scholarly journals Phytophthora Blight Caused by Phytophthora capsici on Pumpkin and Winter Squash in Texas

Plant Disease ◽  
2007 ◽  
Vol 91 (5) ◽  
pp. 633-633 ◽  
Author(s):  
T. Isakeit
Keyword(s):  
Phytophthora Capsici ◽  
Morphological Characteristics ◽  
Lima Bean ◽  
The United States ◽  
Fruit Rot ◽  
High Plains ◽  
Phytophthora Blight ◽  
Lower Rio Grande Valley ◽  
Production Areas ◽  
Winter Squash

Phytophthora blight of pumpkin and squash (Cucurbita spp.) has increased in importance in many production areas of the United States in recent years. This disease was seen on a 36-ha commercial field of several cultivars of pumpkin and winter squash (including Cucurbita maxima cvs. Prizewinner, Atlantic Giant, and Casper and C. pepo cvs. Howden, Festival, Sweet Dumpling, and Magic Lantern) in Yoakum County in the High Plains of Texas during August of 2006. At that time, 2% of the field was affected. A month later, after unusually frequent rain showers and higher-than-average precipitation, 78% of the field was lost in spite of an aggressive fungicide program following the initial diagnosis. Symptoms consisted of white, velvety growth on fruit, fruit rot, leaf blight, and wilt. Sporangia on fruit were papillate, ovoid to ellipsoid, and measured 37 to 40 × 21 to 23 μm. Isolations were made from tissue onto water agar and two isolates used for further study were maintained on corn meal agar. When isolates were paired on V8 agar with two Phytophthora capsici isolates from pepper (3) of opposite mating type, amphigynous antheridia and plerotic oospores 25 to 27 μm in diameter were produced. The morphological characteristics of the isolates were consistent with P. capsici (1). Four-week-old plants of C. maxima cv. Cinderella and C. pepo cvs. Festival and Sweet Dumpling growing in Metro-Mix 366 were inoculated with each isolate by placing 2 cm3 of a 6-week-old culture from lima bean agar (0.2% agar) adjacent to the base of each stem. The soil was then watered to saturation. There were four plants per 2.8-liter pot and two pots per isolate-cultivar combination. Plants were grown in the greenhouse at 18 to 27°C. The test was repeated once. Wilting and stem collapse were seen on inoculated plants 2 to 7 days later, sometimes with production of sporangia on stems. The pathogen was consistently reisolated from symptomatic plants, fulfilling Koch's postulates. These isolates were also pathogenic to pepper (Capsicum annuum). The affected field had been planted to pumpkins and winter squash the previous year when the grower saw similar symptoms on a few plants. In 2004, this field was planted to wheat. There are 1,350 ha of pumpkins produced in Texas, mostly in High Plains counties, and 730-ha squash produced throughout the state. To my knowledge, this is the first report of Phytophthora blight on pumpkin and winter squash in Texas. Phytophthora blight has been a long-standing problem of peppers grown in the Lower Rio Grande Valley of Texas (2), which is 900 km from Yoakum County. References: (1) D. C. Erwin and O. K. Ribeiro. Phytophthora Diseases Worldwide. The American Phytopathological Society. St. Paul, MN. 1996. (2) G. H. Godfrey. Plant Dis. Rep. 31:8, 1947. (3) B. Villalon. Phytopathology (Abstr.) 86(suppl):S118, 1996.

scholarly journals Characterizing Sources of Resistance to Phytophthora Blight of Pepper Caused by Phytophthora capsici in North Carolina

2019 ◽  
Vol 20 (2) ◽  
pp. 112-119
Author(s):  
Camilo H. Parada-Rojas ◽  
Lina M. Quesada-Ocampo
Keyword(s):  
North Carolina ◽  
Phytophthora Capsici ◽  
The United States ◽  
Field Trials ◽  
Fruit Rot ◽  
Phytophthora Blight ◽  
Sources Of Resistance ◽  
Crown Root ◽  
Different Levels ◽  
Important Disease

