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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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This chapter discusses topics on Western corn rootworm (WCR), Diabrotica virgifera virgifera, biology and history, resistance to crop rotation (in maize and soyabean fields), WCR movement, movement and the WCR life cycle, factors influencing movement, measuring movement, diet and movement, and diet and mechanisms of rotation resistance.

The effect of any management strategy on pest population levels must be researched and determinations need to be made as to how that strategy might work based on the control objectives. In certain areas of Europe, the objective is to contain or eradicate the western corn rootworm (WCR), Diabrotica virgifera virgifera LeConte, population. In order to evaluate the impact of insecticide seed coatings and/or planting-time applications of insecticides as WCR population suppressors, plot trials and large field observations were carried out in Italy over a 5-year period. Larval, pupal and adult densities, along with root damage ratings, were estimated at different locations. Data from these studies revealed that the number of WCR adults emerging from untreated plots did not differ from the number of beetles emerging from those treated with insecticides, whether as seed coating or in-furrow applications. Both seed insecticide coatings (imidacloprid, fipronil, thiamethoxam, tefluthrin) and soil insecticides applied in-furrow (chlorpyrifos, diazinon, tefluthrin) did not reduce the number of beetles emerging from monoculture fields, either in plot trials or large field observations. Observations in the USA had previously shown that soil insecticides applied at planting time partially protected basal roots from economic damage, but did not reduce corn rootworm populations. Similarly, in Europe, it has been demonstrated that not only the application of soil insecticides at planting time but also insecticide seed coatings have no role in the containment and/or eradication of WCR. Although insecticide seed coatings and soil insecticides applied in-furrow may provide protection against economic damage to roots, these management strategies do not have an impact on WCR populations and therefore are useless in WCR containment and eradication programmes.

This chapter presents an overview on the hypotheses for the development of the new rotation-tolerant Western corn rootworm (WCR) variant, attraction of different crops to WCR adults and their feeding on non-maize crops, development of WCR adults in maize following different crops, and population level of WCT adults in different crop stands in the USA. Results are also presented of an experiment conducted in Hungary in 2000.

Sweep-nel sampling and pilfalllrapping were used 10 survey insects in weedy and weedfree soybean habitals. Weedy soybean habitats consisted of (I) grassy soybeans; (2) soybeans with broad leaf weeds; and (3) soybeans with broadleaf weeds and grasses. Insect species diversity was greater in weedy soybean habitats than in weed-free soybeans. Greatest diversity of species occurred in Ihe mixed-weed soybean habitat. The most imponant phytophagous insect on soybeans in Indiana, the Mexican bean beetle, Epilachlla varivestis Mulsant, was mOSI abundanl in weed-free soybeans. Predators were mosl ahundanl in weedy soybeans. Coit'omeKilla marl/lata (DeGeer) was mllsl abundant in weedy soybean habitats, whereas Orius insidiosus (Say) and Nabis spp. were most abundant in soybean habitats with grasses and mixed weeds. In the pitfall trapping study, Harpalus spp. were more abundant in soybean habitats with grasses and mixed broad leaf and grass weeds. I 1 IAnnual weeds arc often a major component of soybean fields, yet little is known of insect-weed interactions in soybeans. Several studies indicated that weeds increase the diversity and abundance of insects in soybeans. Balduf (1923) surveyed thc in~cct fauna of soybeans and surrounding vegetation in Ohio. He reported that most of the 209 species collected were associated with weeds. In Minnesota, Kretzschmar (1948) reported that weedy soybeans had a larger and more diverse insect fauna than weed-free soybeans. In Arkansas, Tugwell et al. (1973) made sweep-net collections in soybeans and a weed host, Desmodium sp., growing adjacent to the soybeans. Of 133 species collected from Desmodium sp., 93 were also collected on soybeans.Although plant species diversity is generally associated with a diverse insect fauna, monocultures sometimes support a greater herbivore load than diverse plantings. Pimental (1961) and Smith (1976) found that colonizing aphids were more attracted to weed-free brussels sprouts, Brassica oleracea L., than sprouts grown with weeds. Tahvanainen and Root (1972) suggested that diverse vegetational communities exude so many different chemicals that herbivores may be confused and consequently seek simpler floral systems.This study was conducted to determine how annual weeds affect the diversity and abundance of insects in soybeans. Materials and MethodsResearch was conducted in southern Indiana during the summers of 1978 and 1979. The study area was a 5.7-ha field which had been in continuous soybeans for several years. The field was divided into 12 plots (30.5 by 30.5 m), with each of the four treatments (weed-free, broadleaf weeds, grass weeds, and mixed weeds) rep-' licated three times in a randomized complete block design.TrifJuralin (1.75 liters/ha) was applied preplant to broadlcaf-weed plots to control grasses, and metribuzin (0.83 kg/ha) was applied preplant to grass-weed plots to control broadleaf weeds. Weed-free plots and border areas were kept virtually weed free by preplant application of metribuzin and trifJuralin at the rate above, ...