Why Augmentative Biological Control Holds Promise for Advancing Agriculture in Developing Countries - Entomology Today

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Parasitoid wasps in the genus Trichgramma are often used in augmentative biological control efforts to manage crop pests. Here, a female Trichogramma dendroliti wasp lays an egg of its own inside an armyworm egg. (Photo by Victor Fursov, Ph.D., CC BY-SA 4.0, via Wikimedia Commons)

By Anamika Sharma, Ph.D.

Anamika Sharma, Ph.D.

A sustainable agricultural system could make the economies of developing countries more stable and self-dependent, and augmentative biological control provides such an opportunity. The aim of augmentative biological control is to manage a crop pest through inoculation and inundation of biological control agents, or natural enemies of the pest. These can include predator or parasitoid insects or microbial organisms. A focused effort and investment to enhance the commercial production of biocontrol agents can improve the human and institutional capacity of developing countries.

The establishment of augmentative biological control requires extensive dissemination of appropriate information and capacity building. One of the major priorities of the Feed the Future Innovation Lab for Integrated Pest Management—located at Virginia Tech’s Center for International Research, Education, and Development and funded by the U.S. Agency for International Development—is improving the human and institutional capacity of its host countries in Africa and Asia.

Muni Muniappan, Ph.D., director of IPM Innovation Lab, says there is a general misperception among scientists that the production and augmentative release of natural enemies is unfeasible and not cost-effective, especially in developing countries.

“This is because usually the cost of production of natural enemies (parasitoids, predators, and microbials) in the laboratories is compared to the cost of available synthetic chemical pesticides,” he says. “However, the establishment of the production units in developing countries builds the human and institutional capacity of the country, and all the money spent on production and use of the natural enemies remain in the country, which in turn makes the food production sustainable and economical. Moreover, about 80 percent of the amount spent on chemical pesticides in developing countries goes to the developed country that produces the chemical, and only a small amount of money stays in the developing countries applying them.”

Augmentative Biological Control in the Realm of Pest Management

The three major types of biological control are classical, conservation, and augmentative. Classical biological control (also identified as inoculation of an exotic natural enemy) involves importing a natural enemy of a pest to the infested region and working to establish a sustained local population. Conservation biological control focuses on maintaining conditions favorable to native natural enemies. Augmentative biological control involves mass rearing of natural enemies and actively releasing or dispersing them to control a pest.

Each approach has its limitations and strengths. For instance, while classical biological control requires longer implementation periods and provides lasting control of a pest, augmentative approaches are comparatively quicker and can control targeted nuisance organisms (insect pests, diseases, weeds) for an extended period but certainly not permanently.

In Niger, farmers are provided gunny sacks with grains, rice moth (Corcyra cephalonica) larvae, and two pairs of the parasitoid wasp Habrobracon hebetor in them. This low-cost process enables farmers to release the parasitoids easily and economically. A bucket is usually used to avoid the sack getting drenched during the rainy season.

Within augmentative biological control, an inoculative approach uses only living organisms (biocontrol agents), including predators, parasites, and microbials (fungus, bacteria, nematodes, and virus), whereas an inundative approach uses living organisms as well as non-living components extracted from living organisms such as neem products, pyrethrins, and Bacillus thuringiensis. The non-living components that are extracted from living organisms are known as biologically based pesticides and function by inundating the system. Currently, highly potent synthetic biochemical pesticides are also available in the market, such as pyrethroids. Since synthetic biochemical and chemical pesticides also require a repetitive application, therefore they can also be identified as an inundative augmentative approach.

The categorizations for all these different approaches may overlap in different ecosystems and circumstances. For instance, Pediobius foveolatus, an introduced parasitoid of the Mexican bean beetle (Epilachna varivestis) in the northeastern United States, does not overwinter and hence does not provide permanent management. It is released every summer in the crop fields as a source of “inoculative augmentation,” a combination of classical and augmentative forms of biological control.

Augmentative Biological Control in Action

Numerous examples throughout history give evidence to the success, sustainability, and viability of biological control in a variety of ecosystems. For just one example, the papaya mealybug (Paracoccus marginatus), is a native of Mexico and feeds on several crops such as papaya, cassava, and mulberry, causing substantial damage to these crops around the globe. Endoparasitoid wasps Acerophagus papayae, Anagyrus loecki, and Pseudleptomastix mexicana have single-handedly managed this pest wherever they are released, including in Africa and Asia.

Meanwhile, release of the native parasitoid Habrobracon hebetor at the onset of summer in the Sahelian region of Africa, coinciding with the emergence of the pearl millet head miner Helicochilus albipunctella, is an example of inoculative biological control. Malick Niango Ba, Ph.D., principal scientist at the International Crops Research Institute for the Semi-Arid Tropics in Niger, found this approach immensely effective in managing H. albipunctella populations.

