BIOLOGY AND MANAGEMENT OF INVASIVE WEEDS IN THE WESTERN UNITED STATES
Location: Exotic and Invasive Weeds Research
Title: Natural history studies for the preliminary evaluation of a prospective biological control agent of yellow starthistle, Larinus filiformis (Coleoptera: Curculionidae).
| Gultekin, Levent - ATATURK UNIVERSITY |
| Christofaro, Massimo - ENEA C.R. CASACCIA |
| Tronci, Carlo - BIOTECH & BIOCON AGCY |
Submitted to: Environmental Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: June 25, 2008
Publication Date: October 1, 2008
Citation: Gultekin, L., Christofaro, M., Tronci, C., Smith, L. 2008. Natural History Studies for the Preliminary Evaluation of a Prospective Biological Control Agent of yellow starthistle, Larinus filiformis (Coleoptera: Curculionidae).. Environmental Entomology. 37(5): 1185-1199.
Interpretive Summary: Yellow starthistle is an alien weed that has invaded about 20 million acres in the western U.S. It is especially abundant in Pacific western states. The spiny plant interferes with grazing livestock and outdoors recreation, it is fatally poisonous to horses, and it outcompetes desirable vegetation. Six species of insects have been introduced as biological control agents, but they are not providing sufficient control. Recent foreign exploration conducted in the Mediterranean Basin revealed the existence of the weevil, Larinus filiformis. Basic field and laboratory studies show that this insect is abundant on yellow starthistle in Eastern Turkey, that it attacks a high proportion of flowerheads, completely destroying all the seed, and that it probably has a very narrow host range. These results indicate that this species merits further evaluation to determine if it would be a safe and effective biological control agent.
We conducted studies on the life history, behavior and ecology of Larinus filiformis (Coleoptera: Curculionidae) to determine if it is worthy of further evaluation as a classical biological control agent of yellow starthistle, Centaurea solstitialis (Asteraceae: Cardueae). Larinus filiformis occurs in Armenia, Azerbaijan, Turkey and Bulgaria and has been reared only from C. solstitialis. At field sites in eastern Turkey, adults were active from mid May to late July and oviposited in flowerheads of C. solstitialis from mid June to mid July. Developing larvae destroy all the seeds in a flowerhead. The insect has one generation per year in eastern Turkey, and adults hibernate from mid September to mid May. In the spring, before females begin laying eggs, they feed on the immature flower buds of C. solstitialis, causing them to die. The weevil destroyed 25 to 75% of flowerheads at natural field sites in Turkey, depending on the sample date. Preliminary host specificity experiments on adult feeding indicate that the weevil appears to be restricted to a relatively small number of plants within the tribe Cardueae. About 57% of larvae or pupae collected late in the summer were parasitized by hymenopterans (Braconidae, Ichneumonidae and Chalcidoidea), which is an encouraging sign for a prospective biological control agent.