CHARACTERIZATION AND IMPROVED MANAGEMENT OF IMPORTANT PEACH AND STRAWBERRY DISEASES IN SOUTH CAROLINA AND THE EASTERN UNITED STATES.

• Sponsoring Institution: National Institute of Food and Agriculture
• Project Status: COMPLETE
• Funding Source: HATCH
• Reporting Frequency: Annual
• Accession No.: 1004858
• Project Start Date: Jan 9, 2015
• Project End Date: Oct 15, 2016
• Program Code: [(N/A)]- (N/A)

Recipient Organization
CLEMSON UNIVERSITY
(N/A)
CLEMSON,SC 29634

Performing Department
Agricultural & Environmental Sciences

Non Technical Summary
Diseases of fruit crops are a significant limiting factor in production agriculture.Some diseases are very difficult to control because the causal organismpersist in the soil protected in roots from microbial decay and fungicide drenches.In the southeastern United States,Armillaria root rot caused by the soilborne fungusArmillaria tabescens is now the number one peach tree killer. Chemical and biological attempts to control this disease have failed but new horticultural methods may allow growers to replant trees successfully on infested sites. Other diseases are successfully controlled with integrated approaches including fungicide applications but many causal organisms are now developing resistance to fungicides. Resistance is a serious threat because Integrated Pest Managementpractices depend on the application of fungicides. Communicating research findings and control strategies with growers is just as critical as developing them. We are interested in using modern technology, specifically smartphones, to promoteIPM practices. Thegoal of this project is to address these issues and come up with solutions that ensure sustainable fruit crop production in South Carolina and neighboring states. Specific objectives are to(i) Investigate root collar excavation to extend the life of peach trees on replant sites, (ii) Characterize and manage multifungicide resistance in important pathogens of small fruits and stone fruits, and to (iii)develop MyIPM, a new smartphone app for IPM implementation in strawberry.

Animal Health Component

40%

Research Effort Categories

Basic

40%

Applied

40%

Developmental

20%

Classification

Knowledge Area (KA)	Subject of Investigation (SOI)	Field of Science (FOS)	Percent
212	1114	1160	50%
212	1122	1160	50%

Knowledge Area
212 - Pathogens and Nematodes Affecting Plants;

Subject Of Investigation
1114 - Peach; 1122 - Strawberry;

Field Of Science
1160 - Pathology;

Keywords

fungicide resistance

monilinia fructicola

alternaria alternata

colletotrichum acutatum

colletotrichum gloeosporioides

armillaria mellea

Goals / Objectives
The goal of this project is to provideSouth Carolina fruit grower with the tools needed for sustainable management of crop diseases and to help implement sound IPM practices.Investigate root collar excavation to extend the life of peach trees on replant sitesCharacterization and management of multifungicide resistance in Botrytis cinerea, Alternaria alternata, and Colletotrichum spp. on strawberry and peach.Development of MyIPM, a new smartphone app for IPM implementation in strawberry and peach

