The evolution of resistance to the Bacillus thuringiensis ( Bt ) toxins by insect pests is a major threat to Bt technology. However, the rate of resistance can be slowed with appropriate integrated insect resistance management (IRM) strategies. Surveys were conducted to identify alternate host species for Maruca vitrata (commonly called the legume pod borer or Maruca ) that could serve as refuges for Pod-Borer Resistant (PBR) cowpea in three West African countries (Ghana, Nigeria, and Burkina Faso). Survey sites included 25 in northern Ghana, 44 in northern Nigeria, and 52 in north-central and southwestern Burkina Faso. Alternate hosts of Maruca identified from plant species belonging to the Fabaceae family that showed signs of Maruca damage on cowpea tissues were collected and dissected. Larvae that were found during these dissections were reared to adult moths in the laboratory then identified to species. The alternate host plants including species of Crotolaria , Sesbania , Tephrosia , and Vigna were the most frequently encountered among sites and locations. Flowering and podding of these plants overlapped with flowering and podding of the nearby (~200 m) cowpea crop. Abundance of these wild hosts and overlapping flowering patterns with the cowpea crop in most locations have the potential to sustain ample numbers of Bt susceptible Maruca that will mate with possible resistant Maruca and deter resistance development. Further quantitative studies, however, are required from each location to determine if actual Maruca production from alternate hosts is sufficient for a PBR IRM strategy. If verified, this approach would be compatible with the high dose/refuge IRM strategy that includes alternate hosts and non- Bt crops as refuges.
Abstract Cowpea [Vigna unguiculata (L) Walp.] is an important staple legume in the diet of many households in sub-Saharan Africa. Its production, however, is negatively impacted by many insect pests including bean pod borer, Maruca vitrata F., which can cause 20–80% yield loss. Several genetically engineered cowpea events that contain a cry1Ab gene from Bacillus thuringiensis (Bt) for resistance against M. vitrata were evaluated in Nigeria, Burkina Faso, and Ghana (West Africa), where cowpea is commonly grown. As part of the regulatory safety package, these efficacy data were developed and evaluated by in-country scientists. The Bt-cowpea lines were planted in confined field trials under Insect-proof netting and artificially infested with up to 500 M. vitrata larvae per plant during bud formation and flowering periods. Bt-cowpea lines provided nearly complete pod and seed protection and in most cases resulted in significantly increased seed yield over non-Bt control lines. An integrated pest management strategy that includes use of Bt-cowpea augmented with minimal insecticide treatment for protection against other insects is recommended to control pod borer to enhance cowpea production. The insect resistance management plan is based on the high-dose refuge strategy where non-Bt-cowpea and natural refuges are expected to provide M. vitrata susceptible to Cry1Ab protein. In addition, there will be a limited release of this product until a two-toxin cowpea pyramid is released. Other than South African genetically engineered crops, Bt-cowpea is the first genetically engineered food crop developed by the public sector and approved for release in sub-Saharan Africa.
The legume pod borer Maruca vitrata Fabricius (Lepidoptera: Crambidae) is a pantropical insect pest of legumes. In West Africa M. vitrata is the most devastating insect pest of cowpea, a food crop providing much-needed, inexpensive protein to farmers and consumers. Various approaches to controlling this pest have been tried, including cultural management, host plant resistance and use of synthetic and botanical pesticides, all with limited success. In this review we present information on the distribution, morphology, molecular characteristics, behavior and host plants of M. vitrata . We give especial attention to innovative management tactics being developed for West Africa, including genetically engineered Bt cowpea, new biopesticides and use of exotic parasitoids. We discuss research needs for enhancing integrated pest management (IPM) for M. vitrata in Africa.
Rapid dissemination of critical and accurate information to low-resource and poorly literate people in crisis situations has long been a challenge. Historically, print media as well as radio and television have served as major delivery channels. With the advent of cellphones, SMS (texting), and the Internet, these digital technologies now afford enhanced opportunities for reaching this poorly literate, low-resource client group quickly and efficiently. Here, we describe a two-step, rapid response approach to the Fall Armyworm ( Spodoptera frugiperda ), an invasive noctuid pest newly causing havoc on maize production in Africa and Asia. First, we developed a science-based, animated video – now being localized further into various languages across Africa and Asia – intended to aid semi-literate, smallholder farmers in identifying and scouting for fall armyworm effectively. Second, we made the animation easily available for (re)distribution in affected areas via the Internet and copying/sharing with Bluetooth®, thereby exponentially increasing the animation's reach across a wide spectrum of diverse languages and literacy levels. In this way, this form of asymmetrical communication hybridizes and combines the educational qualities of print dissemination with the range of radio/television delivery. An urgent need now exists to place the existing mobile ESD FAW animation into as many local languages as needed/possible to improve management of this pest. Such language variants will also increase the usefulness of the FAW animation for governments, intergovernmental institutions, non-government organizations, and civil society groups intent of working with farmers in Africa (and Asia) as it pertains to FAW IPM. The USAID, CIMMYT, IITA, and SAWBO teams will continue to foster awareness around mobile ESD as a FAW resource through each of their respective networks, but we also encourage other research and development organizations to do the same. More broadly, there is also the need to develop and disseminate further SAWBO mobile ESD animations on other aspects of FAW management to assist farmers in their attempts to control this pest. Making sure that target audiences have access to this animation, and any future animations, is undoubtedly a considerable challenge. It will be critical to inform intergovernmental, governmental, and non-governmental organizations, working directly or indirectly with farmers, that this resource exists, such that they can be the direct conduit to its deployment in the field. Thus, this (and any future FAW) animation(s) represent(s) a supporting tool for other organizations to use. It will also require that they develop localized pathways for deployment. However, it is important to note that training local educational deployment agents (e.g., extension agents) in the use of the SAWBO Deployer App allows for a highly effective approach to make SAWBO animations available for deployment with farmers in real time as new animations and language variants become available.
