Life history of Anomalococcus indicus (Hemiptera: Lecanodiaspididae), a potential biological control agent for prickly acacia Vachellia nilotica ssp. indica in Australia

Abstract

Babul scale Anomalococcus indicus Ramakrishna Ayyar, a major pest of Vachellia nilotica (L.f.) P.J.H. Hurter & Mabb. on the Indian subcontinent, has been identified as a potential biocontrol agent for prickly acacia V. nilotica subsp. indica (Benth.) Kyal. & Boatwr. in Australia and was imported from southern India for detailed assessment. The life history of A. indicus under controlled glasshouse conditions was determined as a part of this assessment. Consistent with other scale species, A. indicus has a distinct sexual dimorphism which becomes apparent during the second instar. Females have three instars, developing into sexually mature nymphs after 52 days. The generation time from egg to egg was 89 days. Females are ovoviviparous, ovipositing mature eggs into a cavity underneath their body. An average of 802 ± 114 offspring were produced per female. Reproductive output was closely associated with female size; larger females produced more than 1200 offspring. Crawlers emerged from beneath the female after an indeterminate period of inactivity. They have the only life stage at which A. indicus can disperse, though the majority settle close to their parent female forming aggregative distributions. In the absence of food, most crawlers died within three days. Males took 62 days to develop through five instars. Unlike females, males underwent complete metamorphosis. Adult males were small and winged, and lived for less than a day. Parthenogenesis was not observed in females excluded from males. The life history of A. indicus allows it to complement other biological control agents already established on prickly acacia in Australia.

Keywords:

• Acacia nilotica
• biological control of weeds
• Coccoidea
• life cycle

Acknowledgements

We would like to thank Mariappan Senthilkumar, Selvaraj Murugesan and Ayyapillai Balu from the Institute of Forest Genetics and Tree Breeding in Tamil Nadu, India, for their assistance with collecting and shipping the insect to Australia. Bill Palmer, Tony Pople and three anonymous reviewers provided valuable comments on earlier drafts.

Funding

This research was funded by Meat and Livestock Australia.

Notes

1. The genus Acacia sens. lat. has been provisionally divided into five genera: Acacia, Vachellia, Senegalia, Acaciella and Mariosousa. Acacia (sensu stricta) has been retypified so that the majority of species within Acacia s.l. (i.e. Acacia subg. Phyllodineae) retain this name. See Maslin, Miller & Seigler (2003) and Miller & Seigler (2012).

Additional information

Funding

Funding: This research was funded by Meat and Livestock Australia.