Biological control is defined as, 'the action of predators, pathogens, and/or parasites in maintaining another
organism's population density at a lower average level than would occur in their
absence'. Biological weed control involves the utilisation of natural enemies for the control of weeds. It may be achieved via direct or indirect action of the biotic agent which can either;
bore into the weed and weaken its structure,
consume or destroy vital plant parts,
reduce weed vigour and reproduction, or
enhance conditions that favour plant pathogen attack.
The objective in biological control is never eradication; it is reduction of weed density to non-economic levels.
