Understanding aphidophagous hoverfly winter survival strategies in Midwest farmscapes to improve conservation biological control

Project Overview

Project Type: Graduate Student
Funds awarded in 2017: $11,993.00
Projected End Date: 03/01/2020
Grant Recipient: University of Illinois
Region: North Central
State: Illinois
Graduate Student:
Faculty Advisor:
Dr. Alexandra Harmon-Threatt
University of Illinois, Urbana-Champaign

Information Products


  • Agronomic: canola, clovers, corn, sorghum (milo), sorghum (sweet), sorghum sudangrass, soybeans, wheat
  • Fruits: apples, citrus, peaches
  • Vegetables: beans, cabbages, cucurbits, sweet corn
  • Additional Plants: native plants, ornamentals


  • Crop Production: pollination, pollinator habitat
  • Education and Training: on-farm/ranch research
  • Pest Management: biological control, cultural control, integrated pest management
  • Production Systems: agroecosystems, organic agriculture

    Proposal abstract:

    Understanding the biology of beneficial insects in agricultural landscapes for the development of conservation biological control schemes is an understudied area of research that is of vast importance. Hoverflies (family Syrphidae) uniquely provide multiple beneficial services for growers during different life stages. Adults are important pollinators of several crops while many larvae are voracious predators of soft-bodied insects like aphids. While most research focuses on attracting adult hoverflies and other natural enemies to agricultural landscapes during the growing season, little work has explored methods to retain populations over the winter, which is critical for controlling early aphid outbreaks in the spring. The proposed research will explore hoverfly winter survival strategies and develop methods for predicting and enhancing their prevalence in the landscape during the spring. This knowledge is of substantial interest to growers as it reduces wasted resources spent seeking control measures during the growing season. Using a combination of field observations and lab experiments, three objectives will be addressed to investigate two key aspects of hoverfly winter behavior: migration and diapause. Objective one is to use stable isotope analysis to determine if hoverflies migrate south in the fall to avoid winter temperatures, as observed in Europe. If hoverflies occupying agricultural landscapes are migratory, growers will be advised to focus on attracting these individuals to diapause on their property. Objective two is to use a series of laboratory experiments to determine the lower temperature survival thresholds of diapausing individuals, allowing predictions on the potential number of individuals emerging in the spring based on winter conditions. Finally, the third objective is to determine both when and where diapausing hoverflies emerge. This will be addressed by placing a series of emergence traps in fields and field margins to determine which location hosts the highest abundance of overwintering hoverflies. Simultaneously, this data will be compared to weekly environmental conditions to determine the cues that cause hoverflies to emerge from diapause. Farmers will be informed on how to best enhance natural pest suppression by manipulating farming practices to protect diapausing hoverfly populations. These outcomes will be summarized in a series of refereed scientific and extension publications, and a multitude of public presentations.

    Project objectives from proposal:

    By understanding the winter survival strategies of understudied hoverflies (Syrphidae), this project will provide growers specific recommendations on methods to increase and maintain these beneficial insects on their property post-harvest to maximize the pest suppression benefits. This work targets growers who struggle with aphid pests and seek alternative methods to control them. The overall learning outcome is to educate farmers on the importance of conservation biological control, and to increase the awareness and usefulness of beneficial arthropods such as hoverflies in the landscape. The specific learning outcome is to inform farmers on the benefits of retaining hoverflies in their landscapes over the winter, and how they can eliminate aphid problems in early spring before populations become large. Action outcomes are two-fold. The first is to provide farmers with tools to estimate survival and emergence times of hoverflies in the spring based on environmental conditions, allowing them to forecast the impacts they will have on aphid populations. The second major action outcome is to train farmers how to modify their practices in such a way that can attract hoverflies seeking overwintering sites in the fall. The overall goal of this project is to develop information on hoverfly winter survival strategies that will allow farmers to simultaneously reduce aphid outbreaks and enhance crop pollination, leading to increased profitability.

    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.