Insecticide Efficacy for Control of Alfalfa Weevil and Blue Alfalfa Aphid, 2016*

The objective of the study was to evaluate the efficacy of the insecticidal compounds used against AW larvae and against BAA on alfalfa grown for hay production under desert growing conditions. A field study was conducted during the spring 2016 at the UC Desert Research and Extension Center, Holtville, CA. A stand of alfalfa, VAR. ‘CUF 101’, was used for the experiment. The experimental design was an RCB using four replicates with 10 insecticidal treatments and an untreated check. Plots measured 20 ft by 50 ft and insecticide treatments were applied on 26 Feb 2016, using a Lee Spider Spray Trac Tractor equipped with 9 TJ-60 11003VS nozzles on a spray boom applying a 15-ft swath broadcast application, operated at 50 psi, delivering 41.4 gpa through. The larval AW and BAA populations were measured in each plot with a standard 15-inch diameter insect net consisting of ten 180° sweeps; means reported in the tables are per sweep. Insect samples were collected on 25 Feb, 1 day pre treatment (1-DPT) and 29 Feb or 3 DAT, 4 Mar (7 DAT), 8 Mar (11 DAT), and 11 Mar (14 DAT). Sweep samples were bagged, labeled, and frozen for later counting of AW larvae and BAA in the laboratory. Posttreatment averages (PTA) were calculated for each treatment. Data sets were analyzed using a two-way ANOVA and means separated by LSD test (P ≤ 0.05).

The 2016 AW levels were typical for Imperial Valley alfalfa during late-Feb through mid-Mar, but the BAA levels were higher than typical and increased rapidly during Mar. There were no differences among the treatment means for AW larvae from the pretreatment samples on 25 Feb (Table 1). All of the insecticide treatments resulted in AW larvae means that were significantly (P = 0.05) lower than the means for the untreated check on all post-treatment sampling dates and for the PTAs. The Steward + Dimethoate treatment resulted in the lowest AW larvae PTA and the lowest AW larval means on all posttreatment sampling dates, compared to all other treatments, except Transform WG + Steward EC on 11 Mar. There were no differences among the treatment means for BAA on 25 Feb (Table 2). All of the insecticide treatments resulted in BAA means that were significantly (P = 0.05) lower than the means for the untreated check on all posttreatment sampling dates with the exceptions of Entrust SC and Entrust SC + Aza-Direct on 4 Mar, and Entrust on 8 Mar. All of the insecticide treatments resulted in PTAs for BAA that were lower than the PTA for the untreated check.

Table 1

	Alfalfa Weevil larvae per 10 sweeps
Treatment/formulation	Rate amt/acre	25 Feb 1DPT	29 Feb 3 DAT	4 Mar 7 DAT	8 Mar 11 DAT^a	11 Mar 14 DAT^a	PTA^a
Untreated check	–	164.25 a	131.50 a	109.25 a	117.50a	92.00 a	112.56 a
Cobalt advanced	32 fl oz	104.75 a	25.50 bc	7.00 c	16.00 d–f	28.00 c–f	19.13 cd
Transform WG	1 fl oz	130.00 a	52.00 b	48.50 b	52.75 bc	45.00 bc	49.56 b
Transform WG + Steward EC	1 fl oz 11.3 fl oz	176.25 a	6.75 b	3.00 c	0.50 g	1.50 fg	2.94 de
Sivanto 200SL+ Steward EC	7 fl oz 11.3 fl oz	124.00 a	9.75 c	4.50 c	7.25de	7.50 c–g	7.25 c–e
Sivanto 200SL	10.5 fl oz	124.00 a	44.75 b	57.50 b	63.75 ab	44.50 ab	52.63 b
Sivanto 200SL+ Steward EC	7 fl oz 11.3 fl oz	83.00 a	5.50 c	2.75 c	2.75 e–g	12.50 c–g	5.88 c–e
Sivanto 200SL + Steward EC	10.5 fl oz 11.3 fl oz	80.25 a	4.50 c	2.00 c	1.50 e–g	1.25 e–g	2.31 de
Dimethoate 2.67EC	24 fl oz	109.50 a	5.00 c	4.00 c	6.25 d–f	11.25 b–e	6.63 c–e
Steward EC + Dimethoate 2.67EC	11.3 fl oz 24 fl oz	125.25 a	3.75 c	1.25 c	1.25 fg	0.75 g	1.75 e
Entrust SC	4 fl oz	132.00 a	5.25 c	4.75 c	8.75 d	4.50 d–g	5.81 c–e
Entrust SC + Aza-Direct	4 fl oz 56 fl oz	56.25 a	5.50 c	9.00 c	12.75 cd	14.25 b–d	10.38 c
Assail 30 SG	5.0 dry oz	96.00 a	13.50 c	14.25 c	21.25 cd	16.50 b–d	16.38 c

