K. V. Seshu Reddy

Reduction of insect pest attack on sorghum and cowpea by intercropping

Two experiments to establish the relationship between insect suppression by intercropping and grain yield in sorghum and cowpea were conducted under field conditions. Treatments consisted of monocrops and intercrops of sorghum and cowpea and an additional pair of monocultures and mixtures protected by insecticides. Intercropping reduced the numbers of stem borer, Chilo partellus in sorghum and thrips, Megalurothrips sjostedti in cowpea. In the monocropped, unprotected sorghum, yield was reduced by 28% compared to the protected monocrop, while reduction in the unprotected intercropped sorghum was 15% compared to the protected intercrop. Similarly, in the unprotected cowpea, monocrop yield was reduced by 94% and intercrop yield was reduced by 51%. Thus, there are yield advantages under conditions where intercropping reduces insect pest density. Intercropping can form a component of an integrated pest management programme.

Reduction of banana weevil populations with pseudostem traps

Abstract One‐week‐old traps made from split banana pseudostems were 1.5–1.7‐fold more attractive to adult banana weevils than 2–3‐week‐old traps. In one experiment, all available pseudostem material was used for trapping, and weekly collecting of weevils over an 11‐month trapping period led to a 50% reduction in weevil catches in one field. In another field with a lower initial weevil density the trapping did not reduce weevil populations. In another experiment, the effect of intensive use of pseudostem traps and daily collecting of trapped weevils was estimated by a mark and recapture method over a period of 6 weeks. Reductions in weevil densities were calculated using a modified version of the Lincoln‐Index. Weevil populations were reduced by 48.5% after 3 weeks and by 62.5% after 6 weeks. Trapping efficiency declined during the experiment and appeared to be related to weevil population densities. This cultural control system may be effective in weevil control in small‐farm situations where labour avail...

A review of the yield losses in graminaceous crops caused by Chilo spp.

A review of the losses caused by various species of Chilo, methodologies adopted for the assessment of losses and information generated on the models for the effect of Chilo species on the yield of graminaceous crops is given.RésuméUne revue sur les pertes occasionnees par les diverses especes du genre Chilo, sur les methodologies pour evaluer les pertes ainsi que sur les informations issues des modeles relatifs a l’effet de Chilo spp. sur le rendement des plantes cerealieres est presentee ici.

Studies on the stem-borer complex of sorghum in Kenya

The distribution and importance of stem-borer species of sorghum in Kenya, viz. Chilo partellus Swinhoe, C. orichalcociliellus Strand, Busseola fusca Fuller, Eldana saccharina Walker and Sesamia calamistis Hampson were studied and discussed. The incidence and period of activity of the stem-borer complex on sorghum indicated that C. partellus, which is a major pest, infested the crop early, while E. saccharina and S. calamistis infested late and persisted in the crop till it was harvested. Preliminary studies on the carryover of stem-borer showed that the larvae of C. partellus and S. calamistis were able to enter diapause in dry sorghum stalks for several months at the end of long and short rain seasons. Some new alternative host plants and parasites and predators affecting different life stages of stem-borers were identified. Preliminary screening of several sorghum lines was carried out for identification and confirmation of resistance to C. partellus and B. fusca, and some sources of resistance were reported.In studies on the distribution, importance, natural enemies and control (by plant resistance) of the stem-borers Chilo partellus (Swinh.), C. orichalcociliellus (Strand), Busseola fusca (Fuller), Eldana saccharina Wlk. and Sesamia calamistis Hmps. on sorghum in Kenya in 1981-1982, C. partellus, which was a major pest, infested the crop early, while E. saccharina and S. calamistis infested late and persisted in the crop until it was harvested. Larvae of C. partellus and S. calamistis were able to enter diapause in dry sorghum stalks for several months at the end of the long and short rainy seasons. Sixteen food-plants for the complex of stem-borers are listed, and notes are provided on some natural enemies. Apanteles sesamiae Cam. parasitised 4 species, Dentichasmias busseolae Heinr. parasitised C. partellus, and predators (on one or more species) were the earwig Diaperasticus erythrocephalus (Ol.), the ant Camponotus rufoglaucus (Jerd.) and the coccinellids Cheilomenes spp. Some sources of plant resistance to Chilo partellus and B. fusca were identified

Insect pest management and socio-economic circumstances of small-scale farmers for food crop production in western kenya: A case study

