scholarly journals Tilletia walkeri on Annual Ryegrass in Wheat Fields in the Southeastern United States

Plant Disease ◽  
1999 ◽  
Vol 83 (7) ◽  
pp. 685-689 ◽  
Author(s):  
Barry M. Cunfer ◽  
Lisa A. Castlebury
Keyword(s):  
United States ◽  
Lolium Multiflorum ◽  
Southeastern United States ◽  
Karnal Bunt ◽  
Annual Ryegrass ◽  
Wheat Seed ◽  
Tilletia Indica ◽  
Wheat Field ◽  
South Central ◽  
Low Levels

Surveys for Tilletia walkeri on annual ryegrass (Lolium multiflorum) were conducted during 1997 and 1998 in the southeastern United States, where suspect teliospores of the Karnal bunt fungus, Tilletia indica, were found in USDA-APHIS surveys of wheat (Triticum aestivum) seed in 1996. T. walkeri is morphologically similar to T. indica. Annual ryegrass is a common weed in wheat fields in the southeastern United States. Between April and June 1997, ryegrass seed samples were collected from 190 fields of wheat in 47 counties in Georgia and from 26 fields in 17 counties in Alabama and south-central Tennessee. In 1998, 70 samples were collected from 40 counties in the same regions of the three states. The teliospores from these samples were 23 to 45 μm in diameter (average about 33 μm) and ranged from light brown to dark reddish brown. They had coarse, widely spaced cerebriform ridges on the surface and were surrounded by a gelatinous sheath. The ryegrass bunt was identified as the recently described species T. walkeri, occurring on ryegrass seed from Australia and Oregon. In 1997, teliospores of T. walkeri were found in 13 samples from eight counties in central Georgia and from one field in Tennessee. In 1998, more teliospores and bunted seeds were found, possibly due to frequent rain in the region throughout the flowering period for ryegrass. Teliospores were found in 26/70 of the samples, and among these, only a small number of bunted seed were found in 12 of 13/70 samples. In one wheat field in Morgan County, Georgia, about 50% of the ryegrass seed collected was partially bunted, and a small percentage was completely bunted. Fields with teliospores were widely distributed and generally matched the locations where teliospores were found in APHIS wheat seed surveys in 1996 to 1998. T. walkeri occurs at very low levels on ryegrass in the Southeast and is the source of teliospores, initially identified as those of T. indica, associated with wheat seed in APHIS surveys. No bunted wheat seeds or teliospores of T. indica were found in the survey.

scholarly journals Invasion Pathways of Karnal Bunt of Wheat into the United States

Plant Disease ◽  
2003 ◽  
Vol 87 (8) ◽  
pp. 999-1003 ◽  
Author(s):  
David Marshall ◽  
Timothy T. Work ◽  
Joseph F. Cavey
Keyword(s):  
United States ◽  
El Paso ◽  
Weather Conditions ◽  
The United States ◽  
Karnal Bunt ◽  
Border Crossings ◽  
Tilletia Indica ◽  
Invasion Pathways ◽  
Established Disease ◽  
Made In

Karnal bunt of wheat (caused by Tilletia indica) was first detected in the United States in Arizona in 1996. The seed lots of infected, spring-habit, durum wheat associated with the initial detection were traced to planted fields in California, Arizona, New Mexico, and Texas. However, in the summer of 1997, the disease appeared in unrelated, winter-habit, bread wheat located over 700 km from the nearest potentially contaminated wheat from 1996 (and destroyed prior to reinfection). Here, we examined potential invasion pathways of the fungus associated with the movement of wheat into the United States. We analyzed the USDA/APHIS Port Information Network (PIN) database from 1984 through 2000 to determine likely pathways of introduction based on where, when, and how the disease was intercepted coming into the United States. All interceptions were made on wheat transported from Mexico, with the majority (98.8%) being intercepted at land border crossings. Karnal bunt was not intercepted from any other country over the 17-year period analyzed. Most interceptions were on wheat found in automobiles, trucks, and railway cars. The majority of interceptions were made at Laredo, Brownsville, Eagle Pass, and El Paso, TX, and Nogales, AZ. Karnal bunt was intercepted in all 17 years; however, interceptions peaked in 1986 and 1987. Averaged over all years, more interceptions (19.2%) were made in the month of May than in any other month. Our results indicate that Karnal bunt has probably arrived in the United States on many occasions, at least since 1984. Because of the relatively unaggressive nature of the disease and its reliance on rather exacting weather conditions for infection, we surmised that it is possible this disease has a long period of latent survival between initial arrival and becoming a thriving, established disease.

