Brown rot on peach, Clemson Plant Pathology, Department of Entomology, Soils, & Plant Sciences

Guido Schnabel

Associate Professor, Fruit Pathology

OFFICE: B02 Long Hall

ADDRESS: Dept. of Entomology, Soils, & Plant Sciences, 120 Long Hall, Clemson, SC 29634-0315

TELEPHONE: 864-656-6705

FAX: 864-656-0274

E-MAIL: schnabe@clemson.edu

Research Interest

The goal of this lab is to advance the science of tree fruit pathology in general and to study diseases affecting peach trees and fruit specifically. We are using basic and applied research to answer relevant questions in regard to peach fruit disease management. Areas of interest include but are not restricted to uncovering the molecular basis of fungicide resistance in the brown rot pathogen Monilinia fructicola and developing novel strategies to manage brown rot and Armillaria root rot (caused by Armillaria species) in commercial peach orchards.

For postdoctoral scientists and MS and PhD students, this laboratory offers a unique opportunity to conduct basic and applied research with the goal to address real-world problems. Basic research includes gene discovery, gene expression analysis, PCR, Southern and Northern hybridization, RFLP, AFLP, and gel electrophoresis. Applied research includes the use of fungicides, horticultural practices, biocontrol agents and transgenic rootstocks to reduce disease incidence.

Outreach Highlights

Extension work is primarily focused on peaches with a little bit of strawberries mixed in. An important outlet of disease management recommendations is the Southeastern Peach, Nectarine, and Plum Pest Management Guide (http://www.ent.uga.edu/pubs.htm) and the Southeastern Peach Growers Handbook (http://www.ent.uga.edu/pubs.htm). Furthermore there will be a book coming out soon “The Peach” with a great educational peach disease chapter. We are working with county agents on resistance profiling in order to optimize brown rot management and minimize environmental exposure of pesticides; and with growers to test novel approaches of disease management in their own fields.

Dr. Schnabel's Fruit Pathology Lab

Current lab members
The fruit pathology lab currently consists of one technician (Karen Bryson), two postdoctoral scientists (Drs. Achour Amiri, and Chao-Xi Luo), and two graduate students (Alexis Nagel and Hetal Kalariya).

Specific Research Interests

Armillaria root rot (ARR) causes devastating losses to the South Carolina and Georgia peach industry. It kills mature and sometimes young fruit trees within a few months after infection and is considered the number one cause of premature peach tree decline in the Southeast. Currently we are developing strategies to manage the disease in commercial peach orchards. Specifically we are interested in
- cultural control methods (above ground root collars)
- chemical control methods (trunk injections)
- biotechnological control methods (the development of disease tolerant rootstocks for peach based on gastrodianin antifungal protein (GAFP) expression
Brown rot caused by Monilinia fructicola can be devastating for stone fruit growers especially in wet years when weather conditions are suitable for disease epidemics during preharvest season. The disease is primarily controlled using fungicides, however, the development of fungicide resistance in M. fructicola is becoming a major concern. Benzimidazole resistance is still lingering in many parts of SC and GA and in 2004 our lab reported the presence of M. fructicola populations in GA with reduced sensitivity to demethylation inhibitor (DMI) fungicides. Since then, DMI fungicide resistance has also been reported in OH, NY and SC. Responsible and strategic use of available fungicides is critical for sustained brown rot management. Therefore we are currently:
- developing methods to quickly detect fungicide resistance
- determining resistance profiles in SC and GA peach orchards
- studying the molecular basis of fungicide resistance in M. fructicola

Selected Publications

Luo, C. X, Cox, K. D., Amiri, A. and Schnabel, G. 2008. Occurrence and detection of the DMI resistance-associated, genetic element 'Mona' in Monilinia fructicola. Plant Disease, accepted for publication.

Amiri, A., Scherm, H., Brannen, P. M., and Schnabel, G. 2008. Laboratory evaluation of three rapid, agar-based assays to assess fungicide sensitivity in Monilinia fructicola. Plant Dis. 92:415-420.

