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COCONUT MOTH Levuana irridescens
Bethune-Baker -- Lepidoptera, Zygaenidae (Contacts) ----- CLICK on Photo to enlarge &
search for Subject Matter with Ctrl/F. GO TO ALL: Bio-Control Cases This small purple
moth became a serious pest in Fiji in 1924, where the entire copra industry
was threatened with disaster and the Government of Fiji ordered a prize of
5,000 pounds to anyone who could devise a solution to the problem (DeBach
1974). However, the offer was
withdrawn when it was considered that the only practical solution to the
problem was a biological one, requiring trained entomologists. Working cooperatively with H. W. Simmonds,
the Government Entomologist, Dr. J. D. Tothill, R. W. Paine and T. H. C.
Taylor were hired to initiate the biological control attack.
Coconuts were the chief income of the native Fijians and enabled
islands to be inhabited and prosper that otherwise would be uninhabited. Historically the coconut moth was
restricted to the large island of Viti Levu where it was considered native. Because of the damage, coconuts were never
considered a commercial crop there.
The threat developed as the moth spread to other islands causing
defoliation and crop failure. The
coconuts on islands attacked by L.
irridescens turned from the
normal fringe of shining green fronds to a band of lifeless grey. At the close of an outbreak not a single
green palm was to be found.
Because the coconut moth was originally known only from Viti Levu and
there it had no parasitoids of consequence, it was suspected that it might be
exotic. However, careful searches
throughout the south Pacific islands and southeast Asia, coconut moth was
never found outside of Fiji. However,
a related moth, Artona
catoxantha, had been
known for some time to occur in Java and Malaya and to be heavily
parasitized. In 1924 attempts were
made through cooperating entomologists to obtain parasitoids from A. catoxantha.
Several species were collected in abundance in Java and twice sent by
ships' cold storage to Fiji, but as the voyage was prolonged by routes
through Australia (4,000 miles), and took one month, the parasitoids failed
to survive.
At the time biological control was still in its infancy and no single
approach was considered. It was, for
example, decided to import a series of generalist parasitoids of non related
hosts from Hawaii in the hope that they might attack coconut moth. There were attempts to increase predation
with an ant, Oecophylla
smaragdina, which was
used in the Orient to control pests on citrus. Even insectivorous birds were considered for importation from
Sri Lanka and India, etc. These
approaches either failed or were finally rejected as impractical, undesirable
or unfeasible. The parasitoids of A. catoxantha were again considered for introduction, even
though success was thought to be improbable due to the necessity of
transferring from Artona to Levuana. Often host specificity prevents such
transfers; but, as was learned from studies of moths in Canadian forests, in
certain cases the same parasitoids could attack distinctly different host
species.
Drs. Taylor, Tothill and Paine conducted additional explorations in
Melanesia and Indonesia in 1925, and nine species related to Levuana were found, most of them
being quire rare and heavily parasitized.
When Taylor returned to Fiji with a shipment of parasitoids, all had
died. Because of the rarity of most
species, and the fact that Artona
catoxantha was more readily
available in Java and other parts of Indonesia and was known to have at least
two active parasitoids, Ptychomyia and Apanteles,
it was decided to concentrate on their importation. While H. W. Simmonds was in Kuala Lumpur early in 1925 to seek
out a Artona outbreak,
Taylor was travelling in Malaysia when he located a small outbreak of Artona about 300 miles from
Singapore at Batu Gajah. Both species
of parasitoids were present. Simmonds
joined him there to prepare as large a shipment as possible for Fiji, which was
gathered into 17 large Wardian-type ventilated cages, each of which would
hold 4-5 small coconut seedlings infested with both parasitized and
unparasitized Artona
larvae. The latter were to serve as
hosts for egg-laying parasitoids that emerged en route. About 20,000 larvae were placed on the 85
young palms and sent 300 miles to Singapore by rail.