Breeding a heat‐tolerant annual ryegrass for earlier fall planting in the southeastern United States

Crop Science ◽  
2020 ◽  
Vol 60 (2) ◽  
pp. 830-840
Author(s):  
Eric D. Billman ◽  
Jesse I. Morrison ◽  
Brian S. Baldwin
Keyword(s):  
United States ◽  
Southeastern United States ◽  
Annual Ryegrass ◽  
Heat Tolerant

scholarly journals Frequency and Pathogenicity of Dematiaceous Hyphomycetes on Annual Ryegrass Overseeded on Bermudagrass in Mississippi

Plant Disease ◽  
2006 ◽  
Vol 90 (8) ◽  
pp. 1085-1090 ◽  
Author(s):  
R. G. Pratt
Keyword(s):  
United States ◽  
North American ◽  
Fungal Pathogens ◽  
Cynodon Dactylon ◽  
Southeastern United States ◽  
Axenic Culture ◽  
Warm Season ◽  
Application Site ◽  
Annual Ryegrass ◽  
Dematiaceous Hyphomycetes

Fungal diseases of annual ryegrass (Lolium multiflorum Lam.), a cool-season species grown for forage and turf in the southeastern United States, and bermudagrass (Cynodon dactylon (L.) Pers.), a warm-season perennial, usually are considered distinct. In May 2002 and 2004, symptoms of leaf and stem necrosis were observed simultaneously in forage bermudagrass and overseeded annual ryegrass on a swine waste application site in Mississippi. Sporulation by nine species of Bipolaris, Curvularia, Drechslera, and Exserohilum was observed on symptomatic leaves of ryegrass that were surface disinfested and plated on agar each year, and axenic cultures were established by spore transfers. These isolations represent four new worldwide and two new North American records of occurrence of fungal pathogens on ryegrass, and three new records for the southeastern United States and Mississippi. Bipolaris cynodontis, a common bermudagrass pathogen, and Drechslera dictyoides were observed most frequently on ryegrass during both years. In excised leaves of ryegrass inoculated with infested agar discs, most isolates of B. cynodontis from ryegrass and bermudagrass were equally virulent and caused necrosis equal to or greater than that caused by D. dictyoides, an established ryegrass pathogen. Isolates of B. cynodontis from both hosts also caused similar symptoms in foliage of ryegrass and bermudagrass following spore inoculations. Pathogenicity to ryegrass of five other species of dematiaceous hyphomycetes that represented new worldwide or North American records of occurrence also was demonstrated by foliar inoculations. All pathogens were reisolated from symptomatic tissues and grown in axenic culture for fulfillment of Koch's postulates. Results demonstrate that most of the same species of dematiaceous hyphomycetes infect both forage ryegrass and bermudagrass in Mississippi and indicate that B. cynodontis, in particular, may be a common and virulent pathogen of ryegrass in the southeastern United States.

