Bridget R. Lassiter

Yield and Physiological Response of Peanut to Glyphosate Drift

Five experiments were conducted during 2001 and 2002 in North Carolina to evaluate peanut injury and pod yield when glyphosate was applied to 10 to 15 cm diameter peanut plants at rates ranging from 9 to 1,120 g ai/ha. Shikimic acid accumulation was determined in three of the five experiments. Visual foliar injury (necrosis and chlorosis) was noted 7 d after treatment (DAT) when glyphosate was applied at 18 g/ha or higher. Glyphosate at 280 g/ha or higher significantly injured the peanut plant and reduced pod yield. Shikimic acid accumulation was negatively correlated with visual injury and pod yield. The presence of shikimic acid can be detected using a leaf tissue assay, which is an effective diagnostic tool for determining exposure of peanut to glyphosate 7 DAT. Nomenclature: Glyphosate; peanut, Arachis hypogaea L. ARHHY.

Peanut (Arachis hypogaea L.) cultivar response to prohexadione calcium

Peanut digging efficiency is often reduced due to excessive vine growth. The plant growth regulator prohexadione calcium retards vegetative growth and improves row visibility by inhibiting internode elongation resulting in improved digging efficiency and in some instances increases in pod yield. The objective of this research was to determine the effects of prohexadione calcium on row visibility and pod yield of newly released and commercially available cultivars AT VC-2, Brantley, CHAMPS, Georgia Green, Gregory, Perry, Phillips, NC-V 11, NC 12C, Tamspan 90, and VA 98R and the breeding lines N02006, N01013T, and VT 976133. Although differences in row visibility were noted among cultivars, prohexadione calcium improved row visibility in almost every experiment regardless of cultivar. The cultivars NC 12C and Perry were more responsive to prohexadione calcium in terms of pod yield than NC-V 11 or VA 98R. Response of these cultivars was independent of digging date. In other experiments, prohexadione calcium improved row visibility of the cultivars AT VC-2, Gregory, NC-V 11, Perry, VA 98R, and Wilson, but did not increase yield when compared with non-treated peanut. In a final experiment, prohexadione calcium improved row visibility of the Virginia market type cultivars Brantley, CHAMPS, Gregory, and Phillips and the experimental lines N02006, N01013T, and VT 976133. Row visibility for the experimental line N01013T was improved at 2 of 4 sites by prohexadione calcium. In a final experiment, prohexadione calcium increased row visibility of Georgia Green, Gregory, and Tamspan 90 but did not affect pod yield of these cultivars.

Weed Management in Peanut with Herbicide Combinations Containing Imazapic and Other Pesticides

Abstract Research was conducted in North Carolina to compare weed control by various rates of imazapic POST alone or following diclosulam PRE. In a second experiment, weed control by imazapic applied POST alone or with acifluoren, diclosulam, or 2,4-DB was compared. In a final experiment, yellow nutsedge control by imazapic alone and with the fungicides azoxystrobin, chlorothalonil, pyraclostrobin, and tebuconazole was compared. Large crabgrass was controlled more effectively by imazapic POST than diclosulam PRE. Common lambsquarters, common ragweed, and eclipta were controlled more effectively by diclosulam PRE than imazapic POST. Nodding spurge was controlled similarly by both herbicides. Few differences in control were noted when comparing imazapic rates after diclosulam PRE. Applying either diclosulam PRE or imazapic POST alone or in combination increased peanut yield over nontreated peanut in five of six experiments. Few differences in pod yield were noted when comparing imazapic rates. Acifluorfen, diclosulam, and 2,4-DB did not affect entireleaf morningglory, large crabgrass, nodding spurge, pitted morningglory, and yellow nutsedge control by imazapic. Eclipta control by coapplication of imazapic and diclosulam exceeded control by imazapic alone. The fungicides azoxystrobin, chlorothalonil, pyraclostrobin, and tebuconazole did not affect yellow nutsedge control by imazapic. Nomenclature: Acifluorfen; azoxystrobin, methyl (E)-2-{2-[6-(2-cyanophenoxy)pyrimidin-4-yloxy]phenyl}-3-methoxyacrylate; bentazon; chlorothalonil, tetrachloroisophthalonitrile; 2,4-DB; diclosulam; imazapic; pyraclostrobin, methyl [2-[[[1-(4-chlorophenyl)-1H-pyrazol-3-yl]oxy]methyl]phenyl]methoxycarbamate; tebuconazole, α-[2-(4-chlorophenyl)ethyl]-α-(1,1-dimethylethyl)-1H-1,2,4-triazole-1-ethanol; common lambsquarters, Chenopodium album L. CHEAL; common ragweed, Ambrosia artemisiifolia L. AMBEL; eclipta, Eclipta prostrata L. ECLAL; entireleaf morningglory, Ipomoea hederacea var. integruscula Gray IPOHG; large crabgrass, Digitaria sanguinalis (L.) Scop. DIGSA; nodding spurge, Chamaesyce nutans (Lag.) Small EPHNU; pitted morningglory, Ipomoea lacunosa L. IPOLA; yellow nutsedge, Cyperus esculentus L. CYPES; peanut, Arachis hypogaea L

