64 Plant Protection Quarterly VoI.9(2) 1994 similar scales were described by Froggatt Biological control of the native shrubs Cassinia spp. (1903), no data on their biology were available. Thus observations began on using the native scale insects Austrotachardia sp. and Austrotachardia sp. in 1988 and Para­ Paratachardina sp. (Hemiptera: Kerriidae) in New tachardina sp. in 1991 to record their biol­ ogy and to ascertain whether they could South Wales be used for the biological control of Cassinia spp. M.H. Campbell', R.H. Holtkamp', L.H. McCormick', P.J. Wykes', J.F. Donaldson', P.J. Gulian' and P.S. Gillespie'. Life cycle of Austrotachardia sp. and Para tach ardin a sp. Austrotachardia sp. was s tudied at 1 NSW Agriculture, Agricultural Research and Veterinary Centre, Forest "0aydawn", Kerrs Creek and at the Agri­ Road, Orange, New South Wales 2800, Australia. cultural Research and Veterinary Centre, ' NSW Agriculture, Agricultural Research Centre, Tamworth, New South Orange. Paratachardina sp. was studied in Wales 2340, Australia. the Tamworth and Manilla districts. ' NSW Agriculture, Manilla, New South Wales 2346, Australia. Fi rs t-instar nymphs (crawlers) of • "Daydawn", Kerrs Creek, New South Wales 2741, Australia. Austrotachardia sp. (Figure 1) (orange in ' Department of Primary Industries, lndooroopilly, Queensland 4068, colour and 0.5 mm long) emerged in De­ Australia. cember 1990 and established on stems of ' Division of Botany and Zoology, Australian National University, Canberra, C. arcuata. Initially, all second-instar ACT 2600, Australia. nymphs appeared identical. However, by February 1991, the red, oblong (1.5 x 0.6 ' Biological and Chemical Research Institute, Rydalmere, New South Wales mm) male tests were distinguishable 2116, Australia. &om the red, oval (1 mm diame ter) fe­ male tests (Figure 2). The red-coloured Summary soil or plant disturbance and become male fli es emerged in March 1991, but it is Naturally occurring populations of the weeds because they are unpalatable, com­ not known whether fertilization occurred native scale insects A ltstrotaC#,ardia sp. petitive, unproductive and difficult and a t this time because mating was not ob­ and Paratacharditra s p. killed large ar­ costly to control (Campbell el al. 1990). served. Sca le insects reproduce by a vari­ eas of native Cassi"ia s pp. in, respec­ They also p rovide harbour for noxious ety of means including hermaphroditism, tively, central and no rth-western New animals and make stock mustering diffi­ parthenogenesis and normal fertilization South Wales, from 1988 to 1993. These cult. The four main species are Cassinia (O'Brien el al. 1991). scales, which are specific to Cassi,Jia arcuala R.Br., C. IOll gifolia R.Br., C. lnevis Females of Austrotachardia sp. grew spp., have been wide ly spread through R.Br . and C. quinque/aria R.Br. C. arcuata slowly during winter 1991, increasing New South Wales by the transfer of in­ has invaded 616 000 hectares in central from 1.5 mm to 2.0 mm in diameter. As fested cuttings by humans. Observa­ and southern New South Wa les and is a the females matured, embryos appeared tions on one pro perty near Orange re­ declared noxious weed in 10 shires vealed that deliberate transfe r of (Campbell 1990, Campbell et al. 1990). A ustrotacltardia sp. assisted in killing Preliminary estimates indicate C. laevis 70% (255 ha) of C. arcuata on the prop­ and C. qUinquefaria are present on 250 000 erty between 1988 and 1993. Cassillia hectares in north-western New South spp. a re us ually re placed by native Wales. On arable land Cassinia spp. can grasses; however, poor management can be controlled by ploughing, sowing im­ lead 10 re-infes tation by woody weeds. proved pastures and applying fertilizers Both scales have a n annual life cycle and to overcome nutrient deficiencies and soil are spread b y transferring infected acidity (McGowen et al. 1990). On non­ cuttings to ne w plants 10 to 30 days be­ arable land conventional methods of con­ fo re firsl-instar nymphs e me rge. A com­ trol e.g., spraying and aerial distribution Figure 1. First·instar nymphs plex o f paras ito ids a nd pred ators, of pasture seed and fertilizers, are imprac­ (crawlers, 0.5 mm long) of Austro­ mainly small wasps, may limit the effec­ tical because herbicide treatments are un­ tachardia sp. emerge in summer or tiv~n ess of the scales in controlling economic and pasture establishment dif­ Cassinia spp. Pa rasito ids ca n be par­ ficult on the unploughed acid soils autumn ; transfer of infected tially contro lled by d estroying cuttings (Campbell 1990). cuttings should take place 10 to 30 immediately after crawler emergence Native scale insects have killed small days before crawler emergence. because they continue to eme rge for up a reas of C. arcuata and C. longifolia in cen­ to seven months after the crawlers. This tral New South Wales since 1979 O.j. study indicates thai if humans assist by Dell