Studies were conducted in North Carolina to determine the effect of holding durations (HDs) [0, 1... more Studies were conducted in North Carolina to determine the effect of holding durations (HDs) [0, 1, 3, 5, and 7 days before planting (DBP)] of ‘Covington’ sweetpotato (Ipomoea batatas) transplants on plant stand and storage root numbers and yield in production fields. In a second field study, the effect of preplant irrigation (PI) treatments (PI and nonirrigation) were evaluated along with the transplant HD on plant stand, storage root numbers, and yield. Transplants held for 7 DBP did not survive as well as the other treatments (lower plant stands) and had lower no. 1, marketable, and total storage root numbers and yields than other holding treatments. HD of 1 or 3 DBP resulted in higher plant stands, and no. 1, marketable, and total numbers of storage roots and yields than holding for 0, 5, or 7 DBP. This study affirms the importance of soil moisture at and shortly after planting for transplant survival and yield. Holding transplants for 1–3 DBP can improve stand establishment and ...
The reason for internal necrosis occurrences in sweetpotato (Ipomoea batatas) storage roots is no... more The reason for internal necrosis occurrences in sweetpotato (Ipomoea batatas) storage roots is not well understood. This disorder begins internally in the storage roots as small light brown spots near the proximal end of the root that eventually can become more enlarged as brown/black regions in the cortex. The objective of this study was to determine the effect of ethephon and flooding on the development of internal necrosis in the sweetpotato cultivars Beauregard, Carolina Ruby, and Covington over storage durations from 9 to 150 days after harvest (DAH) when roots had been cured. Soil moisture treatments were no-flooding, and simulated flooding that was created by applying 10 inches of overhead irrigation during 2 weeks before harvest. Ethephon was applied at 0, 0.75, and 0.98 lb/acre 2 weeks before harvest. Overall, ‘Covington’ and ‘Carolina Ruby’ had greater internal necrosis incidence (22% to 65% and 32% to 51%, respectively) followed by ‘Beauregard’ (9% to 22%) during storage ...
Partial budget analysis was used to evaluate soil treatment alternatives to methyl bromide (MeBr)... more Partial budget analysis was used to evaluate soil treatment alternatives to methyl bromide (MeBr) based on their cost-effectiveness in the production of strawberries (Fragaria ×ananassa). The analysis was conducted for two geographical areas: the piedmont and coastal plain area (including North Carolina and Georgia) and the mountain area of western North Carolina, based on 7 years of field test data. The fumigation alternatives evaluated were Telone-C35 (1,3-dichloropropene 61.1% + chloropicrin 34.7%), Telone II (1,3-dichloropropene 94%), chloropicrin (Chlor-o-pic 99% and TriClor EC), InLine (1,3-dichloropropene 60.8% + chloropicrin 33.3%), and metam sodium (Vapam or Sectagon 42, 42% sodium methyldithiocarbamate). The MeBr formulation was 67% MeBr and 33% chloropicrin (Terr-O-Gas) with the exception of the earlier trials where a 98:2 ratio was used. In the piedmont and coastal plain area, the soil treated with chloropicrin showed the best results with an additional return of $1670/a...
Grafting of watermelon (Citrullus lanatus) is an established production practice that provides re... more Grafting of watermelon (Citrullus lanatus) is an established production practice that provides resistance to soilborne diseases or tolerance to abiotic stresses. Watermelon may be grafted on several cucurbit species (interspecific grafting); however, little research exists to describe root systems of these diverse rootstocks. A greenhouse study was conducted to compare root system morphology of nine commercially available cucurbit rootstocks, representing four species: pumpkin (Cucurbita maxima), squash (Cucurbita pepo), bottle gourd (Lagenaria siceraria), and an interspecific hybrid squash (C. maxima × C. moschata). Rootstocks were grafted with a triploid watermelon scion (‘Exclamation’), and root systems were compared with nongrafted (NG) and self-grafted (SG) ‘Exclamation’. Plants were harvested destructively at 1, 2, and 3 weeks after transplant (WAT), and data were collected on scion dry weight, total root length (TRL), average root diameter, root surface area, root:shoot dry-w...
