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United States Department of Agriculture

Agricultural Research Service

Research Project: CONTROL OF ARTHROPOD PESTS OF PECAN AND PEACH

Location: Fruit and Nut Research

Title: Testing the potential to suppress pecan disease using byproducts from bacteria

Authors
item Shapiro Ilan, David
item Reilly, Charles
item Hotchkiss, Michael

Submitted to: Pecan Grower
Publication Type: Trade Journal
Publication Acceptance Date: November 9, 2007
Publication Date: February 1, 2008
Citation: Shapiro Ilan, D.I., Reilly, C.C., Hotchkiss, M.W. 2008. Testing the potential to suppress pecan disease using byproducts from bacteria. Pecan Grower. 19(3):20-25.

Interpretive Summary: Certain pecan diseases such as scab and Phytophthora can be severe limiting factors in pecan production. Novel methods to control these diseases are needed. In laboratory experiments, we determined the ability of byproducts (= metabolites) that were derived from certain bacteria to suppress pecan diseases. The metabolites were derived from bacteria associated with insect-killing nematodes. Overall we tested metabolites from seven different species or strains of bacteria for their suppressive abilities to pecan diseases fungal leaf scorch, Phytophthora shuck and kernel rot, and pecan scab, and the peach disease, brown rot. We discovered that the potency of the bacteria’s metabolites varied among the different species and strains. Although all bacterial metabolites showed some potency, metabolites from one bacterium (called Photorhabdus luminescens VS strain) had the highest potency and suppressed all pecan disease organisms in all tests. We also tested activity of the metabolites on pecan leaves, and observed that diluted metabolites could cause disease suppression with little or no phytotoxicity. Finally, we found that the bacteria metabolites could suppress sporulation of scab on detached pecan shoots; reductions in sporulation caused by the metabolites were similar to those following treatment with two chemical fungicides, dodine and fenbuconazole. Based on these preliminary results, further research is warranted to determine the potential for using bacterial metabolites to suppress pecan diseases under field conditions.

Technical Abstract: In laboratory experiments, we determined the ability of byproducts (= metabolites) that were derived from certain bacteria to suppress pecan diseases. The metabolites were derived from bacteria associated with insect-killing nematodes. Overall we tested metabolites from seven different species or strains of bacteria for their suppressive abilities to Glomerella cingulata and Phomopsis sp., Phytophthora cactorum, and pecan scab (Cladosporium caryigenum), and brown rot in peach (Monilinia fructicola). We discovered that the potency of the bacteria’s metabolites varied among the different species and strains. Although all bacterial metabolites showed some potency, metabolites from one bacterium (Photorhabdus luminescens VS strain) had the highest potency and suppressed all pecan disease organisms in all tests. We also tested activity of the metabolites on pecan leaves, and observed that diluted metabolites could cause disease suppression with little or no phytotoxicity. Finally, we found that the bacteria metabolites could suppress sporulation of scab on detached pecan shoots; reductions in sporulation caused by the metabolites were similar to those following treatment with two chemical fungicides, dodine and fenbuconazole; a third chemical, triphenyltin hydroxide had no effect on sporulation. Based on these preliminary results, further research is warranted to determine the potential for using bacterial metabolites to suppress pecan diseases under field conditions.

Last Modified: 7/28/2014