Een invasie van de Nieuw-Zeelandse tarwewants Nysius huttoni in Nederland (Heteroptera: Lygaeidae).

Invasion of the New-Zealand wheat bug Nysius huttoni in the Netherlands (Heteroptera: Lygaeidae) In 2006 the European Invertebrate Survey - Netherlands, by order of the National Plant Protection Organisation, conducted a survey of the distribution and population characteristics of the true bug Nysius huttoni White, 1878. This is originally an endemic species of New Zealand, which was first discovered in the Netherlands in 2002 (Aukema et al. 2005). Presumably this species has been introduced to Europe through the harbour of Antwerp. In New Zealand this species is an economically important pest species, known as the wheat bug (Schaefer & Panizzi 2000). They feed on the seeds of wheat and enzymes in the saliva degrade the gluten giving rise to runny dough that is unsuitable for baking (Schaefer & Panizzi 2000). The goal of the survey conducted in the Netherlands, and partially in Belgium, was to reveal the distribution, the population characteristics such as the phenology and the frequency of the different wing morphs within the populations, and the possible damage to crops. A survey of potential sites was carried out, as well as a standardised monitoring of, first two, and later three, populations. Nysius huttoni occurs throughout the south-western part of the Netherlands (fig. 8, 9), suggesting that the adults are capable of flying over large waterways like the Westerschelde and the Oosterschelde. Nysius can be found on all kinds of waste grounds, even of the smallest size. The only condition is the presence of acrocarpous mosses. The animals do not feed on these mosses, but merely use them as a shelter and as a place to hibernate. During the entire survey period (from April 14 - October 26) adults of Nysius huttoni could be observed in the field. However, the nymphs were first found on April 25. Therefore, in the Netherlands this species apparently hibernates as an adult, as it does in New Zealand. During the monitoring of the populations there were two periods, June 2 - July 31 and September 1 - October 11, in which teneral specimens were found. These are specimens that recently moulted to adult. These two periods, combined with the fact that this species hibernates as an adult, indicates that there are at least two generations per year, presumably more. On average 25% of the individuals of the monitored populations were macropterous. Macropterous individuals have fully developed wings and flight muscles. They can contribute to dispersal over longer distances. There were significantly more macropterous individuals among the females (31.8%) than among the males (20.3%) (p = 0.0001). There were no significant differences between the three populations. No damage to crops could be established. Not one specimen was found inside a crop field, nor among the crops. Besides, no damage to other vegetation could be established at places where N. huttoni was present. Even after a long period of drought no damage could be established. Nysius huttoni is a recent introduction into Belgium and the Netherlands, not known prior to 2002. There are still numerous places with suitable habitat. Waterways pose no barrier for the spread of N. huttoni. Around 25% of the population is macropterous and thus capable of long distance dispersal. Therefore it is expected that this species may spread over the major part of the Netherlands, and probably other parts of north-western Europe.