson, R.J., Harrell, M.O., Case, R.M., Wright, R.J., Hodges, L., Brandle, J.R., Schoeneberger, M.M., Sunderman, N.J., Fitzmaurice, R.L., Young, L.J., Hubbard, K.G. 1995. Influences of trees on abundance of insect pests: A review. Agroforestry Systems 29:303-311.

Dix, M. E., L. Hodges, J. R. Brandle, R. J. Wright & M. O. Harrell. 1997. Effects of shelterbelts on the aerial distribution of insect pests in muskmelon. J. Sustainable Agric. 9: 5-24.

Theses

Sunderman, N.J. 1995. Avian use of field windbreaks, herbaceous fencerows, and associated crop fields in east central Nebraska. M.S. Thesis. Univ. NE, Lincoln. 108pp.

Fitzmaurice, R.L. 1995. Avian use of riparian corridors and adjacent cropland in east-central Nebraska. M.S. Thesis. Univ. NE, Lincoln. 77pp.

Proceedings

Dix, Mary Ellen and Subhashini Donthiri. 1993.
Opportunities for biological control of insect pests in agroforestry systems. pp. 278-284. In: Society of American Foresters national convention. 1992 October 25-28; Richmond, VA. Washington, DC: Society of American Foresters.

Dix, M. E. et al. 1993. Influences of trees on abundance of natural enemies of insect pests. Proc. Third International Agroforestry Symposium. [August 16-18, 1993, Ames,Iowa].

Johnson, R. J., J. R. Brandle, R. L. Fitzmaurice, and K. L. Poague. 1993. Vertebrates for biological control of insects in agroforestry systems. Pp.77-84 in Biological Control of Forest Pests in the Great Plains: Status and Needs, J. A. Walla, M. E. Dix, and R. Cunningham, Coord. Proc. 44th Annu. Meet. Forestry Committee, Great Plains Agric. Council, Publ. No. 145.

Sunderman, N. J., R. J. Johnson, J. R. Brandle, R. M. Case, M. O. Harrell, M. E. Dix, L. J. Young, L. Hodges, R. J. Wright. 1994. Role of Birds in Sustainable Agriculture. Proc. 1994 Nebraska Fruit and vegetable growers Conference.

Published Abstracts

Fitzmaurice, R.L., and R.J. Johnson. 1992. Role of birds and riparian corridors in sustainable agricultural systems. Neo-tropical Migrant Bird Project Directory (abstract). “Partners in Flight” program, Midwest Working Group.

Dix, M.E.; et. al. Influences of trees on abundance of natural enemies. 1993. In: Opportunities for agroforestry in the temperate zone worldwide. The third North American
Agroforestry Conference. 1993 August 15-18. Iowa State University, Ames, IA. 9-10.

Fitzmaurice, R. L., R. J. Johnson, R. M. Case, and J. R. Brandle. 1993. Working towards sustainable agricultural systems through the study of birds and riparian corridors. Proc. Nebraska Academy of Sciences 103:20.

Fitzmaurice, R.L., R.J. Johnson, R.M. Case, and J.R. Brandle. 1993. Avian components of riparian corridors and adjacent crop fields. Proc. 55th Midwest Fish and Wildlife Conference.

Fitzmaurice, R.L., R.J. Johnson, J.R. Brandle, R.M. Case, and L.J. Young. 1994. Role of birds and stream corridors in sustainable agricultural systems. Proc. 1994 Nebraska Fruit and Vegetable Growers Conference.

Johnson, R. J. , K. L. Poague, R. L. Fitzmaurice, N. J. Sunderman, J. R. Brandle, M. E. Dix, R.
M. Case, M. O. Harrell, L. J. Young, R. J. Wright, L. Hodges. 1994. Combining biological conservation with the needs of people in rural and urban landscapes. Proc. 1st Annual Conference, The Wildlife Society, Albuquerque, New Mexico, September 1994.

Sunderman, N. J., R. J. Johnson, J. R. Brandle, R. M. Case, M. O. Harrell, M. E. Dix, L. J. Young, L. Hodges, R. J. Wright. 1994. Avian Components of windbreaks, herbaceous fencerows, and adjacent crop fields in southeastern Nebraska. Proc. 56th Midwest Fish and Wildlife Conference, December 1994.

Sunderman, N. J., R. J. Johnson, J. R. Brandle, R. M. Case, M. O. Harrell, M. E. Dix, L. J. Young, L. Hodges, R. J. Wright. 1994. Bird use of field edges and adjacent crop fields in southeastern Nebraska. Proc. Nebraska Academy of Sciences 104:27-28.

