A Survey of Five Stem-Feeding Insect Pests of Wheat in the Northern Great Plains
The wheat stem sawfly, Cephas cinctus Norton, the wheat stem maggot, Meromyza americana Fitch, the Hessian fly, Mayetiola destructor (Say), the wheat jointworm, Tetramesa tritici (Fitch), and the wheat strawworm, Tetramesa grandis (Riley), have long been considered wheat pests in the northern Great Plains. This paper reports results of surveys for these pests conducted over 3 yrs in parts of Montana (10 counties), North Dakota (14 counties), South Dakota (1 county), Nebraska (4 counties) and Wyoming (1 county). Fields were randomly selected and a mean of 191 stems were sampled from each field. The percentage of stems infested with each pest was recorded. The percentage of parasitized wheat stem sawfly larvae also was noted. The wheat stem sawfly, wheat stem maggot, and Hessian fly were the most commonly encountered pests, recorded in nearly every county. Wheat stem sawfly density was twice that of wheat stem maggot (7% vs 3.2%) in infested fields. Wheat stem sawfly densities exceeded 10% in 4 counties: Da...
Using Sex Pheromone Trapping to Explore Threats to Wheat from Hessian Fly (Diptera: Cecidomyiidae) in the Upper Great Plains
ABSTRACT 
 Before embarking on the 5–10 yr effort it can take to transfer plant resistance (R) genes to adapted crop cultivars, a question must be asked: is the pest a sufficient threat to warrant this effort? We used the recently discovered female-produced sex pheromone of the Hessian fly, Mayetiola destructor (Say) (Diptera: Cecidomyiidae), to explore this question for populations in the Upper Great Plains. Methods for pheromone trapping were established and trapping data were used to explore geographic distribution, phenology, and density. The pheromone lure remained attractive for up to 10 d and only attracted male Hessian flies. Traps placed within the crop canopy caught flies but traps placed above the crop canopy did not. Hessian flies were trapped throughout North Dakota starting in the spring and continuing through the summer and autumn. Densities were low in the spring but increased greatly during the early part of the summer, with peak adult emergence taking place at a time (July/August) when spring wheat was being harvested and winter wheat had not yet been planted. In the autumn, adults were found at a time when winter wheat seedlings are growing. The discovery of flies on Conservation Reserve Program land supports the idea that pasture grasses serve as alternate hosts. We conclude that the Hessian fly is a risk to wheat in the Upper Great Plains and predict that global warming and the increasing cultivation of winter wheat will add to this risk.
Experimental study of water fluxes in a residential area: 2. Road infiltration, runoff and evaporation
Lack of accurate data has led some hydrologists and city planners to assume that urban infiltration is zero and runoff is 100% of the rainfall. These assumptions lead to an over estimation of road runoff volume and an underestimation of direct recharge to groundwater, which is already rising under some UK cities. This study investigates infiltration and runoff processes and quantifies the percentage of rainfall that contributes to storm drainage, and that which infiltrates through different types of road surface. Access tubes were installed for measuring soil water content using a neutron probe in three car parks, a road and a grass site at the Centre for Ecology and Hydrology, Crowmarsh Gifford, Wallingford. Storm drainage was recorded at the exit of the Thamesmead Estate in Crowmarsh Gifford, just before the drain joins the River Thames at Wallingford. Rainfall and water table depth were also recorded. Weekly measurements of soil moisture content indicated that the top 40 cm layer is not influenced by water‐table fluctuations and, therefore, positive changes in soil moisture could be attributed to infiltration of rainfall through the surface. Depending on the nature of the surface, subsurface layers, level of traffic, etc., between 6 and 9% of rainfall was found to infiltrate through the road surfaces studied. The storm drainage generated by road runoff revealed a flow pattern similar to that of the receiving watercourse (River Thames) and increased with the increase of infiltration and soil water content below the road surface. The ratio of runoff to rainfall was 0·7, 0·9 and 0·5 for annual, winter (October–March) and summer (April–September) respectively. As the results of the infiltration indicated that 6 to 9% of annual rainfall infiltrates through the road surface, this means that evaporation represents, 21–24% of annual rainfall, with more evaporation taking place during summer than winter. Copyright © 2003 John Wiley & Sons, Ltd.