Reduced Seedling Emergence Research Articles

Establishment and summer survival of the perennial legumes, Dorycnium hirsutum and D. rectum in Mediterranean environments

The genus Dorycnium has been identified for its potential use as a forage plant for southern Australia, but little is known about factors affecting establishment and survival. This investigation examined some factors affecting the establishment of D. hirsutum and D. rectum in Mediterranean environments of south-west Western Australia. The population dynamics of D. hirsutum and D. rectum seedlings were investigated during the summer drought in 4 environments. The effect of time of sowing on establishment and survival of D. hirsutum was tested as a management option for improving establishment of these species. Poor seedling performance was observed in both Dorycnium species. Less than 20% of D. rectum plants survived the summer drought at all locations, compared with >50% for D. hirsutum seedlings. Poor seedling vigour coupled with weed competition resulted in low plant numbers at 2 sites. Compared with autumn sowings, populations of D. hirsutum sown in August and September had lower plant densities before summer due to poorer seedling emergence. Plant numbers declined during the summer in all plots, but losses were greatest in those sown in September. In both experiments, small D. hirsutum plants survived in plots where little competition was present. Improvements in seedling vigour may be possible with plant breeding but establishment methods that reduce weed competition are valuable. Spring sowing may enable effective weed control before seeding, but later sowings run the risk of reducing seedling emergence and survival.

Effects of vegetation canopy and climate on seedling establishment in Mediterranean shrubland

Abstract Question: Does the influence of plant canopy on seedling establishment interact with climate conditions, and particularly, do intensified drought conditions, enhance a positive effect of the vegetation canopy on seedlings in Mediterranean-type ecosystems. Location: Mediterranean shrubland near Barcelona, Spain at 210 m a.s.l. Methods: Over the course of four years we recorded seedling emergence and survival in open areas and below vegetation under control, drier and warmer experimental climatic conditions. Results: Seedling emergence is more sensitive to climate conditions than later stages of growth. When considering the whole set of species, the total number of established seedlings at the end of the experiment was lower in the drought and warming stands than in control ones, and vegetation canopy increased the number of these seedlings in the drought stands. Drought reduced seedling emergence but not warming, while the interaction between climate treatments and vegetation canopy was not signif...

Tillage and Poultry Litter Application Effects on Cotton Growth and Yield

Although use of no‐tillage in cotton (Gossypium hirsutum L.) production in the southeast USA has dramatically increased recently, reports of reduced seedling emergence, poor plant establishment, reduced growth, delayed maturity, and low yields still constrain adoption. The objective of this study was to evaluate the effect of tillage systems on growth and yield of cotton grown in rotation with a winter rye (Secale cereale L.) cover crop with poultry litter and ammonium nitrate fertilizer application in north Alabama. Results from 1996 to 2001 are reported in this paper. Treatment factors were three tillage systems, two cropping systems, two N sources, and four N levels. Winter rye cover cropping increased surface residue cover by up to 35, 70, and 100% in conventional tillage, mulch tillage, and no‐tillage systems, respectively. Despite initial differences in rate of seedling emergence, final seedling establishment averaged 10 seedlings m−1 in all treatments. At the rate of 100 kg N ha−1, the effect of poultry litter on cotton growth and yield parameters was generally lower or similar to that of ammonium nitrate at the rate of 100 kg N ha−1. However, at 200 kg N ha−1, poultry litter improved cotton growth and lint yield compared with ammonium nitrate at 100 kg N ha−1 or poultry litter at 100 kg N ha−1. Cotton lint yields averaged over all treatments ranged from 1128 to 1405 kg ha−1 over the study period. With adequate N fertility from poultry litter, no‐tillage and mulch‐tillage systems with winter rye cover cropping are ideal for cotton production in the southeast USA.

Field Isolates of Streptomyces Differ in Pathogenicity and Virulence on Radish.

