Seed Treatment Fungicides Research Articles

Impact of seed potatoes infected withPhytophthora infestans (US-1 or US-8 genotypes) on crop growth and disease risk

As the surface area with late blight symptoms of seed tubers increased, the incidence of plant emergence decreased. This relationship was more dramatic with the US-8 genotype than the US-1 genotype ofhytophthora infestans, causal agent of late blight. However, when seed tubers were inoculated with both US-1 and US-8 isolates, the plant growth responses were generally intermediate to those obtained with the two genotypes alone. More resistant cultivars (eg. Dorita, Island Sunshine, and Sebago) had greater plant emergence and less seed rot than more susceptible cultivars (eg. Green Mountain and Shepody) but the response differences between resistant and susceptible cultivars was less clear with US-8 as most cultivars had 100% seed rot. Seed handling treatments affected crop growth and disease risk; as the inoculum levels and in some cases, the pre-planting storage period increased, plant emergence decreased generally due to greater seed rot incidences. Of the one registered seed treatment fungicide and several non-registered and/or experimental fungicides tested, only two significantly improved plant emergence.

Influence of Tillage, Seed Quality, and Fungicide Seed Treatments on Cotton Emergence and Yield

Seedling diseases of cotton (Gossypium hirsutum L.) limit production in the High Plains of Texas. Field studies were conducted from 1992 through 1995 to determine the influence of tillage (conventional or terminated wheat [Triticum aestivum L.] conservation tillage system), seed quality, and fungicide seed treatments (specific for Rhizoctonia solani, Pythium spp., and Thielaviopsis basicola) on cotton emergence and lint yield. Seed quality positively affected plant emergence and yield in all years. Increases in plant emergence and yield were generally found with conventional rather than conservation tillage. Emergence 21 d or later was generally lower for untreated seed or Captan (C) (N-trichloromethylthio-4-cyclohexene-1,2-dicarboximide) treated seed than seed treatments that included triadimenol (Baytan 30 [B]) (Beta-(4-Chlorophenoxy)-alpha-(1,1-dimethylethyl)-1H-1,2,4-triazole-1-ethanol) in 3 of 4 yr; carboxin-PCNB (Vitavax-PCNB [V]) (5,6-dihydro-2-methyl-N-phenyl-1,4-oxathiin-3-carboxamide-Pentachloronitrobenzene) in 2 of 3 yr and metalaxyl (Apron 2.66F [A]) (N-(2,6-dimethyl-phenyl)-N-(methoxyacetyl)alanine methyl ester) + C in one year. Yields were affected by seed treatments in 3 yr, with B being associated with higher yields every year, and lower yields associated with chloroneb (Nuflow ND [N]) (1,4-dichloro-2,5-dimethoxybenzene) + TCMTB (2-(thiocyanomethylthio) benzothizaole (1992), untreated seed (1994) and C (1995). Plants were infected most frequently with R. solani and T. basicola. The most consistent factor affecting seedling disease was seed quality. Conventional tillage and seed treatments specific for Rhizoctonia and Thielaviopsis improved seedling emergence and yield most years. Interactions between chemical seed treatments, seed quality, and tillage systems were inconsistent between years and even among different evaluation times in the same year.

Synthesis of Stereoisomers of Ipconazole and Their Fungicidal and Plant Growth Inhibitory Activities

Two racemic diastereomers 5a and 5b, both of which are active ingredient of a seed treatment fungicide on rice, ipconazole, (1RS,2SR,5RS;1RS,2SR,5SR)-2-(4-chlorobenzyl)-5-isopropyl-1-(1H-1,2,4-triazol-1-ylmethyl)cyclopentanol, and two other racemic diastereomers (1RS,2RS,5RS)-5c and (1RS,2RS,5SR)-5d were synthesized, and fungicidal activity and plant growth inhibitory activity were examined. Enantiomers of 5a and 5b were prepared, and their fungicidal activities were also examined. Racemic diastereomers 5a, 5b and 5d were more active than 5c in fungicidal activity (EC 50 value) in vitro on Gibberella fujikuroi, Cochliobolus miyabeanus and Pyricularia oryzae. In plant growth inhibitory activity test for seed treatment on rice, only 5d was slightly active in the first sheath growth inhibition. The comparative test of enantiomers in vitro revealed that the fungicidal activities of (−)-5a and (−)-5b were higher than those of corresponding (+)-5a and (+)-5b, respectively.

