Pythium spp. associated with root rot and stunting of winter crops in North Carolina

Plant Disease ◽  
2021 ◽  
Author(s):  
Ella Reeves ◽  
James Patrick Kerns ◽  
Barbara Shew
Keyword(s):  
North Carolina ◽  
Winter Wheat ◽  
Cover Crops ◽  
Root Rot ◽  
Growing Seasons ◽  
Salvia Sclarea ◽  
Root Necrosis ◽  
Winter Crops ◽  
Eastern North Carolina ◽  
Isolated Species

Annual double-crop rotation systems that incorporate winter wheat, clary sage, or a cover crop are common in eastern North Carolina. Stunting and root rot of clary sage (Salvia sclarea L.) reduce yields of this crop, especially in wet soils. Stunting and reduced stand establishment also afflict winter cover crops, including rye, rapeseed, and winter pea. Pythium spp. are causal agents of root rot of winter wheat in this region, but their role in root rot and stunting of other winter crops is not understood. During the growing seasons of 2018-2019 and 2019-2020 samples of clary sage, rye, rapeseed, and winter pea displaying symptoms of stunting were collected across eastern NC, resulting in the recovery of 420 isolates of Pythium from the roots of all hosts. P. irregulare, P. spinosum, and the complex Pythium sp. cluster B2A were the most frequently isolated species from clary sage. P. irregulare and P. spinosum were aggressive pathogens of clary sage at 18°C, and caused moderate root rot at 28°C. Koch’s postulates confirmed that isolates belonging to Pythium sp. cluster B2A, P. sylvaticum, P. pachycaule, P aphanidermatum, P. myriotylum, and P. oopapillum are pathogens of clary sage. P. irregulare (37% of all isolates) and members of the species complex Pythium sp. cluster B2A (28% of all isolates) comprised the majority of isolates collected from all hosts and were the most frequently isolated species from rye, rapeseed, and winter pea. In pathogenicity assays, isolates representing P. irregulare and P. spinosum caused slight to moderate root necrosis on rye, rapeseed, and winter pea. Isolates representing Pythium sp. cluster B2A caused slight to moderate root necrosis on rapeseed and clary sage, but no symptoms on rye or winter pea.

Pythium spp. associated with root rot and stunting of winter wheat in North Carolina

Plant Disease ◽  
2020 ◽  
Author(s):  
Ella Reeves ◽  
James Patrick Kerns ◽  
Christina Cowger ◽  
Barbara Shew
Keyword(s):  
North Carolina ◽  
Winter Wheat ◽  
Root Rot ◽  
In Vitro Growth ◽  
Pythium Species ◽  
Nitrogen Application ◽  
Pythium Irregulare ◽  
Severe Stunting ◽  
Eastern North Carolina

In eastern North Carolina, mild to severe stunting and root rot have reduced yields of winter wheat, especially during years with abundant rainfall. Causal agents of root rot of wheat in this region were previously identified as Pythium irregulare, P. vanterpoolii, and P. spinosum. To investigate species prevalence, 114 isolates of Pythium were obtained from symptomatic wheat plants collected in 8 counties. Twelve species were recovered, with P. irregulare (32%), P. vanterpoolii (17%), and P. spinosum (16%) the most common. Pathogenicity screens were performed with selected isolates of each species, and slight to severe necrosis of young roots was observed. The aggressiveness of five isolates each of P. irregulare, P. vanterpoolii, and P. spinosum was compared on a single cultivar of wheat at 14°C, and very aggressive isolates were found within all species. In vitro growth of these isolates was measured at 14°C and 20°C, and all isolates grew faster at the warmer temperature. The effects of varying temperatures and rates of nitrogen on root rot caused by Pythium species alone or in combination were investigated. All inoculation treatments caused severe root rot under all conditions tested, and disease was more severe at 12/14°C compared to 18/20°C, but there was no effect of nitrogen application.

