Trends in invasive root maggots (Diptera: Anthomyiidae) and prospects of frass fertilizer as a biorational control strategy

Root maggots pose a growing global threat to food security, causing potential crop losses of up to 100 %, prompting the search for innovative and sustainable management strategies. In this review, we examine the global distribution of root maggots, evaluate the current management strategies and their effectiveness, and explore the potential of insect frass fertilizer as a novel, cost-effective, and multipurpose soil amendment for root maggot control. We report a wide distribution of Delia species in over 123 countries globally, with geographical specific distribution of individual species. Species such as D. radicum, D. planipalpis, D. floralis and D. antiqua strictly occur in Palaearctic and Nearctic regions whereas D. steiniella, D. flavibasis, D. arambuorgi and D. coarctata were restricted to the tropical climate of Sub-Saharan Africa. Notably, D. platura was the most widely distributed species, occurring across all bioregions. Furthermore, crop damage and yield loss were strongly influenced by factors such as soil type, climatic conditions, crop variety, cropping season, and the management approach. Despite recent advancements in integrated pest management, farmers still favour pesticides, which does not provide any advantage for long-term pest control. We present insect frass fertilizer as a promising alternative strategy for managing root maggots by inducing systemic resistance in plants, enhancing natural enemy populations, and exerting direct contacticidal effects. This information is essential for fostering cross-disciplinary collaboration among farmers, researchers, and policymakers, forming the basis for sustainable root maggot control, improved food security, and enhanced ecosystem resilience.