Common scab is a significant disease of potato, and affects root and tuber crops worldwide. Streptomycetes, a diverse group of soil-inhabiting gram-positive bacteria, cause common scab. To better understand the basis for variability in disease symptoms seen in field situations, strep-tomycetes were isolated from scabby potato plants. Isolates differed in morphology and pigmentation. Isolates were evaluated for pathogenicity and virulence in radish. Scab lesions varied in appearance and severity. Disease symptoms also included plant stunting, wilting, necrosis, and death. Some pathogenic isolates were missing genes from the putative pathogenicity island (PAI); several lacked the nec1 gene, and one was missing the txtA gene encoding thaxtomin biosynthesis, the most reliable pathogenicity determinant. Studies of disease severity over 5 logs initial inoculum density showed that there is a threshold inoculum density for disease. Disease severity increased with inoculum density over three logs, then reached a maximum, which is characteristic of individual Streptomyces strains. Lesion severity was not correlated with presence of melanin, the nec1 gene, or whether an isolate reduced seedling emergence or plant survival. Differences in disease symptoms and severity combined with absence of known pathogenicity determinants (txtA) or factors (nec1) suggest that there may be pathogenicity factors in addition to thaxtomin.

Effects of water level and phosphorus enrichment on seedling emergence from marsh seed banks collected from northern Belize

The effects of water level and nutrient additions on seed germination from the seed banks of phosphorus-limited freshwater herbaceous wetlands in Northern Belize, Central America, were tested in a greenhouse study. Seed bank soil was exposed to both draw-down and flooded conditions with and without added phosphorus (P) in a replicated germination assay. The seed banks of herbaceous species, as assessed by seedling emergence, in 7 marshes of the study area ranged in size from 55 to 1556 seeds m −2 and from 4 to 15 species. The dominant species in the standing vegetation, Typha domingensis Pers., Eleocharis cellulosa Torr., and Cladium jamaicense Crantz, were almost completely absent in the seed banks. The addition of phosphorus and flooding each reduced the number of species germinating from the seed banks by 50%, although the effect of water level varied by marsh. Phosphorus had a greater effect on the total number of seedlings emerging in flooded than draw-down treatments, reducing emergence by 75 and 20%, respectively. Overall, flooding reduced seedling emergence by 50%. The emergence of Typha from the seed banks, a competitive dominant in the marshes, was not increased by the addition of P.

CRYPTIC CONSEQUENCES OF A DISPERSAL MUTUALISM: SEED BURIAL, ELAIOSOME REMOVAL, AND SEED-BANK DYNAMICS

In moving seeds from one location to another, dispersers define the ecological context that a plant will experience throughout its lifetime. Because seed deposition sites may benefit one plant life cycle stage but not others, dispersal may give rise to a conflict between a plant's dispersal needs (e.g., predator escape) and its requirements for successful establishment (e.g., suitable habitat). In this study, we assessed the effects of two com- ponents of seed dispersal by ants (seed burial depth and elaiosome removal) at several stages during the recruitment of Leucospermum truncatulum, an ant-dispersed plant from the fynbos shrublands of South Africa. A seed-predator exclusion experiment revealed that the removal of elaiosomes significantly reduced rodent predation on seeds buried 1 cm deep and increased the viability of seeds that were not consumed. In contrast, we found that elaiosomes had no effect on the probability of a living seed emerging as a seedling. In a seed burial depth experiment in which predators were not excluded, deeper burial significantly enhanced seed survival, but this benefit came at the expense of reduced seedling emergence, delayed emergence, and smaller cotyledon size. Despite the potential importance of these seedling characteristics, elaiosomes and burial depth had no significant effect on seedling survival through the first year of this study. In contrast, burial depth had strong positive effects on the fraction of seeds that persisted in the seed bank. Although dormant individuals may die before germinating and reproducing, those that persist at greater soil depths can play a crucial role in rescuing populations from local extinction in unpredictable environments. Given the extreme variability in fire frequency in fynbos, the net effect of seed dispersal by ants on plant populations will depend on how temporal fluctuations in fire regimes influence cost-benefit thresholds related to seed dormancy and seed mortality.

