Janet Knodel
North Central Research Extension Center, NDSU, Minot, ND

Purpose and Objective
     To evaluate the efficacy of different insecticides-fungicides used for control of orange wheat blossom midge (Sitodiplosis mosellana) and wheat diseases (scab, tan spot, Septoria).

Material and Methods
     The variety Monroe Durum was planted early on May 12, 2001 on a previous durum field. The high risk planting period (200-600 degree days, base = 40^BF) for wheat midge infestation was May 4 to May 26, 2001 in the Plaza-Makoti area. So, the May 12th planting date was in the middle of the susceptible planting period for wheat midge infestation. Plots were 10' wide by 30' long with a RCBD with six replicates. Herbicides (a pt./A of Starene, a pt./A of Puma, and a oz./A of Harmony GT) were applied for weed control on June 21, 2001. Insecticides-fungicides were applied at late heading to early flowering (uneven growth) on the evening of July 9, 2001 using a handheld boom sprayer with 8002 Twin-jet nozzles (5 nozzles total), 40 PSI, and 20 GPA. An adjuvant, Induce, was used with all treatment except Lorsban alone and the untreated. Night visual observations for adult wheat midge averaged at least 1 wheat midge per 7 wheat heads, which is the economic threshold level for durum. A total of 120 wheat heads and flag leaves per treatment (20 wheat heads/flag leaves per plot) were randomly collected on July 30, 2001 for evaluation of disease infection – scab (Fusarium head blight) and leaf diseases (tan spot and Septoria). The percent incidence and severity were determined for each disease. Another 120 wheat heads per treatment (20 wheat heads per plot) were randomly collected on July 30, 2001 for wheat midge counts. Wheat heads were allowed to dry and later rubbed out. The number of wheat midge larvae and kernels per head were counted. Wheat was harvested on August 16, 2001 using a small plot combine.

Results and Discussion
     All insecticides and insecticide-fungicide treatments resulted in lower wheat midge infestation than the untreated check and the fungicide alone treatments (Table 1). However, these differences were not always significant at the 5% level due to the large variability within treatments. Treatments with significantly lower number of wheat midge numbers listed in ascending order include: 16 oz/A of Lorsban + 4 oz/A of Folicur + Induce; 16 oz/A of Lorsban; 16 oz/A of Penncap-M + Induce; 8 oz/A of Lorsban + 4 oz/A of Folicur + Induce; 32 oz/A of Penncap-M + 1 lb/A of Penncozeb + Induce; and 32 oz/A of Penncap-M + Induce. For wheat scab, the average field severity in the untreated check was 37%, 37% in the insecticide treated plots, 28% in the insecticide-fungicide treated plots, and 28% in the fungicide treated plots. Overall, the field severity of scab was lower in the fungicide and insecticide-fungicide treated plots than the insecticide alone treated plots and untreated check. The Folicur sprayed plots had significantly lower field severity for scab than the Penncozeb sprayed plots. Again, the fungicide and insecticide-fungicide treatments had lower severity of leaf diseases compared to the insecticide alone and untreated check. The average severity of leaf diseases in the untreated check was 41%, 42% in the insecticide treated plots, 22.5% in the insecticide-fungicide treated plots, and 27% in the fungicide treated plots.

     In Table 2, the harvest results are summarized. In general, treatments with both insecticide+fungicide had higher yields than the other treatments. However, these differences were only significant for the Lorsban + Folicur + Induce treatments. This suggests that the pressures from both wheat midge and diseases reduced the overall yield. The untreated check (33.4 Bu/Acre) had 9.3 fewer bushels per acre compared to the treatment with the highest yield, 8 oz/A of Lorsban + 4 oz/A of Folicur + Induce (42.7 bu/acre). The insecticide alone treatments averaged a 3.5 bu/A increase, the insecticide-fungicide treatments averaged a 6.5 bu/A increase, where as the fungicide alone treatments averaged a 1.5 bu/A increase. The local environmental conditions may have impacted the level of disease infection. For test weight, only three treatments had a significantly higher test weight than the untreated control:
16 oz/A of Lorsban + 4 oz/A of Folicur + Induce; 8 oz/A of Lorsban + 4 oz/A of Folicur + Induce; and 32 oz/A of Penncap-M + 1 lb/A of Penncozeb + Induce. No significant differences were recorded in grain protein content among treatments. For percent seed damaged, the untreated check has 16% damage and was significantly higher from all of the treatment except 32 oz/A of Penncap-M + Induce. The combination Lorsban + Folicur + Induce treatments (both rates) had the lowest percent seed damaged.

     The estimated costs of Lorsban is about $2.75/A for 8 oz/A and $5.50/A for 16 oz/a; where as Penncap-M is about $3.20/A for 16 oz/A and $6.40/A for 32 oz/A. The fungicide costs for Folicur at 4 oz/A is about $9.50/A; and $2.25/A for Penncozeb at 1 lb/A. The adjuvant, Induce, is about 50 cents per acre. As a result, an application of Lorsban + Folicur + Induce ranges from $12.75 to $15.50 per acre; in contrast, an application of Penncap-M + Penncozeb + Induce ranges from $5.455 to $8.65 per acre. The application costs would also run about $3.50 per acre for air and $2.50 per acre for ground (based on 2001 prices).

Acknowledgements
     We are very grateful to the grower, Monty Schenfisch, who let us use his land; and to Craig Rystedt of Monsanto, who planted the plots. Harvest assistance was provided from Yabo Gjellstad and John Reimer from the North Central Research Extension Center. This research would not have been possible without the field assistance of H. Semler, N. Carlson, K. Novak, K. McKay, K. Clark; and the support of Dow AgroSciences and Cerexagri.