Page Banner

United States Department of Agriculture

Agricultural Research Service

Research Project: Sunflower Genetic Improvement with Genes from Wild Crop Relatives and Domesticated Sunflower

Location: Sunflower Research

Title: Methods for assessing infestations of sunflower stem weevil (Coleoptera: Curculionidae) in sunflower stems

Authors
item Prasifka, Jarrad
item Campbell, James
item Aiken, Robert -
item Bradshaw, Jeffrey -

Submitted to: The Canadian Entomologist
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: August 28, 2013
Publication Date: July 8, 2014
Citation: Prasifka, J.R., Campbell, J.F., Aiken, R.M., Bradshaw, J.D. 2014. Methods for assessing infestations of sunflower stem weevil (Coleoptera: Curculionidae) in sunflower stems. The Canadian Entomologist. 146(4): 465-469.

Interpretive Summary: Sunflower stem weevils reduce sunflower yields by promoting diseases, damaging vascular tissues, and causing lodging of sunflower plants. To measure weevil populations for host plant resistance or insecticide field trials, usually larvae are dissected out of stems, a process that is slow and expensive. Alternative methods to estimate weevil populations include digital radiographs (X-rays) of stem sections or rearing out overwintering stem weevils. When tested, digital X-rays of small stem pieces (15 cm above soil level) explained most of the variation in numbers of weevil larvae from dissected stem samples (50 cm), but required less than one-fifth the time of manual dissection. Using emergence boxes to estimate weevil populations was similarly time-efficient, but may not be easily related to weevils per plant because of parasitism and death of weevil larvae inside the stems. Results suggest for large field trials with sunflower stem weevils, digital X-rays provide much more cost-efficient larval population estimates, increasing researchers’ ability to detect differences among treatments.

Technical Abstract: The sunflower stem weevil, Cylindrocopturus adspersus LeConte (Coleoptera: Curculionidae), reduces sunflower, Helianthus annuus L. (Asteraceae), yields by spreading pathogens, damaging vascular tissues, and promoting lodging of sunflower plants. To assess weevil populations for host plant resistance and insecticide field trials, usually larvae are dissected out of stems for counting, a process that is costly and limits experimental designs. To improve efficiency of sunflower stem weevil sample processing, field-collected sunflower samples were used to evaluate whether digital radiographs (X-rays) of stem sections or population estimates from rearing out overwintering stem weevils are suitable substitutes for dissection of complete stems. Digital X-rays of small stem pieces (15 cm above soil level) split longitudinally were found to explain over 75% of the variation in numbers of weevil larvae from dissected stem samples (50 cm), but required less than one-fifth the time of manual dissection. Use of small emergence boxes to estimate weevil populations was similarly time-efficient, but may not be easily related to weevils per plant because of parasitism and other mortality. Results suggest for large field trials with sunflower stem weevils, digital X-rays permit greater statistical power to detect treatment differences and provide much more cost-efficient larval population estimates.

Last Modified: 10/25/2014
Footer Content Back to Top of Page