Submitted to: Peanut Science
Publication Type: Peer reviewed journal
Publication Acceptance Date: 11/15/2009
Publication Date: 1/2/2010
Citation: Faircloth, W.H., Prostko, E.P. 2010. Effect of imazapic and 2,4-DB on peanut seed quality, yield, grade and tomato spotted wilt incidence. Peanut Science. Vol. 37, No. 1, pp. 78-82. Interpretive Summary: Because of tomato spotted wilt virus, obtaining a uniformly emerging plant stand has become critical to the success of peanut production systems in the southeast. Several varieties (Florida MDR-98, DP-1, GA-01R) were released in the past few years which experienced significant emergence problems at the farm level. Consequently, questions have been raised about the potential effects that certain postemergence herbicides have on peanut seed quality, particularly germination and vigor. Of all the postemergence herbicides labeled for use in peanut, imazapic and 2,4-DB are the most likely suspects because they are both systemic broadleaf herbicides and widely used. Therefore, the objective of this research was to evaluate the influence of imazapic and 2,4-DB on the yield, grade, and seed quality of three peanut varieties (Georgia Green, C-99R, GA-01R). Peanut yield and grade showed differences between cultivars depending on location and year, as expected, but no relationship with herbicide was found. Research further demonstrated that differences in germination and vigor were due to intrinsic variation in the peanut cultivars, not due to the herbicides applied. Therefore, continued usage of the herbicides imazapic and 2,4-DB on peanuts grown for seed is recommended.
Technical Abstract: Many factors contribute to peanut seed quality including maturity, genetics, and agronomic management during the growing season. The effect of herbicides on current peanut cultivar seed quality (germination and vigor) has not been studied. Small-plot, irrigated field trials were conducted at 2 locations in 2005 and 2006 (Tifton, Dawson) to evaluate the influence of imazapic and 2,4-DB on tomato spotted wilt virus (TSWV) infection, yield, grade, and seed quality of three peanut varieties (Georgia Green, C-99R, GA-01R). Each peanut variety was treated with imazapic (0.07 kg ai ha-1) at either 30 or 45 days after planting (DAP) or 2,4-DB (0.28 kg ai ha-1) at either 75 or 90 DAP. Plot areas were maintained weed-free throughout the growing season. Yield and pod samples were collected using a stationary plot harvester in mid to late-September, depending on variety. Standard percent germination at 25 C and cold germination (15 C) tests were conducted by the Georgia Department of Agriculture in early-December. No variety by herbicide interaction was detected. The main effect of variety strongly influenced TSWV infection, yield, grade, germination, and vigor. There were no differences in TSWV infection between Georgia Green and C-99R at Tifton. However, both of these varieties had 45% more TSWV than GA-01R. Variety had no effect on TSWV at Dawson as TSWV infection was extremely low (mean < 1%). GA-01R yielded 5380 kg ha-1 which was greater than C-99R (4800 kg ha-1), both of which yielded greater than Georgia Green (3780 kg ha-1) at Tifton. Yield at this location closely followed TSWV infection rates. At Dawson, Georgia Green produced the highest yields (5210 kg ha-1) and C-99R produced the lowest yields (4230 kg ha-1). GA-01R graded highest at Tifton (TSMK 77%) followed by C-99R (75%) and Georgia Green (73%). At Dawson, variety had no effect on grade with mean TSMK 76%. Seed germination at Tifton was greatest with Georgia Green (93%) and lowest with GA-01R (67%). Both Georgia Green and C-99R had greater germination than GA-01R at Dawson. Cold test results mirrored standard germination results with Georgia Green having highest percent germination at both locations (88%). When compared to the non-treated, the herbicides evaluated in these studies had no effect on TSWV, grade, seed germination, and cold germination. However, the main effect of herbicide was significant for yield at the Dawson location only. A late application of 2,4-DB (95 DAP) produced higher yields than any of the imazapic treatments or 2,4-DB at 75 DAP. First-year results from this series of field studies suggest that the intrinsic differences between varieties influence TSWV infection, yield, grade, and seed germination/vigor greater than the herbicides imazapic and 2,4-DB.