STAND ESTABLISHMENT TECHNOLOGIES FOR PROCESSING CARROTS

STAND ESTABLISHMENT TECHNOLOGIES FOR PROCESSING CARROTS

INCIDÊNCIA DE BIPOLARIS SOROKINIANA NAS SEMENTES E A TRANSMISSÃO PARA PLANTAS DE CEVADA

O potencial de rendimento do cultivo de cevada é diminuído principalmente pela ocorrência de doenças como helmintosporiose ou mancha marrom (Bipolaris sorokiniana Sacc. in Soroc) transmitida pelas sementes. A hipótese desse trabalho é de que se a semente de cevada é o principal agente de disseminação de Bipolaris sorokiniana, então diferentes níveis de incidência do fungo em sementes podem se correlacionar com a incidência do fungo nas plantas oriundas dessas sementes. O objetivo desse trabalho foi verificar a correlação entre diferentes níveis de incidência do fungo em sementes e sua transmissão para plantas de cevada em campo e casa-de-vegetação e determinar a capacidade de transmissão do fungo pela semente. Sementes de vários lotes da cultivar BR2 com níveis de incidência de 2,7; 7,5; 12,5; 16,5; 31,0 e 55,5% foram semeadas em campo com 4 repetições. As avaliações foram realizadas aos 7 dias após a emergência, nas 4 fileiras centrais de cada parcela, contando-se o número de plantas com sintomas de helmintosporiose e determinando-se a porcentagem em relação à emergência. Em casa-de-vegetação as sementes foram semeadas em caixas plásticas com aproximadamente 13 kg de solo esterilizado com dazomet. Foram utilizadas 400 sementes a profundidade de 3 cm. Demonstrouse a importância da semente infectada como fonte de inóculo primário. Observou-se que a transmissão do patógeno no campo foi mais eficiente quando o nível foi de 55,5%. Em casa-de-vegetação, houve correlação apenas entre a incidência nas sementes e nas raízes. Conclui-se que não há correlação entre diferentes níveis B. sorokiniana nas sementes e a sua incidência em campo e que níveis de 55,5% diminuem a emergência das plantas no campo e em casa-de-vegetação.

Preharvest Applications of Glyphosate Affect Emergence and Seedling Growth of Field Pea (Pisum sativum)1

Field experiments were conducted in 1994 and 1995 at Vegreville, Legal, and Lacombe, AB, to determine the effects of a preharvest application of glyphosate on seedling emergence and growth of field pea. Glyphosate was applied at 0.9 kg ai/ha at each of the three crop development stages, as determined by seed moisture content (SMC), to determinate (‘Ascona’ and ‘Radley’) and indeterminate (‘Miko’ and ‘Trapper’) cultivars. Applying glyphosate when the SMC was less than 30% had little to no effect on seedling emergence but reduced seedling shoot fresh weight in two of six experiments. Applying glyphosate at SMC above 40% reduced seedling emergence and shoot fresh weight in two and three of the six experiments, respectively. Reductions in seedling emergence and shoot fresh weight were greater from seeds collected from the top than from seeds collected from the bottom one-third of sprayed plants. Differences in response between determinate and indeterminate cultivars occurred, but there was no consistent trend. Given the variable maturity in most fields and on individual pea plants, applications of preharvest glyphosate to peas destined for seed production may decrease seed germination and biomass accumulation.Nomenclature: Glyphosate; field pea, Pisum sativum L. ‘Ascona’, ‘Miko’, ‘Radley’, ‘Trapper’.Additional index words: Crop desiccation, determinate and indeterminate pea cultivars, harvest aid.Abbreviations: SMC, seed moisture content.