Project Methods
Objective 1. Investigate root collar excavation to extend the life of peach trees on replant sites. Large scale field trials were established in 2011 on ARR-infested replant sites at 3 producer locations (Fisher Orchards, Titan Farms, Hyder Farms) and at the Musser Fruit Research Farm. Berms were established either with the Savannah Plow or disc plows. We will be taking yield (first, second and third pick), disease incidence and disease severity data at each location. We will count the number of suckers coming from the crown of the trees. The exposed roots may be vulnerable to standard herbicides The susceptibility of those roots to standard herbicides will be investigated to investigate potential increased susceptibility of excavated roots. Upon completion of this multiyear study, we will summarize the data and if the data indicate that AGRCE under commercial conditions reduces ARR, we will promote this system via extension publications, during production meetings, and at conferences. The trials themselves will be used as grower demonstration trials and have been used successfully already to discuss this option with interested growers.Objective 2. Characterization and management of multifungicide resistance in important pathogens of small fruits and stone fruits. Resistance profiles for B. cinerea will be determined using traditional growth inhibition assays at discriminatory doses (Fernandez Ortuno et al, Plant Dis.).We will monitor fungicide resistance profiles that are subjected to different management strategies and compare the resistance profile at the beginning of the season with that of the end of the season. We will collect and analyze (i) before and after resistance profiles, (i) spray records, (ii) information on the origin of plant source, (iii) spray history, (iv) and info on alternate hosts of the farm for analysis. In addition, we will choose commercial production sites in Florida and South Carolina for more detailed analysis to investigate how SAS plus resistance management strategies based on resistance profiling influence selection of multifungicide resistance. At these locations we will compare three major spray strategies: grower standard (weekly applications); SAS (reducted number of sprays); and SAS plus Location Specific Resistance Profiling (LSRP).Strategy 1: Grower StandardStrategy 1: SAS plus rotating/mixing available registered fungicidesStrategy 2: SAS plus rotating/mixing low risk fungicides identified by LSRPFor each location, we will determine and compare the baseline resistance profiles (20 isolates) at bloom and the season-end profiles for three years, which will allow us to investigate carry over genotypes that may have survived on alternate hosts or plant residue.As we have shown in our recent studies, the gray mold pathogen responds quickly to new management strategies by evolving new mechanisms of resistance. Understanding the genetic basis of resistance evolution is critical for the design of future management strategies. We will monitor shifts in genotypes over the course of the field trials and study new genotypes discovered through our regional resistance monitoring.Objective 3. Development of MyIPM, a new smartphone app for IPM implementation in strawberryThe MyIPM app will include Disease, Arthropod, and Weed diagnostics tools for strawberry with the idea in mind to use the same code for other specialty crops in the future such as other small fruits or pome and stone fruits. The app for strawberry growers is going to be complex and will include multiple features for multiple disciplines. It is being developed in stages, starting with the code for one discipline 'Diseases'. Developing the code for the disease portion is in progress, but we will add arthropods and weeds over time as well as additional features. Key features of the app are:- Disease diagnostics (pictures and descriptions of signs and symptoms of fungal, bacterial, and viral diseases; concise epidemiology of the disease). This feature for now will be of regional scope but could be expanded to include diseases that may not be an issue in the southeast but are an issue elsewhere.- List of registered active ingredients (conventional fungicides and biorationals), searchable, sortable, listed by disease, color-coded FRAC codes, efficacy ratings, and toxicity ratings. The efficacy data for conventional and biorational fungicides will be obtained ,summarized, and averaged from independent published reports conducted in the United States such as Plant Disease Management Reports, the journal 'Plant Disease', and specialist consensus that can typically found in production guides.- List of registered trade names (fungicides and biorationals separately), searchable, sortable, listed by disease, rate per acre, PHI, REI, toxicity rating and efficacy rating (We are using www.cdms.net to access labels and determine what products are registered for a certain crop as well as regional spray guides). This feature is of national scope.- One of the biggest advantages of smartphones is their ability to play audio recordings. I personally enjoy listening to science podcasts during runs or long car rides. This relatively new opportunity of educational outreach should be used to promote IPM. Inspired by our close collaborator Dr. Poling, we will offer preseason interviews with key extension specialists that are timely and with relevant information. Dr. Poling has already expressed interest in conducting some of these interviews. We have already been recording selected state production talks about disease, arthropod, and weed management that the user will be able to download and listen to at their leisure. Other opportunities include taping selected topic talks at regional production conferences such as the Savannah Fruit and Vegetable Conference or the NASA/NCSA Strawberry Expo and to record testimonies and experiences from growers who have tested IPM strategies on their farms. Some companies already tape educational talks at regional (Fruit and Vegetable Conference in Savannah) or national meetings and we will explore the possibility of tapping into this resource. This feature is of regional scope.- Texting with specialist(s). The idea is to have specialists and agents sign up for a certain discipline (horticulture, plant pathology, entomology, weed science) and indicate the states of their responsibility. When a grower wants to text a question/picture, the GPS feature in the app will locate the state at which this request is made and identifies automatically the specialist(s) that signed up for that state. The grower then sends the text/picture to the specialist(s) and starts a chat or group chat if he chose to include more than one available specialist or agent. The initial request by the grower (but not the follow up conversation) is saved in a permanent external database and kept as a record. There is currently no such feature available in agriculture and we believe that the simplicity of this feature and the potential for rapid, nearly immediate response will provide excellent service. This feature could be of national scope if specialists and agents from other regions signed up for the service.