	Alfalfa Weevil larvae per 10 sweeps
Treatment/formulation	Rate amt/acre	25 Feb 1DPT	29 Feb 3 DAT	4 Mar 7 DAT	8 Mar 11 DAT^a	11 Mar 14 DAT^a	PTA^a
Untreated check	–	164.25 a	131.50 a	109.25 a	117.50a	92.00 a	112.56 a
Cobalt advanced	32 fl oz	104.75 a	25.50 bc	7.00 c	16.00 d–f	28.00 c–f	19.13 cd
Transform WG	1 fl oz	130.00 a	52.00 b	48.50 b	52.75 bc	45.00 bc	49.56 b
Transform WG + Steward EC	1 fl oz 11.3 fl oz	176.25 a	6.75 b	3.00 c	0.50 g	1.50 fg	2.94 de
Sivanto 200SL+ Steward EC	7 fl oz 11.3 fl oz	124.00 a	9.75 c	4.50 c	7.25de	7.50 c–g	7.25 c–e
Sivanto 200SL	10.5 fl oz	124.00 a	44.75 b	57.50 b	63.75 ab	44.50 ab	52.63 b
Sivanto 200SL+ Steward EC	7 fl oz 11.3 fl oz	83.00 a	5.50 c	2.75 c	2.75 e–g	12.50 c–g	5.88 c–e
Sivanto 200SL + Steward EC	10.5 fl oz 11.3 fl oz	80.25 a	4.50 c	2.00 c	1.50 e–g	1.25 e–g	2.31 de
Dimethoate 2.67EC	24 fl oz	109.50 a	5.00 c	4.00 c	6.25 d–f	11.25 b–e	6.63 c–e
Steward EC + Dimethoate 2.67EC	11.3 fl oz 24 fl oz	125.25 a	3.75 c	1.25 c	1.25 fg	0.75 g	1.75 e
Entrust SC	4 fl oz	132.00 a	5.25 c	4.75 c	8.75 d	4.50 d–g	5.81 c–e
Entrust SC + Aza-Direct	4 fl oz 56 fl oz	56.25 a	5.50 c	9.00 c	12.75 cd	14.25 b–d	10.38 c
Assail 30 SG	5.0 dry oz	96.00 a	13.50 c	14.25 c	21.25 cd	16.50 b–d	16.38 c

PAT =

Means within columns followed by the same letter are not significantly different, LSD Test; P> 0.05. DPT = days pre-treatment; DAT = days after treatment; Post-treatment average.

Log₁₀ (X + 1) transformed data used for analysis, nontransformed means shown in the table.

Table 1

	Alfalfa Weevil larvae per 10 sweeps
Treatment/formulation	Rate amt/acre	25 Feb 1DPT	29 Feb 3 DAT	4 Mar 7 DAT	8 Mar 11 DAT^a	11 Mar 14 DAT^a	PTA^a
Untreated check	–	164.25 a	131.50 a	109.25 a	117.50a	92.00 a	112.56 a
Cobalt advanced	32 fl oz	104.75 a	25.50 bc	7.00 c	16.00 d–f	28.00 c–f	19.13 cd
Transform WG	1 fl oz	130.00 a	52.00 b	48.50 b	52.75 bc	45.00 bc	49.56 b
Transform WG + Steward EC	1 fl oz 11.3 fl oz	176.25 a	6.75 b	3.00 c	0.50 g	1.50 fg	2.94 de
Sivanto 200SL+ Steward EC	7 fl oz 11.3 fl oz	124.00 a	9.75 c	4.50 c	7.25de	7.50 c–g	7.25 c–e
Sivanto 200SL	10.5 fl oz	124.00 a	44.75 b	57.50 b	63.75 ab	44.50 ab	52.63 b
Sivanto 200SL+ Steward EC	7 fl oz 11.3 fl oz	83.00 a	5.50 c	2.75 c	2.75 e–g	12.50 c–g	5.88 c–e
Sivanto 200SL + Steward EC	10.5 fl oz 11.3 fl oz	80.25 a	4.50 c	2.00 c	1.50 e–g	1.25 e–g	2.31 de
Dimethoate 2.67EC	24 fl oz	109.50 a	5.00 c	4.00 c	6.25 d–f	11.25 b–e	6.63 c–e
Steward EC + Dimethoate 2.67EC	11.3 fl oz 24 fl oz	125.25 a	3.75 c	1.25 c	1.25 fg	0.75 g	1.75 e
Entrust SC	4 fl oz	132.00 a	5.25 c	4.75 c	8.75 d	4.50 d–g	5.81 c–e
Entrust SC + Aza-Direct	4 fl oz 56 fl oz	56.25 a	5.50 c	9.00 c	12.75 cd	14.25 b–d	10.38 c
Assail 30 SG	5.0 dry oz	96.00 a	13.50 c	14.25 c	21.25 cd	16.50 b–d	16.38 c

