Environmental Entomology (1985) 14, 433-436

Richard D. Goeden and Donald W. Ricker (1985)
Seasonal asynchrony of Italian thistle, Carduus pycnocephalus, and the weevil, Rhinocyllus conicus (Coleoptera: Curculionidae), introduced for biological control in southern California
Environmental Entomology 14 (4), 433-436
Abstract: Thirty Italian thistle (Carduus pycnocephalus L.) plants produced a total of 7,735 (mean, 258) flower heads, which potentially contained ca. 25,000 seeds, from mid-April to late August 1980, at See Canyon, San Luis Obispo County, Calif. Rhinocyllus conicus Froelich larvae directly and indirectly caused an estimated 55% seed loss in these heads, but still allowed production of 11,410 seeds, mainly after oviposition by the univoltine weevils ended in late June. Larval mortality of 45%, mostly in early instars, was due to intraspecific competition in flower heads. This competition was of the scramble type. Negligible interspecific competition in heads resulted from lepidopterous larvae.
(The abstract is excluded from the Creative Commons licence and has been copied with permission by the publisher.)

Research topic(s) for pests/diseases/weeds:
biocontrol - natural enemies
Research topic(s) for beneficials or antagonists:
general biology - morphology - evolution

---

Pest and/or beneficial records:

Beneficial	Pest/Disease/Weed	Crop/Product	Country	Quarant.
	Carduus pycnocephalus (weed)		U.S.A. (SW)
Rhinocyllus conicus (weed bioagent)	Carduus pycnocephalus (weed)		U.S.A. (SW)