Abstract: By using inverted ‘W’ sampling method, a field survey was conducted to study the seasonal dynamics of weed community in 32 plots of 5 cities in Pearl River Delta Region. The weed community was mainly consisted of Kyllinga brevifolia + Desmodium triflorum + Cynodon dactylon + Asiatic pennywort  in spring, K. brevifolia + D. triflorum + Cyperus rotundus + Hedyotis corymbosa in summer, K. brevifolia + D. triflorum+ H. corymbosa + C. dactylon in autumn, and A. Pennywort + K. brevifolia + Hydrocotyle sibthorpoioides + D. triflorum  in winter. The analysis of the weed niches in different seasons based on improved Levins niche breadth index and Pianka niche overlap index showed that most weeds had a niche breadth of < 0.5, and the weeds having a niche breadth of >0.5 included K. brevifolia (in four seasons), D. triflorum (in autumn), C. dactylon (in spring), and Oxalis pescaprae (in spring). For the dominant weeds, their niche overlap indices >0.60 were appeared most in spring and least in winter, and the maximum was appeared in summer, being 0.85 between H. sibthorpoioides and Lindernia crustacean, and Hedyotis diffusa and Ophioglossum vulgatum.

Key words: Pest mites, Damage index, Typhlodromus bambusae, Outbreaks