Submitted to: Plant Disease
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: June 12, 2001
Publication Date: September 1, 2001
Citation: Thomas, S.H., Fuchs, J.M., Handoo, Z.A. 2001. First report of meloidogyne partityla on pecan in new mexico. Plant Disease 85: 1030.
Interpretive Summary: Nematodes are microscopic worms that attack plant roots and cause ten billion dollars of agricultural losses each year in the United States. Root-knot nematodes are important root parasites that seriously damage many economic plants worldwide. A recent agricultural problem is a decline of mature pecan trees in Dona Ana County, New Mexico. The purposes of this swork were to determine the cause and then identify the nematodes determined to cause this decline. A collaboration of ARS and New Mexico State University scientists revealed the presence of numerous small galls and egg masses on feeder roots, with root-knot nematodes that were later identified as Meloidogyne partityla Kleynhans based on anatomical examination. Host range tests revealed that this nematode is limited to members of the hickory and pecan family. This discovery is significant because it is the first report of this nematode from New Mexico, and the second report outside of South Africa and thus is of quarantine interest. This report will serve as a useful guide to researchers in planning future research, revising quarantine strategies, and identifying economically important species.
For several years, mature pecan (Carya illinoinensis (Wangenh.) K. Koch) trees were observed to decline despite normal fertilization and irrigation practices in an orchard in Dona Ana County, New Mexico. Affected trees were growing in sandy soil in two widely separated irrigation terraces and exhibited chlorotic foliage and substantial dieback of branches in the upper canopy. Examination of feeder roots revealed the presence of numerous small galls and egg masses, with root-knot nematode females often visibly protruding from root tissue. Attempts to culture the nematode on tomato were unsuccessful. Females and egg masses were collected from fresh pecan roots and sent to the USDA Nematology Laboratory in Beltsville, MD in October 2000, where specimens were identified as Meloidogyne partityla Kleynhans based on morphological examination. This is the first report of M. partityla from New Mexico, and the second report of this nematode outside of South Africa. Starr et al. first reported M. partityla from pecan in the U.S.A. in 1996, after recovering the nematode from five orchards in Texas. Their host range studies revealed that this species was limited to members of the Juglandaceae, which may explain the inability of the NM population to reproduce on tomato. Additional information is needed regarding distribution of this nematode within pecan-growing regions throughout North America.