Plant Protection Quarterly Vol.16(2) 2001 63 problems due to parthenium also occur in several parts of Asia, Africa and the Car- Gall-inducing insects and biological control of ibbean (Navie et al. 1996, Mahadevappa Parthenium hysterophorus L. (Asteraceae) 1997). Parthenium hysterophorus is a vigorous A,B A B and fast-growing annual plant that pro- S.K. Florentine , A. Raman and K. Dhileepan duces nearly 60 000 florets, each bearing A The University of Sydney – Orange, PO Box 883, Orange, New South Wales one seed (K. Dhileepan, unpublished ob- 2800, Australia. servations). The seeds persist in the soil B Tropical Weeds Research Centre, Department of Natural Resources, PO Box for a long time, with nearly 50% of the 187, Charters Towers, Queensland 4820, Australia. seed bank remaining viable up to six years (Navie et al. 1998). Different chemical, biological and cul- tural methods have been adopted to man- Summary Introduction age this weed in Australia and in other Weeds invade agricultural ecosystems Parthenium hysterophorus L. (parthenium parts of the world. Use of herbicides has and degrade productive land. Parthen- weed, white top, false ragweed) was acci- proved uneconomic (Holman and Dale ium hysterophorus, introduced acciden- dentally introduced into Australia from 1981). Biological control offers great po- tally into Australia from the United the United States of America. It was first tential to minimize and manage P. hystero- States of America, not only affects pro- recorded in Queensland in the 1950s phorus, especially in the heavily-infested ductive land, but also causes severe (Everist 1976). At present it is reported areas of Central Queensland (McFadyen health problems to humans. Since gall- throughout much of Queensland and oc- 1992). inducing arthropods are increasingly be- curs in small pockets along roadsides in As an effort towards biological control, coming useful in weed management northern New South Wales (McFadyen nine insect species and one pathogenic campaigns, we discuss in this paper the 1995) and in the Northern Territory rust fungus from Central America were benefits of using gall-inducing insects in (Navie et al. 1996). In the last two decades, released in Queensland between 1980 and the biological control of weeds, targeting this species has caused severe economic 1999 (Table 1). Among these, a gall-induc- P. hysterophorus which is a major prob- and ecological impacts in Queensland. It ing moth, Epiblema strenuana Walker lem weed in Queensland. We evaluate has spread to nearly 170 000 km2 in (Lepidoptera: Tortricidae) and a gall- the capability of two gall-inducing in- Queensland with an estimated loss of inducing weevil, Conotrachelus albocinereus sects against P. hysterophorus. The gall- farm productivity up to 40% (Chippen- Fiedler (Coleoptera: Curculionidae) ap- inducing moth, Epiblema strenuana and dale and Panetta 1994). It is a serious pear to have the potential for control- the gall-inducing weevil, Conotrachelus health hazard and induces allergic derma- ling P. hysterophorus (McFadyen 1992, albocinereus display significant morpho- titis, hay fever and asthma in more Dhileepan et al. 1996, Raman and logical and physiological impacts on P. than 20% of the exposed population Dhileepan 1999, Treviño et al. 1999, hysterophorus indicating them to be ef- (McFadyen 1995, Cheney 1998). Manage- McFadyen 2000). This paper discusses the fective organisms for use in biological ment of this species is expensive (Chip- strengths and advantages of using the gall control in Australia. pendale and Panetta 1994) and control moth and the gall weevil for the manage- programs from 1977 to 1992 have cost ment of P. hysterophorus, as well as sum- nearly $3.5 m in Australia (McFadyen marizes the benefits in using galling ar- 1992). Severe economic and health thropods in weed management and the Table 1. Biological control agents released in P. hysterophorus-infested areas in Australia. Biological Country Year of Year of Biology Impact References control agents of origin release establishment on host Bucculatrix parthenica Mexico 1984–85 na Leaf mining + McClay et al. (Lepidoptera: Bucculatricidae) (1990) Conotrachelus albocinereus Argentina 1995–97 2000 Stem galling na McFadyen (Coleoptera: Curculionidae) (2000) Carmenta ithacae Mexico 1998–99 2000 Root boring na Dhileepan (Lepidoptera: Sesiidae) (pers. obs.) Epiblema strenuana Mexico 1982–85 1983 Stem galling +++ McFadyen (Lepidoptera: Tortricidae) (1989) Listronotus setosipennis Brazil and 1982–86 1983 Stem boring ++ Wild et al. (Coleoptera: Curculionidae) Argentina (1992) Platphalonida mystica Argentina 1992–96 na na na Dhileepan and (Lepidoptera: Tortricidae) McFadyen (1997) Smicronyx lutulentus Mexico 1981–83 1996 Seed feeding + McFadyen and (Coleoptera: Curculionidae) McClay (1981) Stobaera concinna Mexico 1983–85 1992 Sap sucking Nil Dhileepan and (Hemiptera: Delphacidae) McFadyen (1997) Zygogramma bicolorata Mexico 1981–83 1990 Leaf feeding +++ Dhileepan and (Coleoptera: Chrysomelidae) McFadyen (1997) Puccinia abrupta var. parthenicola Mexico 1992 1994 Pustule forming na Dhileepan and (Fungi: Uredinales) on leaves McFadyen (1997) + = low. ++ = moderate. +++ = high. na = data unavailable. 