DOI: 10.5061/dryad.mcvdnck9h
title: Preventative insecticides reduce seedling injury, but do not increase yield in Bt and non-Bt corn grown in the Mid-Atlantic

description: BACKGROUND: Field corn production systems rely on preventative insect
 management tactics, including hybrids expressing plant incorporated
 protectants that are treated with neonicotinoid seed treatments, and
 sometimes in-furrow pyrethroids. While effective seedling pest control can
 be crucial because of the cost of replanting, these treatments target many
 of the same pests and may add unnecessary costs for growers. Further,
 seedling pests in the Mid-Atlantic tend to be sporadic, and preventative
 insecticides may negatively impact natural enemies. To better understand
 the value of common preventative tactics, we evaluated pest pressure and
 compared a neonicotinoid seed treatment (clothianidin) and an in-furrow
 pyrethroid (bifenthrin) in Bt and non-Bt corn hybrids. RESULTS: In Bt
 hybrids, the in-furrow pyrethroid did not decrease pest injury, increase
 stand, or increase yield, while the neonicotinoid seed treatment decreased
 pest injury and increased stand but did not increase yield. In a non-Bt
 hybrid, both insecticides decreased pest injury, but neither increased
 stand or yield. Above- and below-ground pest injury was scarce throughout
 the study, but even in the site-year with the most extensive injury,
 insecticides did not result in yield gains. CONCLUSION: Implementing
 efficient economically and environmentally sustainable corn pest
 management requires a thorough understanding of the contributions of each
 component of the pest control system. By thoroughly exploring pest
 pressure in Bt and non-Bt systems, this study shows that preventative
 insecticide use could be scaled back in many cases, especially given the
 environmental and economic costs associated with them.
description: ## Preventative insecticides reduce seedling injury, but do not increase
 yield in Bt and non-Bt corn grown in the Mid-Atlantic
 [https://doi.org/10.5061/dryad.mcvdnck9h](https://doi.org/10.5061/dryad.mcvdnck9h) ## Description of the data and file structure These data sets contain the data collected in a three year (2020-2022) field study across three research farms in Maryland, United States. In the study, 2 insecticide treatments (a neonicotinoid seed treatment and an in-furrow pyrethroid treatment) were compared to an untreated control in Bt and non-Bt field corn. The treatments were each replicated three times in each corn hybrid in a Latin-square design. We sampled early-season performance (plant stand, stunted plants, plant height) and insect damage, damage in the mid- (whorl stage/R2) and late-seasons (ear stage), and stand and stunted plants at the end of the season and collected yield data. We also collected data on migratory lepidopteran pests (corn earworm, fall armyworm, and Western bean cutworm). The associated codes analyze insecticide treatment impacts to the outcome variable data collected separately in the Bt and non-Bt hybrids. ### Data sets and variables #### File: locations.xlsx **Description:** This data set provides the locations of the research farms in order to generate a map showing the locations of the research plots in the context of the Mid-Atlantic region. ##### Variables * Latitude * Longitude #### File: seedling\_stand\_stunted\_pest\_damage.xlsx **Description:** Seedling sampling data for Bt and non-Bt corn. This data set contains stand counts (healthy plants), stunted plant counts, and counts of plants injured by a range of pest types as well as physiological and deer-injured plant counts. Metadata tab describes experimental design, sampling, and variables in detail.  ##### Variables * corn * year * date * location * growth stage * days after planting * rep * treatment * subsample * stand * stunted * soil pest * grub * wireworm * cutworm * armyworm * flea beetle * slug * stinkbug * non-ID chewing * physiological * deer #### File: plant\_height.xlsx **Description:** Height measurements that were taken during the seedling stage while sampling stand, stunted, and pest damage counts in Bt and non-Bt corn. Metadata tab describes experimental design, sampling, and variables in detail.   ##### Variables * corn * year * date * location * growth stage * days after planting * rep * treatment * subsample * plant * plant height (in) #### File: insect\_area.xlsx **Description:** The area of feeding injury done to seedlings by insect pests in Bt and non-Bt corn. These data were collected in 2021 and 2022. Metadata tab describes experimental design, sampling, and variables in detail.  ##### Variables * corn * year * location * rep * treatment * subsample * plant * insect area (cm^2) #### File: whorl\_damage\_2020.xlsx **Description:** The leaf injury data collected in 2020 from one leaf in the R2 stage in Bt and non-Bt corn. Tab 2 is incidence and tab 3 is severity. Metadata tab describes experimental design, sampling, and variables in detail.  ##### Variables * corn * days after planting * date * location * rep * treatment * subsample * caterpillar incidence * Japanese beetle incidence * grasshopper incidence * piercing-sucking incidence * leaf beetle incidence * leaf miner incidence * total plants * caterpillar area (cm^2) * Japanese beetle area (cm^2) * grasshopper area (cm^2) * piercing-sucking area (cm^2) * leaf beetle area (cm^2) * leaf miner area (cm^2) #### File: whorl\_inc\_2years.xlsx **Description:** Feeding injury done to the whole plant in the whorl stage in 2021 and 2022. Tab 2 is the count of different types of damage, while tab 3 gives the severity on a 5-point scale:  | The rating for the damage: 1) Unblemished plant with no feeding injury, 2) Minor feeding: isolated holes or small rows of holes from boring lepidopterans, 3) Moderate feeding: Many rows of boring holes/extensive leaf feeding, but stalk intact, 4) Feeding has damaged the stalk and/or unemerged tassels, 5) Corn is completely defoliated, stalk no longer intact | | :---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | Metadata tab describes experimental design, sampling, and variables in detail.  ##### Variables * year * date * days after planting * location * corn * growth stage * rep * treatment * sub sample * row * caterpillar incidence * grasshopper incidence * Japanese beetle incidence * aphid incidence * stinkbug incidence * total plants sampled * caterpillar severity (1-5) * grasshopper severity (1-5) * Japanese beetle severity (1-5) #### File: ear\_damage\_incidence\_severity.xlsx **Description:** Contains the incidence (tab 2) and severity (tab 3) of ear pests (caterpillar, stink bug, and sap beetle) in Bt and non-Bt hybrid corn at soft-dough stage. Metadata tab describes experimental design, sampling, and variables in detail.  ##### Variables * corn * year * date * days after planting * location * growth stage * rep * treatment * sub sample * caterpillar incidence * stinkbug incidence * sap beetle incidence * stink bug live * cowhorn * deer * ear * caterpillar area (cm^2) * stinkbug area (cm^2) * sap beetle area (cm^2) #### File: yield.xlsx **Description:** Yield collected at maturity from Bt and non-Bt corn. Metadata tab describes experimental design, sampling, and variables in detail.  ##### Variables * year * location * corn * rep * treatment * bushels per acre * kg per hectare #### File: final\_stand\_stunted.xlsx **Description:** Counts of healthy and stunted plants at the end of the growing season, shortly before harvest in Bt and non-Bt corn. Metadata tab describes experimental design, sampling, and variables in detail.  ##### Variables * corn * year * date * location * rep * treatment * sub sample * stand * stunted #### File: pheromone\_traps.xlsx **Description:** Capture counts for pheromone traps targeting corn earworm, fall armyworm, and Western bean cutworm throughout the growing season. Metadata tab describes experimental design, sampling, and variables in detail. Periods indicate missing data when traps were not checked that week or trap captures were lost.  ##### Variables * year * location * date * trap * count * notes ## Code/software ### File: Cramer\_PMS\_analysis.Rproj This is the R project in which all the analyses were run. In order to reproduce this project: 1\) Download this R project 2\) If needed, download all excel files into the Raw data folder 3\) If needed, download all markdown files into the Annotated code folder 4\) Using the Knit dropdown for each markdown file, set the Knit Directory to Project Directory 5\) Run the code in the "01 packages to install" markdown You should now be able to run all of the markdowns in any order to reproduce the analysis performed for this study. ### File: 01\_packages\_to\_install.Rmd This markdown file contains code to install the packages needed to run the analyses in the subsequent markdowns. It also includes comments with a brief description of what each package will be used for.  ### File: 02\_locations\_map\_figure.Rmd This markdown file contains the code to generate a map of the research farm locations from the study. It uses state and county data from the 'maps' package and the gps coordinates from the locations.xlsx file. ### File: 03\_Seedling\_insect\_damage.Rmd This markdown file contains the code used to clean and prepare, explore, analyze, and summarize the seedling insect injury data. Preparation includes grouping damage categories (e.g. soil_pest, wireworm, and grub are added together into a single soil pest category), as well as pooling across subsamples (adding injured plant counts across subsamples to give total counts per replicate plot). Exploration and analysis are done separately for Bt and non-Bt data and include visualizing the data for each pest grouping with histograms and boxplots and analyzing treatment effect on total insect damage using linear mixed effects models. Model checking and post-hoc tests are performed. Means and standard errors are generated. ### File: 04\_Plant\_height.Rmd This markdown file contains the code used to clean and prepare, explore, analyze, and summarize the seedling height data. Preparation includes converting plant height from inches to centimeters and calculating the mean height across the subsamples within replicate plots. Exploration and analysis are done separately for Bt and non-Bt data and include visualizing the height data with histograms and boxplots and analyzing treatment effect on seedling height using linear mixed effects models. Model checking and post-hoc tests are