INSECT ANTAGONISTIC BIO-INOCULANTS FOR NATURAL CONTROL OF LEAF-MINING INSECT PESTS OF FRENCH BEANS

Fungal endophytes, specifically, Trichoderma asperellum , Beauveria bassiana and Metarhizium anisopliae ; strains M2RT4, S4SU1 and S4ST7, respectively, are known to deter aphid infestation and damage to leguminous crops, but no research exists on their biochemical profiles and effects on French bean ( Phaseolus vulgaris ) leaf miners. The objective of this study was to assess the ability of these endophytic bio-inoculants to produce extracellular enzymes, as well as determine their impact on French beans seedling emergence and growth, and leaf miner fecundity and pupation. Laboratory and greenhouse experiments were conduct at the International Centre of Insect Physiology and Ecology (ICIPE, Nairobi), and the University of Bonn (Germany). Bio-priming French bean seeds by soaking in fungal suspension containing 108 conidia/ ml for 4 hr positively impacted on seedling vigour. Six weeks after germination, all bio-inoculant treatments improved nodulation by 1.5-1.7 folds, while S4SU1 and M2TR4 improved shoot biomass by ~ 2g. In vitro, spore suspensions of these isolates were highly toxic to leaf miner larvae, often resulting in high mortalities and a suppression of pupation by over 70%. All tested isolates exhibited protease (Index=1.22), lipase (Index=1.32) and cellulase (Index=1.06) activities; with M. anisopliae being the best enzyme secretor when cultured under dark conditions on enzyme-specific substrate for 7-14 days. In vivo B. bassiana-primed seedlings deterred larval feeding and development, resulting in reduced number of larvae, pupae and adults, by 65.3, 43.2 and 54.0%, respectively. For the first time, this study showed that bio-priming French bean seeds with bio-inoculants can boost P. vulgaris growth and nodulation, consequently altering its interaction and response to leaf miner infestation, feeding and damage to treated seedlings. These bio-inoculants, thus, hold great potential as crop protection agents and could be safely used for priming seeds prior to planting, if leaf mining damages and associated yield losses in French beans are to be minimised in an environmentally sound manner. Further studies should be undertaken to elucidate the mechanisms involved in plant growth promotion, nodulation and insect feeding deterrence.Les endophytes fongiques, sp\ue9cialement, Trichoderma asperellum , Beauveria bassiana et Metarhizium anisopliae ; souches M2RT4, S4SU1 et S4ST7, respectivement, sont connues pour dissuader l\u2019infestation et le dommage des aphids sur les plantes l\ue9gumineuses, mais aucune recherche n\u2019a \ue9t\ue9 men\ue9e sur leurs profils biochmiques et leurs effets sur les insectes mineurs de feuilles du haricot vert ( Phaseolus vulgaris ). L\u2019objectif de cette \ue9tude \ue9tait d\u2019\ue9valuer la capacit\ue9 endophytique de ces bio-inoculants \ue0 produire des enzymes extra-cellulaires, ainsi que de d\ue9terminer leurs impacts sur l\u2019\ue9mergence et la croissance des plantules du haricot vert, sur la f\ue9condit\ue9 et la nymphose du mineur des feuilles. Des exp\ue9rimentations de laboratoire et sous serre on \ue9t\ue9 conduites au Centre International de Physiologie et d\u2019Ecologie d\u2019Insecte (ICIPE, Nairobi), et \ue0 l\u2019Universit\ue9 de Bonn (Allemagne). Le bio-amor\ue7age des graines du haricot vert par trempage dans une suspension fongique contenant 108 conidies/ml pendant 4heures a positivement imapct\ue9 la vigueur des plantules. Six semaines apr\ue8s la germination, tous les traitements de bio-inoculants ont augment\ue9 la nodulation par 1,5-1,7 fois, pendant que S4SU1 et M2TR4 ont augment\ue9 la biomasse des pousses d\u2019environ 2g. En conditions in vitro, les suspensions de spores de ces isolats \ue9taient fortement toxiques aux larves des mineurs de feuilles, r\ue9guli\ue8rement provoquant de grandes mortalit\ue9s et une suppression de la nymphose de plus de 70%. Tous les isolats test\ue9s ont produit des activit\ue9s protease (indice=1,22), lipase (indice=1,32) et cellulase (indice=1.06); avec M. anisopliae constiuant le meilleur s\ue9creteur d\u2019enzyme alors qu\u2019il est cultiv\ue9 dans le noir sur un substrat d\u2019enzyme sp\ue9cifique pendant 7-14 jours. En conditions in vitro, les plantules amorc\ue9es avec B. bassiana ont frein\ue9 l\u2019alimentation et le d\ue9veloppement des larves, r\ue9sultant en une r\ue9duction du nombre de larves, nymphes et adultes, par 65,3; 43,2; et 54,0%, respectivement. Pour une premi\ue8re fois, cette \ue9tude a montr\ue9 que le bio-amor\ue7age des graines du haricot vert avec des bio-inoculants peut augmenter la croissance et la nodulation de P. vulgaris, par cons\ue9quent alt\ue8re son interaction et sa r\ue9ponse \ue0 l\u2019infestation, \ue0 l\u2019alimentation de mineur de feuilles et les dommages sur les plantules trait\ue9es. Ces bio-inoculants, constituent ainsi de grands potentiels agents protecteurs de cultures et pourraient \ueatre utilis\ue9s de fa\ue7on s\ue9curisante pour l\u2019amor\ue7age des graines avant leur semis, si les dommages caus\ue9s sur les feuilles et la perte de rendement associ\ue9e sur le haricot vert sont \ue0 r\ue9duire sans danger pour l\u2019environnement. Des \ue9tudes suppl\ue9mentaires devraient \ueatre men\ue9es pour \ue9lucider les m\ue9canismes impliqu\ue9s dans la promotion de la croissance v\ue9g\ue9tale, la nodulation et la dissuasion de l\u2019alimentation de l\u2019insecte

