Delimiting Surveys
Findings from this survey showed an expansion of invasion boundary from
the initial point of infestation in the Mwea rice scheme, with 80% of
the scheme being infested with GAS. The survey did not find any adults
or eggs in Ahero, Bura, Hola and West Kano rice schemes and its out
growers in Kisumu and Tana River Counties.
The average number of adults/m2 and egg masses was 8.4
and 7.7, respectively. Out growers, Kiamanyeki and Ndekia sections in
the Mwea irrigation scheme recorded the highest average number of adults
(Figure 3). Table 2 shows the average number of
adults/m2 and egg masses recorded within each block
and section. Time had an impact on the density of adult GAS recorded
with sections sampled in the morning recording significantly higher
adult densities compared to those sampled in the afternoon (data not
shown). There were no adult or egg masses recorded in Karaba section.
Results showed that there was a statistically significant difference in
the number of adults/m2 and egg masses among the
sections; X2(7) = 138.69, p< 0.001 and
X2(7) = 114.17, p< 0.001, respectively. The
pairwise post-hoc Dunn’s test with Bonferroni adjustments showed
significant differences in the number of adults/m2 and
egg masses between sections (Tables 3 & 4). While rice was the main
economic host attacked there were no observed varietal differences in
the infestation and damage by GAS.