Battling insects: Keeping pesky pod borer, bean weevil at bay
Scientists from institutions around the world are developing protective measures to keep crops safe from harmful legume pests.
July 11, 2016 - Author: Cameron Rudolph
Insect infestation, both in the field and after harvest, is a major threat to legume crops. Storage to thwart postharvest losses has been the focus of much research, ranging from testing various types of containers to using motion as a pest deterrent.
A 1991 paper published in Nature by MSU entomology professor James Miller and two graduate students, Martha Quentin and Joseph Spencer, recommended that farmers in sub-Saharan Africa use 50 to 75 percent-filled cylindrical containers to store beans and rotate them one full rotation twice a day. The tumbling prevented bean weevils from boring into the beans, an activity that typically takes 24 hours. Unable to establish a position to bore, the weevils become exhausted and eventually die. The research resulted in lowering bean weevil populations by 97 percent compared to non-movement controls.
It was the first study to examine motion as a pest control. The downside: it wasn’t a feasible option for large-scale farms due to the time and labor. To have a profound impact on large operations, the containers in which crops are stored needed to be evaluated.
Larry Murdock, a distinguished professor of entomology at Purdue University, has been studying pest management in Africa since 1987. He and his team developed a triple-layer plastic bag that protects cowpeas from weevils and other insects with funding from the Legume Innovation Laboratory (LIL), known as the . The layers are individually sealed to form an airtight container.
Researchers also analyzed the bag’s efficacy with other crops, including common bean, maize, pigeon pea and many others. The project, now headed by Dieudonné Baributsa, a research associate professor of entomology at Purdue, also examined the bags ability to prevent mold and preserve seed viability for planting. Results were promising and economic research showed that the bags could be a cost-effective practice for African farmers, moving the project into a third stage.
PICS3, as the program is known today, functions with funding from the Bill and Melinda Gates Foundation. Its mission is to expand food security, market access and cash incomes for farmers through increasing the bag’s implementation in the targeted countries of Burkina Faso, Ethiopia, Ghana, Malawi, Nigeria, Tanzania and Uganda. The goal is to promote a local supply chain by pinpointing manufacturers and distributors. Additionally, with the assistance of international research and extension entities, as well as nongovernmental organizations (NGOs), demonstrations of the bag’s effectiveness are delivered to growers throughout the region.
“Postharvest storage loss of legume crops is a major challenge among smallholder farmers,” Baributsa said. “PICS bags improve income, food security and nutrition by reducing storage loss. By 2015, PICS demonstration activities reached more than 3 million farmers in at least 46,000 villages. About 7 million bags have been sold by more than 15 licensed manufacturers and distributors in Africa and Asia.”
Bringing It All Together
Millions of people around the world rely on cowpeas as a fundamental component of the daily diet. Grown in warm climates such as Africa, South Asia, Central America and South America, they are tolerant to drought and can thrive in poor soil conditions. The rich nutrient profile consists of vitamins, minerals and protein, making cowpeas an important food source for many who can’t afford meat.
The significance of this crop is intensified considering the lack of access to food in many developing countries, so protecting what is produced is crucial. Despite the cowpea’s hardiness, it faces its share of biotic dangers. Pests and diseases can drastically reduce yields when not properly managed. Scientists from U.S. universities and international institutions have been working for decades to mitigate these risks and bring food security to countries in desperate need of a stable food supply.
The legume pod borer is the primary pest of cowpeas in the field, decimating up to 90 percent of some farmers’ yields. Also referred to as Maruca vitrata, the legume pod borer lays eggs on the flowers of legume plants. Larvae feed on the flowers before moving to pods. Without appropriate treatment, larvae can ravish an entire crop in short order. The pod borer can be controlled with insecticides, but they are expensive, not easily accessible to resource-poor farmers, and continuous use results in the advancement of resistance in target pests.
Whether it’s deploying groundbreaking storage bags or biotechnology, equipping developing nations with new infrastructure to fight pests requires capacity building. MSU is committed to offering educational services, consultation and expertise through the World Technology Access Program (WorldTAP).
