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Virginia Cooperative Extension - Knowledge for the CommonWealth

Performance of Commercial Insecticides Against Alfalfa Weevil in Virginia

Crop and Soil Environmental News, April 1999

R. R. Youngman, C. A. Laub, T. P. Kuhar, and T. A. Dellinger
Department of Entomology, Virginia Tech

The first three tables show results of several commercial insecticides that we have evaluated against alfalfa weevil in Virginia. In most cases, insecticides significantly reduced alfalfa weevil numbers below that of the untreated check. Those insecticides that consistently gave superior control of alfalfa weevil larvae for approximately 14 to 21 days after treatment (DAT) include: Baythroid 2E, Furadan 4F, Lorsban 4E, and Karate 1E (= Warrior T 1CS).

The last table lists performance ratings of commercial insecticides reported in alfalfa weevil efficacy trials from other alfalfa producing states, as well as Virginia, for the period from 1993 -1997. This information is annually published by the Entomological Society of America in Arthropod Management Tests. We rated insecticides as either excellent (E), good (G), fair (F), or poor (P) depending on how well they controlled alfalfa weevil compared to their respective controls for up to three weeks.

1998 Alfalfa Weevil Insecticide Efficacy Trial;
Pulaski Co., Virginia
Alfalfa weevil larvae/10 stems
TreatmentRate
(lb AI/ac)		0 DAT
(21 Apr)		4 DAT
(25 Apr)		8 DAT
(29 Apr)		13 DAT
(4 May)		20 DAT
(11 May)		24 DAT
(15 May)
Baythroid 2E   0.02526.6ab*0.0b0.6b1.0b0.0d0.6b
Furadan 4F   0.516.6abc0.6b0.0b1.6b0.0d1.0b
Karate 1E   0.02516.6abc3.6b0.0b0.6b0.0d0.0b
Lorsban 4E   0.514.6c0.6b0.6b1.6b0.3d0.0b
Check (untreated)   --26.6ab33.0a33.6a33.0a9.0a4.6a
*Means within a column followed by the same letter are not significantly different; LSD (P > 0.05).

1997 Alfalfa Weevil Insecticide Efficacy Trial;
Floyd Co., Virginia
Alfalfa weevil larvae/10 stems
TreatmentRate
(lb AI/ac)		0 DAT
(15 Apr)		5 DAT
(20 Apr)		10 DAT
(25 Apr)		14 DAT
(29 Apr)		20 DAT
(5 May)		24 DAT
(9 May)		28 DAT (13 May)
Baythroid 2E   0.0259.00.6 b2.0 bcd0.6 cd0.0 f0.0 f2.0 c
Furadan 4F   0.512.60.0 b0.0 d0.6 cd0.6 ef2.0 ef2.0 c
Furadan 4F   1.010.60.6 b0.6 cd0.6 cd0.6 ef0.0 f0.6 c
Karate 2.09CS   0.0259.60.0 b1.0 bcd0.6 cd0.6 ef0.6 ef1.6 c
Lannate 2.4LV   0.4513.01.0 b2.0 bcd4.6 b5.0 cde7.0 bcd12.0 ab
Lannate 2.4LV   0.911.01.0 b0.6 cd1.0 bcd3.0 def6.0 cd9.0 ab
Lorsban 4E   0.57.01.0 b0.6 cd0.6 cd0.6 ef0.6 ef2.0 c
Lorsban 4E   1.015.60.0 b0.0 d1.6 bcd0.6 ef0.6 ef2.0 c
Check (untreat.)   --8.610.0 a7.6 a13.6 a17.6 a23.6 a17.0 a

1996 Alfalfa Weevil Insecticide Efficacy Trial;
Montgomery Co., Virginia
Alfalfa weevil larvae/10 stems
TreatmentRate
(lb AI/ac)		0 DAT*
(25 Apr)		4 DAT
(1 May)		7 DAT
(4 May)		12 DAT
(9 May)		16 DAT
(13 May)
Furadan 4F   0.58.30.0 b0.5 c1.0 c0.3 c
Karate 1E   0.0258.30.0 b0.3 c0.5 c0.5 c
Lannate 2.4LV   0.457.00.8 b3.3 b5.3 b6.8 b
Check (untreat.)   --8.310.5 a15.5 a13.5 a12.5 a
*All insecticides were applied on 27 April 1996.

Performance of commercial insecticides for control of alfalfa weevil.
Data obtained from ESA Arthropod Management Tests: 1993-97.
InsecticideNo. of
tests		Insecticide performance ratinga
Ambush 2E3   G,G,G
Baythroid 2E18   E,E,E,E,E,E,E,E,E,E,E,E,E,E,E,E,E,E
Furadan 4F24   E,E,E,E,E,E,E,E,E,E,E,E,E,E,E,E,E,E,G,G,G,G,G,P
Imidan 2.5EC7   E,E,E,E,E,E,F
Guthion 3F2   E,G
Lorsban 4E20   E,E,E,E,E,E,E,E,E,E,E,E,E,E,E,E,G,G,G,F
Penncap-M 2F5   E,E,E,G,G
Pounce 3.2EC13   E,E,E,E,E,E,E,E,E,E,G,G,G
Sevin XLR Plus6   E,E,E,E,E,G
Warrior/Karate12   E,E,E,E,E,E,E,E,E,E,E,E
a "E" = excellent; "G" = good; "F" = fair; "P" = poor



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