Interactions between predators and insect-parasitic nematodes in soil

• 2000 annual report
• 2001 annual report
• 2002 annual report

In this research we are evaluating the interactions between various types of soil fauna and insect-parasitic (beneficial) nematodes used for biological control of soil-dwelling pests. Potential responses include predation impacts on (augmented or applied) nematode populations, or non-target effects of beneficial nematodes on the soil (“decomposer”) community. Three strains of beneficial nematodes were applied inundatively, simulating commercial application, and via infected insect cadavers, simulating natural infection, in both conventional-till and no-till corn. Data indicate that soil fauna responses to nematode application, both inundatively and via natural infection, are most evident at the level of individual taxa, rather than at the level of abundance and diversity. Differences in abundance and diversity of particular groups of soil fauna due to tillage (higher in no-till than conventional-till) and to time (higher at 24 hours than at 4 hours) were also detected. (GSA-21)

Introduction

In an agricultural setting the soil community plays a critical role in decomposition, nutrient cycling and the control of pathogens and pests of crops. Conservation and augmentation of soil-dwelling predators and pathogens may enhance the control of agricultural pests. The purpose of this research is to examine the response of soil fauna to an applied biological control agent; insect-parasitic nematodes. Insect-parasitic nematodes in the families Steinernematidae and Heterorhabditidae occur naturally in the soil and are also applied inundatively, like a pesticide, at the commercial rate of 2.5 billion/hectare. In field applications, recovery of nematodes directly following application may yield less than 50%. This has generally been attributed to abiotic factors. Biotic factors, however, may also impact applied or augmented nematode populations.

The objectives of this research were to:
1) Evaluate the response of soil fauna to native and introduced insect-parasitic nematodes applied inundatively or via an insect cadaver, simulating a natural infection.
2) Evaluate the effects of tillage on the soil fauna response.
3) Evaluate the effects of time on the soil fauna response