Submitted to: Pecan Grower
Publication Type: Trade Journal
Publication Acceptance Date: 6/25/2004
Publication Date: 7/1/2004
Citation: Nyczepir, A.P., Reilly, C.C., Wood, B.W. 2004. Nematodes, a hidden problem for pecan production. Pecan Grower. 16(1):20-21. Interpretive Summary: Pecan is an important nut crop throughout much of the southern United States with Georgia being ranked as the leading producer. Root-knot nematodes, Meloidogyne spp., are recognized as pests of pecan. In 2002, the pecan root-knot nematode, M. partityla, was first reported on pecan in Georgia and was associated with stressed trees exhibiting dead branches in the upper canopy. Determining the distribution and association of this nematode with mouse-ear disorders in pecan in Georgia needs to be investigated. In 2003-04, a survey was conducted in the major pecan growing regions of Georgia to determine distribution of M. partityla and other root-knot nematodes. Additionally, the relationship between this nematode alone and in combination with a ring nematode on incidence of mouse-ear was investigated. Results indicate that M. partityla was the dominant root-knot nematode on pecan in Georgia and that it was the primary nematode involved with predisposing pecan to mouse-ear disorder. Until a resistant rootstock or nonchemical management strategy is discovered or an effective nematicide is developed, the nematode problem must be managed by manipulating the environment. These data provide useful insights into the occurrence of M. partityla on pecan throughout Georgia=s pecan production areas, its association with mouse-ear development, and management strategy for this nematode pest in pecan.
Technical Abstract: The pecan root knot nematode, Meloidogyne partityla (Mp), has been associated with pecan trees exhibiting above-ground symptoms that included dead branches in the upper canopy, severely stunted growth, and (or) mouse-ear leaf symptoms. In 2003 04, a survey was conducted in the major pecan growing regions of Georgia to determine distribution of Mp and other Meloidogyne spp. Meloidogyne partityla and two unknown Meloidogyne spp. were the only root-knot nematode species found parasitizing pecan. Meloidogyne partityla was found in a greater number of samples and appears to be the dominant root-knot nematode species in pecan. In July 2002, the relationship between Mp alone and in combination with Mesocriconema xenoplax (Mx) on incidence of mouse-ear (ME) was initiated in field microplots. The occurrence of ME symptoms was detected at bud break on foliage in April and May 2003 and 2004, respectively. Trees were rated for ME leaflet deformity and severity. The ME severity index consisted of a 1-to-10 scale, with 1 = no ME leaflet symptoms and 10 = >50% leaf distortion and multiple stunted shoots. Trees growing in Mp-infested soil alone exhibited greater (P < 0.05) ME symptoms than in the uninoculated control plots. No differences in degree of ME severity occurred between Mx infested soil alone and the uninoculated control plots. Until a resistant rootstock or nonchemical management strategy is discovered or an effective nematicide is developed, the nematode problem must be managed by manipulating the environment.