Abstract:

The study was conducted in 2012 and 2013 in Kiryandongo district, western Uganda in Bweyale
and Diika sub counties. Study sites were selected basing on cropping system and proximity to a
grassland with wild grass species within a radius of 500m away from the maize field. A total of 28
maize fields were used in 2012, fourteen maize fields from each Sub county, 7 under monocrop
system and 7 under intercrop system. In the first season of 2013 (2013A), 36 maize fields were
used 1 8 maize fields per sub county, 9 under monocrop system and 9 under intercrop system. Each
selected field was sampled twice at vegetative stage, once at tasselling stage and once at
physiological maturity in each cropping season. The study revealed that Chilo partellus was the
most dominant species, accounting for over 75% of the total borer species collected, followed by
Busseoia fusca. With regard to parasitoids. Cotesia flavipes was the most abundant in the area with
Cotesia sesamea occurring in very low numbers and was considered negligible. Intercropping
maize with non-host crops reduced Chilo partellus larval infestation and supported higher Cotesia
flavipes parasitoids numbers compared to the monocropped fields. The highest mean stemborer
incidence was recorded in the vegetative growth stage of maize.
The survey showed I2grass species surrounding maize fields; llyperrhenia tufa. Pennisetum
purpureum. Pennisetum polystachion, RottoboHa cochiliensis, Thameda triandra, Panicum
Cynodon dactyl on. Eleusine coronaca, Sorghum vesicolar, Cyperus scar iosus.
Saccharum offtcinarum and Heteropogon contortus as important hosts/refugia for stemborers and
their parasitoids albeit to varying levels. Chilo partellus preferred maize and Pennisetum, whereas
Busseoia fusca was most abundant on maize and Saccharum offtcinarum. Cotesia flavipes was
most abundant on borers found on Saccharum offtcinarum.
This study showed that cropping system influenced occurrence of the major stem borers and the
larval parasitoid on maize with monocrops consistently having higher occurrence of both Chilo
partellus and Busseoia fusca and lower counts of C. flavipes. On the other hand maize intercrop
system consistently increased C. flavipes and reduced stem borer occurrence on maize as well as
yield. Secondly, there were variable levels of occurrence of maize stem borers and C. flavipes
parasitoid on maize and grasses. Nevertheless, maize was the most favoured hosts of both Chilo
partellus and Busseoia fusca.