	Alfalfa Weevil larvae per 10 sweeps
Treatment/formulation	Rate amt/acre	25 Feb 1DPT	29 Feb 3 DAT	4 Mar 7 DAT	8 Mar 11 DAT^a	11 Mar 14 DAT^a	PTA^a
Untreated check	–	164.25 a	131.50 a	109.25 a	117.50a	92.00 a	112.56 a
Cobalt advanced	32 fl oz	104.75 a	25.50 bc	7.00 c	16.00 d–f	28.00 c–f	19.13 cd
Transform WG	1 fl oz	130.00 a	52.00 b	48.50 b	52.75 bc	45.00 bc	49.56 b
Transform WG + Steward EC	1 fl oz 11.3 fl oz	176.25 a	6.75 b	3.00 c	0.50 g	1.50 fg	2.94 de
Sivanto 200SL+ Steward EC	7 fl oz 11.3 fl oz	124.00 a	9.75 c	4.50 c	7.25de	7.50 c–g	7.25 c–e
Sivanto 200SL	10.5 fl oz	124.00 a	44.75 b	57.50 b	63.75 ab	44.50 ab	52.63 b
Sivanto 200SL+ Steward EC	7 fl oz 11.3 fl oz	83.00 a	5.50 c	2.75 c	2.75 e–g	12.50 c–g	5.88 c–e
Sivanto 200SL + Steward EC	10.5 fl oz 11.3 fl oz	80.25 a	4.50 c	2.00 c	1.50 e–g	1.25 e–g	2.31 de
Dimethoate 2.67EC	24 fl oz	109.50 a	5.00 c	4.00 c	6.25 d–f	11.25 b–e	6.63 c–e
Steward EC + Dimethoate 2.67EC	11.3 fl oz 24 fl oz	125.25 a	3.75 c	1.25 c	1.25 fg	0.75 g	1.75 e
Entrust SC	4 fl oz	132.00 a	5.25 c	4.75 c	8.75 d	4.50 d–g	5.81 c–e
Entrust SC + Aza-Direct	4 fl oz 56 fl oz	56.25 a	5.50 c	9.00 c	12.75 cd	14.25 b–d	10.38 c
Assail 30 SG	5.0 dry oz	96.00 a	13.50 c	14.25 c	21.25 cd	16.50 b–d	16.38 c

PAT =

Means within columns followed by the same letter are not significantly different, LSD Test; P> 0.05. DPT = days pre-treatment; DAT = days after treatment; Post-treatment average.

Log₁₀ (X + 1) transformed data used for analysis, nontransformed means shown in the table.

Table 2

	Blue Alfalfa Aphids per 10 sweeps
Treatment/formulation	Rate amt/acre	25 Feb 1DPT	29 Feb 3 DAT	4 Mar 7 DAT^a	8 Mar 11 DAT^a	11 Mar 14 DAT	PTA^a
Untreated check	–	353.3 a	541.0 a	1231.8 a	1635.3 a	1704.5 a	1278.1 a
Cobalt advanced	32 fl oz	366.0 a	161.3 b–d	794.0 b–d	636.8 b–d	895.0 b	621.8 bc
Transform WG	1 fl oz	308.5 a	71.8 d	432.8 ef	329.3 d	415.0 ef	312.2 ef
Transform WG + Steward EC	1 fl oz 11.3 fl oz	340.8 a	119.5 cd	404.3ef	366.5 d	373.5 f	315.9 ef
Sivanto 200SL+ Steward EC	7 fl oz 11.3 fl oz	383.0 a	123.8 cd	371.5 ef	325.8 d	517.5 d–f	334.6 d–f
Sivanto 200SL	10.5 fl oz	353.8 a	78.3 d	372.0 f	370.3 d	312.3 f	283.2 f
Sivanto 200SL+ Steward EC	7 fl oz 11.3 fl oz	246.5 a	80.8 d	428.8 ef	340.8 cd	544.3 d-f	348.6 d–f
Sivanto 200SL + Steward EC	10.5 fl oz 11.3 fl oz	325.5 a	75.8 d	365.0 f	207.3 e	460.3 ef	277.1 f
Dimethoate 2.67EC	24 fl oz	372.0 a	143.8 b–d	475.5 d–f	480.8 b–d	595.5 c–f	423.9 d–f
Steward EC + Dimethoate 2.67EC	11.3 fl oz 24 fl oz	415.0 a	152.5 b–d	583.3 c–f	451.3 cd	754.0 b–d	485.3 c–e
Entrust SC	4 fl oz	287.3 a	235.3 bc	924.0 ab	1017.5 ab	856.0 bc	758.2 b
Entrust SC + Aza-Direct	4 fl oz 56 fl oz	333.3 a	254.8 b	804.0 a–c	575.3 b–d	958.0 b	648.0 bc
Assail 30 SG	5.0 dry oz	265.0 a	111.8 cd	612.8 b–e	661.0 bc	667.8 b–e	513.3 cd

