Nguya K. Maniania

Mortality in Three African Tephritid Fruit Fly Puparia and Adults Caused by the Entomopathogenic Fungi, Metarhizium anisopliae and Beauveria bassiana

The pathogenicity of 13 isolates of Metarhizium anisopliae and two isolates of Beauveria bassiana to Ceratitis capitata and Ceratitis var. rosa fasciventris exposed as late third instar larvae in sand was evaluated in the laboratory. All isolates caused a significant reduction in adult emergence and a corresponding large mortality on puparia of both species. All isolates also induced large deferred mortality in emerging adults following treatment as late third instar larvae. On C. capitata , seven isolates ( M. anisopliae ICIPE 18, 20, 32, 60 and 69 and B. bassiana ICIPE 44 and 82) caused significantly higher mortality on puparia than other isolates. With the exception of ICIPE 32, the other four isolates of M. anisopliae above were the most pathogenic against C. r. fasciventris . Dose-response study carried out with these isolates of M. anisopliae on the two species of flies above plus another species, Ceratitis cosyra showed that the dose-mortality regression lines of ICIPE 18 and 20 were steeper with lower LC 50 values when compared with ICIPE 60 and 69 on the three species. When these two isolates were evaluated with regard to their pathogenicity to different pupal age, adult emergence was found to increase with increasing pupal age with a corresponding decrease in mortality in puparia and emerging adults in the three species of fruit flies. M. anisopliae ICIPE 18 and 20 were equally pathogenic to all pupal ages tested in C. capitata and C. cosyra but ICIPE 18 was more pathogenic to older puparia of C. r. fasciventris than ICIPE 20. Our results suggest that soil inoculation with M. anisopliae under mango trees might form an important component of integrated pest management strategies in areas where these three species of fruit fly coexist.

Pathogenicity of Metarhizium anisopliae (Metsch.) Sorokin and Beauveria bassiana (Balsamo) Vuillemin, to three adult fruit fly species: Ceratitis capitata (Weidemann), C. rosa var. fasciventris Karsch and C. cosyra (Walker) (Diptera :Tephritidae)

The pathogenicity of two isolates of Beauveria bassiana and 12 of Metarhizium anisopliae towards adult fruit flies, Ceratitis capitata and Ceratitis rosa var. fasciventris was tested in the laboratory. Fruit flies were exposed to dry conidia evenly spread on velvet material covering the inner side of a cylindrical plastic tube. All isolates tested were pathogenic to both species of fruit flies. Mortality ranged from 7 to 100% in C. capitata and from 11.4 to 100% in C. rosa var. fasciventris at 4 days post-inoculation. Six isolates, M. anisopliae ICIPE 18, 20, 32, 40, 41 and 62, were highly pathogenic to both C. capitata and C. rosa var. fasciventris. The LT90 values of the most pathogenic isolates ranged between 3–4 days in both insects. Because of the difficulties in rearing C. cosyra, only the isolates that were highly pathogenic to both C. rosa var. fasciventris and C. capitata were tested against adult C. cosyra. They caused mortality of between 72–78% at 4 days post-inoculation. The LT90 values in all the isolates did not exceed 4 days. One of the most pathogenic isolates, M. anisopliae ICIPE 20, was evaluated against C. capitata and C. rosa var. fasciventris in cage experiments using threeautoinoculators (maize cob, cheesecloth and Petri dish) in an autoinoculative deviceconsisting of plastic mineral bottle. Mortality of between 70–93% was observed in flies of both species that were captured from the cages and held under laboratoryconditions. These results indicate the possibility of fruit fly suppression withentomopathogenic fungi using an autoinoculative device.

Effect of Temperature on Germination, Radial Growth and Virulence of Metarhizium anisopliae and Beauveria bassiana on Megalurothrips sjostedti

The effect of temperature on germination, radial growth and pathogenic activity of two strains of Beauveria bassiana and four strains of Metarhizium anisopliae on the legume flower thrips, Megalurothrips sjostedti , was studied in the laboratory. Germination, radial growth and pathogenic activity was low for all strains at 15 C. Optimum temperature for germination, radial growth and pathogenic activity ranged between 25-30 C. The fastest growing strain at 25-30 C was M. anisopliae strain ICIPE 69. Compared to other strains, ICIPE 69 also appeared to have a broad temperature range of pathogenic activity against the pest. The significance of these findings in relation to control of M. sjostedti is discussed.

Effect of constant temperatures on germination, radial growth and virulence of Metarhizium anisopliae to three species of African tephritid fruit flies

The effect of temperatureon conidial germination, mycelial growth, andsusceptibility of adults of three tephritidfruit flies, Ceratitis capitata(Wiedemann), C. fasciventris (Bezzi) andC. cosyra (Walker) to six isolatesof Metarhizium anisopliae were studied inthe laboratory. There were significantdifferences among the isolates in the effect oftemperature on both germination and growth.Over 80% of conidia germinated at 20, 25 and30°C, while between 26 and 67% conidiagerminated at 35°C and less than 10% at15°C within 24 hours. Radial growth was slowat 15°C and 35°C with all of theisolates. The optimum temperature forgermination and mycelial growth was 25°C. Mortality caused by the six fungal isolatesagainst the three fruit fly species varied withtemperature, isolate, and fruit fly species.Fungal isolates were more effective at 25, 30and 35°C than at 20°C. The LT90values decreased with increasing temperature upto the optimum temperature of 30°C. Therewere significant differences in susceptibilitybetween fly species to fungal infection at allthe temperatures tested.