Influence of Cover Crops on Weed Management in Strip Tillage Peanut

Abstract Experiments were conducted in North Carolina during 2005, 2006, and 2007 to determine peanut and weed response when peanut was planted in strip tillage after desiccation of cereal rye, Italian ryegrass, oats, triticale, wheat, and native vegetation by glyphosate and paraquat before planting with three in-season herbicide programs. Control of common ragweed and yellow nutsedge did not differ among cover crop treatments when compared within a specific herbicide program. Applying dimethenamid or S-metolachlor plus diclosulam PRE followed by imazapic POST was more effective than a chloroacetamide herbicide PRE followed by acifluorfen, bentazon, and paraquat POST. Incidence of spotted wilt in peanut (caused by a Tospovirus) did not differ when comparing cover crop treatments, regardless of herbicide program. Peanut yield increased in all 3 yr when herbicides were applied POST, compared with clethodim only. Peanut yield was not affected by cover crop treatment. Response to cover crop treatments was comparable, suggesting that growers can select cereal rye, Italian ryegrass, oats, or triticale as an alternative to wheat as a cover crop in peanut systems without experiencing differences associated with in-season weed management. Nomenclature: Acifluorfen; bentazon; glyphosate; imazapic; paraquat; common ragweed, Ambrosia artemisiifolia L.; yellow nutsedge, Cyperus esculentus L.; cereal rye, Secale cereale L.; Italian ryegrass, Lolium multiflorum Lam.; oats, Avena sativa L.; peanut, Arachis hypogaea L.; triticale, Triticale hexaploide Lart.; wheat, Triticum aestivum L.

Confirmation and Management of Common Ragweed (Ambrosia artemisiifolia) Resistant to Diclosulam

Abstract Selection for biotypes of common ragweed expressing resistance to acetolactate synthase (ALS)–inhibiting herbicides has increased in North Carolina and surrounding states. Research was conducted in North Carolina to confirm common ragweed resistance to diclosulam and to compare herbicide programs designed to control ALS-resistant common ragweed in corn, cotton, peanut, and soybean. In greenhouse experiments, 50% inhibition values following POST application of diclosulam for mortality of plants, visual estimates for percentage of control, and percentage of reduction in plant fresh weight were 557- to 653-fold higher for the suspected ALS-resistant biotype compared with a suspected ALS-susceptible biotype. Herbicides with different modes of action, including atrazine, dicamba, and glyphosate in corn; fomesafen, glyphosate, MSMA, and prometryn in cotton; bentazon, flumioxazin, and lactofen in peanut; and flumioxazin, glyphosate, and lactofen in soybean controlled common ragweed more effectively than programs relying on cloransulam-methyl (soybean), diclosulam (peanut), thifensulfuron (corn), and trifloxysulfuron (cotton), which typically control nonresistant common ragweed populations. Applying tank-mix or sequential applications of herbicides with different modes of action was effective in controlling ALS-resistant common ragweed in all crops. Nomenclature: Atrazine; cloransulam-methyl; dicamba; diclosulam; flumioxazin; fomesafen; glyphosate; lactofen; prometryn; trifloxysulfuron; common ragweed, Ambrosia artemisiifolia L.; corn, Zea mays L.; cotton, Gossypium hirsutum L.; peanut, Arachis hypogaea L.; soybean, Glycine max (L.) Merr.

Peanut and Eclipta (Eclipta prostrata) Response to Flumioxazin

Abstract Research was conducted in North Carolina to determine peanut response to flumioxazin as influenced by rate and timing of application and cultivar. Delaying application of flumioxazin from 1 d after planting until peanut emergence increased injury regardless of rate. The Virginia market-type cultivar ‘NC-V 11’ was injured more by flumioxazin than the cultivars ‘Gregory’ or ‘Perry’. However, pod yield was not affected by flumioxazin even though significant injury was observed early in the season regardless of flumioxazin rate, application timing, or cultivar. Diclosulam was more effective than flumioxazin in controlling eclipta when these herbicides were applied PRE with metolachlor or following pendimethalin PPI. However, control by flumioxazin prevented yield loss when compared with metolachlor alone. Nomenclature: Diclosulam; flumioxazin; eclipta, Eclipta prostrata L.; peanut, Arachis hypogaea L., ‘Gregory’, ‘NC-V 11’, ‘Perry’.

Influence of Planting Pattern on Pest Management in Virginia Market Type Peanut (Arachis hypogaea L.)

Abstract Twelve field trials were completed in North Carolina from 2005 to 2007 to determine the impact of planting pattern on peanut yield, market grade characteristics, and pest reaction for the Virginia market type cultivars Perry and VA 98R. The first set of experiments was designed to evaluate incidence of Cylindrocladium black rot (caused by Cylindrocladium parasiticum) using a factorial treatment arrangement of two cultivars, two levels of fumigation (none or metam sodium at 112 L/ha), and two levels of planting pattern (single rows spaced 91-cm apart or twin rows spaced 18 cm apart on 91-cm centers). Damage from tobacco thrips (Frankiella fusca) was higher in the cultivar VA 98R planted in twin rows than in single rows or for the cultivar Perry. Visible symptoms associated with Cylindrocladium black rot were not affected by planting pattern. However, in 1 of 3 trials pod scarring as a result of feeding by southern corn rootworm (Diabrotica undecimpunctata Howardi) was greater in twin rows compared...