Integrated control of root-feeding fly larvae infesting vegetable crops (FlyIPM) C-IPM Coordinated Integrated Pest Management in Europe Pesticide Research No. 195 March 2021 Publisher: The Danish Environmental Protection Agency Editors: Rosemary Collier, Anne-Marie Cortesero, Nicolai Meyling, Martin Hommes, Ute Vogler, Quentin Schorpp, Timea Szikora, Michael Gaffney, Tor Johansen, Richard Meadow, Stane Trdan The University of Warwick, Université de Rennes, University of Copenhagen, Julius Kuehn Institute, Agroscope CH, Teagasc Eire, Norwegian Institute of Bioeconomy Research, Norwegian University of Life Sciences, University of Ljubljana ISBN: 978-87-7038-220-5 The Danish Environmental Protection Agency publishes reports and papers about research and development projects within the environmental sector, financed by the Agency. The content of this publication do not necessarily represent the official views of the Danish Environmental Protection Agency. By publishing this report, the Danish Environmental Protection Agency expresses that the content represents an important contribution to the related discourse on Danish environmental policy. Sources must be acknowledged 2 Funded by the European Union Project information Project acronym: FlyIPM Project ID: Project title: Integrated control of root-feeding fly larvae infesting vegetable crops Project website (if https://www.agroscope.admin.ch/agroscope/en/home/topics/plant- existing): production/plant-protection/flyipm.html Start of project: 01/05/2017 End of project: 31/03/2020 35 months Duration in months: Consortium Address of the coordinator Name: Collier First name: Rosemary Telephone: +44 24 7657 5066 E-mail address: [email protected] Name of the University of Acronym of the coordinator’s Warwick coordinator’s institution: institution: Address line 1: School of Life Address line 2: Wellesbourne Campus Sciences Postal code: CV35 9EF City: Warwick Region/ State: Warwickshire Country: UK Partner Country: Institution/ Type of Functions2): Involved Contact no.: organisation institution/ in WPs: person name: organisation1): with e- mail address: 1 UK The University University PC, WPL 1,3,4,5 Prof of Warwick Rosemary Collier Rosemary.c ollier@war wick.ac.uk 2 France Institute for University WPL 1,2,3,4,5 Prof Anne- Genetics, Marie Environment Cortesero and Plant anne- Protection marie.corte sero@univ- rennes1.fr 3 Denmark University of University WPL 3,4,5 Dr Nicolai Copenhagen Meyling nvm@plen. ku.dk 4 Germany Julius Kuehn Public research P 1,3,4,5 Dr Martin Institute (JKI) centre Hommes 3 Funded by the European Union martin.ho mmes@juli us- kuehn.de Dr. Ute Vogler Ute.vogler @julius- kuehn.de Dr. Quentin Schorpp Quentin.sc horpp@juli us- kuehn.de 5 Switzerlan Agroscope Public research WPL 1,4,5 timea.sziko d centre ra@agrosc ope.admin. ch 6 Ireland Teagasc Public research P 1,3,4,5 Dr Michael centre Gaffney Michael.Ga ffney@teag asc.ie 7 Norway Norwegian Public research P 1,2,3,5 Dr Tor Institute of centre Johansen Bioeconomy Tor.Johans Research [email protected] o 8 Norway Norwegian University WPL 2,3,4,5 Dr Richard University of Meadow Life richard.me Sciences adow@nm bu.no 9 Slovenia University of University P 4,5 Prof Stane Ljubljana Trdan Stane.Trda [email protected] lj.si 1) University, Public research centre, Private research centre, Company, Other 2) PC = Project coordinator, WPL = Work package leader, WPCL = Work package co-leader, P = Participant Short description on the elaboration of the proposal (earlier projects this project is based on, involvement of end users/farmers/other stakeholders in the design of the project) The species of root fly on which this project focuses (Delia radicum, D. floralis, D. antiqua, D. platura and Chamaepsila rosae) have been researched in Europe and North America where they are economically important pests. There is a good understanding of their basic biology and ecology. A number of potential components of IPM strategies have been investigated for one or more species, but control in Europe still relies mainly on the use of insecticides. Components of IPM that have been investigated for one or more species include host plant resistance, cultural control methods, sterile 4 Funded by the European Union insect release, inundative and conservation biological control with arthropods, entomopathogenic nematodes and fungi, companion planting, intercropping, undersowing, trap crops, physical barriers and decision support (monitoring and forecasting). There is scope for refining and combining some of these approaches and for evaluating them collaboratively in different locations and cropping systems. The phenology of all species is relatively well understood. Monitoring systems have been developed for all species. Forecasting systems