- Turnips -

TURNIPS:  Brassica rapa L., ‘All Top’

Green peach aphid (GPA): Myzus persicae (Sulzer)           

CONTROLLING GREEN PEACH APHID ON TURNIP GREENS, OKLAHOMA, 1999.  ‘Alltop’ turnips were direct seeded to a field at the Wes Watkins Agricultural Research and Extension Center, Lane, OK on 15 Sep 1999.  Experimental design was a RCB with 10 treatments and 5 replicates.  Plots were 72 inches wide with 2 rows and 20 ft long and had 20 ft alleys between plots in rows.  Rows were precision seeded to a stand of 3 inches between plants.  Foliar applications of insecticides were made with a tractor-mounted sprayer with an output of 20 gal/acre at 40 psi.  The spray boom was equipped with hollow cone nozzles positioned with one nozzle over each row and nozzles directed into the rows at an angle from drops located on the boom.  Applications were made to the plots on 4 Nov.  Number of green peach aphids was determined by counting all aphids on 3 plants in each plot.

Aphid populations were moderately abundant and numbers increased over time from 4 to 18 Nov.  All insecticides applications provided signficant reductions in aphid numbers except Neemix.  Acetamiprid and Provado provided excellent control up to 14 DAT.

Table 1.

                                                                        Mean number of aphids

Treatment                     Rate/acre                     7 DAT             14 DAT

acetamiprid                   0.075                             14  bc                 1        e

Provado                       3.75 oz actual                   3    c                   2        e

Aphistar                       0.12                               29  bc                17   cde

pirimicarb                     0.33                               12  bc                21     de

lambda cyhalothrin            0.03                               24  bc                34     de

Fulfill                            2.75 oz actual                 60 ab                 46  bc

thiomethoxam               0.02                               17 abc    66   cde

endosulfan                    0.75                               73  bc                87  bcd

Neemix 4.5                  1 pint actual               218 abc       267 ab

untreated                      -                                   189 a               413 a              

Rate/acre provided as lb AI unless otherwise noted.

Data reported as actual mean number per 3 plants but analysis conducted using numbers converted to (log₁₀ + 1) values and analysed using LSD at P = 0.1.

TURNIPS:  Brassica rapa L., ‘All Top’                                              J.V. Edelson, J. Duthie, W. Roberts

            Green peach aphid (GPA): Myzus persicae (Sulzer)                        Oklahoma State Univ./WWAREC

                                                                                                            Lane, OK 74555

EFFECT OF LEPIDOPTERA SPECIFIC INSECTICIDES ON APHID POPULATIONS ON TURNIP GREENS, OKLAHOMA, 1999:  ‘Alltop’ turnips were direct seeded to a field at the Wes Watkins Agricultural Research and Extension Center, Lane, OK on 15 Sep.  Experimental design was a RCB with 5 treatments and 5 replicates.  Plots were 72 inches wide with 2 rows and 20 ft long and had 20 ft alleys between plots in rows.  Rows were precision seeded to a stand of 3 inches between plants.  Foliar applications of insecticides were made with a tractor-mounted sprayer with an output of 20 gal/ acre at 40 psi.  The spray boom was equipped with hollow cone nozzles positioned with one nozzle over each row and nozzles directed into the rows at an angle from drops located on the boom.  Applications were made to the plots on 4 Nov.  Number of green peach aphids was determined by counting all aphids on 3 plants in each plot.

This trial was intended as an evaluation of various insecticides for controlling lepidopteran species which were practically non-existant.  Aphids were abundant and the data provides insight into effects of the insecticides on aphid populations. Spinosad applications resulted in significantly reduced numbers of aphids in comparison to the untreated plots.  The other insecticides provided reductions, albiet statistically non-significant, in aphid numbers.  Thus applications of these insecticides should result in no increases or ‘rebounds’ in aphid populations when used to control lepidoptera and spinosad applications should result in reductions in aphid numbers. 

Table 1.