EFFECT OF COVER CROPS ON WINTER SURVIVAL, COMMON ROOT ROT, AND YIELD OF WINTER WHEAT

1962 ◽  
Vol 42 (2) ◽  
pp. 286-293 ◽  
Author(s):  
A. D. Smith ◽  
J. S. Horricks ◽  
J. E. Andrews
Keyword(s):  
Winter Wheat ◽  
Cover Crops ◽  
Root Rot ◽  
Cover Crop ◽  
Ammonium Phosphate ◽  
Winter Survival ◽  
Common Root ◽  
Common Root Rot

When four varieties of winter wheat (Yogo, Kharkov 22 M.C., Jones Fife, and Elgin) were sown into wheat, oat, or barley cover crops, the yields were lower than when they were sown on fallow. The yield of winter wheat sown into the different cover crops was highest in barley and lowest in wheat cover crop. When the growth of cover crops was abundant, the yield of winter wheat was reduced. Application of ammonium-phosphate-sulphate fertilizer (16-20-0) increased the yield of winter wheat and generally decreased the severity of common root rot. Winter survival was generally greater when winter wheat was sown into cover crops than when it was sown on fallow. Root rot was most severe in winter wheat sown into wheat cover and was progressively less severe when sown into fallow, barley, or oat cover. Neither blade-cultivating nor mowing the cover crop prior to seeding the winter wheat appreciably affected the yield.

scholarly journals Developing Cover Crops for Weed Control in Establishment Year for Strawberries

HortScience ◽  
1995 ◽  
Vol 30 (4) ◽  
pp. 820A-820
Author(s):  
Charlotte Herman ◽  
David Larson ◽  
Emily Hoover
Keyword(s):  
Winter Wheat ◽  
Cover Crops ◽  
Weed Management ◽  
Cover Crop ◽  
Plant Material ◽  
Weed Suppression ◽  
First Year ◽  
Growing Seasons ◽  
Stage Of Development ◽  
Soil Area

The goal of our program is to learn how to effectively establish first-year strawberry plantings without using herbicides. Before strawberry transplanting, four treatments were established: winter wheat, a dwarf Brassica sp., napropamide (2.24 kg·h–1) plus hand hoeing and rototilling, and no weed management. `Honeyoye' transplants were set into plots measuring 6.1 × 7.32 m on 21 May 1993 and 10 May 1994. Weekly data was taken on the percentage of soil area covered with plant material, height, and stage of development of plants, and weeds present. Weed transects and plant dry weights were done periodically during the growing seasons. The most promising cover crop treatment was the dwarf Brassica sp. for early season weed suppression because of rapid germination and short stature. Winter wheat was very competitive with the strawberry plants. The herbicide treatment had the largest inputs; however, it did produce the largest strawberry plants at the end of the season.

scholarly journals First Report of Cylindrocarpon sp. Associated with Root Rot Disease of Strawberry in North Carolina

Plant Disease ◽  
2013 ◽  
Vol 97 (9) ◽  
pp. 1251-1251 ◽  
Author(s):  
T. B. Adhikari ◽  
C. S. Hodges ◽  
F. J. Louws
Keyword(s):  
North Carolina ◽  
Root Rot ◽  
Management Strategies ◽  
Morphological Characteristics ◽  
Internal Transcribed Spacers ◽  
Universal Primers ◽  
Sodium Hypochlorite Solution ◽  
Tissue Samples ◽  
First Report ◽  
Root Necrosis

