Comparing the Effects of Spring and Fall Tillage on Larval Populations of a Beneficial Insect

View the project final report

Commodities

• Vegetables: tomatoes

Practices

• Crop Production: cover crops, no-till
• Education and Training: demonstration, extension, farmer to farmer, on-farm/ranch research, participatory research, workshop
• Natural Resources/Environment: biodiversity
• Pest Management: biological control, integrated pest management, mulches - living, mulching - vegetative, prevention, traps, weed ecology
• Production Systems: organic agriculture
• Soil Management: green manures, organic matter

Growers committed to sustainable agriculture need simple, efficient strategies to maximize ecosystem services provided by beneficial insects on-farm. Ground beetles (Coleoptera:Carabidae) are ubiquitous in market vegetable systems. Many are primarily granivorous, and can substantially decrease the weed seed bank, reducing germination. Cover crops are widely used as cultural controls of weeds in annual vegetable crop systems, and can also enhance invertebrate weed seed predation by providing diverse food resources, shelter from the elements, and refuge from predation. In Indiana, the most abundant seed-feeding carabid species, Harpalus pennsylvanicus mates and lays eggs in the fall, after fall cover crops are planted. Larvae are vulnerable and relatively immobile until they mature the following year. Delaying tillage in the fall or spring extends the duration of seed predation services by adult beetles, but may adversely affect the larval population. In a market vegetable system, we will sample ground beetle larvae and adults in both spring and fall tillage systems, to establish optimal egg-laying sites and use peak larvae abundances to examine tradeoffs between tillage regimes, adult seed predation services and larval survival. This project will produce publications and outreach programs that will inform growers on how to maintain tillage regimes while minimizing larval mortality, protecting weed seed predation services for the following year. We will provide an additional ecological tool for managing weeds, helping to reduce costs of chemical inputs.

In the short term, this project will produce data that will inform growers of the tradeoffs between cultivation timing and weed seed predation services by beneficial insects. Growers will be prepared to make decisions about cultural weed-management tools with knowledge about the effects of tillage on the larval community specifically, which has been unavailable to this point. Preliminary data will be presented on farm tours and in grower-focused presentations across the state. Additionally, initial contact will be made with stakeholders that have previously not been involved in the Purdue Extension Program, to inform them of our efforts, and assess needs for future research.

In the intermediate term, this project will establish relationships with Purdue researchers and organic growers in Indiana. Few resources for organic growers have been available historically through the Purdue Extension program, and many are disengaged and unaware of work addressing problems related to organic weed/insect management. We will work with the Local Growers Guild, a cooperative of small-scale growers and retailers headquartered in Bloomington, Indiana, to disseminate and raise awareness of our relevant research, to build partnerships, assess needs, and seek advice for future projects. Our work will produce publications that will be promptly submitted to peer-reviewed journals. We will also prepare extension publications, which will be added to the key-word searchable knowledge base available to growers across the country.

Long-term outcomes will include a more comprehensive, deliberate approach to weed management. Our recommendations should reduce unnecessary mortality of carabid larvae, stabilizing populations of beneficial weed seed predators. This will increase recruitment in crop areas, leading to better weed control. Ultimately, we hope our work will reduce manual labor commitments, reduce costs of inputs, and improve the viability of sustainable market vegetable farming in Indiana.