Project Overview
Annual Reports
Commodities
- Agronomic: corn, soybeans
Practices
- Crop Production: cover crops
- Pest Management: mulches - living
Proposal abstract:
Since their introduction in 1991, neonicotinoids have quickly become the most popular insecticides worldwide. Within the past decade their use as preventative seed coatings has expanded enormously and now hundreds of millions of acres of field crops are planted annually with neonicotinoid seed treatments (NSTs). Unfortunately, the great majority of NSTs are used outside an IPM framework with little regard for pest populations even though limited unbiased evidence suggests that NSTs improve yield and profitability. Moreover, recent evidence suggests that they can pollute surface water and negatively influence wildlife, including populations of pollinators. In addition, our ongoing research is documenting that NSTs are exacerbating slug populations in no-till crop fields by disrupting biological control. This issue is important because slugs are among of the most challenging crop pests faced by Mid-Atlantic and Northeastern field crop growers. To combat slug infestations and over-reliance on NSTs, we are collaborating with four farmers in central Pennsylvania to test an alternative approach that avoids NSTs and uses rye cover crops to provide an alternative food source for slugs while maintaining strong populations of potential predators. Our two specific objectives are to: 1. Determine the influence of a fall-established rye cover crop on slug and natural enemy populations and slug damage to corn; 2. Compare corn productivity and biological control of slugs in presence and absence of neonicotinoid seed treatments. A Partnership grant will allow us to hold field days promoting our efforts and partially compensate the growers for their time spent on the project.
Project objectives from proposal:
To combat growing slug infestations and over-reliance on NSTs, we would like to know if rye cover crops can provide an alternative food source for slugs while maintaining strong populations of potential predators.
Project objectives:
1. Determine the influence of a fall-established rye cover crop on slug and natural enemy populations and slug damage to corn.
2. Compare corn productivity, and biological control of slugs in presence and absence of neonicotinoid seed treatments.
We hypothesize that rye cover crop will decrease damage from slugs by two mechanisms: 1) reduced feeding upon plants of the cash crop because slugs prefer to eat rye over corn (unpublished data) and 2) increased mortality of slugs because rye cover crops will harbor greater predator populations. Further, we hypothesize that fields that receive untreated seeds will experience less damage from slugs than those receiving treated seeds because untreated fields will have stronger predator populations.
PROJECT METHODS
On four farms of members of the Pennsylvania No-Till Alliance, we established a factorial experiment crossing two levels of seed treatment (treated or untreated seed) with three levels of cover (bare plot, rye cover crop terminated before planting, rye cover crop terminated after planting). Two growers (Mr. Harbach and Mr. Anchor) will host the full design with six treatments replicated four times each (24 plots), whereas Mr. Lucas was not interested in a bare ground treatment, and Mr. Meyer was not interested in a later termination cover crop; thus two of the farms have a reduced number of treatments (four treatments, 16 plots) that fit within their production systems.
In autumn, rye will be planted either with 15” or 30” planters or a modified grain drill, depending on the grower’s equipment, and will be established so that rows of rye alternate with empty rows. In spring, we will plant glyphosate-resistant corn treated with the high rate of the neonicotinoid clothianidin (1.25 mg per seed). To terminate the rye, the cooperator will either use glyphosate herbicide two weeks prior to planting or 5 days following planting. We hypothesize that in both treatments rye will provide good quality habitat for predators, but in post-planting plots the slowly dying rye will also provide an alternative food source for slugs.
Rye and corn establishment, percent cover, slug abundance and damage will be compared among treated and untreated plots across the four locations by analysis of variance. At the end of the growing season, we will harvest the plots for yield using the growers’ field scale equipment. If variation between sites complicates analyses, we will use Z-scores to standardize value at each site relative to the controls and then analyze Z-scores across sites using ANOVA. We will use linear regression to relate continuous variables to one another (e.g., percent cover vs. slug damage). Because other early season pests may also infest our plots, we will scout them every other week and quantify their numbers. If pest populations exceed economic thresholds, we will protect plots as necessary. We will compare yield, pest populations, and the number of damaged plants among our treatments using ANOVA. Importantly, from our grower collaborators, we will know the cost of seed (rye and corn), scouting, any necessary pest control applications, and the value of yield. Including an economic component is critical to provide evidence that IPM-based production can compete with prophylactic seed treatments.
We will also sample natural enemy populations using pitfall traps (five per plot) and measure predation services using sentinel prey. Pitfall traps measure arthropod activity-density and comprise 32-oz plastic containers sunk in the soil and filled with small amounts of propylene glycol as a killing agent and preservative. We will establish the traps with lids to prevent accumulation of rainwater, and then remove the lids monthly (June, July, August) for 48h to capture arthropods and slugs. Because our previous research has identified the main slug predators in central Pennsylvania, our assessment will largely focus on C. tricolor and P. melanarius, but we will identify the arthropods we capture to the lowest taxonomic level possible.
