Disturbance of the rainforest has the potential to enhance egg parasitism of lepidopteran noctuid stemborers in Kisangani, DR Congo

Landscape   context   influences   population   dynamics   of insects and  impacts  biological processes within  commu- nities.  It was  expected  that  anthropogenic disturbances of the rainforest landscape  in DR Congo would lead to a decreased level of noctuid  stemborer  egg parasitism  as a consequence   of  a  decoupling  between stemborers   and their  naturally occurring  parasitoids  through dispersal. To   test   this  hypothesis,    noctuid    egg   batches   were collected in maize fields along  an anthropogenic distur- bance  gradient   to  assess  change   in  the  rates  of  eggs parasitism  and  maize plant  infestation  with  noctuid  egg batches.  Our  results  showed that,  in  contrast   to  what was  initially  expected,  egg  parasitism   increased   from less to highly  disturbed  landscape  whereas  maize infestation   had   an   inverse  tendency.  Discovery  effi- ciency and  mean  egg parasitism  were 1.416 and  1.392 times higher, respectively, in the most than in the less disturbed   landscape.   The   numbers  of  eggs and   egg batches   per  100   maize  plants   were  0.55   times  and 0.532 times  the value  in  the  less disturbed  landscape, suggesting    a   dilution    of  the    stemborer  population within   a  large  habitat   patch   encompassing   cultivated fields and   the   surrounding  wild  host   plants.   It  was concluded   that   the  presence  of suitable  host   plants enhances  noctuid  stemborers  egg parasitism  in adjacent maize fields.

Auteurs: Onésime M. Kankonda, Benjamin D. Akaibe, Boaz Musyoka, Yaovi A. Bruce and

Bruno-Pierre  Le Ru