Abstract:
Plants defend themselves against herbivores through activation of both constitutive and induced
defences. Previous studies reported that egg deposition on maize landraces induces the release of vol-
atiles that attract parasitoids, but little is known on the effect of these volatiles on subsequent herbi-
vore oviposition. In addition, larval preference and development on these maize landraces is
unknown. We evaluated six landraces and one hybrid maize variety for their resistance to
Chilo
partellus
(Swinhoe) (Lepidoptera: Crambidae). Larval orientation, settling, arrest and dispersal, feed-
ing, development, survival, and subsequent oviposition of moths were determined for individuals
reared on each of these varieties under laboratory and screen house conditions. For oviposition pref-
erence studies, all treatments were initially exposed to egg deposition whereas the control treatments
were not. Larval preference was generally higher for hybrid maize, compared to the landraces. Simi-
larly, first-instar feeding on maize leaves was more intense in hybrid maize than in four of the six
landraces. The amount of food consumed and assimilated by third instars over a 24-h period was,
however, not different among the maize varieties. Larval survival was significantly lower in maize
landraces (32%) compared to hybrid maize (54%). However, there was no difference in the larval
development period between any of the treatments. Two-choice oviposition assays showed that
moths preferred non-exposed maize landraces for subsequent oviposition, whereas in the hybrid,
there was no difference in oviposition preference between exposed and non-exposed plants.
Although the mechanism of larval suppression was beyond the scope of this study, it was inferred that
the landraces showed some resistance to
C. partellus
feeding and that initial egg deposition on these
landraces deters further colonisation by the herbivore.