TABLE CONTENTS

Development of a Management Strategy for the Meloidogyne
incognita/Cyperus rotundus/C. esculentus Pest Complex
Thomas, S.H. (1), J. Schroeder (1), L. Murray (2), J. Trojan (1), C. Fiore (1) & J. Libbin (3)
(1) Department of Entomology, Plant Pathology and Weed Science, New Mexico State University, Las Cruces,
NM, USA; (2) Department of Statistics, Kansas Sate University, Manhattan, KS, USA; (3) Department of
Agricultural Economics and Agricultural Business, New Mexico State University, Las Cruces, NM, USA.
Pest complexes limit profitable crop production in many of the intensively-managed irrigated
fields in the arid southwestern USA. These persistent interactions plague producers who must
manage limited irrigated acreage in an economically efficient manner without the use of
nonselective biocides like methyl bromide. One complex that threatens the sustainability of
vegetable and cotton production involves Meloidogyne incognita (southern root-knot
nematode) and the perennial weeds Cyperus rotundus (purple nutsedge) and C. esculentus
(yellow nutsedge). These pests do not disseminate readily and are well adapted to a mutually
beneficial coexistence that sustains and enhances the pest complex. Both nutsedges are hosts
of M. incognita and can propagate vegetatively via tubers in which the nematode overwinters
and survives spring application of 1,3-dichloropropene, the main fumigant nematicide
in the region. Vegetative nutsedge growth shows little pathogenic response to nematode
infection, and tuber production is often enhanced. All annual rotation crops that would
compete successfully with these nutsedges are excellent hosts for M. incognita, and therefore
unacceptable. Research utilizing a three-year alfalfa rotation sufficiently suppressed the pest
complex such that chile pepper (Capsicum annuum) yield without 1,3-D fumigation was
twice that recovered following a three-year cotton rotation (Gossypium hirsutum) with
fumigation. Research was conducted to determine if a two-year rotation with a perennial,
nondormant M. incognita-resistant alfalfa (Medicago sativa ‘Mecca II’) effectively
suppresses the pest complex while reducing the irrigation demands of a third year of alfalfa.
Following the two-year alfalfa rotation, 32% and 47% of yellow and purple nutsedge root
systems, respectively, showed galling by M. incognita 26 days after chile was planted,
indicating inadequate suppression of the pest complex compared to that achieved with the
three-year rotation. Economic return, efficient water use and effective suppression of the
root-knot nematode/nutsedge pest complex must all be considered when choosing rotation
schemes.
5 th International Congress of Nematology, 2008 319