Phytophthora blight, caused by Phytophthora capsici, is an important disease of peppers in the United States and worldwide. P. capsici causes crown, root, and fruit rot as well as foliar lesions in peppers. Field trials were conducted in 2015 and 2016 to evaluate 32 commercial and experimental pepper cultivars against a mixed-isolate inoculum in North Carolina. Cultivars Martha-R and Meeting were classified as highly resistant to P. capsici, and Paladin was classified as resistant. Intermediate resistance to P. capsici in the field was observed with Fabuloso, Revolution, Vanguard, Archimedes, Aristotle, Ebano-R, and Declaration. Greenhouse experiments were conducted to determine the response of 48 pepper cultivars when inoculated individually with two isolates from North Carolina and an isolate from Michigan. Isolates exhibited different levels of virulence in pepper cultivars screened for resistance. Landraces CM334 and Fidel as well as the cultivars Martha-R, Meeting, and Intruder were categorized as highly resistant or resistant to the three isolates tested. Overall, highly resistant cultivars tended to respond similarly to field mix inoculations and greenhouse single isolate inoculations.

scholarly journals Inheritance of Resistance to Crown Rot Caused by Phytophthora capsici in Cucurbita

HortScience ◽  
2009 ◽  
Vol 44 (1) ◽  
pp. 211-213 ◽  
Author(s):  
Les D. Padley ◽  
Eileen A. Kabelka ◽  
Pamela D. Roberts
Keyword(s):  
Phytophthora Capsici ◽  
Backcross Progeny ◽  
The United States ◽  
Crown Rot ◽  
Inheritance Of Resistance ◽  
University Of Florida ◽  
Growing Seasons ◽  
Production Areas ◽  
Winter Squash ◽  
Dominant Genes

The various disease syndromes caused by Phytopthora capsici Leonian can be devastating to squash (Cucurbita spp.) production areas of the United States. In some growing seasons, yield loss has been reported up to 100%. A recently developed University of Florida Cucurbita breeding line, #394-1-27-12, resistant to the crown rot syndrome of P. capsici, was used to determine the inheritance of resistance to this disease. Data from F1, F2, and backcross progeny from crosses of a P. capsici-susceptible butternut-type winter squash (C. moschata) with #394-1-27-12 indicated that resistance is conferred by three dominant genes. The introgression of P. capsici crown rot resistance from #394-1-27-12 into morphologically diverse domesticates within Cucurbita will aid in the management of this economically important pathogen.

scholarly journals Evaluation of a Diverse, Worldwide Collection of Wild, Cultivated, and Landrace Pepper (Capsicum annuum) for Resistance to Phytophthora Fruit Rot, Genetic Diversity, and Population Structure

2015 ◽  
Vol 105 (1) ◽  
pp. 110-118 ◽  
Author(s):  
R. P. Naegele ◽  
A. J. Tomlinson ◽  
M. K. Hausbeck
Keyword(s):  
Genetic Diversity ◽  
Population Structure ◽  
Phytophthora Capsici ◽  
The United States ◽  
Fruit Rot ◽  
Sources Of Resistance ◽  
Plant Introductions ◽  
Genetic Clusters ◽  
Commercial Breeding ◽  
Moderately Resistant

Pepper is the third most important solanaceous crop in the United States and fourth most important worldwide. To identify sources of resistance for commercial breeding, 170 pepper genotypes from five continents and 45 countries were evaluated for Phytophthora fruit rot resistance using two isolates of Phytophthora capsici. Genetic diversity and population structure were assessed on a subset of 157 genotypes using 23 polymorphic simple sequence repeats. Partial resistance and isolate-specific interactions were identified in the population at both 3 and 5 days postinoculation (dpi). Plant introductions (PIs) 640833 and 566811 were the most resistant lines evaluated at 5 dpi to isolates 12889 and OP97, with mean lesion areas less than Criollo de Morelos. Genetic diversity was moderate (0.44) in the population. The program STRUCTURE inferred four genetic clusters with moderate to very great differentiation among clusters. Most lines evaluated were susceptible or moderately susceptible at 5 dpi, and no lines evaluated were completely resistant to Phytophthora fruit rot. Significant population structure was detected when pepper varieties were grouped by predefined categories of disease resistance, continent, and country of origin. Moderately resistant or resistant PIs to both isolates of P. capsici at 5 dpi were in genetic clusters one and two.

