Weed species and biomass on pineapple culture under five weed control methods

Abstract

Weeds reduce pineapple yield, and better knowledge about their dynamic contributes to improve theircontrol. At FEPAGRO, Maquiné, RS, one field assay was carried out in randomized blocks, with five replications andfive treatments: T1-W=Weeding; T2-G=Glyphosate; T3-D=Diuron; T4-D+G=Diuron+Glyphosate; T5-A+S=Atrazine+Simazine. In Mar./05, before planting, 40 spontaneous species were identified. In Aug. and Dec./05 thenumber of species and fresh biomass of the weeds were evaluated. In Aug., T4-D+G presented higher biomass andnumber of species, and the inverse was observed for T2-G. In Dec./05, it was observed: higher number of species in theT3-D; higher biomass in T5-A+S; and the lowest values of both variables in T2-G. and in Dec. D. horizontalis, E. planna,P. urvillei, B. plantaginea and C. juncea produced 71,7% of the biomass. Still in Aug., the predominant weeds were: L.multiflorum in T1-W; Gamochaeta sp. in T2-G; H. brasiliensis and P. urvillei in T3-D and T4-D+G; P. paniculatum in T5-A+S. In Dec., the weeds were: C. dactylon and H. decumbens in T1-W; Ipomoea sp. in T2-G; species of all treatmentsin T3-D and T4-D+G; and D. horizontalis and E. planna in T5-A+S. In Mar./05, 25% of the species were grasses, andin Aug. and. Dec./05, respectively, 58% and 78% of the total biomass was produced by grasses. This indicates that, tocontrol weeds in pineapple crop with herbicides, they must be efficient against grasses.