Abstract

Difficulties in establishing and maintaining legumes were observed on sandy soils (Aeric Haploquets) in northeastern Minnesota. Two field experiments were conducted to determine if nematicide and fungicide applications would increase establishment, yield, and persistence of alfalfa (Medicago sativa L.) and birdsfoot trefoil (Lotus corniculatus L.). In Exp. I, the nematicides phenamiphos [ethyl 4-(methylthi0)-rn-tolyl isopropyl phosphoramidate] at 5.6 kg a.i./ha, aldoxycarb [2 methyl-2(methylsulfonyl)propanal O-methylamino carbonyl)oxime] at 8.9 kg a.i./ha, and carbofuran (2,3-dihydro-2,2-dimethyl-7-benzofuranyl methylcarbamate) at 2.2 kg a.i./ha were applied immediately prior to legume seeding. In the seeding and following year, nematicide treatments increased legume yields and stands compared to the control. Carbofuran and phenamiphos were superior to aldoxycarb. Nematicides did not reduce soil nematode populations compared to the control.

In Exp. 11, carbofuran at 2.2 kg a.i./ha alone or in combination with the fungicides metalaxyl [N-2,6-dimethylphenyl)-N-(methoxyacetyl)alanine methyl ester] at 2.2 kg a.i./ha and benomyl [methyl1-(butylcarbamoyl)-2-benzimidazole carbamate] at 16 kg a.i./ha resulted in significantly greater alfalfa yields and populations than the control, benomyl, metalaxyl or metalaxyl-benomyl treatments. Soil nematode populations were not affected by nematicide application; however, carbofuran and carbofuran-metalaxyl and carbofuranbenomyl mixtures significantly reduced root lesion nematode [>Pratylenchus penetrans (Cobb) Filipj. Schuur-Stekh.] numbers recovered from alfalfa roots. The superiority of the carbofuran-metalaxyl treatment in maintaining alfalfa populations compared to carbofuran or metalaxyl alone suggests a nematode-fungus disease complex may be responsible for poor seedling establishment and yields of alfalfa.

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