The principles and practice of using fungal pathogens to
control both weed and insect pests are outlined. It is emphasized that a clear distinction
should be made between natural control, resulting from the direct action of natural
enemies, and biological control, achieved by the deliberate manipulation of natural
enemies by man.
The past history of
research on entomopathogenic fungi in Sri Lanka is traced and discussed, highlighting the
pivotal role played by early colonial scientists, such as Tom Petch, in elucidating their
ecology and systematics. The actual and potential exploitation of entomopathogenic fungi
as biological control agents is reviewed.
Several plant species, such as
Dichrostachys cinerea, Ligustrum robustum and Rottboellia cochinchinensis, which are
indigenous to but generally uncommon in Sri Lanka, have become major invasive weeds in
exotic situations, particularly in the Neotropics. In contrast, a number of native,
neotropical plant species, such as Chromolaena odorata, Eichhornia crassipes, Lantana
camara and Mimosa pigra, which are typically only minor weeds in Latin America, have
become invasive in Sri Lanka, posing a threat to both agricultural and natural ecosystems.
These examples are discussed in relation to the role of natural enemies, with particular
reference to fungal pathogens, in the regulation of plant populations and their use as
classical biological control agents.