School of Pure and Applied Sciences
Permanent URI for this communityhttp://localhost:4000/handle/20.500.12092/1952
Browse
3 results
Search Results
Item Relationship between virulence and repellency of entomopathogenic isolates of Metarhizium anisopliae and Beauveria bassiana to the termite Macrotermes michaelseni(Journal of Insect Physiology, 2009) Mburu, D.M.; Ochola, L.; Maniania, N.K; Njagi, P.G.N.; Gitonga, L.M.; Ndung'u, M.W.; Wanjoya, A.K.; Hassanali, A.Termites encounter a diverse array of potentially useful and harmful fungi in their subterranean habitats. These vary from symbiotic to harmful species with varying levels of virulence. How these hemiedaphic insects survive in habitats with infective fungi is not well understood. Possible mediation of olfactory signals in avoiding contact with entomopathogenic fungi has been explored by a number of workers. In the present study, we initially found that Macrotermes michaelseni detected a virulent isolate of Metarhizium anisopliae from some distance and avoided direct physical contact. We hypothesized that there may be a relationship between virulence and repellency of different isolates of M. anisopliae and Beauveria bassiana to the termite. We compared these for selected isolates of the two fungi. Positive correlations between the two parameters for both sets of isolates of the fungi were obtained. The results show an interesting co-evolutionary phenomenon in which the termite’s response to either M. anisopliae or B. bassiana is directly related to potential harm these fungi can inflict on the insect and that the virulent strains are more likely to be recognized from some distance and avoided.Item Selection of promising fungal biological control agent of the western flower thrips Frankliniella occidentalis (Pergande)(Letters of Applied Microbiology, 2012-02) Niassy, S.; Maniania, N.K; Subramanian, S.; Gitonga, L.M.; Mburu, D.M.; Masiga, D.; Ekesi, S.Aims: Larval stages of Frankliniella occidentalis are known to be refractory to fungal infection compared with the adult stage. The objective of this study was to identify promising fungal isolate(s) for the control of larval stages of F. occidentalis. Methods and Results: Ten isolates of Metarhizium anisopliae and eight of Beauveria bassiana were screened for virulence against second-instar larvae of F. occidentalis. Conidial production and genetic polymorphism were also investigated. Metarhizium anisopliae isolates ICIPE 7, ICIPE 20, ICIPE 69 and ICIPE 665 had the shortest LT50 values of 8Æ0–8Æ9 days. ICIPE 69, ICIPE 7 and ICIPE 20 had the lowest LC50 values of 1Æ1 · 107 , 2Æ0 · 107 and 3Æ0 · 107 conidia ml)1 , respectively. Metarhizium anisopliae isolate ICIPE 69 produced significantly more conidia than M. anisopliae isolates ICIPE 7 and ICIPE 20. Internally transcribed spacers sequences alignment showed differences in nucleotides composition, which can partly explain differences in virulence. Conclusion: These results coupled with the previous ones on virulence and field efficacy against other species of thrips make M. anisopliae isolate ICIPE 69 a good candidate. Significance and Impact of the Study: Metarhizium anisopliae isolate ICIPE 69 can be suggested for development as fungus-based biopesticide for thrips management.Item Compatibility of Metarhizium anisopliae isolate ICIPE 69 with agrochemicals used in French bean production(Journal of Pest Management, 2012-04) Niassy, S.; Maniania, N.K; Subramanian, S.; Gitonga, L.M.; Maranga, R.; Obonyo, A.B.; Ekesi, S.The compatibility of the Metarhizium anisopliae (Metschnikoff) Sorokin isolate ICIPE 69, which is being developed as a biopesticide for the control of Frankliniella occidentalis Pergande, was assessed under laboratory conditions with 12 agrochemicals including 5 insecticides (thiamethoxam, L-cyhalothrin, imidacloprid, chlorpyrifos, diazinon), 1 botanical insecticide (azadirachtin), 2 acaricides (abamectin, spiromesifen), and 3 fungicides (carbendazim, copper hydroxide, probineb) used in French bean production. The insecticides abamectin and imidacloprid were highly compatible with M. anisopliae; thiamethoxam was compatible, whereas azadirachtin and L-cyahalothrin were toxic to the fungus, adversely affecting vegetative growth and sporulation. The acaricide spiromesifen was moderately toxic, while the fungicides carbendazim, probineb, and copper-hydroxide were very toxic to the fungus. The combination of the M. anisopliae isolate ICIPE 69 with imidacloprid or thiamethoxam did not result in any synergistic or antagonistic effects to larvae of F. occidentalis. However, the combination of lower concentrations of the fungus with thiamethoxam resulted in a shorter lethal time (LT50) compared with individual treatments. Our results suggest that application of the fungus with agrochemicals has to be assessed carefully prior to any field intervention.