There is a research gap with respect to documenting the effects of sweetpotato (Ipomoea batatas) ... more There is a research gap with respect to documenting the effects of sweetpotato (Ipomoea batatas) seed root density and size on transplant yield and quality. Field studies were conducted in 2012 and 2014 to determine the effect of sweetpotato seed root (canner size) density [12, 24, 37, 49, 61, 73, and 85 bushels [bu (50 lb)] per 1000 ft2] on ‘Covington’ and ‘Evangeline’ slip production in propagation beds. Another field study was conducted in 2012 and 2013; treatments included canner, no. 1, and jumbo-size ‘Covington’ roots at 49 bu/1000 ft2, to determine the effect of seed root size on slip production. As seed root density increased in the propagation bed, transplant production increased with no change in slip quality as measured by node counts and slip length except for stem diameter. In 2012, the best marketable slip yield was obtained at root densities of 73 and 85 bu/1000 ft2. In 2014, marketable slip production of ‘Evangeline’ increased as seed root density increased at a grea...
Field studies were conducted in 2009 at Clinton, NC and 2014 at Pontotoc, MS to determine the inf... more Field studies were conducted in 2009 at Clinton, NC and 2014 at Pontotoc, MS to determine the influence of simulated glyphosate drip on sweetpotato yield and quality. Treatments consisted of three glyphosate solution (140 g ae L–1) drip volumes (0.16, 0.32 and 0.48 ml) by four application timings [(4 wk after transplanting (WAP); 6 WAP; 8 WAP; and 4 WAP followed by (fb) 6 WAP fb 8 WAP]. A non-treated check was included for comparison. Visual sweetpotato injury consisted of chlorosis at the shoot tips approximately 1 wk after treatment fb necrosis and stunting. At 6 WAP and 8 WAP, sweetpotato injury following glyphosate applied 4 WAP was 71 and 65%, respectively. Injury from glyphosate applied 4 WAP fb 6 WAP was 78%. Injury from glyphosate applied 6 WAP was 26% at 8 WAP. In 2009, jumbo, no. 1, canner, and marketable yield of the non-treated check were two to three times greater than glyphosate treatments (0.16, 0.32, 0.48 ml). Likewise, yield of the non-treated check was substantiall...
Palmer amaranth (Amaranthus palmeri S. Wats.) is a highly competitive weed that can be difficult ... more Palmer amaranth (Amaranthus palmeri S. Wats.) is a highly competitive weed that can be difficult to manage in many cropping systems. Research to date has not quantified the growth and development of A. palmeri in a manner that allows direct comparisons across cropping systems. Research was conducted to compare the growth, development, and seed production of A. palmeri when competing with corn (Zea mays L.), cotton (Gossypium hirsutum L.), peanut (Arachis hypogaea L.), and soybean [Glycine max (L.) Merr.] when emerging with crops or emerging three weeks after crops emerge. Regardless of when A. palmeri emerged, seed production was greatest and similar in cotton and peanut and exceeded that of corn and soybean; seed production in soybean exceeded that of corn. However, seed production was approximately 10-fold greater when A. palmeri emerged with crops compared with emergence three weeks later. These results illustrate the importance of controlling weeds during the first three weeks o...
There has been renewed interest in using fluridone herbicide to aid in control of glyphosateresis... more There has been renewed interest in using fluridone herbicide to aid in control of glyphosateresistant Palmer amaranth (Amaranthus palmeri S. Watson) in cotton (Gossypium hirsutum L.). Section 18 Emergency Use Exemptions for fluridone in cotton have been granted recently in several states and the manufacturer is pursuing federal registration. Fluridone has long persistence in soil, leading to questions about rotational crop response. Field experiments were conducted in North Carolina to evaluate the potential for fluridone to carry over to corn (Zea mays L.), peanut (Arachis hypogaea L.), grain sorghum [Sorghum bicolor (L.) Moench.], and soybean [Glycine max (L.) Merr.] grown in rotation with fluridone-treated cotton. Fluridone at 0, 280, 420, 560, 840, and 1120 g ai ha -1 was applied preemergence to cotton and rotational crops were planted the following spring. The fluridone rates were well above proposed use rates. Only minor visible injury to cotton was observed and cotton yield w...
MEYERS, STEPHEN LAWRENCE. Interference and Control of Palmer Amaranth (Amaranthus palmeri) in Swe... more MEYERS, STEPHEN LAWRENCE. Interference and Control of Palmer Amaranth (Amaranthus palmeri) in Sweetpotato. (Under the direction of Katie Jennings and Jonathan Schultheis.) The most common and troublesome weed in North Carolina sweetpotato is Palmer amaranth, an upright, branching, annual weed with rapid growth and high fecundity. Field studies were conducted in 2007 and 2008 to develop a Palmer amaranth management program in sweetpotato using density models to establish thresholds, and herbicides for control. Palmer amaranth was established at 0, 0.5, 1.1, 1.6, 3.3, and 6.5 plants/m within the sweetpotato row and densities maintained season-long. Jumbo, no. 1, and marketable sweetpotato yield loss ranged from 56 to 94%, 30 to 85%, and 36 to 81%, respectively for 0.5 to 6.5 Palmer amaranth/m. Yield loss displayed a positive linear relationship with Palmer amaranth light interception. Light intercepted by the Palmer amaranth canopy increased linearly from 0.5 to 6.5 plants/m and was g...
