2002 Nebraska Insecticide Evaluations

Researcher(s): Keith Jarvi

Location: Haskell Agricultural Laboratory

Evaluation: Cowpea aphid and grasshopper insecticide

Species: Cowpea aphid, Aphis craccivora Koch

Differential grasshopper, Melanoplus differentialis Thomas

Two-striped grasshopper, Melanoplus bivittatus (Say)

Hybrid	Alfalfa variety: Garst 630
Row Spacing
Application Date	2 August 2002
Planter
Stage	50% bloom
Average height of stand:	18 inches
Planting Rate
Application Equipment	Backpack CO2 sprayer with 5 ft boom,14.75 gal acre, 25 psi
Field Preparation
Fertilization
Herbicides
Wind	Calm
Temperature	55 ^o F
Soil Type
Organic Matter
ph
Field History
Irrigation
Plot Direction
Plot Size	20 by 20 ft

Experimental Design and Evaluation

Randomized complete block with 4 replications

Ratings: Number of insects per 3 180 degree sweeps of a 15 inch diameter net within each plot

Counts taken on 3, 7 and 14 days after application

Statistical evaluation based on 25 June count.

Comments: This was the first year cowpea aphids were at high levels in alfalfa fields in Nebraska. Tom Hunt first found the cowpea aphid in Nebraska in Knox County in 1999. Pretreatment counts were estimated at over 500 aphids per sweep of a 15 inch diameter net. Stunting and discoloration of the alfalfa was nor evident at the time. No phytotoxic symptoms were cause by any of the treatments. A 3.2 inch rain the day after application greatly reduced aphid and grasshopper populations and no significant differences were found after the 7 day count.

Note: FMC 0570 was applied at higher than the recommended rate.

Insecticide Screening Concord, Nebraska 2002

Number of cowpea aphids per 3 sweeps

Treatment	Rate formulation per acre	3 day count	7 day count
FMC 0570	2.4 oz	0.00 a	0.50 abc
Lorsban 4 E	16 oz	0.25 a	2.00 cd
Warrior TC	2.6 oz	1.00 a	0.00 a
Dow XDE 225	3.2 oz	1.00 a	0.25 ab
Pounce 3.2 EC	4 oz	2.50 a	1.75 bcd
Baythroid 1 EC	1.6 oz	5.50 ab	0.75 abc
Untreated		15.25 b	2.50 d

Means with the same letter are not significantly different. (3 day LSD = 11.781, 7 day LSD 1.7103; alpha = 0.05)

Insecticide Screening Concord, NE 2002

Number of grasshoppers per 3 sweeps

Treatment	Rate formulation per acre	3 day count	7 day count
Lorsban 4E	16 oz	0.50 a	1.75 abc
Warrior TC	2.6 oz	1.00 a	0.50 a
Dow XDE 225	3.2 oz	1.25 ab	3.25 bc
FMC 0570	2.4 oz	1.25 ab	1.25 ab
Baythroid 1 EC	1.6 oz	2.50 abc	1.25 ab
Untreated		5.25 cd	3.25 bc
Pounce 3.2 EC	4 oz	6.00 c	4.00 c

Means with the same letter are not significantly different. (3 day LSD = 4.2454, 7 day LSD 2.5612; alpha = 0.05)