Location: Fruit and Nut Research2008 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.
3. Progress Report
This progress falls under National Program (NP) 303, Plant Diseases, Component 4 Biological and Cultural Strategies for Sustainable Disease Management, Problem Statement 4A Biological and Cultural Control Technologies. 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, the 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 Peach Tree Short Life (PTSL) or replant sites. The proposed research project is in accord with two ARS Strategic Program Plans as follows: 1) 126.96.36.199 - Pathogen Interactions with Host Plants and 2) 188.8.131.52 - Plant Disease and Nematode Control. PROGRESS: 1) One and 2-year preplant crop rotation sequences have been established to study the suppression of nematode infestation, thus promoting tree growth on a root-knot nematode infested field site prior to replanting orchard back to peaches. Nematode population densities determined in respective plots; 2) Crude root exudates from rotation grass were extracted and challenged against two root-knot nematode species under laboratory conditions. No results to report at this time, but work is continuing in this area; 3) Soil solarization alone and in combination with the cocktail of biocontrol agents treatment plots have been established. Winter wheat planted in respective plots. Cocktail of biocontrol agents were applied through the irrigation system, and nematode and bacteria soil population dynamics determined throughout year; 4) Three Pasteuria penetrans isolates have been tested under laboratory and greenhouse conditions for attachment to the pecan root-knot nematode, Meloidogyne partityla. Two of the bacteria isolates exhibited 100% attachment to M. partityla J2’s, with one of those isolates exhibiting a mean of >23 endospores per J2. Field microplots to study best P. penetrans isolate were established at ARS-Byron location, but experiment not initiated due to electrical failure and loss of M. partityla test cultures; 5) Pecan tree growth and mouse-ear data collected from field microplots as related to pecan root-knot and ring nematode interaction study; 6) Tree growth and symptomatology data recorded as related to Armillaria root rot fungus-nematode interaction field microplot study; and 7) Peach tree growth & symptomatology data recorded among rootstock treatments with & without continuous root-knot nematode pressure in field microplots. It appears that the continuous weed host is influencing population density of the root-knot nematode over time, but it is too early to determine the influence on test rootstocks.
1. Host Status of Peach Rootstocks to Meloidogyne mayaguensis: Meloidogyne mayaguensis (Mm) was detected in Florida in 2001. Concern with Mm has arisen because of the increased interest to grow peaches in Florida. Evaluating rootstocks for resistance to Mm is important in determining the economic impact this nematode may have on the peach industry. Results indicate that all rootstocks were poor hosts to Mm, with Flordaguard being immune. These data provide useful insights into the use of Nemaguard and Flordaguard on sites infested with Mm. This accomplishment relates to National Program 303 Plant Disease Action Plan, Component 4 Biological and Cultural Strategies for Sustainable Disease, Problem Statement 4A Biological and Cultural Control Technologies.
5. Significant Activities that Support Special Target Populations
Nyczepir, A.P., Rodriguez-Kabana, R. 2007. Preplant biofumigation with sorghum or methyl bromide compared for managing Criconemoides xenoplax in a young peach orchard. Plant Disease. 91:1607-1611.