Studies were conducted in 2012 and 2013 to compare Evangeline to various sweetpotato (Ipomoea bat... more Studies were conducted in 2012 and 2013 to compare Evangeline to various sweetpotato (Ipomoea batatas) varieties (Bayou Belle, Beauregard, Bonita, Covington, NC05-198, and Orleans) for commercial production in North Carolina. In another study, microwaved and oven-baked ‘Evangeline’ and ‘Covington’ sweetpotato roots were subjected to analysis of chemical and physical properties [color, dry matter (DM), texture, and sugar] and to sensory evaluation for determining consumer acceptance. ‘NC05-198’ produced the highest no. 1 grade sweetpotato 600 bushels [bu (50 lb)] per acre and total marketable storage root yield was similar to ‘Bayou Belle’ and ‘Beauregard’ (841, 775, and 759 bu/acre, respectively). No. 1 and marketable root yields were similar between ‘Orleans’ and ‘Beauregard’. However, ‘Orleans’ produced more uniform roots than ‘Beauregard’, in which the latter had higher cull production. ‘Evangeline’ was comparable to no. 1 yield of ‘Bayou Belle’, ‘Orleans’, and ‘Covington’, which...
Lab and greenhouse studies were conducted to evaluate the effects of chemical treatments applied ... more Lab and greenhouse studies were conducted to evaluate the effects of chemical treatments applied to Palmer amaranth seeds or gynoecious plants retaining seeds on seed germination and quality. Treatments applied to physiologically mature Palmer amaranth seed included acifluorfen, dicamba, ethephon, flumioxazin, fomesafen, halosulfuron, linuron, metribuzin, oryzalin, pendimethalin, pyroxasulfone, S-metolachlor, saflufenacil, trifluralin, and 2,4-D plus crop oil concentrate applied at 1 and 2× the suggested use rates from the manufacturer. Germination was reduced by 20% from 2,4-D, 15% from dicamba, and 13% from halosulfuron and pyroxasulfone. Dicamba, ethephon, halosulfuron, oryzalin, trifluralin, and 2,4-D decreased the average seedling length by at least 50%. Due to the observed effect of dicamba, ethephon, halosulfuron, oryzalin, trifluralin, and 2,4-D, these treatments were applied to gynoecious Palmer amaranth inflorescence at the 2× registered application rates to evaluate their...
Palmer amaranth (Amaranthus palmeri S. Watson) populations resistant to acetolactate synthase-inh... more Palmer amaranth (Amaranthus palmeri S. Watson) populations resistant to acetolactate synthase-inhibiting (ALS) herbicides and glyphosate are fairly common throughout the state of North Carolina (NC). This has led farm managers to rely more heavily on herbicides with other sites of action (SOA) for A. palmeri control, especially protoporphyrinogen oxidase- and glutamine synthetase inhibitors. In the fall of 2016, seeds from A. palmeri populations were collected from the NC Coastal Plain, the state’s most prominent agricultural region. In separate experiments, plants with 2 to 4 leaves from the 110 populations were treated with field use rates of glyphosate, glufosinate-ammonium, fomesafen, mesotrione, or thifensulfuron-methyl. Percent visible control and survival were evaluated three weeks after treatment. Survival frequencies were highest following glyphosate (99%) or thifensulfuron-methyl (96%) treatment. Known mutations conferring resistance to ALS inhibitors were found in populat...
Field trials were conducted in North Carolina in 2017 and Louisiana and Mississippi in 2018 to de... more Field trials were conducted in North Carolina in 2017 and Louisiana and Mississippi in 2018 to determine the effect of pre-transplanting applications of diquat on sweetpotato crop tolerance, yield, and storage root quality. At North Carolina treatments consisted of two rates of diquat (560 or 1,120 g ai ha-1) alone or mixed with 107 g ai ha-1 flumioxazin and applied 1 d before transplanting (DBP), sequential applications of diquat (560 or 1,120 g ha-1) 1 and 17 DBP, 107 g ha-1 flumioxazin alone, and a non-treated check. At Louisiana and Mississippi treatments consisted of diquat (560 or 1,120 g ha-1) applied 1 DBP either alone or followed by (fb) rehipping rows or 107 g ha-1 flumioxazin immediately prior to transplanting. Additional treatments included 546 g ha-1 paraquat applied 1 DBP and a non-treated check. At North Carolina injury was ≤ 3% for all treatments through 23 DAP, and no injury was observed after 23 DAP. Visual sweetpotato stunting pooled across Mississippi and Louisia...
