Abstract:
Tomato (Solanum lycopersicum) is an economically important crop in East Africa and is
produced largely by small-scale farmers. The root-knot nematode, Meloidogyne
incognita (Kofoid and White) Chitwood, causes serious constraints in tomato
production in the African continent. Organic additives of plant origin have been known
to control nematodes. The efficacy of different formulations of these additives dispensed
as a slow-release in filter bags against M. incognita remains unknown. This study
investigated the efficacy of two formulations; powder, and pellet from leaves and stems
(above parts) and roots (below parts) of Tithonia diversifolia and Tagetes minuta on M.
incognita in tomato. The filter bags were made of non-woven interfacing fusible fabric,
and they contained the extracts used in the experiments. The experiment was laid out in
a completely randomized design with 18 treatments and replicated four times. Tomato
seedlings were inoculated with about 1500 freshly hatched second stage juveniles of M.
incognita five days after seedling transplant. Data was collected on root galling, number
of egg masses per root, root-knot nematode second-stage juveniles in the soil, and
tomato yield and subjected to analysis of variance (ANOVA). Treatment means were
compared using the Tukey Studentized Range Test at a 5% probability level (P = 0.05).
Results showed that all formulations significantly (P= ˂0.001) reduced nematode
populations relative to the untreated control. However, untagged (without filter bag)
formulations were about five times better than the tagged (with filter bag) in both the
preventive and curative trials at 42- and 84-days post-inoculation (DPI). No significant
differences were observed at 126 DPI. Powder formulations of T. minuta roots (79%)
and T. diversifolia leaves (78%) significantly (P = ˂0.001) reduced M. incognita juvenile
populations followed by pellet formulations of T. minuta leaves (74%) and T. diversifolia
roots (72%) relative to the positive control (70%) Bionematon® Powder formulations
(79%) reduced RKN populations better than the pellet formulations (73%) but the yield
was higher (70.7 t/ha) in the latter. Tagged powder formulations of T. diversifolia roots
recorded a 7% decrease in yield in the preventive trial compared to the curative trial.
However, within the same trial, tagged pellets of T. minuta roots and the positive control
recorded more than 10% increase in yield relative to the curative trial. These findings
indicate that formulations of T. minuta and T. diversifolia incorporated in filter bags can
be used for management of RKNs in tomato and other vegetable crops.