using weather data have been developed in the UK and Germany for P.rosae and D. radicum and have been used by the respective industries for more than 10 years. In the UK, information on pest activity is disseminated through a web site hosted by Syngenta UK and in Norway through the VIPS program developed by NIBIO and the Agricultural Extension Service. The University of Rennes (IGEPP) has been investigating the use of volatile organic compounds to manage D. radicum. They have shown that it is possible to modify oviposition behaviour under field conditions by using dispensers to release volatile chemicals that significantly decrease the numbers of eggs laid on plants. The aim is to develop a push-pull strategy combining the use of synthetic volatile compounds and attractive Brassica cultivars (used as trap crops) to control infestations. The potential for trap cropping has been demonstrated in experimental plots and this approach needs to be tested on a larger scale. This approach requires further development but there may be the potential to combine it with other components of an IPM strategy. Recent developments in molecular tools mean that the potential for identifying and studying the root- colonizing/endophytic capacity of entomopathogenic fungi (EPF) strains isolated from host-plants and understanding plant-EPF-insect interactions is improved. Several studies have demonstrated promising results by infecting D. radicum larvae with EPF under controlled conditions, particularly with Metarhizium spp. However, it remains a challenge to target the soil-dwelling larvae in the field. Many EPFs also associate with plant roots, where Metarhizium can persist and proliferate in the rhizosphere, and some fungi become endophytic in the root system. Soil drenching of EPF inoculums showed promise in greenhouse and field experiments, but such methods will be challenging to implement in an IPM strategy. Roots grown from seeds inoculated with Metarhizium remained infective to root-feeding larvae in greenhouse conditions, indicating that the roots can deliver EPF inoculum in the soil. EPFs appear to be compatible with other natural enemies e.g. parasitoids, suggesting that EPF have limited non-target effects. Furthermore, EPF inoculation may bolster the crop by promoting plant growth. While entomopathogenic nematodes (EPN) are potentially useful field-applied biocontrol agents for soil dwelling pest insects, their control potential is limited, in the main by ambient temperatures. EPN species have narrow temperature ranges over which they can effectively control pests and these vary between EPN species and strains. Currently, EPN useful for control of D. radicum are applied to coincide with oviposition in the field, which invariably is at ambient temperatures unsuitable for optimal efficacy of these agents. Research has shown that the infectivity of key nematode groups, such as the Heterorhabditidae and Steinernematidae, can be enhanced; giving potential for enhanced performance, at both optimal and sub-optimal temperatures. Enhancement can occur following low- temperature storage of EPN in water with particular combinations of temperature and duration. Improving the field performance of these agents could contribute to making them a more robust alternative to current chemical control strategies. Approaches to IPM of root flies in Europe have been considered on several occasions (e.g. paper by Finch & Collier, 2000; EPPO workshop on C. rosae 2009; EIP-AGRI Focus Group ‘Integrated Pest Management – focus on Brassica species’ 2014-2016). Key requirements identified included: reliable, cost-effective and simple monitoring and decision support systems; alternative control strategies with fewer side effects on beneficials; knowledge about alternative ways of applying treatments; better ways of presenting information to growers. Unfortunately, with the exception of some changes in the insecticide treatments applied, and greater use of physical barriers, IPM strategies used commercially to control root flies have not been enhanced in the 16 years since the paper by Finch & Collier was published and, although decision support systems have been available for a number of years, there is 5 Funded by the European Union scope for improvement. It is also timely to consider the impact of climate change on pest life-cycles in future. Reference: Finch, S. & Collier, R.H. (2000). Integrated pest management in field vegetable crops in northern Europe – with focus on two key pests. Crop Protection (19), 817-824 Outputs - results of the activities undertaken in the project Several important vegetable crops grown outdoors in temperate climates can be damaged by the root-feeding larvae of Diptera; the larvae of Delia radicum (L.) (cabbage root fly),