A research gap exists on the effects of irrigation, transplant (nonrooted stem cuttings) size, an... more A research gap exists on the effects of irrigation, transplant (nonrooted stem cuttings) size, and planting depth on sweetpotato (Ipomoea batatas) plant survival and storage root yield. Field studies were conducted in 2012 and 2013 to determine the effects of preplant irrigation, planting depth, and transplant size on sweetpotato plant stand, storage root number, and yield. Treatments included four transplant sizes (3.7, 6.3, 8.5, and 10.7 inches), two planting depths (2 and 6 inches), and preplant irrigation or nonirrigation. Overall, plant stand, storage root number, and yield were greater when transplants of size ≥6.3 inches were planted 6 inches deep as compared with transplants planted 2 inches deep. The use of preplant irrigation had an overall positive impact on plant stand, storage root number, and yield under dry soil conditions. When moisture was readily available, neither plant stand nor storage root numbers were affected by the application of irrigation as observed in 20...
Field studies were conducted in 2016 and 2017 in Clinton, NC, to determine the interspecific and ... more Field studies were conducted in 2016 and 2017 in Clinton, NC, to determine the interspecific and intraspecific interference of Palmer amaranth (Amaranthus palmeri S. Watson) or large crabgrass [Digitaria sanguinalis (L.) Scop.] in ‘Covington’ sweetpotato [Ipomoea batatas (L.) Lam.]. Amaranthus palmeri and D. sanguinalis were established 1 d after sweetpotato transplanting and maintained season-long at 0, 1, 2, 4, 8 and 0, 1, 2, 4, 16 plants m−1 of row in the presence and absence of sweetpotato, respectively. Predicted yield loss for sweetpotato was 35% to 76% for D. sanguinalis at 1 to 16 plants m−1 of row and 50% to 79% for A. palmeri at 1 to 8 plants m−1 of row. Weed dry biomass per meter of row increased linearly with increasing weed density. Individual dry biomass of A. palmeri and D. sanguinalis was not affected by weed density when grown in the presence of sweetpotato. When grown without sweetpotato, individual weed dry biomass decreased 71% and 62% from 1 to 4 plants m−1 row ...
Herbicide systems consisting of PRE, early POST, and late POST options arranged factorially were ... more Herbicide systems consisting of PRE, early POST, and late POST options arranged factorially were compared for control of sicklepod in narrow-row soybean with modified acetolactate synthase (ALS) (E.C.4.1.3.18). Other weeds present included common cocklebur and mixed infestations of entireleaf, ivyleaf, pitted, and tall morningglories. PRE options were alachlor or alachlor plus metribuzin plus chlorimuron. Early POST options included chlorimuron, chlorimuron plus thifensulfuron, and no herbicide applied 3 wk after planting. Late POST options were chlorimuron and no herbicide applied 5 wk after planting. POST herbicides were more effective than PRE herbicides on all weeds. Chlorimuron and chlorimuron plus thifensulfuron applied early POST were equally effective on these weeds and usually more effective than chlorimuron applied late POST. There was no advantage of two POST applications compared with a single early POST application. Greatest net returns were obtained in systems using on...
Tomato grafting is practiced worldwide as an innovative approach to manage stress from drought, w... more Tomato grafting is practiced worldwide as an innovative approach to manage stress from drought, waterlogging, insects, and diseases. Metribuzin is a commonly used herbicide in tomato but has potential to cause injury after application if plants are under stress. The influence of metribuzin on grafted tomato under drought-stress has not been studied. Greenhouse experiments were conducted in Raleigh, NC to determine the tolerance of drought-stressed grafted and non-grafted tomato to metribuzin. The tomato cultivar ‘Amelia’ was used as the scion in grafted tomato, and for the non-grafted control. Two hybrid tomato ‘Beaufort’ and ‘Maxifort’ were used as rootstocks for grafted plants. Drought-stress treatments included: no drought-stress; 3 d of drought-stress before metribuzin application with no drought-stress after application (3 d DSB); and 3 d of drought-stress before metribuzin application with 3 d of drought-stress after application (3 d DSBA). Metribuzin was applied at 550 g ai h...
