Janet F. Spears

Influence of environmental factors on slender amaranth (Amaranthus viridis) germination

Abstract 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. Nomenclature: Slender amaranth, Amaranthus viridis L. AMAVI.

Influence of environmental factors on broadleaf signalgrass (Brachiaria platyphylla) germination

Abstract 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. Nomenclature: Broadleaf signalgrass, Brachiaria platyphylla (Griseb.) Nash BRAPP.

Influence of environmental factors on after-ripened crowfootgrass (Dactyloctenium aegyptium) seed germination

Abstract 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. Nomenclature: Crowfootgrass, Dactyloctenium aegyptium (L.) Willd. DTTAE.

Virginia Market-Type Peanut (Arachis hypogaea) Cultivar Tolerance and Yield Response to Flumioxazin Preemergence1

Abstract: 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. Nomenclature: Flumioxazin; peanut, Arachis hypogaea L., ‘NC 12C’, ‘NC 7’, ‘VAC 92R’, ‘NC-V 11’, ‘NC 10C’, ‘AT VC 1’, ‘NC 9’, ‘N9001OE’. Additional index words: Disease interaction, Cylindrocladium crotalariae (Loos) Bell and Sobers, Cercospora arachidicola Hori, Cercosporidium personatum (Berk. and Curt.), Sclerotium rolfsii Sacc., grade parameters, extra-large kernels, sound mature kernels, sound splits, total kernels, other kernels, fancy pods. Abbreviations: CBR, cylindrocladium black rot; DAP, days after planting; ELK, extra-large kernels; PPI, preplant incorporated; PRE, preemergence; SMK, sound mature kernels; SS, sound splits; TMSK, total sound mature kernels; TSWV, tomato spotted wilt virus; WAP, weeks after planting.

Diclosulam Does Not Influence Yields in Eight Virginia Market-Type Peanut (Arachis hypogaea) Cultivars1

Abstract: 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. Nomenclature: Diclosulam; peanut, Arachis hypogaea L. NC 12C, NC 7, VAC 92R, NC-V 11, NC 10C, AT VC 1, NC 9, N90010E. Additional index words: Disease interaction, cylindrocladium black rot, Cylindrocladium crotalariae (Loos) Bell et Sobers, early leaf spot, Cercospora arachidicola Hori, late leaf spot, Cercosporidium personatum (Berk. et Curt.), southern stem rot, Sclerotium rolfsii Sacc., tomato spotted wilt virus, grade parameters, extra large kernels, sound mature kernels, sound splits, total kernels, other kernels, fancy pods. Abbreviations: CBR, cylindrocladium black rot; DAP, days after planting; ELK, extra large kernels; PPI, preplant incorporated; SMK, sound mature kernels; SS, sound splits; TSMK, total sound mature kernels; TSWV, tomato spotted wilt virus; WAP, weeks after planting.

Doveweed (Murdannia nudiflora) germination and emergence as affected by temperature and seed burial depth

Abstract Doveweed is becoming more common in agronomic crops in North Carolina. Laboratory and greenhouse experiments were conducted to determine the effect of temperature and seed burial depth on doveweed germination and emergence. Germination of lightly scarified seed at constant temperature was well described by a Gaussian model, which estimated peak germination at 28 C. Similar maximum percentage of germination was observed for optimal treatments under both constant and alternating temperatures. Among alternating temperatures, a 35/25 C regime gave greatest germination (77%). In spite of similar average daily temperatures, germination was greater with alternating temperature regimes of 40/30 and 40/35 C (65 and 30%, respectively) than constant temperatures of 36 and 38 C (4 and 0%, respectively). No germination was observed at 38 C constant temperature or for alternating temperature regimes of 20/10 and 25/15 C. Light did not enhance germination. Greatest emergence occurred from 0 to 1 cm, with a reduction in emergence as depth increased to 4 cm. No emergence occurred from 6 cm or greater depth. This information on seedbank dynamics may aid in developing tools and strategies for management. Nomenclature: Doveweed, Murdannia nudiflora (L.) Brenan MUDNU.

Sicklepod (Senna obtusifolia) Control and Seed Production after 2,4-DB Applied Alone and with Fungicides or Insecticides'

