Several formulations of the essential element manganese (Mn) are commercially available for application to peanut (
Manganese (Mn) is an essential element needed for peanut (
A variety of commercial formulations of Mn are available, with the range of elemental Mn applied per unit area varying considerably when these products are applied at the manufacturer's suggested use rates. Furthermore, some manufacturers with lower concentrations of manganese claim that absorption of Mn is enhanced by their formulation. Determining the relative difference in the amount of elemental Mn accumulation in plant tissue following foliar application of Mn fertilizer is important in determining which formulation is the most beneficial for use in peanut. The influence of pesticides and adjuvants on absorption of boron, a micronutrient often applied topically to peanut, into peanut leaves has been reported previously (Jordan
Determining compatibility of agrochemicals is important when developing pest management strategies for peanut. Interactions of graminicides with herbicides that control broadleaf weeds and purple nutsedge (
Reduced herbicide efficacy may be a result of chemical interactions in the spray solution. Cations in the spray solution can adversely affect efficacy of glyphosate and sethoxydim (Nalewaja
Timing of application of fungicides, insecticides, and Mn often coincide, and determining interactions of these agrochemicals will be important in making good decisions on pest management in peanut. Although research has demonstrated that boron does not affect efficacy of fungicides (
Determining which formulations of Mn provide the most elemental Mn in plants will help when attempting to correct deficiencies with a wide range of commercially available products. Additionally, determining if Mn affects pesticide efficacy or if agrichemicals will affect Mn absorption can assist practitioners as they develop appropriate production and pest management strategies for peanut. Research was conducted to determine (1) differences in Mn accumulation in peanut leaf tissue when various commercially available Mn products are applied, (2) influence of pesticides and adjuvant on Mn accumulation in peanut, and (3) the effect of Mn on disease and weed control when co-applied with fungicides, herbicides, and insecticide.
The experiment was conducted in two separate fields located near Edenton, NC during 2001 both on a Roanoke silt loam soil (clayey, mixed, thermic, Typic Ochraquepts) and in two separate fields at the Upper Coastal Plain Station during 2007 on a Goldsboro loamy sand soil (fine-loamy, mixed, semiactive, thermic, Typic Hapludults). The cultivar NC-V 11 (2001) (Wynne
Treatments in 2001 consisted of no Mn, a dry formulation of Mn sulfate (Techmangum®, 19% S and 32% Mn sulfate monohydrate, Erachem Mexico, Veracruz, Mexico) at 2.8 kg/ha (17.5% actual Mn), and a liquid complex of Mn containing 5.0% Mn formulated at 1.10 kg Mn/L (Manganese Xtra©, Custom Agricultural Formulations, Fresno, CA) at 0.12 L/ha. In 2007, treatments consisted of no Mn or Mn formulations containing 8% Mn (NutriSol 9% Manganese™, Coastal Agrobusiness, Inc., Greenville, NC) at 1.16 L/ha or Mn sulfate (Man-Gro DF®, Tetra micronutrients, The Woodlands, TX) at 2.8 kg/ha (17.4% actual Mn). These rates are consistent with those recommended by the manufacturer and typically applied by peanut producers in North Carolina. Manganese was applied during flowering in late July.
In 2001, ten leaves consisting of four leaflets per leaf were removed at random from the top one-third of the peanut canopy 6 h (0.25 d), 2, and 14 d after application and were subjected to a 30 second leaf wash in 1 L tap water. Stems and pods were removed from three randomly selected plants within a plot for Mn determination 14 d after application. In 2007, ten leaves were removed from each plot 7 d after application as described previously and subjected to a 30 second wash in 1 L tap water. Leaf, stem, and pod tissue were dried and ground to pass through a 1 mm screen prior to Mn concentration determination using a Perkin Elmer 3300 Argon Plasma Emission Spectrophotometer (Perkin Elmer, Sulton, CN).
In both experiments, Mn was applied using a CO2-pressurized backpack sprayer calibrated to deliver 145 L/ha using 8002 regular flat fan nozzles (Spraying Systems Co., Wheaton, IL) at 275 kPa. Adjuvant was not included. The experimental design was a randomized complete block with treatment replicated 3 or 4 times. Data for Mn accumulation (mg Mn/kg tissue) were subjected to analyses of variance and means separated using Fisher's Protected LSD test at P ≤ 0.05.