Progress 01/09/15 to 10/15/16

Outputs
Target Audience:Peach growers and strawberry growers in South Carolina and elsewhere Southeastern Professional Fruit Workers General scientific audience Changes/Problems: Nothing Reported What opportunities for training and professional development has the project provided? Nothing Reported How have the results been disseminated to communities of interest?Grower production talks, conferences, publications, smartphone app content, website, handouts, demonstration trials in grower fields What do you plan to do during the next reporting period to accomplish the goals? Nothing Reported

Impacts
What was accomplished under these goals? We initiated three trials in South Carolina to investigate whether root collar excavation can be done on a large scale to combat Armillaria root rot; one at the Musser Fruit Research Farm near Seneca, SC, one at Titan Farms near Ridge Spring, SC and one at Fisher Orchards near Greer, SC. The sites were picked because previous plantings suffered from Armillaria root rot decline. After 5 years of establishment, trees are now starting to die at all three locations from Armillaria root rot. At the Ridge Spring location trees suffered from bacterial canker that likely camewith frost damage in 2014 and 2015. Consequently, a lot of trees died from this disease during that time. However, very few trees were lost to this disease in 2016. Both in Ridge Spring and Greer trees in the Grower Standard (GS) treatment started to die from Armillaria root rot in 2016. In the Ridge Spring location, 3.5% of all trees died of Armillaria root rot but none in the AGRCE had died. In the Greer location nearly 8% died from the same disease in the grower standard treatment and fewer trees (5%) had died in the AGRCE treatment. Above ground root collar excavation (AGRCE) is a powerful planting technique that continues to extend tree longevity. Excavated trees have been performing well over the years and the survival rate is much higher on replant sites with documented Armillaria problems. While data at the Ridge Spring and Greer locations come in slowly (2016 was the first year that we saw trees declining from Armillaria root rot), results at Musser Farm continue to impress. Almost 35 percent of all trees planted according to grower standards are now dead from Armillaria root rot but so far all trees with excavated roots continue to perform well. Previous research has shown that Botrytis cinerea isolates with resistance to multiple chemical classes of fungicides exist in eastern strawberry fields. In this study the fungicide resistance profiles of 2130 isolates from flowers of commercial strawberry fields located in multiple states was determined over 4 consecutive strawberry production seasons. Producers were asked to alternate single-site fungicides that were considered 'low risk' in their specific location based on resistance monitoring results in their fields. This guidance led to an increase of chemical class diversity used in the spray programs. Results indicated that simultaneous resistance in individual isolates to two, three, four, five, six, and seven classes of fungicides increased over time. The increase in resistancewithin isolates was likely due to a process we coined 'selection by association', where fungicide resistance traits were often linked to the trait being selected rather than the selectable trait itself. Data analysis also indicated that the odds were highest for isolates resistant to one chemical class (1CCR) to be resistant to thiophanate-methyl; for 2CCR isolates to be resistant to thiophanate-methyl and pyraclostrobin; and for 3CCR isolates to be resistant to thiophanate-methyl, pyraclostrobin, and either cyprodinil or fenhexamid. We hypothesize that the more chemical classes are used in a spray program, the faster isolates will be selected with increasing numbers of chemical class resistances by virtue of 'selection by association' if such isolates preexist in the population. Few fungicides are effective against anthracnose, caused by Colletotrichum spp., and emerging resistance makes the search for chemical alternatives more relevant. Isolates of the Colletotrichum acutatum species complex were collected from South Carolina and Georgia peach orchards and phylogenetic analysis of the combined internal transcribed spacer region, glyceraldehyde-3-phosphate dehydrogenase, and b-tubulin gene sequences separated the isolates into C. nymphaeae and C. fioriniae. The sensitivity of these and three other previously reported Colletotrichum spp. from peach, including C. fructicola, C. siamense, and C. truncatum, to demethylation inhibitor (DMI) fungicides difenoconazole, propiconazole, tebuconazole, metconazole, flutriafol, and fenbuconazole was determined based upon mycelial growth inhibition. C. truncatum was resistant to tebuconazole, metconazole, flutriafol, and fenbuconazole and C. nymphaeae was resistant to flutriafol and fenbuconazole based on 50% effective concentration (EC50) values >100 mg/ml. C. fructicola and C. siamense were sensitive to all DMI fungicides (EC50 values of 0.2 to 13.1 mg/ml). C. fioriniae subgroup 2 isolates were less sensitive to DMI fungicides (EC50 values of 0.5 to 16.2 mg/ml) compared with C. fioriniae subgroup 1 (EC50 values of 0.03 to 2.1 mg/ml). Difenoconazole and propiconazole provided the best control efficacy in vitro to all five species, with EC50 values of 0.2 to 2.7 mg/ml. Tebuconazole and metconazole were effective against all Colletotrichum spp., except for C. truncatum. The strong in vitro activity of some DMI fungicides against Colletotrichum spp. may be exploited for improved anthracnose disease management of peach. Integrated Pest Management (IPM) is a useful and environmentally sensitive strategy to pest management that relies on the incorporation of multiple 'common-sense' practices into a management program. While the individual practices may appear straightforward on paper, implementation of IPM can be hindered in several ways. Being able to identify pests from fungi to beetles and knowing which control measure is most effective while also reducing the risk of chemical resistance can be difficult, even for trained specialists. Producers are in need of tools to rapidly diagnose pests in the field, to navigate the plethora of active ingredients and trade names available for pest management, to cope with the increasing threat of pesticide resistance, and to obtain more training in pathogen biology, disease epidemiology, and cultural/chemical/biological management options. Thus, in 2012, we set out to develop a smartphone app to help strawberry and peach producers in South Carolina and Georgia understand and implement IPM principles. With the help of Clemson University computer scientist Roy Pargas as well as computer science and plant pathology students and postdocs, we developed MyIPM for iOS and Android platforms to address these needs. The first version was introduced during the 2014 Southeast Regional Fruit and Vegetable Conference in Savannah, GA. We provided the app free of charge to make sure all growers would have access to this new IPM tool (Schnabel 2015; Schnabel et al. 2015). The response was overwhelmingly positive from producers, agents, and fellow specialists and hundreds of downloads were recorded on both platforms within days of the meeting. Recognizing the value of the product and potential to be a major IPM tool, we were pressed almost instantly by strawberry growers and specialists alike to expand this app to include more strawberry pests and diseases and to include other crops because many strawberry growers diversify to spread the production risk. We therefore formed a team of specialists (see list of key personnel) from eastern states with expertise in a variety of fruit crops in plant pathology, fruit disorders, and entomology to address these needs. Through a virtual workshop and in-person training in 2015 we developed MyIPM-NED (northeastern diseases) for apples, pears, cherries, and cranberries, and MyIPM-SEP (southeastern pests) for strawberries, blueberries, and peaches. The original app was amended with blueberries and renamed MyIPM-SED (southeastern diseases). Since inception, these apps were downloaded more than 3300 times (all apps for Android and iOS), mostly from United States growers, but also from many growers abroad (40%).

