Weed management in Italian rice fields

Historical information on weeds in rice in Italy dates back to 1800’s, when Giovanni Biroli (1807) reported, as biggest weed problems, the sedges Cyperus longus and Scirpus mucronatus and the barnyardgrasses, particularly Echinochloa crus-galli. At the beginning of the 1900s, Jacometti (1912) highlighted listed 133 species, remaining constant until the middle of the 1950s, when the diffusion of new techniques of rice cultivation began. In particular, the shift from transplanting to direct seeding, the abandonment of hand weeding, and the introduction of short-stature rice varieties resulted in the worsening of weed infestations. The first widespread use of herbicides was specifically aimed at controlling Alismataceae species and sedges. The tradeoff was increased dominance of grasses, especially Echinochloa. Nowadays, the Italian rice field ecosystem is notably complex and includes species which compete with rice in the paddy fields and also those present in other areas, such as levees, ditches, canals, and paths. Based on the practices adopted for their control, the major weed species in Italian rice fields can be grouped as follows: (1) Echinochloa spp.; (2) various weedy rice biotypes; (3) Heteranthera species; (4) Alismataceae, Cyperaceae (sedges) and Butomaceae species ; (5) weeds of the drill-seeded fields; and (6) other weeds of minor importance that are normally not subjected to specific interventions.