- Agronomic: corn, soybeans
- Crop Production: conservation tillage
- Pest Management: biological control, chemical control, integrated pest management, prevention, weed ecology
No-till farming provides important benefits, but its sustainability is compromised by heavy reliance on pesticides for insect and weed control. The most common insecticides used in Northeastern field crops are neonicotinoid seed treatments. These seed treatments have questionable value for most farmers, and are not effective against slugs, considered by 80% of local no-till growers to be their most challenging pest. Because slugs ingest neonicotinoids but are not killed by them, they may pass these toxins to generalist predators and thereby disrupt biocontrol. My preliminary data support this notion because ground beetles were poisoned when they attacked slugs that had been fed on treated seedlings. There is a pressing need to examine the consequences of neonicotinoid seed treatments for whole farm ecosystems. I propose to evaluate non-target risks of neonicotinoid seed treatments in no-till corn and soybeans. Using laboratory and field experiments, I will examine the transfer of neonicotinoids up food chains from plants to slugs to predators, and the potential of this transfer to disrupt biocontrol of slugs, insect pests, and weeds. To provide a viable alternative to seed treatments, I will improve extension resources for early-season pest control in corn and soybeans, providing new publications that describe proven tactics for managing invertebrate pests. Finally, I will produce novel video footage highlighting important contributions of natural enemies to pest control in field crops. This footage will stimulate interest in IPM by illustrating predation services and depicting risks that accompany disruption of natural enemy populations.
Project objectives from proposal:
Objective 1: Determine whether insecticidal seed treatments can be transferred from crop plants to natural enemies via slugs.
The potential for insecticides to move up food chains and harm non-target species has been a concern since Rachel Carson discussed this phenomenon in Silent Spring. My preliminary studies suggest that
slugs may be important conduits of insecticides to natural enemies. Ground beetles, in particular, are frequent slug predators in agoecosystems (e.g. Symondson et al. 1996). I will use laboratory studies to determine whether slugs transfer to ground beetles a common neonicotinoid insecticide used on corn and soybean (thiamethoxam), testing for both lethal effects and sub-lethal effects on predator behavior.
Objective 2: Determine how insecticidal seed treatments influence pest communities and predation of multiple pest guilds in corn and soybeans under field conditions.
Seed treatments may harm natural enemies via several pathways, including direct contact in soil, contaminated prey (including slugs), and plant products (guttation drops, pollen). These multiple routes of exposure could disrupt generalist natural enemies important for pest control. Pterostichus melanarius, for example, is a common ground beetle species and a known slug predator, but it also preys on weed seeds and insect pests (Allen 1979). I will conduct field experiments with corn and soybeans comparing plots planted with untreated seeds to plots planted with seeds treated at standard low and high rates of thiamethoxam. To assess the influence of seed treatments on predation across the growing season, I will deploy sentinel prey, with separate assays to measure predation on slugs, insects, and weed seeds. Simultaneously, I will monitor pest populations and measure absolute densities of natural enemies. In addition to testing for seed treatment effects, the control plots in this study will reveal potential for biocontrol of slugs, insects, and weeds in no-till corn and soybeans.
Objective 3: Educate farmers about neonicotinoid seed treatments and alternative practices through extension materials, videos, and presentations.
While farmers receive promotional material from agricultural companies on benefits of seed treatments, they rarely hear potential downsides of the technology. Biocontrol contributes significantly to pest control, but is largely invisible because predation events are fleeting and rarely witnessed. Video is a powerful visual medium that I will harness to depict predator-provided pest control and non-target effects of insecticides on predator behavior and survival. Furthermore, I will produce two new publications to integrate and summarize early-season IPM practices for corn and soybeans into an easy-to-understand program.