Strawberry (Fragaria × ananassa Duchesne) is an economically important fruit crop in North Carolina for domestic consumption and export. In April 2012, outbreaks of a destructive root disease were observed in strawberry cv. Chandler in Buncombe, New Hanover, and Roman counties, North Carolina. Samples from Rowan (ID 13175) and Buncombe (ID 13193) counties submitted to the Plant Disease and Insect Clinic of the Department of Plant Pathology, North Carolina State University, exhibited yellowing and wilting of leaves and extensive root necrosis, and disease severity based on field symptoms ranged from 20 to 30%. To identify the pathogen, five small pieces of necrotic crown and root tissues were taken from each sample, surface disinfested for 1 min in a 1.5% sodium hypochlorite solution, and plated onto potato dextrose agar (PDA) with 0.5 g liter–1 of streptomycin sulfate. Colonies developing from the tissue samples were transferred to PDA. Colonies from both samples were identical, grew relatively slowly, and gradually turned yellowish to partially brownish. After about 7 days, abundant conidia were formed. These were hyaline, mostly straight with both ends rounded, predominantly three septate, and 40 to 50 × 5 to 10 μm. Based on morphological characteristics, these isolates were identified as a species of Cylindrocarpon (1) To confirm the original identification of the fungus as a species of Cylindrocarpon, genomic DNA of both isolates was extracted from mycelia using DNeasy Plant Mini Kit (Qiagen Inc., Valencia, CA) and analyzed using PCR (2). The internal transcribed spacers (ITS)1 and (ITS)2 flanking the 5.8S rRNA regions were amplified and sequenced using universal primers ITS1 (forward) and ITS4 (reverse). The sequences of the 421 bp (GenBank KC847090 and KC847091) of both isolates were identical. Furthermore, a BLASTn search of these sequences showed homology of 99% with the sequences of Cylidrocarpon species (AB369421.1, AM419069.1, AM419074.1, AY295332.1, JN031017.1, JN253505.1, and JQ886422.1), To fulfill Koch's postulates, inoculum of each isolate was prepared and adjusted to 1.5 × 107 conidia/ml using a hemacytometer. ‘Chandler’ strawberry plants were grown in 25-cm diameter plastic pots (one seedling per pot) in the greenhouse and five 6-week-old plants were injected with conidia of each isolate into the base of crown using a 5-ml syringe. The plants were covered with clear plastic for 24 h and left on the greenhouse bench with a 16-h photoperiod and 25/20°C day/night temperatures and assessed for disease development 14 days after inoculation. The inoculated plants exhibited wilting and root necrosis, consistent with the symptoms observed on strawberry plants in the field. Control plants treated with distilled water remained healthy. Isolations were made from the inoculated plants and the fungus used for inoculation was recovered from all plants. The morphology of these isolates was in agreement with published descriptions of Cylindrocarpon (1). To our knowledge, this is the first report of a Cylindrocarpon sp. causing crown and root rot on strawberry in North Carolina and effective disease management strategies need to be explored. References: (1) C. D. Booth. Mycol. Pap. (CMI) 104:1, 1996. (2) T. J. White et al. Page 315 in: PCR Protocols: A Guide to Methods and Applications. Academic Press, San Diego, CA, 1990.

scholarly journals Sensitivity of Watermelon Cultigens to Ambient Ozone in North Carolina

Plant Disease ◽  
2003 ◽  
Vol 87 (4) ◽  
pp. 428-434 ◽  
Author(s):  
Gerald J. Holmes ◽  
Jonathan R. Schultheis
Keyword(s):  
North Carolina ◽  
Fruit Size ◽  
Fruit Shape ◽  
Foliar Injury ◽  
Breeding Programs ◽  
Breeding Lines ◽  
Growing Seasons ◽  
Cultivar Selection ◽  
Severity Of Injury ◽  
Eastern North Carolina

Foliar ozone (O3) injury is common on watermelon grown in eastern North Carolina. During the 2000 and 2001 growing seasons, 93 cultivars and breeding lines (i.e., cultigens) were evaluated for foliar injury caused by ambient levels of O3. One tetraploid, 42 diploid, and 50 triploid cultigens were evaluated. Injury developed on all cultigens in both years, but severity of injury varied among cultigens and between years. Visible foliar injury (percent surface area necrotic or chlorotic) was rated 1 week after the first harvest in both years. Mean injury for all cultigens was 39% in 2000 (range = 16 to 66%) and 20% in 2001 (range = 2.5 to 60%). This corresponded to greater mean seasonal O3 levels (12-h [0900 to 2100 h EST] mean daily O3 concentration between early May and mid-June) in 2000 (58 ppb) than in 2001 (52 ppb). Triploid cultigens were less sensitive to injury than diploid cultigens. Mean injury for all triploids was 31% in 2000 and 16% in 2001, whereas injury for diploids was 47% in 2000 and 25% in 2001. Injury level was consistently negatively correlated with average number of days between transplanting and harvest. Correlations between injury level and yield, fruit size, fruit shape, and fruit sweetness were inconsistent between years and/or insignificant. O3 tolerance in watermelon cultivars should receive increased attention in watermelon breeding programs and in cultivar selection in areas of high O3 pollution.

