Maize yield losses attributed to the stemborer; Chilo partellus (swinhoe) (lepidoptera: crambidae), in the Eastern agro-ecological Zone of Tanzania
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Date
2005
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Sokoine University of Agriculture
Abstract
Lepidopteran stem borers are generally considered the major biotic constraint to
increased maize production in Tanzania and elsewhere in Africa. The exotic stem
borer, C. partellus, is by far the most important species causing serious damage to
maize and sorghum in the eastern zone of Tanzania. The effect of four nitrogen rates
(0, 50, 75 and 100 kg Nha'1) on stem borer damage, growth and yield loss of maize
was assessed in two seasons in two locations Kibaha and Morogoro. The results
show that nitrogen had a positive effect on growth variables, mainly stem diameter,
plant height and yield, and negative effect on stem borer damage and stem tunneling.
At Kibaha the percentage yield loss due to natural stem borer infestation decreased
with increasing nitrogen application from 52.75 % to 19.38 % in the 0 kg Nha‘’and
100 kg Nha’’rates, respectively. There was no stem borer infestation at Morogoro
during the first season. During the second season, yield loss decreased from 27.09 %
in the 0 kg Nha’1 to 14.84 % in the 100 kg Nha’1 rates at Kibaha, and from 13.19 %
to 0.40 % in 0, and 100 kg Nha rates, respectively, at Morogoro. During the second
season of 2003, maize fields were surveyed at the vegetative growth phase to asses
stem borers abundance and distribution and at harvest for stem borer damage and
yield loss. At vegetative stage, C. partellus was the dominant stem borer accounting .
for 98.58 %, while S. calamistis accounted for 1.42 % of the population. During
harvesting time, there were more S. calamistis (64 %) than C. partellus (36 %).
Results from on-farm surveys showed that stem borer tunneling rec'-jced grain yield
of infested plants by 10.14 %. A 16.63 % yield loss was found in plants with more
than 15 cm tunnels. Stem diameter, plant height, and stem tunneling were found to be
the key variables affecting maize grain yield.
Description
Dissertation
Keywords
Chilo partellus (swinhoe), Agro-ecological Zone, Tanzania, Lepidopteran stem borers