TABLE CONTENTS

Belonolaimus, Trichodorus and Longidorus. Soils in Nzoia were the most heavily infested
having 55% of total nematodes recovered from all the zones. Sandy soils haboured 40% more
nematodes compared to clay soils. Crop cycle, altitude, AEZ and organic products were also
found to influence the parasites. Greenhouse tests were conducted to determine relative host
resistance status of sugarcane varieties grown in Kenya. Seven varieties namely CO421,
CO617, CO945, EAK70-97, KEN83-737, KEN82-808 and KEN82-216 were selected for
evaluation. All the varieties tested showed a higher level of resistance to nematodes
compared to the standard, N14. A study to determine the influence of different intercrops of
sugarcane on the population dynamics of plant parasitic nematodes was undertaken. Five
food crops were selected namely bean, soybean, pigeon pea, maize, and cowpea. Nematode
numbers were 81% lower in a CO421/bean mixture compared to N14/bean. Significant
differences (P≤0.05) were also observed in different sugarcane/soybean mixtures.
Aphelenchoides and Pratylenchus species were significantly (P≤0.05) influenced by different
types of intercrop with their numbers highest in CO617 and least in KEN83-737. Overall
intercropping resulted in reduction of numbers of nematodes except Scutellonema species
whose numbers increased in sugarcane/bean mixtures.
The Effect of Cover Crops on the Biology of the Yam Nematode,
Scutellonema bradys
Claudius-Cole, A.O. (1), D.L. Coyne (2), R. Asiedu (2) & B. Fawole (1)
(1) Department of Crop Protection and Environmental Biology, University of Ibadan, Ibadan, Nigeria; (2)
International Institute of Tropical Agriculture, Oyo Road, PMB 5320, Ibadan, Nigeria. E-mail
d.coyne@cgiar.org
Management of Scutellonema bradys is important in the sustainable production of yams
(Dioscorea spp.). Cover crops that can be selected for inclusion in yam cropping systems
were screened for their antagonism of S. bradys. Two week old seedlings of Aeschynomene
histrix, Cajanus cajan, Stylosanthes guianensis, Tagetes erecta and Dioscorea rotundata
(control) were inoculated with 1000 eggs of S. bradys. The experiment was laid out in a
randomized complete block design with three replicates and 50 plants per treatment to
accommodate daily destructive sampling. Roots of plants were harvested from between 1- 42
days after inoculation and assessed for nematode penetration and development within the
roots. Exudates from roots were also collected and the in vitro effect of 1 mm stock solution
assessed against 50 eggs of S. bradys in glass blocks. Hatching and juvenile mortality were
recorded daily over a 10 day period. S. bradys juveniles were observed in yam roots and roots
of C. cajan at three days after inoculation, but not in roots of S. guianensis until the 12 th day
or in T. erecta roots until the 17 th day. Adult females produced eggs 26 days after inoculation
in yam roots, whereas no females or eggs occurred in the roots of C. cajan by the end of the
study. Juveniles observed in roots of S. guianensis and T. erecta did not emerge into adults
by the end of the study. Egg inhibition and juvenile mortality in exudates of T. erecta was
71% and 80% respectively compared to the control, while A. histrix and S. guianensis
inhibited egg hatch by 59 and 46% respectively. S. guianensis and T. erecta appear to
produce exudates that affect the penetration of juveniles into their roots and at the same time
disrupt the biology of those that penetrate. C. cajan however, permits rapid penetration of
juveniles after which their development is arrested.
5 th International Congress of Nematology, 2008 276