scholarly journals Three Pythium Species Isolated From Severely Stunted Wheat During an Outbreak in North Carolina

2017 ◽  
Vol 18 (3) ◽  
pp. 169-173
Author(s):  
Emma Lookabaugh ◽  
Barbara Shew ◽  
Christina Cowger
Keyword(s):  
United States ◽  
North Carolina ◽  
Root Rot ◽  
Yield Loss ◽  
The United States ◽  
Pythium Species ◽  
Wheat Roots ◽  
Soil Waterlogging ◽  
Pythium Root Rot ◽  
Eastern North Carolina

Large portions of eastern North Carolina experienced prolonged soil waterlogging in 2016. Severely stunted wheat plants from saturated fields were examined and Pythium spp. consistently were associated with the symptoms observed. Three species of Pythium were identified among 15 isolates derived from wheat roots and crowns: P. irregulare, P. spinosum, and P. vanterpoolii. Each species was isolated from samples that came from between two and five counties. Pythium vanterpoolii and P. spinosum have not previously been reported as pathogens in wheat in the United States. All three species caused root rot when reinoculated on wheat plants. These species are not opportunistic or mainly saprophytic on other hosts; therefore, it is likely that they contributed to the extreme stunting and yield loss observed in North Carolina wheat in 2016. The 15 isolates were tested for sensitivity to mefenoxam at 100 μg/ml a.i. and none was insensitive. Prolonged hypoxia likely predisposed North Carolina wheat to unusual levels of Pythium root rot in 2016.

New Technologies to Combat Herbicide Resistance

2020 ◽  
Vol 31 (2) ◽  
pp. 90-92
Author(s):  
Rob Edwards
Keyword(s):  
Winter Wheat ◽  
Herbicide Resistance ◽  
Cover Crops ◽  
New Technologies ◽  
Green Revolution ◽  
Arable Land ◽  
Limited Range ◽  
Cultural Control ◽  
Arable Farming ◽  
The Uk

Herbicide resistance in problem weeds is now a major threat to global food production, being particularly widespread in wild grasses affecting cereal crops. In the UK, black-grass (Alopecurus myosuroides) holds the title of number one agronomic problem in winter wheat, with the loss of production associated with herbicide resistance now estimated to cost the farming sector at least £0.5 billion p.a. Black-grass presents us with many of the characteristic traits of a problem weed; being highly competitive, genetically diverse and obligately out-crossing, with a growth habit that matches winter wheat. With the UK’s limited arable crop rotations and the reliance on the repeated use of a very limited range of selective herbicides we have been continuously performing a classic Darwinian selection for resistance traits in weeds that possess great genetic diversity and plasticity in their growth habits. The result has been inevitable; the steady rise of herbicide resistance across the UK, which now affects over 2.1 million hectares of some of our best arable land. Once the resistance genie is out of the bottle, it has proven difficult to prevent its establishment and spread. With the selective herbicide option being no longer effective, the options are to revert to cultural control; changing rotations and cover crops, manual rogueing of weeds, deep ploughing and chemical mulching with total herbicides such as glyphosate. While new precision weeding technologies are being developed, their cost and scalability in arable farming remains unproven. As an agricultural scientist who has spent a working lifetime researching selective weed control, we seem to be giving up on a technology that has been a foundation stone of the green revolution. For me it begs the question, are we really unable to use modern chemical and biological technology to counter resistance? I would argue the answer to that question is most patently no; solutions are around the corner if we choose to develop them.

Effect of precursors, fertilizers and soil cultivation on the phytosanitary condition of winter wheat crops in the zone of the Left Bank Forest-Steppe

2017 ◽  
Vol 1 (92) ◽  
pp. 100-108
Author(s):  
T.S. Vinnichuk ◽  
L.M. Parminskaya ◽  
N.M. Gavrilyuk
Keyword(s):  
Powdery Mildew ◽  
Winter Wheat ◽  
Root Rot ◽  
Forest Steppe ◽  
Left Bank ◽  
Soil Cultivation ◽  
No Till ◽  
Harmful Organisms

In the article the research the results of studies of the phytosanitary state of winter wheat sowing with three soil treatments - plowing (22-24 cm), shallow (10-12 cm) and zero (no - till) with various doses of fertilizers: N56 Р16 К16 , N110-130 Р90 К110 and N145-165 Р135 К150 , without fertilizers (control) for the two predecessors - soybean and rapeseed. The influence of these methods on the development and prevalence of powdery mildew, septoriosis of leaves, root rot of winter wheat, the most common pests in the area of research - cereal flies, wheat thrips and grain sawflies. The identified measures to limit the development and spread of harmful organisms above.