Holb, I. J. and G. Schnabel 2008. The benefits of combining elemental sulfur with a DMI fungicide to control Monilinia fructicola isolates resistant to propiconazole. Pest Manag. Sci. 64:156-164.

Luo, C. X. andG. Schnabel 2008. Adaptation to fungicides in Monilinia fructicola isolates with different fungicide resistance phenotypes. Phytopathology 98:230-238.

Luo, C.X. and Schnabel, G. 2008. The cytochrome P450 lanosterol 14a-demethylase gene is a demethylation inhibitor fungicide resistance determinant in Monilinia fructicola field isolates from Georgia. Appl. Environ. Microbiol. 74:359-366.

Schnabel, G., D. R. Layne and I. J. Holb 2007. Micronised and non-micronised sulphur sprays control peach scab equally well with negligible impact on fruit quality. Annals of Applied Biology 150:131-139.

Holb, I. J. and G. Schnabel 2007. Differential effect of triazoles on mycelial growth and disease measurements of Monilinia fructicola isolates with reduced sensitivity to DMI fungicides. Crop Protection 26:753-759.

Cox, D. K., K. P. Bryson, and G. Schnabel 2007. Instability of propiconazole resistance and fitness in Monilinia fructicola. Phytopathology 97:448-453.

Schnabel, G. and J. Mercier 2006. Use of a Muscodor albus pad delivery system for the management of brown rot of peach in shipping cartons. Postharvest Biology and Technology 42:121-123.

Cox, K. D., D. R. Layne, R. Scorza, and G. Schnabel 2006. Gastrodia Anti-Fungal Protein from the orchid Gastrodia elata confers disease resistance to root pathogens in transgenic tobacco. Planta 224:1373-1383.

Schnabel, G., W. Chai, and K. R. Cox. 2005. Identifying and characterizing summer diseases on ‘Babygold’ peach in South Carolina. Plant Health Progress. Doi:10.1094/PHP-2006-0301-01-RS.

Schnabel, G., J. S. Ash, and P. K. Bryson. 2005. Identification and characterization of Armillaria tabescens from the southeastern United States. Mycol. Res. 109:1208-1222.

Holb, I. J. and G. Schnabel. 2005. Effect of fungicide treatments and sanitation practices on brown rot blossom blight incidence, phytotoxicity, and yield for organic sour cherry production. Plant Dis. 89:1164-1170.

Schnabel, G., K. E. Bussey, and P. K. Bryson. 2005. First Report of Armillaria gallica causing Armillaria root rot in daylily in South Carolina. Plant Dis. 89:683, 2005.

Schnabel, G., P. K. Bryson, W. C. Bridges, and P. M. Brannen. 2004. Reduced sensitivity in Monilinia fructicola to propiconazole in Georgia and implications for disease management. Plant Dis. 88:1000-1004.

Schnabel, G. and D. R. Layne., 2004. Comparison of reduced-application and sulfur-based fungicide programs on scab intensity, fruit quality, and cost of disease control on peach. Plant Dis. 88:162-166.

Schnabel, G. and Q. Dai. 2004. Heterologous expression of the 14alpha-demethylase gene from Monilinia fructicola reduces sensitivity to some but not all DMI fungicides. Pestic. Biochem. Physiol. 78:31-38.

Work hard and stay fit at Clemson University

Contact me if (i) you live in or near Clemson SC, (ii) you are a competitive table tennis player, and (iii) you are looking for training partners: schnabe@clemson.edu

Key words: ping pong, ping-pong, table tennis

Entomology, Soils, & Plant Sciences Department
Agronomy -- Entomology -- Plant Pathology-- Soil Science
114 Long Hall, Clemson University
Clemson, SC 29634-0315
office (864)656-3111 fax (864)656-0274

M.S. and Ph.D. in Plant & Environmental Science -- B.S. in Soils and Sustainable Crop Systems
Faculty/Staff -- Research Programs -- Extension/Public Service

Tiger Weather

College of Agriculture, Forestry and Life Sciences -- Public Service and Agriculture (PSA)