                                                                        Mean number aphids / 3 plants

Treatment                                 Rate/acre         5 DAT             12 DAT                           

untreated                                  -                       240 a               575 a

lambda cyhalothrin                    0.03                   77 ab             203 ab

Confirm                                    16 oz                  65 ab             343 ab

Proclaim                                   4.8 oz                 42 ab             348 ab

spinosad                                   0.13                   27   b               63   b                                    

Rates/acre are reported as lb AI unless otherwise noted.

Mean numbers of aphids are reported in the table, but analyses were conducted using log₁₀+1 values with a LSD at P=0.1.

TURNIPS:  Brassica rapa L., ‘All Top’                                              J.V. Edelson, J. Duthie, W. Roberts

            Green peach aphid (GPA): Myzus persicae (Sulzer)                        Oklahoma State Univ./WWAREC

                                                                                                            Lane, OK 74555

SOIL INSECTICIDES FOR CONTROLLING APHIDS, OKLAHOMA, 1999:  ‘Alltop’ turnips were direct seeded to a field at the Wes Watkins Agricultural Research and Extension Center, Lane, OK on 15 Sept 1999.  Experimental design was a RCB with 5 treatments and 5 replicates.  Plots were 72 inches wide with 2 rows and 20 ft long and had 20 ft alleys between plots in rows.  Rows were precision seeded to a stand of 6 inches between plants.  Applications were made using a tractor-mounted sprayer with flood jet nozzles directed over the seed furrow at a rate of 20 gal/acre.  Applications were made to the plots 20 Sept.  Number of green peach aphids was determined by counting all aphids on 3 plants in each plot.

Aphids were moderately abundant early (12 Oct), then decreased in abundance during the middle of the season and increased again at the end of the season as determined from surveys in the untreated plots.   Results of regression analysis of aphid response to rates of thiamethoxam indicated significant rate responses for data collected 28 Oct, 2  and 9 Nov.  Comparisons among the high rate of thiamethoxam, imidacloprid and the untreated plots indicated that both insecticides provided significant reductions in aphid numbers on 28 Oct, 2 , 9 and 18 Nov.  Imidacloprid provided greater reductions in aphid numbers on 18 Nov than did thiamethoxam.  The high rates of both insecticides provided good full season control of aphids. 

Tabel 1.                        Rate                             Mean number of aphids / 3 plants

Treatment                     g AI /330 row ft            28 Oct            2 Nov            9 Nov

untreated                      0.0                               14        7          124     

thiamethoxam               0.1                                 3          2           31       

thiamethoxam               0.5                                 3          1            8         

thiamethoxam               1.0                                 1          0.4          2           

P>|T| for regression on 28 Oct, intercept 0.001, rate 0.03.  P>|T| for regression on 2 Nov, intercept 0.001, rate 0.1.  P>|T| for regression on 9 Nov, intercept 0.001, rate 0.003.

Tabel 2.                        Rate                             Mean number of aphids / 3 plants

Treatment                     g AI /330 row ft            12 Oct            19 Oct            28 Oct 2 Nov  9 Nov 18 Nov

untreated                      0.0                               33            2            14a         7a        124a            169a

imidacloprid                  1.5                               15            1            4 b       0.4 b       6 b           3  c

thiamethoxam               1.0                                 9          1            1 b       0.4 b       2 b         37 b

Numbers in a column followed by the same letter or without letters are not significantly different, LSD, P=0.1.

TURNIPS:  Brassica rapa L., ‘All Top’                                              J.V. Edelson, J. Duthie, W. Roberts

            Green peach aphid (GPA): Myzus persicae (Sulzer)                        Oklahoma State Univ./WWAREC

                                                                                                            Lane, OK 74555

SOIL APPLICATION OF INSECTICIDES TO CONTROL APHIDS, OKLAHOMA, 2000:  ‘Alltop’ turnips were direct seeded to a field at the Wes Watkins Agricultural Research and Extension Center, Lane, OK on 19 Apr 2000.  Experimental design was a RCB with 5 treatments and 5 replicates.  Plots were 72 inches wide with 2 rows and 20 ft long and had 20 ft alleys between plots in rows.    Applications were made to plots on 1 May, using a tractor-mounted sprayer with flood jet nozzles directed over the seed furrow at a rate of 20 gal/ acre.  Number of aphids on 3 plants per plot were recorded at 7-day intervals.  Bioassays were conducted by collecting terminal leaves from plants in each plot, cutting tissue discs from the leaves and placing them into petri dishes with moist filter paper.  Ten large, late-instar green peach aphids from a laboratory maintained susceptible culture were placed on each leaf disc and examined after 24 hrs to determine mortality.

