David L. Jordan

Response of the Peanut (Arachis hypogaea L.) Cultivar Gregory to Interactions of Digging Date and Disease Management

Digging date can have a major impact on pod yield, market grade characteristics, and economic return of peanut (Arachis hypogaea L.) and can be influenced by environmental conditions and disease management. In 17 experiments from 2003 to 2012, economic return of peanut was determined over 5 digging dates spaced 1 week apart beginning in early to mid-September through mid-October. Linear, quadratic, and cubic relationships for economic return versus days after peanut emergence were observed in 3, 6, and 4 experiments, respectively, with no response to digging date observed in 4 experiments. In a second experiment from 2005 to 2012, relationships among canopy defoliation and economic return for peanut at 3 digging dates with 3 fungicide regimes were variable, although increasing the number of fungicide sprays decreased canopy defoliation and increased economic return for later digging dates. Applying a single late-season spray of fungicide as a rescue treatment reduced canopy defoliation in 4 of 8 years and affected economic value in 2 of 8 years.

Influence of Application Variables on Peanut (Arachis hypogaea L.) Response to Prohexadione Calcium

Prohexadione calcium retards peanut vegetative vine growth, improves row visibility, and potentially reduces pod shed, thus increasing pod yield compared with non-treated peanut. Although prohexadione calcium has been registered for use in peanut for the past decade, practitioners continue to express a range of questions about use including banded application, compatibility with other agrichemcials, and interactions of application rate and timing. In experiments over multiple years, applying prohexadione calcium to lateral branches only of peanut increased row visibility compared with banded applications over main stems or broadcast applications over the entire peanut canopy. Similarly, when using different spray nozzle configurations, greater row visibility was noted when the highest rate of prohexadione calcium was applied over lateral branches compared with broadcast applications of a uniform rate across all spray nozzles or when the highest rate was delivered to main stems. Delaying the first of two sequential applications of prohexadione calcium 1 wk after 50% row closure resulted in reduced row visibility regardless of application rate when compared with sequential applications initiated at 50% row closure. Applying prohexadione calcium within 2 to 3 wks prior to digging and vine inversion resulted in minor increases in improved row visibility and did not affect pod yield. Efficacy of prohexadione calcium was not affected by tank mixing with pyraclostrobin or 2,4-DB.