Biological Control of Insect Pests: Southeast Asian Prospects - EcoPort

4.15 Planococcus citri 299
The encyrtid Leptomastix dactylopii, introduced in 1934 from Brazil,
was mass reared and released. Recoveries were made over a number of years
following each spring or summer release, but not following the ensuing
winter. Eventually, a few managed to overwinter, resulting in a low level
population (Compere 1939).
The South China platygasterid, Allotropa citri, introduced in 1950,
attacked 1st and 2nd instar P. citri, but mass releases over some 6 years
resulted in few field recoveries and it is not thought to be established
(Bartlett 1978).
A somewhat polyphagous encyrtid, Anagyrus pseudococci, was
unsuccessfully introduced from Brazil in 1934 and 1953. The same or a
similar species, Anagyrus sp. nr pseudococci, was brought in from Italy in
1955, but was established only briefly (Bartlett 1978).
The coccinellid Exochomus metallicus from Eritrea was established
from introductions in 1954 against citricola scale (Coccus pseudomagnoliarum)
and black scales and attacks P. citri on plants other than citrus
(Bartlett 1978).
In spite of this series of introductions, the natural enemies of P. citri in
California do not, unaided, maintain populations at sub-economic levels,
mainly because, it is claimed, climatic conditions permit the overwintering
of, at best, inadequate populations. Cryptolaemus montrouzieri has often
provided spectacular control of high populations, but is unable to maintain
its numbers on low prey populations and disappears, requiring
reintroduction. Methods are available for its low cost mass production
(Fisher 1963).
The encyrtid Leptomastidea abnormis is of considerable value in
attacking young mealybugs sheltering under citrus fruit sepals in spring and
autumn, but is adversely affected by high temperatures. Both Leptomastix
dactylopii and Coccidoxenoides peregrinus build up high numbers
following mass releases, but crash over winter and require repeated mass
releases to maintain effectiveness.
AUSTRALIA
P. citri can be an important pest of citrus, but also attacks passionfruit and
custard apple in warmer regions. The earliest attempts at biological control
were in Western Australia, where Cryptolaemus montrouzieri was
introduced from New South Wales in 1902 and an unidentified coccinellid
from Spain in 1903. Only the former was established and it rapidly became
an important factor in the successful control of mealybugs there (Wilson
1960).