There were great difficulties encountered in getting shipments through
alive. It had been decided that
direct shipment from Singapore to Fiji was required in order to avoid
Australian quarantines. However,
there were virtually no direct sailings so that most shipments went by
Australia anyway. Also the
collections and shipments had to be made when the insects were available, but
this had to coincide with the avai8lability of a ship which often was months
apart. About the only hope was the
Clan Line of cargo boats which sailed between London and Fiji, sometimes via
Singapore. In June it was learned by
cable that the Clan Mackay would sail from
Singapore on July 10 for Fiji but not directly. Meanwhile it was learned, again by cable, that Clan Matheson was sailing from Java directly to Suva, Fiji, on
July 10, so for an extra 250 pounds sterling the Clan Mackay
was instructed to call at Surabaya, Java, to transfer the parasitoids to the Clan Matheson which would be ready to sail (DeBach 1974). This saved several days although it still
took 25 days following collection to reach Suva. Taylor accompanied this shipment to supervise and care for it
en route, arriving in Suva on Aug 3, 1925, when he immediately conveyed the
cages to a quarantine insectary.
About 315 live adult parasitic flies of Ptychomyia but no Apanteles
survived. The tachinid flies were
transferred to cages stocked with Levuana
larvae and immediately attacked them.
By August 21 the first generation of new adult flies began to emerge
and insectary culture was assured.
Within six months over 15,000 flies had been bred and colonized over
the coconut moth infested area. The
potential of the fly was first realized when just two months after the
importation, parasitoids were found to be accidentally established around the
insectary. From this time in October
onward, the dispersal of the fly was very rapid and it was found to be established
throughout all host infested zones within six months of the first liberation.
Within three months of liberation of the Suva colony, Levuana was exterminated on the
original release trees. Six months
after the initial introduction of Ptychomyia,
many of the outbreaks had subsided completely. When the final report was written in 1929, there had been no
new outbreak of Levuana for three years.
DeBach (1974) noted that it seemed especially significant that this
single natural enemy, P. remota, apparently gave better
control of its adopted host L.
irridescens than it did of
its native host Artona
(Tothill et al. 1930) (also see Gater 1925, 1926a,b, 1928; Simmonds 1930, van
der Vecht 1950, O'Connor 1953, and Clausen 1978). REFERENCES: [Additional references may be found at: MELVYL
Library ] Clausen, C.
P. 1978. Zygaenidae. In: C. P. Clausen (ed.), Introduced Parasites
and Predators of Arthropod Pests and Weeds.
U. S. Dept. Agric., Agric. Handbk. No. 480.
545 p. DeBach,
P. 1974. Biological Control
by Natural Enemies. Cambridge
University Press, London, New York.
323 p. Gater, B. A. R. 1925. Some observations
on the Malaysian coconut zygaenid (Artona
catoxantha Hamps.). Malayan Agric. J. 13: 92-115. Gater, B. A. R. 1926a. Further
observations aon the Malaysian coconut zygaenid (Artona catoxantha
Hamps.) and its parasites. Malayan
Agric. J. 14: 304-50. Gater, B. A. R. 1926b. Further
observations on the Malaysian coconut zygaenid (Artona catoxantha
Hamps.) and its parasites. Malayan
Agric. J. 14: 304-50. Gater, B. A. R. 1928. The Malayan
coconut zygaenid (Artona catoxantha Hamps.) and its
relation to Levuana iridfescens B. baker, in
Fiji. 3d Pan-Pacific Sci. Cong. Proc.
2: 2082-85. O'Connor, B. A. 1953. Biological
control of insects and plants in Fiji.
7th Pacific Sci. Cong. Proc. (1949) 4: 278-93. Simmonds, H. W. 1930. Problems in
biological control. The gap in the
sequence of generations in Artona
catoxantha, the coconut leaf
moth of Malaya. Trop Agric.
(Trinidad) 7: 215-19. Tothill, J. D., T. H. C. Taylor & R. W.
Paine. 1930. The coconut moth in Fiji. A history of its control by means of
parasites. Publ. Imp. Bur. Ent.,
London. 296 p. van der Vecht,
J. 1950. The coconut leaf
moth (Artona catoxantha Hamps.). Pt. I. Life history and habits of Artona catoxantha, its parasites and hyperparasites. Min. Agric. Gen. Agric. Res. Sta.,
Bogor, Contrib. 110: 1-77. |