DOI: 10.5061/dryad.dfn2z355q
title: Data from: Earlier flowering of winter oilseed rape compensates for higher pest pressure in warmer climates

description: Pest abundance and timing of migration relative to the vulnerable crop
 stage influence the severity of crop damage and yield loss to insect pests
 in oilseed rape (OSR). Both abundance and timing are influenced by
 landscape composition, changes therein due to crop rotation, and
 temperature. The need for sustainable and temperature-adapted management
 strategies of OSR pests due to the environmental harm of current
 conventional practices and global warming calls for a better understanding
 of the combined effects of landscape composition and temperature on pest
 abundances, larval parasitism, crop damage and yield, but also of the role
 of crop phenology for crop damage and yield under field conditions. Here,
 29 winter OSR crops were studied along a multi-annual mean temperature
 gradient (MAT, 1981–2010) in Bavaria, Germany. We measured pest abundances
 (pollen beetles, stem weevils), crop damage (bud loss, stem tunnelling),
 pollen beetle larval parasitism and crop yield and calculated Julian dates
 of flowering from biweekly observations of growth stages. Pest abundances
 and parasitism were analysed with regard to MAT and landscape parameters
 at six scales (non-crop habitat and OSR area, change in the proportion of
 OSR area relative to the previous year; 0.6 km, and 1–5 km in 1-km steps),
 while analysis of crop damage and yield also included Julian date of
 flowering. Pollen beetle abundance was increased under higher MAT, but
 less strongly when OSR proportions were high (1-km scale) and not strongly
 reduced relative to the previous year (5-km scale), while pollen beetle
 larval parasitism was overall low but exceeded 30% (considered as
 threshold for effective natural control) occasionally under both low and
 high MAT. In contrast to abundance of adult pollen beetles, stem weevil
 larval abundance – as well as stem damage – did not respond to landscape
 composition nor MAT. Despite high abundance of adult pollen beetles under
 high MAT, crop yield was high (and the proportion of bud loss low) under
 high MAT when OSR flowered early. Our results underpin the potential of
 targeted landscape management (e.g. through regionally coordinated crop
 rotations) and timing of flowering (e.g. through cultivar choice) for
 environment-friendly and temperature-adapted pest management in winter
 OSR.
description: Winter oilseed rape plants were sampled during flowering and crop
 ripening on 29 study sites across a spatial multi-annual mean temperature
 gradient (1981-2010) in Bavaria, Germany. Flowering samples were stored at
 -20°C and samples taken during crop ripening were dried for yield
 assessment. We assessed pest abundances (adult pollen beetles, stem weevil
 larvae), pollen beetle larval parasitism, crop damage (proportion of bud
 loss and stem tunneling) and seed yield and calculated field-level Julian
 date of flowering from biweekly growth stage observations. During sampling
 at flowering, plants were cut at ground-level and were carefully bagged to
 assure that also adult pollen beetles on the plant were included in the
 sample. Adult pollen beetles on plants and inside sampling bags were
 counted. Then, all organs on the main raceme of winter oilseed rape plants
 were counted distinguishing between ‘lost buds’ (stalks without buds or
 pods and stalks carrying dead buds), broken stalks (stalk with visibly
 moist tips at the breakage due to breaking off in the frozen stage of the
 sample) and all other organs (pods, flowers, flower buds). From there, we
 calculated the proportion of ‘lost buds’ relative to all organs on the
 main raceme.  Flowers and flower buds &gt;3mm on the entire plants
 were scanned for pollen beetle larvae. Larvae &gt; 2mm were counted
 and presence-absence of black parasitoid eggs inside larvae recorded to
 calculate the proportion of parasitized pollen beetle larvae. Besides,
 stem length with diameter &gt;=5mm was measured and then cut open to
 count the number of stem weevil larvae and to measure the length of
 orange-brown-coloured pith due to the presence of stem weevil larvae.
 Proportion of stem damage was calculated as length of stem damage relative
 to stem length. To obtain seed yield values per plant, number of pods per
 ripe, air-dried plant were counted as well as the number of seeds per pod
 for 20 pods, and 400 seeds per plant were weighted. Prior to analysis,
 exclusion criteria were applied to standardize data (e.g. exclusion of
 sites for analysis when information available on less than three plants
 per site). For details we refer to the manuscript.
description: Fricke et al OSR data processing (.R file)
 This R-script contains all code needed to process data in
 preparation for data analysis, except for data standardization that is
 included in the R-script on data analysis.
 Fricke_et_al_OSR_data_processing.R Fricke et
 al OSR data analysis (.R file) This R-script contains
 the code used to standardize data (e.g. applying exclusion criteria) and
 to analyse pest abundance, parasitism, and crop damage and yield data
 including generalized linear mixed effect models and multimodel
 averaging. Fricke_et_al_OSR_data_analysis.R Fricke et al OSR data processing Raw data on measures per plant, plant organ and pod as well as biweekly growth stage observations and general site information were processed using the accompanying R-script to obtain proportions of bud loss on the main raceme, proportions of parasitized pollen beetle larvae, proportions of stem damage, seed yield per plant and calculated Julian dates of flowering, and complete data sets for analysis. The resulting processed data were used in the R-script on data analysis. Fricke_et_al_flowering_sample_data_per_plant_raw.csv Metadata_Fricke_et_al_flowering_sample_data_per_plant_raw.txt Fricke_et_al_flowering_sample_data_per_plant_organ_raw.csv Metadata_Fricke_et_al_flowering_sample_data_per_plant_organ_raw.txt Fricke_et_al_yield_sample_data_per_plant_raw.csv Metadata_Fricke_et_al_yield_sample_data_per_plant_raw.txt Fricke_et_al_yield_sample_data_per_pod_raw.csv Metadata_Fricke_et_al_yield_sample_data_per_pod_raw.txt Fricke_et_al_growth_stage_data.csv Metadata_Fricke_et_al_growth_stage_data.txt Fricke_et_al_site_info_data.csv Metadata_Fricke_et_al_site_info_data.txt Fricke_et_al_flowering_sample_data_processed.csv Metadata_Fricke_et_al_flowering_sample_data_processed.txt Fricke_et_al_yield_sample_data_processed.csv Metadata_Fricke_et_al_yield_sample_data_processed.txt Fricke et al data on landscape parameters This dataframe contains the landscape variables 'proportion of non-crop area' (= forest + permanent managed grassland + semi-natural habitats; year: 2019), 'proportion of oilseed rape area' (year: 2019), 'change in oilseed rape area relative to the previous year' (year: 2019 relative to 2018) at multiple spatial scales as used in the accompanying R-script on data analysis. Fricke_et_al_landscape_data.csv Metadata_ Fricke_et_al_landscape_data.txt