Combining biological control approaches for managing insect crop pests in the field can generate interactive effects

Abstract

Abstract With the loss of effective chemical controls of crop pests, a move towards biological controls is a way to future‐proof our agricultural system. Floral field margins have shown successes in reducing crop pests, though the effect may not be precise enough to control infestations in commercial crops. Entomopathogenic nematodes (EPNs) may provide a more species‐ and time‐specific control and combining these methods may have synergy. Three in‐field vegetation margins, divided into four plots each (two floral and two grass), were established in March 2022. Three strips of sprouting broccoli were planted parallel in April, May and June. Each strip had a split‐plot design, with eight replicates of four nematode treatments placed alongside each floral/grass plot: Steinernema carpocapsae, S. feltiae and Heterorhabditis bacteriophora and a nematode‐free control. Pest pressure was assessed using adult counts. Assessments of crop yield and crop damage associated specifically with the swede smidge (Contarinia nasturtii) were also made. It was found that utilising a combination of control measures was successful in controlling a wider range of pests, though the success of each control method was highly dependent on the time of crop plantings. Field margins had a significant influence on crop damage associated with the swede midge. The EPN H. bacteriophora was an effective control method for the cabbage stem flea beetle and the swede midge, as well as reducing crop damage and yield loss. Field margins and EPNs combined have an interactive effect on crop yield, highlighting the need for control methods to be tested in combination in future integrated pest management research to accurately understand their effects within an integrated system.