Aphids were virtually non-existant in the field plots during the growing season.  Results from the bioassays conducted 15 May indicated no significant rate response but results from those conducted on 31 May indicated a significant response in aphid mortality as a function of rate of thiamethoxam (Table 1).  Comparison of aphid mortality among insecticides indicated a significant increase in mortality in bioassays conducted using the tissue collected 31 May (Table 2).  Results indicate that there is a significant rate response for thiamethoxam and that thiamethoxam and imidacloprid are present, active and can cause significant aphid mortality up to harvest in plants treated at seeding. 

Table 1.                                                31 May

Treatment and rate (oz AI/acre)            No. dead aphids

Untreated                     0.0                   1.0

Thiamethoxam            0.01                 1.4

Thiamethoxam            0.02                 2.4

Thiamethoxam            0.04                 5.6                                                      

Based on regression analysis, intercept = 0.5 (P>|T| = 0.3) and rate = 53.7 (P>|T| = 0.0001) with R² = 0.61.

Table 2.

                                                            No. dead aphids     

Treatment and rate (oz AI/acre)               15 May                       31 May

Untreated                     0.0                   2.4                   1.4 a

Thiamethoxam            0.04                 3.6                   5.6  b

Imidacloprid                 0.05                 2.8                   7.4  b                          

Mean no. dead aphids in a column followed by the same letter or no letter are not significantly different, LSD, P=0.1.

TURNIPS:  Brassica rapa L., ‘All Top’                                              J.V. Edelson, J. Duthie, W. Roberts

            Green peach aphid (GPA): Myzus persicae (Sulzer)                        Oklahoma State Univ./WWAREC

                                                                                                            Lane, OK 74555

‘BIORATIONAL’ INSECTICIDES FOR CONTROLLING APHIDS, OKLAHOMA, 2000:  ‘Alltop’ turnips were direct seeded to a field at the Wes Watkins Agricultural Research and Extension Center, Lane, OK on 19 Apr 2000.  Experimental design was a RCB with 4 treatments and 5 replicates.  Plots were 72 inches wide with 2 rows and 20 ft long and had 20 ft alleys between plots in rows.    Applications were made to plots on 1 May, using a tractor-mounted sprayer with 3 hollow cone nozzles directed over each row, one nozzle directly over the row and one on each side on 10 inch drops directed at angles into the rows and applying mixtures at a rate of 20 gal/ acre.  Number of aphids on 3 plants per plot were recorded at 7 day intervals. 

            Aphid populations were very low and decreased in abundance in untreated plots from 12 May to 23 May.  None of the insecticides applied to plots resulted in decreased abundance of aphids in comparison to untreated plots at 3 days after the first application of insecticides.  These results concur with previous research indicating that these insecticides are not effective for killing green peach aphids on turnip plants grown for leafy greens.

Table 1.

                                                            No. aphids / plant   

Treatment                     Rate                 15 May            26 May

Untreated                     -                         9 a                   3 a

Neemix 4.5                  1 pint/acre            15 a                   2 a

Pyronyl             12 oz/acre   9 a                   3 a

M-Pede                       2.5 oz/gallon            16 a                   2 a                                                    

Mean number of aphids / 3 plants in the same column followed by the same letter are not significantly different, LSD, P=0.1.  Numbers in the table are arithmetic means but analyses were conducted using means transformed to log₁₀ values.