Smallseed Falseflax (Camelina microcarpa) Management in Oklahoma Winter Wheat

2021 ◽  
pp. 1-14
Author(s):  
Jodie A. Crose ◽  
Misha R. Manuchehri ◽  
Todd A. Baughman
Keyword(s):  
Winter Wheat ◽  
Weed Control ◽  
Herbicide Resistance ◽  
Wheat Yield ◽  
Acetolactate Synthase ◽  
Growing Season ◽  
Time Of Application ◽  
Adequate Control ◽  
Growing Seasons

Abstract Three herbicide premixes have recently been introduced for weed control in wheat. These include: halauxifen + florasulam, thifensulfuron + fluroxypyr, and bromoxynil + bicyclopyrone. The objective of this study was to evaluate these herbicides along with older products for their control of smallseed falseflax in winter wheat in Oklahoma. Studies took place during the 2017, 2018, and 2020 winter wheat growing seasons. Weed control was visually estimated every two weeks throughout the growing season and wheat yield was collected in all three years. Smallseed falseflax size was approximately six cm in diameter at time of application in all years. Control ranged from 96 to 99% following all treatments with the exception of bicyclopyrone + bromoxynil and dicamba alone, which controlled falseflax 90%. All treatments containing an acetolactate synthase (ALS)-inhibiting herbicide achieved adequate control; therefore, resistance is not suspected in this population. Halauxifen + florasulam and thifensulfuron + fluroxypyr effectively controlled smallseed falseflax similarly to other standards recommended for broadleaf weed control in wheat in Oklahoma. Rotational use of these products allows producers flexibility in controlling smallseed falseflax and reduces the potential for development of herbicide resistance in this species.

scholarly journals Rattail fescue (Vulpia myuros) interference and seed production as affected by sowing time and crop density in winter wheat

Weed Science ◽  
2020 ◽  
pp. 1-10
Author(s):  
Muhammad Javaid Akhter ◽  
Per Kudsk ◽  
Solvejg Kopp Mathiassen ◽  
Bo Melander
Keyword(s):  
Winter Wheat ◽  
Grain Yield ◽  
Seed Production ◽  
Yield Components ◽  
Field Experiments ◽  
Growing Season ◽  
Sowing Time ◽  
Growing Seasons ◽  
Crop Density ◽  
Wide Range

Abstract Field experiments were conducted in the growing seasons of 2017 to 2018 and 2018 to 2019 to evaluate the competitive effects of rattail fescue [Vulpia myuros (L.) C.C. Gmel.] in winter wheat (Triticum aestivum L.) and to assess whether delayed crop sowing and increased crop density influence the emergence, competitiveness, and fecundity of V. myuros. Cumulative emergence showed the potential of V. myuros to emerge rapidly and under a wide range of climatic conditions with no effect of crop density and variable effects of sowing time between the two experiments. Grain yield and yield components were negatively affected by increasing V. myuros density. The relationship between grain yield and V. myuros density was not influenced by sowing time or by crop density, but crop–weed competition was strongly influenced by growing conditions. Due to very different weather conditions, grain yield reductions were lower in the growing season of 2017 to 2018 than in 2018 to 2019, with maximum grain yield losses of 22% and 50% in the two growing seasons, respectively. The yield components, number of crop ears per square meter, and 1,000-kernel weight were affected almost equally, reflecting that V. myuros’s competition with winter wheat occurred both early and late in the growing season. Seed production of V. myuros was suppressed by delaying sowing and increasing crop density. The impacts of delayed sowing and increasing crop density on seed production of V. myuros highlight the potential of these cultural weed control tactics in the long-term management programs of this species.

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