Biological Control of Insect Pests: Southeast Asian Prospects - EcoPort

Comments
4.15 Planococcus citri 315
P. citri is frequently only one of several pests of importance on the economic
crops that it infests and, if biological control is contemplated, it is advisable
to have its identity confirmed by a competent taxonomist. Its abundance is
increased when it is tended by ants for its honeydew and often, by the
injudicious use of insecticides (against it or accompanying pests). This is
mainly because of the adverse effects on natural enemies and sometimes
because low levels of insecticide may stimulate egg-laying. There has thus
been considerable effort, within an Integrated Pest Management framework
and with varying degrees of success, to develop biological control of each of
the important pests in a complex, for example on citrus, grape vines and in
glasshouses. This has also involved the careful selection of pesticides (if
these are still required) that have the least possible adverse effect on the
major natural enemies.
Where natural enemies already present are not adequate, the almost
universal response has been to introduce the encyrtid Leptomastix dactylopii
and the coccinellid Cryptolaemus montrouzieri (if the latter is not already
present as a result of introductions for other pests).
Both species are affected by the winter in temperate zones and survive
less well than P. citri in the Mediterranean region. Under these
circumstances, classical biological control seldom provides economic
control alone and requires augmentation of the natural enemies from time to
time.
Where P. citri is still a problem in the field in warm regions and
Cryptolaemus montrouzieri is not present, serious thought should be given
to introducing the latter. More importantly, however, if not already present
Leptomastix dactylopii (of Brazilian origin) should be of highest priority,
followed by Leptomastidea abnormis and Anagyrus pseudococci (both of
Mediterranean origin and capable of maintaining populations of low levels
under slightly cooler conditions). Under Southeast Asian and Pacific
conditions, Coccidoxenoides peregrinus (of south China or Indian origin)
deserves special attention.
If Planococcus citri proves to be of south China origin (and this
hypothesis requires confirmation) it is surprising that only two parasitoids
have been reportedÑthe encyrtid Coccidoxenoides peregrinus and the
platygasterid Allotropa citri. A thorough survey in this region might well
reveal additional valuable specific or near specific parasitoids. There are
good grounds for optimism that biological control of P. citri can be
improved in warmer regions by establishing, if missing, any one of the
foregoing natural enemies.