Biology Reference
In-Depth Information
et al. 1996; Tamado and Milberg 2000; Tomado et al. 2002a) as well as serious
environmental problems (Chippendale and Panetta 1994). In Australia, parthenium
affected over 170,000 km
2
of grazing land in Queensland (Chippendale and Panetta
1994; McFadyen 1992) and reduced beef production by AUD 16.5 million annually
(Chippendale and Panetta 1994). In India, parthenium caused yield losses of up to
40% in crops (Khosla and Sobti 1979) and reduced forage production by up to 90%
(Nath 1981). Parthenium has reduced the species richness and species diversity of
other plant species (Sridhara et al. 2005) and their seed banks (Navie et al. 2004).
Parthenium also acts as a reservoir host for plant pathogens and insect pest of crop
plants (e.g. Basappa 2005; Evans 1997a; Govindappa et al. 2005; Navie et al. 1996;
Rao et al. 2005; Robertson and Kettle 1994). Parthenium and related genera contain
sesquiterpene lactones (Picman and Towers 1982), which induce severe contact
dermatitis and other allergic symptoms (Towers 1981). Stock animals, especially
horses, suffer from allergic skin reaction while grazing infested paddocks.
Parthenium is generally unpalatable and toxic to cattle, buffalo and sheep (e.g.
Narasimham et al. 1980; Kadhane et al. 1992). Consumption of large amounts will
produce taints in mutton (Tudor et al. 1982) and can even kill livestock.
12.4 ManagementOptions
Chemical control is the first line of defence (Holman 1981), but high costs of her-
bicides prohibit their long-term use for parthenium management in grazing areas,
public and uncultivated areas and forests. To eradicate localised infestations, for
roadside infestations or when the weed is a problem in certain crops, control can be
achieved by using herbicides (e.g. Holman 1981). In areas where chemical control
is not economical, other options such as the use of competitive plants to displace
parthenium (e.g. Joshi 1991a, b; O'Donnell and Adkins 2005), fire (Vogler et al.
2002) and other physical methods including mulching green parthenium plants
have been suggested as suitable options either individually on in combinations.
12.4.1 ChemicalControl
Herbicides, either as pre- or post-emergence application, can provide effective con-
trol of parthenium in crops (e.g. Holman 1981; Navie et al. 1996; Dawson and
Sarkar 1997), infestations along road side (e.g. Brooks et al. 2004) and wasteland
(e.g. Dixit and Bhan 1997; Yadav et al. 1997). The effectiveness of herbicides
depends on the timing of application, and often more selective herbicides are pre-
ferred to minimise non-target damage. Chemical control is the first line of defence
in eradication and containment programs. Chemical control is also the most suita-
ble option for managing parthenium in urban areas, to reduce human and animal
health impacts as well as in high-value crops. However, high costs of herbicides
