scholarly journals Postharvest Strategies for Managing Phytophthora Brown Rot of Citrus using Potassium Phosphite in Combination with Heat Treatments

Plant Disease ◽  
2015 ◽  
Vol 99 (11) ◽  
pp. 1477-1482 ◽  
Author(s):  
J. E. Adaskaveg ◽  
W. Hao ◽  
H. Förster
Keyword(s):  
Brown Rot ◽  
The United States ◽  
Heat Treatments ◽  
Water Control ◽  
Export Restrictions ◽  
Fruit Coating ◽  
Potassium Phosphite ◽  
Highly Effective ◽  
Orange Fruit ◽  
Water Treatments

Phytophthora brown rot, caused by several species of Phytophthora, is an economically important disease of citrus in areas with rainfall during the late stages of fruit development. Recent export restrictions of California orange fruit to China due to the presence of brown rot caused by the quarantine pathogen Phytophthora syringae have mandated more rigorous disease management. We evaluated postharvest applications with the phosphonate fungicide potassium phosphite in combination with heat treatments. In timing studies, potassium phosphite at 1,500 μg/ml was most effective when applied within 18 h after inoculation of orange fruit with P. citrophthora, reducing the incidence of decay by >96% as compared with the control. Potassium phosphite was also highly effective in inoculations with P. syringae. Heated water treatments at 60°C were consistently and highly effective in reducing the incidence of brown rot after inoculation with P. citrophthora, whereas treatments at 55 or 50°C were more variable and generally less effective. Two-stage treatments of fruit were conducted in the laboratory to simulate current packinghouse practices and to evaluate any interaction of the efficacy of potassium phosphite with treatments of two commonly used postharvest fungicides (i.e., imazalil and thiabendazole [TBZ]) or a postharvest carnauba-based fruit coating. In these studies, an aqueous imazalil-potassium phosphite (2,000 μg/ml) dip at ambient temperature that was followed by a spray treatment of imazalil and TBZ prepared in fruit coating significantly reduced the incidence of brown rot from the control. When the aqueous dip was applied at 54°C, brown rot developed in only 1% of the fruit as compared with 76% in the water control. The efficacy of potassium phosphite was also demonstrated in commercial packinghouse treatments. Based on our research, this fungicide was registered for postharvest use against brown rot of citrus and is exempt from tolerance in the United States and many other countries.

Resistance to Potassium Phosphite in Phytophthora Species Causing Citrus Brown Rot and Integrated Practices for Management of Resistant Isolates

Plant Disease ◽  
2020 ◽  
Author(s):  
Wei Hao ◽  
Helga Forster ◽  
James Adaskaveg
Keyword(s):  
Winter Season ◽  
Brown Rot ◽  
The United States ◽  
Phytophthora Species ◽  
Resistant Isolate ◽  
Multi Drug Resistance ◽  
In Vitro Toxicity ◽  
Potassium Phosphite ◽  
Moderately Resistant

Phytophthora citrophthora, P. syringae, P. nicotianae, and less commonly P. hibernalis are causal agents of brown rot of citrus fruit in California. The chronic disease occurs during the winter season, requires seasonal management, and has limited California citrus exports due to quarantines in some markets. Potassium phosphite (KPO3) is registered as a pre- and postharvest fungicide in the United States to manage Phytophthora brown rot. We evaluated the in vitro toxicity of KPO3 to 65, 60, and 38 isolates of P. citrophthora, P. syringae, and P. nicotianae, respectively, that were obtained from major growing regions of California. Frequency distributions of effective concentrations to inhibit mycelial growth by 50% (EC50 values) were not normally distributed with skewness values of 1.84, 1.60, and -0.51 for each species, respectively. Isolates considered sensitive (EC50 values <25 µg/ml), moderately resistant (EC50 values 25 to 75 µg/ml), or resistant (EC50 values >75 µg/ml) were identified for each species. The majority of P. citrophthora (83.1%) and P. syringae (78.3%) isolates were sensitive, whereas most P. nicotianae isolates (86.8%) were moderately resistant or resistant. Resistance factors were calculated as 65, 19, and 10 for the three species, respectively. In preharvest field trials, KPO3 (2,280 g/ha) applications were not effective in reducing citrus brown rot incidence when orange fruit were inoculated with a resistant (EC50 = 161.9 µg/ml) isolate of P. citrophthora demonstrating the potential for field resistance. Oxathiapiprolin (32.6 g/ha), however, was highly effective indicating the absence of multi-drug resistance. Postharvest treatments with KPO3 were only effective in reducing brown rot caused by the resistant isolate of P. citrophthora to a low incidence when high rates (8,000 µg/ml) were used in heated (54°C) applications. The sensitive and moderately resistant isolates were managed using rates of 4,000 µg/ml, but heated treatments at this rate were needed to reduce brown rot to commercially acceptable levels when decay was caused by a moderately resistant isolate.

