EUPATORIUM SHRUBBY WEED
Eupatorium odoratum L. -- Compositae
This is a neotropical shrubby weed which became established in many areas of the Old World tropics. Investigations by the West Indian Station of the Commonwealth Institute of Biological Control revealed several possibly useful host-specific phytophagous insects. One leaf-feeding arctiid, Ammalo insulata (Walker), that causes severe defoliation in Trinidad and South America seemed most promising. The larvae are nocturnal in their feeding and thus are protected from predaceous birds, etc., but they may become infected with a virus disease spread by a nocturnal tachinid parasitoid (Bennett & Cruttwell 1973). The virus is apparently foliage-borne, so by rearing material from eggs sent to India this was easily eliminated for supplying virus free material of Ammalo to those countries interested in utilizing it against Eupatorium (Simmonds 1976). The arctiid was tried out in the field in Karnataka, India; Sabah, Malaysia; Takoradi, Ghana and in Nigeria. It was also tested in Sri Lanka. In India and West Africa there was no establishment as it appears that predators (ants) quickly removed all young larvae. In one small area only in Sabah, at Papar road near Kota Kinabalu, a small population of Ammalo persisted in a restricted area on either side of a stretch of road ca. 100 m. long. Within this area a number of ovipositing moths and feeding larvae could be found at night, but damage to Eupatorium was restricted to a small area which tends to shift from time to time around the general area. In other release sites no establishment occurred. In Sri Lanka releases made at the end of 1973 were followed by considerable damage to Eupatorium that was growing in some areas under coconut palms. At most other areas where releases were made no establishment occurred. Later, a large area of ca. 1,000 ha. was defoliated and establishment seemed to have occurred on one other area.
Investigations showed that releases of Ammalo larvae results in defoliation of Eupatorium, but there is no more oviposition by Ammalo, nor does it move to a new area, and the fate of the pupae and adults resulting from the released larvae is unknown. Although it is understandable that in West Africa and in India, predators, particularly ants, are able to prevent establishment of Ammalo, the explanation of why similar elimination has not occurred in one small area of Sabah and in a much larger area of Sri Lanka, which may be deficient in the regulatory predators, is unknown.
REFERENCES: [Additional references may be found at: MELVYL Library ]
Bennett, F. D. & R. E. Cruttwell. 1973. Insects attacking Eupatorium odoratum in the neotropics. I. Ammalo insulata (Walk.) [Lep.:
Arctiidae], a potential biotic agent for the control of Eupatorium odoratum L. [Compositae]. Tech. Bull. Commonw. Inst. Biol. Contr. 16:
Simmonds, F. J. 1972. Approaches to biological control problems. Entomophaga 17: 151-.
Simmonds, F. J. 1976. Some recent puzzles in biological control. Entomophaga 21: 327-32.