Linus M. Gitonga
Jomo Kenyatta University of Agriculture and Technology
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Featured researches published by Linus M. Gitonga.
Biological Control | 2002
Linus M. Gitonga; William A. Overholt; Bernhard Löhr; J.K. Magambo; J.M. Mueke
Abstract A locally available anthocorid predator, Orius albidipennis Reuter, was evaluated as a candidate biocontrol agent for Megalurothrips sjostedti Trybom, a major pest of French beans, Phaseolus vulgaris (L), in Kenya. The functional response of adult O. albidipennis to larval and adult M. sjostedti was studied at 15, 25, and 28 °C and densities of 5, 10, 20, and 30 larval and adult M. sjostedti per cage, over 24 h. More larvae and adult M. sjostedti were killed at the higher densities and with an increase in temperature. The data provided good fit to both type I and II functional response models. Attack rates increased with temperature for both the second instar larva and adult M. sjostedti. Handling times for the larvae decreased with an increase in temperature while those for the adults increased with increase in temperature. The implications of these results are discussed.
Entomologia Experimentalis Et Applicata | 2012
S. Niassy; Nguya K. Maniania; Sevgan Subramanian; Linus M. Gitonga; Sunday Ekesi
The performance of an autoinoculation device was evaluated in field cage experiments for control of Western flower thrips, Frankliniella occidentalis (Pergande) (Thysanoptera: Thripidae), in French bean, Phaseolus vulgaris L. var. Samantha (Fabaceae). Treatments consisted of a fungus‐treated device with and without semiochemical (Lurem‐TR), and a fungus‐free device as control; the fungus used was Metarhizium anisopliae (Metchnikoff) Sorokin (Hypocreales: Clavicipitaceae). The overall mean number of conidia acquired by a single insect was higher in the fungus‐treated semiochemical‐baited device than in the device without semiochemical: 5.0 ± 0.6 × 104 vs. 2.2 ± 0.4 × 104 conidia per insect. The overall thrips mortality was also higher in the semiochemical‐baited device than in the device without the semiochemical: 59.3 ± 3.9 vs. 41.7 ± 3.5%. Conidial viability was not affected in the M. anisopliae‐treated device without semiochemicals, 7 days after treatment, whereas it was considerably decreased – from 81.0 ± 1.3 to 6.5 ± 1.1%, 2 and 7 days post‐inoculation – in the M. anisopliae‐treated semiochemical‐baited device. Thrips mortality was positively correlated with M. anisopliae conidial viability, and conidial viability was negatively correlated with conidial acquisition. This suggests that the semiochemical volatiles reduced the conidial viability, which in turn resulted in significant reduction in thrips mortality, despite the highest conidial acquisition in the semiochemical‐baited fungus‐treated device. Thrips density per plant was significantly reduced in both fungus‐treated treatments (with semiochemical: 8.7 ± 1.7 adults per plant; without semiochemical: 6.6 ± 1.4 adults per plant) compared with the fungus‐free control (19.8 ± 2.6 adults per plant). These results demonstrate the potential for an autoinoculation device strategy for the control of thrips, particularly in screenhouses.
Journal of Economic Entomology | 2012
Donald L. Kachigamba; Sunday Ekesi; Mary Ndungu; Linus M. Gitonga; Peter E. A. Teal; Baldwyn Torto
ABSTRACT We investigated conspecific and heterospecific oviposition host discrimination among four economically important fruit fly pests of mango in Africa (Ceratitis capitata, Wiedemann; C. fasciventris, Bezzi; C. rosa, Karsch, and C. cosyra, Walker) with regard to host-marking behavior and fecal matter aqueous solutions. The objective of the study was to get insight into the potential of managing these pests using the host-marking technique. Observations were done on mango slices marked by the flies and treated with aqueous solutions of fecal matter of the flies, respectively. In both host-marking and fecal matter experiments, C. cosyra, which is the most destructive species of the four on mango, was exceptional. It only discriminated against hosts treated with its fecal matter but with lower sensitivity while C. capitata and C. fasciventris discriminated against hosts marked by it or treated with its fecal matter and with higher sensitivity. Our results provide evidence for potential of managing some of the major fruit fly species infesting mango in Africa using the host-marking pheromone of the mango fruit fly, C. cosyra.
Biocontrol Science and Technology | 2007
Joseph M. Baya; Srinivasan Sithanantham; Linus M. Gitonga; Ellie O. Osir; Stephen Gaya Agong
Abstract In response to emerging interest in commercial mass production of Trichogramma for Helicoverpa armigera biocontrol in eastern Africa, laboratory experiments were undertaken to assess the scope for genetic enhancement of the parasitisation potential of native strains of the local common trichogrammatid species, Trichogrammatoidea sp. nr. lutea. Four promising strains (ex-Kilifi – Kilifi District, ex-Kwa Chai – Kibwezi District, ex-Rarieda – Bondo District and ex-Ebuhayi, Kakamega District) were tested for cross-mating in reciprocal combinations with focus on fecundity and progeny female ratio. While all the crosses resulted in F1 progeny of both sexes, significant differences were observed between homogamic and reciprocal heterogamic crosses in fecundity, progeny production, proportion of female progeny and adult longevity. Among all the crosses, the cross between ex-Rarieda strain females and ex-Kilifi strain males resulted in progeny that was significantly superior in fecundity and progeny female ratio. Conversely, Kilifi strain females crossed to males from ex-Rarieda strain gave rise to progeny with relatively low fecundity and female ratio. There were significant differences between homogamic crosses and most reciprocal heterogamic crosses in the major biological attributes. Genotypic and phenotypic variance-covariance matrices generated for six life-history traits showed high positive correlations for most traits in both inbred (P<0.05) and reciprocal heterogamic crosses (P<0.05 and P<0.001). Fecundity and number of female offspring were the most important factors in the heterogamic crosses. The results confirmed the scope for genetic enhancement through inter-strain crossing for improving the field impact potential of T. sp. nr. lutea being targeted for commercial mass production.
