Evaluation of New Prohexadione Calcium Formulation on Vine Growth Suppression and Yield of Peanut (Arachis hypogaea L.) in Georgia

Prohexadione calcium is a plant growth regulator used to reduce vegetative growth and increase pod yield in peanut (Arachis hypogaea L.). Although historically formulated as a water dispersible granule (WDG), a new oil dispersion formulation (OD) of prohexadione calcium was labelled for use in peanut in 2024. Large plot experiments were conducted in Tifton, Georgia in 2021 and 2022 to evaluate the effects of prohexadione calcium OD at multiple rates on peanut vine growth suppression, Rhizoctonia solani incidence, yield, and return on investment. Prohexadione calcium OD was applied on the cultivar Georgia-12Y at 140 g ai/ha, 105 g ai/ha, and 70 g ai/ha. Prohexadione calcium WDG was applied at the recommended rate of 105 g ai/ha, and a non-treated control was included for comparison. Initial applications were made when 50% of the lateral vines were touching in adjacent rows and again 14 days later. The OD formulation regardless of rate significantly reduced main stem height and internode length compared to the non-treated control. Following the second application, prohexadione calcium OD at 105 g ai/ha continued to suppress vegetative growth for an additional four weeks compared to the WDG formulation at 105 g ai/ha. Rhizoctonia solani incidence was 9 to 15% greater in the non-treated control than all prohexadione calcium treatments. Prohexadione calcium OD at 70 g ai/ha and prohexadione calcium WDG at 105 g ai/ha significantly increased yield by 594 to 595 kg/ha over the non-treated control. Due to environmental conditions throughout 2021 and 2022, prohexadione calcium regardless of rate or formulation did not significantly increase net revenue. Therefore, prohexadione calcium OD may have increased efficacy on reducing vine growth compared to prohexadione calcium WDG, while the labelled rate of prohexadione calcium OD at 140 g ai/ha may hinder yield potential similarly to the WDG formulation as seen in other studies.