Contents - Faperta

Transgenic Resistance to Insects: Interactions with Nontarget Organisms 355
FIGURE 11.5 The hymenopteran parasitoid, Campoletis chlorideae female laying eggs in the second-instar larva
of Helicoverpa armigera reared on Bt-intoxicated artifi cial diet/transgenic plants. Right: egg, larva, and pupa of
C. chlorideae.
(Johnson, Gould, and Kennedy, 1997). Decreased feeding by H. virescens larvae on transgenic
plants may be responsible for the observed differences in parasitism, because C.
sonorensis locates host larvae using cues from damaged plants. When mean larval survival
was used to estimate fi tness of the nonadapted insects relative to the Bt toxin-adapted
insects, it was found that C. sonorensis might delay adaptation to Bt-transgenic plants
(Johnson, Gould, and Kennedy, 1997). Bourguet et al. (2002) observed a signifi cant variation
in parasitism by the tachinids, Lydella thompsoni Herting and Pseudoperichaeta nigrolineata
Walker across locations, and greater parasitism was recorded in normal than in Bt
transgenic maize.
Cocoon formation (%)
120
100
80
60
40
20
0
Mech 12 Mech 162 Mech 184
Nontransgenic Transgenic
FIGURE 11.6 Cocoon formation of the parasitoid, Campoletis chlorideae reared on Helicoverpa armigera larvae fed
on the leaves of Bt transgenic and nontransgenic cottons.