Nadler-Hassar, T., Weed Science Lab, Biological Science and Pest Management, Colorado State University, Fort Collins, CO 80527, United States
Shaner, D.L., Weed Science Lab, Biological Science and Pest Management, Colorado State University, Fort Collins, CO 80527, United States
Nissen, S., Weed Science Lab, Biological Science and Pest Management, Colorado State University, Fort Collins, CO 80527, United States
Westra, P., Weed Science Lab, Biological Science and Pest Management, Colorado State University, Fort Collins, CO 80527, United States
Rubin, B., Weed Science Lab, Biological Science and Pest Management, Colorado State University, Fort Collins, CO 80527, United States

BACKGROUND: Herbicide-resistant crop technology could provide new management strategies for the control of parasitic plants. Three herbicide-resistant oilseed rape (Brassica napus L.) genotypes were used to examine the response of attached Cuscuta campestris Yuncker to glyphosate, imazamox and glufosinate. Cuscata campestris was allowed to establish on all oilseed rape genotypes before herbicides were applied. RESULTS: Unattached seedlings of C. campestris, C. subinclusa Durand & Hilg. and C. gronovii Willd. were resistant to imazamox and glyphosate and sensitive to glufosinate, indicating that resistance initially discovered in C. campestris is universal to all Cuscuta species. Glufosinate applied to C. campestris attached to glufosinate-resistant oilseed rape had little impact on the parasite, while imazamox completely inhibited C. campestris growth on the imidazolinone-resistant host. The growth of C. campestris on glyphosate-resistant host was initially inhibited by glyphosate, but the parasite recovered and resumed growth within 3-4 weeks. CONCLUSION: The ability of C. campestris to recover was related to the quality of interaction between the host and parasite and to the resistance mechanism of the host. The parasite was less likely to recover when it had low compatibility with the host, indicating that parasite-resistant crops coupled with herbicide resistance could be highly effective in controlling Cuscuta. © Published 2009 by John Wiley & Sons, Ltd.