~ 1354 ~ Journal of Entomology and Zoology Studies 2021; 9(1): 1354-1359 E-ISSN: 2320-7078 P-ISSN: 2349-6800 www.entomoljournal.com JEZS 2021; 9(1): 1354-1359 © 2021 JEZS Received: 19-11-2020 Accepted: 21-12-2020 Esther Adhiambo Abonyo (1) College of Biological and Physical Sciences, University of Nairobi, P. O. Box, 30197 (00100), Nairobi, Kenya (2) Noctuid Stem Borer Biodiversity Project, icipe, Nairobi, P. O. Box 30772 (00100), Nairobi, Kenya George Otieno Ongámo (1) College of Biological and Physical Sciences, University of Nairobi, P. O. Box, 30197 (00100), Nairobi, Kenya (2) Noctuid Stem Borer Biodiversity Project, icipe, Nairobi, P. O. Box 30772 (00100), Nairobi, Kenya Gideon Nzioka Nyamasyo College of Biological and Physical Sciences, University of Nairobi, P. O. Box, 30197 (00100), Nairobi, Kenya Catherine Wanjiru Lukhoba College of Biological and Physical Sciences, University of Nairobi, P. O. Box, 30197 (00100), Nairobi, Kenya Gerphas Okuku Ogola Noctuid Stem Borer Biodiversity Project, icipe, Nairobi, P. O. Box 30772 (00100), Nairobi, Kenya Midingoyi Soul-Kifouly Socioeconomic Unit, icipe, Nairobi, P. O. Box 30772 (00100), Nairobi, Kenya Hippolyte Affognon Socioeconomic Unit, icipe, Nairobi, P. O. Box 30772 (00100), Nairobi, Kenya Bruno P Le Ru (1) Noctuid Stem Borer Biodiversity Project, icipe, Nairobi, P. O. Box 30772 (00100), Nairobi, Kenya (2) UMR IRD 247 Laboratoire Evolution, Génomes, Comportement et Ecologie, Diversité, Ecologie et Evolution des Insectes Tropicaux, CNRS, 91198 – Gif-sur-Yvette, France and Université de Paris-Sud, 91405 - Orsay, France Corresponding Author: Esther Adhiambo Abonyo (1) College of Biological and Physical Sciences, University of Nairobi, P. O. Box, 30197 (00100), Nairobi, Kenya (2) Noctuid Stem Borer Biodiversity Project, icipe, Nairobi, P. O. Box 30772 (00100), Nairobi, Kenya Cereal stem borer species complex and establishment status of highland larval parasitoid, Cotesia sesamiae (Cameron) in coastal Taita Hills, Kenya Esther Adhiambo Abonyo, George Otieno Ongámo, Gideon Nzioka Nyamasyo, Catherine Wanjiru Lukhoba, Gerphas Okuku Ogola, Midingoyi Soul-Kifouly, Hippolyte Affognon and Bruno P Le Ru Abstract Sorghum and maize are important crops whose production is constrained by stem borers such as Busseola fusca. In Kenya, two distinct populations of Cotesia sesamiae, a parasitoid of B. fusca exist. The virulent highland biotype was released in the coastal region where the avirulent biotype existed. However, post release surveys were not done to assess for establishment. This survey was undertaken in release areas where 100 maize plants were inspected for infestation and ten plants dissected to recover stem borers in each farm. Results revealed that B. fusca was the most dominant pest (85.5%). Overall infestation was 19.17±2.48% and varied significantly among stem borer species ( 2 2  =16.86, p=0.00022) Overall parasitism was 10.78±4.34% and did not show significant variation from parasitoid pre-release rates (V=3, p>0.05). Cotesia sesamiae was recovered from C. partellus only suggesting that it was the avirulent biotype. The highland C. sesamiae did not establish in coastal Kenya. Keywords: Cotesia sesamiae, virulent, avirulent, biotype, Busseola fusca, redistribution Introduction Busseola fusca (Fuller) (Lepidoptera: Noctuidae), is one of the important field pests of maize (Zea mays L.) and sorghum (Sorghum bicolor (L) Moench) in Sub-Saharan Africa (SSA) [1, 2] . Before the introduction of maize from Meso America in the 16 th century [3] and the extensive cultivation of sorghum, B. fusca subsisted on non-cereal wild host plants [1] . Following the introduction and extensive cultivation of these crops, B. fusca shifted to cultivated habitat [4] where yield losses associated with its infestation was estimated at 10-14% [5] . In Kenya, these losses are mostly incurred in regions considered the ‘bread basket’ of the country [6, 7] and characterized as high potential zones (highland tropics, moist transitional and moist mid- altitude) [8] . Distribution of B. fusca is favoured by low temperatures, an attribute found in the afore-mentioned high potential zones [9-15] . Busseola fusca infestations cause considerably higher yield losses among small scale farmers who cannot afford chemicals but rely mainly on naturally available enemies. Various natural enemies including forty parasitoids, five predators and eight pathogens have been reported to attack B. fusca in East Africa [16] . Of these, the most common is the braconid, larval endoparasitoid, Cotesia sesamiae (Cameron) [17, 18] . In addition to B. fusca, C. sesamiae can attack Chilo partellus (Swinhoe), Chilo orichalcociliellus (Strand) and Sesamia calamistis Hampson [19] . Several strains of C. sesamiae varying in their insect host ranges have been found in Africa [20] . In Kenya, studies have shown that two C. sesamiae biotypes with variation in developmental success in B. fusca exist. The virulent strain (found in highlands) is able to develop successfully while the avirulent strain (found at the coast) is encapsulated by B. fusca [12, 21-23] . Evolution of biotypes was the result of trade-offs brought by local adaptation to host community structure [24] and is of vital importance in pest management. Cotesia sesamiae distinct populations have been utilized in the biological control redistribution programme during which natural enemies were exchanged between African regions and different localities within a country to manage indigenous stem borer pests [25] . In Kenya, the