Seedborne fungal pathogens of jacaranda (Dalbergia nigra) tree

Seedborne fungal pathogens reduced seedling emergence and the quality of Dalbergia nigra seedlings in Brazil. Cladosporium cladosporioides, Colletotrichum crassipes, Fusarium semitectum, Phomopsis dalbergiae and Pestalotiopsis sp. were the only fungi consistently isolated from seed samples obtained from a number of trees. Colonisation of both, pericarp and seed by these fungi starts soon after pod formation and continues to increase to pod maturity. Except for C. cladosporioides, all the other fungi were highly pathogenic to seeds and to seedlings, causing seed rot, root rot and reduced seedling height and survival. The leaf spots of P. dalbergiae extended to the hypocotyl causing dieback, whereas those caused by C. crassipes remained restricted to leaves. Both the seedborne fungi also latently colonised the hypocotyl. Foliar inoculation of seedlings with Pestalotiopsis sp. induced severe chlorosis and defoliation. The findings of this study explain the heavy losses suffered by nurserymen due to low quality seedlings. This is the first report on economic loss due to these fungi on this host.

PHOSPHORUS PLACEMENT ON ACID ARENOSOLS OF THE WEST AFRICAN SAHEL

Phosphorus (P) deficiency is a major constraint to pearl millet (Pennisetum glaucum L.) growth on acid sandy soils of the West African Sahel. To develop cost-effective fertilization strategies for cash poor farmers, experiments with pearl millet were conducted in southwestern Niger. Treatments comprised single superphosphate hill-placed at rates of 1, 3, 5 or 7 kg P ha−1 factorially combined with broadcast P at a rate of 13 kg ha−1. Nitrogen was applied as calcium ammonium nitrate at rates of 30 and 45 kg ha−1. At low soil moisture, placement of single superphosphate in immediate proximity to the seed reduced seedling emergence. Despite these negative effects on germination, P placement resulted in much faster growth of millet seedlings than did broadcast P. With P application, potassium nutrition of millet was improved and seedling nitrogen uptake increased two- to three-fold, indicating that nitrogen was not limiting early millet growth. Averaged over the 1995 and 1996 cropping seasons, placed applications of 3, 5 and 7 kg P ha−1 led to 72%, 81% and 88% respectively, of the grain yield produced by broadcasting 13 kg P ha−1. Nitrogen application did not show major effects on grain yield unless P requirements were met. A simple economic analysis revealed that the profitability of P application, defined as additional income per unit of fertilizer, was highest for P placement at 3 and 5 kg ha−1.

Seedling establishment in an Australian tropical savanna: effects of seed supply, soil disturbance and fire

Summary Australia's savannas typically are burnt every 1–3 years. Although there are concerns about the effect of frequent fire on recruitment of Australian savanna species, there is a lack of information. This research aimed to determine whether seed or microsite availability limits seedling recruitment of the overstorey tree Eucalyptus miniata and the midstorey shrub Acacia oncinocarpa, whether seed or microsite availability is affected by frequent fire, and the consequent effect on seedling recruitment. Quadrats were established in unburnt areas. Experimental manipulations were addition of seed and/or disturbance of the soil surface to increase the number of microsites suitable for germination. In a second experiment, seed was added to quadrats established in three fire regimes after the annual burning event (unburnt, burnt early in the dry season, burnt late in the dry season). In unburnt areas, seedling regeneration was limited by both seed supply and microsite availability. Both burning regimes reduced seedling emergence, possibly because the reduced canopy cover caused unfavourable microclimate, the increased grass and forb ground cover increased competition for resources, and there was increased loss of seed to seed harvesters. The results indicate that sexual regeneration of these common species is disadvantaged by current burning practices because both seed supply and the number of microsites are reduced. Thus, long‐term changes in savanna floristic structure seem likely unless fire managers aim to increase the fire‐free intervals. The relative abundance of species able to reproduce vegetatively may increase under frequent fire regimes. Such a change may take a long time to detect given the fire‐resistant and long‐lived nature of overstorey species, and the capacity for vegetative regeneration in many savanna species. The impacts of fire on limiting seedling regeneration will require savanna managers to consider fire‐free intervals of several years for effective recruitment of dominant woody species.

