Oct 6, 2003

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Western corn rootworm

Beetle alert reaches Germany

This summer the Western corn rootworm was discovered for the first time near the German border – close to Basel/Mulhouse Airport – triggering a cross-border beetle alert.

The maize pest was first spotted in Europe at the beginning of the 1990s near Belgrade Airport and has been steadily spreading in all directions. Last year the beetle suddenly appeared near Paris and has now reached Alsace. Beetle traps have been set in Bavaria and Baden-Württemberg in expectation of the pest since 1997 so that its arrival will be noted promptly. Appropriate zone restrictions could at least delay the pest’s spread.

Western corn rootworm . Photo: Marlin E. Rice

It is the larvae that cause the most damage. They eat the roots and have a detrimental effect on the plant’s water and nutrient uptake and on its stability. If a maize plant suffers severe grazing damage, it snaps just above the ground. In regions with intensive maize farming it takes five to seven years from initial colonisation to noticeable economic damage.

A safety zone has been set up around the site where the beetle was discovered in Basel/Mulhouse. This zone crosses the German border. Within this zone around 100 hectares of silo maize are to be chopped up by mid-August and used only on-site. All other maize fields have been treated with an insecticide, for which an emergency licence first had to be obtained.

Since the beetle lays its eggs only in the roots of maize plants, fields in which maize is gown successively offer ideal conditions for it. This is why the most sustainable measure recommended for combating the pest is crop rotation, and there is even talk of banning the cultivation of successive maize crops at European level.

In the USA genetically modified maize designed to combat the pest is currently being tested. Based on the Bt concept, this maize produces a toxin within the plant that kills the pest.

In the EU as well, authorisation has been applied for for a genetically modified maize plant produced from a cross between two Bt maize lines (MON 863 x MON 810) which is effective against the Western corn rootworm. The application relates to maize imports; there are no plans to cultivate it in the EU.

The Berlin-based Robert Koch Institute – the German authority responsible – has no safety concerns and recommends that the maize be approved, but only until the end of 2004, since the maize plants contain an antibiotic-resistance marker.