Cowpea (Vigna unguiculata Walp.) is the most economically important legume crop in arid regions of sub-Saharan Africa. Cowpea is grown primarily by subsistence farmers who consume the leaves, pods and grain on farm or sell grain in local markets. Processed cowpea foods such as akara (a deep-fat fried fritter) are popular in the rapidly expanding urban areas. Demand far exceeds production due, in part, to a variety of insect pests including, in particular, the lepidopteran legume pod borer (LPB) Maruca vitrata. Genetically engineered Bt-cowpea, based on cry1Ab (Event 709) and cry2Ab transgenes, is being developed for use in sub-Saharan Africa to address losses from the LBP. Before environmental release of transgenic cowpeas, the Bt Cry proteins they express need to be assessed for potential effects on non-target organisms, particularly arthropods. Presented here is an assessment of the potential effects of those Cry proteins expressed in cowpea for control of LPB. Based on the history of safe use of Bt proteins, as well as the fauna associated with cultivated and wild cowpea in sub-Saharan Africa results indicate negligible effects on non-target organisms.
The purpose of this article is to provide information on the history, accomplishments, and future direction of the Bt brinjal (eggplant) program in Bangladesh, formerly under the Agricultural Biotechnology Support Project II, now the South Asia Eggplant Improvement Partnership (SAEIP). The India-based Maharashtra Hybrid Seed Company (Mahyco) developed an eggplant expressing Cry1Ac (EE-1) for control of the eggplant fruit and shoot borer (EFSB). In a partnership among Mahyco, USAID, Sathguru Management Consultants and Cornell University EE-1 was provided to the Bangladesh Agricultural Research Institute (BARI) who bred it into local varieties. After regulatory approval, four varieties were distributed to 20 farmers who harvested Bt brinjal in 2014. Adoption in subsequent years has increased rapidly so that, in 2018, 27,012 farmers used this technology. This article provides background information on the process leading up to current adoption levels, the level of control of EFSB achieved and the economic benefits of Bt brinjal. Efforts on stewardship, farmer training and communication are discussed. In order to ensure the long-term future of the partnership, we discuss the need to enhance involvement of the private sector in the production and stewardship of Bt eggplant. Bt brinjal is the first genetically engineered crop to be commercially released in Bangladesh, and other GE crops are in the pipeline. Hence, success of the Bt brinjal partnership is likely to affect the future of other GE crops in Bangladesh, as well as other parts of the world where biotechnology is needed for food security and environmental safety.
Advances in biotechnology continue to drive the development of a wide range of insect-protected, herbicide-tolerant, stress-tolerant, and nutritionally enhanced genetically modified (GM) crops, yet societal and public policy considerations may slow their commercialization. Such restrictions may disproportionately affect developing countries, as well as smaller entrepreneurial and public sector initiatives. The 2014 IUPAC International Congress of Pesticide Chemistry (San Francisco, CA, USA; August 2014) included a symposium on "Challenges Associated with Global Adoption of Agricultural Biotechnology" to review current obstacles in promoting GM crops. Challenges identified by symposium presenters included (i) poor public understanding of GM technology and the need for enhanced communication strategies, (ii) nonharmonized and prescriptive regulatory requirements, and (iii) limited experience with regulations and product development within some public sector programs. The need for holistic resistance management programs to enable the most effective use of insect-protected crops was also a point of emphasis. This paper provides details on the symposium discussion and provides background information that can be used in support of further adoption of beneficial GM crops. Overall, it emphasizes that global adoption of modern agricultural biotechnology has not only provided benefits to growers and consumers but has great potential to provide solutions to an increasing global population and diminishing agricultural land. This potential will be realized by continued scientific innovation, harmonized regulatory systems, and broader communication of the benefits of the high-yielding, disease-resistant, and nutritionally enhanced crops attainable through modern biotechnology.
