Using Social Network Analysis to Understand Pest Management Used by Vegetable Growers

The July “Pests and Progress” webinar featured a presentation about carrot weevils and management efforts, along with an analysis of how social networks can influence adoption of IPM practices. Efforts with the carrot weevil were used as an example.  

Dr. Elizabeth Long, assistant professor and extension specialist from Purdue University, started the webinar by explaining why carrot weevils are important pests in  the Great Lakes region. These weevils significantly influence yields of parsley, carrots and celery, and they are difficult to manage. Dr. Long described monitoring methods, which include setting traps in the spring and scouting stems for egg scars during the growing season. Management strategies were also shared to provide context for the social network analysis leading us to wonder: Are farmers using the IPM strategies and they are not effective? Or is more effort needed to understand why farmers are not using recommended methods?

Research trials showed that delayed planting, one of the IPM strategies recommended for carrot weevil, was not effective at reducing weevil populations or egg laying. Anecdotal experiences from a farm that struggled with carrot weevil showed that one recommended practice is effective: crop rotation. If parsley, celery and carrot are not planted or are planted at least 1/4 of a mile away from where they were grown the previous year, the weevils cannot travel far enough to reach the new location. Without a place to lay eggs, the weevil population declines.

Next, Dr. Carlo Moreno, assistant professor of environmental studies at the College of Wooster, shared factors that affect whether farmers adopt new pest management practices. Farmer perceptions about whether a new practice was high risk or low risk is known to influence decisions about trying new pest management strategies. Something that helps farmers gain confidence that risks are low is to see management techniques being used successfully.

To better understand decisions farmers make about carrot weevil management, three questions were explored:

• How are farmers making decisions about carrot weevil management?
• Are farmers sharing information with each other?
• Are the IPM recommendations effective at a commercial scale?

Surveys were sent to farmers to learn about crops, pest management methods and where farmers seek advice for managing pests. This social network analysis showed that 37% of specialty crop growers relied heavily on pesticides; 18% used a combination of pesticides and one or two other management strategies; and 34% used three or more pest control practices. 

However, when it comes to identifying important advisors or information networks among specialty crop growers, most farmers seek advice from one or possibly two people. Growers tended to seed information from other growers or extension professionals, and there was not much overlap between different pairs. 

One important result to note is that farmers prefer to learn from people who are like them. So before giving advice or talking about pest challenges, it’s important to connect on a personal level and build trust.

Watch the recording to learn more about carrot weevils, social network analysis and how to start your own social network analysis of communication patterns in your area.