Impact of Vairimorpha sp (Microsporidia : Burnellidae) on Trichogramma chilonis (Hymenoptera, Trichogrammalidae), a hymenopteran parasitoid of the cabbage moth, Plutella xylostella (Lepidoptera, Yponomeutidae)
M. Schuld et al., Impact of Vairimorpha sp (Microsporidia : Burnellidae) on Trichogramma chilonis (Hymenoptera, Trichogrammalidae), a hymenopteran parasitoid of the cabbage moth, Plutella xylostella (Lepidoptera, Yponomeutidae), J INVER PAT, 74(2), 1999, pp. 120-126
A multi-generation mass breeding colony of the cabbage moth, Plutella xylos
tella, was found to be infected with a microsporidium, Vairimorpha sp., whi
ch is passed transovarially between generations. The microsporidian infecti
on had little impact on the fitness of this lepidopteran pest. However when
Trichogramma chilonis parasitized such infected host eggs, the offspring o
f this parasitoid species suffered from severe deficiencies. Microsporidian
spores, ingested by parasitoid larvae together with the host egg nutrients
, gave rise to stages which developed in various tissues of the parasitoid,
such as the flight muscle and the nervous system. This infection resulted
in a significantly increased rate of metamorphosis failure (related to host
age) and reduced longevity and reproductive performance of the parasitoids
. There are two main consequences arising from our findings if T. chilonis
is to be used in an integrated control strategy against P. xylostella: (1)
T. chilonis must be raised on Vairimorpha-free host eggs to receive viable
and efficaceous parasitoids for release and (2) if natural populations of t
he cabbage moth in cruciferous crops are infected with Vairimorpha to a sig
nificant extent, the parasitoid must be released repeatedly within infested
crop areas. (C) 1999 Academic Press.