© The Author(s) 2018. Published by Oxford University Press on behalf of Entomological Society of America. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com. 139 Special Collection: Pulse Crop Insect Pests and Their Management Strategies Insect Pest Suppressive Soils: Buffering Pulse Cropping Systems Against Outbreaks of Sitona Weevils Heikki M. T. Hokkanen 1,2 and Ingeborg Menzler-Hokkanen 1 1 Department of Agricultural Sciences, University of Helsinki, Latokartanonkaari 5, PL 27, FIN-00014 Helsinki, Finland and 2 Corresponding author, e-mail: heikki.hokkanen@helsinki.f Subject Editor: Gadi V. P. Reddy Received 22 March 2018; Editorial decision 4 May 2018 Abstract Innovative approaches to redesigning agricultural systems are urgently needed. A crucial way of ‘ecologically intensifying’ agricultural production relies on designing cropping systems that mimic the diversity of natural ecosystems through lengthening and diversifying crop rotations and reducing tillage intensity (e.g., conservation agriculture). Minimal soil disturbance (reduced or no tillage) and permanent soil cover (mulch) combined with rotations facilitate to conserve, improve, and make more ef fcient use of natural resources. These practices not only reduce soil degradation but also contribute to sustained agricultural production including biological control of pests and diseases. Plant pathologists have for a long time studied the concept of ‘suppressive soils’ and tried to understand the mechanisms involved in plant disease suppression. We propose to expand the concept to ‘insect pest suppressive soils’, and provide concepts and data on the occurrence and importance of soil-borne insect pathogens in pest population suppression. Agricultural felds usually harbor only low numbers of benefcial insect antagonists such as entomopathogenic nematodes (EPN) and fungi (EPF), so that their role in pest population dynamics currently is negligible. Yet simple improvements or modifcations in feld and crop management can quickly increase the numbers of EPN and EPF to levels that will impact the peak pest populations. Sitona weevils are highly susceptible to common insect pathogens, and can play a key role in maintaining effective EPN and EPF levels in the feld, while being under effective control themselves. Key words: biological control, ecostacking, entomopathogenic fungi, entomopathogenic nematodes, insect antagonists We must increasingly rely on ecosystem services including biocontrol to maintain or to increase agricultural production, and at the same time, to keep it ecologically, economically, and socially sustainable (Eilenberg and Hokkanen 2006). In this process, ecosystem service providers (ESP) must be seen as critically important components in securing the long-term sustainability of agricultural production. Biodiversity at all levels has been shown to have the potential to affect the supply of ecosystem services to crops by the ESP. These affecting levels include crop plant genetic variability (Grettenberger and Tooker 2017), soil microbial assemblages (Pineda et al. 2017, Prieto et al. 2017), botanical composition in a feld (Adhikari and Reddy 2017, Balzan 2017, Schröder et al. 2017), and diversity of the agroecosystem landscape (Steingröver et al. 2010). These benefcial effects have so far not been systematically exploited in an additive or synergistic manner to provide the best possible level of pest control obtainable in a given environment. Hokkanen (2017) proposed to make full use of the pest control services accruable by stacking and conserving functional biodiversity in our cropping sys- tems—by ‘ecostacking’. Stacking implies combining the pest control services based on functional biodiversity from all levels and types. The various ESP must be fully integrated with the rest of the cropping system, including agronomic practices. One key group in this strategy is the various microbial consortia in the soil, providing invaluable eco- system services such as pest, disease, and weed control. This includes benefcial microbes either directly as components of suppressive soils, or as plant colonizers either as endophytes, or as epiphytic microbial fora (Shikano et al. 2017). Suppressive soils are well known for plant pathogenic microbes (e.g., Hornby 1983, Schlatter et al. 2017), but soils suppressive to insect pests have received practically no attention (Bell et al. 2016, Hokkanen and Menzler-Hokkanen 2017). The role of endo- and epiphytes in steering interactions between insects and plants is under intensive study, but as yet has not been utilized in crop protection (Shikano et al. 2017). The aim of this review is to encourage the development of insect pest suppressive soils (IPSS) as an integral part of sustainable pest management. A suitable frst target might be buffering the cropping system against outbreaks of the Sitona weevils, specialized on feeding on legume crops. The pea leaf weevil Sitona lineatus L. (Coleoptera: Annals of the Entomological Society of America, 111(4), 2018, 139–143 doi: 10.1093/aesa/say019 Forum Downloaded from https://academic.oup.com/aesa/article/111/4/139/5052934 by guest on 17 January 2023