(F54)
SOYBEAN: Glycine max (L) Merrill, ‘NK S06-L6 RR’
EFFICACY OF FOLIAR APPLIED INSECTICIDES-FUNGICIDES AGAINST SOYBEAN APHIDS ON
SOYBEANS, 2006
Janet Knodel
North Dakota State University
Department of Entomology
202A Hultz Hall
Fargo, ND 58105
Phone: (701) 231-7581
Fax: (701) 231-8557
E-mail: [email protected]
Carl Bradley
North Dakota State University
Department of Plant Pathology
301 Walster Hall
Fargo, ND 58105
Phone: (701) 231-7056
Fax: (701) 231-7851
E-mail: [email protected]
Soybean aphid: Aphis glycines Matsumura
Efficacy of different insecticide-fungicide treatments was assessed for control of soybean aphid in research plots located on
the Olsen Farm in Colfax, ND. Soybeans were planted on 29 May using a seeding rate of 180,000 seeds/acre. Plots were 10
ft wide by 25 ft long in a RCB design with 15 treatments and four replicates. All applications were applied at R3 on 14 Jul
using a handheld CO2 boom sprayer at 40 psi, 15 gpa and XR8001VS nozzles. For aphid control, five plants per plot were
assessed by counting the number of aphids per plant at pre-spray (0 DAT), at 6 DAT on 20 Jul (R3), 11 DAT on 25 Jul
(R4), 26 DAT on 9 Aug (R5) and 32 DAT on 15 Aug (R5). Roundup (glyphosate) was applied post-emergence in late June
for weed control. Plots were harvested on 22 Sep using a small plot combine and yield (bu/acre) adjusted to 13% moisture.
Prior to analyses, data from 6, 11 and 32 DAT were transformed using log(x+1) and 26 DAT using arsine square root
percent. Variables were subjected to ANOVA and means compared using Fisher’s Protected LSD at the 5% significance
level.
Prior to the insecticide application, a mean of 190 aphids per plant were present in research plots and there were no
significant differences between treatments. At 6, 11 and 26 DAT, all insecticide and insecticide-fungicide treatments had
significantly lower numbers of aphids per plant than the untreated check and fungicide alone treatments. This indicates that
the tested insecticides and/or insecticide-fungicide combinations effectively controlled soybean aphids for 26 DAT.
Soybean aphid counts were not significantly different between the insecticide alone and the insecticide-fungicide
treatments, regardless of the DAT; however, Lorsban alone had higher numbers of aphids per plant compared to the
Lorsban-fungicide treatments at 6 DAT. This suggests some sort of synergistic reaction between Lorsban and those
fungicide combinations. General observations consist of Lorsban (organophosphate insecticide) having a quicker
knockdown and shorter residue than Warrior (pyrethroid insecticide). At 32 DAT, there were few differences between
treatments due to the reduced residual of tested insecticides and movements of soybean aphids out of plots reducing the
overall population level. Only Warrior, Folicur + Warrior, and Headline + Warrior had significantly lower number of
aphids per plants than the untreated check. Although sub-threshold aphid populations (below 250 aphids per plant) were
present in the plots prior to spraying, all treatments except Topsin and Headline SBR had significantly higher yields than
the untreated check. Insecticide and insecticide-fungicide treatments also had significantly higher yields (average of 42.6
bu/acre) compared to the fungicide alone treatments (average of 30.5 bu/acre), except for Topsin + Warrior.
Soybean aphids per plant
Treatment/
formulation
Rate
fl oz/acre
(unless noted)
Untreated check
---Folicur 3.6 F
4
Headline 2.09 EC
6
Topsin 4.5 FL
15
Headline SBR
(Folicur 3.6 F
3.1
+ Headline 2.09 F) 4.7
Lorsban 4E
1 pt/acre
Warrior 1 CS
1.92
Folicur 3.6 F
4
+ Lorsban 4E
1 pt/acre
Headline 2.09 F
6
+ Lorsban 4E
1 pt/acre
Topsin 4.5 FL
15
+ Lorsban 4E
1 pt/acre
Headline SBR
(Folicur 3.6 F
3.1
+ Headline 2.09 F) 4.7
+ Lorsban 4E
1 pt/acre
Folicur 3.6 F
4
+ Warrior 1 CS
1.92
Headline 3.6 F
6
+ Warrior 1 CS
1.92
Topsin 4.5 FL
15
+ Warrior 1 CS
1.92
Headline SBR
(Folicur 3.6 F
3.1
+ Headline 2.09 F) 4.7
+ Warrior
1.92
a
a
b
a
0 DAT
R3
6 DAT
R3
11 DAT
R4
26 DAT
R5
32 DAT
R5
Yield
bu/acre
213.7a
164.5a
225.9a
176.8a
133.4a
89.8a
75.4a
120.1a
216.0a
190.0a
201.1a
267.0a
196.5ab
238.6a
215.3a
167.3ab
82.6a-d
45.7b-f
151.6a
168.1a
26de
33c
33c
24e
162.2a
81.7a
159.0a
197.0ab
117.0ab
32cd
249.8a
152.1a
164.2a
19.2bc
10.1bcd
6.1d
19.6a
15.5bcd
12bcd
96.6cd
41.5de
68.8cde
49.7b-e
17.2f
34.1b-f
41b
45ab
43ab
231.0a
7d
15.2bc
74.2cde
50.3a-e
41ab
176.7a
6.1d
14.3bcd
49.2de
39.2b-f
43ab
170.8a
5.3d
16.6b
127.6bc
74.5abc
42ab
232.9a
6.4d
6.2d
80.3cde
21.3ef
40b
142.9a
17.1bc
16.3bcd
62.8de
34.2ef
44ab
194.9a
12.4bcd
21.7b
53.0e
32.9c-f
38bc
189.3a
22.1b
36.4e
26.9def
47a
6.5cd
Means within a column followed by the same letter are not significantly different (Fisher’s Protected LSD,
P < 0.05).
a
Data transformed using log(x + 1) prior to analyses; untransformed data presented.
b
Data transformed using arcsine square root percent prior to analyses; untransformed data presented.