Sunderman, N. J., R. J. Johnson, J. R. Brandle, R. M. Case, M. O. Harrell, M. E. Dix, L. J. Young, L. Hodges, R. J. Wright. 1994. Bird use of field edges and adjacent crop fields in southeastern Nebraska. Proc. The Wildlife Society, Nebraska Chapter Annual Meeting and technical sessions.

Sunderman, N.J., Johnson, R.J., Brandle, J.R., Case, R.M., Harrell, M.O., Dix, M.S., Young, L.J., Hodges, L., Wright, R.J. 1994. Avian components of windbreaks, herbaceous fencerows, and adjacent crop fields in southeastern Nebraska. Proc. 56th Midwest Fish and Wildlife Conference, December, Indianapolis, Indiana.

Dix, M. E., M. O. Harrell, R. J. Wright, L. Hodges, J. Irwin, J. R. Brandle, R. J. Johnson, R. M. Case, L. J. Young, K. G. Hubbard, R. L. Fitzmaurice, N. J. Sunderman, and M. M. Schoeneberger. 1995. Distribution of Predators n Tree/Crop Ecosystems. Abstracts, 50th Meeting, North Central Branch, Entomological Society of America. (Lexington Kentucky).

Dix, M. E., M. O. Harrell, L. Hodges, J. R. Brandle, R. J. Wright, J. Irwin, R. J. Johnson, R. M. Case, K. G. Hubbard, R. L. Fitzmaurice, N. J. Sunderman, and M. M. Schoeneberger. 1995. Influence of vegetation on abundance of pest and beneficial arthropods in agroecosystems. Proc. 4th North American Agroforestry Conference. Pp. 54-55. (Boise, Idaho).

Dix, M. E., J. R. Brandle, R. J. Johnson, M. O. Harrell, R. J. Wright, R. M. Case, L. Hodges, and K. G. Hubbard. 1995. Biological control and beyond: capitalizing on the ecological interactions of agroforestry systems. Agronomy Abstracts, p58. (St Louis, Missouri).

Sunderman, N. J., R. L. Fitzmaurice, R. J. Johnson, J. R. Brandle, M. E. Dix, L. Hodges, L. Young, R. M. Case, and R. J. Wright. 1995. Avian use of woody vegetation in agricultural landscapes. Agronomy Abstracts, p52. (St Louis, Missouri).

Johnson, R. J., J. R. Brandle, N. A. Beecher, N. J. Sunderman, R. L. Fitzmaurice, R. M. Case, M.
M. Dix, L. J. Young, M. O. Harrell, R. J. Wright, and L. Hodges. 1996. Wildlife as natural enemies of crop pests. National Extension Wildlife and Fisheries Specialists Workshop. (Bellingham, Washington, June, 1996)

OTHER PRESENTATIONS:

Dix, M.E. et al. 1993. Impact of tree windbreaks in distribution of insect pests and their natural enemies in sustainable agriculture systems, Society of American Foresters 1993 National Convention. [November 7-10, 1993, Indianapolis, Indiana].

Dix, M.E. 1993. Center for Semiarid Agroforestry: In-house and cooperative research overview. 23rd Annual Meeting of the Horticultural Inspection Society. [October 27, 1993, Omaha, NE].

Fitzmaurice, R. L. 1994. Role of birds and stream corridors in sustainable agricultural systems. Meeting with cooperating Farmers, March 1994.

Sunderman, N. J. 1994. Influence of windbreaks on bird distribution in sustainable agricultural systems. Meeting with cooperating Farmers, March 1994.

Information on natural enemies of crop pests and related habitat management was included in at least four Conservation Reserve Program (CRP) meetings, one statewide (Sep 1995) and three for districts or extension programming units (March 1996). Materials used at these meetings and in a CRP reference notebook included information on the potential of pest suppression using natural enemies.

News Media

Radio: Project information included in at least 11 radio programs

Newspaper

“Balanced Landscape Provides Natural Defenses Against Pests” — University news release carried in at least seven newspapers.
“Our Friends, the Windbreaks” — editorial in Lincoln Journal newspaper discussed project.
“Shelterbelt benefits relayed at Veggie Conference” — University news release (2/18/94)
“Natural pest control gets attention” Lincoln Journal-Star Sunday feature article (7/24/94)

Project Outcomes

Recommendations:

Areas needing additional study

This study examined the effect of agroecosystem structure on the abundance and species composition of both vertebrate and invertebrate natural enemies of insect pests. For both groups of natural enemies, research is limited on relating abundance of natural enemies to their ability to control insect pests. Studies are needed on consumption rates of these natural enemies (both vertebrate and invertebrate) against different insect pests, and behavioral studies to better understand preferred habitats and feeding behavior of natural enemies.

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.