Submitted to: Pest Management Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/20/2009
Publication Date: 1/20/2009
Citation: Nadler-Hassar, T., Shaner, D.L., Nissan, S., Rubin, B., Westra, P. 2009. Are Herbicide Resistant Crops The Answer To Controlling Cascuta?. Pest Management Science. doi 10,1002/PS 1760 Interpretive Summary: Dodder (Cuscuta spp) is a serious parasitic weed of a number of crops. While it is difficult to manage this weed with herbicides, herbicide resistant crops offer a means to try to control dodder. In this research the utility of three different herbicide resistant crops was examined. Glufosinate did not control dodder when applied to glufosinate resistant canola, probably due to the rapid metabolism of the herbicide by the resistant crop. Glyphosate showed potential for controlling dodder, although it will probably require multiple applications. Imazamox showed the most promise due to a combination of activity on dodder as well as the inherent tolerance of the imidazolinone resistant canola to the parasite.
Technical Abstract: Herbicide tolerant crop technology could provide new management strategies for the control of parasitic plants. Three herbicide-tolerant oilseed rape genotypes were used to examine the response of attached C. campestris to glyphosate, imazamox and glufosinate. C. campestris was allowed to establish on the different oilseed rape genotypes before herbicide applications were made. Glufosinate applied to C. campestris attached to glufosinate-tolerant oilseed rape had very little impact on parasite development, while imazamox inhibited C. campestris growth on the imidazolinone-tolerant host. The growth of C. campestris on glyphosate-tolerant host was inhibited by glyphosate, but the parasite recovered and resumed growth within 3 to 4 weeks. The ability of the parasite to recover was related to the quality of interaction between the host and parasite and to the host’s tolerance mechanism. The parasite was less likely to recover when it had low host compatibility indicating that parasite-tolerant crops could be more effective in controlling Cuscuta than herbicide-tolerant crops. Unattached seedlings of C. campestris, C. subinclusa and C. gronovii were exposed in dose response assays to amino acid biosynthesis inhibitors. All three were tolerant to imazamox and glyphosate and sensitive to glufosinate indicating that resistance initially discovered in C. campestris is universal to all Cuscuta species.