Efficacy of Imazapic in Controlling the Germination Fluxes of Rottboellia cochinchinensis (Lour.) Clayton Under Different Rainfall Levels and Sugarcane Straw Amounts

The weeds of the species Rottboellia cochinchinensis (Lour.) Clayton (camalote grass) are highly aggressive in bush competition for sugarcane crops, and these species are increasing their infestations in the state of Mato Grosso do Sul, generating impacts on the development of sugarcane plantations and reducing productivity and longevity. The objective of this study was to evaluate the efficacy of the herbicide imazapic in pre-emergence control of the species R. cochinchinensis when applied under conditions with and without sugarcane straw and in different simulations of rainfall. The experiment was conducted in a greenhouse in a completely randomized design. A 2 × 2 × 2 triple factorial design was used, consisting of 2 doses of the herbicide imazapic (105 and 147 g ai ha⁻¹), 2 amounts of straw (0 and 10 t ha⁻¹) and 2 rainfall simulations (10 and 30 mm). With 4 replicates and 4 controls, this factorial being isolated for two soil types (clayey and sandy) and in two germination flows (F1 and F2). The rainfall factor always resulted in higher control performances with the smallest simulated volume of 10 mm, and the amount of straw factor influenced the effectiveness of the control, both in sandy and clayey soils. The highest dose (147 g ai ha⁻¹) showed better control efficacy in clayey soils. The herbicide imazapic showed excellent control until the end of the second flush, with an average dry mass reduction of 92% for R. cochinchinensis.