Experiments were conducted during 2008 at the Peanut Belt Research Station in two separate fields with the peanut cultivar Perry (Isleib
In one experiment, treatments consisted of a dry formulation of Mn (Super Mangro) at 2.8 kg/ha (17.4% Mn) applied alone or with azoxystrobin (230 g ai/ha), chlorothalonil (1,260 g ai/ha), pyraclostrobin (175 g ai/ha), and tebuconazole (230 g ai/ha). Manganese was also applied with these fungicides combined with the insecticide lambda cyhalothrin at 18 g ai/ha. Additional treamtments included lambda cyhalothrin and Mn applied in mixture without fungicide and a no-Mn control was included. In a second experiment, treatments consisted of the same formulation and rate of Mn applied alone or with nonionic surfactant (Induce nonionic surfactant, Helena Chemical Co., Memphis, TN) at 0.25% (v/v), crop oil concentrate (Agri-Dex nonionic spray adjuvant™, Helena Chemical Co., Memphis, TN) at 1.0% (v/v), clethodim at 110 g ai/ha plus crop oil concentrate, imazapic at 70 g ai/ha plus nonionic surfactant, lactofen at 280 g ai/ha plus crop oil concentrate, and 2,4-DB at 280 g ai/ha without adjuvant. A non-treated control was included in both experiments. Treatments were applied using a CO2-pressurized backpack sprayer calibrated as described previously.
The experimental design was a randomized complete block with four replications. Twenty leaves that were present at the time of application were removed from the top half of the canopy 7 d after application. Leaves were subjected to a one minute wash in tap water as described previously. Leaf tissue was blotted, air dried, and the concentration of Mn determined as descried previously. Data for Mn accumulation (mg Mn/kg tissue) were subjected to analysis of variance and means were separated using Fisher's Protected LSD test at p ≤ 0.05.
The experiment was conducted at the Cherry Research Farm located near Goldsboro, NC in 2001 on a Wickam sandy loam (fine-loamy, mixed, semi-active, thermic, Typic Hapludults). The experiment was also conducted at the Central Crops Research Station located near Clayton, NC in 2002 on a Geliad sandy loam soil (clayey, kaolinitic, thermic, Aquic Hapludults). Experiments were established in tilled fallow areas without a peanut crop. Plot size was 2 by 5 m.
In the first set of experiments at Goldsboro during 2001, treatments consisted of clethodim (140 g/ha), imazapic (70 g /ha), imazethapyr (70 g ai/ha), sethoxydim (220 g ai/ha), and 2,4-DB (220 g/ha) applied alone, with dry manganese sulfate (Techmangum®), or with a liquid formulation (Manganese Xtra©) at rates described previously. Herbicides were applied in separate experiments and were repeated in different fields during the same year. Imazethapyr was applied when Palmer amaranth was 40 to 60 cm in height. Imazapic, imazethapyr, and 2,4-DB were applied when sicklepod was 15 cm in height. Tall morningglory had 6 to 10 leaves when imazapic was applied. Clethodim and sethoxydim were applied to corn that was 25 cm in height.
In a second set of experiments conducted during 2007, common ragweed control by lactofen at 280 g ai/ha and large crabgrass control by clethodim at 140 g/ha were compared in separate experiments at the Upper Coastal Plain Research Station near Rocky Mount on the Goldsboro loamy sand soil described previously. The experiment was conducted in two adjacent fields and herbicides were applied alone or with manganese sulfate (Man-Gro DF®) at 2.8 kg/ha or liquid Mn (NutriSol 9% Manganese™) at 1.16 L/ha when common ragweed was 15 to 20 cm in height and large crabgrass was 10 to 15 cm in height.
Crop oil concentrate (Agri-Dex spray adjuvant™) at 1.0% (v/v) was applied with clethodim and sethoxydim. Nonionic surfactant (Induce nonionic surfactant™) at 0.25% (v/v) was applied with imazapic, imazethapyr, lactofen, and 2,4-DB. Treatments were applied using a CO2-pressurized backpack as described previously.
Visual estimates of percent weed control were determined 2 wk after application using a scale of 0 to 100% where 0 = no control and 100 = complete control. Foliar chlorosis, necrosis, and plant stunting were used when making the visual estimates. The experimental design was a randomized complete block with 3 or 4 replications. Means for visual estimates of percent control were separated using Fisher's Protected LSD Test at p ≤ 0.05.
