Parthenium - Other Control Methods

Once parthenium weed is established in pastures, control requires maintenance of good grass growth to maximise competition against the plant. This can only be achieved by initial destocking followed by reduced stocking rates to maintain grass competition (Holman and Dale, 1981; Anon. 1997).

While individual parthenium weed plants are easily killed with herbicides, rapid regeneration from seed soon follows. The only successful way to control the plant with herbicides is to use residual pre-emergent compounds and several retreatments are necessary to prevent further seed production (Anon. 1997). The State Government and local authorities in Queensland spent about $1 million in 1989 to control parthenium weed along roadsides, showgrounds and cattle-holding yards (Rural Lands Protection Board reports 1989). $¼ million was spent on control measures on only 5 properties (Herron, pers. comm. 1990), and over $100,000 was spent in NSW eradicating the weed from a single property (I.Kelly, pers.comm. 1993). A recent survey found parthenium weed to be costing Queensland beef producers over $16 million per year (Chippendale and Panetta, 1994).

A biological control program has been in place since 1977, with surveys undertaken in Mexico, Brazil and Argentina. Eight species of insect and a rust disease have been introduced since 1979 (Navie et al 1996). Six species are established; a stem-galling moth Epiblema strenuana (Lep.: Tortricidae), a leaf-mining moth Bucculatrix parthenica (Lep.: Bucculatricidae), a stem-feeding weevil Listronotus setosipennis (Col.: Curculionidae), a stem-galling weevil Conotrachelus sp. (Col.: Curculionidae), a seed-feeding weevil Smicronyx lutulentus (Col.: Curculionidae), and a leaf-feeding beetle Zygogramma bicolorata (Col.: Chrysomelidae), and the rust Puccinia abrupta var. partheniicola. Their combined impact is currently being evaluated in a 3-year project (Dhileepan et al. 1996). Preliminary results indicate that the impact is significant in wetter years and zones, reducing the weed’s competitiveness and assisting management in grazing properties. Control is however far from adequate and parthenium weed is still one of the major weeds of the brigalow soils of central and northern Queensland (V. Pope, unpub. data, 1990).