International Journal of Tropical Insect Science | 2002
Linus M. Gitonga; Bernhard Löhr; W.A. Overholt; J. K. Magambo; J. M. Mueke
The effects of temperature on the development of Orius albidipennis (Reuter) (Hemiptera: Anthocoridae), reared on its prey, Megalurothrips sjostedti (Trybom) (Thysanoptera: Thripidae), were studied in the laboratory. Nymphal mortality was 87, 48 and 38 % at 20, 25 and 30 °C, respectively. With the exception of first-instar nymphs, percentage mortality was lowest at 25 °C. Pre-oviposition period and longevity decreased with an increase in temperature. Mean daily and total fecundity were 2.1 and 76.4 respectively at 25 °C. The mean developmental period from oviposition to adult eclosion was 27.7, 14.1 and 10.9 days at 20, 25 and 30 °C respectively. There was a linear relationship between temperature and developmental rate (1 /day) of O. albidipennis. Lower thermal thresholds were 13.8, 13.5, 12.7, 15.0, 13.8 and 12.5 °C for eggs and nymphal stages 1 to 5, respectively, with the corresponding average degree-day requirement of 46.9, 42.6, 33.3, 29.2, 26.1 and 51.4 days,, respectively. The implications of these results for biological control of thrips are discussed.RésuméLes effets de la température sur le développement d’Orius albidipennis (Reuter) (Hemiptera: Anthocoridae) élevé sur sa proie, Megalurothrips sjostedti (Trybom) (Thysanoptera: Thripidae), ont été étudiés au laboratoire. La mortalité des nymphes est respectivement de 87,48 et 38% à 20, 25 et 30 °C. A l’exception de la nymphe de 1er stade, la mortalité est plus faible à 25 °C. La durée de pré-oviposition et la longévité diminuent lorsque la température augmente. La fécondité moyenne journalière et totale sont respectivement de 2,1 et 76,4 à 25 °C. La durée moyenne de développement de l’oviposition à l’émergence de l’adulte est respectivement de 27,7, 14,1 et 10,9 jours à 20, 25 et 30 °C. Il existe une relation linéaire entre le température et le taux de développement (1/jour) d’Orius albidipennis. Les seuils thermiques de développement inférieurs sont respectivement de 13,8, 13,5, 12,7, 15,0, 13,8 et 12,5 °C pour l’oeuf et les stades nymphaux 1 à 5 avec respectivement un besoin moyen en degrés jours de 46,9,42,6,33,3,29,2,26,1 et 51,4 jours. On discute des conséquences de ces résultats sur la lutte biologique contre les thrips.
Pest Management Science | 2018
Miriam Kungu; Emilie Deletre; Sevgan Subramanian; Komi Km Fiaboe; Linus M. Gitonga; Zipporah Osiemo Lagat; Thibaud Martin
BACKGROUND Tetranychus evansi and T. urticae spider mites are known major pests of Solanaceae. Smallholders in Africa rely heavily on pesticide treatments. However, farmers claim that pesticides are generally ineffective despite high-frequency sprays. New management solutions are thus urgently needed. This study assessed the efficacy of using acaricide-treated nets combined with predatory mite release for controlling spider mites. RESULTS The results showed the acaricide-treated net alone was more effective at reducing numbers of T. urticae than T. evansi. We observed the opposite for release of the predatory mite Phytoseiulus longipes. This difference could be explained by the specific dispersion strategies of the two spider mite pests; T. evansi is gregarious, whereas T. urticae dispersed rapidly. Joint application of both techniques resulted in a synergetic effect that reduced T. evansi and T. urticae spider mite numbers close to zero. The synergetic effect could be explained by predator avoidance behaviour of the prey spider mites, resulting in higher prey trapping and killing rates on acaricide-treated nets, while P. longipes fed on spider mite eggs. CONCLUSION These techniques are profitable for smallholders as they are not expensive and avoid residues on the crop.
Biological Control | 2006
Caleb Momanyi; Bernhard Löhr; Linus M. Gitonga
The Journal of horticultural science | 2008
Monicah M Waiganjo; Linus M. Gitonga; Jones Mueke
The Journal of horticultural science | 2011
Sjn Muriuki; Linus M. Gitonga; Charles N Waturu; Hellen Kutima
The Journal of horticultural science | 2009
Lucy Kananu Murungi; Markus Knapp; Peter Wafula Masinde; G Onyambu; Linus M. Gitonga; Stephen Gaya Agong