Population Monitoring and Analysis of the Main Pests of Cruciferous Vegetables in Shenzhen

The monitoring results revealed distinct temporal patterns in pest occurrence across the three vegetable gardens. Spodoptera litura maintained year-round activity in Shenzhen, with a primary outbreak peak from late April to mid-June and a secondary peak between mid-September and mid-October. In contrast, Spodoptera exigua exhibited significant spatial heterogeneity among monitoring sites, though sharing similar bimodal patterns characterized by a primary outbreak period（late April to late June）and a secondary peak phase（mid-September to mid-October). Plutella xylostella demonstrated relatively synchronized population dynamics across all sites, featuring two prolonged outbreak windows: an initial phase spanning early January to late June, followed by a second intensive period from late September to mid-December. Similarly, Phyllotreta striolata showed consistent inter-site distributions with triphasic emergence patterns: a minor early-season peak（mid-to-late February), a dominant outbreak phase（early May to mid-June), and a sustained late-season resurgence from early October through mid-December. These temporally stratified infestation profiles underscore the necessity for seasonally adaptive management strategies tailored to each pest's specific population dynamics.