Meta-Analysis of the Effects of QoI and DMI Fungicide Combinations on Fusarium Head Blight and Deoxynivalenol in Wheat.

Field trials were conducted in 17 U.S. states to evaluate the effects of quinone outside inhibitor (QoI) and demethylation inhibitor (DMI) fungicide programs on Fusarium head blight index (IND) and deoxynivalenol (DON) toxin in wheat. Four DMI-only treatments applied at Feekes 10.5.1, five QoI-only treatments applied between Feekes 9 or Feekes 10.5, three QoI+DMI mixtures applied at Feekes 10.5, and three treatments consisting of a QoI at Feekes 9 followed by a DMI at Feekes 10.5.1 were evaluated. Network meta-analytical models were fitted to log-transformed mean IND and DON data and estimated contrasts of log means were used to obtain estimates of mean percent controls relative to the nontreated check as measures of efficacy. Results from the meta-analyses were also used to assess the risk of DON increase in future trials. DMI at Feekes 10.5.1 were the most effective programs against IND and DON and the least likely to increase DON in future trials. QoI-only programs increased mean DON over the nontreated checks and were the most likely to do so in future trials, particularly when applied at Feekes 10.5. The effects of QoI+DMI combinations depended on the active ingredients and whether the two were applied as a mixture at heading or sequentially. Following a Feekes 9 QoI application with a Feekes 10.5.1 application of a DMI reduced the negative effect of the QoI on DON but was not sufficient to achieve the efficacy of the Feekes 10.5.1 DMI-only treatments. Our results suggest that one must be prudent when using QoI treatments under moderate to high risk of FHB, particularly where the QoI is used without an effective DMI applied in combination or in sequence.

Revisiting Fungicide-Based Management Guidelines for Leaf Blotch Diseases in Soft Red Winter Wheat.

Standard foliar fungicide applications in wheat are usually made between flag leaf emergence (Feekes [FK] 8) and heading (FK10.5) to minimize damage to the flag leaf. However, over the last few years, new fungicide programs such as applications prior to FK8 and split half-rate applications have been implemented, although there are few data pertaining to the efficacy of these programs. Eight experiments were conducted in Illinois, Indiana, Ohio, and Wisconsin from 2010 to 2012 to compare new programs to standard FK8 and FK10 programs in terms of disease control and yield response. The programs evaluated consisted of single full-rate applications of 19% tebuconazole + 19% prothioconazole (Prosaro) or 23.6% pyraclostrobin (Headline) at FK5 (pseudostem strongly erected), FK8, or FK10, or split half rates at FK5 and 8 (FK5+8), plus an untreated check (CK). Leaf blotch (LB) severity and yield data were collected and random effects meta-analytical models fitted to estimate the overall log odds ratio of disease reaching the flag leaf ( L¯OR ) and mean yield increase ( D¯ ) for each fungicide program relative to CK. For all programs, L¯OR was significantly different from zero (P < 0.05). Based on estimated odds ratios (OR = exp[ L¯OR ]), the two FK8 programs reduced the risk of LB reaching the flag leaf by 55 and 75%, compared with 62 and 69% and 67 and 70% for the two FK10 and FK5+8 programs, respectively, and only 32 and 37% for the two FK5 programs. D¯ was significantly different from zero (P ≤ 0.003) for all FK8, FK10, and FK5+8 programs, with values of 233 and 245, 175 and 220, and 175 and 187 kg ha-1 for the FK10, FK5+8, and FK8 programs, respectively. Differences in mean yield response between Headline and Prosaro were not statistically significant (P > 0.05). The probability of profitability was estimated for each program for a range of grain prices and fungicide application costs. All FK8, FK10, and FK5+8 programs had more than an 80% chance of resulting in a positive yield response, compared with 63 and 67% for the two FK5 programs. The chance of obtaining a yield increase of 200 kg ha-1, required to offset an application cost of $36 ha-1 at a grain price of $0.18 kg-1, ranged from 44 to 60% for FK8, FK10 and FK5+8 programs compared with 22 and 25% for the two FK5 programs. These findings could be used to help inform fungicide application decisions for LB diseases in soft red winter wheat.

Development of Molecular Assays for Detection of Stenocarpella maydis and Stenocarpella macrospora in Corn.

