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Les insectes ravageurs représentent une contrainte majeure à l’augmentation du rendement en culture cotonnière en Afrique de l’Ouest. Les filières cotonnières se sont engagées, à des degrés divers, dans des démarches de gestion intégrée des ravageurs pour réduire l’utilisation des insecticides et limiter en amont les risques sanitaires et environnementaux. Toutefois, un changement fondamental des pratiques, au bénéfice de la stimulation des services de régulation naturelle des ravageurs, s’impose pour mettre au point des systèmes de production encore plus économes en pesticides et plus résilients. Les leviers permettant de stimuler les processus écologiques de régulation naturelle des ravageurs sont multiples et redevables d’actions à différentes échelles, du champ cultivé au territoire, mais nécessitent d’approfondir notre connaissance du système de vie des ravageurs et de leurs ennemis naturels. Ils nécessitent aussi une plus grande prise en compte de la perception et des pratiques des acteurs dans une approche participative de la gestion collective des ressources et des processus d’innovation. À terme, il s’agit de construire une organisation territorialisée d’actions individuelles et collectives de gestion des ravageurs et des services écosystémiques, incluant des dimensions écologiques, économiques et sociales.

Enhancing cotton pest management using plant natural defenses has been described as a promising way to improve the management of crop pests. We here reviewed various studies on cotton growing systems to illustrate how an ancient technique called plant training, which includes plant topping and pruning, may contribute to this goal. Using examples from cotton crops, we show how trained plants can be brought to a state of enhanced defense that causes faster and more robust activation of their defense responses. We revisit the agricultural benefits associated with this technique in cotton crops, with a focus on its potential as a supplementary tool for integrated pest management (IPM). In particular, we examine its role in mediating plant interactions with conspecific neighboring plants, pests and associated natural enemies. We propose a new IPM tool, plant training for induced defense, which involves inducing plant defense through artificial injury. Experimental evidence from various studies shows that cotton training is a promising technique, particularly for smallholders, which can be used as part of an IPM program to significantly reduce insecticide use and to improve productivity in cotton farming. © 2018 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

Crop pests are a major constraint to the intensification of agricultural production in the tropics, with novel issues related to global change (climate, land use, biological invasions, etc.), food security and preservation of natural resources and biodiversity. A research, extension and education network called DIVECOSYS (Diversity of cropping systems and ecologically-based pest management in West Africa) was launched in 2010 to synergize applied research actions in response to growing concerns on the vulnerability of agricultural systems to pest management in West Africa. This scientific network brings together research and academic institutions, with expertise spanning a multidisciplinary perspective from biology and ecology to remote sensing, agronomy and integrated pest management. Its main scientific objective is to explore the potential of biodiversity and ecological processes such as pest regulation, enabling novel ecologically-based models for productive systems, reduction of pesticide use, and adaptation or resilience of farming systems in the face of environmental disruptions. From Northern Senegal to Southern Benin, the research group explores a wide range of ecoregions and socio-ecological contexts, including stakeholders and their objectives, land use and agricultural practices, and management of biodiversity for enhancing biological control. Main challenges to be turned into opportunities include (i) encouraging collaborations amongst researchers from different scientific fields, (ii) fostering interactive research and synergies among research institutions and among countries, and (iii) developing an ecological engineering approach for the design of sustainable agricultural systems for smallholder farmers. [ABSTRACT FROM AUTHOR]

Abstract: In the late 1980s, after a long period during which insecticides were sprayed at preset dates to control cotton (Gossypium hirsutum L.) pests and their damage, some French-speaking countries in sub-Saharan areas decided to disseminate a special form of crop protection approach among smallholders, i.e. targeted staggered control (LEC, for Lutte étagée ciblée). According to this approach, decisions on some insecticide applications were made on the basis of infestation levels or the extent of crop injury caused by major pests: Aphis gossypii Glover aphids, Haritalodes (=Syllepte) derogata F., leaf-eating caterpillars, and more generally Helicoverpa armigera (Hübner), Diparopsis watersi Rothschild, Earias insulana (Boisduval) and Earias biplaga (Walker) bollworms. Polyphagotarsonemus latus (Banks) mites were sometimes included on this list. Today, the calendar-based or conventional program is still widely implemented with some changes in insecticides applied due to the development of pyrethroid resistance in H. armigera. Depending on the country, protection programs based on pest monitoring have been preserved or replaced by programs still using thresholds (staggered or true). In Benin, there are two forms of LEC tailored to two regions delineated according to the extent of damage caused by of bollworms that live inside cotton bolls, i.e. Thaumatotibia (=Cryptophlebia) leucotreta (Meyrick). The logical follow-up to LEC, involving true thresholds, was developed in Mali, Cameroon and, recently, Senegal. Cameroon opted for a sequential plan for individual decision program or LOIC (for Lutte après observation individuelle des chenilles), based on control after sequential sampling of bollworms. A calendar program with additional applications of insecticides based on a particular scouting of H. armigera was developed in Togo. In Ivory Coast, the use of true thresholds is limited to the beginning of the cotton crop cycle whereas in Burkina Faso true thresholds are used after the first two calendar sprayings. The present article describes the diversity of these cotton protection programs, sampling methods and associated intervention thresholds based on pests or injury levels in addition to the advantages and constraints associated with their adoption. [Copyright &y& Elsevier]

Abstract: In sub-Saharan areas of Africa, cotton growers no longer cut the shoot tips from plants (topping), although manual topping was promoted at the start of the 20th century to improve yield and, surprisingly, to reduce pest incidence. In these areas, the bollworms Helicoverpa armigera Hübner, Earias spp., and Diparopsis watersi Rothschild are responsible for the majority of cotton yield losses, and the use of pyrethroids has resulted in resistance in field populations of H. armigera. In the face of these problems and given the scarcity of literature on the effects of topping on pest control, we assessed bollworm infestation levels in 12 trials comparing manual topping and non-topping cotton plots in Mali over a six-year period (2002, 2003, and 2005 to 2008). Topping was performed at the emergence of the 15th sympodial branch or at 10 days after the first flower opening. Our results showed no significant difference in seed cotton yields between topped and non-topped cotton. Bollworm infestations (all species) were always lower on topped cotton and 7 out of 12 trials showed significantly lower infestations on topped cotton. In plots of topped cotton, we recorded an average of 56% fewer H. armigera larvae, 68% fewer Earias spp. larvae, and 71% fewer D. watersi larvae with respectively 5, 4, and 3 out of 12 trials with significant differences in favor of topping and no significant difference in favor of non-topping. To our knowledge, our study is the first to report decreases in D. watersi larval infestation with cotton topping. Further studies are required to understand the mechanisms involved in these effects and to ensure that topping is economically attractive for farmers. [Copyright &y& Elsevier]