scholarly journals Fungicide Rotation Programs for Managing Phytophthora Fruit Rot of Watermelon in Southeastern United States

2017 ◽  
Vol 18 (1) ◽  
pp. 28-34 ◽  
Author(s):  
Chandrasekar (Shaker) S. Kousik ◽  
Pingsheng Ji ◽  
Daniel S. Egel ◽  
Lina M. Quesada-Ocampo
Keyword(s):  
United States ◽  
South Carolina ◽  
Phytophthora Capsici ◽  
Southeastern United States ◽  
Heavy Rain ◽  
Integrated Approach ◽  
The United States ◽  
Fruit Rot ◽  
Management Options ◽  
Before And After

About 50% of the watermelons in the United States are produced in the southeastern states, where optimal conditions for development of Phytophthora fruit rot prevail. Phytophthora fruit rot significantly limits watermelon production by causing serious yield losses before and after fruit harvest. Efficacy of fungicide rotation programs and Melcast-scheduled sprays for managing Phytophthora fruit rot was determined by conducting experiments in Phytophthora capsici-infested fields at three locations in southeastern United States (North Carolina, South Carolina, and Georgia). The mini seedless cultivar Wonder and seeded cultivar Mickey Lee (pollenizer) were used. Five weekly applications of fungicides were made at all locations. Significant fruit rot (53 to 91%, mean 68%) was observed in the nontreated control plots in all three years (2013 to 2015) and across locations. All fungicide rotation programs significantly reduced Phytophthora fruit rot compared with nontreated controls. Overall, the rotation of Zampro alternated with Orondis was highly effective across three locations and two years. Rotations of Actigard followed by Ranman+Ridomil Gold, Presidio, V-10208, and Orondis, or rotation of Revus alternated with Presidio were similarly effective. Use of Melcast, a melon disease-forecasting tool, may occasionally enable savings of one spray application without significantly impacting control. Although many fungicides are available for use in rotations, under very heavy rain and pathogen pressure, the fungicides alone may not offer adequate protection; therefore, an integrated approach should be used with other management options including well-drained fields.

scholarly journals Evaluation of Winter Squash and Pumpkin Cultivars for Age-related Resistance to Phytophthora capsici Fruit Rot

HortScience ◽  
2016 ◽  
Vol 51 (10) ◽  
pp. 1251-1255 ◽  
Author(s):  
Charles S. Krasnow ◽  
Mary K. Hausbeck
Keyword(s):  
Cucurbita Pepo ◽  
Disease Incidence ◽  
Phytophthora Capsici ◽  
Genetic Resistance ◽  
Fruit Rot ◽  
Infested Soil ◽  
Cucurbita Moschata ◽  
Cucurbita Maxima ◽  
Age Related ◽  
Winter Squash

Phytophthora capsici annually threatens production of cucurbit and solanaceous crops. Long-lived oospores produced by the pathogen incite primary infection of susceptible plants when conditions are wet. Limiting the rot of winter squash and pumpkin (Cucurbita sp.) fruits is difficult due to the long maturation period when fruits are often in direct contact with infested soil. Genetic resistance to fruit rot is not widely available within Cucurbita sp.; however, age-related resistance (ARR) to P. capsici fruit rot develops in specific cultivars during maturation. The objective of this study was to evaluate the fruits of 12 cultivars of Cucurbita pepo, Cucurbita moschata, and Cucurbita maxima for ARR to P. capsici using a mycelial-plug inoculation method. All Cucurbita pepo and Cucurbita moschata cultivars displayed ARR; 7 days postpollination (dpp) fruits were susceptible, limited lesion development occurred on fruits 22 dpp, and lesions did not develop at 56 dpp. Disease developed on both Cucurbita maxima cultivars tested at 7, 14, 22, and 56 dpp. Firmness of fruit exocarps was measured with a manual penetrometer. Exocarp firmness of all cultivars increased during maturation; however, there was no correlation between firmness and disease incidence among cultivars at 22 dpp (R2 = −0.01, P = 0.85). When fruits of cultivars expressing ARR at 22 dpp were wounded before inoculation, fruit rot developed.