Soybean Looper and Cabbage Looper (Lepidoptera: Noctuidae) Populations in Cotton and Soybean Cropping Systems in Mississippi

2002 ◽  
Vol 37 (3) ◽  
pp. 227-235 ◽  
Author(s):  
Douglas J. Jost ◽  
Henry N. Pitre
Keyword(s):  
United States ◽  
Trichoplusia Ni ◽  
Cropping Systems ◽  
Southeastern United States ◽  
Cabbage Looper ◽  
Pheromone Traps ◽  
Growing Seasons ◽  
Low Levels ◽  
Soybean Looper ◽  
Lepidoptera Noctuidae

Colonization and abundance of soybean looper, Pseudoplusia includens (Walker), and cabbage looper, Trichoplusia ni (Hübner), adults and larvae were monitored in cotton and soybean cropping systems in the Delta region of Mississippi for three growing seasons (1994–1996). Soybean looper and cabbage looper adults were initially observed in pheromone traps during the last week of May or first week of June, although adults may have been present in the collection area prior to trap establishment. Adult populations of both species remained low until early August, after which moth density increased coincident with the bloom stages of cotton and soybean. Larvae were first collected from the crops when plants were in bloom, with the greatest increase in population density occurring in early to mid-August. Although samples were not taken after mid-August, looper populations generally decline to low levels during September in Mississippi. More soybean looper larvae usually were collected from soybean than in cotton, whereas fewer cabbage looper larvae were collected from soybean than cotton. Cabbage looper larvae were collected in soybean on the same sample date in 1995, but approximately 5 wk after soybean looper larvae in 1996. The occurrence of soybean and cabbage loopers in cotton and soybean agroecosystems in Mississippi appears to be similar to patterns of activity recorded for these insects 20 to 40 years ago in other areas of the southeastern United States.

scholarly journals Utilization of Soil Solarization for Eliminating Viable Tilletia indica Teliospores from Arizona Wheat Fields

Plant Disease ◽  
2008 ◽  
Vol 92 (12) ◽  
pp. 1604-1610 ◽  
Author(s):  
G. L. Peterson ◽  
K. L. Kosta ◽  
D. L. Glenn ◽  
J. G. Phillips
Keyword(s):  
Management Strategies ◽  
Soil Solarization ◽  
Karnal Bunt ◽  
Daily Maximum ◽  
Rapid Decline ◽  
United States Department ◽  
Tilletia Indica ◽  
Wheat Field ◽  
Soil Temperatures ◽  
Clear Plastic

Studies were conducted in Arizona to determine the efficacy of soil solarization for killing teliospores of the soilborne fungal wheat pathogen Tilletia indica. In a replicated study conducted in each of 3 years, T. indica teliospores and bunted wheat kernels were buried in a Karnal bunt-infested wheat field at depths of 5, 10, and 20 cm. Replicate samples were removed from under a clear plastic solarization cover at 7-day intervals and the number of viable teliospores determined. A rapid decline in teliospore viability occurred at all treatment depths over 38 days, with efficacy comparable with methyl bromide protocols using clear plastic sheeting. Initial viability rates of 43, 71, and 82% germination were reduced to 0.1, 7.7, and 0.2% after 38 days (across all depths) in 2003, 2005, and 2006, respectively. Mean daily maximum soil temperatures at 5 and 20 cm under clear plastic in 2003, 2005, and 2006 were 67, 53 and 60°C and 43, 38, and 43°C, respectively. Under current United States Department of Agriculture disease management strategies, the method may be useful for the rapid deregulation of Karnal bunt-affected fields.

scholarly journals Distribution and Recovery of Tilletia indica Teliospores from Regulated Wheat Fields in Texas

Plant Disease ◽  
2008 ◽  
Vol 92 (3) ◽  
pp. 344-350 ◽  
Author(s):  
T. W. Allen ◽  
H. W. Maples ◽  
F. Workneh ◽  
J. M. Stein ◽  
C. M. Rush
Keyword(s):  
Grid Point ◽  
The United States ◽  
Karnal Bunt ◽  
Tilletia Indica ◽  
Soil Factors ◽  
Wheat Field ◽  
Contour Maps ◽  
Grid Points ◽  
Single Field ◽  
Analyze Data

