Biological Control of Insect Pests: Southeast Asian Prospects - EcoPort

4.16 Trichoplusia ni
India
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Myanmar
++ Laos
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20°
China
+
Thailand
++
Cambodia
++
Vietnam
+
Malaysia
Singapore
Brunei
P
Indonesia
Taiwan
+
Philippines
Australia
Papua
New Guinea
317
The cabbage looper, Trichoplusia ni,
of North American origin, attacks cabbage (and other
Brassicaceae), cotton, lettuce, tomatoes and a very wide range of other cultivated crops and
wild hosts. In North America it is maintained for much of the time at sub-economic levels by a
wide range of natural enemies, but damaging outbreaks do occur, particularly when its natural
enemies are killed by insecticides applied against other pests in the same crop.
The major predators, which together cause considerable mortality, are widely polyphagous,
and hence are unlikely to be considered seriously as classical biological control agents. Several,
among its 120 or so parasitoids are somewhat more host specific and are worth serious
consideration. They include species of Trichogramma egg parasitoid; Copidosoma
truncatellum (an egg-larval parasitoid); and the larval parasitoids Hyposoter exiguae,
Microgaster brassicae and Voria ruralis.
High larval mortality is frequently produced by a valuable, naturally occurring, nuclear
polyhedral virus, particularly late in the season when T. ni populations are high and rainfall is
adequate.
There appear to be good reasons for optimism that the establishment of suitable missing
natural enemies in regions into which T. ni has spread would assist in maintaining its populations
at sub-economic levels.
20°
0°
20°