scholarly journals Outbreak of Phytophthora Foliar Blight and Fruit Rot in Processing Pumpkin Fields in Illinois

Plant Disease ◽  
2000 ◽  
Vol 84 (12) ◽  
pp. 1345-1345 ◽  
Author(s):  
M. Babadoost
Keyword(s):  
Phytophthora Capsici ◽  
The United States ◽  
Leaf Blight ◽  
Fruit Rot ◽  
Infected Leaf ◽  
American Phytopathological Society ◽  
Foliar Blight ◽  
Highly Correlated ◽  
June July ◽  
Central Illinois

Approximately 65% of the total commercial processing pumpkins (Cucurbita moschata Poir.) in the United States are produced in central Illinois. In 1999, Phytophthora capsici caused severe foliar blight and fruit rot in processing pumpkin fields in Illinois. Infection was widely observed in July when fruit weights were approximately 5 kg and continued until harvest in late August. Infection of the fruit generally started on the side contacting the soil. However, when an infected leaf came in contact with a fruit, fruit rot started at the site of contact. Many fruits that looked normal fell apart when they were turned for examination. Infected fruit were generally covered with white, cottony growth consisting of mycelium, sporangiophores, and sporangia. Leaf infection began as small chlorotic lesions, which enlarged and became necrotic. Leaf petioles also were infected and developed lesions that girdled petioles, causing the collapse and death of leaves. Vines also were infected and developed girdling lesions. The girdling lesions, which caused collapse and death of the vines, were observed on all parts of the vines. Affected vines collapsed and died. Roots and crowns of the plants with foliar blight and fruit rot exhibited little brownish discoloration or no symptoms. In most fields, the disease started in low-lying areas but spread rapidly throughout the field. The disease occurred in both irrigated and nonirrigated fields. In August, approximately 1 week before harvest, one nonirrigated and eight irrigated fields, a total of 267 ha, were surveyed to assess the incidence of disease. The incidence of disease was determined by examining vines, leaves, and fruit in 10 plots (36 m2 each) per field by walking a path on the longest diagonal of each field. In each plot, 10 plants were inspected, with one vine, 10 leaves on the vine, and one fruit of each plant (total of 10 vines, 100 leaves, and 10 fruits in each plot) were examined for infection. The incidence of vine blight, leaf blight, and fruit rot in the nonirrigated field was 30, 50, and 49%, respectively. The incidence of vine blight, leaf blight, and fruit rot in irrigated fields ranged from 4 to 48% (average 21%), 17 to 68% (average 40%), and 4 to 71% (average 32%), respectively. The incidence of vine blight, leaf blight, and fruit rot were highly correlated. Due to severe fruit rot, two of the irrigated fields were not harvested. In Illinois, processing pumpkins are planted in May and harvested in August. Recorded precipitation in the pumpkin growing area in Illinois in 1999, was 9 days (211 mm), 7 days (113 mm), 7 days (147 mm), and 7 days (91 mm) in May, June, July, and August, respectively. It is believed that the frequent and high rainfall during the growing season in the area resulted in the outbreak of Phytophthora foliar and fruit rot in processing pumpkins in Illinois in 1999. References: (1) D. C. Erwin and O. K. Ribeiro. 1996. Phytophthora Diseases Worldwide. The American Phytopathological Society, St. Paul, MN. (2) M. T. McGrath. 1998. Biological and Cultural Tests. The American Phytopathological Society, St. Paul, MN.

