ROLE OF SOME ECOLOGICAL FACTORS FOR AN ALTITUDINAL EXPANSION OF SPOTTED STEMBORER, CHILO PAR TELL US (SWINHOE) (LEPIDOPTERA: CRAMBIDAE)

Abstract

Survey was carried out during 2004 main cropping season to investigate the abundance
and distribution of stemborers, with emphasis on spotted stemborer, Chilo partellus (Swinhoe) in central
and eastern Ethiopia. The survey sites were mapped using Arc View GIS software. Three species of
stemborers, namely, C. partellus, maize stemborer, Busseola fusca (Fuller) and pink stemborer, Sesamia
calamistis (Hampson) were recorded. Chilo pmctellus was recorded as a dominant and widely distributed
species in 96% of the surveyed sites. On the other hand, B. fusca was mainly recorded in highland areas,
while S. calamistis was found at all elevations in small number. The current survey revealed the
expansion of C. partellus to high-elevated areas as high as 2088 meters above sea level (masl), where it
was not recorded earlier in the country. Observations were also made during the survey on the effect of
cropping system, wild host and weediness on stemborer infestation, species composition and density.
Analysis of variance and independent T test showed higher level of infestation on monocrops and on
fields with wild hosts than intercrop and wild host free fields. The results also proved the existence of
significant variation in the level of infestation between crop types. Chi square test revealed strong
relationship between cropping systems, crop type, presence or absence of wild host and species
composition at intermediate and highlands. Borer density was the highest at low altitude as compared
to intermediate and high altitude