Study on the Biology and Some Ecological Aspects of Chilo Partellus (Swinhoe) (Lepidoptera: Crambidae) in Relation to its Altitudinal Expansion
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Date
2005-06
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Addis Ababa University
Abstract
Swvey was carried out during 2004 main cropping season to investigate the abundance
and distribution of stemborers, with emphasis on C. partellus in central and eastern
Ethiopia. Three species of stemborers, Chilo partellus (Swinhoe), Busseola fusca (Fuller)
and Sesatnia calamistis (Hampson) were recorded. C. partellus was dominant and widely
distributed species recorded in 96 % of the swveyed sites. On the other hand, B. fusca
was mainly recorded in highland areas while S. calamistis found at all elevations but
in small number. Though studies were not conducted so far on the increasing importance
of C. partellus, the current survey revealed the expansion of the pest to high elevated
areas as high as 2088 niasl, where it was not recorded earlier in the country.
Obseivations were also made during the survey on the effect of cropping system, wild
host and weediness on percent infestation, stemborer composition and density. The result
showed higher level of infestation on monocrops and on fields with wild hosts than
intercrop and wild host free fields. Significant variation in level of infestation between
crop types was observed. Chi square test revealed strong relationship between cropping
systems, crop type, presence or absence of wild host and species composition at
intermediate and highland. Borer density was highest at low altitude as compared to
intermediate and high altitude.
Laboratoiy study was conducted to obseive the combined effect of relative humidity and
temperature on the biological features of C. partellus. Temperature levels tested were
22°C, 26°C and 30°C while the relative humidity were 40 %, 60 %, and 80 %. The result
obtained showed variation on potential and realized fecundity, the developmental time of
immatures, and adult longevity due to differences in temperature levels, relative humidity
and their interaction. Mean duration of C. partellus life cycle was 70.2 days at 22°C and
80 % relative humidity whereas it took only 26.5 days to complete its life cycle at 30 °C
and 40 % relative humidity. Average life span adult C. partellus ranged 6.9-11.1 days at
22 °C and 2.3 - 7.2 days at 30 °Cfor the different levels of relative humidity tested.
Although developmental period of immmatures and adult longevity was longest at lowest
temperature level, C. partellus successfully completed its life cycle suggesting reason for
its expansion to high elevated areas.
Key words: Chilo partellus, infestation, species composition, interactive effect,
developmental time, longevity, fecundity
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Keywords
Chilo Partellus, Infestation, Species Composition, Interactive Effect, Developmental Time, Longevity, Fecundity