Location: Crop Production and Protection2011 Annual Report
1a. Objectives (from AD-416)
Research activity at SABCL is aligned with National Program 304, Crop Protection and Quarantine, whose central challenge is the economical and sustainable management of pests in the U.S. minimizing negative consequences to the environment. Accidental introductions of invasive pests into the U.S. from South America have increased as a result of the international trade. Invasive pests cause major ecological and economical losses and often reduce the quality and value of products, increase the cost of production, damage environmental areas and place native species at risk. In addition, they restrict U.S. products from access to valuable foreign markets. Classical biological control offers the possibility for permanent regional suppression of weeds and insect pests that are a threat to U.S. ecosystems. The objectives are: Obj.1) survey South America to discover, collect, and identify biological control agents of target pests; Obj.2) develop rearing techniques and conduct host range and efficacy trials for potential biocontrol agents to identify the most promising candidates; and Obj.3) facilitate exportation of selected candidates to researchers in the U.S. for field release.
1b. Approach (from AD-416)
SABCL research program Project Plan approved by OSQR in 2010 includes target weeds: Brazilian peppertree (Schinus terebinthifolius), Brazilian waterweed (Egeria densa), water primrose (Ludwigia hexapetala), water lettuce (Pistia stratiotes) and waterhyacinth (Eichhornia crassipes). Insect targets are cactus moth (Cactoblastis cactorum), little fire ant (Wasmannia auropunctata), Harrisia cactus mealybug (Hypogeococcus pungens), imported fire ants (Solenopsis invicta and S. richteri) and glassy-winged sharpshooter (Homalodisca vitripennis). Prior to the collection of their natural enemies, more in depth studies on the biology, ecology, genetics, and/or taxonomy of water primrose, cactus moth and little fire ant are required. These studies are planned as sub-objectives. Target priorities are set by Congressional mandates, as a result of stakeholder workshops, or by hierarchical decision with input from ARS National Program Leaders (NPLs), stakeholders, SABCL director and ARS scientists. Flexibility in this Project is needed to deal with new pest problems in the U.S., with concurrence of NPLs and ARS laboratories. SABCL functions as an overseas arm for several U.S.-based biological control programs on invasive pests of South American origin (except glassy-winged sharpshooter), conducting foreign exploration, collection and evaluation of potential biological control agents to be used in the U.S. Waterhyacinth, Brazilian peppertree, imported fire ants, and glassy-winged sharpshooter were also targets in the previous Project Plan and, except for Brazilian peppertree, Obj.1 and Obj.2 have already been accomplished; current work is limited to collecting and shipping of selected agents (Obj.3). Brazilian waterweed, water primrose, water lettuce, cactus moth, little fire ants and Harrisia cactus mealybug were added by NPLs during the implementation of the previous Project Plan and investigations are in different stages of progress; for the most recently-added targets (cactus moth, little fire ant and Harrisia cactus mealybug), specific approach and procedures for Ob.2 will be determined as soon as natural enemies are discovered, collected and identified. The general impact of work conducted at SABCL includes conservation of non-renewable resources by self-perpetuation of natural enemies; cost-effective suppression of target pests; decreased use of hazardous pesticides; improved environment quality; protection of natural ecosystems from invasive species, favoring biodiversity; sustainable production systems and land use; higher quality food and fiber; higher protection of human health; enhanced scientific understanding of successful biocontrol programs and integrated pest management.