Relationship between virulence and repellency of entomopathogenic isolates of Metarhizium anisopliae and Beauveria bassiana to the termite Macrotermes michaelseni

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 termites 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.

Effect of soil temperature and moisture on survival and infectivity of Metarhizium anisopliae to four tephritid fruit fly puparia.

The infectivity of 4 isolates of Metarhizium anisopliae to puparia of Ceratitis capitata treated as late third-instar larvae in unsterilized soil was investigated in the laboratory under controlled temperature and moisture. At 20-30 degrees C, mortality in puparia was highest at water potential of -0.1 and -0.01 mega Pascal (MPa) and lowest at water potential of -0.0055 and -0.0035 MPa in all the isolates. In wetter soil however, isolates ICIPE 20 and 60 caused significantly higher mortality than ICIPE 18 and 69. The survival of conidia in drier soil (-0.1 MPa) was not adversely affected at all temperatures. However, in wet soil (-0.0035 MPa) there was drastic reduction in colony counts in ICIPE 18 and 69 at 25 and 30 degrees C but conidial density in ICIPE 20 and 60 remained at the initial level at 14 days after inoculation at all temperatures. When ICIPE 20 was evaluated against three other fruit fly species (Ceratitis cosyra, Ceratitis rosa, and Ceratitis fasciventris), significant reduction in adult emergence and higher pupal mortality occurred in C. cosyra and C. fasciventris than in C. rosa at a combination of 15 and 20 degrees C and -0.1 and -0.0035 MPa. However, at higher temperature and the same moisture level, the isolates were equally pathogenic across the 3 species. It is probable that in addition to pathogen cycling and multiplication from dead infected insects in the soil, a balance between microbial degradation and replenishment of inoculum of virulent isolates occur through fluctuations in, and intricate interactions between temperature and moisture levels. This study is indicative of the potential of using isolate ICIPE 20 for soil inoculation against pupariating third-instar larva of fruit flies, thus providing a novel alternative to chemical soil application.

Susceptibility of Megalurothrips sjostedti developmental stages to Metarhizium anisopliae and the effects of infection on feeding, adult fecundity, egg fertility and longevity

The susceptibility of immature stages of the legume flower thrips, Megalurothrips sjostedti, to the entomopathogenic fungus Metarhizium anisopliae, was investigated under laboratory conditions. The adult stage was found to be more susceptible to infection than the larval and pupal stages. Mortality at all stages was dose‐dependent, with the highest concentration of 1×108 conidia ml−1 producing the highest mortality (26, 46 and 100% for larvae, pupae and adults, respectively) at 8 days post‐inoculation. At the same concentration, daily pollen consumption was significantly reduced at 2 days after treatment in infected adults but more slowly in infected larvae. Fecundity, egg fertility and longevity in adults surviving infection as larvae were significantly reduced compared to the control.

African edible insects for food and feed: inventory, diversity, commonalities and contribution to food security

This paper reviews entomophagy as practised in Africa within the context of food and nutritional security by providing an inventory of the various species of insects that are consumed on the continent and suggests a research for development (R4D) agenda for sustainable utilisation of insects for food and feed. Our survey showed that over 470 species of insects are eaten in Africa. The Central African region remains the most important hotspot of having a culture of entomophagy. The insects mostly eaten in the continent are dominated by the orders Lepidoptera, Orthoptera and Coleoptera. Commonalities were observed across the majority of the insects consumed across Africa, providing opportunities for related R4D activities. An R4D agenda and pathways for using edible insects suggest that socio-economics and marketing studies should address issues of communities’ perceptions, based on their cultural background, income and beliefs. Cost-effective rearing, harvesting and processing technologies are required to ...

Prospects for biological control of the western flower thrips, Frankliniella occidentalis, with the entomopathogenic fungus, Metarhizium anisopliae, on chrysanthemum

The potential of Metarhizium anisopliae (Metsch.) Sorok. for the control of Frankliniella occidentalis (Pergande) on chrysanthemum cuttings was evaluated in greenhouse experiments. The fungus significantly reduced both the adult and larval populations of F. occidentalis, although the level of control of larval populations was much lower than for adults. Combined application of M. anisopliae and Methomyl (Lannate®), however, resulted in a significant reduction of both the larval and adult stages. The use of both control agents might be helpful in reducing the selection pressure for resistance to chemical insecticides, thereby delaying or preventing the build-up of resistant populations in greenhouses.

Influence of temperature on virulence of fungal isolates of Metarhizium anisopliae and Beauveria bassiana to the two-spotted spider mite Tetranychus urticae.

Twenty-three isolates of Metarhizium anisopliae (Metschnikoff) Sokorin and three isolates of Beauveria bassiana (Balsamo) Vuillemin (Ascomycota: Hypocreales: Clavicipitaceae) were assessed for their virulence against the two-spotted spider mite, Tetranychus urticae Koch (Acari: Tetranychidae). Based on the screening results, nine isolates of M. anisopliae and two isolates of B. bassiana were tested for their virulence against young adult (1- to 2-day-old) female T. urticae at constant temperatures of 20, 25, 30 and 35°C. At all temperatures tested, all the fungal isolates were pathogenic to T. urticae but mortality varied with isolates and temperatures. Fungal isolates were more virulent at 25, 30 and 35°C than at 20°C. The lethal time to 50% mortality (LT50) and lethal time to 90% mortality (LT90) values decreased with increased temperature. There were no significant differences in virulence between fungal isolates at 30 and 35°C; however, significant differences were observed at 20 and 25°C.