Browsing by Author "Kahuthia-Gathu, Ruth"

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    Association of a native predator Chilocorus sp. (Coleoptera: Coccinelidae) with a new exotic mango pest, Aulacaspis tubercularis Newstead (Hemiptera: Diaspididae) in Ethiopia
    (The Entomological Society of Israel, 2017-07) Djirata, Ofgaa; Getu, Emana; Kahuthia-Gathu, Ruth
    White Mango Scale Aulacaspis tubercularis Newstead, 1906 was reported for the first time in 2010 from mango orchards belonging to Green Focus Ethiopia Ltd in western Ethiopia. It was hypothesized that the pest could enter Ethiopia with mango seedlings imported by the same company. The present study surveyed natural enemies of the pest and their population dynamics in western Ethiopia. Larvae of Chilocorus sp. (Coleoptera: Coccinelidae) were found feeding ravenously on live mango scales. There was a statistically significant (p<0.05) positive correlation between the A. tubercularis and Chilocorus sp. populations in both orchards, implying that the predator was not suppressing the pest population. There was no significant difference in the mean numbers of the predatory larva populations between Arjo and Bako orchards (p>0.05). Populations of White Mango Scale and its predator showed remarkably similar fluctuations, with their abundancies reaching peaks during same months. It has been concluded that the native predator got associated with the exotic insect pest recently, and its population may gradually build up. It is suggested that implementation of Chilocorus sp. as a biocontrol agent would be a sound strategy in the management of White Mango Scale in western Ethiopia, together with other control options
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    Evaluation of neem formulations for the control of selected pests of French beans (phaseolus vulgaris. L.)
    (2012-02-22) Kahuthia-Gathu, Ruth; Ogol, Callistus, K. P. O.; Sithanantham, S.; Gaya, Agong S.
    Evaluation on efficacy of neem seed oil (NSO) and neem kernel cake powder (NKCP) as compared to synthetic pesticides against Aphis fabae, Megarulothrips sjostedti and frankliniella species and their effects on natural enemies was conducted at Jomo Kenyatta University of Agriculture and Technology (JKUAT), Thika District, Central Province of Kenya, between August 1998 and June 1999. NKCP/wannin and Gaucho (imidochloroprid) were applied as seed treatment, NKCP and Furadan (carbofuran) as soil amendment, while NSO, neem kernel cake powder water extract (NKCP/WE) and Karate (lambda-cyhalothrin) as foliar sprays, replicated four times in a Rondomixed Complete Block Design (RCBD). The parameters involved were seed germination, leaf damage, flower drop, crop yield, pod quality, thrips and aphid infestation, parasitoid and predator populations. NKCP/wannin had the highest germination and differed significantly from NKCP soil amendment. There was no significant difference (P>0.05) in leaf damage and infestation by Frankliniellla species amongst the treatments. There was significant difference in aphid, adult thrips and larvae population amongst the treatments. However, treatments with Karate resulted with the lowest infestation by thrips and aphids. There was a significant difference in the population of Megarulothrips sjostedti among the treatments during the reproductive stage, with NSO and NKCP/WE treated plots having significantly low population. The mean number of flower drops differed significantly among the treatments. The parasitoid and predator population compared within the plots sprayed with NKCP/WE and control, but different significantly from plots sprayed with Karate an indication that Karate adversely affected the population. Although there was no significant difference (P>0.05) in pod yield among the treatments, the pod quality differed significantly (P<0.05) amongst the treatments. High percentage of unblemished pods was obtained in plots sprayed with NSO, NKCP/WE and Karate. The high percentage difference in pod quality was attributed to high infestation of thrips. The amount of NKCP used, as a soil amendment is not economical due to the large quantities required. Thus seed treatment using NKCP could be used instead of the conventional pesticides as it is cheap and little amounts are required. NSO and NKCP/water extract could also be used as alternatives to Karate as they reduced thrip population thus reducing the extent of pod damage and had no adverse effects on the natural enemies.
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    Reproductive Potential of Fall Armyworm Spodoptera Frugiperda (J.E. Smith) and Effects of Feeding on Diverse Maize Genotypes under Artificial Infestation
    (Frontiers in Insect Science, 2022-09) Anyanda, Geoffrey N.; Anani, Y. Bruce; Makumbi, Dan; Ahonsi, Monday; Kahuthia-Gathu, Ruth; Namikoye, Samita E.; Beyene, Yoseph; Prasanna, B. M.
    Fall armyworm (FAW) Spodoptera frugiperda (J.E. Smith) has become a major threat to maize production in Africa. In this study, six maize genotypes were assessed for their resistance to FAW under artificial infestation in both laboratory and net house conditions. These included two FAW-tolerant hybrids (CKHFAW180294 and CKH191221), two commercial hybrids (WE2115 and CKH10717), and two open-pollinated varieties (ZM523 and KDV4). Larval development time and reproductive potential were assessed on maize leaves in the laboratory and a life table for FAW was constructed. The maize genotypes were also artificially infested with three FAW neonates at two phenological stages (V5 and V7) and reproductive stage (R1) in the net house. Leaf and ear damage scores were recorded on a scale of 1–9. Larval development time varied significantly between maize genotypes with the highest on CKH191221 (16.4 days) and the lowest on KDV4 (13.7 days). The intrinsic rate of natural increase for life tables varied from 0.24 on CKH191221 to 0.41 on KDV4. Mean generation time of FAW ranged from 17.6 to 22.8 days on KDV4 and CKH191221, respectively. Foliar damage was the lowest on CKH191221, and the highest on KDV4 at V7 infestation stage in week 1. CKH191221 had the lowest ear damage score, whereas ZM523 had the highest scores at V5 infestation stage. The highest and lowest yield reductions were observed on ZM523 (64%) at V7 infestation stage and CKHFAW180294 (6%) at R1 infestation stage, respectively. The results indicated the potential for developing tropical mid-altitude maize germplasm with native genetic resistance to FAW.