“When you have natural enemies that are easy to multiply in mass at a cheap cost, augmentative biological control is easy to implement,” says Ba. “It works well in settings with functional infrastructure and enabling policies (incentives for biological control and reduced use of chemical pesticides). One of the challenges we faced in West Africa was how to pass on the technology to the private sector. We overcame that by working with farmer cooperatives to enable them to produce the natural enemies and sell them to fellow farmers. This requires a lot of capacity building and engagement from farmers.”

Trichogramma is a genus of tiny polyphagous wasps, measuring about 0.3 millimeters in length, and are endoparasitoids of insect eggs. Several species of Trichogramma are employed as biological control agents as part of an inundative approach and have managed key lepidopteran pests of several crops worldwide.

While sharing a success story of inundative approach using Trichogramma, Chandish R. Ballal, Ph.D., former director, of the Indian Council of Agricultural Research’s National Bureau of Agricultural Insect Resources, mentioned that an inundative approach using Trichogramma for management of rice pests in India resulted in substantial savings in plant protection costs and restoration of rice biodiversity.

In Tanzania, a woman collects parasitoids with an aspirator from a locally built, low-cost container.

In Nigher, the Feed the Future Innovation Lab for Integrated Pest Management ensures training of members from different countries in mass-rearing and release of natural enemies.

In Kenya, parasitoid Trichogramma wasps are released via cards containing up to 20,000 eggs. The cards are placed in maize fields to manage fall armyworm (Spodoptera frugiperda).

The parasitoid wasp Habrobracon hebetor is mass-reared in lab cages in Niger for release via augmentative biological control of pests such as the rice moth (Corcyra cephalonica) or the pearl millet head miner Helicochilus albipunctella.

“Rice crop in wetlands or Kole lands of Kerala state in India were earlier subject to as many as six rounds of chemical pesticide sprays during a crop season,” she says, “leading to significant deleterious effects on the ecosystem and biodiversity, as the wetlands are interspersed by a network of canals, besides being home to a large number of migratory birds. Two egg parasitoids, Trichogramma japonicum, and T. chilonis, for managing stem borer and leaf roller infestations were promoted by the local department of agriculture. This intervention was so successful that not a single spray of insecticide was required in rice during the entire season.”

When the effectiveness and benefits of augmentative biological control (both inoculative and inundative) are compared with conventional chemical pesticides, safety and sustainability are always emphasized. Nevertheless, crucial aspects—including efficacy, ease of application, and availability and viability of the commercially available organisms/products—are required to develop an economically viable augmentative biocontrol program. Similar to synthetic chemical pesticides, a successful augmentative biocontrol program requires timely release/application and repetitive use. For the purpose of ease of application, like chemical pesticides, both microbial and botanical biological control agents are currently available in various forms, such as flowable concentrates or wettable powders.

Challenges and Opportunities in Augmentative Biological Control

T. M. Manjunath, Ph.D., who established India’s first commercial insectary, says “mass production, supply, and utilization of parasitoids and predators are beset with several challenges. Being living entities, they have definite life cycles and shelf-life, and their productions require a great deal of pre-planning to match and balance the timely demand, as otherwise the valuable products may go waste.” Based on his long experience, he says, “mass-production and marketing of biological control agents should be treated as a passionate scientific adventure. Although the entire process could be challenging to initiate and function, careful training and promotion could lead to profitable commercial production of biological control agents in developing countries.”

Big challenges often create big opportunities. Commercial production of biocontrol agents has immense growth potential. Collaboration of public and private sectors and involvement of small-scale industries is the key to the successful commercialization of biological control agents in developing countries. Currently, chemical pesticides are the most commonly used method around the world to manage pests because of the rapid results and easy availability; however, they carry a breadth of health and environmental hazards. Moreover, chemical pesticides also need repeated applications similar to inundative biological control agents, and, unlike synthetic chemical methods, the use of natural enemies is compatible with all other pest control methods and does not create resistance in pest populations.

The establishment of production and rearing units of biological control agents in developing countries enable local technicians and scientists to be trained, making institutes and universities of these countries equipped with appropriate skills and facilities. Production of the beneficial fungus Trichoderma spp., which is used as a seed treatment to protect crops from soil-inhabiting fungal pathogens, and mass rearing and releasing Trichogramma spp. for control of pestiferous species of Lepidoptera (for example, Spodoptera spp.,) are examples of some of the IPM Innovation Lab’s most effective capacity-building programs.

Appropriate scaling and pricing as well as active networks of communication among businesses, research institutions, government extension agents, farmer organizations, and farmers can all increase the chances of success of this venture. Augmentative biological control creates opportunities for the local population, small- and large-scale farmers, and industries to work together and harvest monetary benefits, besides human and environmental safety. It is indeed money well spent.

Anamika Sharma, Ph.D., is a research associate at the Feed the Future Innovation Lab for Integrated Pest Management, housed at Virginia Tech’s Center for International Research, Education, and Development. Email: anamika@vt.edu.

All photos courtesy of Anamika Sharma, Ph.D., Feed the Future Innovation Lab for Integrated Pest Management, unless otherwise noted.

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