Behaviour and biology ofChilo partelluson maize landraces

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 volatiles that attract parasitoids, but little is known on the effect of these volatiles on subsequent herbivore 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, feeding, 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 preference 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. Similarly, 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.

More Than “Push” and “Pull”? Plant-Soil Feedbacks of Maize Companion Cropping Increase Chemical Plant Defenses Against Herbivores

“…moth oviposition (Mutyambai et al, 2014(Mutyambai et al, , 2015 or through the attraction of natural enemies (Khan et al, 1997;Tamiru et al, 2011;Mutyambai et al, 2015). In our study, however, no statistically significant difference was detected in the moth oviposition between maize plants grown in soil from push-pull and non-push-pull fields.…”

“…While this could be attributed to limited sample size, this result could also be an indication for two biological phenomena at play. First, in previous studies herbivore-or oviposition-induced VOC emissions had been found as factors driving oviposition choices of C. partellus adults (Mutyambai et al, 2014(Mutyambai et al, , 2015. The VOC emissions induced by push-pull soil may include some of the same compounds but as a bouquet may not contain the same information for the female moths as herbivore-induced VOCs.…”

Responses of stemborer Chilo partellus to volatiles emitted by maize landraces exposed to signal grass (Brachiaria brizantha)

“…The larva of C. partellus is the damaging stage which makes tunnels into maize leaves, tassels and stems causing yield loss of up to 80% and therefore threatens food security (Kfir et al 2002;Khan et al 2007Khan et al , 2010. Chilo partellus has also been reported to cause damage on other crops such as sorghum, sugar cane, forage crops and wild grasses (Harris 1990;Khan et al 1997;Mutyambai et al 2015a).…”

An Indirect Defence Trait Mediated through Egg-Induced Maize Volatiles from Neighbouring Plants

“…In particular, plants respond to herbivore attack through production of a number of chemical signals known as herbivore-induce plant volatiles (HIPVs), which have direct and/or indirect effects on the attacking herbivore. Directly, these chemical cues negatively affect the physiology or behaviour of the herbivore, either as toxins, digestibility reducers or deterrents [ 6 , 7 ]. Indirectly, plants use these HIPVs to attract natural enemies of the herbivores, as well as increase the foraging success of these natural enemies, thereby facilitating improved control of herbivores [ 8 , 9 ].…”