Natural Parasitism Influences Biological Control Strategies Against Both Global Invasive Pests Ceratitis capitata (Diptera: Tephritidae) and Drosophila suzukii (Diptera: Drosophilidae), and the Neotropical-Native Pest Anastrepha fraterculus (Diptera: Tephritidae)

Ceratitis capitata (Wiedemann) and Drosophila suzukii (Matsumura) are two severe invasive pests widespread in all Argentinean fruit-producing regions. Both coexist with the Neotropical pest Anastrepha fraterculus (Wiedemann) in northern Argentina. The northwestern region shelters major soft fruit and Citrus producing and exporting industries, which are heavily affected by these dipterans. Eco-friendly strategies are under assessment in Argentina. This study mainly assessed D. suzukii, C. capitata, and A. fraterculus temporal abundance variations and their natural parasitism levels on a 1.5-ha-patch of feral peach trees within a disturbed secondary subtropical rainforest of northwestern Argentina. Fly puparia were mainly collected from the soil under fallen peach. Sampling was performed over three peach fruiting seasons. The most abundant pest species was C. capitata. Drosophila suzukii was only found in the last collecting period, but outnumbered A. fraterculus. Natural parasitism distinctly affected the temporal abundance of these dipterans: it significantly depressed C. capitata abundance in last sampling weeks, it did not substantially affect D. suzukii abundance, but it increased synchronously with the increase in the A. fraterculus abundance. Parasitism on C. capitata was mostly exerted by a combination of both a cosmopolitan pupal and a native larval parasitoid, while A. fraterculus was mainly parasitized by two indigenous larval parasitoids. Only three resident pupal parasitoids were associated with D. suzukii, of which the cosmopolitan Pachycrepoideus vindemiae Rondani (Hymenoptera: Pteromalidae) was the most significant. Data on the resident parasitoid impact are relevant for designing biocontrol strategies in noncrop habitats.

First Record and Distribution of Ganaspis brasiliensis (Hymenoptera: Figitidae: Eucoilinae), a Parasitoid of Drosophila suzukii (Diptera: Drosophilidae) in Argentina

The eucoiline species Ganaspis brasiliensis (von Ihering) (Hymenoptera: Figitidae) is recorded for the first time in Argentina, with confirmation of parasitism of Drosophila suzukii (Matsumura) infesting healthy raspberry fruit (Rubus idaeus L. cv. "Heritage") still on the plant. Drosophila suzukii puparia were recovered from fruit collected in an organic farm in Tafí del Valle, Tucumán, Argentina. One G. brasiliensis specimen was obtained from an isolated D. suzukii puparium. An additional 83 specimens, deposited in the entomological collection of the Museo de la Plata, Argentina, were also identified as G. brasiliensis. This parasitoid species is distributed in four biogeographical provinces of Argentina. The specimens of G. brasiliensis collected in Argentina are assumed to belong to a worldwide distributed and generalist lineage, parasitizing several Drosophila species. A taxonomic key of known Ganaspis species from Argentina is provided.

Detection and identification of a novel 16SrXIII subgroup phytoplasma associated with strawberry red leaf disease in Argentina

Strawberry red leaf phytoplasma was found in strawberry plants from production fields in Lules (Tucumán province) and Bella Vista (Corrientes province), Argentina. Characteristic strawberry red leaf symptoms were stunting, young leaves with yellowing at the edges, mature leaves which curled and were reddish at the abaxial face, flower and fruit deformation and death. The pathogen was detected with phytoplasma-universal primer pairs P1/P7 followed by R16F2n/R16R2 as nested primers in 13 diseased plants. Based on RFLP and sequence analysis of the amplified 16S rRNA gene, the phytoplasma was related to the 16SrXIII group (Mexican periwinkle virescence). In silico the RFLP profile of all the samples analysed revealed the presence of a unique pattern, showing that the novel phytoplasma is different from all the phytoplasmas currently composing the 16SrXIII group. The phylogenetic analysis was consistent with RFLP analysis as the strawberry red leaf phytoplasma was grouped within the 16SrXIII group, but formed a particular cluster. On this basis, the Strawberry red leaf phytoplasma associated with strawberry red leaf disease was assigned to a new subgroup, 16SrXIII-F.

First Report of Macrophomina phaseolina Causing Strawberry Crown and Root Rot in Northwestern Argentina

The winter strawberry (Fragaria ananassa Duch.) industry in subtropical regions is characterized by early-season fruit production, a time when crop value is the highest. This is the case of the northwestern province of Tucuman (27°S), Argentina's largest winter strawberry growing area (2). Collapsed and dying strawberry plants of cv. Camarosa were observed in commercial farms in Tucumán in September 2007 with an incidence of 16%. Crowns and roots of affected plants revealed dark, external and internal browning tissue with several dark, oblong, subepidermal sclerotia. Pieces of necrotic crowns and roots disinfested with 0.6% chloride for 30 s were placed on potato dextrose agar (PDA). After 4 days of incubation at 25°C with constant fluorescent lighting, dark cultures with numerous, dark, oblong sclerotia immersed in the isolation medium were observed. Sclerotia size ranged from 70 to 120 μm in 7-day-old cultures. The isolated fungus was identified as Macrophomina phaseolina (3). Ostiolate pycnidia bearing ellipsoidal, hyaline conidia were rarely observed on the affected host tissue (1). Pathogenicity tests were performed on micropropagated nursery plants grown in sterile potting soil under greenhouse conditions for 3 months. Single-sclerotia culture was grown in PDA at 25°C for 4 days. Then, sterile wooden toothpicks were placed on the medium for seven additional days to allow fungal colonization. Prior to use, toothpicks were autoclaved twice in deionized water and once in V8 juice (4). Four plants of Camarosa, Camino Real, Pajaro, and Chandler cultivars were inoculated by inserting a colonized toothpick into the crown. Sterile toothpicks were inserted into crowns of control plants. All plants were incubated under greenhouse conditions. The experimental setting was a randomized complete design with two replicates per cultivar. Inoculated plants developed wilting in one or more leaves 6 days after inoculation. Most of the inoculated plants (90%) collapsed or died within 2 weeks, while control plants remained healthy during the observation period. The reisolated fungus from affected plants was morphologically and culturally identical to the inoculated isolates. M. phaseolina has been reported in the province of Santa Fe (~32°S) where winters are humid and cold (1), contrasting with Tucumán winters, which are dry and cold, both highly conducive conditions for the development of the disease. To our knowledge, this is the first report of M. phaseolina, an emerging pathogen, considered as a potential threat for northwestern Argentina's strawberry industry, which is recognized as a major source of employment and income in this region. References: (1) C. J. N. Carrera. Ficha Fitopatológica 000867 INTA IMIZA Castelar Bs.As., 1972. (2) D. S. Kirschbaum and J. F. Hancock. HortScience 35:807, 2000. (3) J. Maas. Page 26 in: Compendium of Strawberry Diseases. 2nd ed. J. L. Maas, ed. The American Phytopathological Society, St. Paul, MN, 1998. (4) J. Mertely et al. Plant Dis. 89:434, 2005.