Seedborne Pathogenic Fungi that Affect Seedling Quality of Red Angico (Anadenanthera macrocarpa) Trees in Brazil

AbstractInternal and external seedborne fungal pathogens of Anadenanthera macrocarpa reduced seedling emergence and the quality of seedlings grown from contaminated seeds. Colletotrichum gloeosporioides, Fusarium lateritium, F. semitectum, Pestalotiopsis sp. and Phomopsis dalbergiae were the only fungi consistently isolated from seed samples collected from afforestation companies, university forestry departments and a Forest Reserve Park. Their frequency was much lower in surface disinfested than in untreated seeds. The temporal dynamics of the pericarp and seed infection on trees used for seed harvest in the Forest Reserve Park showed that colonization by these fungi starts soon after pod and seed formation, and continues to increase to pod maturity. Although the maximum proportion of infected seeds occurred at full maturity, their proportion was also high at physiological maturity. The high external seed infestation appears to occur during on‐floor sun drying of the pods and separation of pericarps from seeds by broom sweeping. All five fungi were highly pathogenic to seeds and seedlings, causing seed rot, root rot and reduced height and thriftiness of surviving seedlings. Our results explain the heavy losses suffered by nurserymen due to low quality seedlings. This is the first report of the occurrence of these fungi on this host causing economical losses.

Phytotoxicity in pearl millet varies among in-furrow insecticides

Chinch bug [ Blissus leucopterus leucopterus (Say.)] is the insect most likely to cause economic damage to pearl millet [ Pennisetum glaucum (L.) R. Br.], a promising alternative feedgrain crop for the Southeast and Mid-South regions of the United States. In-furrow application of insecticide offers early season protection against chinch bug but may be phytotoxic. The insecticides that control early season infestations in other crops were evaluated for phytotoxic effects on pearl millet emergence and seedling growth under greenhouse conditions. Phorate caused the most phytotoxicity, reducing seedling emergence to less than 7% and shoot weight to 12 mg per seedling (17% of the non-treated control) at dose rates of 50.4 and 67.2 mg a.i. pot −1. Aldicarb, chlorpyrifos, and terbufos all caused some phytoxicity expressed by reduced seedling emergence. No phytotoxicity was observed with tefluthrin and tebupirimphos+cyfluthrin, either of which could be recommended for in-furrow application if effective against chinch bug on pearl millet.

Rodent‐limited establishment of bush lupine: field experiments on the cumulative effect of granivory

Summary Plants often suffer substantial loss of seeds to consumers. However, because the seed‐to‐seedling transition is frequently ignored, quantitative estimates of the effects of seed consumers on plant population dynamics are rare. We examined how post‐dispersal seed predation by rodents affected seedling emergence and subsequent adult plant abundance of bush lupine (Lupinus arboreus), a large N‐fixing shrub common to coastal dunes in California. We monitored patterns of seedling emergence and survival over 3 years for seeds sown into exclosed and control plots. We sowed additional cohorts of seeds in the second and third years and compared interannual variation in emergence patterns. Rodent exclusion substantially reduced seedling emergence, with an average of 109 seedlings emerging over 3 years from 476 seeds sown in rodent exclusion plots vs. 26 from control plots. The intensity of granivory, however, varied between years, with rodent exclusion increasing emergence from seeds sown in year one, but not in year two. Winter seedling mortality, due to cutworm herbivory, was similarly high in rodent‐free and control plots, and its net impact was to reduce the difference in seedling abundance. Thus, by mid‐summer in each of the three years, there were only marginally more seedlings in rodent‐excluded vs. control plots. The cumulative effect of protecting seeds, was, however, large. After 3 years, an average of four adult lupines were established in rodent‐free plots, whereas only 0.5 were found in control plots and lupine biomass was more than 5‐fold higher in exclusion plots. Taken together, the results indicate that rodents play a critical role by limiting the abundance and biomass of a large N‐fixing shrub in dunes.