We will also deploy pinned sentinel waxworm caterpillars (six per plot) in June, July, and August for three hours during the early morning, and then again in the early evening when predation by epigeal arthropods is high, and we will visit the prey every 90 minutes, recording the status of the waxworms and any predators present (as in Lundgren et al. 2006). We will use waxworm caterpillars rather than slugs because slugs are uncooperative sentinel prey despite our best efforts; slugs will pull themselves off of pins and even sacrifice themselves if we confine them with rings of salt or copper, which are known repellent.
We will compare predation rates (Z-scores if necessary) across the two factors (seed treatments and cover) and their interaction using linear mixed models, with location as a random factor (repeated measures if needed). We will compare activity density of C. tricolor and P. melanarius among treatments by ANOVA. Field community data will also be analyzed using multivariate statistics because the species are unlikely to be independent of each other. We will use linear discriminant analysis, or redundancy analysis (RDA), which is a linear method of direct ordination similar and complementary to principal components analysis (PCA). Significance of variables will be tested with a permutational analysis of variance (Anderson 2005) and a Monte Carlo simulation (999 iterations with a forward stepwise selection procedure) and ordination analyses will be conducted in CANOCO (V. 4.5; ter Braak and Šmilauer, 2002). We will also use linear regression to explore relationship between predation or predator communities with percent cover, slug densities, and other variables.
PROJECT TIMETABLE
(Previous to grant award) Fall 2014 November
Plant rye in assigned plots (four growers) Order corn for the four farms (Mr. Anchor))
Spring 2015
March through May
Measure slug populations every other week using 10 white roofing shingles per plot (Dr. Le Gall) Measure slug damages to rye on 40 plants per plot (Dr. Le Gall)
May
Terminate rye two weeks before planting corn (four growers)
Plant corn (four growers)
Terminate rye 5 days following planting corn (Mr. Harbach, Mr. Anchor, and Mr. Criswell).
Summer 2015
June through August
Measure slug populations (shingle traps) and scout for early pest every other week (Dr. Le Gall)
June
Collect pitfall trap samples (Dr. Le Gall)
Deploy pinned sentinel waxworm caterpillars (six per plot) for three hours during the early morning, and then again in the early evening (Dr. Le Gall)
Corn V1 stage. Measure slug damages to rye on 40 plants per plot (Dr. Le Gall)
Corn V3 stage. Measure slug damages to rye on 40 plants per plot (Dr. Le Gall)
Assess stand establishment using three quadrats at three points in each plot; count the number of plants in five randomly chosen 10-ft sections of row. Assess cover crop/crop residue per plot (i.e., percent cover) using the line- transect method (Dr. Le Gall)
Corn V5 stage. Measure slug damages to rye on 40 plants per plot (Dr. Le Gall)
July
Collect pitfall trap samples (Dr. Le Gall)
Deploy pinned sentinel waxworm caterpillars (six per plot) for three hours during the early morning, and then again in the early evening (Dr. Le Gall)
August
Collect pitfall trap samples (Dr Le Gall)
Deploy pinned sentinel waxworm caterpillars (six per plot) for three hours during the early morning, and then again in the early evening (Dr. Le Gall)
Fall 2015
October 2015
Harvest corn and measure yield (four growers)
6. HOW WILL YOU DISSEMINATE YOUR PROJECT RESULTS?
Collaborative work with growers, our main target audience, will directly test the widespread assumption that modern field crop production requires NSTs. It will also provide on working farms a robust demonstration that IPM can be manageable and profitable while simultaneously avoiding the environmental and non-target concerns associated with NSTs. After all, many growers were successfully growing corn, soybeans, and other crops using IPM prior to introduction of NST about ten years ago! If we can show growers a successful approach that considers pest populations and economics prior to any insecticide use while emphasizing some of the poorly discussed drawbacks of NSTs, we will encourage more growers to return to IPM, reducing the numbers of acres unnecessarily planted with NSTs. Such a reduction will decrease accumulation of NSTs in soils and waterways. We will work with the Pennsylvania No-Till Alliance, Penn State Extension, and other groups including NRCS and county-based conservation districts to organize field days at three of our research sites to share our approach, rationale, and findings. We will market these events to the MidAtlantic agricultural community. We will also discuss our results during Extension events throughout the autumn and winter extension seasons when we have audiences with thousands of growers. We will share our results through Penn State Extension’s Field Crop News, which is a year round production of the Crop Management Team (weekly during the growing season, monthly during the rest of the year) and is distributed to nearly 1500 subscribers each week. Finally will discuss and present our findings at national meetings (e.g., Entomological Society of America annual meeting); other than the postdoc salary, the EPA grant will cover travel to this national conference.