Page 62 - Ilmu Tanah

The Chemistry and Fertility of Soils under Tropical Weeds 49

Therefore, biological weed control is conducted by introducing weed natural
enemies to make new ecosystem equilibrium so that weed may not cause problem.
The positive thing of this method is the permanent effect of the control so that
after treatment no more intervention to lower the weed population once the
equilibrium is attained. The increase in weed population may always be followed
by the increase in natural enemys population because their feeds is enough. On
the other hand, the weeds may soon decrease and cause the decrease in their
natural enemys population because of less feeds available. This trend will again
stimulate the increase in weed population and this cycle will continue with time.
This is a perfect equilibrium that occurs in an ecosystem which control the
population of weeds and their natural enemies and neither one dominates and
causes problem in an ecosytem.
Weed biological control has been widespreadly practiced in some countries.
As many as 391 biocontrol agents with 150 target weeds had been released in 1990
in five most active countries in biocontrol, i.e. The United States of America, South
Africa, Canada, Australia, and New Zealand (McFadyen and Wilson, 1997).
Australia was the most active country in developing and applying weed biocontrol.
Julien dan White (1997) report that there were 174 biocontrol projects by CSIRO
Australia with 101 weed species targets with a total of 178 different species as
biocontrol agents. Out of the 174 projects about 34% was successfull, out of the
101 weed targets about 48% was successfully controlled, and out of the 178
biocontrol agents 34% was considered effective. Some of the successfull biocontrol
was the control of cactus Opuntia sp. using the larva of moth Cactoblastis
cactorum; the control of kiyambang (Salvinia molesta) using beetle Cyrtobagous
salviniae; the control of Kirinyuh (Chromolaena odorata) using caterpillar
Pareuchaetes pseudoinsulata; and the control of Alternanthera philoxeroides using
beetle Agasicles hygrophila.
The release of biocontrol agents in Indonesia had been conducted for several
important weeds in agricultural lands. Some of them were imported from
Australia, among which are caterpillar Parauchaetes pseudoinsulata to control
Kirinyuh (Chromolaena odorata), beetle Neochetina bruchi and Neochetina
eichorniae to control eceng gondok (Eichornia crassipes), beetle Cyrtobagous
salviniae to control kiyambang (Salvinia molesta), and stem borer Carmenta
mimosa to control putri malu (Mimosa pigra).

Abdul Kadir Salam and Nanik Sriyani – 2019