This chapter presents an overview of Western corn rootworm (WCR) monitoring in Europe from 1992 to 2003. The other topics covered include monitoring as a tool for multiple purposes and some characteristics of the spread of WCR in Europe.

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Potato virus Y (PVY) is the potato virus with the highest economic impact on seed potato production. Insecticides are efficient in controlling aphids, which are the vectors of this virus, but rarely limit virus spread in the field. Straw mulching and mineral oil spraying are known as alternatives to insecticides to reduce PVY incidence, but important year-toyear variation in efficacy has been observed with both of these techniques. Preliminary studies revealed the efficacy of intercropping in controlling PVY spread, but more data are needed to validate this observation. A four-year field trial was conducted in Switzerland to assess the potential synergistic effect of combining mineral oil spraying with straw mulching to increase the protection of seed potato crops against PVY spread. Furthermore, the efficacy of intercropping with oat and hairy vetch was examined as a novel way to control in-field PVY spread. The present work demonstrates that the modes of action of mineral oil and straw mulching are complementary and reduce the year-to-year variation observed with oil and straw when used alone as PVY control agents. The results also demonstrate the efficacy of intercropping for the control of PVY, and the mode of action of this novel control method is discussed. Overall, this work shows that it is possible to increase the protection of potato fields against PVY spread by combining control strategies with different modes of action that complement each other, such as mulching, oil spraying and intercropping.

Biological control of a univoltine race of European corn borer, Ostrinia nubilalis Hübner (Lepidoptera: Crambidae), by Trichogramma in Switzerland is currently timed according to repeated, semi‐field observations of the post‐diapause development of the pest at one site. We developed a phenology model with the aims of replacing this costly labour practice and by considering the Swiss landscape. Observations collected over 29 years were used for model calibration and validation. We parameterized a time‐varying distributed delay model based on published laboratory observations of development durations at constant temperatures. The model was driven with hourly temperature recordings beginning on January 1. The calibration of the mean development rates and their variations was based on semi‐field data of larval and pupal development. The model, with its calibrated parameters and their variations, allowed the simulation of mean predictions and prediction intervals. We validated the model predictions of emergence with flight data (obtained via light traps) from several sites in western and northern Switzerland. The simulated mean emergence was 6.9 degree‐days earlier than the observed flight at the calibration sites and only 0.5 degree‐days earlier than the observed flight at other sites. Our simulation of pupation explained half of the variation in emergence time, whereas semi‐field observations of pupation explained three‐quarters of this variation. Our model simulations are not subjected to the local potential biases. Simulation errors from a year with an extremely dry spring were explained by the lack of consideration of humidity by the model. Our simulations provide a valid and less labour‐intensive alternative to observations for timing biological control in the maize‐growing areas of Switzerland and likely other areas of Europe.

We compiled data from the Swiss seed certification programme for the country-wide incidence of viruses in seed potato crops for the years 1989-2012. Model selection techniques were used to regress year-to-year variation in the incidence of potato viruses -largely dominated by Potato virus Y (PVY) -in three susceptible varieties against the abundance of virus vectors (winged aphids), obtained in a suction trap, to identify the most important vector species. The ultimate aim of this study was to develop a decision-support system capable of forecasting virus spread during the current season using trap data of aphid flights. The average virus incidence in the varieties Bintje, Sirtema and Charlotte varied considerably among years, ranging from 1.0% in 2009 to 13.6% in 1989 (N = 150-611 seed lots per year). A linear regression model including the cumulative sums (until mid-June) of two aphid species (Brachycaudus helichrysi and Phorodon humuli) as predictor variables for virus disease was remarkably well supported by the data (R 2 = 0.86). Similarly, using counts of B. helichrysi alone resulted in a good model fit (R 2 = 0.81). Cross-validation revealed high predictive accuracy of the model. Although prediction root mean squared errors (RMSE) calculated for different timings of forecasts were high for extremely early forecasts, they rapidly declined for forecasts conducted by the end of May (i.e. 2-4 weeks after potato emergence). Winter temperature (January-February) was positively correlated with the abundance of B. helichrysi in early summer as well as with post-harvest virus incidence. Remarkably, the abundance of Myzus persicae, often considered the main vector of PVY, was not correlated with virus incidence. Taken together, our analysis suggests that the early migrating aphid B. helichrysi, rather than M. persicae, is the main vector of PVY in Switzerland, and that suction trap data are useful for the design of decision-support systems aimed to optimise virus control in seed potato production.