scholarly journals First Report of Mefenoxam-Resistant Isolates of Phytophthora capsici from Lima Bean Pods in the Mid-Atlantic Region

Plant Disease ◽  
2008 ◽  
Vol 92 (4) ◽  
pp. 656-656 ◽  
Author(s):  
J. F. Davey ◽  
N. F. Gregory ◽  
R. P. Mulrooney ◽  
T. A. Evans ◽  
R. B. Carroll
Keyword(s):  
Foliar Application ◽  
Phytophthora Capsici ◽  
Crop Protection ◽  
Lima Bean ◽  
Fruit Rot ◽  
Resistant Isolate ◽  
Phaseolus Lunatus ◽  
Atlantic Region ◽  
History Of ◽  
Lima Beans

Phytophthora capsici Leonian, the causal agent of lima bean pod rot, was first identified as a pathogen of lima bean in 2002 (1) and poses a new threat to lima bean (Phaseolus lunatus L.) production in the Mid-Atlantic Region. The phenylamide fungicide mefenoxam (Ridomil Gold; Syngenta Crop Protection) is widely used in the region for controlling foliar and soilborne diseases caused by Oomycetes. Isolates of P. capsici were collected from lima bean pods from production fields in Delaware, Maryland, and New Jersey from 1998 to 2004. These isolates originated from survey samples of lima bean fields for another pathogen, P. phaseoli, in 1999 and 2000 and diagnostic samples were submitted to the Plant Disease Clinic. Isolates were from lima bean, except for one from pepper (basal stem). Identification was made on the basis of morphometric characteristics. No known sensitive or insensitive isolates were included in the evaluation. Single zoospore cultures were evaluated for mefenoxam sensitivity on V8 agar plates amended with 100 ppm of mefenoxam, a previously tested concentration (2). Seven-millimeter-diameter agar plugs of each isolate were cut from the edge of actively expanding cultures of P. capsici with a cork borer and transferred to three V8 agar plates amended with mefenoxam and three unamended V8 plates. The plates were arranged in a completely randomized design and incubated at 25°C in the dark for 3 days. After incubation, colony growth was measured in millimeters and averaged for the three replicate plates of each isolate and percent growth relative to the unamended control was calculated. Mefenoxam sensitivity was assigned according to methods of Lamour et al. (2). The experiment was repeated once, and also run with a treatment of 200 ppm of mefenoxam. Of sixteen isolates screened, nine were rated as sensitive, four were intermediately resistant, and three were resistant. There was no difference between the 100 and 200 ppm results, except for a slight increase in sensitivity for one isolate. A subsequent experiment tested five isolates at concentrations of 1, 10, 100, and 1,000 ppm. Results were consistent with previous tests, with resistant isolates exhibiting some growth at the highest concentration of mefenoxam. One resistant isolate was from a field in Delaware previously cropped to slicing cucumbers with a history of mefenoxam applications. The second was from Caroline County, MD, which is heavily cropped to pickling cucumbers and likely to have been exposed to mefanoxam applications for the control of fruit rot; the origin of the third insensitive isolate from lima bean is unknown. Mefanoxam usage on lima bean is usually limited to one foliar application of mefenoxam+copper hydroxide to control downy mildew in the fall crop in wet seasons. This study indicates that mefenoxam resistance is present in populations of P. capsici in lima bean fields in the Mid-Atlantic Region, presumably as a result of mefenoxam applications to other vegetable crops, principally cucurbits, which are planted in rotation with lima beans or from nearby cucurbit fields. Implementing strategies to minimize fungicide resistance in other vegetables is important to slow resistance development associated with this emerging pathogen on lima beans. Lima bean pod rot continues to be seen sporadically each year in fields with a history of P. capsici and abundant rainfall or excessive irrigation. References: (1) C. R. Davidson et al. Plant Dis. 86:1049, 2002. (2) K. H. Lamour et al. Phytopathology 90:396, 2000.

