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ARS Home » Crop Production and Protection » Research » Research Project #432249

Research Project: Biological Control of Latin American Weeds and Insects

Location: Crop Production and Protection

2021 Annual Report

The objective of this NACA is to discover, develop, evaluate and ship biological control agents of invasive species. The invasive species of concern threaten agriculture and natural environments anywhere in the world, but the emphasis of the agreement will be on those invasive species that either originated in Latin America or that threaten Latin America. Discovery includes initial discovery of potential biological control agents (arthropods, nematodes and microorganisms) and definition of their taxonomy sufficient for subsequent research, development and regulation. Development includes refinement of methods for monitoring, rearing and otherwise necessary methods for manipulation of the species. Evaluation of the biological control agent makes estimates of its efficacy against the target invasive species and determines specificity (i.e., avoids damage to non-target organisms). Basic information developed on systematics, behavior, bionomics, physiology and other aspects of the biology of target and biological control organisms will be considered relevant to the overall effort.

Staff will travel to sites of native origin of invasive species, collect potential biological control agents and perform other elements of the objectives either at their central facility or at collaborating institutions. Results of biological and other studies will be published in peer reviewed journals to the maximum extent possible. Project plans will be written and reviewed according to the procedures for an ARS laboratory. Reporting will include an annual report written in narrative style to complete requirements for the NACA. In addition, FuEDEI will provide the written materials for an ARS SF-421 annual report including SF-115s of publications and talks.

Progress Report
Waterhyacinth is a floating aquatic plant that invaded USA and causes significant alterations in the structure and biodiversity of invaded ecosystems. Biological control is considered one of the few sustainable ways of controlling this plant. Biocontrol agents, such as the plant hopper Megamelus scutellaris, are affected by climatic factors, or symbiotic associations with different microorganisms –often called endosymbionts-, affecting their establishment and abundance. These Yeast-Like Symbionts (YLS) and bacteria that they host in their digestive system play a fundamental role in the plant hopper’s fitness by complementing their deficient nutrition. We studied how climate could affect endosymbiont abundance and the insect's fitness. We are also conducting studies on diversity of endosymbionts of M. scutellaris, comparing those found in the insect’s native range (Argentina), and its introduced range (USA and South Africa) range. Water primroses are a complex of closely related floating and creeping aquatic plants that have become aggressive invaders in USA, as well as western Europe. Dense stands of water primrose can hamper water draining, water uptake, cause hyper-sedimentation, and are a threat to biodiversity. They are also an agricultural problem in rice production. Given the costs of chemical and mechanical control, and their environmental impact, biological control is considered the best tool to manage water primroses. Insects and pathogens discovered are tested on different species of water primroses and related plants, and later exported to ARS quarantine facilities to continue the tests on plants of interest for the USA. Tawny crazy ant (TCA): The TCA is native to South America and has become an urban and agricultural pest in Central and North America. It is established in southern US, occupying most of Texas and Florida since 2002, causing structural damage in urban areas, while ecological or agricultural damages are still to be assessed. Effective control methods are yet to be found. We are trying to determine the source populations invasive in the US, find natural enemies for its biocontrol, and understand key biological aspects of its invasiveness. Other species of Nylanderia are known to form “species complexes” that comprise two or more sister species that are extremely difficult to tell apart. We are using distribution, morphology, and genetic markers to determine if there are cryptic species. These studies indicate that TCA comprises three distinct genetic groups, which occur in overlapping but distinguishable distributions across Argentina and southern Brazil. Peanut smut: The soil-borne pathogenic fungus Thecaphora frezii is the causal agent of peanut smut, the most damaging and prevalent disease of peanut farming in Argentina. It was first reported in 1995, and by 2012 it was present in the whole country, and has so far been recorded in Bolivia and Brazil too. Given that Argentina is a leading exporter of peanuts and peanut products, there is fear that it will continue to spread to other peanut-producing regions. The fungus develops inside the peanut pods, with damage ranging from abnormal development of the seeds to total losses. As there are no symptoms on the aerial part of the plant, it is difficult to assess the incidence and severity of the disease until the harvest. In 2020 FuEDEI started working in cooperation with the USDA-ARS lab in Stillwater, OK, to study if there are different strains, and their distribution in Argentina. Leaf-cutting ants are characterized by cutting fragments of leaves and flowers and using them as substrate for the cultivation of a fungus on which they feed. Although most known species of LCA act as key components in ecosystems, some species are one of the most important pests in the Neotropics. Currently this project seeks to define the species limits of some economically important LCA species. To do this, new genetic analyses are being carried out with next generation technologies in collaboration with scientists from Universidad de la República, Uruguay, and Arizona State University. Biological Control and Society: How can we improve the success of any management strategy? Both prevention and success ultimately rely on public awareness and perception. This is necessary not only to increase the acceptance and visibility of biological control, but also to show the importance of international collaboration to implement biological control programs. Since 2015, FuEDEI has invested a lot of effort to raise awareness among the scientific, policy-making, and educational community of the threat posed by invasive alien species (IAS), and the benefits of biological control. To achieve this FuEDEI participates in biocontrol courses, workshops, science fairs, outreach talks, and online surveys. The cactus moth, Cactoblastis cactorum, is native to South America and invasive in North America, where it threatens wild and cultivated native Opuntia cacti. A specific parasitoid wasp of CM called Apanteles opuntiarum, is being mass reared in quarantine at Gainesville (FL), and a petition to release this wasp in the US has been filed. A second native parasitoid, Goniozus legneri, is under evaluation in the field in Argentina. Cortaderia selloana (pampas grass) and C. jubata (purple pampas grass) are native to South America. Both species are invasive in Europe, South Africa, Australia, New Zealand, Hawaii and western USA (California, Oregon and Washington). Control and monitoring costs in California are around $82/year. On top of its invasiveness, Pampas grass increases fire fuel loads and are dangerous near homes. Classical biological control (CBC) with host-specific natural enemies from Argentina offers an ecologically sound, cost effective, and sustainable control option as a component of an integrated weed management program. The aim of this project is to find invertebrate and microbial biocontrol agents for controlling invasive Pampas grass in the USA. Huanglongbing (HLB): HLB is regarded as the worst citrus pest in the world. It is a disease produced by a bacteria transmitted by an Asian psyllid that is devastating the citric industry by reducing fruit production, changing the appearance, taste and juice contents of fruits, and eventually killing the trees. Studies aim at controlling the spread of the pathogen by controlling the vector insect with the parasitoid Tamarixia radiata. However, the parasitoid has several ecological variants (haplotypes) that show differences in their capacities to control the Asian psyllid. Parrot’s feather (Myriophyllum aquaticum) is an aquatic macrophyte native to South America. It is invasive in the USA, Canada, South Africa, Australia and many countries in Europe, most likely through the aquatic plant trade. FuEDEI is currently part of a new Parrot’s feather international working group. Research on this invasive plant is not new to FuEDEI. Most of the initial work on the exploratory search for natural enemies was conducted here in the 1970s. The stem-mining weevil Listronotus marginicollis was first collected in Argentina, where preliminary host-specificity tests were carried out. The main biocontrol agents considered are L. marginicollis and a defoliating flea beetle, Lysathia sp., already released into South Africa, where it is effective and has brought parrot’s feather under control in much of that country. Harrisia Cactus Mealybug (HCM): This scale, native to South America, invaded Puerto Rico causing severe damage, and even death, of endemic cacti, including two endangered species. This insect was also found on California cacti several times since 2004, and although it was eradicated each time, it remains a threat to native U.S. cacti, and the succulent ornamental industry of around $41 million. The overall goal of this project is to develop a biological control program against the HCM in Puerto Rico. Two parasitoids from Argentina and Paraguay were mass reared at FuEDEI and exported to the quarantine facility in Puerto Rico. Both parasitoid species attacked the Puerto Rican strain of HCM, and the host range tests in the native range showed that both agents are safe for release.

