BIOLOGICAL CONTROL OF INVASIVE TERRESTRIAL AND RIPARIAN WEEDS IN THE FAR WESTERN U.S. REGION, WITH EMPHASIS ON THISTLES, BROOMS AND CAPE-IVY
Location: Exotic and Invasive Weeds Research
Title: Laboratory and field experimental evaluation of host plant specificity of Aceria solstitialis, a prospective biological control agent of yellow starthistle
| Stoeva, Atanaska - |
| Harizanova, Vili - |
| DE Lillo, Enrico - |
| Massimo, Cristofaro - |
Submitted to: Experimental and Applied Acarology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: September 12, 2011
Publication Date: November 20, 2011
Citation: Stoeva, A., Harizanova, V., De Lillo, E., Massimo, C., Smith, L. 2011. Laboratory and field experimental evaluation of host plant specificity of Aceria solstitialis, a prospective biological control agent of yellow starthistle. Experimental and Applied Acarology. 56(1):43-55 DOI: 10.1007/s10493-011-9497-6.
Interpretive Summary: Yellow starthistle is one of the most important alien invasive weeds in the western United States, infesting 20 million acres. It interferes with land use such as grazing and recreation, displaces native species, and is toxic to horses. It is an alien plant that probably originated from the eastern Mediterranean. Six species of insects that attack the flower heads have been introduced for biological control, but they are not controlling the plant in most of its range. Therefore we have been looking for new agents that attack other parts of the plant. The eriophyid mite, Aceria solstitialis, was discovered in Turkey and has been found only on yellow starthistle. The mite damages plants and can prevent the development of flowers and seeds, which reduces the ability of the plant to reproduce. We conducted a series of preliminary host specificity tests to determine if this agent warrants further evaluation as a prospective biological control agent. Our results indicate that this mite can maintain populations in the field on only two closely related plants, including the target weed, and that it is worthy of more thorough evaluation as a prospective biological control agent.
Yellow starthistle (Centaurea solstitialis) is an invasive annual weed in the western USA that is native to the Mediterranean Region and is a target for classical biological control. Aceria solstitialis is an eriophyid mite that has been found exclusively in association with yellow starthistle in Italy, Greece, Turkey and Bulgaria. The mite feeds on leaf tissue and damages bolting plants, causing stunting, witch's broom and incomplete flower development. A combination of laboratory no-choice and two-way choice experiments and field experiments were conducted to assess host plant specificity of the mite in Bulgaria. Mites showed the highest degree of host specificity in the field and lowest in the no-choice experiments. In the field, highest densities of mites occurred on Ce. solstitialis and bachelor's button (Ce. cyanus), and either no mites or trace numbers occurred on the other test plants: diffuse knapweed (Ce. diffusa), safflower (Carthamus tinctorius) and artichoke (Cynara scolymus). In no-choice experiments, mites persisted on diffuse knapweed, bachelor's button, safflower and artichoke, whereas in two-way choice experiments mites persisted on 25% of artichoke plants and did not persist on safflower. The eight other species of plants that were tested in the laboratory were less suitable for the mite. These results suggest that A. solstitialis is highly specific under natural conditions, and warrants further evaluation as a prospective biological control agent.