Surfactants increase toxicity of glyphosate and 2,4-D to Brazil pusley

Various combinations of glyphosate and 2,4-D (+/- surfactant) were evaluated for control of Brazil pusley [Richardia brasiliensis (Moq.) Gomez]. Typical 2,4-D symptoms on plants were manifested within 2 to 3 days after treatment. Application of glyphosate alone had only marginal effects (14%) on Brazil pusley, but the addition of Induce' (nonionic surfactant) significantly increased control to 83% and reduced the fresh weight by 68%. Application of LandmasterOll ora tank-mixof glyphosate + 2,4-D ( surfactants) resulted in 96% to 100% control. Treatment with 2,4-D alone, or with Induce', or L-771 (organosiliconesurfactant) resulted in84%,90%,or 100% control, respectively. Very low fresh weights of Brazil pusley were recorded when 2,4-D +Induce", or L-771, Landmaster'll ( surfactants), or the tank-mix ( surfactants) were applied. In the regrowth studies, shoot weight was greater following application of glyphosate with or without L-771 or Kinetic' (a blend of nonionic and organosilicone) than following other treatments. The fresh weight of the shoots in the regrowth study, recorded following the application of 2,4-D or Landmaster'll ( surfactants), was very low except when Kinetic' was added to Landmaster'll. No regrowth of shoots occurred following the tank-mix treatment. Similar observations were recorded for roots. Plants treated with 2,4-D did not regrow. The presence of 2,4-D in either formulation accelerated synergistic effect of the glyphosate to the target site. Therefore, 2,4-D could be used either as a component of a formulation or in a tank-mix with glyphosate to control Brazil pusley. Chemical names used: N(phosphonomethyl glycine) (glyphosate); 2,4-dicholorophenoxyacetic acid (2,4-D).