Trainings on integrated pest management, biotechnology, food safety, intellectual property rights and more are available. Partnering with local institutions in Africa, WorldTAP seeks to connect growers with solutions. For cowpea farmers, the introduction of a disease- and pest-resistant variety could transform their operations.
An international team of scientists from the African Agricultural Technology Foundation (AATF), in collaboration with local researchers in Africa and advanced laboratories, is working to cultivate cowpea varieties that have built-in insect protection through the use of a gene from bacteria (Bt gene). The Bt gene produces a protein that interferes with the digestive system of legume pod borers, but it is specific to pod borers and safe for all other organisms, including beneficial insects, humans and animals.
“We help to introduce practical, sustainable technologies to farmers in Africa who may not otherwise have access to them,” said Denis Kyetere, the executive director of AATF. “Through our partnerships, we can develop and deliver technology such as Bt cowpea that improves crop yields. This is one component of a larger integrated pest management (IPM) plan. MSU and other institutions assist in educating the public about IPM and what it can do to boost productivity.”
Bt cowpea lines have been tested in confined field trials in Burkina Faso, Ghana, Malawi and Nigeria, showing promising results. These varieties are expected to reach smallholder farmers in the next five years. Kyetere was among several who visited MSU in May to attend a conference for the university’s new Alliance for African Partnerships initiative. The Alliance encourages research innovation and collaboration, while expanding MSU’s portfolio of work in Africa.
“Capacity building is extremely important because we want to create sustainable systems in these countries, for pest management and much more,” said Karim Maredia, an MSU entomology professor and program director of WorldTAP. “Training and education are a necessity, and we need to develop and present a range of options to farmers. Biotechnology is just one tool in the toolbox. We are looking to develop a package of strategies that will work long into the future. That means we need experts from
all disciplines to weigh in.”
The LIL backs numerous capacity building projects, including a cowpea pest initiative run by Barry Pittendrigh, an endowed chair in Insect Toxicology at the University of Illinois (UI), who will join the MSU faculty in August as an MSU Foundation Professor in the Department
His research aims to provide growers in Benin, Burkina Faso, Ghana and Niger with tactics that consider cost, human health and environmental impact. Many local producers live on less than $2 per day, so management improvements need to make sense economically. Pittendrigh along with Julia Bello-Bravo — assistant director of the Center for African Studies at UI — and international scientists have generated “IPM-omics.” The project incorporates genomics and geographic information systems technology into integrated pest management.
Pittendrigh’s group has conducted field studies that define pest populations in the region for legume pod borer and other insects. Traditional methods such as spraying neem oil, which has been used as a natural pesticide for hundreds of years, have been explored. Biocontrol tests with a wasp that preys on the legume pod borer are also underway.
“Cowpea is a staple for millions of people and an important source of protein,” Pittendrigh said. “It needs to be protected in ways that are feasible to local farmers. We have worked with Manuele Tamò (insect ecologist at the International Institute of Tropical Agriculture in Benin) on the development and release of biocontrol agents and with our host country scientists on local solutions that can be taught to farmers. But it all comes down to sustainability and making sure that we give a full range of IPM strategies for farmers to choose from.”
Once management plans are created, dissemination can be a substantial challenge that requires a network of organizations. The research team is working with NGOs and Scientific Animations Without Borders (SAWBO), a program cofounded by Bello-Bravo and Pittendrigh. SAWBO conveys scientific and extension information through two-and three-dimensional animations that are accessible in several languages and free of charge. For cell phones and tablets, a free SAWBO app is available. A Nigerian television station has aired some of the animations, prompting Pittendrigh to scout elsewhere for similar opportunities.
“The research is needed to provide scientifically-sound solutions, but it doesn’t mean much if we can’t get it into the hands of the farmers,” Pittendrigh said. “SAWBO helps us connect with both local educators and end users through mobile devices, such as cell phones and in some cases through computers and television. The availability of these devices is increasing significantly in developing countries. The more platforms where SAWBO animations are used, the better chances that it can
positively influence a greater number of people.”