ow, NSW Agriculture, Orange, per­ spreading scale insects and controlling sonal communication) and patches of C. parasito id s and predators the scales laevis and C. quinquefaria in north-western could be useful biological agents for the New South Wales since 1988. However, control of Cassi"ia spp. between 1988 and 1993 relatively large ar­ eas of Cassinia spp. were killed by Introduction Austrotachardia sp (Hemiptera: Kerriidae) Cassillia spp. (Asteraceae), native shrubs in central New South Wales (Campbell widespread in New South Wales, Victo­ and Wykes 1991, 1992) and by Para­ ria and Queensland (Campbell 1977, tachardina sp. (Hemiptera: Kerriidae) in Figure 2. An oblong male nymph 1990), generally grow on infertile acid north-western New South Wales (Holt­ (centre) surrounded by six oval soils. They invade pastures in response to kamp and Campbell 1992). Although females of Austrotac1.ardia sp. Plant Protection Quarterly VoI.9(2) 1994 65 test and the adults emerge by cutting a Scott 1982). Although ants assist round hole in the test. Often female scale homopterans by carrying them (e.g., insects produce crawlers despite the pres- Pseudococcus spp.) to new habitats ence of a wasp larva. Wasps continue to (Strickland 1958, Way 1963) we have not emerge after crawler emergence has observed such assistance for Austro- ceased; for example, in the early autumn tachardia sp. and Paratachardina sp. 1993 Austrotachardia sp. population, 61% of wasps emerged in the two months af- Other insects and animals ter crawler emergence had ceased and Honeydew from Austrotachardia sp. and continued to emerge for a further seven Paratachardina sp_ attracted honeybees, Figure 3. A fully developed Austro­ months. This indicates that cuttings at­ ladybird beetles, hoverflies, wasps and tachardia sp. female one year old. tached to new plants to spread Austro­ blowflies which did not harm the scale tachardia sp. should be destroyed after insects. However, rabbits, hares, sheep inside and developed into crawlers that crawler emergence (Campbell and Wykes and goats often ate the scale insects which emerged in December 1991. Thus the life 1991, Campbell 1992) to reduce wasp was most detrimental when a new colony cycle of the population that began at numbers. was establishing. Kerrs Creek in December 1990 was ap­ The larvae of an undetermined moth proximately one year (Figure 3). Another (Lepidoptera: Coleophidae) predate on Fungi population, that began with crawlers in Austrotachardia sp., spinning a protective Austrotachardia sp. and Paratachardina sp. February 1991, had males emerging and web under which they feed. A dark are commonly covered by the black sooty females 1 mm in diameter in December brown beetle, Trogoderma sp., (Coleop­ mould, Capnodium walter; (Ascomyco­ 1991, and crawlers emerging in February tera: Dermestidae), a black and white tina), which does not seem to harm them 1992. These two populations repeated moth, Macrobathra sp. (Lepidoptera: because large numbers of crawlers are their respective life cycles in 1992/93 and Cosmopterigidae) and an unidentified produced from completely covered fe­ 1993/94; crawlers from the first popula­ case moth (Lepidoptera: Psychidae), are males. tion emerged in January 1993 and Decem­ often present; their larvae are suspected ber 1993 and those from the second, in of feeding on crawlers, females, dead Distribution of the scale insects March 1993 and March 1994. The two lat­ scales or detritus. No detailed survey has been carried out ter emergences were later than in 1991/ Despite these predators and parasites, on the distribution of Austrotachardia sp. 92. Buckley (1987) recorded that climatic populations of Austrotachardia sp. and and Paratachardina sp. in New South and habitat factors may affect ant-plant­ Paratachardina sp. increased markedly Wales. However Austrotachardia sp. has homopteran interactions and regulate from 1988 to 1993 and the transfer of been observed on Cassinin spp. between population dynamics. Thus, lower than scales from infected plants to new plants Gulgong and Uarbry, north of Coolah, normal temperatures and higher rainfall was successful. throughout the Pilliga scrub, Bathurst, in 1992 (average daily mean 11.2·C and Hill End and in a 40 kilometre arc north total rainfall 1322 mm in 1992 compared Ants of Orange. Paratachardina sp. has been ob­ with the 100 year average of 12.1 °C and Ants observed tending Austrotachardia sp. served in the Tamworth, Armidale, 901 mm) may have increased the length included Iridomyrmex rufoniger (Lowne), Inverelt Tenterfield, Glen Innes, Bingara, of the life cycle of Austrotachardia sp. It 1. purpureus (F. Smith), Anonychomyra Barraba, BWldarra, Manilla and Merriwa was also observed that female itillerallS (Lowne) and CampO/lOtus sp. districts. Austrotachardia sp. grew more slowly, (Hymenoptera: Formicidae); the first with a corresponding increase in length of three in daylight and the latter at night.