2012 Annual Report
1a.Objectives (from AD-416):
Develop improved nematode management strategies based on cultural and biocontrol approaches for suppression of ring and (or) root-knot nematode and related peach disease complexes and elucidate the interactive effects and (or) incidence among key nematode pests, pathogenic fungi, and rootstocks to improve the understanding of host susceptibility associated with peach and pecan tree decline problems, such as Peach Tree Decline and Pecan Replant Disease.
1b.Approach (from AD-416):
Evaluate selected rotation crop for suppression of root-knot nematode as an alternative to fumigation; investigate natural products associated with rotation crop for effect on nematode egg hatch and vermiform-life stage survival; investigate solarization alone and in combination with the application of a cocktail of biocontrol agents for nematode management when delivered through irrigation; characterize the suppressive effects of biocontrol agent towards the Pecan and Peach root-knot nematodes; develop new knowledge regarding interactive effects among nematode pests and (or) pathogenic fungi as associated with peach and (or) pecan replant disease; and evaluate advanced Prunus germplasm for resistance to continuous root-knot nematode pressure under field conditions.
Resources will support research already taking place on this project. This includes development of strategies or approaches to minimize the economic impact of nematodes and other pathogens on peach and pecan. Work involves ground covers, alternatives to chemical nematicides, and biological agents to reduce nematode populations in soils.
FY 2008: One and 2-yr rotation sequences were established to study nematode suppression prior to replanting peach orchard; Grass root exudates were extracted and challenged against root-knot nematode; Soil solarization and biocontrol agent plots were established; Three Pasteuria penetrans isolates were tested for potential attachment to M. partityla; Pecan growth and mouse-ear data collected from pecan root-knot/ ring nematode interaction study; Tree growth as related to Armillaria root rot fungus*nematode interaction field microplot study was recorded; and Peach growth data recorded in treatments with & without continuous root-knot nematode (RKN) pressure in field microplots.
FY 2009: One & 2-yr rotation sequences completed & fumigation established prior to planting new orchard; Root exudates challenged against RKN J2 stage. Results inconclusive. Evaluated grass against 3 root-knot nematodes (RKN) at ARS-Byron & ARS-Beltsville; Soil solarization and/or biocontrol agents on suppression of ring nematode and tree mortality continues. Solarization as good as preplant methyl bromide; P. penetrans isolate for biocontrol of M. partityla initiated at ARS-Byron; Pecan root-knot/ ring nematode interaction study completed & wrote manuscript; Armillaria root rot fungus*nematode interaction study continues; and Nematode populations & tree growth & yield data recorded in continuous RKN pressure study.
FY 2010: One & 2-yr grass rotations, fumigation, and unfumigated plots were replanted to peach. Nematode populations & tree growth recorded; RKN egg hatch & J2 mobility suppressed by root exudate. Greenhouse grass vs. 3 RKN species was completed & results indicate that not all RKN species suppressed; Solarization and/or biocontrol agents on suppression of ring nematode continues. Wheat planted & solarization as good as methyl bromide in promoting tree survival; P. penetrans for biocontrol of M. partityla continues; Armillaria root rot fungus*nematode interaction study results indicate that tree death is greater when both organisms occur together; and Nematode populations, tree growth, & yield recorded in continuous RKN pressure study.
FY 2011: Tree growth in 1-yr & 2-yr grass rotations & fumigated plots were greater vs. unfumigated soil. Yield in grass and fumigated plots were greater than in unfumigated plots; RKN egg hatch & J2 mobility were suppressed by root & shoot exudates at ARS-Beltsville. Wrote manuscript on evaluating grass against 3 RKN species; Solarization, biocontrol agents, and/or wheat on suppression of ring nematode and PTSL mortality completed. Solar-wheat treated soil was as effective as methyl bromide in increasing tree survival from PTSL. Wrote manuscript; P. penetrans for biocontrol of M. partityla continues. Excessive rainfall may compromise study; Armillaria root rot fungus*nematode interaction study results indicate tree growth not substantiating 2010 data; and Tree growth, & yield data in continuous RKN pressure study inconclusive.
FY 2012: The new Project Plan was submitted and accepted for implementation on April 4, 2012; project #6606-22000-014-00D.
Foliar Nickel Application Increases Peach Tree Mortality by Peach Tree Short Life. Certain micronutrients, like nickel (Ni), are beneficial in combating plant diseases caused by fungi, bacteria, or nematodes. The potential for using Ni foliar application to assist in the suppression of ring nematode populations, thereby prolonging tree survival on a PTSL sites, is warranted. ARS researchers at Byron, Georgia, found that PTSL linked tree mortality potentially increases when exposed to foliar Ni compared to untreated control and fumigated treatment trees. These data provide insights into foliar Ni application in peach that triggers an unknown mechanism(s) in the tree that enhances PTSL associated tree death, and may be useful in defining the mode of action responsible for tree death in this disease complex.
Preplant IPM Strategy Developed for Managing Root-Knot Nematode in Peach. Peach growers in the Southeast often find it an economic hardship to apply fumigants to orchard sites. Finding a nonchemical alternative to preplant chemical control of nematode pests is warranted. ARS researchers at Byron, Georgia, and Beltsville, Maryland, evaluated a tall fescue grass cultivar as a preplant rotation for suppressing the Southern root-knot nematode. Trees planted after a 1-yr or 2-year tall fescue grass cover crop and trees planted in fumigated soil are significantly larger than trees in unfumigated soil. This work provides the essential baseline data needed to develop a nonchemical preplant nematode control recommendation that now appears in the 2012 SE Peach, Nectarine, and Plum Pest Management and Culture Guide.
Nyczepir, A.P., Wood, B.W. 2012. Foliar nickel application can increase the incidence of peach tree short life and consequent peach tree mortality. HortScience. 47(2):224-227.