Influence of temperature on the development, reproduction and longevity of Ceratothripoides claratris (Thysanoptera: Thripidae) on tomatoes

Ceratothripoides claratris (Shumsher) is a serious pest attacking tomatoes in Thailand. Temperature-dependent development of C. claratris was studied at seven constant temperatures, i.e. 22, 25, 27, 30, 34, 35 and 40°C. Pre-adult survivorship was greatest (95%) at 25 and 30°C and shortest at 22°C. Egg-to-adult time decreased within the range of 20 to 30°C and at 34°C it started to increase. The lower thermal threshold for egg-to-adult development was estimated at 16 and 18°C by linear regression and the modified Logan model, respectively. The optimum temperature for egg-to-adult development was estimated at 32-33°C by the modified Logan model. The influence of temperature on reproduction and longevity of C. claratris was determined at 25, 30 and 35 and 40°C. Both inseminated and virgin females failed to reproduce at 40°C. Virgin females produced only male offspring, confirming arrhenotoky. The sex ratio of the offspring of fertilized females was strongly female-biased, except at 25°C. Mean total fecundity per female and mean daily total fecundity per female were highest for both virgin and inseminated females at 30°C. Female longevity was longest at 25°C and shortest at 40°C. Male longevity was longest at 30°C and shortest at 40°C. The net reproductive rate (R0) and intrinsic rate of natural increase (rm) was greatest at 30°C while, mean generation time (G) and the doubling time (f) were highest at 25°C. The finite rate of increase (λ) was fairly constant (1.1-1.5 days) over the three temperatures tested. The pest potential of C. claratris for tropical Asia is discussed

Langzeit-Systemvergleiche in Kenia und Indien: Konventionelle und biologische Erträge aus dem ersten Umstellungsjahr

Organic agriculture is more and more perceived as a promising approach to increase food security in developing countries. However, only few attempts have been made so far to assess agronomic and economic performance of organic agriculture in these^regions in a systematic way. This article reports the first year’s results of two long-term farming systems comparison field trials in Kenya and India. In sub-humid Central Kenya, on a high potential site in Meru South District (Chuka), there were no differences between yields of conventional and organic systems for the first maize and brassica crops. In contrast, organic yields were 14 to 60% lower than conventional yields on a trial site in a medium potential zone in Maragua District (Thika). It is assumed that the organic crops in Chuka could benefit from N and P mobilisation from the soil. In Thika, where N and P were less available, the crop depended on the easily soluble nutrients applied in the conventional treatments. In the semi-arid cotton belt of^Central India, biodynamic, organic, conventional and genetically modified (GM) cotton are compared. Soya and wheat are also part of the crop rotation under study. Biodynamic and organic cotton and wheat yields were 30% lower than conventional and GM yields. Soya yields did not differ between the treatments. It is suggested that yield in organic farming systems in conversion depends on initial inherent soil fertility and crop

Thermal Tolerance of the Coffee Berry Borer Hypothenemus hampei: Predictions of Climate Change Impact on a Tropical Insect Pest