scholarly journals Changes in Winter Squash Fruit Exocarp Structure Associated with Age-Related Resistance to Phytophthora capsici

2020 ◽  
Vol 110 (2) ◽  
pp. 447-455 ◽  
Author(s):  
Safa A. Alzohairy ◽  
Raymond Hammerschmidt ◽  
Mary K. Hausbeck
Keyword(s):  
Electron Microscopy ◽  
Phytophthora Capsici ◽  
Fruit Rot ◽  
Structural Barriers ◽  
Microscopy Imaging ◽  
Age Related ◽  
Structural Barrier ◽  
Winter Squash ◽  
Thickened Cuticle ◽  
Scanning Electron

Phytophthora capsici is a destructive pathogen of cucurbits that causes root, crown, and fruit rot. Winter squash (Cucurbita spp.) production is limited by this pathogen in Michigan and other U.S. growing regions. Age-related resistance (ARR) to P. capsici occurs in C. moschata fruit but is negated by wounding. This study aimed to determine whether structural barriers to infection exist in the intact exocarp of maturing fruit exhibiting ARR. Five C. moschata cultivars were evaluated for resistance to P. capsici 10, 14, 16, 18, and 21 days postpollination (dpp). Scanning electron microscopy imaging of Chieftain butternut fruit exocarp of susceptible fruit at 7 dpp and resistant fruit at 14 and 21 dpp revealed significant increases in cuticle and epidermal thicknesses as fruit aged. P. capsici hyphae penetrated susceptible fruit at 7 dpp directly from the surface or through wounds before 6 h postinoculation (hpi) and completely degraded the fruit cell wall within 48 hpi. Resistant fruit remained unaffected at 14 and 21 dpp. The high correlation between the formation of a thickened cuticle and epidermis in maturing winter squash fruit and resistance to P. capsici indicates the presence of a structural barrier to P. capsici as the fruit matures.

scholarly journals Advances in Research on Phytophthora capsici on Vegetable Crops in The United States

Plant Disease ◽  
2012 ◽  
Vol 96 (11) ◽  
pp. 1588-1600 ◽  
Author(s):  
Leah L. Granke ◽  
Lina Quesada-Ocampo ◽  
Kurt Lamour ◽  
Mary K. Hausbeck
Keyword(s):  
Host Range ◽  
Phytophthora Capsici ◽  
The United States ◽  
Fruit Rot ◽  
Economic Losses ◽  
Future Research ◽  
Vegetable Crops ◽  
Long Distance ◽  
Term Survival ◽  
Wide Range

Since L. H. Leonian's first description of Phytophthora capsici as a pathogen of chile pepper in 1922, we have made many advances in our understanding of this pathogen's biology, host range, dissemination, and management. P. capsici causes foliar blighting, damping-off, wilting, and root, stem, and fruit rot of susceptible hosts, and economic losses are experienced annually in vegetable crops including cucurbits and peppers. Symptoms of P. capsici infection may manifest as stunting, girdling, or cankers for some cultivars or crops that are less susceptible. P. capsici continues to be a constraint on production, and implementation of an aggressive integrated management scheme can still result in insufficient control when weather is favorable for disease. Management of diseases caused by P. capsici is currently limited by the long-term survival of the pathogen as oospores in the soil, a wide host range, long-distance movement of the pathogen in surface water used for irrigation, the presence of fungicide-resistant pathogen populations, and a lack of commercially acceptable resistant host varieties. P. capsici can infect a wide range of hosts under laboratory and greenhouse conditions including cultivated crops, ornamentals, and native plants belonging to diverse plant families. As our understanding of P. capsici continues to grow, future research should focus on developing novel and effective solutions to manage this pathogen and prevent economic losses due to the diseases it causes.

scholarly journals First Report of Fruit Rot and Associated Branch Dieback of Almond in California Caused by a Phomopsis Species Tentatively Identified as P. amygdali

