Biological Control of Insect Pests: Southeast Asian Prospects - EcoPort

Biology
4.9
Dysmicoccus brevipes
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In some countries (Ivory Coast, Madagascar, Dominican Republic,
Martinique, Malaysia) both sexes of D. brevipes occur (Beardsley 1965;
Lim 1973). D. neobrevipes is known from many countries in Central and
South America and probably also originated there (Williams and Watson
1988). It is known from Mexico, Jamaica, American Samoa and Samoa,
Cook Is, Kiribati and Guam. In Southeast Asia it occurs in Malaysia, the
Philippines and Thailand (where there have been recent serious outbreaks
(Beardsley 1965; Rohrback et al. 1988; Williams and Watson 1988).
D. brevipes females are broadly oval to rotund in shape, pinkish in colour,
and have a thick waxy covering with short conical waxy projections
(Kalshoven 1981). In Hawaii, D. brevipes is parthenogenetic and
ovoviviparous (i.e. it produces its young alive). About 250 crawlers are
produced per female over a 3 to 4 week period and take some 34 days to
mature. Females start producing young about 25 days after the third moult
(Ito 1938).
In peninsular Malaysia the bisexual form is widespread but the
parthenogenetic form was not found (Lim 1973). In the male, there are two
nymphal, one prepupal and one pupal instar of 10, 6, 3 and 4 days duration
respectively. Adult males live for 1 to 3 days, whereas adult females live 17
to 49 days. The female has 3 nymphal instars, lasting 10, 7 and 7 days
respectively. A female produces 19 to 137 offspring with a sex ratio of 1:1
(Lim 1973). The bisexual form in Malaysia has a 10 day shorter life cycle
than the parthenogenetic form in Hawaii and might have as many as 9
generations a year (Lim 1973). The bisexual form of D. brevipes is capable
of producing green spotting on pineapple leaves, whereas the
parthenogenetic form is not (Beardsley 1965).
In India, Ghose (1983) studied the parthenogenetic form of D. brevipes
at 30¡C and 60Ð66% R.H. The nymphs completed their development in 19
days and, after a pre-oviposition period of 16 days, produced an average of
240 young over a period of 40 days.
D. brevipes occurs mainly on the underground parts of the pineapple
stem (where the stem is covered by leaf bases) and on the roots. Leaves or
fruit are less heavily infested, except on weak plants. However the bisexual
form also infests the crown of the pineapple plant (Rohrbach et al. 1988).
By comparison, D. neobrevipes,
which is always bisexual, is found only
on the aerial parts of the pineapple plant Ñ leaves, stems, aerial roots,
flowers and fruit clusters. Unlike D. brevipes,
it does not infest grasses . In
Hawaii, only D. neobrevipes causes green spotting of pineapple leaves
(Beardsley 1959).