ProCrop

Orange Wheat Blossom Midge Timing Insecticide-Fungicide 
Trial (1999) - HRSW Benson County (Minnewaukan)

The variety Russ HRSW was planted on May 10, 1999. The high risk planting period (200-600 degree days, base = 40^BF) for wheat midge infestation was May 2 to May 30, 1999 in the Baker area. So, the May 10 planting date was in the middle of the susceptible planting period for wheat midge infestation. Insecticides-fungicides were applied at early heading (30%) on July 11, 1999; at late heading (90%) on July 14, 1999, at early flowering on July 16, 1999; and at mid-flowering (50%) on July 19, 1999. All treatments were applied with a backpack sprayer using a double swivel adapter containing XR 8001 nozzles angled 30� from horizontal and directed forward and backwards to the direction of travel, 40 PSI, and 18.5 GPA . Table 1 includes application information. The levels of Orange Wheat Blossom Midge were observed at 1 adult per 6 heads at the 90% headed stage. The threshold for spraying is 1 wheat midge per 4-5 wheat heads. So, the field was slightly below the economic threshold level. Ten heads per plot were sampled August 4, 1999. It appeared that some midge larvae may had left the heads due to a light rainfall the day before. Wheat scab (head blight) ratings were taken August 13, 1999 at the soft dough stage. Seven heads at 3 locations in each plot were visually evaluated for scab symptoms.

Results of the wheat midge and scab counts are summarized in Table 2. The late heading, early flowering, and mid flowering applications of Lorsban and Lorsban-Folicur had the significantly lower larval counts compared to the untreated check and Folicur alone treatments. However, there was no significant differences in number of larvae between treatments applied at the 30% heading application. This application timing was too early for effective control of wheat midge. Folicur had no negative affects on Lorsban�s efficacy against wheat midge. For wheat scab (head blight), the untreated check, all treatments applied at the 30% heading stage, and the Lorsban alone treatments applied at 90% heading, early flowering, and mid flowering stages had significantly higher severity of scab. In contrast, the Folicur alone or with Lorsban treatments provided significant reductions in percent scab for treatments applied at the 90% heading, early flowering, and mid flowering stages. The estimated costs to applied the insecticide, Lorsban, is about $5.66 per A and the fungicide, Folicur, is about $9.14 per A; which would make Lorsban + Folicur about $14.80 per A (based on 1999 prices).

We are very grateful to the grower, Howard Schmidt, who let us use his wheat field. This work was supported by SBARE, North Dakota Wheat Commission, and Dow AgroSciences.

Janet Knodel¹ and Terry Gregoire²

¹ North Central Research Extension Center, NDSU, Minot, ND 

² NDSU Extension, Devils Lake, ND

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