64 Plant Protection Quarterly Vol.16(2) 2001 nature of physical and physiological (1996) indicate the vulnerability of the damage caused by these arthropods. host plant to moisture stress and the gall acting as a metabolic sink as the key Why gall-inducing insects hold strengths in using gall insects in weed promise in weed control? management. Use of plant-feeding arthropods and pathogenic fungi is preferred in weed Mechanism of damage by gall- management programs, because such a inducing insects practice is ecologically sound and eco- Gall-inducing insects play a major role in nomically viable (Shepherd 1993). Gall- redirecting photo-assimilates from the ac- inducing insects have played a key role in tive meristems of the host to the gall site biological weed control activities through- (Abrahamson and Weis 1987). An active out the world (Julien and Griffiths 1998). gall performs as a metabolic sink trapping Among plant-feeding insects, only those the nutrients and transporting them to tis- belonging to 20 Families classified under sues lying close to larva, through localized seven Orders have the ability to induce cellular modifications (Raman 1987, galls on their host plants. Within the Rohfritsch 1988). Galls act as sinks of en- broad context of insects used in weed bio- ergy as well, to subserve the nutritional logical control, only 2% of them are gall needs of the parasitic galler (Stinner and inducers (Meyer 1987). Gall-inducing in- Abrahamson 1979, Raman and Abraham- sects have a narrow host range and they son 1995). High levels of soluble nutrients severely impair the growth and develop- such as the sugars and amino acids exist ment of the host plant (Harris and in the feeding layers of tissues in galls (Ra- Shorthouse 1996). They induce structural man 1994). In the galls induced by (Lalonde and Shorthouse 1984, Raman Phanacis taraxaci on the common dande- and Dhileepan 1999) and metabolic lion (Taraxacum officinale), up to 70% of changes (Daley and McNeil 1987, carbon was redirected to the gall, to pro- Paquette et al. 1992, Raman 1994) in the vide nutrition to the growing larva Figure 1. Epiblema strenuana- host plant. Their ability to significantly af- (Bagatto et al. 1996). In addition to photo- induced gall on P. hysterophorus, fect host-plant growth and metabolism, assimilates, galls accumulate mineral nu- cut open longitudinally to show the and their narrow host range indicate that trients in their specialized nutritive tissue mature larva (scale bar: 1 mm). they could be an ideal group for the (Abrahamson and McCrea 1985, Short- biological control of weeds. The gall house and Gassmann 1994). During early weevil, Rhinocyllus conicus (Coleoptera: stages of development of galls induced by through a window cut by the mature larva Curculionidae) on the thistles (Carduus Hemadas nubilipennis on Vaccinium angusti- before pupation (McFadyen 1986, Raman nutans and C. acanthoides) (Shorthouse and folium, minerals such as copper, nickel, and Dhileepan 1999). Lalonde 1984); the seed-fly, Urophora iron and zinc remained higher in the The weevil, C. albocinereus is active at cardui (Diptera: Tephritidae) on Cirsium galled tissue than in the ungalled tissue night and feeds on the stems and leaves of arvense; the fly, Pegomya cutricornis (Bagatto and Shorthouse 1994, Shorthouse P. hysterophorus. Adults live for up to three (Diptera: Anthomyiidae) on Euphorbia et al. 1986). Early developmental pressure months. The female weevil chews the epi- virgata and E. esula (Shorthouse and of galls acting as the nutrient sinks for the dermal and outer cortical tissue of the Gassmann 1994); the stem-gall fly, inhabiting insect increases energy alloca- shoot. She lays eggs singly in the feeding Procecidochares utilis (Tephritidae: Diptera) tion from the storage reserves of the plant scar sites and sometimes on leaf axils and on Eupatorium adenophorum (Swaminthan organ; in some instances, the development covers them with frass. A neonate larva and Raman 1981) are some of the well of the insect progeny depends on the re- bores directly into the stem (Figure 2). The documented examples of gall inducers sources mobilized at the galled organ (e.g. larvae remain inside the gall until mature, used in weed management practice. leaf) and from the immediate neighbour- and then move to