Fungicide Seed Treatment Effects on Emergence of Deeply Planted Winter Wheat

Winter wheat (Triticum aestivum L.) seed is often planted deeply (>3 in.) into stubble-mulch fallow in the semi-arid Pacific Northwest (PNW). Stand establishment is affected by factors that influence the rate of seed germination and coleoptile growth. Systemically translocated triazole and imidazole fungicide seed treatments were compared for effects on seedling emergence under conditions of deep seed placement and variable seed-zone moisture in stubble-mulch fallow systems. Fungicides included RTU Vitavax Thiram (carboxin [2,3-dihydro-5-carboxanilido-6-methyl-1,4-oxathiin] + thiram [tetramethylthiuram disulfide]), Dividend (difenoconazole [1-(2-[4-(4-chlorophenoxy)-2-chlorophenyl]-4-methyl-1,3-dioxolan-2-yl-methyl)-1H-1,2,4-triazole]), Raxil Thiram (tebuconazole [α[2-(4-chlorophenyl)ethyl]-α-(1,1-dimethylethyl)-1H1,2,4-triazole-1-ethanol] + thiram), NuZone and Flo-Pro IMZ (imazalil [1-(2-(2,4-dichlorophenyl)-2-(2-propenyloxy)ethyl)-lH-imidazole]), and Apron (metalaxyl [N-(2,6-dimethylphenyl)-N-(methoxyacetyl)-alanine methyl ester)]). Gaucho (imidacloprid [1 [(6-chloro-3-pyridinyl)methyl]-N-nitro-2-imidazoli-diniminel), a seed-treatment insecticide, was applied in some experiments. Seven field and three greenhouse experiments were performed from 1993 to 1995. Emergence in the field tended to be superior for seed treated with Dividend, alone or mixed with Apron, in plantings made from 1- to 5-in. deep into soil with 5 to 17% seed-zone water content and at 71 to 80°F. RTU Vitavax Thiram had variable effects on seedling emergence. NuZone and Raxil Thiram, alone or mixed with Gaucho, generally delayed emergence when treated seed was planted at depths more than 2 in. In the greenhouse, treated seed was planted at 1-in. depth into moist (7, 10 or 15% w/w), warm (75°F) silt loam overlain by 4-in. of dry silt loam, simulating a planting at 5-in. depth into stubble-mulch fallow during September. Emergence of Dividend-treated seed at each soil moisture content was usually more rapid than for other treatments, including seed planted without fungicide treatment. This research demonstrated that emergence of winter wheat planted deeply into stubble-mulch fallow is often improved when seed is treated with Dividend compared with RTU Vitavax Thiram and, among the systemically translocated triazole fungicides, Dividend is a better choice than Raxil when planting depths exceed 2 in.

Fungicide Seed Treatments Influence Emergence of Winter Wheat in Cold Soil

Winter wheat (Triticum aestivum L.) in the Pacific Northwest (PNW) is typically planted when soils are warm (75°F) to cool (50°F). Drought during 1994 delayed planting in some fields until soils were cold (35-45°F). Emergence in cold, wet soil was slow and often incomplete and, in some circumstances, appeared to differ for seed treated with different fungicides. Experiments were performed in the field and greenhouse to provide improved treatment guidelines for winter wheat planted into cold soil. Emphasis was on the fungicides Vitavax (carboxin [2,3-dihydro-5-carboxanilido-6-methyl-1,4-oxathiin]), Dividend 3FS (difenoconazole [1-(2-[4-(4-chlorophenoxy)-2-chlorophenyl]-4-methyl-1,3-dioxolan-2-yl-methyl)-1H-1,2,4-triazole]), Thiram (tetramethylthiuram disulfide) and Apron (metalaxyl [N-(2,6-dimethylphenyl)-N-(methoxyacetyl)-alanine methyl ester]). Emergence of winter wheat from cold (38°F) soil was more complete when seed was treated with mixtures of Dividend + Apron, Dividend + Thiram, or RTU Vitavax Thiram than with Dividend alone or untreated. Differences in emergence were caused by Pythium root rot. Treatments including Thiram, Apron, or another fungicide toxic to Pythium species are recommended for winter wheat seed planted after about 15 October in the PNW.

