The Interrelation between Natural Enemies of the Invasive Plant Lepidium draba L., Established in a Natural Pasture in Eastern Romania

Lepidium draba L. (family Brasicaceae), originally from Europe, is a problematic plant in many agricultural ecosystems in Romania. A literature survey revealed that 196 phytophagous organisms are associated with L. draba, and 80 of them were found during field surveys. In Romania Ceutorhynchus cardariae, Psylliodes wrasei, and Aceria drabae are the most promising biological agents available for controlling L. draba. Observations were made in natural pastures by the Department of Iassy in eastern Romania in 2008. The most common invasive species were Xanthium italicum, Xanthium spinosum, Elaeagnus angustifolia, L. draba, Euphorbia cyparissias, and Verbascum phlomoides, which dramatically decrease ecosystem productivity. Here we present results obtained based on field test-plant relationship phytophagy between L. draba L. and P. wrasei Leonardi and Arnold. We studied plants of the Brasicaceae family: L. draba, L. crenatum, Armoracia rusticana, and Barbarea orthoceras. Test plots comprised four L. draba planted 5 cm apart, with two test plants (L. draba, L. crenatum, B. orthoceras, or A. rusticana) planted at one of three planting distances (30 cm, 15 cm, and 5 cm) on each side of the central plants. Each planting distance variant was repeated four times, and for each variant all observations were made on 16 central L. draba plants and 8 of each test plant: L. draba, L. crenatum, B. orthoceras and A. rusticana. A total of 144 plants was studied: 48 central L. draba plants and 96 of each test species. These results do not contradict previous evidence that oligophagous species P. wrasei controls the L. draba. P. wrasei is also a potential biologic control agent for B. orthoceras (American yellowrocket), which is native to North America, including much of Canada and the western United States, as well as parts of Asia.