Experiments were conducted during 1999, 2002, and 2003 to evaluate sicklepod control by 2,4-DB applied alone or in mixture with selected fungicides and insecticides registered for use in peanut. The fungicides boscalid, chlorothalonil, fluazinam, propiconazole plus trifloxystrobin, pyraclostrobin, or tebuconazole and the insecticides acephate, carbaryl, esfenvalerate, fenpropathrin, lambda-cyhalothrin, methomyl, or indoxacarb applied in mixtures with 2,4-DB did not reduce sicklepod control by 2,4-DB compared with 2,4-DB alone. The fungicide azoxystrobin reduced control in some but not all experiments. Sicklepod control was highest when 2,4-DB was applied before flowering regardless of fungicide treatment. Seed production and germination were reduced when 2,4-DB was applied 81 to 85 d after emergence when sicklepod was flowering. Applying 2,4-DB before flowering and at pod set and pod fill did not affect seed production. Nomenclature: Acephate, O,S-dimethyl acetylphosphoramidiothioate; azoxystrobin, methyl (E)-2-[2-[6-(2-cyanophenoxy)pyrimidin-4-yloxy]phenyl]-3-methoxyacrylate; boscalid, 3-pyridinecarboxamide,2-chloro-N-[4′-chloro(1,1′-biphenyl)-2-yl]; carbaryl, 1-napthyl N-methylcarbamate; chlorothalonil, tetrachloroisophthalonitrile; 2,4-DB; esfenvalerate, (S)-cyano (3-phenoxyphenyl) methyl (S)-4-chloro-α-(1-methylethyl)benzenacetate; fenpropathrin, α-cyano-3-phenoxybenzyl 2,2,3,3-tetramethylcyclopropanecarboxylate; fluazinam, 3-chloro-N-[3-chloro-2,6-dinitro-4-(trifluoromethyl)phenyl]-5-(trifluoromethyl)-2-pyridinamine; indoxacarb, (S)-methyl 7-chloro-2,5-dihydro2-[[ (methoxy-carbonyl) [ 4(trifluorometoxy)phenyl]amino]-carbonyl]indeno[1,2-e][1,3,4]oxadiazine-4a-(3H)-carboxylate; lambda-cyhalothrin, [1,α(S*),3α(Z)]-(±)-cyano-(3-phenoxyphenyl)methyl-3-(2-chloro-3,3,3-tifluoro-1-propenyl)-2,2-dimethylcyclopropanecarboxylate; methomyl, S-methyl-N-[(methylcarbamoyl)oxy] thioacetimidate; propiconazole, 1-[2-(2,4-dichlorophenyl)-4-propyl-1,3-dioxolan-2-yl-methyl]-1H-1,2,4 triazole; pyraclostrobin, carbamic acid, [2-[[[1-(4-chlorophenyl)-1H-pyrazol-3yl]oxy]methyl]phenyl]methoxy-,methyl ester; tebuconazole, α-[2-(4-chlorophenyl)ethyl]-α-(1,1-dimethylethyl)-1H-1,2,4-triazole-1-ethanol; trifloxystrobin, benzeneacetic acid, α-(methoxyimino)-2-[[[(E)-[1-[3-(trifluoromethyl)phenyl] ethylidene]amino]oxy]methyl]-, methylester (E,E); sicklepod, Senna obtusifolia L. Irwin and Barneby #3 CASOB; peanut, Arachis hypogaea L. Additional index word: Pesticide interaction. Abbreviation: DAE, days after emergence.

A Seedling Assay to Screen Aryloxyphenoxypropionic Acid and Cyclohexanedione Resistance in Johnsongrass (Sorghum halepense)1

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 fluazifop GR50 values for the R and S seedlings were 618.7 and 17.5 mg/L, respectively, resulting in a R:S ratio of 35.4. Nomenclature: Clethodim, fluazifop-P, johnsongrass, Sorghum halepense (L.) Pers. #3SORHA. Additional index words: ACCase inhibitors, herbicide resistance. Abbreviations: ACCase, acetyl coenzyme-A carboxylase; AOPP, aryloxyphenoxypropionate; CHD, cyclohexanedione.

Influence of Environmental Factors on Cutleaf Eveningprimrose (Oenothera laciniata) Germination, Emergence, Development, Vegetative Growth, and Control

Abstract Laboratory and greenhouse studies were conducted to determine the effect of temperature, solution pH, water stress, and planting depth on cutleaf eveningprimrose germination and emergence. Field studies were conducted to measure growth parameters of cutleaf eveningprimrose throughout the fall season. When treated with constant temperature, cutleaf eveningprimrose germinated over a range of 15 to 32 C, with the optimum germination occurring at 24 C. Onset, rate, and total germination were greatest in an alternating 20/35 C temperature regime. Germination decreased as solution pH increased, with greatest germination occurring at solution pH of 4. Germination decreased when cutleaf eveningprimrose seed was subjected to increased water stress. Emergence was optimum when seed were buried at depths of 0.5 cm. Germination decreased with increasing burial depth, and no seed emerged from a depth of 10 cm. Cutleaf eveningprimrose control was maximized when 2,4-D was applied in mixture with glyphosate or paraquat. These data suggest that cutleaf eveningprimrose can germinate and gain biomass from early March to late October. These attributes could contribute to poor control before cotton planting if preplant control applications are delayed after early March. Nomenclature: Cutleaf eveningprimrose, Oenothera laciniata Hill OEOLA, cotton, Gossypium hirsutum L

Effect of Production Environment on Seed Quality of Normal and High- Oleate Large Seeded Virginia-Type Peanut (Arachis hypogaea L.)

ABSTRACT Six Virginia-type peanut (Arachis hypogaea L.) cultivars and their paired backcross-derived high-oleate lines were grown during 2003 and 2004 in North Carolina to compare standard germination (SG), cool germination (CG), and electrical conductivity (EC) of seed. Oleic acid level had no influence on SG but did alter CG and EC compared to the corresponding normal oleate cultivars. Averaged across background genotypes, high-oleate lines had lower seed vigor than their paired lines with normal oleic content. The high-oleate lines of three of the six pairs had lower CG and higher EC. Planting and harvest date affected all the seed quality traits measured. Standard germination of both normal and high-oleate lines was reduced in 2004 when harvest was delayed, but was not affected in 2003. In 2003, CG of the high-oleate lines was lower than that of normal lines in three of the four production environments; EC was higher in the high-oleate lines in all planting date and harvest date combinations. In 2004,...