Pests and Planting Dates APRES

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Influence of Planting Date on Peanut Response to Injury from Thrips and Herbicides.

M.D. INMAN*, D.L. JORDAN, P.D. JOHNSON, R.L. BRANDENBURG, and B.B. SHEW, North Carolina State University, Raleigh, NC 27695.

Early season control of weeds and thrips (Franklienelia spp.) is important to maximize yield of peanut in North Carolina. In one experiment conducted during 2013 and 2014, the influence of planting date (the cultivar Bailey planted approximately May 4, May 18, and May 28) on peanut injury from thrips feeding and pod yield following in-furrow and foliar application of insecticides (phorate and acephate, respectively) was determined. In a second experiment during these years with the same cultivar and planting dates, treatments included non-treated seed and seed treated with standard fungicide both with and without phorate applied in the seed furrow. Peanut stand, thrips injury, and pod yield were recorded. In a final experiment during 2013 and 2014 with the planting dates and cultivar described above, visible peanut injury and pod yield were determined when flumioxazin (107 and 214 g ai/ha) and flumioxazin plus pyroxasulfone (70 plus 89 g ai/ha and 140 plus 179 g/ha) were applied immediately after planting when either no insecticide was applied at planting or phorate (1.1 kg ai/ha) was applied in the seed furrow. In this experiment, visible estimates of percent injury were recorded 2, 3, and 4 weeks after peanut emergence.

A range of main affects and interactions were noted in all three experiments. Thrips injury was higher during 2013 than 2014 in most instances. When comparing thrips injury in absence of insecticide during 2013, higher injury was noted with early and late-planted peanut compared with peanut planted in mid-May. During 2014, injury was similar for early and mid-May plantings with injury during these dates higher than planting in late-May. Acephate increased yield regardless of phorate application or planting date during 2013 but not during 2014. Phorate increased yield during both years regardless of acephate application or planting date. Less peanut stand and more injury from thrips was noted when the fungicide seed treatment was not included. Yield was higher when phorate was applied regardless of seed treatment. Irrespective of phorate application, yield increased when seed was treated regardless of planting date. Visible injury and pod yield were affected by the interaction of year and herbicide. Response to herbicides and phorate was independent. Injury was affected by planting date with increased injury across all evaluations observed when rainfall occurred within 7 days after application. During these years significant rainfall occurred shortly after planting on May 28 as peanut emerged but was minimal following the first two planting dates. Regardless of herbicide or herbicide rate, greater injury associated with herbicide effects and stunting from thrips feeding was noted in absence of phorate compared with phorate applied in the seed furrow. Injury varied across years for herbicide treatments but was generally greater when higher rates of herbicides were applied. The higher rates of herbicides reduced yield compared with the standard rate but there was no difference in yield when comparing flumioxazin or flumioxazin plus pyroxasulfone. Although these data suggest that flumioxazin plus pyroxasulfone could be an effective alternative to flumiozaxin alone based on peanut response, other research has shown elevated injury from flumioxazin plus pyroxasulfone compared with flumioxazin and may limit the possibility of use in peanut.

Results from these experiments indicate that peanut response to pesticides used to control thrips, seedling disease, and weeds will generally be the same irrespective of planting date. While there were some interactions of treatment factors with planting date, the magnitude of these interactions was relatively minor compared with response due to main affects. The planting dates evaluated in these experiments are within the recommended timings for peanut grown in North Carolina.

Article first appeared as North Carolina Peanut Note (PNNC-2015-017)