Effects of Irrigation, Planting Depth, and Fungicide Seed Treatment on Sugarbeet Stand Establishment

Effects of irrigation, planting depth, and fungicide seed treatment on seedling disease and stand quality in sugarbeet were evaluated in two field experiments arranged as three-factor randomized complete block designs. Stand establishment was improved greatly by planting into moisture compared to a post-plant irrigation, shallow compared to deep planting depth, and a fungicide seed treatment. Soil population densities of Pythium spp. (primarily P. ultimum) were high in both trials. A fungicide seed treatment with metalaxyl and thiram combined with shallow planting (2 cm) and pre- plant furrow irrigation was optimal for rapid and uniform seed germination and stand establishment.

Development of Formulations ofPseudomonas fluorescensfor Control of Chickpea Wilt

Pseudomonas fluorescens strains were obtained from the rhizosphere of different crops and strains that showed inhibitory action against the chickpea (Cicer arietinum) wilt pathogen Fusarium oxysporum f. sp. ciceris were selected for further studies. The efficacy of various carriers in sustaining the population of these strains in storage was assessed. In talc-based and peat-based formulations the bacteria survived even up to 240 days of storage although the population declined from 30 days. When chickpea seeds were treated with talc-based formulations, P. fluorescens survived on the seeds for at least 180 days. When the treated seeds were sown in soil, the antagonist moved to the rhizosphere and survived well in it. Biopriming of seeds increased rhizosphere population. Seed treatment with the antagonist formulation effectively controlled chickpea wilt disease in the two field trials and increased the yield. When seed treatment was followed by root zone application the efficacy of P. fluorescens formulations increased. Pseudomonas fluorescens did not inhibit the beneficial N-fixing bacteria Rhizobium and Azospirillum in vitro and seed treatment fungicides (thiram and carbendazim) were not inhibitory to P. fluorescens in vitro.

Effects of Irrigation, Planting Depth, and Fungicide Seed Treatment on Sugarbeet Stand Establishment

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Metabolism of Ipconazole, a New Triazole Fungicide for Seed Treatment, in Rice Plants

種子消毒後のイネ幼苗および登熟期の穀粒部におけるイプコナゾール ((1RS,2SR,5RS;1RS,2SR,5SR)-2-(4-chlorobenzyl)-5-isopropyl-1-(1H-1,2,4-triazol-1-ylmethyl)cyclopentanol) の代謝について検討した. トリアゾール環を標識した [T-14C]-イプコナゾール, およびベンジルメチレン位を標識した [B-14C]-イプコナゾールをイネ種子あるいは水耕液に処理し, 温室内で栽培した. 種子処理において播種22日後では, 添加したイプコナゾールの40～41%の放射能が土壌から, また, 27%が種子および根部から回収された. イプコナゾールの地上部への移行性は乏しく, 茎葉部から検出されたのは添加量の0.36～0.42%にすぎなかった. 種子あるいは水耕液処理後のイネ幼苗中の代謝物は, 主としてイソプロピル基 (メチル, メチン) およびベンジルメチレン部位の酸化物であった. また, 水溶性画分には, 微量ながら抱合体が含まれることが示唆された. さらに種子処理したイネを収穫期まで栽培し, 穀粒中の放射性代謝物を分析したところ, 玄米中に検出された量は微量であったが, [T-14C]-イプコナゾール処理では2.5μgeq./kg, また, [B-14C]-イプコナゾール処理した場合には0.2μgeq./kgと14C標識部位により差が認められた. [T-14C]-イプコナゾール処理では玄米中の放射能のほとんどは, 植物体の抽出残さと水溶性画分に認められ, 親化合物あるいは幼苗中に検出された代謝物は検出されなかった.

Effects of Seed Factors on Spermosphere and Rhizosphere Colonization of Cotton byBacillus subtilisGB03

Cotton seed factors, including seed-surface pH, cultivar, and presence of a seed-treatment fungicide, were investigated for their effect on spermosphere and rhizosphere colonization by the commercial biological control agent Bacillus subtilis strain GB03 (GB03). Commercial (nonneutralized) cotton seed is traditionally acid-delinted and in these studies was found to have surface pH values ranging from 1.90 to 3.50. Following seed treatment with GB03, spermosphere populations of GB03 were up to 5-10-fold lower on nonneutralized (commercial acid-delinted) cotton seed than on neutralized seed grown in sterile sand or in field soil, respectively; however, rhizosphere populations of GB03 on 2-wk-old cotton root systems did not differ significantly [...]

