Biological Control of Insect Pests: Southeast Asian Prospects - EcoPort

344 Biological Control of Insect Pests: Southeast Asian Prospects
Trichogramma minutum Hym.: Trichogrammatidae
When attacking eggs of T. ni, females reared from T. ni eggs were more
fecund than those from Sitotroga cerealella and searched over larger areas
for hosts (Marston and Ertle 1973). At 27¡C and 50% RH T. minutum
populations increased more rapidly than those of T. platneri. T. minutum
does not feed from the host egg nor does it superparasitise eggs even when
hosts are in short supply (Manweiler 1986).
Trichogramma platneri Hym.: Trichogrammatidae
After ovipositing in a host egg, females pierce it again and feed from
exuding droplets of fluid. T. platneri superparasitised hosts when eggs were
scarce. At about 27¡C and 50% RH, T. platneri populations increased more
slowly than those of T. minutum (Manweiler 1986). The maximum number
of progeny bred from a single T. ni egg was 3 and 73% of male progeny
emerged from the first eggs exposed to a female. Honey was shown to
increase parasitoid longevity (Hohmann et al. 1988a, b).
Trichogramma pretiosum Hym.: Trichogrammatidae
This species can be reared from egg to adult in vitro (Hoffman et al. 1975).
Females have a preference for young T. ni eggs, although eggs of all ages are
accepted (Godin and Boivin 1994). A local Missouri, USA strain of
T. pretiosum successfully parasitised T. ni eggs in field experiments, large
host eggs producing more adults than small ones and these adults were more
fecund and active than those from small eggs (Boldt et al. 1973). A Texan
strain was effective in the laboratory against T. ni eggs, but not in the field. It
was able to develop in the same T. ni egg as Trichogramma evanescens if
eggs of both parasitoids were deposited on the same day (Parker and Pinnell
1972, 1974).
In Texas, naturally occurring T. pretiosum assisted in controlling T. ni on
cotton in field cages (Lingren et al. 1978). In southern California, average
parasitisation of T. ni eggs ranged from 3 to 47% in tomatoes when releases
were made at the rate of 200 000 to 318 000 adult wasps per 0.4 ha (Oatman
and Platner 1978). In Florida 3 releases 3 days apart of T. pretiosum at about
378 000/acre/release in a 1 acre field cage containing 7 crops resulted in
substantial parasitisation of T. ni eggs and in suppression of larvae (Martin et
al. 1976b). Laboratory and field cage studies with T. pretiosum were also
carried out in California (Ashley et al. 1974) where female parasitoids
produced from T. ni eggs were larger, more fecund and lived longer than
those from artificial rearing hosts (Plodia interpunctella and Sitotroga
cerealella) (Bai et al. 1992).