Monitoring of Wheat Midge and the Associated Parasitoid Macroglenes penetrans in Spring Wheat Fields

Principle Investigator: Gadi V.P. Reddy

Project personnel: Govinda Shrestha, Dan Picard, Ramadevi L. Gadi

Western Triangle Agricultural Research Center, Montana State University, 9546 Old Shelby Rd., P.O. Box 656, Conrad, MT 59425, USA

Aim of the Study

The aims of this study were: 1) to determine the wheat midge population in the Golden Triangle area of Montana and 2) to monitor the status of parasitoid M. penetrans in the Golden Triangle area of Montana

Fig. Life cycle of wheat midge

Materials and Methods

Wheat midge populations

WTARC installed 14 pheromone traps (Fig 1) in spring wheat fields at different locations such as in Valier, WTARC, Ledger, Cutbank, Devon, Choteau and Knees in the Golden Triangle area of Montana. Traps were set out from June 3-10, 2016. Pheromone traps were monitored every day from Monday to Friday in Valier, WTARC and Ledger areas, while at an average of 10 day intervals in Cutbank, Devon, Choteau and Knees areas. Trap monitoring work was wrapped up in the last week of July.

Figure1. A) Spring wheat growers (Cory Crawford and Tex Crawford) and a summer intern (Connie Miller) monitoring wheat midge adults on a pheromone trap at Valier and B) Wheat midge parasitoid Macroglenes penetrans adult

Parasitoid Macroglenes penetrans

Monitoring of M. penetrans adult (Fig 1) were performed in two steps: 1) determine the presence or absence of parasitoid adults in spring wheat fields where traps were established (only monitored at Valier, WTARC and Ledger areas) and, 2) monitor the M. penetrans adult activity at two locations throughout pest activity periods. Sweep net method was used to sample the parasitoids from each field (80 sweeps per sampling time) and the parasitoid adults were confirmed under a stereomicroscope. As a first step, parasitoid adults were monitored at 3-4 days intervals in all the traps established sites until its presence or absence was determined. First activity was initiated on June 20, 2016. As a second step, two spring wheat fields at Valier were selected to monitor the parasitoids activity throughout wheat midge activity periods. This is an area where almost all spring wheat growers spray insecticides to control wheat midge. This second activity began June 20 and completed on July 15, 2016.

Table 1. Total cumulative midge count observed in Valier, WTARC and Ledger areas of Montana

Results

Total cumulative midge count observed in our trap established locations were shown in Table 1. In 2016, wheat midge populations were checked in seven counties (Liberty, Toole, Teton, Chouteau, Glacier, Cascade and Pondera) at the Golden Triangle area of Montana. The total number of wheat midge pheromone traps installed in wheat fields were 58. Among the seven counties, the highest wheat midge populations were observed in Pondera County in contrast to no presence of wheat midge in Cascade County (Fig 1). The second highest wheat midge populations were noticed at Liberty County followed by Toole, Glacier, Teton and Chouteau Counties (Fig 1). In comparisons of this year data with previous years (2014 and 2015), wheat midge populations were further sharply increased in Pondera and Liberty Counties, remained steady in Teton, Glacier and Chouteau Counties and declined in Toole County (Fig 1).

Fig1. Wheat midge population trends at the Golden Triangle area of Montana from 2014-2016

Parasitoid Macroglenes penetrans

Parasitoid adults were monitored in 8 field locations at the Golden Triangle area of Montana (see Table 2). Among the 8 locations, parasitoids were found in Valier (4 locations) and WTARC (2 locations) areas while no parasitoids were recorded in other two locations (Table 2).

Table 2.Monitoring of Macroglenes penetrans at field sites in Pondera County

NA: Data not recorded

Acknowledgements

This work was supported by Montana Wheat and Barley Committee. We would like to thank Connie Miller for assistance with field work.