Evaluation of seed-treatment fungicides for control of take-all in soft white spring wheat

The control of take-all in soft white spring wheat, cv. Fielder, by seed treatments with benomyl and triadimenol was tested in four trials over three years in the field. Benomyl provided erratic control of the disease at rates of 1.0 and 2.0g a.i. kg-1 seed in 1987 and 1988 but was effective at these rates and at 3.0g a.i. kg-1 seed in 1989. Benomyl significantly increased yields by 18% at 2.0g a.i. kg-1 seed in 1987 and by 15% and 28% at 3.0 g a.i. kg-1 in 1989. Triadimenol at a rate of 0.3g a.i. kg-1 seed reduced disease severity and increased yield, by 24% and 29%, respectively, in 1989 only. None of the fungicide treatments produced yields at the levels found in noninoculated checks.

Impact of Fungicide Seed Treatments on Rhizoctonia Root Rot, Take-all, Eyespot, and Growth of Winter Wheat

Fungicides were examined for in vitro activity against Rhizoctonia solani AG-8 and R. oryzae and for capacity to suppress the incidence and severity of Rhizoctonia root rot of winter wheat in eastern Oregon. Thirteen seed treatments were evaluated at three sites during 1986-87 and five were evaluated at two sites during 1987-88. A factorial experiment with variables of seed treatment and tillage intensity (conventional plowing vs. no tillage) was also performed at two sites. All seed treatments in the seven experiments were ineffective or unreliable for controlling Rhizoctonia root rot (...)

The Incidence and Survival of Sclerotinia Minor in Peanut Seed

Abstract The incidence of Sclerotinia minor was assessed in seed of two peanut (Arachis hypogaea L.) varieties (VA 81B and Florigiant) harvested from two fields in Virginia exhibiting disease symptoms typical of Sclerotinia blight. The incidence of S. minor in peanut seed with pink, light brown and dark brown testae riding a 6.4 × 25.4 mm screen averaged 1.5, 3.9 and 6.0%, respectively, from both fields. Similar trends were evident with colonization of seed by other fungi. The incidence of S. minor from pieces of testa removed from seed from both fields averaged 3.4% and 2.6%, respectively. However, the incidence of S. minor from seed cotyledons with testae removed was extremely low (<0.1%). Sclerotia of S. minor were not observed on, in or under the testa of seed or between the cotyledons of seed in prepared seed lots (lots containing only seed with pink and light brown testae). BOTEC, a seed treatment fungicide applied at recommended rate (2.5 g/kg), reduced the incidence of S. minor in peanut seed from 4.5% to 0.1%. Similar decreases were noted in other seedbome fungi commonly associated with peanut seed.

Potato growth and tuber production as affected by inoculation of cut and whole seed withRhizoctonia solani (AG 3) and the use of seed treatment fungicides

A potato seed tuber inoculation technique forRhizoctonia solant resulted in consistent field study results and demonstrated a reduction of about 15% in early plant vigor ratings 30 days after planting. Plant stands were generally unaffected by the introduced pathogen presence around the potato seed. After 45–60 days’ growth, inoculated seed had significant increases in the number of weak plants compared to the uninoculated seed. The impact ofR. solani on daughter tuber production included significant total yield losses in two of three years and seed inoculation increased the severity of black scurf on daughter tubers with significant differences occurring two of four years. Use of whole seed resulted in similar early plant vigor losses as was found for cut seed but inoculated, whole seed treatments had fewer weak plants and less yield loss than inoculated, cut seed treatments. Pre-planting seed treatment fungicide applications resulted in a few significant differences in plant growth and yield depending on the fungicide used. Black scurf incidences on daughter tubers were generally reduced but significant differences were more frequent for whole than cut seed treatments. However, none of the commercially available seed treatment fungicides provided consistent disease control. Aspects of disease incidence, development and control for potato production conditions in the northeastern region are also discussed.