The causal agents of Diplodia ear rot are two species of the Stenocarpella genus, S. macrospora and S. maydis. In addition to ears, both pathogens can infect leaves and stalks, and both are present in most corn-production regions around the world. It is difficult to visually distinguish between the two pathogens based on plant symptoms and fungal signs. To facilitate accurate and rapid pathogen identification, polymerase chain reaction (PCR) assays were developed for identification of each species. Species-specific primers of 18 to 20 nucleotides in length were designed, targeting a portion of the internal transcribed spacer (ITS) region of the fungal genome for conventional and real-time PCR assays. The conventional PCR method successfully amplified a single 1.7-kb and 800-bp fragment for each S. maydis and S. macrospora isolate, respectively. The real-time method was performed using SYBR green dye, and detection of each specific target pathogen was successfully obtained. In total, 82 S. maydis and 15 S. macrospora isolates were tested to evaluate the reproducibility of these primers. Both methods provide a rapid and specific tool for the detection of Stenocarpella spp.

A Coordinated Effort to Manage Soybean Rust in North America: A Success Story in Soybean Disease Monitoring.

Existing crop monitoring programs determine the incidence and distribution of plant diseases and pathogens and assess the damage caused within a crop production region. These programs have traditionally used observed or predicted disease and pathogen data and environmental information to prescribe management practices that minimize crop loss. Monitoring programs are especially important for crops with broad geographic distribution or for diseases that can cause rapid and great economic losses. Successful monitoring programs have been developed for several plant diseases, including downy mildew of cucurbits, Fusarium head blight of wheat, potato late blight, and rusts of cereal crops. A recent example of a successful disease-monitoring program for an economically important crop is the soybean rust (SBR) monitoring effort within North America. SBR, caused by the fungus Phakopsora pachyrhizi, was first identified in the continental United States in November 2004. SBR causes moderate to severe yield losses globally. The fungus produces foliar lesions on soybean (Glycine max) and other legume hosts. P. pachyrhizi diverts nutrients from the host to its own growth and reproduction. The lesions also reduce photosynthetic area. Uredinia rupture the host epidermis and diminish stomatal regulation of transpiration to cause tissue desiccation and premature defoliation. Severe soybean yield losses can occur if plants defoliate during the mid-reproductive growth stages. The rapid response to the threat of SBR in North America resulted in an unprecedented amount of information dissemination and the development of a real-time, publicly available monitoring and prediction system known as the Soybean Rust-Pest Information Platform for Extension and Education (SBR-PIPE). The objectives of this article are (i) to highlight the successful response effort to SBR in North America, and (ii) to introduce researchers to the quantity and type of data generated by SBR-PIPE. Data from this system may now be used to answer questions about the biology, ecology, and epidemiology of an important pathogen and disease of soybean.

Meta-analysis of yield response of hybrid field corn to foliar fungicides in the U.S. Corn Belt.

The use of foliar fungicides on field corn has increased greatly over the past 5 years in the United States in an attempt to increase yields, despite limited evidence that use of the fungicides is consistently profitable. To assess the value of using fungicides in grain corn production, random-effects meta-analyses were performed on results from foliar fungicide experiments conducted during 2002 to 2009 in 14 states across the United States to determine the mean yield response to the fungicides azoxystrobin, pyraclostrobin, propiconazole + trifloxystrobin, and propiconazole + azoxystrobin. For all fungicides, the yield difference between treated and nontreated plots was highly variable among studies. All four fungicides resulted in a significant mean yield increase relative to the nontreated plots (P < 0.05). Mean yield difference was highest for propiconazole + trifloxystrobin (390 kg/ha), followed by propiconazole + azoxystrobin (331 kg/ha) and pyraclostrobin (256 kg/ha), and lowest for azoxystrobin (230 kg/ha). Baseline yield (mean yield in the nontreated plots) had a significant effect on yield for propiconazole + azoxystrobin (P < 0.05), whereas baseline foliar disease severity (mean severity in the nontreated plots) significantly affected the yield response to pyraclostrobin, propiconazole + trifloxystrobin, and propiconazole + azoxystrobin but not to azoxystrobin. Mean yield difference was generally higher in the lowest yield and higher disease severity categories than in the highest yield and lower disease categories. The probability of failing to recover the fungicide application cost (p(loss)) also was estimated for a range of grain corn prices and application costs. At the 10-year average corn grain price of $0.12/kg ($2.97/bushel) and application costs of $40 to 95/ha, p(loss) for disease severity <5% was 0.55 to 0.98 for pyraclostrobin, 0.62 to 0.93 for propiconazole + trifloxystrobin, 0.58 to 0.89 for propiconazole + azoxystrobin, and 0.91 to 0.99 for azoxystrobin. When disease severity was >5%, the corresponding probabilities were 0.36 to 95, 0.25 to 0.69, 0.25 to 0.64, and 0.37 to 0.98 for the four fungicides. In conclusion, the high p(loss) values found in most scenarios suggest that the use of these foliar fungicides is unlikely to be profitable when foliar disease severity is low and yield expectation is high.

