Effects of metarhizium anisopliae application o~ the diversity of plants, ants, cockroaches and mantids associated with odontotermes termite mounds at mpala research centre - laikipja district (central kenya)

Abstract

Termites are an important component of savanna ecosystems throughout Africa. They feed on dead and living plant cell wall material (wood, leaf litter, roots, dead herbs, grasses, dung and humus). They directly or indirectly modulate the availability of resources such as minerals, fatty acids, vitamins and organic carbon to other species by creating, modifying and maintaining habitats. Their removal from the ecosystem is anticipated to affect the community structure. However, some species can be serious pests of structures, houses, rangelands, tropical forestry and agriculture. In an attempt to manage the damage these species cause, persistent organic pollutants (POPs) including aldrin, dieldrin, endrin, heptachlor and chlordane (cyclodienes) have often been used. In view of the growing concern on the effects of such chemicals on the environment, they have been banned and other alternative strategies have been sought. Alternatives such as chlorpyrifos, isofenphos, and permethrin, are less persistent, but not as effective and need to be frequently applied. It is in this context that biological termiticides with an entomopathogenic fungus Metarhizium anisopliae as the active ingredient has gained popularity. Metarhizium anisopliae is a cosmopolitan, naturally occurring pathogen, which infects over 200 insect species. Since it infects a variety of insect species, there are concerns that it could potentially cause mortality in populations of non-targets including beneficial insects. This study was undertaken to determine the effects of M anisopliae on the diversity of plants and selected insect species associated with Odontotermes termite mounds when the fungus is used for termite control. The selected insect groups were Hymenoptera and Dictyoptera. Effects on plants were also assessed. The research was carried out at the Mpala Research Centre (MRC) in Laikipia District of Kenya. The centre is located in a savannah ecosystem that has been maintained in a relatively undisturbed state, aside from cattle grazing. The diversity of selected insect groups and plants on termite mounds that had been treated with spores of M anisopliae were compared to that of control mounds that had not been treated with the fungus. Invertebrates were sampled using pitfall traps and sweep nets over a period of one and a half years. There was no significant variation in diversities between treated and control mounds (F = 0.016, df = 1,P = 0.8989,). Laboratory assays were conducted to assess the fungus' direct effects on two different species of ants (Crematogaster mimosae and Camponotus sp.). Results indicated that the fungus has varied pathogenicity towards different species of ants. For C. mimosae, the mean mortality for ants exposed 'to M anisopliae was 28.47 ± 1.08% compared to control mortality of 23.33 ± 1.57% (F = 7.29; p = 0.0072). However, the result could be attributed to the optimized infection conditions in the laboratory. In Camponotus sp., significantly higher mean mortalities were' recorded in controls (60) relative to treatments (50) F = 13.01; p = 0.0004). There was no evidence of variation in vegetation cover across the fungal treatments (F = 0.003, df = 1, p = 0.96). It can be concluded that M anisopliae isolate ICIPE 30 does not have negative effects against nontarget organisms associated with Odontotermes sp. termites, and can therefore be used for the control of termites.