| dc.description.abstract | The occurrence and infestation of plant-parasitic
nematodes on tobacco, Nicotiana tabacum L., in
Busia and Bungoma districts of Kenya was investigated.
during 1983. Samples of tobacco roots and soil from
238 different sites were examined. The nematodes were
extracted by the Baermann's pan and filter method, and
then, identified to genus, except for rootknot nematode,
Meloidogyne Goeldi, which was identified to species
level.
The response of tobacco varieties; air-cured "Burley 181';;
fire-cured "Heavy Western" and flue-cured "Speight G28",
to increasing infestation levels of rootknot nematodes,
were determined in 60 different plots of either small-holder
farmers or the tobacco company, B.A.T. (Kenya) Limited.
Similar studies were also done on potted plants under
glasshouse.
(
Some seven genera of plant-parasi tic nematodes were
commonly found associated with tobaeco roots. They
were; rootknot nematode, Meloidogyne spp., root lesion
nematode, Pratylenchus spp., stubby root nematode,
Tylenchorhynchus spp., spiral nematodes; Scutellonema spp.,
Helicotylenchus spp. and Rotylenchus spp., and sheath
nematode, Hemicycliophora spp. The rootknot nematode
caused conspicous galls 01:'1 tobacco roots, and severa]Y
infected plants were considerably stunted in
growth. The nematode was found to be present in
all the sites sampled, and it contributed upto
about 85% of the total population count of parasitic
nematodes within and around tobacco roots at
postharvest sampling. The specie Meloidogyne
j avanica (Treub. ) Chitwood was predorminant wi th an
incidence of 85%. ~.incognita (Kofoid and White)
Chitwood made up the remaining 15%.
On field plots where the preplant infestation
levels of rootknot nematodes ranged from 5.9 to 10.2
larvae per 100 g of soil, the tobacco plants on
sandy or gravel soils were more severely galled and
stunted, relative to those on clay soils. Nematicide
trials with phenamiphos at 10 Kg, a.i., per ha, on
paired plots of tobacco always gave significantly
(P = 0.05) better plant growth on sandy soils but not
always on clay soils. Inspite of considerable galling
of roots, the nematodes apparently caused relatively
less reduction of growth and yields of tobacco plants
in clay soils. Similar results occurred on potted
pIants as well.
Tobacco variety "Speight G28" was more tolerant to
i~fection by rootknot nematodes at increasing
infest ation levels, relati ve to varieties "Burley 181"
and "Heavy Western". The latter two were usually
equally galled and stunted at similar inoculum levels. | en |