Plant Disease ◽  
1999 ◽  
Vol 83 (11) ◽  
pp. 1073-1073 ◽  
Author(s):  
J. E. Adaskaveg ◽  
H. Förster ◽  
J. H. Connell
Keyword(s):  
Disease Incidence ◽  
Morphological Characteristics ◽  
The United States ◽  
Tree Canopy ◽  
Fruit Rot ◽  
Control Treatment ◽  
Field Inoculation ◽  
First Report ◽  
Branch Dieback ◽  
Summer Fruit

A fruit rot of almond (Prunus dulcis (Mill.) D. Webb.) was observed in an orchard in Durham, CA (Butte County), in June of 1998 after an unusually wet spring with a total precipitation of 17.2 cm for April and May. Disease incidence on fully developed fruit of almond cv. Sonora was nearly 90% in the lower tree canopy by July. Almond cv. Nonpareil grown in alternate rows in the same orchard was much less affected. Fruit symptoms included extensive grayish brown discolored and shriveled hulls, often associated with a clear gum secretion and shriveled kernels. Affected fruit frequently abscised. Leaf symptoms and branch dieback were not associated with the disease in 1998. In May of 1999, however, extensive twig dieback was observed on almond cv. Sonora in the same orchard. Isolations from more than 100 symptomatic fruit were conducted from 9 sampling sites in the 9-ha orchard. Based on morphological characteristics, the same fungus was isolated from 93% of the fruit. The fungus also was isolated consistently from samples exhibiting twig dieback. During a major disease survey conducted in 1998, the fungus was only incidentally isolated from almond fruit from other California orchards. Ascomata were not observed in vivo or in vitro. The fungus produced alpha and beta spores in pycnidia when cultured on potato dextrose agar. Spore measurements were obtained from 10 spores for each of 3 isolates obtained from fruit or twig dieback of almond cv. Sonora. Conidial dimensions of fruit and twig isolates were very similar. Based on spore sizes, with alpha spores measuring 5.3 to 7.5 (to 8) × 1.7 to 2.5 μm and beta spores measuring12.8 to 29.8 × 0.6 to 0.7 μm, the fungus was tentatively identified as Phomopsis amygdali (Del.) Tuset & Portilla (2). Previous reports on this fungus (2), however, indicated that beta spores are not produced in culture, and disease symptoms have not been observed on fruit. The fungus was morphologically different from other species of Phomopsis reported from almond and other Prunus species, including P. mali Roberts, P. padina (Sacc. & Roum.) Died., P. parabolica Petrak, P. perniciosa Grove, P. pruni (Ellis & Dearn.) Wehm., P. prunorum (Cooke) Grove, P. ribetejana Camara, and P. stipata (Lib.) Sutton (3). Field inoculation studies were performed in May of 1999 on almond cvs. Carmel and Mission. Almond fruit were wounded (2 × 2 × 2 mm) or left unwounded and were sprayed with water (control) or a suspension of alpha spores (105 spores per ml). Branches were bagged for 4 days to maintain high humidity. Fruit symptoms on cv. Carmel were observed after 4 weeks on wounded and nonwounded inoculated fruit, and P. amygdali was successfully reisolated from diseased tissue. No symptoms were observed in the control treatment for almond cv. Carmel or in any treatment for cv. Mission. This is the first report of P. amygdali causing a late spring and summer fruit rot and associated branch dieback of almond in North America (1). References: (1) D. F. Farr et al. 1989. Fungi on Plants and Plant Products in the United States. The American Phytopathological Society, St. Paul, MN. (2) J. J. Tuset and M. T. Portilla. Taxonomic status of Fusicoccum amygdali and Phomopsis amygdalina. Can. J. Bot. 67:1275, 1989. (3) F. A. Uecker. 1988. A World List of Phomopsis Names with Notes on Nomenclature, Morphology, and Biology. Mycologia Memoir No. 13. J. Cramer, Berlin.

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