Publications

• Type: Journal Articles Status: Published Year Published: 2016 Citation: Chen, S. N., C.X. Luo, M.J. Hu, and G. Schnabel 2016. Sensitivity of Colletotrichum species, including C. fioriniae and C. numphaeae, from peach to demethylation inhibitor fungicides. Plant Dis. 100:2434-2441.
• Type: Journal Articles Status: Published Year Published: 2016 Citation: Hu, M.J., K. D. Cox, and G. Schnabel 2016. Resistance to increasing chemical classes of fungicides by virtue of Selection by Association in Botrytis cinerea. Phytopathology 106:1513-1520.
• Type: Journal Articles Status: Published Year Published: 2016 Citation: Dowling, M. E., P. K. Bryson, H.G.Boatwright, J. R. Wilson, Z. Fan, S. E. Everhart, P. M. Brannen, and G. Schnabel 2016. Effect of fungicide applications on Monilinia fructicola population diversity and transposon movement. Phytopathology 106:1504-1512.
• Type: Journal Articles Status: Published Year Published: 2016 Citation: Dowling, M.E., Hu, M.J., Schmitz, L.T., Wilson, J.R., and G. Schnabel 2016. Characterization of Botrytis cinerea isolates from strawberry with reduced sensitivity to polyoxin D Zinc Salt. Plant Dis. 100:2057-2061.
• Type: Journal Articles Status: Published Year Published: 2016 Citation: Chen, S. N., C.X. Luo, M.J. Hu, and G. Schnabel 2016. Fitness and competitive ability of Botrytis cinerea isolates with resistance to multiple chemical classes of fungicides. Phytopathology 106:997-1005.
• Type: Journal Articles Status: Published Year Published: 2016 Citation: Ishii, H., F. Zhen, M. Hu, X. Li, and G. Schnabel 2016. Efficacy of SDHI fungicides, including benzovindi?upyr, against Colletotrichum species. Pest Manag. Sci. 72:1844-1853.
• Type: Journal Articles Status: Published Year Published: 2016 Citation: Hu, M., Fern�ndez-Ortu�o, D., and G. Schnabel. 2016. Monitoring resistance to SDHI fungicides in Botrytis cinerea from strawberry fields. Plant Dis. 100:959-965.

