The development of dicamba-resistant cotton and soybean cultivars has created great concern about the potential off-target movement of dicamba onto sensitive species, including broadleaf crops. Peanut is often grown in close proximity to cotton and soybean. Therefore, field studies were conducted during 2012 and 2013 at Plains, Ty Ty, and Attapulgus, GA to evaluate peanut response to rates of dicamba (35, 70, 140, 280, and 560 g ae ha 21 ) applied at preemergence (PRE), 10, 20, or 30 d after planting (DAP) corresponding to PRE, V2, V3, and V5 peanut growth stages, respectively. Nontreated controls were included for comparison. As dicamba rate increased, both peanut injury and peanut yield loss increased. Peanut response to dicamba was fit to log-logistic regression models for injury and linear regression models for yield loss. Peanut injury increased with rate of dicamba, but was variable among the locations. A general trend was that peanut plants became more sensitive to dicamba injury as plants approached reproductive stage, as evidenced through a declining linear relationship between I 50 values (i.e. rate of dicamba that elicits a 50% crop response) and timing of application. PRE applications of dicamba had I 50 values that ranged from 125 to 323 g ha 21 of dicamba, while I 50 values were 44 to 48 g ha 21 of dicamba at the V5 peanut growth stage. There was a linear relationship between peanut yield and dicamba rate, with 560 g ha 21 causing maximum yield losses ranging from 0 to 86% when applied PRE, 24 to 82% when applied at V2 growth stage, 30 to 95% when applied at V3 growth stage, and 45 to 88% when applied at V5 growth stage. Across all treatments and locations, there was also a negative linear relationship between peanut yield and peanut crop injury, with a decline of 8.5% yield for every 10% increase in crop injury. Growers and their consultants/extension agents can use this peanut injury data to predict potential peanut yield loss from sprayer contamination or off-target movement of dicamba.
The development of 2,4-D-resistant cotton and soybean cultivars has created great concern about the potential off-target movement of 2,4-D onto sensitive broadleaf crops. Peanut is often grown in close proximity to cotton and soybean. Therefore, field studies were conducted during 2012 and 2013 at Plains, Ty Ty, and Attapulgus, GA to evaluate peanut response to 2,4-D at 67, 133, 266, 533, and 1066 g ae ha À1 applied at preemergence (PRE), 10, 20, or 30 d after planting (DAP), corresponding to PRE, V2, V3, and V5 peanut growth stages. Nontreated controls (NTC) were included for comparison. Treatment timing by rate interactions were significant (P , 0.0001). As 2,4-D rate increased peanut injury increased. There was variation in yield loss response dependent on peanut growth stage at application timing. Peanut that was treated preemergence and at the V2 growth stage did not have yield loss at any of the 2,4-D evaluated rates (67 to 1066 g ha À1 ) relative to the NTC. When peanut was treated at V3 and V5 growth stages with 2,4-D, injury estimates were 5 to 32% from the 67 to 1066 g ha À1 rates respectively, and peanut canopy diameter was stunted 5 to 35% at the same rates. The resulting peanut yield loss was 23 and 36% from 533 and 1066 g ha À1 of 2,4-D applied at V3 and V5 growth stages; in part due to reproductive growth being initiated during that time-frame and peanut had less time to recuperate before harvest. Linear regression models were used to evaluate peanut injury and peanut yield results. Significant correlations were established for V3 and V5 treatments between injury and yield, injury and canopy diameter, and canopy diameter and yield (P , 0.0001), with correlation coefficients of À 0.48, À 0.76, and 0.51, respectively. Growers and extension agents will be able to use these peanut injury estimates and canopy diameter data to make improved predictions of potential peanut yield loss where off-target movement of 2,4-D or sprayer contamination has occurred.
