Biological Control of Insect Pests: Southeast Asian Prospects - EcoPort

300 Biological Control of Insect Pests: Southeast Asian Prospects
Before biological control was attempted in Queensland in 1980, six
natural enemies were recorded, the coccinellids Cryptolaemus montrouzieri,
and Harmonia octomaculata (= Coccinella arcuata) the chrysopids
Chrysopa sp. and Oligochrysa lutea (all 4 native) and the exotic encyrtids
Leptomastidea abnormis and Coccidoxenoides peregrinus. However, they
were unable to maintain infestations consistently at acceptable commercial
levels. Attack by a fungus similar to Entomophthora fumosa caused up to
58.1% mortality of 3rd instar nymphs and adults on passionfruit during wet
periods (Murray 1978, 1982; Smith et al. 1988).
The Brazilian encyrtid Leptomastix dactylopii was imported from
California and approximately 2.5 million adults released between 1980 and
1987. It established readily and became the commonest natural enemy of
P. citri throughout southeast Queensland, reducing mealybug infestations,
averaging 38% of fruit in early December, to an acceptable level of 5% or
less at harvest in April. Parasitoid numbers were lowest during winter and
spring and augmentative releases of 5 to 10 thousand parasitoids per hectare
in spring to early summer advanced parasitoid activity by 6 weeks.
When no releases were made, the parasitoid was first recorded in early
February and was present in an average of 55% of mealybug-infested fruit
by mid-March. The mealybug infestation peaked at an average of 47% in
mid-December but, by late April, only dropped to 10% and the presence of
the mealybug on 25% or more fruit from December to March usually
resulted in excessive amounts of sooty mould. C. montrouzieri was recorded
on a maximum of 5% of mealybug-infested fruit, and augmentative release
failed to increase this level. Augmentative release of L. dactylopii was found
to be at least as cheap as pesticides and far more compatible with IPM of
other citrus pests (Smith et al. 1988).
Placing sticky bands around the trunks of custard apple trees reduced the
numbers of the ant, Pheidole megacephala, and lowered, somewhat, the
numbers of P. citri. Parasitisation of P. citri by Leptomastidea abnormis was
low and unaffected by banding, but there were more predators (especially
Oligochrysa lutea, Cryptolaemus montrouzieri and Syrphus sp.).
Nevertheless, natural enemies were still unable to maintain P. citri at
acceptable levels (Murray 1982).
BERMUDA
Seven species of parasitoid and four predators were introduced between
1951 and 1955, mainly from California, but originating elsewhere:
Coccidoxenoides peregrinus from Hawaii and south China, Leptomastix
dactylopii (South American race) Leptomastidea abnormis, Pseudaphycus
perdignus, Anagyrus pseudococci, Blephyrus saccharicola and Allotropa
citri. Only C. peregrinus, L. dactylopii and L. abnormis were established