Eight wheat fields from the Karnal bunt-regulated regions within Texas were grid sampled to gain a better understanding of the ecology and epidemiology of teliospores produced by the causal agent, Tilletia indica. Teliospores from 25-g aliquots of soil from each grid point were extracted using a size-selective sieving sucrose-centrifugation procedure. Teliospores were recovered from all eight fields and, in some cases, from every grid point within a field. Total teliospore numbers ranged from 0 to 1,305 per 25 g of soil. Over 70% of the total grid sampled points contained one or more teliospores. The relation between soil chemical and physical characteristics and teliospore numbers from each field was evaluated. In general, no consistent, significant trend could be made between soil factors and teliospore numbers. Geostatistics were used to analyze data from grid points and create contour maps. Teliospore distribution was aggregated in four of the fields, random in three of the fields, and discontinuous (neither random nor aggregated) in a single field. This is the first report of widespread distribution and high teliospore numbers from wheat field soils in the United States.

scholarly journals Risk Assessment for Karnal Bunt Occurrence in the Pacific Northwest

Plant Disease ◽  
1997 ◽  
Vol 81 (6) ◽  
pp. 689-692 ◽  
Author(s):  
Richard W. Smiley
Keyword(s):  
United States ◽  
Risk Assessment ◽  
Pacific Northwest ◽  
The United States ◽  
Climatic Conditions ◽  
Karnal Bunt ◽  
Climate Data ◽  
Tilletia Indica ◽  
The Past ◽  
The Pacific

Tilletia indica, the causal agent of Karnal bunt of wheat, was first detected and reported in the United States in 1996. Karnal bunt occurred in the southwestern United States as early as 1992. Wheat contaminated with teliospores of T. indica is likely to have been transported from the Southwest to other regions, including the Pacific Northwest, before presence of the pathogen was discovered. Teliospore and sporidial germination and infection are highly dependent on climatic conditions. The potential for T. indica to infect wheat in the Pacific Northwest has not been reported. The objective of this study was to use published information on environmental factors favorable for infection and historical climate data for the Pacific Northwest to analyze the environmental risk for Karnal bunt to occur if wheat fields in the Pacific Northwest become contaminated by T. indica. Conditions during the past four decades appeared favorable for infection in nonirrigated wheat during 1 of every 3 years at two (Corvallis, OR, and Spokane, WA) of 13 Idaho, Oregon, and Washington locations examined, and every year at all locations where wheat is irrigated. If introduced to the area, it appears possible for T. indica to become established in selected regions of the Pacific Northwest.

scholarly journals Susceptibility of Wheat to Tilletia indica During Stages of Spike Development

2006 ◽  
Vol 96 (9) ◽  
pp. 962-966 ◽  
Author(s):  
Blair J. Goates ◽  
Eric W. Jackson
Keyword(s):  
Karnal Bunt ◽  
Growth Stages ◽  
Optimal Conditions ◽  
Tilletia Indica ◽  
Airborne Inoculum ◽  
Yield And Quality ◽  
Spike Development ◽  
Low Levels ◽  
Dough Stage ◽  
Different Growth Stages

Karnal bunt of wheat is caused by the fungus Tilletia indica, which partially converts kernels into sori filled with teliospores. Despite minor overall yield and quality losses, the disease is of considerable international quarantine concern. Plant development stages reported susceptible to infection vary considerably. A study was designed to better define the susceptibility period by inoculating wheat spikes at different growth stages with naturally liberated secondary sporidia under optimal conditions for disease development. Spikes of a resistant and susceptible cultivar were inoculated at eight growth stages from awns emerging to soft dough. Spikes became susceptible only after emerging from the boot and continued to be susceptible up to soft dough stage at which low levels of disease occurred. Disease severity in both cultivars peaked when spikes were inoculated after complete emergence, but before the onset of anthesis. Disease levels tapered off gradually in spikes inoculated after anthesis. The results broaden the known susceptibility period of wheat to T. indica to include stages long after anthesis, and indicate that infection from airborne inoculum is not possible during boot or awns emerging stages, which are commonly referred to as the most susceptible stages.

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