Evaluation of Metarhizium anisopliae for integrated management of termite infestation on farmed lands

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 (11.0%) 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, p = 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 M. 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.