Field assessment in land of origin of host specificity, infestation rate and impact of Ceratapion basicorne a prospective biological control agent of yellow starthistle

Abstract

Yellow starthistle, Centaurea solstitialis (Asteraceae), is an important invasive alien weed in the western United States. Currently established biological control agents attack only the capitula (flowerheads), and are not effectively controlling the plant in much of its range. The geographic center of diversity for the plant appears to be in Turkey, but no agents have been introduced from this country. Ceratapion basicorne (Coleoptera: Apionidae) is common in Central Turkey, attacking 25-100% of yellow starthistle plants. In a field experiment, Ceratapion spp. attacked 90% of yellow starthistle plants and 88% of milk thistle plants (Silybum marianum) but not seven other plant species, including artichoke and safflower. We suspect that a different species of insect attacked milk thistle, but they emerged before the plants were sampled. Laboratory tests showed that C. basicorne does not oviposit in milk thistle. Ceratapion basicorne appears to be more host specific than was suggested by previous studies of a population in Italy (Clement et al. 1989. Ann. Entomol. Soc. Am. 82: 741-747). The insect is gregarious, and the number of larvae per plant was positively correlated to root diameter. The level of damage to individual plants was positively correlated to the proportion of plants attacked, indicating aggregation both among plants and within plants. Field data did not show any impact of the insect on plant size or number of capitula, but germination rate of seeds produced by infested plants was 15% lower than for uninfested plants at two of three sites studied.

Physiological host range of Ceratapion basicorne, a prospective biological control agent of Centaurea solstitialis (Asteraceae)

“…cyanus L., and Cnicus benedictus L., which suggests that it is highly host-speciWc (Alonso-Zarazaga, 1990a;Wanat, 1994;Campobasso et al, 1999). The insect is common on yellow starthistle in Turkey, Greece, and Georgia (Rosenthal et al, 1994;Balciunas, 1998;Uygur et al, 2005) and is widely distributed in Europe and western Asia (Alonso-Zarazaga, 1990a;Wanat, 1994). Overwintering adults become active in the early spring and feed on rosette leaves (Clement et al, 1989).…”

“…However, absence of reports of the development of this insect from these hosts in the Weld (Alonso-Zarazaga, 1990a;Wanat, 1994;Campobasso et al, 1999;Uygur et al, 2005) prompted me to further evaluate its host speciWcity. The purpose of the present study was to determine what non-target plants are susceptible to damage by C. basicorne and to measure the relative amount of damage the insect can cause under no-choice laboratory conditions.…”

Assessing the biological control of yellow starthistle (Centaurea solstitialis L): prospective analysis of the impact of the rosette weevil (Ceratapion basicorne (Illiger))

“…Field observations (Uygur et al , ) and modelling analysis (Gutierrez et al , ) suggest that natural enemies killing whole plants before seed maturation and/or reducing the ability of surviving plants to compensate for feeding damage with reduced seed production are required for successful control (see below). The weevil Ceratapion basicorne (Illiger) (Coleoptera; Brentidae) attacks the rosette stage of YST throughout most of its range in the Mediterranean Basin (Alonso‐Zarazaga, ; Antonini et al , ) and has some of requisite attributes: infestation levels range from 25% to 100% (Uygur et al , ; Smith et al , ) and it is highly host specific (Smith et al , ; Smith, , ; Rector et al , ; Cristofaro et al , ). A release permit application for C. basicorne for North America was submitted to USDA‐APHIS (U.S. Department of Agriculture's Animal and Plant Health Inspection Service) on 26 January 2006 (Smith, ), although approval has not been granted because of concerns about possible risk to safflower crops ( Carthamus tinctorius ) and the ornamental cornflower ( Centaurea cyanus ) that are of Palearctic origin (Hinz et al , ; L. Smith, personal communication).…”

“…Rosenthal et al () reported 50–97% infestation and Smith et al () reported 48–100% infestation in field garden studies, whereas Balciunas and Korotyaev () found an average 58% infestation across 20 sites. Uygur et al () reported that at least 50% of the root crown area was damaged in 63% of YST plants in southern Turkey. The number of larvae per plant was positively correlated with root diameter, with aggregation occurring both among plants and within plants (Balciunas & Korotyaev, ).…”

“…Furthermore, as observed for Larinus minutus on diffuse knapweed (Piper, ), rosette weevil adult feeding on rosette leaves in the spring may cause significant damage. In a field study in Turkey, up to seven C. basicorne larvae were found in some YST roots, reducing viable seed production by 15% (Uygur et al , ). Greenhouse experiments show that an infestation of 4.2 ± 3.0 larvae per plant caused a 23% reduction in the size of well‐watered, fertilized potted plants (Smith, ).…”