Of all of the insecticides evaluated against blue alfalfa aphid (BAA) by Eric Natwick of Imperial County, almost every insecticide applied to alfalfa this spring gave initial knockdown of BAA. Blue alfalfa aphid populations resurged in 7-10 days. Treatments giving 70–75% control (reported by PCA’s) were combinations of a pyrethroid with an organophosphate.
Possible factors for our BAA issue:
- High initial aphid populations
- Smaller than expected populations of predators and parasites; particularly the seven-spotted lady beetle
May be weather related or pesticide related
- Potentially more insecticides to alfalfa than in the past; partially due to cowpea aphid
- Lack of “bio-rational” for weevil and aphid management in alfalfa
- Growers are spraying at the time of year when there are the fewest beneficial insects in alfalfa. The insecticides along with cool weather may be preventing or delaying the buildup of beneficial insect populations
Blue Alfalfa Aphids per Sweep, Holtville, CA, 2013.
|
Treatment |
fl oz/acre |
1 DPTw |
3 DATxz |
7 DAT |
10 DAT |
14 DAT |
PTAyz |
|
Check |
-------- |
105.05 a |
58.58 a |
38.83 a |
82.50 a |
39.10 b |
54.75 |
|
Warrior II |
1.92 |
127.80 a |
10.95 bc |
8.63 c |
15.55 b |
24.23 bc |
14.84 b |
|
Endigo ZCX |
4.0 |
84.00 a |
1.08 f |
3.05 c |
4.48 b |
13.73 c |
5.58 bc |
|
Besiege |
9.0 |
103.05 a |
5.55 cd |
2.93 c |
16.63 b |
21.60 bc |
11.68 b |
|
Cobalt Advanced |
24.0 |
69.75 a |
2.23 de |
1.60 c |
5.73 b |
6.60 c |
4.11 c |
|
Mustang |
4.3 |
91.48 a |
4.53 d |
3.20 c |
13.13 b |
18.13 bc |
9.74 b |
|
Stallion 3.025 EC |
9.25 |
95.98 a |
3.53 d |
2.38 c |
14.33 b |
13.45 c |
8.42 bc |
|
Stallion 3.025 EC |
11.75 |
105.05 a |
2.08 ef |
2.25 c |
5.48 b |
22.45 bc |
8.06 bc |
|
Danitol |
16.0 |
115.23 a |
13.98 b |
22.28 b |
65.45 a |
65.45 a |
41.79 a |
Blue Alfalfa Aphids per Ten Sweeps, Holtville, CA, 2013.
|
Treatment |
fl oz/acre |
PTw |
3 DATx |
7 DATz |
14 DAT |
PTAyz |
|
Check |
-------- |
58.48 a |
65.66 a |
82.64 a |
86.36 a |
78.22 a |
|
Paradigm VC |
3.84 |
60.02 a |
17.12 b |
18.68 b |
20.16 b |
18.65 b |
|
Baythroid XL |
1.9 |
49.58 a |
11.84 b |
23.20 b |
26.12 b |
20.39 b |
|
Mustang |
4.3 |
54.44 a |
11.42 b |
15.40 b |
23.00 b |
16.61 b |
|
Lorsban Advanced |
24.0 |
81.56 a |
8.20 b |
7.28 c |
15.34 b |
10.27 c |
|
Warrior II |
1.92 |
72.64 a |
14.58 b |
6.94 c |
15.92 b |
12.48 bc |
Means within columns followed by the same letter are not significantly different, LSD; P= 0.05.
w Pre-treatment
x Days after treatment
y Post treatment average
z Log10 (X+1) transformed data used for analysis, ACTUAL MEANS REPORTED