Assessing the impact of crop rotation on the persistence and efficacy of insect-parasitic nematodes as biocontrol agents for soil-insect pests

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Assessing the impact of crop rotation on the persistence and efficacy of insect-parasitic nematodes as biocontrol agents for soil-insect pests

Field and specialty crop producers in the North Central Region are under increasing pressure from buyers to manage key pests, including Asiatic garden beetle and corn rootworm, more sustainably. We have preliminary field data suggesting that insect-parasitic nematodes (IPNs) offer promise on this front, but many of the factors limiting their effectiveness remain elusive. With a renewed focus on reducing pesticide use in agriculture, IPNs have been a subject of increasing research in recent years. However, previous work in this area has largely been pest or commodity specific, or limited in scope and scale. The impact of crop rotation and accompanying cultural practices on the persistence and effectiveness of these biocontrol agents has rarely been investigated. As such, these factors remain key unknowns for producers who are interested in adopting sustainable pest management practices and exploring the potential soil food web-related effects of diversifying their cropping systems. Our proposed work in mint-corn-soybean rotations addresses both of these unknowns and is specifically rooted in questions raised by producers.

We will evaluate the persistence of both endemic and introduced “persistent” IPNs and assess their capacity to maintain soil-insect pest populations below damaging thresholds as mint, corn, and soybean are rotated during a 3-year period. Using experimental plots at one of our Purdue managed farms (PPAC=Pinney Purdue Agricultural Center) and duplicating these treatments in commercial farmers’ fields, we will quantify IPN densities in inoculated and naturally colonized (endemic) fields over the course of the crop rotation cycle, and measure key environmental factors known to impact  their persistence and infectivity against focal soil-insect pests. We expect to gain key insights into the relationship between crop rotation and the sustainability and effectiveness of this biocontrol strategy when deployed against soil-dwelling pests of high-acreage, high-value cropping systems. Through this work, we will provide growers with field-based data; quantifying the processes, costs, and benefits of conserving endemic IPNs, and augmenting endemic populations with commercially available, “persistent” IPN strains. Information generated through this research will be disseminated through established and novel Extension networks we have developed over the last 5 years to provide growers with a realistic, unbiased picture of 1) the long-term sustainability of this biological control strategy, and 2) how it might be used in tandem with current and future cultural practices implemented on their farms.

We expect to gain critical insights into the effects of crop rotation on the persistence and efficacy of insect-parasitic nematodes (IPNs) - an aspect of biological control that has not previously been explored in the North Central region. As a result of our integrated Extension programming, specialty crop farmers will gain increased knowledge of IPN biology and their potential as biocontrol agents in rotation schemes that are familiar to the region. We expect this project to serve as an entry point for farmers that have not previously adopted biocontrol, with a broader goal of reducing dependence on insecticides.