Sorghum, maize and cowpea serve as staple food for people in Africa and are grown mostly by small-scale farmers. A major constraint on the production of these crops is attack by insect pests among which crop borers are most important, causing 30–80% yield losses. Use of pesticides to control these pests is hazardous and not feasible for the farmers. Alternative strategies for the integrated pest management (IPM) are being developed at the International Centre of Insect Physiology and Ecology (ICIPE) and include the following components: (1) Intercropping and other cultural practices, (2) Plant resistance to insect pests, and (3) Biological control. These IPM components have now been developed to a stage where they can be taken for on-farm trials under farmers’ management for subsequent use by them. But, adoption and diffusion of agricultural innovations requires a prior knowledge of the farming systems and the socio-economic circumstances in which the target farmers operate, and their bearing on the use of innovations. Information on these aspects has therefore been obtained through a survey of farming households in Rendu Bay and Oyugis Divisions in western Kenya during April–August 1986. The survey was conducted jointly with UNEC A and Ministry of Agriculture, Kenya, under a project funded by the Royal Government of Belgium.The survey involved interview with 150 farmers, (75 in each Division. In Kendu Bay 27 were men and 48 women whereas in Oyugis 40 were men and 35 women.) and was based on a questionnaire which comprised six sections. Five sections covered the farmers’ background, farming practices, pest problems and their control, socio-economic conditions, and accessibility/willingness of the farmers to participate in the project. The last section included field observations on the insect pests of sorghum, maize and cowpea.On the basis of the information obtained on above-mentioned aspects, criteria were defined and assigned appropriate weigh tage for selecting 25 farmers in each Division for on-farm trials. The selected farmers included 12 men and 13 women in Kendu Bay while in Oyugis 13 men and 12 women were selected.The measures that need to be taken to counter these limitations and thereby assist the farmers in increasing food production have been recommended.RésuméLe mil, le mais et les pois sont des aliments de base pour les africains et sont cultivés par des petits paysans. La majeure constrainte pour la production de ces cultures est l’attaque courante par les ravageurs, particulièrement les rongeurs qui a eux seuls causent une reduction du rendement entre 30 a 80%. L’utilisation des insecticides est un problème et presque impossible pour les paysans. Des strategies pour la gestion intégrée de la lutte contres les ravageurs (IPM) sont entrain d’être develloppées à l’ICIPE. Ces strategies comprennent: 1) la combinaison des cultures et autres pratiques culturales; 2) la résistance des plantes contre les ravageurs et 3) la lutte biologique. Ces composantes de la gestion intégrée contre les ravageurs furent devellopper jusqu’à un stage ou elles peuvent être mise en application par les paysans. Il est à noter que l’adaptation et la diffusion des découvertes dans le domaine agricole nécessitent à priori des connaissances de base sur les pratiques culturales et les conditions socio-économiques dans lesquelles opèrent les paysans. Cet aspect du problème a été évalué chez les paysans à Kendu Bay et Oyugi à l’ouest du Kenya entre Avril et Août 1986. Le projet fut conjointement conduit par la CEA et le ministère de l’agriculture du Kenya grâce à un financement du Rayaume de Belgique. 150 paysans (75 de chaque village; 27 hommes et 48 femmes de Kendu Bay ainsi que 40 hommes et 35 femmes de Oyugis) ont accepte de repondre aux questions posées pendant cette etude. L’étude comprennait un questionnaire qui avait six sections. Cinq de ces sections couvraient l’historique des paysans, leurs pratiques culturales, les problèmes de ravageurs et leur contrôle, les conditions socio-économiques et l’accord des paysans pour participer au projet La sixième section couvrait les observations faites sur lesravageurs du sorgho, maïs et du pois. Sur la base des informations obtenues grâce aux critères cités ci dessus, une selection de 25 paysans dans chaque village (12 hommes et 13 femmes de Kendu Bay ansi que 13 hommes et 12 femmes de Oyugi) a été faite pour une experimentation sur le terrain. Les mesures qui doivent être prises en consideration pour résoudre ces problèmes et assister les paysans à augmenter leur production alimentaire ont été proposé.

Assessment of On-Farm Yield Losses in Sorghum Due to Insect Pests

In many parts of Africa, field sorghum is attacked by a number of insect pests, notable among them being the sorghum shootfly, a range of lepidopterous stem borers, midge and a complex of head bugs. Studies on yield losses caused by these insects are scanty, yet such information is essential in formulating an IPM strategy for the crop. This study, therefore, describes the various methods of assessing and quantifying the on-farm (pre-harvest) yield losses caused by the above insect pests.