performed. Means and standard errors are generated. ### File: 05\_Seedling\_stand\_and\_stunted.Rmd This markdown file contains the code used to clean and prepare, explore, analyze, and summarize the seedling stand and stunted data. Preparation includes adding stand and stunted counts across subsamples to give total counts per replicate plot, and converting stand from total count to plants per hectare. Exploration and analysis are done separately for Bt and non-Bt data and include visualizing the number of plants per hectare and stunted plant counts with histograms and boxplots and analyzing treatment effect on the number of plants per hectare and stunted counts using linear mixed effects models. Model checking and post-hoc tests are performed. Means and standard errors are generated. ### File: 06\_Seedling\_damage\_area.Rmd This markdown file contains the code used to clean and prepare, explore, analyze, and summarize the seedling insect injury area data (the area per seedling that insects removed during feeding). Preparation includes calculating the mean area removed per injured plant across subsamples to give a mean injury area per replicate plot. Exploration and analysis are done separately for Bt and non-Bt data and include visualizing the injury area with histograms and boxplots and analyzing treatment effect on injury using linear mixed effects models. Model checking and post-hoc tests are performed. Means and standard errors are generated. ### File: 07\_Whorl\_damage.Rmd This markdown file contains the code used to clean and prepare, explore, analyze, and summarize mid-season insect injury. The markdown is divided into exploration and analysis of the 2020 data (incidence and severity) and the 2021 & 2022 data (only incidence). For all years of incidence data, preparation includes adding the counts of injured plants across subsamples to generate the total number of injured plants per replicate plot. For 2020 severity data, preparation includes adding across subsamples to generate a total damage area per replicate plot, then dividing by the number of plants sampled to give the mean damage area per replicate plot. Exploration and analysis are done separately for Bt and non-Bt data and include visualizing the damage incidence and severity with histograms and boxplots, and analyzing treatment effect on damage incidence and severity using linear mixed effects models. Model checking and post-hoc tests are performed. Means and standard errors are generated. ### File: 08\_Ear\_incidence.Rmd This markdown file contains the code used to clean and prepare, explore, analyze, and summarize insect injury incidence in approximately the soft-dough ear stage. Preparation includes adding counts of injured ears in each of three insect categories (caterpillar, stinkbug, and sap beetle) across subsamples to give a total injury count per replicate plot. Exploration and analysis are done separately for Bt and non-Bt data and include visualizing the number of injured ears in each category with histograms and boxplots and analyzing treatment effect on the number of injured ears in each category with linear mixed effects models. Model checking and post-hoc tests are performed. Means and standard errors are generated. ### File: 09\_Ear\_severity.Rmd This markdown file contains the code used to clean and prepare, explore, analyze, and summarize insect injury severity in approximately the soft-dough ear stage. Preparation includes calculating the average injury area in three insect categories (caterpillar, stinkbug, and sap beetle) across plants and subsamples to give the mean injury area per replicate plot. Exploration and analysis are done separately for Bt and non-Bt data and include visualizing the injury area in each category with histograms and boxplots and analyzing treatment effect on the injury area in each category with linear mixed effects models. Model checking and post-hoc tests are performed. Means and standard errors are generated. ### File: 10\_Yield.Rmd This markdown file contains the code used to clean and prepare, explore, analyze, and summarize corn yield data (kg/ha). Preparation includes removing missing values where there was a harvest error. Exploration and analysis are done separately for Bt and non-Bt data and include visualizing yield  with histograms and boxplots and analyzing treatment effect on yield with linear mixed effects models. Model checking and post-hoc tests are performed. Means and standard errors are generated. ### File: 11\_Final\_stand\_and\_stunted.Rmd This markdown file contains the code used to clean and prepare, explore, analyze, and summarize the stand and stunted data collected at the end of the season prior to harvest. Preparation includes adding stand and stunted counts across subsamples to give total counts per replicate plot, and converting stand from total count to plants per hectare. Exploration and analysis are done separately for Bt and non-Bt data and include visualizing the number of plants per hectare and stunted plant counts with histograms and boxplots and analyzing treatment effect on the number of plants per hectare and stunted counts using linear mixed effects models. Model checking and post-hoc tests are performed. Means and standard errors are generated.