Giant miscanthus is under consideration as a biofuel crop in the United States; however, there is little information on weed management for the establishment and survival of this crop. Therefore, greenhouse and field studies using ornamental pots were conducted in summer 2011 at Tifton, GA, with the objective of screening potential PPI, PRE, and POST herbicides and herbicide combinations for giant miscanthus when establishing from vegetative rhizomes. For the POST treatments, giant miscanthus was established from rhizomes in 7.6-L containers in the field and treated with 27 POST herbicides to evaluate efficacy. Thifensulfuron, metsulfuron, tribenuron, chlorimuron, halosulfuron, rimsulfuron, cloransulam, pinoxaden, bentazon, and metribuzin did not significantly lower shoot height, reduce shoot dry weight, or increase injury compared with nontreated control (NTC) when evaluated at 4 wk after treatment. Nicosulfuron, trifloxysulfuron, sulfometuron, clodinafop, fluazifop, and pyrithiobac caused the greatest injury, reduced plant height, and reduced dry weights compared with the NTC. Sethoxydim, diclofop, flumioxazin, imazamox, imazapic, and imazethapyr decreased plant heights or resulted in increased injury. PPI and PRE treatments included 21 herbicides and herbicide combinations applied at two rates. Results indicated that most treatments containing atrazine, metribuzin, pendimethalin, acetochlor, metolachlor, and mesotrione did not injure or stunt growth; however, EPTC at 4.5 kg ai ha−1 significantly reduced height and dry weight and oxadiazon resulted in greater injury compared with NTC at both rates. These results indicate that PPI, PRE, and POST herbicides can be utilized for establishment of giant miscanthus from vegetative rhizomes. Considering the invasive potential of giant miscanthus, several POST herbicides evaluated in this study such as fluazifop, pyrithiobac, and sulfometuron may be viable options to control this species if it becomes invasive.
The development of dicamba-resistant cotton and soybean cultivars has created great concern about the potential off-target movement of dicamba onto sensitive broadleaf crops. Peanut is often grown in close proximity to cotton and soybean. Therefore, field studies were conducted during 2012 and 2013 at Plains, Ty Ty, and Attapulgus, GA to evaluate peanut response to dicamba rates 35, 70, 140, 280, and 560 g ae ha-1 applied at preemergence (PRE), 10, 20, or 30 d after planting (DAP) corresponding to PRE, V2, V3, and V5 peanut growth stages, respectively. Nontreated controls were included for comparison. Location by rate (P < 0.0002) and location by treatment timing (P < 0.004) interactions were significant. As dicamba rate increased peanut injury and yield loss increased. There was variation in peanut response by location after PRE treatments. Plains peanut was injured less among locations, possibly due to the Greenville soil there having higher organic matter and clay contents at 3.8 and 30%, respectively. Soil texture and other environmental factors can affect the extent of injury that occurs to peanut from dicamba exposure. When dicamba was applied at the V5 peanut growth stage, peanut was at 25% bloom, so a reduction in yield occurred, in part, from injury during that sensitive growth stage and from peanut having less time to recover before harvest. Dicamba at 35 g ha-1 applied to V5 peanut in Attapulgus had 33% injury, 42% canopy diameter stunting, and 45% yield loss as compared to the NTC. Linear regression and log-logistic regression models were used to evaluate peanut yield and injury data. There were significant correlations between peanut injury at 20 DAT and peanut yield as % NTC, injury and canopy diameter at 20 DAT as % NTC, and canopy diameter and yield (P < 0.01), with correlation coefficients of -0.57 to -0.96, -0.69 to -0.91, and 0.37 to 0.87, respectively. Growers and extension agents will be able to use peanut injury estimate and canopy diameter data to make improved predictions of potential peanut yield loss where off-target movement of Powered by Editorial Manager® and ProduXion Manager® from Aries Systems Corporation dicamba or sprayer contamination occurred. Main DocumentClick here to download Main Document: Webster edit -The effect of dicamba on peanut when applied during vegetative growth stages.do ABSTRACT 6The development of dicamba-resistant cotton and soybean cultivars has created great concern 7 about the potential off-target movement of dicamba onto sensitive species, including broadleaf 8 crops. Peanut is often grown in close proximity to cotton and soybean. Therefore, field studies 9 were conducted during
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