Effect of environment on efficacy of seed-treatment fungicides for control of common bunt in spring and winter wheat

The effectiveness of protectant and systemic seed-treatment fungicides for control of common bunt caused by Tilletia caries (DC.) Tul. and T. foetida (Wallr.) Liro. in spring and winter wheats was evaluated at different locations from 1981 to 1987. The fungicides, tested at two rates (I and II), were of three types: (1) fungicides which were effective in all years and locations at levels approaching 100%; (2) fungicides which provided uniform bunt control in all years and locations at levels less than 100%, and (3) fungicides which were sensitive to environmental conditions within years and locations. Fungicides which were effective in all years and locations at levels approaching 100% were triadimenol II, myclobutanil I and II, diniconazole I and II, and flutriafol II, on spring wheat, and etaconazole and furmecyclox in the seed-(SD), and seed- and soil- (SS) inoculation treatments, and triadimenol in the SD-inoculation treatment on winter wheat. Fungicides which provided uniform bunt control in all years and locations at levels less than 100% included flutriafol I and triadimenol I in spring wheat, applied at rates below optimal, and carboxin dust and nuarimol on winter wheat, in SS- and SD-inoculation treatments. Fungicides which were sensitive to environmental conditions within years and location included maneb, carboxin I and II on spring wheat, and carboxin solution and dust in the SD- and SS-inoculation treatments on winter wheat. Comparisons of bunt levels in fungicide treatments with those in the infested controls revealed that some fungicides did not perform consistently across years and locations. Variation in efficacy of fungicides was classified into three types: (1) random environmental variation which occurred with all fungicide treatments tested; (2) non-random environmental variation which occurred with maneb and carboxin fungicides, and (3) variation attributed to increasing bunt severity which occurred with the SS and SD carboxin fungicides used to control bunt in winter wheat. The implications of inadequate protection from currently registered seed-treatment fungicides on wheat varieties that are highly susceptible to bunt are discussed.

Influence of Foliar Fungicides and Seed Treatments on Powdery Mildew, Septoria, and Leaf Rust Epidemics on Winter Wheat

Three winter wheat cultivars were grown under an optimum crop management system for Pennsylvania at two locations during 1984 and 1985. The seed-treatment fungicide triadimenol and or a foliar spray of triadimefon and mancozeb were applied for disease control. The foliar spray was applied as a tank mix at growth stage 6 (Feekes scale). Differences in AUDPC and grain yield among cultivars and cultivar×treatment interactions were obsered. (…)

SCREENING FOR PHYTO-PROTECTANTS TO GUARD CORN SEEDS/SEEDLINGS FROM SOUTHERN CORN ROOTWORM FEEDING INJURY

A screening program was developed to detect chemicals without acute toxicity that could protect seedling corn from injuiy by southern corn rootworm (SCR), Diabrotica undecimpunctata howardi Barber. Crude plant extracts, purified secondary plant compounds and agricultural fungicides were screened in a no-choice laboratory bioassay using germinating corn seeds in soil. Promising candidates were further tested in a greenhouse assay. Chemicals were evaluated on the ability to reduce the number of plants damaged and the severity of SCR feeding. A seed treatment fungicide, thiram, energed as the most effective compound in these tests. The term phyto-protectant is used to describe substances which prevent or reduce the severity of insect damage to plants without regard to their specific mode of action. The usefulness and limitations of this screening program and terminology are discussed as well as implications for futher screening of phyto-protectants.

Controlling Bakanae (BAK) and Foot Rot Disease with Fungicide Seed Treatments

Controlling Bakanae (BAK) and Foot Rot Disease with Fungicide Seed Treatments

An assessment of the need for routine use of organomercurial cereal seed treatment fungicides

Abstract Seed crops need protection from a build-up of seed-borne pathogens, but it is not known whether such protection is necessary for the large proportion of seed which is sown to produce a crop for consumption. Trials have been carried out on farms in Scotland over a 5-year period to assess the risk of sowing untreated cereal seed. Over 220 comparisons were made, with 41 stocks of spring barley and 36 of winter wheat. The mean establishment of winter wheat was increased from 59% to 65% with treatment, but that of barley was not affected. The amount of seedling disease in untreated crops was approximately 2–3 times the level in treated crops. There were, however, no significant differences of overall mean yield associated with the absence of treatment for either wheat or barley. There were significant differences in yield in individual comparisons, but these were unrelated to significant differences in establishment or seedling disease, and they were considered to be due to intrafield variation, and not to the effect of treatment. It is considered that seed treatment to protect against seed-borne pathogens, other than wheat or barley loose smut if known to be present, is not necessary for certified seed being sown to produce a non-seed crop. The use of organomercury in seed treatments in Great Britain could be reduced from 17 to 6 tonnes per annum.

Effects of Chloride Fertilizer and Systemic Fungicide Seed Treatments on Common Root Rot of Barley

Effects of Chloride Fertilizer and Systemic Fungicide Seed Treatments on Common Root Rot of Barley