Determination of Economic Injury Level of the Stem Borer, Chilo Partellus (Swinhoe) in Maize, Zea Mays L.

The economic injury level (EIL) of the maize stem borer, Chilo partellus (Swinhoe) was determined by artificially infesting maize (cv. Katumani) plants at three different growth stages; viz, 20,40 and 60 days old plants with varying densities of newly hatched larvae; viz, 2,4,6,8,10 and 12 per plant constituting the borer population. The grain yield data obtained from the infested and the protected plants showed that maximum yield reduction and stalk damage occurred to the 20-day old crop, while there was insignificant larval effect on yields for the 60-day old crop. Regression analyses gave a significant linear equation (y = a + bx) which estimated the yields per plant at different infestation levels and these were used to calculate the economic injury level at each stage. The resultant EIL was 3.2 and 3.9 larvae/ plant for 20- and 40-day old plants, respectively.RésuméLe niveau de dégâts economiques par le boreur du maïs, Chilo partellus (Swinhoe) a été déterminé, après infestation artificielle des plantes de mais (cv. Katumani) âgées de 20, 40, et 60 jours, et en faisant varie la densité de larves nouvelles-nées de 2, 4, 6, 8, 10 et 12 chenilles par plante. Le maximum de réduction de rendement et de dégâts de tiges est apparu sur les plantes âgées de 20 jours. Par contre, il n’y a pas eu d’effet significatif des larves sur le rendement des plantes de 60 jours. L’analyse de regression a donné une equation linéaire (y = a + bx), laquelle a permis d’estimer le rendement par plante différents niveaux d’infestation, et de calculer le niveau de dégâts economiques de chaque stade. Le niveau de dégâts economiques a été de 3,2 et de 3,9 larves/plante pour les plantes âgées de 20 et 40 jours, respectivement.

Insect pests of sorghum in Africa

Several insect pests are associated with the sorghum crop, but essentially a few are considered key pests. These include shootfly, several species of stem borers, sorghum midge and a complex of head bugs. Other insect pests which are occasionally devastating and sporadic include leaf feeders and defoliators (Lepidoptera of various genera, locusts, grasshoppers, aphids, beetles, etc.) and also several species of head worms and head beetles. A list of 101 insect pests of sorghum occurring in Africa is presented.

Relative susceptibility and resistance of some sorghum lines to stem-borers in Western Kenya

Lepidopterous stem-borers are the most serious and widely distributed insect pests of sorghum. Among the several avenues of their control, the use of resistant varieties holds good prospects. In order to identify the sources of resistance to stem-borers (Chilo partellus, Busseola fusca, Eldana saccharina and Sesamia calamistis), a large number of sorghum lines from Kenya, India and Texas, U.S.A. have been screened under a very heavy natural infestation in Western Kenya. Several promising lines with resistance potential have been identified for the stem-borer complex which include: IS 10370, L-2 (TX 2780), IS 10364, IS 1044, S-178, IS 3962, IS 4213, IS 12447, IS 18479, IS 18326, L-l (A&B TX 2756), IS 4405, IS 10711, IS 18676, IS 5613, IS 18517, IS 18323, IS 4881, IS 1151 and IS 18427.

A comparison of rearing methods for the banana weevil, Cosmopolites sordidus (Germar) (Coleoptera: Curculionidae) on its natural host

Simple methods for production of all life stages of the banana weevil on its natural diet, banana rhizome and pseudostem are presented. Their effectiveness, labour demands and applicability for different purposes are discussed. The most effective method for the production of eggs, pupae and adults is the utilization of the rhizome part of suckers, whereas larvae are easier to recover from pseudostem. The hatchability of the eggs produced is high.RésuméDes méthodes simple sont présentées pour la production de tous les stades du charançon du bananier dans son régime naturel, le rhizome et le pseudotronc du bananier. Leur effectivité, dépense en temps et applicabilité pour des objectifs differents sont discutées. La méthode la plus effective pour la production d’oeufs, de pupes et d’adultes est celle utilisant le rhizome des rejets, tandis que les larves sont plus facilement recuperees du pseudotronc. Le pourcentage d’oeufs éclorants est élevé.