Studies were conducted in North Carolina to determine the effect of holding durations (HDs) [0, 1... more Studies were conducted in North Carolina to determine the effect of holding durations (HDs) [0, 1, 3, 5, and 7 days before planting (DBP)] of ‘Covington’ sweetpotato (Ipomoea batatas) transplants on plant stand and storage root numbers and yield in production fields. In a second field study, the effect of preplant irrigation (PI) treatments (PI and nonirrigation) were evaluated along with the transplant HD on plant stand, storage root numbers, and yield. Transplants held for 7 DBP did not survive as well as the other treatments (lower plant stands) and had lower no. 1, marketable, and total storage root numbers and yields than other holding treatments. HD of 1 or 3 DBP resulted in higher plant stands, and no. 1, marketable, and total numbers of storage roots and yields than holding for 0, 5, or 7 DBP. This study affirms the importance of soil moisture at and shortly after planting for transplant survival and yield. Holding transplants for 1–3 DBP can improve stand establishment and ...
The reason for internal necrosis occurrences in sweetpotato (Ipomoea batatas) storage roots is no... more The reason for internal necrosis occurrences in sweetpotato (Ipomoea batatas) storage roots is not well understood. This disorder begins internally in the storage roots as small light brown spots near the proximal end of the root that eventually can become more enlarged as brown/black regions in the cortex. The objective of this study was to determine the effect of ethephon and flooding on the development of internal necrosis in the sweetpotato cultivars Beauregard, Carolina Ruby, and Covington over storage durations from 9 to 150 days after harvest (DAH) when roots had been cured. Soil moisture treatments were no-flooding, and simulated flooding that was created by applying 10 inches of overhead irrigation during 2 weeks before harvest. Ethephon was applied at 0, 0.75, and 0.98 lb/acre 2 weeks before harvest. Overall, ‘Covington’ and ‘Carolina Ruby’ had greater internal necrosis incidence (22% to 65% and 32% to 51%, respectively) followed by ‘Beauregard’ (9% to 22%) during storage ...
Partial budget analysis was used to evaluate soil treatment alternatives to methyl bromide (MeBr)... more Partial budget analysis was used to evaluate soil treatment alternatives to methyl bromide (MeBr) based on their cost-effectiveness in the production of strawberries (Fragaria ×ananassa). The analysis was conducted for two geographical areas: the piedmont and coastal plain area (including North Carolina and Georgia) and the mountain area of western North Carolina, based on 7 years of field test data. The fumigation alternatives evaluated were Telone-C35 (1,3-dichloropropene 61.1% + chloropicrin 34.7%), Telone II (1,3-dichloropropene 94%), chloropicrin (Chlor-o-pic 99% and TriClor EC), InLine (1,3-dichloropropene 60.8% + chloropicrin 33.3%), and metam sodium (Vapam or Sectagon 42, 42% sodium methyldithiocarbamate). The MeBr formulation was 67% MeBr and 33% chloropicrin (Terr-O-Gas) with the exception of the earlier trials where a 98:2 ratio was used. In the piedmont and coastal plain area, the soil treated with chloropicrin showed the best results with an additional return of $1670/a...
Grafting of watermelon (Citrullus lanatus) is an established production practice that provides re... more Grafting of watermelon (Citrullus lanatus) is an established production practice that provides resistance to soilborne diseases or tolerance to abiotic stresses. Watermelon may be grafted on several cucurbit species (interspecific grafting); however, little research exists to describe root systems of these diverse rootstocks. A greenhouse study was conducted to compare root system morphology of nine commercially available cucurbit rootstocks, representing four species: pumpkin (Cucurbita maxima), squash (Cucurbita pepo), bottle gourd (Lagenaria siceraria), and an interspecific hybrid squash (C. maxima × C. moschata). Rootstocks were grafted with a triploid watermelon scion (‘Exclamation’), and root systems were compared with nongrafted (NG) and self-grafted (SG) ‘Exclamation’. Plants were harvested destructively at 1, 2, and 3 weeks after transplant (WAT), and data were collected on scion dry weight, total root length (TRL), average root diameter, root surface area, root:shoot dry-w...
