Abstract
This work was conducted with the objective to determine Euphorbia heterophylla control with fomesafen in association with surfactants applied in pre-emergence, in substrates and soils with different characteristics. Three studies were carried out in pots, conducted in greenhouse, in a completely randomized experimental design. The first two studies consisted of investigating the efficacy of pre-emergence combinations of fomesafen and surfactant in the control of E. heterophylla, applied on different substrates (Study 1) and soils (Study 2) with different textural classes. Study 3 was carried out to evaluate the effect of fomesafen, applied in pre-emergence and in combination with adjuvants with different HLB's (hydrophilic-lipophilic balances). The herbicide efficacy on E. heterophylla and plant shoot dry mass were evaluated. The association of adjuvant to fomesafen, in pre-emergence, reduced plant growth in the different substrates and soils. The fomesafen response was influenced by the addition of surfactants with different HLB's. The increase in organic matter content in substrates or soil was related to the decrease of the effect of the surfactants on the control of E. heterophylla with fomesafen, or the effect was only manifested in higher herbicide dosages. Fomesafen associated with surfactant with HLB of 8.6 provided the highest levels of weed control.
Highlights
The species Euphorbia heterophylla, commonly known as wild poinsettia, is a widely disseminated dicotyledon weed in Brazil, which has a high competitive ability with crop plants (Voll et al, 2002)
The increase in organic matter content in substrates or soil was related to the decrease of the effect of the surfactants on the control of E. heterophylla with fomesafen, or the effect was only manifested in higher herbicide dosages
Experiment 3 have assessed the effect of surfactants with different hydrophilic-lipophilic balances (HLB's) associated with fomesafen sprayed in pre-emergence for weed control
Summary
The species Euphorbia heterophylla, commonly known as wild poinsettia, is a widely disseminated dicotyledon weed in Brazil, which has a high competitive ability with crop plants (Voll et al, 2002). Herbicides from several mechanisms of action are used to control E. heterophylla. In soybean and bean crops, this herbicide is used for the early post-emergence control of broad-leaved weeds, such as wild poinsettia (E. heterophylla), pigweed (Amaranthus deflexus, A. viridis, A. hydridus), morning glory (Ipomoea aristolochiifolia, I. purpurea), hairy beggarticks (Bidens pilosa), among others (BRASIL, 2019). Adjuvants are commonly used to increase the herbicide control efficacy over weeds. The use of adjuvants aims to facilitate the absorption of the pesticide by the plant, to increase the efficacy of the compound, or to reduce the risks of pesticide use. Surfactants are agricultural adjuvants classified according to their function, in this case as leaf surface active agents
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