The experiment was conducted during 2008 at the Peanut Belt Research Station in two separate fields with the peanut cultivar Perry. Plot size was one row (96-cm spacing) by 5 m with one non-treated row separating treated rows.
Treatments consisted of a dry formulation of Mn (Man-Gro DF®) applied alone at 2.8 kg/ha, with the fungicides azoxystrobin (230 g/ha), chlorothalonil (1,260 g/ha), pyraclostrobin (175 g/ha), and tebuconazole (230 g/ha), and with these fungicides co-applied with the insecticide lambda cyhalothrin at 18 g/ha. Fungicides and lambda cyhalothrin were also applied alone. A non-treated control was also included. Treatments were applied using a CO2-pressurized backpack sprayer as described previously.
The experimental design was a randomized complete block with four replications. The percentage of peanut canopy defoliated due to early leaf spot caused by
In 2001, the concentration of Mn in leaf tissue was the highest when manganese sulfate was applied regardless of harvest date (
Manganese (Mn) accumulation in peanut leaf leaves, stems, and pods when applied as two Mn formulations during 2001.a
Manganese (Mn) accumulation in peanut tissue 7 days after application of two Mn formulations during 2007. a
These data suggest that liquid formulations of Mn applied at the manufacturer's suggested use rate do not result in increases in Mn accumulation in all instances. In contrast, Mn sulfate at the rate recommended by the manufacturer consistently increased the amount of Mn in leaf tissue. This result was not surprising when comparing the amount of Mn applied in these formulations in 2001 (
The concentration of Mn in tissue following application of Mn with the adjuvants crop oil concentrate or nonionic surfactant or with clethodim, imazapic, lactofen, or 2,4-DB applied with the appropriate adjuvant was higher than Mn concentration in non-treated peanut (
Influence of adjuvants and herbicides on manganese (Mn) accumulation in peanut leaves 1 wk after application in 2008.a
Absorption of Mn was higher when Mn was applied with fungicides alone or with lambda cyhalothrin compared with Mn alone (
Influence of fungicides and the insecticide lambda cyhalothrin on manganese (Mn) accumulation in peanut leaves 1 wk after application in 2008.a
Corn control by clethodim and sethoxydim; large crabgrass control by clethodim; Palmer amaranth control by imazethapyr; sicklepod control by imazapic, imazethapyr, and 2,4-DB; and tall morningglory control by imazapic was not affected by Mn regardless of formulation (
The highest level canopy defoliation was noted when fungicide was not applied (
Weed control with postemergence herbicides applied alone or with three formulations of manganese (Mn).a,b
Common ragweed and large crabgrass control by herbicides applied alone or with two manganese (Mn) formulations during 2007.a
Influence of manganese (Mn) and the insecticide lambda cyhalothrin on peanut canopy defoliation in 2008.a
Collectively, results from these experiments suggest the amount of Mn in the formulated product and the application rate are the determining factors for increasing Mn concentration in peanut leaves. Growers should select a product that delivers adequate amounts of Mn when applications are needed to correct a Mn deficiency. In most cases, fungicides and insecticides did not affect Mn accumulation in leaf tissue. In contrast, adjuvants alone or with herbicides often increased Mn accumulation compared with Mn alone. Manganese did not affect efficacy of the herbicides clethodim, imazapic, imazethapyr, lactofen, sethoxydim, or 2,4-DB or the fungicides azoxystrobin, chlorothalonil, pyraclostrobin, or tebuconazole. Therefore, growers can apply these products simultaneously without concern of reduced control of weeds and disease. However, Mn sulfate reduced efficacy of lactofen on common ragweed; therefore these products should be not be co-applied to avoid reduced weed control.
Assistance was provided by staff at the Central Crops Research Station, Cherry Research Farm, the Peanut Belt Research Station, the Upper Coastal Plain Research Station, and by the North Carolina Department of Agriculture and Consumer Services. Boone Farm Supply provided the liquid Mn formulation Manganese Xtra©. The other Mn formulations were purchased locally. This research was supported financially by the North Carolina Peanut Growers Association, Inc. and the USAID Peanut CRSP LAG-G-00-96-90013-00.
Current address of S. R. Lancaster: Department of Plant and Soil Sciences, Oklahoma State University, 368 Ag Hall, Stillwater, OK 74078.