TURNIPS:  Brassica rapa L., ‘All Top’                                              J.V. Edelson, J. Duthie, W. Roberts

            Green peach aphid (GPA): Myzus persicae (Sulzer)                        Oklahoma State Univ./WWAREC

                                                                                                            Lane, OK 74555

CONTROLLING APHIDS WITH FOLIAR APPLICATIONS OF INSECTICIDES, OKLAHOMA, 2000:  ‘Alltop’ turnips were direct seeded to a field at the Wes Watkins Agricultural Research and Extension Center, Lane, OK on 19 Apr 2000.  Experimental design was a RCB with 10 treatments and 5 replicates.  Plots were 72 inches wide with two rows and 20 ft long and had 20 ft alleys between plots in rows.  Rows were precision seeded to a stand of 3 inches between plants.  Foliar applications of insecticides were made with a tractor-mounted sprayer with an output of 20 gal/acre at 40 psi.  The spray boom was equipped with hollow cone nozzles positioned with one nozzle over each row and nozzles directed into the rows at an angle from drops located on the boom.  Applications were made to the plots on 12 and 23 May.  Number of green peach aphids was determined by counting all aphids on three plants in each plot.

Aphids were not abundant during the growing season.  Aphistar, Provado and Pirimor provided significant reductions in aphids at 3 DAT.  Residual activity could not be determined because aphids populations in all plots including the untreated declined by 23 May.

Table 1.

                                                            Mean no. aphids/plant

Treatment and rate                              15 May           

Untreated                     -                       7a                   

Aphistar                       8 oz/acre 1    d               

Provado 1.6                 3.75 oz/acre 1    d               

Fulfill                            1.42 oz/acre 2 bcd              

Warrior SC                  0.03                 2 bcd              

Acetameprid                 0.75                 3abc                

Thiamethoxam 25WG 1.5 oz/acre 2 bcd              

Thiamethoxam 25WG 3.0 oz/acre 3abc                

Dibrom             2.0                   5ab                 

Pirimor 50DF               16 oz/acre 1     d                                                              

Mean no. aphids / plant in the same column followed by the same letter are not significantly different, LSD, P=0.1.

Rate provided as lb AI / acre unless otherwise indicated.

TURNIPS:  Brassica rapa L. ‘All Top’                                               

            Green peach aphid (GPA); Myzus persicae (Sulzer)                       

            EVALUATION OF INSECTICIDE EFFICACY ON TURNIPS USING A BIOASSAY, 1998:  Turnip seed was planted on 6 Sep at the AREC, Lane, OK.  The experimental design was a RCB with 5 replicates and 6 treatments. Plots were 2 rows wide (72 inches) and 20 ft long with 15 ft alleys cut between plots. Plots were treated with insecticides using a tractor-mounted hydraulic sprayer with nozzles mounted on vertical extensions and a broadcast application of 72 inches from 6 hollow-cone nozzles applying 37 gal/acre at 40 psi.  Water carrier was adjusted to different pH levels as indicated and all treatments with oil were mixed at a rate of 1 pint of Prime Ag emulsifiable vegetable oil / acre.  Plots were treated on 30 Oct and 12 Nov.  Three plants in each plot were examined 3 days after each application and number of aphids recorded.  A terminal, fully expanded leaf was collected from one plant in each plot.  A one-inch diameter leaf disc was cut from each leaf and placed in a petri dish with the abaxial surface up.  Ten GPA from a colony maintained in the laboratory on turnips were then placed on each leaf disk.  Aphids were allowed to feed on disks for 24 hr at 75^o F under a 24 hr photoperiod.  Disks were examined to determine mortality of aphids on 6 and 17 Nov.  To assess effects of treatments, the proportion of aphids that were dead was arcsin transformed and subjected to ANOV.  Non-transformed means are reported in the table.

            Aphids were not abundant enough in the field to determine treatment effects.  Results from bioassays indicated that all treatments with the exception of dimethoate on 17 Nov resulted in significant mortality of GPA relative to the untreated tissue.

Means in the same column followed by different letters are significantly different (P=0.1, LSD).