1. New genus of leaf-cutting ant. Identifying and characterizing pest insects correctly is of major importance to develop adequate management practices. In the particular case of leaf-cutting ants, differences among very similar species could provide valuable information to explore population structure and trace their origin, know their potential natural enemies, and predict the damage they are capable of inflicting. Leaf-cutting ants were collected all over South America and separated into related groups. FuEDEI scientists in collaboration with Brazilian and Texas A&M scientists have described a new genus of leaf-cutting ants that contains three species (two are completely new to science) after studying collections made in Argentina and Brazil. These studies revealed that closely related ant species can separate either with or without changes in the chromosomes. These discoveries have the potential to transform the way scientists regard ant species separation, and ultimately, the management strategies each group requires.

2. Artificially growing the peanut smut pathogen builds knowledge of its life cycle. Peanut smut is the most damaging and prevalent disease of peanut farming in Argentina. Given that Argentina is a leading exporter of peanuts and peanut products, there is fear that it will continue to spread to other peanut-producing regions, including the U.S. In preparedness for this risk, FuEDEI and ARS scientists in Stillwater, OK, tried to determine whether there are multiple strains that attack peanut, the place of origin of the most important strains, and if it also attacks wild peanut species that grow in northern Argentina and Bolivia. This involves molecular studies that demand reliable amounts of DNA, which can only be obtained through reliable artificial growing techniques. This lead to the development of a process to cultivate the pathogen without a living plant. This is an important step that will allow us to study its life cycle and genetics, and obtain good quantities of DNA for analyses. Until now there were no published papers on peanut smut cultivation, and the reports that exist proved to be incomplete and unreliable. This is a major step toward getting to know the pathogen and managing its impact and spread.

3. Social acceptance for biocontrol. FuEDEI has invested a lot of effort to raise awareness among the scientific, policy-making, and educational community of the threat posed by invasive alien species (IAS), and the benefits of biological control. Due to these initiatives, the United Nations Development Programme (UNDP) awarded a grant to a consortium formed by FuEDEI and the National University of Hurlingham (Province of Buenos Aires, Argentina), to support education in biological control and IAS (invasive alien species) in secondary schools. This implies official recognition for FuEDEI as a nationwide leader in biological control, not only among the scientific community, where it was always prestigious, but in educational and administrative media as well. This recognition improves our research capacity by engaging local collaborators, and our standing in administration to navigate the complex permitting processes in Argentina and neighbouring countries.