Seasonal Variations in Populations of Plant-Parasitic Nematodes and Vesicular-Arbuscular Mycorrhizae in Florida Field Corn

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Abstract
Vesicular-arbuscular (VA) mycorrhizal spores and plant-parasitic nematodes were monitored every 26-42 days for 1 yr at 4 depths (15, 30, 45 and 60 cm) in 5 locations in a Florida cornfield. Nine species of plant-parasitic nematodes in 7 genera were identified: Hoplolaimus galeatus, Pratylenchus spp. and Belonolaimus longicaudatus were most common, followed by Meloidogyne incognita and Trichodorus christiei. Fourteen species of VA mycorrhizal fungi in 4 genera were found: the most common species was Gigaspora margarita; Glomus macrocarpus var. macrocarpus, G. clarus and Sclerocystis sinuosa were also found regularly. The highest numbers of plant-parasitic nematodes were recovered in Sept.; lowest numbers were found in April and May. Mycorrhizal spores were most abundant in Aug. and least abundant in May. More spores and nematodes were found in the first 15 cm of soil than at lower depths, but depth distribution varied somewhat in individual species of both types of organisms. Numbers of plant-parasitic nematodes and VA mycorrhizal spores varied greatly at different locations in the field. Most correlations between spore numbers and nematode populations were positive, indicating that most species of VA mycorrhizal fungi coexist on corn with most of the plant-parasitic nematode species recovered in this study.