TURNIPS:  Brassica rapa L. ‘All Top’                                

  Green peach aphid (GPA); Myzus persicae (Sulzer)                                                                                  

            EVALUATION OF INSECTICIDE EFFICACY, 1999:  Turnip seed was planted in Apr at the AREC, Lane, OK.  The experimental design was a RCB with 5 replicates and 8 treatments. Plots were 2 rows wide (72 inches) and 20 ft long with 15 ft alleys cut between plots. Plots were treated with insecticides using a tractor mounted hydraulic sprayer with drops, with a broadcast application of 72 inches from 6 hollow-cone nozzles applying 37 gal/acre at 40 psi.  Plots were treated on 24 May and 5 Jun.  Water carrier was adjusted to different pH levels as indicated and all treatments with oil were mixed at a rate of 1 pint/acre of Prime Ag emulsifiable vegetable oil.  Three plants in each plot were examined 3 days after each application and number of aphids was recorded.  Data were analysed using a log10 transformation of aphid numbers and non-transformed means are reported.  Data were subjected to ANOV with a means separation test to compare treatment effects.

            GPA occurred in low abundance on 27 May and too few were recorded on 8 Jun to evaluate efficacy of treatments.  Each insecticide, with the exception of triazimate 1.4EW, resulted in significantly reduced GPA abundance in plots on 27 May in comparison to the untreated plots.  

Means in a column followed by the same letter are not significantly different, LSD, P=0.1.

TURNIPS:  Brassica rapa L., ‘All Top’                                 

  Green peach aphid (GPA); Myzus persicae (Sulzer)           

            NEONICOTINOID INSECTICIDE EFFICACY FOR APHID CONTROL, 1998: Turnip seed was planted on 8 Apr at the AREC, Lane, OK.  The experimental design was a RCB with 5 replicates and 5 treatments.  Plots were 1 row wide (36 inches) and 8.25 ft.  Plants in plots were treated using 1 qt of solution as a soil drench to the side of seedlings on 29 Apr.  Plots were surveyed to determine insect abundance on 13 May by examining 1 plant per plot and on 18 May by examining 3 plants per plot and recording GPA present.   Data were converted to a log10 value and subjected to ANOV and a means separation test to compare effects.  Non-transformed data means are noted in the table.

            GPA were moderately abundant on the first date of survey and declined in abundance thereafter.  Each treatment and rate resulted in significant reductions in aphids in comparison to the untreated plots.  No significant differences in reduction of aphids were noted among treatment rates of thiamethoxam.

Means in a column followed by the same letter did not differ significantly, LSD, P=0.1.

^aMean number of GPA per plant.

^bMean number of GPA per 3 plants.

TURNIPS:  Brassica rapa L., ‘All Top’                                 

  Green peach aphid (GPA); Myzus persicae (Sulzer)

            NEONICOTINOID INSECTICIDE EFFICACY FOR APHID CONTROL, 1999:  Turnip seed was planted in Apr at the AREC, Lane, OK.  The experimental design was a RCB with 5 replicates and 5 treatments.  Plots were 1 row wide (36 inches) and 8 ft long with 10 ft alleys between plots.  Plants in plots treated with soil applications were treated using 1 qt of solution as a soil drench to the side of seedlings just after plant emergence.   Plots with foliar applications of insecticides were treated on 18 May with a tractor-mounted sprayer applying 36 gal/acre at 40 psi with 3 hollow-cone nozzles set to broadcast applications over the row. Plots were surveyed to determine insect abundance on 7, 18 and 24 May by examining 3 plants per plot and recording all GPA present.  Data were transformed to log10 values prior to subjecting them to ANOV and means separation test.  Non-transformed means are reported in the table.

            Soil treatments with the neonicotinoid insecticides, thiamethoxam and imidacloprid, significantly reduced GPA on 7 May.  GPA abundance declined in the untreated plots thereafter.  The foliar application of methomyl and the soil application of imidacloprid significantly reduced GPA through 24 May.

Means in the same column followed by the same letters are not significantly different, P=0.1, LSD.