Tuesday, November 2, 2010

Carabid Controller

The carabid beetle, Pterostichus madidus is a very common ground beetle that although being mainly active at night, is often seen in the day time if disturbed from under stones of logs. It is readily identified by its shiny, black body, the fine grooves in its elytra and its typically reddish legs (Sterry, 2004 Collins Complete Guide to Irish Wildlife p. 146). P. madidus is sometimes called the strawberry beetle as it feeds on strawberries as well as other fruit, but it is mainly carnivorous (Chinery, 1997 Collins Gem Insects, p. 129).
Pterostichus madidus
Quantitative ELISA analysis of crop content of the beetle has shown that quite a large proportion of its diet has consists of molluscs (Symondson and Liddell, 1993 Bulletin of Entomological Research 83 pp. 641-647). This feeding habit was shown to posit P. madidus as a potential biological control agent for slugs and snails by a glasshouse experiment (Asteraki, 1993 Entomophaga 38 193-198). This demonstrated that it controlled slug (Deroceras reticulatum) populations in a grass/clover sward. However Mair and Port (2001, Agricultural and Forest Entomology 3 pp. 99-106) have shown that the original serological tests may have been misleading as they showed that dead slugs were consumed by P. madidus in preference to live ones in laboratory conditions. Live slugs that were killed and consumed were quite small (<0.11 g). Yet the use of P. madidus to control molluscan pests is still a viable alternative to chemical means, as long as it is combined with methods to control the larger individuals.

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