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.