There is a research gap with respect to documenting the effects of sweetpotato (Ipomoea batatas) ... more There is a research gap with respect to documenting the effects of sweetpotato (Ipomoea batatas) seed root density and size on transplant yield and quality. Field studies were conducted in 2012 and 2014 to determine the effect of sweetpotato seed root (canner size) density [12, 24, 37, 49, 61, 73, and 85 bushels [bu (50 lb)] per 1000 ft2] on ‘Covington’ and ‘Evangeline’ slip production in propagation beds. Another field study was conducted in 2012 and 2013; treatments included canner, no. 1, and jumbo-size ‘Covington’ roots at 49 bu/1000 ft2, to determine the effect of seed root size on slip production. As seed root density increased in the propagation bed, transplant production increased with no change in slip quality as measured by node counts and slip length except for stem diameter. In 2012, the best marketable slip yield was obtained at root densities of 73 and 85 bu/1000 ft2. In 2014, marketable slip production of ‘Evangeline’ increased as seed root density increased at a grea...
Field studies were conducted in 2009 at Clinton, NC and 2014 at Pontotoc, MS to determine the inf... more Field studies were conducted in 2009 at Clinton, NC and 2014 at Pontotoc, MS to determine the influence of simulated glyphosate drip on sweetpotato yield and quality. Treatments consisted of three glyphosate solution (140 g ae L–1) drip volumes (0.16, 0.32 and 0.48 ml) by four application timings [(4 wk after transplanting (WAP); 6 WAP; 8 WAP; and 4 WAP followed by (fb) 6 WAP fb 8 WAP]. A non-treated check was included for comparison. Visual sweetpotato injury consisted of chlorosis at the shoot tips approximately 1 wk after treatment fb necrosis and stunting. At 6 WAP and 8 WAP, sweetpotato injury following glyphosate applied 4 WAP was 71 and 65%, respectively. Injury from glyphosate applied 4 WAP fb 6 WAP was 78%. Injury from glyphosate applied 6 WAP was 26% at 8 WAP. In 2009, jumbo, no. 1, canner, and marketable yield of the non-treated check were two to three times greater than glyphosate treatments (0.16, 0.32, 0.48 ml). Likewise, yield of the non-treated check was substantiall...
Palmer amaranth (Amaranthus palmeri S. Wats.) is a highly competitive weed that can be difficult ... more Palmer amaranth (Amaranthus palmeri S. Wats.) is a highly competitive weed that can be difficult to manage in many cropping systems. Research to date has not quantified the growth and development of A. palmeri in a manner that allows direct comparisons across cropping systems. Research was conducted to compare the growth, development, and seed production of A. palmeri when competing with corn (Zea mays L.), cotton (Gossypium hirsutum L.), peanut (Arachis hypogaea L.), and soybean [Glycine max (L.) Merr.] when emerging with crops or emerging three weeks after crops emerge. Regardless of when A. palmeri emerged, seed production was greatest and similar in cotton and peanut and exceeded that of corn and soybean; seed production in soybean exceeded that of corn. However, seed production was approximately 10-fold greater when A. palmeri emerged with crops compared with emergence three weeks later. These results illustrate the importance of controlling weeds during the first three weeks o...
There has been renewed interest in using fluridone herbicide to aid in control of glyphosateresis... more There has been renewed interest in using fluridone herbicide to aid in control of glyphosateresistant Palmer amaranth (Amaranthus palmeri S. Watson) in cotton (Gossypium hirsutum L.). Section 18 Emergency Use Exemptions for fluridone in cotton have been granted recently in several states and the manufacturer is pursuing federal registration. Fluridone has long persistence in soil, leading to questions about rotational crop response. Field experiments were conducted in North Carolina to evaluate the potential for fluridone to carry over to corn (Zea mays L.), peanut (Arachis hypogaea L.), grain sorghum [Sorghum bicolor (L.) Moench.], and soybean [Glycine max (L.) Merr.] grown in rotation with fluridone-treated cotton. Fluridone at 0, 280, 420, 560, 840, and 1120 g ai ha -1 was applied preemergence to cotton and rotational crops were planted the following spring. The fluridone rates were well above proposed use rates. Only minor visible injury to cotton was observed and cotton yield w...
MEYERS, STEPHEN LAWRENCE. Interference and Control of Palmer Amaranth (Amaranthus palmeri) in Swe... more MEYERS, STEPHEN LAWRENCE. Interference and Control of Palmer Amaranth (Amaranthus palmeri) in Sweetpotato. (Under the direction of Katie Jennings and Jonathan Schultheis.) The most common and troublesome weed in North Carolina sweetpotato is Palmer amaranth, an upright, branching, annual weed with rapid growth and high fecundity. Field studies were conducted in 2007 and 2008 to develop a Palmer amaranth management program in sweetpotato using density models to establish thresholds, and herbicides for control. Palmer amaranth was established at 0, 0.5, 1.1, 1.6, 3.3, and 6.5 plants/m within the sweetpotato row and densities maintained season-long. Jumbo, no. 1, and marketable sweetpotato yield loss ranged from 56 to 94%, 30 to 85%, and 36 to 81%, respectively for 0.5 to 6.5 Palmer amaranth/m. Yield loss displayed a positive linear relationship with Palmer amaranth light interception. Light intercepted by the Palmer amaranth canopy increased linearly from 0.5 to 6.5 plants/m and was g...