Progress 01/09/15 to 09/30/15

Outputs
Target Audience:Southeastern Peach Growers Southeastern Strawberry Growers Southeastern Professional Fruit Workers General Scientific Audience Changes/Problems: Nothing Reported What opportunities for training and professional development has the project provided?We provided the following training in 2015: Occurrance, Causes, and Management of peach bronzing. Workshop for growers, agents and specialists at the Madren Center, Clemson University, September 2015 Field day at Clemson University Musser Farm. 08/14/2015 Hu, M. J., and G. Schnabel 2015. Fungicide resistance issues on blackberry fields in North Carolina and South Carolina, XI International Rubus and Ribes Symposium, Asheville, NC (field day). MyIPM training for trainers in Clemson, SC. 2015. Location-specific resistance monitoring training for Canadian nursery stock producers. 4-day training in Clemson. Interpreting Resistance Management Reports. Workshop. 2014 Southeastern Strawberry Expo, Pinehurst, NC NC-140 field day at Musser Farm. Overview of Plant Pathology activities 2014 How have the results been disseminated to communities of interest?Through peer reviewed publications, book chapters, presentations, websites and smartphones What do you plan to do during the next reporting period to accomplish the goals?We will continue to collect data from our field trials, continue to develop smartphone apps using the MyIPM series, and continue to study options to manage multifungicide resistance.