scholarly journals Efficacy and Application Strategies for Propiconazole as a New Postharvest Fungicide for Managing Sour Rot and Green Mold of Citrus Fruit

Plant Disease ◽  
2012 ◽  
Vol 96 (2) ◽  
pp. 235-242 ◽  
Author(s):  
A. H. McKay ◽  
H. Förster ◽  
J. E. Adaskaveg
Keyword(s):  
Management Practices ◽  
Citrus Fruit ◽  
The United States ◽  
Optimal Time ◽  
Inoculum Concentration ◽  
Time Of Application ◽  
Sour Rot ◽  
Green Mold ◽  
Highly Effective ◽  
Moderately Resistant

Few postharvest treatments are available for managing sour rot of citrus caused by Galactomyces citri-aurantii and they are generally not very effective. The demethylation-inhibiting (DMI) triazole fungicides propiconazole and cyproconazole were found to be highly effective and more efficacious than other DMIs evaluated, such as metconazole and tebuconazole, in reducing postharvest sour rot of citrus. Additional studies were conducted with propiconazole as a postharvest treatment because it has favorable toxicological characteristics for food crop registration in the United States and the registrant supports a worldwide registration. Regression and covariance analyses were performed to determine optimal time of application after inoculation and fungicide rate. In laboratory studies, decay incidence increased when propiconazole applications were delayed from 8 to 24 h (lemon) or 18 to 42 h (grapefruit) after inoculation. Effective rates of the fungicide were 64 to 512 μg/ml and were dependent on inoculum concentration of the sour rot pathogen and on the type of citrus fruit. Propiconazole was found to be compatible with sodium hypochlorite at 100 μg/ml and 1 to 3% sodium bicarbonate without loss of efficacy for decay control on lemon. The addition of hydrogen peroxide/peroxyacetic acid at 80 μg/ml slightly decreased the effectiveness of propiconazole. Heated (48°C) solutions of propiconazole did not significantly improve the efficacy compared with solutions at 22°C. In experimental packing-line studies, aqueous in-line drenches applied alone or followed by applications of the fungicide in storage or packing fruit coatings were highly effective, reducing sour rot to between 0 and 1.2% compared with 83.8% decay incidence in the control when treatments were made up to 16 h after inoculation. When the fungicide was applied in either fruit coating, decay was only reduced to 49.1 to 57.1% incidence. Tank mixtures of propiconazole with the citrus postharvest fungicides fludioxonil and azoxystrobin were highly effective in reducing green mold caused by isolates of Penicillium digitatum sensitive or moderately resistant to imazalil and sour rot. Propiconazole will be an important postharvest fungicide for managing sour rot of citrus and potentially can be integrated into current management practices to reduce postharvest crop losses caused by DMI-sensitive isolates of P. digitatum.

Potassium Phosphite Mixed with Other Fungicides Reduces Yield Loss to Downy Mildew on Collard

2010 ◽  
Vol 11 (1) ◽  
pp. 10
Author(s):  
Anthony P. Keinath
Keyword(s):  
Downy Mildew ◽  
Yield Loss ◽  
Control Strategies ◽  
Southeastern United States ◽  
Production Costs ◽  
Water Control ◽  
Economic Return ◽  
Potassium Phosphite ◽  
Full Rate ◽  
Reduced Rate

Downy mildew of collard occurs frequently in the southeastern United States, and fungicides have become an essential part of economical control strategies for the disease. Fungicides were evaluated in 2007 and 2008 either alone or combined with a reduced rate (2 pt/acre) of potassium phosphite. Two formulations of potassium phosphite also were tested alone at the full rate (4 pt/acre). Presidio, Presidio plus Pro-Phyt (2007) or K-Phite (2008), K-Phite, Amistar plus ProPhyt, and Aliette reduced downy mildew severity at the final rating and also reduced AUDPC over the two years. Presidio plus potassium phosphite and Amistar plus ProPhyt increased the weight of healthy leaves and stems over the water control and also increased economic return calculated after fungicide and other production costs were subtracted from the crop value. The yields with Ranman, Sonata, and Presidio applied in combination with potassium phosphite were 16% greater than with the fungicides applied alone. Potassium phosphite may be useful in a tank-mix with other fungicides applied to collard to prevent yield loss to downy mildew. Accepted for publication 7 July 2010. Published 23 August 2010.

scholarly journals Development of PCR Assays for the Identification of Species and Pathotypes of Elsinoë Causing Scab on Citrus

