The effects of host plant odours on the calling behaviour, egg maturation and mating success of the cotton bollworm, Helicoverpa armigera (Lepidoptera: Noctuidae)

O.L. Kvedaras 1 , P.C. Gregg 1 , A.P. Del Socorro 1 , D. Alter 1 & C. Moore 2

1 School of Rural Science and Nat. Res., Univ. of New England, Armidale, New South Wales, Australia 2351; 2 Queensland Dept. of Primary Industries, Yeerongpilly, Queensland, Australia 4105

The influence of host plant odours on the calling behaviour and egg maturation of the female cotton bollworm, Helicoverpa armigera was investigated. Host plants included flowering cotton, maize and pigeon pea. Females were held in cages for a period of 6 days from the time of emergence and exposed to either no host (control) or a host plant. The time calling was initiated, time spent calling and the mean number of calling bouts were recorded. A selection of females that initiated calling for the first time 1-6 days after emergence were sacrificed to determine the stage of ovarian development at the onset of calling. In a separate experiment the sex pheromone released by individual calling females of H. armigera was trapped within the stem of Pasteur pipettes. Individual females were exposed to host plant odours and one female was exposed only to filtered air as a control. Host plants included, cotton, pidgeon pea and sunflower. The time spent calling was recorded and the amount of pheromone trapped quantified. Pheromone collection and behavioural observation commenced halfway into scotophase which is generally when female H. armigera start calling. Trapped pheromone was analysed by Gas Chromatography-Mass Spectrometry. Field studies were conducted in the Darling Downs, Queensland, Australia, during the 1996/97 and 1997/98 cotton growing seasons. Mating tables were used to determine the mating success of H. armigera. Moth abundance was assessed using light and pheromone traps. A series of comparisons of three or four crops were used. They included: mature corn; immature, flowering and mature cotton and soybeans; immature and flowering sunflower and sorghum. Fallow land was also included. Laboratory reared virgin females with their wings clipped were placed in mating tables in various crops where they remained until collection and dissection the following morning to determine whether they had been mated. These studies indicate that host plants did not significantly influence the chance of being mated, despite substantial variation in moth abundance between the crops.

Index terms: Helicoverpa armigera, host plants, mating tables, ovarian development, sex pheromone

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