Location: Fruit and Nut Research2013 Annual Report
1a. Objectives (from AD-416):
Develop improved nematode management strategies based on cultural, biocontrol, and chemical pesticide approaches for suppression of ring and/or root-knot nematodes and related peach and pecan disease complexes, such as Peach Tree Decline and Pecan Replant Disease and elucidate the interactive effects among key nematode pests and pathogenic fungi, and rootstock genotype to improve understanding of host susceptibility to peach tree decline problems, such as Peach Tree Decline Disease.
1b. Approach (from AD-416):
Evaluate cover crop systems for nematode suppression and mode of action identified; investigate efficacy of a new postplant nematicide and lower rates of Telone with selected rootstocks; evaluate Pasteuria penetrans as a biocontrol agent for pecan root-knot nematode; develop new knowledge regarding interactive effects among nematode pests and pathogenic fungi as correlated with peach replant disease; and evaluate advanced Prunus germplasm for resistance to continuous root-knot and ring nematode pressure under field conditions. Resources will support research already taking place on this research 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, new postplant nematicide, alternatives to chemical nematicides, lower rates of Telone II nematicide, and biological agent to reduce nematode populations in soils.
3. Progress Report:
The research outlined in this project contributes to the overall mission of ARS to develop new technology and knowledge in order to solve deciduous tree fruit and nut problems of high national priority. This research addresses selected rotation crops, use of bacteria biocontrol agents, the evaluation of advanced rootstock selections in microplots, and evaluation of interactions between nematodes and/or Armillaria root rot fungus that will result in advanced knowledge and improved pre- and postplant nematode management recommendations and tree survival on PTSL or replant sites. In FY 2013, progress accomplished to date includes: 1) Three tall fescue groundcover, peach tree, and natural weed treatments have been established and nematode data by treatment recorded and compared. Selected herbicides needed to be applied to maintain a predominately tall fescue plot. Due to the extensive drought conditions encountered in FY-12, it was decided to leave the groundcovers in place an additional year to enhance their establishment and nematode suppression; 2) J2 penetration data has been recorded, analyzed, and study completed. Grass and peach root exudates to be used in nematode attraction study need to be reevaluated; 3) Microplots in the Pasteuria penetrans biological control study with the Pecan root-knot nematode are established and database developed; 4) Trees in Movento and Telone plots have been planted. Preplant, pretreatment, and/or postplant nematode and growth data have been recorded and analyzed; 5) Weed treatment (tomato) established in respective plots. Also, nematode population dynamics and above-ground tree growth as related to rootstock treatments have been recorded and analyzed in field microplots to determine superior resistance to continuous ring and root-knot nematode pressure over time; and 6) peach seed is being re-stratified and nematode populations increased to be used in nematode, Armillaria (ARR), and peach rootstock treatments in field microplots.
1. Peach and pecan rootstocks evaluated for managing the pecan root-knot nematode. In Georgia, it is not uncommon for peach growers to interplant pecans within a peach orchard, so that when orchard productivity declined the grower pushes out the peach trees and continue using that site for pecan production. Currently, there are no recommended resistant pecan rootstocks available for managing the pecan root-knot nematode on pecan and its host susceptibility to peach is unknown. Studies were initiated to determine the host susceptibility of selected pecan and peach rootstocks for resistance to the pecan root-knot nematode. Results indicate that all pecan rootstocks supported nematode reproduction and were rated as good hosts, whereas all commercial peach rootstocks were rated as highly resistant to this nematode. These data provide useful insights into the need to further explore the development of IPM management strategies (i.e., resistance & biological control) for control of the Pecan root-knot nematode on pecan and their effect on orchard profitability.
2. Tall fescue grass inhibits root-knot nematode development. In recent years peach growers in the Southeast have been faced with economic hardships which make it difficult to afford the costs associated with fumigation. Finding a nonchemical alternative to preplant chemical control of nematode pests and their mode of action is warranted. A tall fescue grass cultivar Jesup (Max-Q) known to suppress root-knot nematode populations was evaluated to examine how it reduced nematode populations at ARS-Byron, GA and in collaboration with ARS-Beltsville, MD. Results indicate that suppression of root-knot nematodes include a low nematode penetration rate and failure of infective worms to complete the life cycle in this cultivar. This research will be used by scientists and growers who are developing use of Jesup (Max Q) for decreasing economic losses due to certain nematode pests encountered in peach orchards.Nyczepir, A.P., Kluepfel, D.A., Waldrop, V., Wechter, W.P. 2012. Soil solarization and biological control for managing Mesocriconema xenoplax and Short Life in a newly established peach orchard. Plant Disease. 96:1309-1314.