Plant Disease ◽  
2007 ◽  
Vol 91 (7) ◽  
pp. 865-870 ◽  
Author(s):  
J. W. Hyun ◽  
N. A. Peres ◽  
S.-Y. Yi ◽  
L. W. Timmer ◽  
K. S. Kim ◽  
...  
Keyword(s):  
Internal Transcribed Spacer ◽  
Sweet Orange ◽  
Random Amplified Polymorphic Dna ◽  
Its Region ◽  
The United States ◽  
Specific Primer ◽  
Identification Of Species ◽  
Orange Fruit ◽  
Pcr Assays ◽  
Primer Sets

Two scab pathogens of citrus, Elsinoë fawcettii and E. australis, cause citrus scab and sweet orange scab, respectively, and pathotypes of each species have been described. The two species cannot be readily distinguished by morphological or cultural characteristics and can be distinguished only by host range and the sequence of the internal transcribed spacer (ITS) region. In this study, random amplified polymorphic DNA (RAPD) assays clearly distinguished E. fawcettii and E. australis, and the sweet orange and natsudaidai pathotypes within E. australis also could be differentiated. We developed specific primer sets, Efaw-1 for E. fawcettii; Eaut-1, Eaut-2, Eaut-3, and Eaut-4 for E. australis; and EaNat-1 and EaNat-2 for the natsudaidai pathotype within E. australis using RAPD products unique to each species or pathotype. Other primer sets, Efaw-2 and Eaut-5, which were specific for E. fawcettii and E. australis, respectively, were designed from previously determined ITS sequences. The Efaw-1 and Efaw-2 primer sets successfully identified E. fawcettii isolates from Korea, Australia, and the United States (Florida) and the Eaut-1 to Eaut-5 primer sets identified both the sweet orange pathotype isolates of E. australis from Argentina and the natsudaidai pathotype isolates from Korea. The EaNat-1 and EaNat-2 primer sets were specific for isolates of the natsudaidai pathotype. The Efaw-1 and Efaw-2 primer sets successfully detected E. fawcettii from lesions on diseased leaves and fruit from Korea and primer pairs Eaut-1, Eaut-2, Eaut-3, Eaut-4, and Eaut-5 detected E. australis from lesions on sweet orange fruit from Brazil.

scholarly journals First Report of Colletotrichum capsici Causing Postharvest Anthracnose on Papaya in South Florida

Plant Disease ◽  
2010 ◽  
Vol 94 (8) ◽  
pp. 1065-1065 ◽  
Author(s):  
T. L. B. Tarnowski ◽  
R. C. Ploetz
Keyword(s):  
The United States ◽  
South Florida ◽  
Plant Diseases ◽  
Water Control ◽  
Single Spore ◽  
Tropical Fruit ◽  
Sterile Needle ◽  
Research And Education ◽  
Production Areas ◽  
The University

Postharvest anthracnose of papaya, Carica papaya, is an important disease in most production areas worldwide (2). Colletotrichum gloeosporioides causes two types of anthracnose symptoms on papaya: (i) circular, sunken lesions with pink sporulation; and (ii) sharply defined, reddish brown and sunken lesions, described as ‘chocolate spot’ (2). Colletorichum spp. were isolated from lesions of the first type on papaya fruit from the University of Florida Tropical Research and Education Center, Homestead in December 2007 and from fruit imported from Belize in March 2008 (4). Single-spore isolates were identified using colony morphology and internal transcribed spacer (ITS) and mating type (MAT1-2) sequences. Two taxa were identified in both locations: (i) C. gloeosporioides (MAT1-2; GenBank Nos. GQ925065 and GQ925066) with white-to-gray, fluffy colonies with orange sporulation and straight and cylindrical conidia; and (ii) C. capsici (ITS; GenBank Nos. GU045511 to GU045514) with sparse, fluffy, white colonies with setose acervuli and falcate conidia. In addition, in Florida, a Glomerella sp. (ITS; GenBank Nos. GU045518 and GU045520 to GU045522) was recovered with darkly pigmented colonies that produced fertile perithecia after 7 to 10 days on potato dextrose agar (PDA). In each of three experiments, mature fruit (cv. Caribbean Red) were wounded with a sterile needle and inoculated with a 15-μl drop of 0.3% water agar that contained 105 conidia ml–1 of representative isolates of each taxon. The diameters of developing lesions were measured after 7 days of incubation in the dark at 25°C, and the presence of inoculated isolates was confirmed by their recovery from lesion margins on PDA. In all experiments, C. capsici and C. gloeosporioides produced lesions that were significantly larger than those that were caused by the water control and Glomerella sp. (respectively, approximately 12, 17, 0, and <1 mm in diameter). C. gloeosporioides produced sunken lesions with dark gray centers and pink/gray sporulation, which match those previously described for anthracnose on papaya (2). In contrast, C. capsici produced dark lesions due to copious setae of this pathogen; they resembled C. capsici-induced lesions on papaya that were reported previously from the Yucatan Peninsula (3). C. capsici has also been reported to cause papaya anthracnose in Asia (4), but to our knowledge, this is the first time it has been reported to cause this disease in Florida. Since it was also recovered from fruit that were imported from Belize, it probably causes anthracnose of papaya in that country as well. Another falcate-spored species, C. falcatum, was recovered from rotted papaya fruit in Texas (1). The Glomerella sp. was recovered previously from other hosts as an endophyte and causes anthracnose lesions on passionfruit (4). However, its role as a pathogen on papaya is uncertain since it was not pathogenic in the current work; the isolates that were recovered from papaya lesions may have colonized lesions that were caused by C. capsici and C. gloeosporioides. References: (1) Anonymous. Index of Plant Diseases in the United States. U.S. Dept. of Agric. Handb. No. 165. Washington, D.C., 1960. (2) D. M. Persley and R. C. Ploetz. Page 373 in: Diseases of Tropical Fruit Crops. R. C. Ploetz, ed. CABI Publishing. Wallingford, UK, 2003. (3) R. Tapia-Tussell et al. Mol Biotechnol 40:293, 2008. (4) T. L. Tarnowski. Ph.D. diss. University Florida, Gainesville, 2009.

