Abstract:

This study evaluated the use Metarhizium anisopliae (Metschnikoff) for integrated
management of pestiferous termites attacking Grevillea robusta trees in farm land. Aspects of
the fungus assessed were persistence; optimum application rate; spread in soil and effect on
non-target ground arthropods. Persistence was evaluated in farm sites applied with the fungus
approximately a decade earlier whereas optimum application rate; horizontal and vertical
spread in soil; and effect on non-target ground arthropods were examined within a year of
fungal application to farm sites with different cropping regimes. Optimum application rate was
evaluated from monthly survival of G. robusta tree seedlings at varying application doses of
the fungal formulations. Results showed that M. anisopliae persisted (75.2%) in farm sites a
decade after application. Survival of G. robusta tree seedlings improved by over 60%
following application of the fungal formulations. An optimum of 66.4% seedling survival was
achieved with the granular formulation at the highest dose of 2 g of the granules per seedling
whereas 76.3% was the optimum survival of seedlings achieved with the oil-based formulation
at a higher dose of 25 g/L per seedling. Mean spread of M. anisopliae in the soil was significant
(p < 0.001) in the cropping zone nearest (0.5 - 1.5 m) to the point of fungal application under
the maize + ground nuts intercrop with spread of 26.5% compared to the sole maize (1 1.0%)
and the fallow (8.1%) whereas mean spread at the mid (1.5 - 3.0 m) and furthest (3.0 - 5.0 m)
were non-significant, p = 0.267 and p = 0.223 respectively, in all the cropping regimes. Mean
vertical spread of M. anisopliae in the shallow and deeper soil layers did not differ,/? = 0.860,
although spread was higher in the upper soil zone (16.9%) than in the lower soil zone (11.7 ±
14.44%). Non-target arthropods were not affected by M. anisopliae application in soil for pest
termite control in farmed lands. Mean proportion of non-target arthropods not infected by M.
anisopliae within the 3m trapping area (96.9%) was non-significantly different (p = 0.25) from
mean proportion of non-target arthropods not infected by the fungus in the 6m area (91.9%)
across all the trapping phases of 0, 12 and 28 Weeks after Application of the fungal granules.
M. anisopliae can persist in the soil for atleast a decade with incidence levels under mixed
cropping than sole cropping. Mortality of G. robusta trees in farmland as a result of termite
attack can significantly be reduced by applying the fungus to the seedlings during planting.
Fungal spread can be achieved within the surrounding points of application yet its use has no
or negligible effect on other useful organisms in the soil. There is need to investigate natural
occurrence of AY. anisopliae strains in comparison with ICIPE 30 isolate thus offering a range
of other options of the genus with potential for bio-control in the local agro ecologies. It is
worthwhile noting that the use of the granules by farmers under intercropping conditions as an
integrated approach to pest termite management is plausible.