Purdue Improved Crop Storage Bags (PICS) bags are hermetic containers consisting of two inner layers of high-density polyethylene (HDPE) surrounded by an outer woven polypropylene bag. They have proven effective in preventing losses of stored cowpea grain to the cowpea bruchid, Callosobruchus maculatus Fabricius (Coleoptera: Chrysomelidae) and perform well with other dry grains attacked by several species of postharvest pests. We tested PICS bags against the rice weevil, Sitophilus oryzae L. (Coleoptera: Curculionidae), a common stored grain pest. Storing rice weevil infested wheat in PICS bags arrested weevil population growth and preserved the grain well. The air surrounding infested wheat held in PICS bags had lower oxygen and higher carbon dioxide levels compared to the ambient atmosphere. Seed germination declined over time in infested PICS bags, but less so than did grain held in infested woven bags. Low-cost, durable, pesticide-free PICS technology offers an inexpensive, practical and useful way to protect wheat against rice weevil.
We tend to think of the word resistance in terms of evolutionary changes in an insect population that occur in response to repetitive exposures to pesticides or other xenobiotics used to manage insect pests in crops, homes, and gardens, or on livestock or humans (including disease vectors). Resistance can also be defined in broader terms since insects are “resistant” to many naturally occurring abiotic and biotic factors they encounter in their environment. In this chapter, we will outline the concepts associated with pesticide resistance, as well as provide examples of some of the known mechanisms associated with resistance. In addition, we will also discuss the broader context of how we can use emergent “omics” tools, such as genomics, proteomics, and metabolomics, to better understand and discover resistance mechanisms. As RNAi is an emerging potential approach for insect control, we also discuss the potential for resistance in insect populations to RNAi pest control strategies. Finally, we will discuss how we can use this information to develop strategies that minimize the impact of insects on human health, food, and property.
During the 20th century, pesticide use has become integral for current agricultural practices, as has the challenge associated with pesticide resistance. Traditional resistance management plans have often used a "use and discard" approach, changing the chemical to target a different mode of action in the pest species once resistance becomes a problem in the field. An alternative strategy is to identify compounds that confer negative cross-resistance (NCR), where the NCR compound is more toxic to pesticide resistant insects as compared to their pesticide susceptible counterparts. Examples of NCR exist in the literature, however, a systematic approach to discover and use these compounds has been lacking in industrial agriculture. In the following chapter we explore both the limitations and the potential for use of NCR strategies in relation to resistance management.
Arthropods form a major part of the biodiversity in agricultural landscapes. Many species are valued because they provide ecosystem services, including biological control, pollination and decomposition, or because they are of conservation interest. Some arthropods reduce crop yield and quality, and conventional chemical pesticides, biological control agents and genetically engineered (GE) crops are used to control them. A common concern addressed in the ecological risk assessment (ERA) that precedes regulatory approval of these pest control methods is their potential to adversely affect valued non-target arthropods (NTAs). A key concept of ERA is early-tier testing using worst-case exposure conditions in the laboratory and surrogate test species that are most likely to reveal an adverse effect. If no adverse effects are observed in those species at high exposures, confidence of negligible ecological risk from the use of the pest control method is increased. From experience with chemical pesticides and biological control agents, an approach is proposed for selecting test species for early-tier ERA of GE arthropod-resistant crops. Surrogate species should be selected that most closely meet three criteria: (i) Potential sensitivity: species should be the most likely to be sensitive to the arthropod-active compound based on the known spectrum of activity of the active ingredient, its mode of action, and the phylogenetic relatedness of the test and target species; (ii) Relevance: species should be representative of valued taxa or functional groups that are most likely to be exposed to the arthropod-active compound in the field; and (iii) Availability and reliability: suitable life-stages of the test species must be obtainable in sufficient quantity and quality, and validated test protocols must be available that allow consistent detection of adverse effects on ecologically relevant parameters. Our proposed approach ensures that the most suitable species are selected for testing and that the resulting data provide the most rigorous test of the risk hypothesis of no adverse effect in order to increase the quality and efficiency of ERAs for cultivation of GE crops. (C) 2012 Elsevier Ltd. All rights reserved.
Cowpea (Vigna unguiculata spp unguiculata) is adapted to the drier agro-ecological zones of West Africa where it is a major source of dietary protein and widely used as a fodder crop. Improving the productivity of cowpea can enhance food availability and security in West Africa. Insect predation--predominately from the legume pod borer (Maruca vitrata), flower thrips (Megalurothrips sjostedti) and a complex of pod-sucking bugs (e.g., Clavigralla spp)--is a major yield-limiting factor in West African cowpea production. Dramatic increases in yield are shown when M. vitrata is controlled with insecticides. However, availability, costs, and safety considerations limit pesticides as a viable option for boosting cowpea production. Development of Bt-cowpea through genetic modification (GM) to control the legume pod borer is a promising approach to cowpea improvement. Cowpea expressing the lepidopteran-active Cry1Ab protein from Bacillus thuringiensis is being developed as a first generation Bt-cowpea crop for West Africa. Appropriate stewardship of Bt-cowpea to assure its sustainability under West African conditions is critical to its successful development. A first step in this process is an environmental risk assessment to determine the likelihood and magnitude of adverse effects of the Cry1Ab protein on key environmental protection goals in West Africa. Here we describe the results of an expert panel convened in 2009 to develop the problem formulation phase for Bt-cowpea and to address specific issues around gene flow, non-target arthropods, and insect resistance management.