Impacts
What was accomplished under these goals? Investigate root collar excavation to extend the life of peach trees on replant sites. There are three replicated trials in South Carolina, one at the Musser Fruit Research Farm near Seneca, one at Titan Farm near Ridge Spring and one at Fisher Orchards near Greer. The sites were picked because previous plantings suffered from Armillaria root rot decline. However, little infection pressure has been observed so far in Greer and Ridge Spring. Trees that did decline at the Ridge Spring location suffered from frost damage followed by bacterial canker infection. Yield data between treatments at the Ridge Spring location were not statistically different (P = 0.05) in 2014. The total fruit weight and average fruit weight of fruit from the AGRCE treatment was 27.4 and 0.48 lbs compared to 28.3 and 0.52 lbs in the control treatments, respectively. The only location with significant tree decline due to Armillaria root rot was in Seneca. There, only trees planted according to grower standard succumbed to the disease. Yield data at this location indicated a numerical, but not statistically significant, increase in yield over two consecutive years in the AGRCE treatment. This is consistent with anecdotal evidence from two South Carolina growers claiming that trees planted on berms appeared more vigorous than the grower standard. This perhaps is due to the fact that growers tend to plant trees too deep, which can deprive trees of oxygen and makes them more vulnerable to water logging. This may then lead to stressed trees that lack behind in development. At Titan Farm, NC State weed specialist Wayne Mitchum and Clemson University county agent Greg Henderson investigated the potential influence of herbicide treatments on root collar excavated trees. The trees were planted in 2011, excavated two years after planting (2013) and herbicide treatments were applied 21 days later. The same treatments were applied to the same trees in 2014. Results show no negative effects between untreated trees and trees that had received herbicide treatments with regard to yield and average fruit weight. The only difference we saw was between herbicide treatments 1 and 4. Results indicated that yield was lower in treatment 1 compared to treatment 4. Characterization and management of multifungicid resistance in plant pathogens of strawberry and peach. We found that isolates resistant to the SDHI fungicide, boscalid, regardless of genotype, were also resistant to pyraclostrobin and thiophanate-methyl. Resistance to pyraclostrobin was due to the G143A mutation in the cytb gene and resistance to thiophanate-methyl was due to a mutation of 167Y in the β-tubulin gene. Representatives of the two most commonly-isolated, SDHI resistance genotypes H277Y in sdh subunit B and H134R in sdh subunit C, as well as genotype D123E in sdh subunit D were selected for fitness evaluations. No competitive advantage was detected for sensitive isolates over the course of five consecutive transfers on peach fruit when spores were mixed with genotypes H277Y or H134R. Results suggest that in the absence of fungicide pressure, A. alternata isolates resistant to MBC, QoI, and SDHI fungicides carrying the H277Y mutation in SDHB and the H134R mutation in SDHC may effectively compete with the boscalid-sensitive populations. Anthracnose of peach is also a problem summer disease of peach in South Carolina. It is primarily caused by Colletotrichum acutatum and Colletotrichum gloeosporioides. Both species are also found in the southeastern United States, where a third species (Colletotrichum truncatum) was isolated from peach. C. gloeosporioides is recognized as a species complex and two subspecies, C. fructicola and C. siamense, were identified to cause anthracnose of peach in South Carolina (Hu et al. 2015). For example, during summer of 2012 and 2013, anthracnose incidence rose to commercially unacceptable levels (more than 50% preharvest fruit loss) in some late-season peach cultivars. In these cases, orchards had received applications of FRAC 1 and 11 fungicides for anthracnose control. The objective of this study was to (i) characterize the sensitivity of Colletotrichum isolates to thiophanate-methyl and azoxystrobin; (ii) investigate molecular mechanisms of resistance, and (iii) compare the efficacy of multiple chemical classes of fungicides for the control of thiophanate-methyl- and azoxystrobin-resistant isolates. Single-spore isolates of Colletotrichum siamense from South Carolina were either sensitive or resistant to both thiophanate-methyl and azoxystrobin with EC50 values >100 µg/ml. Resistant isolates revealed the E198A mutation in the β-tubulin (TUB2) gene and the G143A mutation in the cytochrome b (CYTB) gene. Phylogenetic analysis of C. siamense isolates from different locations and different crops showed that the resistant isolates were genetically closer to each other than to sensitive isolates, suggesting that field resistance to thiophanate-methyl and azoxystrobin fungcides is derived from a common ancestor. The investigation of C. gloeosporioides species allowed the discovery of species-specific selection of resistance to two chemical classes, including MBCs and QoIs. From a disease management standpoint, this study stresses the importance of knowing what Collototrichum species is present for resistance and disease management in commercial peach or blueberry production and also documents that certain DMI fungicides may be valuable rotation partners for resistance management. Development of MyIPM, a smartphone app for IPM implementation in fruits. We developed a new smartphone application, MyIPM, to promote Integrated Disease Management for sustained peach and strawberry production in the southern United States. The app is available in the Google Play Store and Apple Store. It features about a dozen of the most important diseases and disorders of the two fruit crops. For each disease/disorder there are pictures of signs and symptoms, descriptions of the causal agent, and a 2-min audio from the regional specialist. The app features chemical and biological control options, including a list of registered active ingredients for each disease that are sortable by FRAC codes and southeastern spray guide-published efficacy. The app also features field EIQ values as published by the Cornell IPM Program. The active ingredients are linked to registered trade names. MyIPM also features some audio recordings from regional specialists on peach and strawberry IPM issues. Our vision is that this app provides a valuable tool for growers and specialists alike that supplements current spray guides. The unique display of active ingredients, color-coded by chemical classes, provides a useful tool to promote resistance management. MyIPM is fed by an external database that can be updated through an authoring tool and is free of charge. It is expandable to more crops and could, with minor programming modifications, also be useful for entomologists. MyIPM provides Integrated Pest Management (IPM) information to conventional and organic producers of strawberries and peaches in the Southeastern United States. The target audience includes commercial growers, farm advisors, and specialists, but homeowners will also find useful information.

Publications

• Type: Journal Articles Status: Published Year Published: 2015 Citation: Hu, M. J., A. Grabke, and G. Schnabel 2015. Investigation of the Colletotrichum species complex causing peach anthracnose in South Carolina. Plant Dis. 99:797-805.
• Type: Journal Articles Status: Published Year Published: 2015 Citation: Hu, M. J., A. Grabke, M. E. Dowling, H. Holstein, and G. Schnabel 2015. Resistance in Colletotrichum siamense from peach and blueberry to thiophanate-methyl and azoxystrobin. Plant Dis. 99:806-814.
• Type: Journal Articles Status: Published Year Published: 2015 Citation: Yang, J. H., P. M. Brannen, and G. Schnabel 2015. Resistance in Alternaria alternata to SDHI fungicides causes rare disease outbreak in peach orchards. Plant Dis. 99:65-70.
• Type: Book Chapters Status: Published Year Published: 2015 Citation: Schnabel, G., M. J. Hu, and D. Fern�ndez-Ortu�o 2015. Monitoring resistance by bioassay: relating results to field use using culturing methods. In: Fungicide Resistance in Plant Pathogens. Springer Press, Eds. H. Ishii, and D. W. Hollomon, p251-280.