Coffee is predicted to be severely affected by climate change. We determined the thermal tolerance of the coffee berry borer , Hypothenemus hampei, the most devastating pest of coffee worldwide, and make inferences on the possible effects of climate change using climatic data from Colombia, Kenya, Tanzania, and Ethiopia. For this, the effect of eight temperature regimes (15, 20, 23, 25, 27, 30, 33 and 35°C) on the bionomics of H. hampei was studied. Successful egg to adult development occurred between 20–30°C. Using linear regression and a modified Logan model, the lower and upper thresholds for development were estimated at 14.9 and 32°C, respectively. In Kenya and Colombia, the number of pest generations per year was considerably and positively correlated with the warming tolerance. Analysing 32 years of climatic data from Jimma (Ethiopia) revealed that before 1984 it was too cold for H. hampei to complete even one generation per year, but thereafter, because of rising temperatures in the area, 1–2 generations per year/coffee season could be completed. Calculated data on warming tolerance and thermal safety margins of H. hampei for the three East African locations showed considerably high variability compared to the Colombian site. The model indicates that for every 1°C rise in thermal optimum (Topt.), the maximum intrinsic rate of increase (rmax) will increase by an average of 8.5%. The effects of climate change on the further range of H. hampei distribution and possible adaption strategies are discussed. Abstracts in Spanish and French are provided as supplementary material Abstract S1 and Abstract S2

Insect antagonistic bio-inoculants for natural control of leaf-mining insect pests of French beans

Fungal endophytes, specifically, Trichoderma asperellum, Beauveria bassiana and Metarhizium anisopliae; strains M2RT4, S4SU1 and S4ST7, respectively, are known to deter aphid infestation and damage to leguminous crops, but no research exists on their biochemical profiles and effects on French bean (Phaseolus vulgaris) leaf miners. The objective of this study was to assess the ability of these endophytic bio-inoculants to produce extracellular enzymes, as well as determine their impact on French beans seedling emergence and growth, and leaf miner fecundity and pupation. Laboratory and greenhouse experiments were conduct at the International Centre of Insect Physiology and Ecology (ICIPE, Nairobi), and the University of Bonn (Germany). Bio-priming French bean seeds by soaking in fungal suspension containing 108 conidia/ ml for 4 hr positively impacted on seedling vigour. Six weeks after germination, all bio-inoculant treatments improved nodulation by 1.5-1.7 folds, while S4SU1 and M2TR4 improved shoot biomass by ~ 2g. In vitro, spore suspensions of these isolates were highly toxic to leaf miner larvae, often resulting in high mortalities and a suppression of pupation by over 70%. All tested isolates exhibited protease (Index=1.22), lipase (Index=1.32) and cellulase (Index=1.06) activities; with M. anisopliae being the best enzyme secretor when cultured under dark conditions on enzyme-specific substrate for 7-14 days. In vivo B. bassiana-primed seedlings deterred larval feeding and development, resulting in reduced number of larvae, pupae and adults, by 65.3, 43.2 and 54.0%, respectively. For the first time, this study showed that bio-priming French bean seeds with bio-inoculants can boost P. vulgaris growth and nodulation, consequently altering its interaction and response to leaf miner infestation, feeding and damage to treated seedlings. These bioinoculants, thus, hold great potential as crop protection agents and could be safely used for priming seeds prior to planting, if leaf mining damages and associated yield losses in French beans are to be minimised in an environmentally sound manner. Further studies should be undertaken to elucidate the mechanisms involved in plant growth promotion, nodulation and insect feeding deterrence

Seasonal fluctuations of noctuid stemborer egg parasitism in southern Benin with special reference to Sesamia calamistis Hampson (Lepidoptera:Noctuidae) and Telenomus spp (Hymenoptera:Scelionidae) on maize

Published online: 28 Jun 2010Parasitism of noctuid stemborer eggs was assessed in monthly surveys in maize fields in southern Benin, from May 1995 to October 1996, and on alternative hosts, i.e. wild grasses, during the dry season from November 1995 to February 1996. Sesamia calamistis was the most prevalent stemborer species, accounting for 98% of the larvae identified from subsamples reared on ear pieces. Egg batch densities ranged between 0.02-0.15 per plant, with lowest densities found during high rainfall periods. 77% of all egg batches were found to be parasitized The egg parasitoids were the scelionids Telenomus busseolae, T. isis , and the trichogrammatid Lathromeris ovicida , accounting for 55.6, 41.6 and 2.8% of total counts, respectively. Parasitism increased in the course of the cropping season and reached peaks of 92 and 86% during the second growing season of 1995 and 1996, respectively. This coincides with the time when farmers have planted a second crop and during a stage when the plants were most attractive and susceptible to S. calamistis attacks. During the dry season, relatively high parasitism was found on maize and wild grasses in inland valleys, and it was concluded that those habitats play an important role in stabilizing the system for both the pest and its natural enemies. As a result, in the Dahomey Gap, which includes parts of Benin, Togo and Ghana, S. calamistis is usually not of economic importance. Although T. busseolae is ubiquitous in Africa, T. isis was only reported from West Africa, including Cameroon. It is recommended that the geographic range of T. isis should be expanded and include East and Southern Africa, where another host, Busseola fusca , is the most important noctuid stemborer pest on cereals