2012 Annual Report
Three exploratory surveys were conducted in northern Argentina to search for plants of alligator weed infected with the rust pathogen and damaged by miner flies. Alligator weed was found in 17 out of 24 sites, the rust was not found, and the fly was found in three sites. A total of 200 stems of alligator weed were transplanted from the field into tubes, covered with plastic bags and transported to the laboratory for cultivation. Stems and leaves with mines were checked for insects and reared in chambers. Biological observations were recorded. From the 200 stems, 150 had galleries of the fly, and 56 pupae were obtained in the laboratory from which 35 adults of the fly (19 males, 16 females) and 6 parasiotid wasps (17.14 %) emerged. Preliminary host specificity tests of the fly revealed a high degree of specificity. Galleries, pupae and adults were only recorded on alligator weed stems. A different fly was found in 5 out of 17 alligator weed sites. Host specificity tests are needed. For populations with unknown cytogenetical characterizations, pieces of stems were taken to the laboratory and then encouraged to root in a fertilized watery solution or sand-peat mix substrate (70:30). Once roots were ready they were treated following standard cytogenetical procedures to count chromosomes. Preliminary results showed that alligator weed from one site in NW Argentina is a tetraploid (2x= ca. 66), but more studies are needed since samples studied showed diffuse chromosomes. If tetraploidy is confirmed, it would be the first record of this cytotype in such latitudes. Further analyses for the remaining sites are still pending because roots obtained were too tiny and no chromosomes were detected yet.