Influence of host plant variety and pest management practices on diamondback moth abundance and parasitism in Florida

The diamondback moth (DBM), Plutella xylostella (Lepidoptera: Plutellidae), poses significant challenges to Brassica crop production globally, especially in Florida, where its year-round cultivation promotes persistent pest populations. This study evaluated the impact of host plant variety (green cabbage, red cabbage, Napa cabbage, collards) and pest management strategies (chemical, biological, untreated controls) on DBM abundance and parasitism rates in Florida over two consecutive years (2023–2024). Field trials assessed DBM larvae and pupae populations, plant weight, and parasitism levels across three sampling intervals (3, 6, and 9 weeks post-planting). Results revealed significant differences in DBM abundance influenced by host plant variety, sampling time, and pest management strategy. Napa cabbage consistently showed the lowest DBM infestation, suggesting inherent resistance traits. Chemical treatments significantly reduced DBM populations compared to biological and untreated controls across most sampling periods, yet biopesticides still effectively suppressed DBM, enhancing parasitoid activity and potentially reducing environmental impact. Parasitism rates varied significantly by year and treatment, with biological controls typically resulting in higher parasitoid effectiveness compared to chemical treatments. These findings highlight the potential of integrating host plant resistance and biopesticides into sustainable IPM strategies, aiming to mitigate DBM infestations while minimizing reliance on chemical insecticides. This study provides practical insights into optimizing IPM approaches for effective DBM management in subtropical agricultural systems.