Resistance to QoI Fungicides in Ascochyta rabiei from Chickpea in the Northern Great Plains.

Ascochyta blight, caused by Ascochyta rabiei (teleomorph: Didymella rabiei), is an important fungal disease of chickpea (Cicer arietinum). A monitoring program was established in 2005 to determine the sensitivity of A. rabiei isolates to the QoI (strobilurin) fungicides azoxystrobin and pyraclostrobin. A total of 403 isolates of A. rabiei from the Northern Great Plains and the Pacific Northwest were tested. Ninety-eight isolates collected between 2005 and 2007 were tested using an in vitro spore germination assay to determine the effective fungicide concentration at which 50% of conidial germination was inhibited (EC50) for each isolate-fungicide combination. A discriminatory dose of 1 µg/ml azoxystrobin was established and used to test 305 isolates from 2006 and 2007 for in vitro QoI fungicide sensitivity. Sixty-five percent of isolates collected from North Dakota in 2005, 2006, and 2007 and from Montana in 2007 were found to exhibit a mean 100-fold decrease in sensitivity to both azoxystrobin and pyraclostrobin when compared to sensitive isolates, and were considered to be resistant to azoxystrobin and pyraclostrobin. Under greenhouse conditions, QoI-resistant isolates of A. rabiei caused significantly higher amounts of disease than sensitive isolates on azoxystrobin- or pyraclostrobin-amended plants. These results suggest that disease control may be inadequate at locations where resistant isolates are present.

Baseline Sensitivity of Ascochyta rabiei to Azoxystrobin, Pyraclostrobin, and Boscalid.

Ascochyta rabiei, causal agent of Ascochyta blight on chickpea (Cicer arietinum), can cause severe yield loss in the United States. Growers rely on applications of fungicides with site-specific modes of action such as the quinone outside inhibiting (QoI) fungicides azoxystrobin and pyraclostrobin, and the carboximide fungicide boscalid, to manage disease. In all, 51 isolates collected prior to QoI fungicide registration and 71 isolates collected prior to boscalid registration in the United States were tested in an in vitro assay to determine the effective fungicide concentration at which 50% of conidial germination was inhibited (EC50) for each isolate-fungicide combination. The effect of salicylhydroxamic acid (SHAM) on conidia of A. rabiei in the presence and absence of azoxystrobin also was assessed to determine whether the fungus is capable of using alternative respiration. Five of nine A. rabiei isolates tested had significantly higher (P ≤ 0.05) EC50 values when SHAM was not included in media amended with azoxystrobin, indicating that A. rabiei has the potential to use alternative respiration to overcome fungicide toxicity in vitro. EC50 values of azoxystrobin and pyraclostrobin ranged from 0.0182 to 0.0338 µg/ml and from 0.0012 to 0.0033 µg/ml, with mean values of 0.0272 and 0.0023 µg/ml, respectively. EC50 values of boscalid ranged from 0.0177 to 0.4960 µg/ml, with a mean of 0.1903 µg/ml. Establishment of these baselines is the first step in developing a monitoring program to determine whether shifts in sensitivity to these fungicides are occurring in the A. rabiei pathogen population.

First Report of Pink Seed of Pea Caused by Erwinia rhapontici in North Dakota.

