ABSTRACT EnlistTM technology is a new trait on soybean and corn conferring tolerance to auxinic-type (2,4-D choline) and graminicides (aryloxyphenoxypropionates – FOPs) herbicides. However, the occurrence of volunteer corn tolerant to 2,4-D and FOPs can become a significant weed on soybean cropping systems, affecting the crop yield and reducing seed quality. This research aimed to evaluate herbicides to EnlistTM volunteer corn control and their effects on plant development, crop yield, and physiological seed quality of EnlistTM soybean. Field experiment was performed in a complete randomized block experimental design with four replicates, using a density of 10 plants·m-2 of EnlistTM volunteer corn. Treatments consisted of herbicides applied at 3-4-leaves stage of volunteer corn with haloxyfop-P-methyl, clethodim, pinoxaden, cloransulam-methyl and imazethapyr regarding to a control with and without volunteer corn. The development and yield components of EnlistTM soybean were evaluated and physiological seed testing performed on soybean’s seeds. Clethodim controlled EnlistTM volunteer corn, whereas haloxyfop-P-methyl, pinoxaden, and cloransulam-methyl showed insufficient control levels (30-35%) at 30 days after spray. Imazethapyr exhibited 84% of control of EnlistTM volunteer corn and injured the EnlistTM soybean, affecting its seed viability. EnlistTM volunteer corn interferences negatively the soybean crop yield, yield components, and affects the plant development pattern.

Abstract Background: Plants synthesize compounds of specialized metabolism to defend themselves against biotic and abiotic stresses. These compounds could be used as models for pesticide development. Among the species that have not yet been studied for the potential to produce active compounds is the kidney leaf mud plantain (Heteranthera reniformis). Objective: The goal was to evaluate the effect of hexanic, ethyl acetate and methanolic extracts of H. reniformis leaves on cress (Lepidium sativum) seed germination to determine which one have the highest biological activity; and to evaluate different concentrations of extract with the highest biological activity on lettuce (Lactuca sativa), barnyard grass (Echinochloasp.) and giant arrowhead (Sagittaria montevidensis) germination. Methods: The seeds were placed on petri dishes containing two sheets of germitest paper, and after the application of the extract, they were sealed and placed in growth chambers with controlled temperature and photoperiod. The variables analyzed were 1st and 2nd germination count, germination speed index and length of the aerial part and roots. Results: The ethyl acetate extract provided greater phytotoxicity on cress than the other extracts. In general, the highest concentration of ethyl acetate extract was the most efficient in reducing variables for all species. Conclusions: The ethyl acetate extract of H. reniformis presents inhibitory activity on the seeds of cress, lettuce, giant arrowhead and barnyard grass, but this activity was dependent on the concentration of the extract and the species studied. H. reniformis synthesizes compounds with phytotoxic activity and purification of extracts is required to isolate, identify and characterize the action mechanism of the compounds with herbicide activity, so that in the future these can be used as models for the development of herbicides.