| dc.description.abstract | Plant parasitic nematodes associated with sugarcane are known to cause losses in yields of up to
50% thus ranking among the most damaging pests. However, their occurrence, abundance and
distribution in western Kenya sugarcane zones is not known. Therefore, this study was
conducted to determine occurrence of the nematodes, the host resistance status of the varieties
used and the influence of different intercrops on the population dynamics of the parasites. The
survey and field trials were carried out in the western sugarcane zones of Nzoia, Mumias, West
Kenya and Busia while the greenhouse experiment was conducted at Kabete field station.
Samples were collected from farms in the four zones and nematodes extracted from 200 crn' soil.
Nematodes were identified up to the genus level and then counted.
Seven sugarcane varieties were selected for evaluation to determine their host resistance status
to nematodes. These were C0421, C0617, C0945, EAK70-97, KEN83-737, KEN82-808 and
KEN82-216. N14 was used as the standard due to its known tolerance status. The experiment
was carried out in a glasshouse at Kabete in a completely randomized design with three
replications. Data on nematode populations and shoot length were collected at 0, 60 and 120
days after planting (DAP). At termination, data on root length and weight were taken and
subjected to Analysis of Variance and means separated by Least Significant Difference test. The
field trial to evaluate the effect of different intercrops on plant parasitic nematodes associated
with sugarcane was carried out at Kibos, Kisumu in western Kenya. Five food crops namely
bean, soya bean, pigeon pea, maize, and cowpea. The experiment was laid down in split-plot
designwith variety as the main plot.
The dominant genera of nematodes associated with sugarcane were Pratylenchus, Scutellonema
and Meloidogyne with percentage densities of 21, 18 and 13 respectively. Soils in Nzoia were
more heavily infested with plant parasitic nematodes given that 55% of the nematodes were
recovered from the zone compared to 45% in all the other zones combined. Sandy soils haboured
40% more nematodes compared to clay soils. The varieties tested showed a higher level of
resistance to plant parasitic nematodes compared to N14. Crop cycle, altitude, AEZ, management
types and organic products were found to influence the parasites. Most nematodes are
concentrated in Nzoia sugarcane scheme which is a marginal sugarcane zone as opposed to
Mumias which is a typical sugarcane zone (LM1).
The highest density of nematodes in the rhizospheres of all varieties screened were those of
Pratylenchus spp. at 188 per 200cm3 of soil while the least were Hoplolaimus spp. at 92.
Numbers of plant parasitic nematodes were 81% lower when variety C0421 was interplanted
with beans compared to variety N14 with beans. Significant differences were also observed when
different sugarcane varieties were interplanted with soya beans. Intercropping resulted in
reduction of numbers of plant parasitic nematodes with the exception of members of the genus
Scutellonema whose numbers increased in sugarcane interplanted with common bean.
This study has established the presence of 15 genera of plant parasitic nematodes associated
with sugarcane in the western zones of Nzoia, Mumias, West Kenya and Busia with
Pratylenchus, Scutellonema and Meloidogyne being the most predominant. It has also revealed
the influence of soil texture, crop cycle and anthropogenic factors on abundance and distribution
of these nematodes in western Kenya sugarcane zones. It has therefore set the justification of
further work to determine the economic importance of the nematodes to sugarcane production. | en |