	Blue Alfalfa Aphids per 10 sweeps
Treatment/formulation	Rate amt/acre	25 Feb 1DPT	29 Feb 3 DAT	4 Mar 7 DAT^a	8 Mar 11 DAT^a	11 Mar 14 DAT	PTA^a
Untreated check	–	353.3 a	541.0 a	1231.8 a	1635.3 a	1704.5 a	1278.1 a
Cobalt advanced	32 fl oz	366.0 a	161.3 b–d	794.0 b–d	636.8 b–d	895.0 b	621.8 bc
Transform WG	1 fl oz	308.5 a	71.8 d	432.8 ef	329.3 d	415.0 ef	312.2 ef
Transform WG + Steward EC	1 fl oz 11.3 fl oz	340.8 a	119.5 cd	404.3ef	366.5 d	373.5 f	315.9 ef
Sivanto 200SL+ Steward EC	7 fl oz 11.3 fl oz	383.0 a	123.8 cd	371.5 ef	325.8 d	517.5 d–f	334.6 d–f
Sivanto 200SL	10.5 fl oz	353.8 a	78.3 d	372.0 f	370.3 d	312.3 f	283.2 f
Sivanto 200SL+ Steward EC	7 fl oz 11.3 fl oz	246.5 a	80.8 d	428.8 ef	340.8 cd	544.3 d-f	348.6 d–f
Sivanto 200SL + Steward EC	10.5 fl oz 11.3 fl oz	325.5 a	75.8 d	365.0 f	207.3 e	460.3 ef	277.1 f
Dimethoate 2.67EC	24 fl oz	372.0 a	143.8 b–d	475.5 d–f	480.8 b–d	595.5 c–f	423.9 d–f
Steward EC + Dimethoate 2.67EC	11.3 fl oz 24 fl oz	415.0 a	152.5 b–d	583.3 c–f	451.3 cd	754.0 b–d	485.3 c–e
Entrust SC	4 fl oz	287.3 a	235.3 bc	924.0 ab	1017.5 ab	856.0 bc	758.2 b
Entrust SC + Aza-Direct	4 fl oz 56 fl oz	333.3 a	254.8 b	804.0 a–c	575.3 b–d	958.0 b	648.0 bc
Assail 30 SG	5.0 dry oz	265.0 a	111.8 cd	612.8 b–e	661.0 bc	667.8 b–e	513.3 cd

PAT =

Means within columns followed by the same letter are not significantly different, LSD Test; P> 0.05. DPT = days pre-treatment; DAT = days after treatment; Post-treatment average.

Log₁₀ (X + 1) transformed data used for analysis, non-transformed means shown in the table.

