Farmers in Australia are now being advised to spray additional insecticide on Monsanto's GM Bt cotton known as INGARD "under conditions of reduced INGARD plant efficacy".

The latest official guidance (RESISTANCE MANAGEMENT PLAN FOR INGARD®  COTTON 2001-2002 - Transgenic and Insect Management Strategy (TIMS) Committee of the Australian Cotton Growers Research Association - http://www.cotton.pi.csiro.au/Publicat/Pest/IRMS/irms0102.htm
makes it clear that Bt is in some circumstances failing to control the principal target pest it was introduced for.  This pest is known as Helicoverpa armigera.