Studies were conducted in 2012 and 2013 to compare Evangeline to various sweetpotato (Ipomoea bat... more Studies were conducted in 2012 and 2013 to compare Evangeline to various sweetpotato (Ipomoea batatas) varieties (Bayou Belle, Beauregard, Bonita, Covington, NC05-198, and Orleans) for commercial production in North Carolina. In another study, microwaved and oven-baked ‘Evangeline’ and ‘Covington’ sweetpotato roots were subjected to analysis of chemical and physical properties [color, dry matter (DM), texture, and sugar] and to sensory evaluation for determining consumer acceptance. ‘NC05-198’ produced the highest no. 1 grade sweetpotato 600 bushels [bu (50 lb)] per acre and total marketable storage root yield was similar to ‘Bayou Belle’ and ‘Beauregard’ (841, 775, and 759 bu/acre, respectively). No. 1 and marketable root yields were similar between ‘Orleans’ and ‘Beauregard’. However, ‘Orleans’ produced more uniform roots than ‘Beauregard’, in which the latter had higher cull production. ‘Evangeline’ was comparable to no. 1 yield of ‘Bayou Belle’, ‘Orleans’, and ‘Covington’, which...
Lab and greenhouse studies were conducted to evaluate the effects of chemical treatments applied ... more Lab and greenhouse studies were conducted to evaluate the effects of chemical treatments applied to Palmer amaranth seeds or gynoecious plants retaining seeds on seed germination and quality. Treatments applied to physiologically mature Palmer amaranth seed included acifluorfen, dicamba, ethephon, flumioxazin, fomesafen, halosulfuron, linuron, metribuzin, oryzalin, pendimethalin, pyroxasulfone, S-metolachlor, saflufenacil, trifluralin, and 2,4-D plus crop oil concentrate applied at 1 and 2× the suggested use rates from the manufacturer. Germination was reduced by 20% from 2,4-D, 15% from dicamba, and 13% from halosulfuron and pyroxasulfone. Dicamba, ethephon, halosulfuron, oryzalin, trifluralin, and 2,4-D decreased the average seedling length by at least 50%. Due to the observed effect of dicamba, ethephon, halosulfuron, oryzalin, trifluralin, and 2,4-D, these treatments were applied to gynoecious Palmer amaranth inflorescence at the 2× registered application rates to evaluate their...
Palmer amaranth (Amaranthus palmeri S. Watson) populations resistant to acetolactate synthase-inh... more Palmer amaranth (Amaranthus palmeri S. Watson) populations resistant to acetolactate synthase-inhibiting (ALS) herbicides and glyphosate are fairly common throughout the state of North Carolina (NC). This has led farm managers to rely more heavily on herbicides with other sites of action (SOA) for A. palmeri control, especially protoporphyrinogen oxidase- and glutamine synthetase inhibitors. In the fall of 2016, seeds from A. palmeri populations were collected from the NC Coastal Plain, the state’s most prominent agricultural region. In separate experiments, plants with 2 to 4 leaves from the 110 populations were treated with field use rates of glyphosate, glufosinate-ammonium, fomesafen, mesotrione, or thifensulfuron-methyl. Percent visible control and survival were evaluated three weeks after treatment. Survival frequencies were highest following glyphosate (99%) or thifensulfuron-methyl (96%) treatment. Known mutations conferring resistance to ALS inhibitors were found in populat...
Field trials were conducted in North Carolina in 2017 and Louisiana and Mississippi in 2018 to de... more Field trials were conducted in North Carolina in 2017 and Louisiana and Mississippi in 2018 to determine the effect of pre-transplanting applications of diquat on sweetpotato crop tolerance, yield, and storage root quality. At North Carolina treatments consisted of two rates of diquat (560 or 1,120 g ai ha-1) alone or mixed with 107 g ai ha-1 flumioxazin and applied 1 d before transplanting (DBP), sequential applications of diquat (560 or 1,120 g ha-1) 1 and 17 DBP, 107 g ha-1 flumioxazin alone, and a non-treated check. At Louisiana and Mississippi treatments consisted of diquat (560 or 1,120 g ha-1) applied 1 DBP either alone or followed by (fb) rehipping rows or 107 g ha-1 flumioxazin immediately prior to transplanting. Additional treatments included 546 g ha-1 paraquat applied 1 DBP and a non-treated check. At North Carolina injury was ≤ 3% for all treatments through 23 DAP, and no injury was observed after 23 DAP. Visual sweetpotato stunting pooled across Mississippi and Louisia...
