Submitted to: Pest Management Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/29/2006
Publication Date: 11/1/2006
Citation: Zasada, I.A., Klassen, W., Meyer, S.L., Codello, M., Abdul Baki, A.A. 2006. Velvetbean (mucuna pruriens) extracts: impact on meloidogyne incognita, lycopersicon esculentum and latuca sativa survival. Pest Management Science. 62:1122-1127. Interpretive Summary: Nematodes are microscopic soil worms that cause ten billion dollars in crop losses annually in the United States. Vegetable growers in south Florida face a major problem in that there are no safe and effective means of economically controlling populations of nematodes and weeds during the winter production season. One possible approach to solving this problem is in the development of cover crops to be used as antagonists of nematodes and weeds. Therefore, in this study, scientists exposed plant seeds and a plant-parasitic nematode to extracts from the tropical cover crop velvetbean in laboratory tests, and then monitored seed germination, root and stem growth, and plant-parasitic nematode death. The different parts of the velvetbean plant varied in their toxicity to the tested organisms. For example, only extract from velvetbean leaves reduced seed germination, extract from main roots was the most toxic to plant growth, and extract from leaves was the most toxic to the nematode. This research will be used by scientists developing the use of cover crops as environmentally safe methods of reducing weed and nematode pest numbers in agricultural fields.
Technical Abstract: Crude aqueous extracts (1:15 dry weight plant / volume water) were made from velvetbean leaf blades, petioles, vines, main roots and fine roots, and various concentrations of the extracts were evaluated in vitro for toxicities to different stages of Meloidogyne incognita (Kofoid and White) Chitwood and for suppression of hypocotyl and root growth and inhibition of germination of tomato (Lycopersicon esculentum L.) and lettuce (Lactuca sativa L.). Germination of lettuce and tomato seeds was 41 and 13% compared to the water control, respectively, after exposure to crude extracts from leaf blades. Lettuce root growth was the most sensitive indicator of allelopathic activity of the plant part extracts, with maximum percentage reduction in root growth ranging from 8 to 25% in the crude extract, compared to the water control. Lettuce and tomato root growth was more sensitive to the extract from main roots than to extracts of other plant parts, with lethal concentration (LC50) values of 1.2 and 1.1%, respectively. Meloidogyne incognita egg hatch was less sensitive to extracts from velvetbean than the juvenile (J2) stage. There was no difference among LC50 values of the different extracts from plant parts against the egg stage. After a 48-h exposure J2 survival was between 29 to 56%, compared to the water control, for all crude extracts. Based upon LC50 values the extract from fine roots was the least toxic to J2 (LC50 = 39.9%), and the extract from vines the most toxic (LC50 = 7.8%). The effects of the extracts were nematicidal because LC50 values did not change when the extracts were removed and replaced with water. While in vitro studies provide a valuable starting point in determining the toxicity of velvetbean plant material, the relevance of the data to the effects of velvetbean residues in the soil remains to be clarified further.