A survey was carried out on the weed populations occurring after harvest in cornfields along the São Francisco River to identify which weeds remained in the 12 municipalities spread along the river, from its headwaters down to "Tres Marias". Ageratum conyzoides L. was the only species found in all the fields surveyed. The species presenting major Importance Value Index (IVI) were: Sida glasiovi K. Schum, Conyza bonariensis (L.) Cronq, Gaya sp. Sida rhombifolia L. and Blainvillea biaristata DC., being also found in one or more places. These plants are sources of food for certain pollinating and pest predating insects. Such surveys may help to adequately choose herbicides to clean up the fields after corn harvest, avoiding improper applications of chemical products, which represent great risks of environmental pollution.
sustainable agriculture; integrated management; no-tillage system
