Submitted to: Journal of Nematology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: December 9, 1997
Publication Date: N/A
Interpretive Summary: Plant parasitic nematodes, such as root knot and root lesion nematode, damage plants by destroying root tips and affecting root growth, thereby reducing plant yields. Chemical nematicides have been used to control nematodes, but certain of these nematicides are being legislatively withdrawn from use because of hazards to human health and the environment. Certain plants produce chemicals that are toxic to nematodes. We tested the potential of thiarubrine C, a naturally occurring compound in roots of black-eyed Susan, as a nematicide. Thiarubrine C was effective as a nematicide against three types of nematodes under dark coniditions following 12-24 hour exposure times, and it was more toxic under lighted coniditons. Thiarubrine C also greatly reduced plant infection after the nematode was exposed to the compound for only one hour. Thiarubrine C, or compounds modelled after its chemical structure, might be viewed as a natural alternatives to existing nematicides.
Thiarubrine C, a polyacetylenic 1,2-dithiin isolated from the roots of Rudbeckia hirta (Asteraceae), exhibited strong nematicidal activity in in vitro and growth chamber assays. Thiarubrine C was toxic, in the absence of light, to the plant parasitic nematodes Meloidogyne incognita and Pratylenchus penetrans at LD50s of 12.4 ppm and 23.5 ppm, respectively. A minimum exposure time between 12-24 h was the critical period from which nematodes could not recover. Although thiarubrine C is not totally dependent on light for toxicity, activity is enhanced in the presence of light, especially with the free living nematode, Teratorhabditis dentifera. Upon exposure of M. incognita juveniles to 20 ppm thiarubrine C for 1 hour, infectivity of tomato plants was greatly reduced compared to control. Thiarubrine C was also effective in reducing plant infection when mixed with soil 24 h prior to or at planting, unlike other related compounds such has -terthienyl.