Crop responses to applied soil compaction and to compaction repair treatments

Crop responses to annual compaction treatments (applied to whole plots) and management treatments to ameliorate compacted soil were determined in a field experiment on a Vertisol. Initially, all treatments except a control were compacted with a 10 Mg axle load on wet soil (26% gravimetric water content compared with a plastic limit of 22%). Annually applied axle loads of 10 and 6 Mg on wet soil (25–32% soil water) tended to reduce seedling emergence, grain yield (wheat, sorghum and maize), soil water storage and crop water use efficiency (WUE). Annual applications of an axle load of 6 Mg on dry soil (<22% soil water) had little effect on crop performance. Mean reductions in the yield of five crops (three wheat, one sorghum and one maize) in comparison with the uncompacted control were 23% or 0.79 Mg ha −1 (10 Mg on wet soil), 13% or 0.44 Mg ha −1 (6 Mg on wet soil) and 1% or 0.03 Mg ha −1 (6 Mg on dry soil). Maize grown in the fifth year of treatment application was most affected by compaction of wet soil, its WUE being reduced from 14.3 to 9.7 kg ha −1 mm −1 in response to an axle load of 10 Mg. Reduced WUE was associated with delayed soil water extraction at depth. A 3-year pasture ley was the most successful amelioration treatment. A wheat and a maize crop grown after the ley outyielded the control by 0.33 and 0.90 Mg ha −1, respectively. So the pasture not only ameliorated the initial compaction damage, with respect to crop performance, but resulted in improvements in two subsequent crops.

Field pea response to seeding depth and P fertilization

A study was conducted at Melfort, SK, in 1998 and 1999 to determine whether seeding depth and P fertilization affect field pea (Pisum sativum L.) seedling emergence and grain yield. Treatments included a factorial combination of three seeding depths (38 mm, 76 mm, and 114 mm) with and without 25 kg P2O5 ha–1 as monoammonium phosphate. While seedling density was not affected by seeding depth at 3 wk after planting, the deepest seeding depth produced significantly fewer seedlings than the two shallower depths at 5 wk post-seeding. A year-by-seeding-depth interaction was recorded for grain yield, with deep seeding (114 mm) reducing yield by 8.5% in 1998, while no significant differences were recorded due to depth in 1999. Side-banded phosphorus fertilizer applications reduced seedling emergence at 3 wk; however, no difference was recorded by 5 wk after seeding. At harvest, addition of P fertilizer significantly increased grain yields on this high P testing soil; however, this response was small, averaging 138 kg ha–1. Results of this trial indicate that while field peas can tolerate deep seeding there appears to be little benefit from seeding deeper than 76 mm. Key words: Field pea, seeding depth, P fertilizer

Effect of feeding by the western conifer seed bug, Leptoglossus occidentalis, on the major storage reserves of developing seeds and on seedling vigor of Douglas-fir.

The impact of feeding by the western conifer seed bug (Leptoglossus occidentalis Heidemann) on storage reserves of developing seeds of Douglas-fir (Pseudostuga menziesii (Mirb.) Franco) was studied by caging nymphal and adult seed bugs on cones during late-season development, and nymphs on cones during early, mid- and late-season development. Analysis of the major storage reserves of partially damaged seeds revealed that late-season feeding by each life stage and feeding by nymphs at all three stages of cone development significantly reduced the amounts of lipid and buffer-insoluble (crystalloid) protein in seeds at harvest by up to 78 and 97%, respectively. Seeds showing light to moderate damage on radiographs did not exhibit a reduction in the amount of buffer-soluble (matrix) protein. Seeds damaged by feeding during early development compensated in part by continuing to synthesize lipid and crystalloid protein. Light or moderate damage to mature Douglas-fir seeds exposed to L. occidentalis in the laboratory reduced seedling emergence by > 80%, but the seedlings that emerged successfully appeared to suffer no adverse effects when grown under standard nursery conditions.

