New bacterial extracts found by Agricultural Research Service scientists may offer safe and effective alternatives to chemical fungicides commonly used by peach and pecan growers.

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New Method May Thwart Pecan and Peach Diseases

By Sharon Durham
June 12 , 2008

Natural bacterial extracts may offer some assistance to peach and pecan growers in treating fungal diseases such as brown rot in peaches and pecan scab. Agricultural Research Service (ARS) scientists in Byron, Ga., are using these substances as a safe and effective alternative to chemical fungicides.

ARS entomologist David Shapiro-Ilan and plant pathologist Charles Reilly at the Southeastern Fruit and Tree Nut Research Laboratory in Byron developed these natural pesticides to control pecan and peach diseases. Although bacterial methods for controlling fungi are not new, the ARS bacterial compounds have never been used to control disease in these two commodities.

In 2006, the United States produced just over an estimated one million tons of peaches and 100,500 tons of pecans. Various diseases result in annual losses of more than $3.5 million for peach growers and $13 million for the pecan industry.

In these studies, Shapiro-Ilan and Reilly used compounds obtained from two genera of bacteria, Xenorhabdus and Photorhabdus. They were found to be effective against common pecan and peach disease organisms that cause significant damage. The two scientists tested compounds from a variety of bacterial strains and species to determine which would be most potent.

The results indicated that X. bovienii and P. luminescens (VS) bacterial compounds generally exhibited the greatest suppression of plant pathogens. Applying 6- to 12- percent dilutions of the bacterial compounds achieved 90 to 100 percent suppression of Phytophthora cactorum lesions on pecan leaves. P. cactorum can cause root, collar and crown rots, as well as foliar and fruit infections.

The researchers also used bacterial compound treatments on pecan shoots to control pecan scab disease caused by Fusicladosporium effusum. The treatments reduced spore formation of F. effusum to levels similar to those by chemical fungicides.

Applications for patents on these treatments have been submitted, and partners are being sought to develop the bacterial metabolites for commercial use.

ARS is a scientific research agency of the U.S. Department of Agriculture.