A Completely Star Performance?

2014 ◽  
Vol 21 (2) ◽  
pp. 109-133
Author(s):  
Peter Mauch
Keyword(s):  
United States ◽  
British Empire ◽  
Public Diplomacy ◽  
The United States ◽  
Nazi Germany ◽  
Australian Government ◽  
Delicate Balance ◽  
The Pacific ◽  
Highly Effective ◽  
The Face

The Australian government in January 1940 appointed Richard Gardiner Casey minister to the United States. He sought both U.S. support for Britain in its war against Nazi Germany, and a U.S. guarantee to preserve Australian security in the face of an aggressive and threatening Japan. When Casey’s mission ended in March 1942, the United States had entered war in both the Atlantic and the Pacific. The limits to Casey’s ministerial influence were such, however, that one hardly can credit him with having delivered U.S. belligerency. The existing literature nonetheless locates merit in Casey’s ministerial mission, particularly in his highly effective public diplomacy and also in his ability to remain abreast of key U.S. decisions and strategy. This essay takes no particular issue with these findings. Instead, it finds value elsewhere in Casey’s mission, and in particular in the delicate balance he struck between his twin loyalties, to both Australia and the British Empire. It also departs from the existing literature insofar as it identifies a number of issues and episodes that call into question Casey’s accomplishments and acumen.

scholarly journals Effect of exterior wood coatings on the durability of cross-laminated timber against mold and decay fungi

BioResources ◽  
2020 ◽  
Vol 15 (4) ◽  
pp. 8420-8433
Author(s):  
Gabrielly S. Bobadilha ◽  
C. Elizabeth Stokes ◽  
Grant Kirker ◽  
Sheikh Ali Ahmed ◽  
Katie M. Ohno ◽  
...  
Keyword(s):  
Brown Rot ◽  
Acrylic Resin ◽  
Water Repellency ◽  
The United States ◽  
Mold Growth ◽  
Decay Fungi ◽  
Cross Laminated Timber ◽  
Dimensional Changes ◽  
Weight Losses ◽  
Rhizopus Sp

Cross-laminated timber (CLT) is increasingly used in building construction worldwide. Durability of CLT against fungal attack has yet to be fully explored. Water intrusion in mass timber can yield dimensional changes and microbial growth. This study evaluated the performance of CLT coated with various water- and solvent-based stains commercially available in the United States. Twelve coatings were tested for moisture excluding effectiveness, water repellency effectiveness, volumetric swelling, and anti-swelling efficiency. Only five coatings repelled water, limiting dimensional changes. A modified version of AWPA E10-16 (2016) was performed to evaluate decay of the coated CLT samples. Weight losses were recorded after 18 weeks’ exposure to the brown-rot decay fungus Gloeophyllum trabeum. In accelerated mold testing, coated CLT samples were grown in chambers containing spores of Aspergillus sp., Rhizopus sp., and Penicillium sp. for 29 d and assessed visually for mold growth. In both tests, coating C (transparent, water-based, alkyd/acrylic resin) performed the best among the tested coatings. Mold growth was completely prevented, and weight loss caused by G. trabeum was approximately 1.33%. Although coating C prevented decay for 18 weeks, coatings are not intended to protect against decay fungi. However, they may offer short-term protection during transport, storage, and construction.

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