3. Progress Report
Waterhyacinth. The establishment in Florida of a recently-released natural enemy from Argentina failed. Extra samples were collected in northern Argentina with better climate-matching to confirm a higher heat tolerance than those insects already released in Florida. Ecological studies revealed that water hyacinth patches have significant moderating effects on temperature. A new species of natural enemy was discovered but its lab rearing was not possible. Brazilian peppertree. Focused on studying 3 stem galling insects. They were found at high densities and showed high field specificity. Brazilian water weed. Ecological studies on the weed and its fly continued. Natural damage of the new fly was observed in 95% of the plants and 36% of the whorls. Seasonal fly abundance fluctuated widely. A laboratory damage test revealed that 84% of the total length of the plant was damaged affecting the total biomass significantly. The new fly is being described. Water primrose. Morphological and cytological studies continued by culturing plants in controlled greenhouse conditions. Pilosity, leaf form, flower structures, and fruit characteristics were compared. Roots were fixed for chromosome counts. So far most specimens displayed 80 or 16 chromosomes, and a few with different numbers revealed the eventual presence of hybrids. The description of a new species of natural enemy specific to water primrose is in preparation. Water lettuce. Surveys were conducted at 46 sites along the Paraná River basin to assess the number of natural enemies and their geographical and seasonal distribution. Three species of weevils collected were placed on clean plants for oviposition. Rearing methods are being adjusted. Also, adults and nymphs of a new delphacid were collected and lab reared for biological observations. It has proven to be specific to water lettuce. Imported fire ants. Activity reduced to investigate the field host specificity of a virus. Molecular studies were conducted for the presence of the virus in 7 fire ant species from 114 colonies collected in Argentina, Bolivia and Uruguay. Only 2 colonies in Argentina were found positive. Cactus moth. Three genetic variants were field collected as larvae, brought to the lab and adults emerged were kept in cages for their progeny to compare larval performance on native and exotic cacti. Larval survival differed among the hosts. After a survey in 83 sites with 10 cacti species the geographic range was extended further south. A new natural enemy is being described and its lab rearing greatly improved. Little fire ant. Individuals from 26 locations in Argentina were screened for genetic variation for an approach to their phylogeographical history. Sixteen genetic types were found. Molecular evidence showed that this ant was introduced into Israel from a location near SABCL.The radiotolerance is under study to determine an irradiation control dose by sterility of reproductive females. After irradiation, queens were reared with workers for examination of colony growth, which is in progress.A new species of little fire ant was discovered and a new taxonomic key for all species found in Argentina was prepared.
1. Discovery of ten new species for science. During the field explorations for the target pests and their natural enemies in the native land, a number of organisms are usually found and collected for testing as potential candidates for biological control of the invasive target pests in the United States. Prior to the testing process, the accurate taxonomic identification of the natural enemies by classical procedures and/or by more sophisticated molecular methods is a key aspect for the success of the projects. During the extensive field explorations in FY 2011, ARS-SABCL scientists in Argentina discovered 10 species of insects that resulted new for science: one natural enemy of waterhyacinth, one of Brazilian water weed, one of water primrose, one of cactus moth, one of parkinsonia, four of cactus mealybug, and one ant species closely related to the target little fire ant. Some of these new species have been recently described and named by expert taxonomists with the close collaboration of SABCL scientists. The descriptions of the remaining ones are in progress. These accomplishments will greatly increase the chances of success of the respective biological control programs in the United States, and will contribute to the knowledge of the biological diversity in Argentina and globally.
2. Release of a new biological control agent for imported fire ants (IFA). The IFA infest more than 320 million acres in 13 southern states, Puerto Rico and isolated areas of California, Arizona, and New Mexico. They cause an annual expense of $6 billion in damage repair, medical care, and control costs, affecting households, electrical devices, agriculture, wildlife, schools and recreation areas. More than 200,000 people are stung per year and require medical attention. The red imported fire ant affects biodiversity in open habitats and, during the last decade, it has become a global problem. In 1988, the IFA biocontrol project was established at ARS-SABCL in Argentina in close cooperation with ARS scientists at the Center for Medical, Agricultural, and Veterinary Entomology (CMAVE), Gainesville, FL. In late 2010, researchers at CMAVE released a new insect (the parasitoid fly Pseudacteon cultellatus) in several sites of Florida for the biological control of IFA. The agent had been originally found in Argentina and co-developed in the United States and Argentina by CMAVE and SABCL. This new insect released will complement the action of several other species already released from South America for fire ant control in the United States and is intended to decrease the IFA density and damage.
Logarzo, G.A., Casalinuovo, M.A., Piccinali, R., Braun, K. 2010. Geographic host use variabiliy and host range evolutionary dynamics in the phytophagous insect Apagomerella versicolor (Cerambycidae). Oecologia. 165:387-402.