2,4-Dichlorophenoxyacetic acid (2,4-D) is a systemic broadleaf herbicide that is often formulated as an ester.  However, the potential volatility of the ester formulation may result in vapor movement and sensitive plant injury outside of  field borders.  The objective for this work is to design a microcapsule formulation for the 2,4-D ester that offers comparable or better efficacy than the less volatile amine salt formulations of 2,4-D while reducing the potential for off-target movement via vapor transport.  Microcapsules of 2,4-D ethylhexyl ester (2,4-D EHE), with different particle size and shell thickness, have been developed for the purpose of reducing the net ester volatility.  The thermal gravimetric analysis (TGA) method was used to estimate ester release rates from the microcapsules.  Observed release rates positively correlated with the green house volatility bioassay observations for sensitive plant species (grapes and tomatoes).  TGA and bio-assay results suggest capsules having a mean diameter of 8 �m and 100 nm shell thickness reduced the ester volatility by~50% while maintaining efficacy similar to the emulsifiable concentrates (EC) formulations.  Capsules with 3 �m size and 100 nm shell thickness reduced volatility similar to the 2,4-D dimethylamine (DMA) formulations and displayed efficacy similar to that of 2,4-D DMA.

2,4-D ethylhexyl ester formulation with reduced volatility from microencapsulation

246th National Meeting (2013)

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