ABSTRACTyield, improve some market grade characteristics, and decrease incidence of tomato spotted wilt tospovirus Experiments were conducted from 1999 through 2002 in North(TSWV) (Baldwin and Williams, 2002;Hurt et al., 2003). Interactions of planting pattern and seeding rate with irrigation have been reported for several crops. Irrigation increased corn (Zea mays L.) yield when higher A ltering plant population and row pattern can afplant populations were established compared with lower fect crop yield, quality factors, and pest developplant populations when row pattern was held constant ment in peanut. Pod yield of bunch-type peanut was (Liang et al., 1992). In contrast, corn yield did not in-16% higher when peanut was seeded in rows spaced crease when plant population was increased in absence 46 cm apart compared with 91 cm (Norden and Lipsof irrigation (Liang et al., 1992). In soybean [Glycine comb, 1974). Duke and Alexander (1964) reported pod max (L.) Merr.], increasing plant populations and deyield that was 14% higher in narrow row plantings comcreasing row width increased yield (Lehman and Lampared with traditional wider row patterns using largebert, 1960). In cotton (Gossypium hirsutum L.), yield seeded Virginia bunch-type peanut. Spanish market increases were noted when seeding rate was increased type peanut planted in 46-cm rows yielded higher than and row spacing was decreased (Briggs et al., 1967; Heitpeanut planted in rows spaced 61, 76, 91, or 107 cm apart holt et al., 1992;Hoskinson et al., 1974). at similar in-row plant populations (Parham, 1942). Cox Determining interactions of seeding rate and planting and Reid (1965) reported that increasing plant populapattern with variables such as cultivar selection and tions by increasing in-row seeding rate or by decreasing irrigation will assist growers and their advisors in develrow width increased pod yield.oping efficient production and pest management sysAlthough the majority of peanut in the USA is seeded tems for peanut. Therefore, research was conducted to in single rows spaced 91 to 102 cm apart, research sugcompare peanut pod yield, market grade characteristics, gests that seeding peanut in standard twin row patterns and TSWV severity when peanut was seeded in various (rows spaced approximately 18 cm apart with centers planting patterns, seeding rates, and cultural practices. of these rows spaced 91 to 102 cm apart) can increase MATERIALS AND METHODS

Field studies were conducted in 1996 and 1997 to evaluate response of eight peanut cultivars to flumioxazin applied preemergence (PRE) at 71 g ai/ha. Peanut cultivars evaluated include ‘NC 12C’, ‘NC 7’, ‘VAC 92R’, ‘NC-V 11’, ‘NC 10C’, ‘AT VC 1’, ‘NC 9’, and the experimental breeding line ‘N9001OE’. Visible injury 3 wk after planting in 1996 was 3% or less regardless of cultivar. In 1997, all cultivars were injured 15 to 28% with flumioxazin PRE, except VC 1, which was injured 45%. No visible injury was observed at 5 and 9 wk after planting. Flumioxazin did not influence the incidence of early leaf spot, late leaf spot, southern stem rot, cylindrocladium black rot, or tomato spotted wilt virus. Flumioxazin did not affect percentage of extra-large kernels, sound mature kernels, other kernels, and total yield.

Germination response of slender amaranth to temperature, solution pH, moisture stress, and depth of emergence was evaluated under controlled environmental conditions. Results indicated that 30 C was the optimum constant temperature for germination. Germination of slender amaranth seed at 21 d was similar, with 35/25, 35/20, 30/25, and 30/20 alternating temperature regimes. As temperatures in alternating regimes increased, time to onset of germination decreased and rate of germination increased. Slender amaranth germination was greater with acidic than with basic pH conditions. Germination declined with increasing water stress and was completely inhibited at water potentials below −0.6 MPa. Slender amaranth emergence was greatest at depths of 0.5 to 2 cm, but some seeds emerged from as deep as 6 cm. Information gained in this study will contribute to an integrated control program for slender amaranth.

Field studies were conducted in 1996 and 1997 to evaluate response of eight peanut cultivars to diclosulam applied preplant incorporated at 36 g ai/ha in a weed-free environment. Peanut cultivars evaluated included ‘NC 12C’, ‘NC 7’, ‘VAC 92R’, ‘NC-V 11’, ‘NC 10C’, ‘AT VC 1’,‘NC 9’, and the experimental breeding line N90010E. Visible injury 3 wk after planting was less than 5% regardless of cultivar. No injury was observed at 21 d after planting. Diclosulam did not influence the incidence of early leaf spot, late leaf spot, southern stem rot, cylindrocladium black rot, or tomato spotted wilt virus. Diclosulam did not affect percentage of extra large kernels, sound mature kernels, other kernels, and yield.

