Submitted to: Journal of Nematology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/23/2010
Publication Date: 7/1/2010
Citation: Zasada, I.A., Meyer, S.L., Morra, M.J. 2010. Brassicaceous seed meals as soil amendments to suppress the plant-parasitic nematodes Pratylenchus penetrans and Meloidogyne incognita. Journal of Nematology. 41:221-227. Interpretive Summary: Plant-parasitic nematodes are microscopic worms that attack plants and cause ten billion dollars in crop losses annually in the United States. Farmers face an enormous problem because they lack safe and effective ways of reducing the numbers of nematodes in soil. A potential way to control plant-parasitic nematodes may be to apply brassicaceous seed meals to soil. Seed meals are the solid materials remaining after the extraction of oil from seeds produced by plants in Brassicaceae (the mustard family). In this study, two agriculturally destructive species of nematodes were exposed in soil tests to four brassicaceous seed meals. The four seed meals differed in their toxicity to the tested nematodes. In addition, the two nematode species differed in their susceptibility to the different seed meals. These results are significant because they provide guidance in selecting the most effective brassicaceous seed meal for plant-parasitic nematode management. This research will be used by scientists developing the use of brassicaceous seed meals for reducing nematode numbers in agricultural fields.
Technical Abstract: Brassicaceous seed meals are the soil materials remaining after the extraction of oil from seeds; these seed meals contain glucosinolates that degrade to nematotoxic compounds upon incorporation into soil. This study compared the nematode-suppressive ability of four seed meals obtained from Brassica juncea 'Pacific Gold', B. napus 'Dwarf Essex' and 'Sunrise', and Sinapis alba 'IdaGold', against mixed stages of Pratylenchus penetrans and Meloidogyne incognita second-stage juveniles (J2). The brassicaceous seed meals were applied to soil in laboratory assays at rates ranging from 0.5 to 10.0% dry w/w with a nonamended control included. Nematode mortality was assessed after 3 days of exposure and calculated as percentage reduction compared to a nonamended control. Across seed meals, M. incognita J2 were more sensitive to the brassicaceous seed meals compared to mixed stages of P. penetrans. Brassica juncea was the most nematode-suppressive seed meal with rates as low as 0.06% resulting in > 90% suppression of both plant-parasitic nematodes. In general B. napus 'Sunrise' was the least nematode-suppressive seed meal. Intermediate were the seed meals of S. alba and B. napus 'Dwarf Essex'; 90% suppression was achieved at 1.0% and 5.0% S. alba and 0.25% and 2.5% B. napus 'Dwarf Essex', for M. incognita and P. penetrans, respectively. For B. juncea, seed meal glucosinolate-degradation products appeared to be responsible for nematode suppression; deactivated seed meal (wetted and heated at 70 °C for 48 hr) did not result in similar P. penetrans suppression compared to active seed meal. Sinapis alba seed meal particle size also played a role in nematode suppression with ground meal (< 20 mm) resulting in 93% suppression of P. penetrans compared with 37 to 46% suppression by pelletized S. alba seed meal. This study demonstrates that all seed meals are not equally suppressive to nematodes and that care should be taken when selecting a source of brassicaceous seed meal for plant-parasitic nematode management.