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Carduus Thistle Seed Destruction by Rhinocyllus conicus

Published online by Cambridge University Press:  12 June 2017

W. W. Surles  and
L. T. Kok
W. W. Surles
Affiliation:
Fisons Corp., 2 Preston Court, Bedford, MA 01730
L. T. Kok
Affiliation:
Virginia Polytechnic Inst. & State Univ., Blacksburg, VA 24061
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Abstract

The impact of a weevil (Rhinocyllus conicus Froel.) (Coleoptera: Curculionidae) on Carduus thistles in Virginia was evaluated in terms of seed reduction and viability during 1973 and 1974. Musk thistle (Carduus nutans L.) seed production from terminal and first lateral heads was reduced by 10% in 1973 and 75% in 1974 due to larval feeding of R. conicus. The greater seed reduction in 1974 was caused by heavy infestation (45% in 1973, 70% in 1974); there was a five-fold increase in the number of weevil pupation chambers per head over the previous year. Total seed production per plant decreased by 35 to 36% in both years despite increased plant vigor due to better growing conditions in 1974. Larval feeding reduced viability of mature musk thistle seeds. Although individual heads of plumeless thistle (Carduus acanthoides L.) were frequently destroyed by larval feeding, seed production from early heads of this thistle decreased by only 5% in 1973 and 4% in 1974 due to low rates of infestation (9% in 1973, 5% in 1974). Total seed reduction per plant for each of the two years was less than 0.2%. Infested heads of plumeless thistle did not produce sufficient seeds for evaluation of the weevil's impact on seed viability.

Type
Research Article
Information
Weed Science , Volume 26 , Issue 3 , May 1978 , pp. 264 - 269
Copyright
Copyright © 1978 by the Weed Science Society of America 

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References

Literature Cited

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