A research gap exists on the effects of irrigation, transplant (nonrooted stem cuttings) size, an... more A research gap exists on the effects of irrigation, transplant (nonrooted stem cuttings) size, and planting depth on sweetpotato (Ipomoea batatas) plant survival and storage root yield. Field studies were conducted in 2012 and 2013 to determine the effects of preplant irrigation, planting depth, and transplant size on sweetpotato plant stand, storage root number, and yield. Treatments included four transplant sizes (3.7, 6.3, 8.5, and 10.7 inches), two planting depths (2 and 6 inches), and preplant irrigation or nonirrigation. Overall, plant stand, storage root number, and yield were greater when transplants of size ≥6.3 inches were planted 6 inches deep as compared with transplants planted 2 inches deep. The use of preplant irrigation had an overall positive impact on plant stand, storage root number, and yield under dry soil conditions. When moisture was readily available, neither plant stand nor storage root numbers were affected by the application of irrigation as observed in 20...
Field studies were conducted in 2016 and 2017 in Clinton, NC, to determine the interspecific and ... more Field studies were conducted in 2016 and 2017 in Clinton, NC, to determine the interspecific and intraspecific interference of Palmer amaranth (Amaranthus palmeri S. Watson) or large crabgrass [Digitaria sanguinalis (L.) Scop.] in ‘Covington’ sweetpotato [Ipomoea batatas (L.) Lam.]. Amaranthus palmeri and D. sanguinalis were established 1 d after sweetpotato transplanting and maintained season-long at 0, 1, 2, 4, 8 and 0, 1, 2, 4, 16 plants m−1 of row in the presence and absence of sweetpotato, respectively. Predicted yield loss for sweetpotato was 35% to 76% for D. sanguinalis at 1 to 16 plants m−1 of row and 50% to 79% for A. palmeri at 1 to 8 plants m−1 of row. Weed dry biomass per meter of row increased linearly with increasing weed density. Individual dry biomass of A. palmeri and D. sanguinalis was not affected by weed density when grown in the presence of sweetpotato. When grown without sweetpotato, individual weed dry biomass decreased 71% and 62% from 1 to 4 plants m−1 row ...
Herbicide systems consisting of PRE, early POST, and late POST options arranged factorially were ... more Herbicide systems consisting of PRE, early POST, and late POST options arranged factorially were compared for control of sicklepod in narrow-row soybean with modified acetolactate synthase (ALS) (E.C.4.1.3.18). Other weeds present included common cocklebur and mixed infestations of entireleaf, ivyleaf, pitted, and tall morningglories. PRE options were alachlor or alachlor plus metribuzin plus chlorimuron. Early POST options included chlorimuron, chlorimuron plus thifensulfuron, and no herbicide applied 3 wk after planting. Late POST options were chlorimuron and no herbicide applied 5 wk after planting. POST herbicides were more effective than PRE herbicides on all weeds. Chlorimuron and chlorimuron plus thifensulfuron applied early POST were equally effective on these weeds and usually more effective than chlorimuron applied late POST. There was no advantage of two POST applications compared with a single early POST application. Greatest net returns were obtained in systems using on...
Tomato grafting is practiced worldwide as an innovative approach to manage stress from drought, w... more Tomato grafting is practiced worldwide as an innovative approach to manage stress from drought, waterlogging, insects, and diseases. Metribuzin is a commonly used herbicide in tomato but has potential to cause injury after application if plants are under stress. The influence of metribuzin on grafted tomato under drought-stress has not been studied. Greenhouse experiments were conducted in Raleigh, NC to determine the tolerance of drought-stressed grafted and non-grafted tomato to metribuzin. The tomato cultivar ‘Amelia’ was used as the scion in grafted tomato, and for the non-grafted control. Two hybrid tomato ‘Beaufort’ and ‘Maxifort’ were used as rootstocks for grafted plants. Drought-stress treatments included: no drought-stress; 3 d of drought-stress before metribuzin application with no drought-stress after application (3 d DSB); and 3 d of drought-stress before metribuzin application with 3 d of drought-stress after application (3 d DSBA). Metribuzin was applied at 550 g ai h...
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