Table 2

	Blue Alfalfa Aphids per 10 sweeps
Treatment/formulation	Rate amt/acre	25 Feb 1DPT	29 Feb 3 DAT	4 Mar 7 DAT^a	8 Mar 11 DAT^a	11 Mar 14 DAT	PTA^a
Untreated check	–	353.3 a	541.0 a	1231.8 a	1635.3 a	1704.5 a	1278.1 a
Cobalt advanced	32 fl oz	366.0 a	161.3 b–d	794.0 b–d	636.8 b–d	895.0 b	621.8 bc
Transform WG	1 fl oz	308.5 a	71.8 d	432.8 ef	329.3 d	415.0 ef	312.2 ef
Transform WG + Steward EC	1 fl oz 11.3 fl oz	340.8 a	119.5 cd	404.3ef	366.5 d	373.5 f	315.9 ef
Sivanto 200SL+ Steward EC	7 fl oz 11.3 fl oz	383.0 a	123.8 cd	371.5 ef	325.8 d	517.5 d–f	334.6 d–f
Sivanto 200SL	10.5 fl oz	353.8 a	78.3 d	372.0 f	370.3 d	312.3 f	283.2 f
Sivanto 200SL+ Steward EC	7 fl oz 11.3 fl oz	246.5 a	80.8 d	428.8 ef	340.8 cd	544.3 d-f	348.6 d–f
Sivanto 200SL + Steward EC	10.5 fl oz 11.3 fl oz	325.5 a	75.8 d	365.0 f	207.3 e	460.3 ef	277.1 f
Dimethoate 2.67EC	24 fl oz	372.0 a	143.8 b–d	475.5 d–f	480.8 b–d	595.5 c–f	423.9 d–f
Steward EC + Dimethoate 2.67EC	11.3 fl oz 24 fl oz	415.0 a	152.5 b–d	583.3 c–f	451.3 cd	754.0 b–d	485.3 c–e
Entrust SC	4 fl oz	287.3 a	235.3 bc	924.0 ab	1017.5 ab	856.0 bc	758.2 b
Entrust SC + Aza-Direct	4 fl oz 56 fl oz	333.3 a	254.8 b	804.0 a–c	575.3 b–d	958.0 b	648.0 bc
Assail 30 SG	5.0 dry oz	265.0 a	111.8 cd	612.8 b–e	661.0 bc	667.8 b–e	513.3 cd

	Blue Alfalfa Aphids per 10 sweeps
Treatment/formulation	Rate amt/acre	25 Feb 1DPT	29 Feb 3 DAT	4 Mar 7 DAT^a	8 Mar 11 DAT^a	11 Mar 14 DAT	PTA^a
Untreated check	–	353.3 a	541.0 a	1231.8 a	1635.3 a	1704.5 a	1278.1 a
Cobalt advanced	32 fl oz	366.0 a	161.3 b–d	794.0 b–d	636.8 b–d	895.0 b	621.8 bc
Transform WG	1 fl oz	308.5 a	71.8 d	432.8 ef	329.3 d	415.0 ef	312.2 ef
Transform WG + Steward EC	1 fl oz 11.3 fl oz	340.8 a	119.5 cd	404.3ef	366.5 d	373.5 f	315.9 ef
Sivanto 200SL+ Steward EC	7 fl oz 11.3 fl oz	383.0 a	123.8 cd	371.5 ef	325.8 d	517.5 d–f	334.6 d–f
Sivanto 200SL	10.5 fl oz	353.8 a	78.3 d	372.0 f	370.3 d	312.3 f	283.2 f
Sivanto 200SL+ Steward EC	7 fl oz 11.3 fl oz	246.5 a	80.8 d	428.8 ef	340.8 cd	544.3 d-f	348.6 d–f
Sivanto 200SL + Steward EC	10.5 fl oz 11.3 fl oz	325.5 a	75.8 d	365.0 f	207.3 e	460.3 ef	277.1 f
Dimethoate 2.67EC	24 fl oz	372.0 a	143.8 b–d	475.5 d–f	480.8 b–d	595.5 c–f	423.9 d–f
Steward EC + Dimethoate 2.67EC	11.3 fl oz 24 fl oz	415.0 a	152.5 b–d	583.3 c–f	451.3 cd	754.0 b–d	485.3 c–e
Entrust SC	4 fl oz	287.3 a	235.3 bc	924.0 ab	1017.5 ab	856.0 bc	758.2 b
Entrust SC + Aza-Direct	4 fl oz 56 fl oz	333.3 a	254.8 b	804.0 a–c	575.3 b–d	958.0 b	648.0 bc
Assail 30 SG	5.0 dry oz	265.0 a	111.8 cd	612.8 b–e	661.0 bc	667.8 b–e	513.3 cd

PAT =

Means within columns followed by the same letter are not significantly different, LSD Test; P> 0.05. DPT = days pre-treatment; DAT = days after treatment; Post-treatment average.

Log₁₀ (X + 1) transformed data used for analysis, non-transformed means shown in the table.

This research was supported by industry gifts of products and research funding.

Author notes

Subject Editor: Donald Cook

This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/4.0/), which permits non-commercial re-use, distribution, and reproduction in any medium, provided the original work is properly cited. For commercial re-use, please contact [email protected]

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Article Contents

Insecticide Efficacy for Control of Alfalfa Weevil and Blue Alfalfa Aphid, 2016*

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Insecticide Efficacy for Control of Alfalfa Weevil and Blue Alfalfa Aphid, 2016*

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