Seasonal diversity of entomofauna, their impact and management practices in tomato fields in Meru District, Tanzania

Tomato is a highly cultivated vegetable in Tanzania. The intensive tomato cultivation and production in Tanzania has resulted in high pests and diseases build-up. A survey to identify and quantify entomofauna diversity in different seasons and pest management practices in Meru District was conducted. In addition, a laboratory experiment was done to assess the effectiveness of commonly used pesticides SnowBecco (Thiamethoxam) and Belt (Flubendiamide) against two dominating insect pests, white flies (Bemisia tabaci (Gennadius, 1889)) and leaf miner (Tuta absoluta (Meyrick, 1917)), respectively. The results obtained revealed that, tomato fields in Meru District had significantly higher entomofauna build up during dry season than the rainy season (U0.05 (df, 24) = 45, p = 0.0441). More than 70% of all collected entomofauna were dominated by the whiteflies (Bemisia tabaci) and tomato leaf miners (Tuta absoluta) belonging to orders Hemiptera and Lepidoptera, respectively. It was also observed that, the common pesticides management practices were the use of pesticidal cocktail, broad spectrum insecticides, use of botanical pesticides, frequent application of pesticide and insecticides over dosage. Moreover, yield reduction due to whiteflies and tomato leaf miners infestation were observed in terms of reduced fruits number per plant (38 and 18.4%), fruit size (22.4 and 14.2%), and fruits weight per plant by 43.6 and 26.2%, for Bemisia tabaci and Tuta absoluta, respectively. The study showed that the recommended doses in both tested insecticides caused significant pest mortality (F0.05 (df, 19) = 4.367, p = 0.0199) and (F0.05 (df, 19) = 4.761, p = 0.0147) for B. tabaci and T. absoluta, respectively, within a specified period of time. The results suggest that high insect pest infestations could be caused by factors other than development of insecticidal tolerance including inappropriate identification of insect pests due to lack of training, and inappropriate selection and application of insecticides. Consequently, frequent application of broad spectra insecticides not only increases production expenses but also disrupts agroecosystem by killing beneficial entomofauna and disrupting soil organisms that are susceptible to insecticide toxicity

Endophytic fungi for biological control of whitefly and tomato leaf miner in Tanzania

Tomato whiteflies ( Bemisia tabaci ) and leaf miners (Tuta absoluta) are devastating pests of tomato ( Lycopersicon esculentum ). Pest management using broad spectrum synthetic pesticides is discouraged due to harmful effects on human health and the environment. The objective of this study was to assess the potential of endophytic fungi as bioextracts against tomato whiteflies and leaf miners, as an alternative to synthetic insecticides in Tanzania. The study was done using morphological and molecular techniques, during January 2019 to February 2020 in Arusha region in Tanzania. Three endophyte isolates from pyrethrum ( Chrysanthemum cinerariifolium ) and lemon grass ( Cymbopogon citratus ) were identified with resemblance to members of Fusarium sp and Altenaria sp, by 90 and 82 % similarity, respectively; based on phylogenetic clustering patterns and macro- and micro-morphological characteristics. Bioextracts from endophytes of lemon grass leaves (Elg1); and pyrethrum flowers (Epf1) and leaves (Epl1), showed significant repellency properties (F0.05 (df, 15) = 27.052, P = 0.0001) on whiteflies by 54, 76 and 36%, respectively. They also caused significant lethality (F0.05 (df, 11) = 59.559, P = 0.0001) of tomato leaf miner larvae and whiteflies (F0.05 (df, 11) = 53.600, P = 0.0001). The underlying effect was attributed to possession of flavonoid and total phenolics as active ingredients in the bioextracts. This was commensurate to the levels flavonoid and total phenolic contents, which were considerably more in bioextracts of lemon grass and pyrethrum flower (F0.05 (df, 8) = 10.35, P = 0.0114) and (F0.05 (df, 8) = 40.84, P = 0.0003, respectively), than in pyrethrum leaves.Les aleurodes de la tomate ( Bemisia tabaci ) et les mineuses de la tomate (Tuta absoluta) sont des ravageurs d\ue9vastateurs de la tomate ( Lycopersicon esculentum ). La lutte antiparasitaire utilisant des pesticides synth\ue9tiques \ue0 large spectre est d\ue9conseill\ue9e en raison des effets nocifs sur la sant\ue9 humaine et l\u2019environnement. L\u2019objectif de cette \ue9tude \ue9tait d\u2019\ue9valuer le potentiel des champignons endophytes comme bio extraits contre les aleurodes de la tomate et les mineuses de la tomate, comme alternative aux insecticides synth\ue9tiques en Tanzanie. L\u2019\ue9tude a \ue9t\ue9 r\ue9alis\ue9e \ue0 l\u2019aide de techniques morphologiques et mol\ue9culaires, de Janvier 2019 \ue0 F\ue9vrier 2020 dans la r\ue9gion d\u2019Arusha en Tanzanie. Les trois isolats d\u2019endophytes de pyr\ue8thre ( Chrysanthemum cinerariifolium ) et de citronnelle ( Cymbopogon citratus ) ont \ue9t\ue9 identifi\ue9s avec une ressemblance avec des membres de Fusarium sp et Altenaria sp, par 90 et 82% de similitude, respectivement; bas\ue9 sur des sch\ue9mas de regroupement phylog\ue9n\ue9tique et des caract\ue9ristiques macro et micro morphologiques. Bio extraits d\u2019endophytes de feuilles de citronnelle (Elg1); et les fleurs de pyr\ue8thre (Epf1) et les feuilles de pyr\ue8thre (Epl1), ont montr\ue9 des propri\ue9t\ue9s r\ue9pulsives significatives (F0,05 (df, 15) = 27,052, P = 0,0001) sur les aleurodes de 54, 76 et 36%, respectivement. Ils ont \ue9galement caus\ue9 une l\ue9talit\ue9 significative (F0,05 (df, 11) = 59,559, P = 0,0001) des larves de mineuses de la tomate et des aleurodes (F0,05 (df, 11) = 53,600, P = 0,0001). L\u2019effet sous-jacent a \ue9t\ue9 attribu\ue9 \ue0 la possession de flavono\uefdes et de compos\ue9s ph\ue9noliques totaux en tant qu\u2019ingr\ue9dients actifs dans les bioextraits. Cela \ue9tait proportionnel aux teneurs en flavono\uefdes et ph\ue9noliques totales, qui \ue9taient consid\ue9rablement plus \ue9lev\ue9es dans les bioextraits de citronnelle et de fleur de pyr\ue8thre (F0,05 (df, 8) = 10,35, P = 0,0114) et (F0,05 (df, 8) = 40,84, P = 0,0003, respectivement), que dans les feuilles de pyr\ue8thre