Using flower strips to promote green lacewings to control cabbage insect pests

Rafael Alcalá Herrera,Mario Porcel,Belén Cotes,Marco Tasin,Nuria Agustí

doi:10.1007/s10340-021-01419-7

Abstract

Habitat management improves biological control by increasing the abundance and fitness of natural enemies through the provision of floral resources along field edges or between crops. Among the natural enemies reliant on flower resources, green lacewings often stand out due to their abundance, predation capacity and polyphagy. We evaluated the impact of tailored flower strips on the enhancement of natural enemies, especially green lacewings, in three organic cabbage (Brassica oleracea) farms in Southern Sweden. Insects were sampled from the flower strips, and cabbage pests and predators were visually recorded in the crop. In a laboratory assay, the pollen feeding preferences of Chrysoperla carnea (Stephens, 1836) were evaluated in a dual-choice test. The pollen consumed by the Chrysopidae was extracted from laboratory and field specimens, then quantified and identified. Flower strips were found to attract predators and parasitoids, whose abundance increased as flowers bloomed. Cabbage plants next to the flower strips showed lower pest infestation as compared to cabbage plant control, although no significant differences were observed in the number of predators. Chrysopidae used flower strips as feeding, reproduction and shelter sites and mainly consumed pollen from Phacelia tanacetifolia Benth. Under laboratory conditions, C. carnea showed a preference for P. tanacetifolia and Coriandrum sativum L. pollen over Borago officinalis L. and Fagopyrum esculentum Moench. We show that tailored flower strips could be an efficient tool for enhancing beneficial arthropods and should be considered in integrated pest management for cabbage crops.

Highlights

Increasing agricultural intensification has had a negative impact on the wider environment, which has led to landscape simplification, agrochemical spillover in soil and water, as well as an increasing loss of biodiversity (Conway 2000; Tilman et al 2002)
We demonstrated that flower strips in their vicinity have a positive impact on pest reduction in cabbage plants as compared to those in control blocks due to space constraints, we were forced to limit the amount of control blocks in each farm
We recorded other generalist predators in the flower strips, such as Araneae, Anthocoridae, Carabidae and Dermaptera (Cahenzli et al 2019) which may contribute to the reduction in pest populations in the vicinity of the flower strips, these generalist predators were not recorded on the cabbage plants in our study

Summary

Introduction

Increasing agricultural intensification has had a negative impact on the wider environment, which has led to landscape simplification, agrochemical spillover in soil and water, as well as an increasing loss of biodiversity (Conway 2000; Tilman et al 2002). A shift towards a more ecosystem-based approach to agriculture has been proposed (Tittonell 2014) This approach includes habitat management in order to restore functional agrobiodiversity in the agricultural landscape. This involves the introduction of non-crop vegetation with the aim of providing beneficial arthropods with shelter, overwintering sites, alternative prey and food resources (Landis et al 2000; Gurr et al 2017). As several factors may influence the success of this strategy, system-specific evaluations need to be carried out prior to implementation (Tscharntke et al 2016) Parameters such as time of flowering, synchronization with natural enemies and pest occurrence, nectar and pollen production and competition with the main crop for resources should be carefully investigated before this strategy is implemented. Flower strips should not attract or host arthropods potentially harmful to the main crop or favour intraguild predation among beneficial arthropods (Tscharntke et al 2016)

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