Laboratory and greenhouse studies were conducted to determine the effect of temperature, pH, water stress, and planting depth on crowfootgrass germination. When treated with constant temperature, crowfootgrass germinated over a range of 15 to 40 C, with the optimum germination occurring at 30 C (42%). Onset, rate, and total germination (94%) were greatest in an alternating 20 and 35 C temperature regime. Germination decreased as pH increased, with greatest germination occurring at pH 4 and 5. Germination was reduced when seed was subjected to water stress, and no germination occurred below −0.8 mPa. Emergence was similar when seed were placed on the soil surface or buried at depths of 0.5 or 1 cm. Germination decreased with burial depth, and no seed emerged from 10 cm. These data suggest that crowfootgrass may emerge later in the season with warmer temperatures and after a precipitation event, and may emerge rapidly. These attributes could contribute to poor control later in the season by soil-applied herbicides or allow crowfootgrass to emerge after final postemergence treatments are made.

Experiments were conducted from 1999 through 2001 in North Carolina to determine peanut response under weed-free conditions to applications of postemergence herbicides. In one set of experiments, peanut tolerance to acifluorfen plus bentazon or acifluorfen plus bentazon plus 2,4-DB applied alone or with diclosulam, dimethenamid, flumioxazin, or metolachlor 6 to 8 wk after peanut emergence was evaluated. In a second set of experiments, paraquat plus bentazon was applied alone or with diclosulam, dimethenamid, flumioxazin, imazethapyr, or metolachlor 2 wk after peanut emergence. In a third set of experiments, imazapic was applied alone or with diclosulam or flumioxazin 3 to 4 wk after peanut emergence. In the fourth experiment, 2,4-DB was applied approximately 7, 5, or 3 wk before digging and inversion of vines. Flumioxazin applied alone or with aciflurofen plus bentazon (with or without 2,4-DB) injured peanut more than diclosulam, dimethenamid, or metolachlor applied alone or with acifluorfen plus bentazon or aciflurofen plus bentazon plus 2,4-DB. Flumioxazin reduced pod yield 620 kg/ha when compared to non-treated peanut. Additionally, acifluorfen plus bentazon and acifluorfen plus bentazon plus 2,4-DB reduced yield by 200 and 150 kg/ha, respectively, when compared with non-treated peanut. Flumioxazin applied with paraquat plus bentazon was more injurious than diclosulam, dimethenamid, imazethapyr, or metolachlor applied with paraquat plus bentazon. There was no difference in peanut injury when paraquat plus bentazon was applied alone or with diclosulam. Dimethenamid or metolachlor increased injury by paraquat plus bentazon. Although diclosulam did not affect peanut injury from imazapic, injury increased when imazapic was applied with flumioxazin. When pooled over nine sites, 2,4-DB did not adversely affect pod yield, gross economic value, or percent seed germination when applied 7, 5, or 3 wk before vine inversion.

A seedling bioassay was developed for the rapid diagnosis of resistance to clethodim and fluazifop-P in johnsongrass. The assay was based on differences in the coleoptile length of susceptible (S) and resistant (R) seedlings exposed to clethodim and fluazifop-P in petri dishes for 5 d. Bioassay concentrations of 0.09 mg/L clethodim and 0.18 mg/L fluazifop-P were chosen as discriminant based on rate responses of each biotype to increasing herbicide dose. At 5 d after treatment (DAT), the amounts of clethodim required to reduce coleoptile length by 50% (GR50) for the R and S seedlings were 462.5 and 24.8 mg/L, respectively, resulting in an R:S ratio of 18.7. The fluazifopGR50values for the R and S seedlings were 618.7 and 17.5 mg/L, respectively, resulting in a R:S ratio of 35.4.

Laboratory and greenhouse studies were conducted to determine the effect of temperature, solution pH, water stress, and planting depth on broadleaf signalgrass germination. Broadleaf signalgrass seed required removal of the husk for germination. When treated with constant temperature, broadleaf signalgrass germinated over a range of 20 to 35 C, with optimum germination occurring at 30 and 35 C. Onset, rate, and total germination (87%) was greatest in an alternating 20/30 C temperature regime. Germination decreased as solution pH increased, with greatest germination occurring at pH values of 4 and 5. Germination decreased with increasing water potential, and no germination occurred below −0.8 mPa. Emergence was above 42% when seed were placed on the soil surface or buried 0.5 cm deep. Germination decreased with burial depth, but 10% of broadleaf signalgrass seed emerged from 6.0-cm depth. No seed emerged from 10-cm depth. These data suggest that broadleaf signalgrass may emerge later in the season, after rains, and could germinate rapidly and in high numbers. These attributes could contribute to poor control later in the season by soil-applied herbicides or allow broadleaf signalgrass to emerge after final postemergence treatments were made.