In 2006, a seed lot of dry pea cv. DS Admiral obtained from Bowman County, North Dakota contained seed with bright-to-pale pink discoloration on the seed coat. Five discolored seeds and five seeds with normal appearance were surface disinfected in a 0.5% NaOCl solution for 1 min and rinsed with sterilized distilled water for 1 min. Seeds were placed onto potato dextrose agar (PDA) and incubated at 22°C. Three days later, the discolored seeds produced pink bacterial colonies and a pink pigment that diffused throughout the PDA. The pink bacterial colonies were tentatively identified as Erwinia rhapontici on the basis of colony and pigment color (2,3). No fungi or bacteria grew from the seed with normal appearance. A pink bacterial colony growing from one of the discolored seeds was streaked onto PDA and a single colony was obtained. A streaked plate incubated at 37°C showed no growth, which distinguishes E. rhapontici from Brenneria rubrifaciens (formerly E. rubrifaciens) (1-3). To confirm the identity, the isolate was sent to the Bacterial Identification and Fatty Acid Analysis Laboratory at the University of Florida, Gainesville. Fatty acid analysis indicated a similarity index of 0.515 for E. rhapontici. For an additional confirmation of identity, the 16S ribosomal DNA (rDNA) gene was amplified from the E. rhapontici isolate with universal primers fD1 and rP1 (4). The PCR product was cloned into pGEM-T easy vector (Promega, Madison, WI) and sequenced with primers SP6 and T7 at the Keck Biotechnology Center at the University of Illinois, Urbana. The resulting nucleotide sequence was compared with 16S rDNA sequences deposited in the ribosomal database ( http://rdp.cme.msu.edu/seqmatch/seqmatch_intro.jsp ) and showed highest identity to sequences of E. rhapontici or E. persicinus strains. To confirm pathogenicity, the basal ends of five pods on each of six pea plants (cv. Carneval) were syringe injected with 0.1 ml of suspension containing the obtained E. rhapontici isolate in the greenhouse by the methods as previously described (2). As a control, five pods on each of two plants were injected with 0.1 ml of sterile distilled water. Twenty-eight of the 51 seeds obtained from the bacteria-inoculated pods had pink seed symptoms, while seeds from the control pods appeared normal. Isolations from symptomatic and asymptomatic seed were performed as described above, and E. rhapontici was obtained from symptomatic seed. To our knowledge, this is the first report of pink seed of pea caused by E. rhapontici in North Dakota. The first report of this disease on pea in the United States was from Montana (3). References: (1) L. Hauben et al. Syst. Appl. Microbiol. 21:384, 1998. (2) H. C. Huang et al. Can. J. Plant Pathol. 12:445, 1990. (3) B. K. Schroeder et al. Plant Dis. 86:188, 2002. (4) W. G. Weisburg et al. J. Bacteriol. 173:697, 1991.

High-level quinolone resistance in Neisseria gonorrhoeae: a report of two cases.

BACKGROUND AND OBJECTIVES: Fluoroquinolones are widely used oral agents for treating Neisseria gonorrhoeae. Resistance to these agents is sporadic and usually at a low level. Two instances of high-dose ciprofloxacin regimens failing in the treatment of gonococcal infection, caused by strains with high-level quinolone resistance, are reported. STUDY DESIGN: This is a case report. CONCLUSION: High-level resistance to quinolone antibiotics resulting in treatment failure was observed in two distinct gonococcal isolates from patients infected in the Philippines (ciprofloxacin; minimal inhibitory contribution = 16 mg/l). Continued monitoring of the quinolone sensitivity of Neisseria gonorrhoeae is appropriate and prudent.

Meningitis caused by Streptococcus pneumoniae showing high level resistance to penicillin.

A case of meningitis caused by a strain of Streptococcus pneumoniae (SPn) showing high level resistance to penicillin is described. The patient responded to a combination of high dose penicillin and ceftriaxone. After reviewing the Australian situation and the world literature, we propose that empiric treatment of SPn meningitis in Australia should consist of high dose penicillin plus a third generation cephalosporin, with appropriate modification once the identification of the organism and its susceptibilities are confirmed.

Two fatal infections in immunocompromised patients caused by Scedosporium inflatum.