Chicory and English Plantain Seedling Emergence at Different Planting Depths

Chicory (Cichorium intybus L.) and English plantain (Plantago lanceolata L.) have been introduced in the USA as perennial herbs for pastures. A knowledge of seedling emergence and the structure of these species under different planting conditions is necessary for developing planting recommendations. We conducted controlled environment and field studies to compare the emergence and morphology of chicory and plantain seedlings from three planting depths. ‘Grasslands Puna’, ‘La Certa’, and ‘Forage Feast’ chicory, and ‘Ceres Tonic’ and ‘Grasslands Lancelot’ plantain were sown at 1, 3, and 6 cm depths in the growth chamber and greenhouse. The seedlings were destructively sampled 14 d after emergence, and the number and mass of leaves and roots (primary, lateral, basal, and adventitious) were recorded. The same cultivars were sown in field plots in July and September 1998 to determine seedling size and emergence from 1‐, 3‐, or 6‐cm planting depths. Controlled environment studies showed that deeper planting reduced the root weight, length, and number more in chicory than in plantain. Planting at 3 and 6 cm in the field reduced seedling emergence by 34 and 60% (avg. of cultivars), respectively, compared with the 1‐cm planting depth. Differences in seedling size among cultivars within species were mainly related to differences in seed mass. Plantain had better seedling emergence in the field than chicory (54 vs. 27% in July and 60 vs. 17% in Sept.), and these differences were not related to differences in seed mass. Both chicory and plantain should be planted no deeper than 1 cm for rapid establishment.

Identity and Pathogenicity of Fungi Associated with Root and Crown Rot of Soft Red Winter Wheat Grown on the Upper Coastal Plain Land Resource Area of Mississippi

Seedling stand, disease severity and fungal incidence were determined from untreated ‘Wakefield’ soft red winter wheat planted on a Leeper silty clay loam in field tests conducted at the Mississippi Agricultural and Forestry Experiment Station, Plant Science Research Center, Mississippi State University, Starkville, Mississippi during the 1996–97 and 1997–98 growing seasons. Seedling stand was reduced by 40% each year in plots established with untreated seed. Cochliobolus sativus was the most frequently isolated fungus. Fusarium acuminatum, Fusarium equiseti and Fusarium solani were the most prevalent Fusarium spp. Seven other Fusarium spp. and 23 species of other fungal genera were isolated. Pathogenicity tests with three isolates each of C. sativus, Cochliobolus spicifer, F. acuminatum, F. solani, F. equiseti, Fusarium compactum, Embellisia chlamydospora and Microdochium bolleyi were performed in test tube culture and two isolates each of C. sativus, C. spicifer, F. acuminatum, E. chlamydospora and M. bolleyi under greenhouse conditions. In test tubes and in the greenhouse, seedlings infected with isolates of C. sativus developed seedling blight, discoloration and necrosis, primarily in seminal roots and crowns. In the greenhouse, C. sativus induced lesions on the lower leaf sheath and reduced seedling height, seedling emergence, dry and fresh weight of roots and shoots. Isolates of F. acuminatum, F. solani, F. equiseti, F. compactum, E. chlamydospora and M. bolleyi induced slight to moderate orange to light‐brown discoloration of crown and seminal roots in test tubes. Cochliobolus spicifer isolates had the most pre‐emergence activity, inducing black root discoloration and root pruning of wheat seedlings and reducing seedling emergence, root fresh weight and shoot dry weight. In the greenhouse, F. acuminatum reduced seedling height, seedling emergence and root and shoot dry weights. Microdochium bolleyi and E. chlamydospora reduced fresh and dry weight of roots, plant emergence and shoot dry weight. Fusarium acuminatum and C. spicifer reduced the growth rate of wheat seedlings. All fungi evaluated showed increased disease severity compared to the untreated control. The high frequency of isolation of C. sativus from crown and root tissues can be partially explained by the dry, warm conditions during the early stages of wheat seedling development in the Upper Coastal Plain Land Resource Area of Mississippi.