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Sri Lanka has felt the impact of invasive alien animals and plants affecting
agriculture over several decades.
The introduction of water hyacinth (1905), Salvinia (1939) and Parthenium
(1999) are some invasive alien plants that have affected our water bodies
and land. Steps are being taken to overcome the threat from these species
by even using biological control methods, said Senior Professor, Weed
Science, Department of Crop Science, Faculty of Agriculture, University of
Peradeniya and President, Weed Science Society of Sri Lanka, Prof. Buddhi
Marambe.
However, he said the battle to get rid of the menace continues despite the
challenge to completely eradicate the threat to crops.
The Fall Army Worm (FAW; SenaDalambuwa; scientific name:
Spodopterafrugiperda) hit the headlines of news reports and took the country
by surprise in late 2018. Early warnings reached Sri Lanka from India since
mid-2018 regarding the potential invasion of this pest.
However, the insect landed in the country later, mainly affecting the maize
crop. Crop losses were calculated to be in the range of 5-25 percent
depending on the location.
The Department of Agriculture, Faculties of the Agriculture of universities,
Provincial Department of Agriculture, private sector and the farming
community joined forces to control the spread of the alien pest, mainly by
using pesticides to bring down the population densities. The drop of pest
population densities will always help any natural enemy and other potential
techniques to take over the control in the long run. “We succeeded in these
efforts to a great extent,” Prof. Marambe said. A team of scientists led by
Drs. Suranga Kodithuwakku and Dimanthi Jayatillake of the Faculty of
Agriculture at the University of Peradeniya supported the Department of
Agriculture (DOA) by using molecular techniques to identify the insect
accurately.Scientists from the Plant Protection Service (PPS) of the DOA and
elsewhere confirmed the life cycle of the pests and identified the sensitive
growth stages of the pest (early instars of the caterpillar) to impose control
measures effectively.These efforts immensely supported the DOA, other
agencies and farming community to effectively embark on control programs.
Despite these, after about 18 months, we now hear again of the resurgence
of the pest during the Yala season 2020, especially from the Badulla area.
All scientists knew that the FAW has come to stay. In a previous interview
with the Sunday Observer in 2019, the author of this article clearly stated the
same. This has been the case in almost all countries the pest has invaded.
The message was for everyone to be vigilant, monitor the situation, and not
to be complacent that the pest has vanished after the initial success of its
control. Resurgence of such invasive pests need immediate and site-specific
treatment to bring down their population. Careful selection and effective use
of pesticides will support the exercise during the early stages. If the observed
population density is low, manual collection of the caterpillars and destroying
them would help reduce economic losses. Revival of invasive alien pests can
take place due to many reasons. On a global scale, changes in the climate
are considered as one the major causes for pest resurgence. Loss of natural
enemies in an ecosystem is also a favourable situation for an insect-pest to
re-emerge.
However, FAW is an alien, and considering its patterns of invasion, it is less
likely that we have strong natural enemies to reduce the number of pests.
Scientists are still not certain what made the pest re-appear in higher
densities in certain parts of the country. Destroying the pest alone will not
help, but there is a need to understand what alternate hosts (e.g. weeds) the
insect-pest would use to survive in the environment.
- 122 -
agriculture over several decades.
The introduction of water hyacinth (1905), Salvinia (1939) and Parthenium
(1999) are some invasive alien plants that have affected our water bodies
and land. Steps are being taken to overcome the threat from these species
by even using biological control methods, said Senior Professor, Weed
Science, Department of Crop Science, Faculty of Agriculture, University of
Peradeniya and President, Weed Science Society of Sri Lanka, Prof. Buddhi
Marambe.
However, he said the battle to get rid of the menace continues despite the
challenge to completely eradicate the threat to crops.
The Fall Army Worm (FAW; SenaDalambuwa; scientific name:
Spodopterafrugiperda) hit the headlines of news reports and took the country
by surprise in late 2018. Early warnings reached Sri Lanka from India since
mid-2018 regarding the potential invasion of this pest.
However, the insect landed in the country later, mainly affecting the maize
crop. Crop losses were calculated to be in the range of 5-25 percent
depending on the location.
The Department of Agriculture, Faculties of the Agriculture of universities,
Provincial Department of Agriculture, private sector and the farming
community joined forces to control the spread of the alien pest, mainly by
using pesticides to bring down the population densities. The drop of pest
population densities will always help any natural enemy and other potential
techniques to take over the control in the long run. “We succeeded in these
efforts to a great extent,” Prof. Marambe said. A team of scientists led by
Drs. Suranga Kodithuwakku and Dimanthi Jayatillake of the Faculty of
Agriculture at the University of Peradeniya supported the Department of
Agriculture (DOA) by using molecular techniques to identify the insect
accurately.Scientists from the Plant Protection Service (PPS) of the DOA and
elsewhere confirmed the life cycle of the pests and identified the sensitive
growth stages of the pest (early instars of the caterpillar) to impose control
measures effectively.These efforts immensely supported the DOA, other
agencies and farming community to effectively embark on control programs.
Despite these, after about 18 months, we now hear again of the resurgence
of the pest during the Yala season 2020, especially from the Badulla area.
All scientists knew that the FAW has come to stay. In a previous interview
with the Sunday Observer in 2019, the author of this article clearly stated the
same. This has been the case in almost all countries the pest has invaded.
The message was for everyone to be vigilant, monitor the situation, and not
to be complacent that the pest has vanished after the initial success of its
control. Resurgence of such invasive pests need immediate and site-specific
treatment to bring down their population. Careful selection and effective use
of pesticides will support the exercise during the early stages. If the observed
population density is low, manual collection of the caterpillars and destroying
them would help reduce economic losses. Revival of invasive alien pests can
take place due to many reasons. On a global scale, changes in the climate
are considered as one the major causes for pest resurgence. Loss of natural
enemies in an ecosystem is also a favourable situation for an insect-pest to
re-emerge.
However, FAW is an alien, and considering its patterns of invasion, it is less
likely that we have strong natural enemies to reduce the number of pests.
Scientists are still not certain what made the pest re-appear in higher
densities in certain parts of the country. Destroying the pest alone will not
help, but there is a need to understand what alternate hosts (e.g. weeds) the
insect-pest would use to survive in the environment.
- 122 -
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