North Central Research Extension Center

Jan Knodel, Crop Protection Specialist, Email: jknodel@ndsuext.nodak.edu

Wheat Midge Insecticidal Trial 1999 - HRSW                                                     Ward County (Minot)

Treatment
Formulation

Rate
Fl. oz/A

Ave. # Larvae per 10 Wheat Heads*

Ave. Yield*
Bu/A

Ave. Test Weight*
lb/bu

Cost
$/A
Untreated

2.75 a

38.2 a

58.24 a

$0.00
Penncap-M 2FM

16

0.50 a

42.8 a

58.8 a

$3.50
Penncap-M 2FM

32

1.50 a

39.7 a

59.2 a

$7.04
Penncap-M 2FM

48

0.75 a

39.2 a

58.8 a

$10.56
Penncap-M 2FM+ Penncozeb 75DF

32+ 1.5#/A

0.25 a

40.8 a

59.1 a

$14.31
Lorsban
4E-SG

16

0.25 a

41.5 a

58.7 a

$5.66

* Means within the same column are separated by Anova and Fisher’s PLSD at a 5% significance level.

The variety Amidon HRSW was planted on May 26, 1999. The high risk planting period (200-600 degree days, base = 40BF) for wheat midge infestation was April 30 to May 27, 1999 in the Minot area. So, the May 26 planting date was at the end of the susceptible planting period for wheat midge infestation. Insecticides were applied at late heading (80%) on the evening of July 17, 1999 using a handheld boom sprayer with XR 8001 nozzles (5 nozzles total), 40 PSI, and 10 GPA. Night visual observations for adult wheat midge were conducted on two nights by making six observations at 8 different field sites for a total of 48 counts. Night observations for adult orange wheat blossom midge averaged 1 adult per 9 wheat heads on both nights - July 18 and 21, 1999. Wheat was in the heading to mid-flowering stage during the night observations. The threshold for spraying is 1 wheat midge per 4-5 wheat heads. So, the field was not at economic threshold level. A total of 40 wheat heads per treatment (10 wheat heads per plot) were randomly collected on August 3,1999. Heads were later examined and counted for wheat midge larvae. Wheat was harvested on September 14, 1999 using a small plot combine.

All insecticides resulted in lower larval counts in wheat heads than the untreated check. Penncap-M 0.5 + Penncozeb 1.125 and lorsban had the lowest larval count, then Penncap 0.25, Penncap 0.75 and last Penncap 0.5. Due to the light pressures from wheat midge, there were no significant differences among the treatments for larval counts. There were differences in the yield among treatments, but they were not significant. In general, treatments with lower larval counts had higher yields. For example, the untreated check had a 11% yield loss compared to the highest yield, Penncap 0.25. The cost to applied each insecticide per acre was estimated based on 1999 prices. Prices ranged from $3.30 to $8.64 per acre depending on the insecticide and its rate.

We are very grateful to the grower, Travis Zablotney, who let us use his wheat field.

North Central Research Extension Center (http://www.ag.ndsu.nodak.edu/minot/)

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    Department of Entomology, 202 Hultz Hall
  North Dakota State University, Fargo North Dakota

  Extension Entomologist: Janet Knodel