Submitted to: Journal of Nematology
Publication Type: Abstract Only
Publication Acceptance Date: 5/7/2009
Publication Date: 12/1/2009
Citation: Nyczepir, A.P., Wood, B.W. 2009. Separate and concomitant effects of Meloidogyne partityla and Mesocriconema xenoplax on pecan [abstracr]. Journal of Nematology. 41:364-365. Interpretive Summary: Pecan is North America’s most valuable native tree-nut, with worldwide cultivation and substantial production in the United States and Mexico. This tree crop is attacked by a wide variety of disease and insect pests that greatly reduce tree productivity if improperly managed. In 2002, the pecan root-knot nematode, Meloidogyne partityla, was found on pecan in the southeastern United States and associated with stressed trees exhibiting dead branches in the upper canopy and/or typical Mouse-ear associated foliar symptoms. A ring nematode, Mesocriconema xenoplax, was also detected in the soil samples. Determining the interactions between M. partityla and M. xenoplax on pecan growth, nematode reproduction, and incidence of mouse-ear needs to be investigated. A 37-month long field microplot study was conducted at ARS Byron, GA to determine the interaction between the ring and pecan root-knot nematode as it relates to nematode reproduction, tree growth and mouse-ear disorders in Desirable pecan. Results indicate that the presence of root-knot nematode in suppressed reproduction of ring nematode in soil. Additionally, the pecan root-knot nematode suppressed tree growth and increased incidence of mouse-ear severity in pecan more than ring nematode. These data provide useful insights into the interactive relationships between two plant parasitic nematodes in pecan disease complexes and the need in developing appropriate root-knot nematode management strategies in pecan.
Technical Abstract: Mouse-ear (ME) of pecan is a nutrient disorder that has increasingly manifested itself in recent years as an orchard “replant” disorder in the southeastern United States. Mouse-ear has been found to be caused by a nickel (Ni) deficiency, with timely foliar application of Ni correcting this disorder. In many of the affected ME orchards sampled in Georgia, Mesocriconema xenoplax occurs in the same soil as Meloidogyne partityla. The interactive effects of M. partityla and M. xenoplax on nematode reproduction as well as growth of ‘Desirable’ pecan were studied in field microplots. Meloidogyne partityla suppressed reproduction of M. xenoplax, whereas the presence of M. xenoplax did not affect the populations of M. partityla second-stage juveniles in soil. Trunk diameter was reduced in the presence of M. partityla alone or in combination with M. xenoplax as compared with the uninoculated control trees 32 months following inoculation. The interaction between the two nematodes was significant for dry root weight 37 months after inoculation. Although the combined nematode treatment (M. partityla + M. xenoplax) caused a greater reduction in root growth than M. xenoplax alone, it was not less than M. partityla alone. Mouse-ear symptom severity in pecan leaves was increased in the presence of M. partityla compared with M. xenoplax and the uninoculated control. Meloidogyne partityla is an economically important pest to the pecan industry in the southeastern United States; however, the economic impact of M. partityla on orchard longevity, yield, and nut quality remains unknown.