Two fatal infections caused by Scedosporium inflatum in immunocompromised patients are described. One patient developed peritonitis with this fungus 3 mths post renal transplantation. After a stormy course in the intensive care unit he eventually died. The other patient was suffering from non-Hodgkin's lymphoma and showed persistent neutropenia. Progressive deterioration occurred, and disseminated fungal infection was found at post mortem. Both isolates were resistant to all commonly available antifungal agents.

Onychomycosis due to Pityrosporum.

Ten cases of onychomycosis due to Pityrosporum are reported. The epidemiology, clinical features and treatment of these cases are described in detail. These cases are reported to alert medical practitioners and mycologists that Pityrosporum can cause onychomycosis in our community.

Detection of teichoic acid antibodies in Staphylococcus aureus infections.

A commercially available agar gel diffusion (AGD) assay was used to investigate the teichoic acid antibody (TAA) response in 183 patients with proven Staphylococcus aureus (SA) infections. Two control groups were also investigated. One consisted of 100 hospitalized patients with a variety of medical and surgical conditions other than SA infection and the other consisted of 116 healthy hospital staff members. The sensitivity of the AGD assay varied markedly depending on the site of infection in the patients with proven SA infections. All patients with SA endocarditis developed positive TAA titres (greater than or equal to 1:4), although more than one third of these were initially negative. In patients with chronic osteomyelitis or septic arthritis, 41% had positive TAA titres, whereas no positive titres were detected in patients with acute osteomyelitis or septic arthritis. Lower rates of positive TAA titres were found in patients with deep abscesses (27%), pneumonia (14%) and post-operative infections (9%), but no positive titres occurred in patients with acute uncomplicated bacteremia, cellulitis or meningitis. In 100 hospitalized control patients, no positive titres were detected, and only 1 of 116 (0.9%) healthy hospital staff controls was positive. Suggested guidelines for the use of the AGD assay are discussed.

A fatal case of Vibrio vulnificus septicemia.

A fatal case of Vibrio vulnificus septicemia in a 60 yr old man is described. This man displayed many of the classical features seen in fulminant infections with this organism. The epidemiology of V. vulnificus infections is discussed in this report.

Acute flexor tenosynovitis caused by Streptococcus pneumoniae.

A case of acute flexor tenosynovitis caused by Streptococcus pneumoniae in a previously well male truck driver is described. The importance of specimen collection and processing in establishing a microbiological diagnosis is emphasized. Early surgical drainage and treatment with penicillin resulted in rapid resolution of the infection and a return to full function of the hand.

Epidemiological surveillance of Acinetobacter species.

Two hundred and sixty Acinetobacter isolates were recovered from 237 patients over a 2-year period; 156 isolates from 135 spinal cord injuries unit (SCIU) patients and 104 isolates from 102 patients in all the other hospital units. In SCIU patients, 133 isolates were recovered from the urine, 21 from wounds and aspirates, one from sputum and one from blood culture. In non-SCIU patients, 12 isolates were recovered from urine, 43 from wounds and aspirates, 48 from sputum and one from blood culture. Sixty-nine percent of isolates from SCIU patients showed resistance to gentamicin compared to 3% from non-SCIU patients. Gentamicin-resistant Acinetobacter anitratus was recovered from many environmental sites in the SCIU wards and from the hands of seven of 94 SCIU staff members tested. Serial rectal swabs were obtained from 79 newly-diagnosed SCIU patients. Ninety-two percent of those patients followed for up to 5 months acquired gentamicin-resistant Acinetobacter anitratus in their intestinal tract. API 2ONE profiles and antibiograms suggested that two distinct gentamicin-resistant strains of A. anitratus had become endemic in the SCIU and that nosocomial transmission was a frequent occurrence.

Peritonitis caused by Campylobacter jejuni and serologically confirmed in a patient being treated with continuous ambulatory peritoneal dialysis.

A case of Campylobacter jejuni peritonitis in a patient being treated with continuous ambulatory peritoneal dialysis is described. The significance of the organism isolated from our patient was initially doubtful because of a rapid defervescence of symptoms with minimal specific antibiotic therapy, lack of a preceding diarrhoeal illness and the time taken to isolate and identify the organism. Serial serum IgM, IgA and IgG antibody estimations clearly showed an acute seroconversion confirming that the strain of C. jejuni isolated was the causative organism in this case.