Range Of Fungicides Research Articles

Managing spot blotch disease in wheat: Conventional to molecular aspects.

Spot blotch (SB) caused by Bipolaris sorokiniana (teleomorph Cochliobolus sativus) is one of the devastating diseases of wheat in the warm and humid growing areas around the world. B. sorokiniana can infect leaves, stem, roots, rachis and seeds, and is able to produce toxins like helminthosporol and sorokinianin. No wheat variety is immune to SB; hence, an integrated disease management strategy is indispensable in disease prone areas. A range of fungicides, especially the triazole group, have shown good effects in reducing the disease, and crop-rotation, tillage and early sowing are among the favorable cultural management methods. Resistance is mostly quantitative, being governed by QTLs with minor effects, mapped on all the wheat chromosomes. Only four QTLs with major effects have been designated as Sb1 through Sb4. Despite, marker assisted breeding for SB resistance in wheat is scarce. Better understanding of wheat genome assemblies, functional genomics and cloning of resistance genes will further accelerate breeding for SB resistance in wheat.

Seed treatment with the fungicide fluopyram limits cotyledon infection by Leptosphaeria maculans and reduces blackleg of canola

Blackleg, caused by Leptosphaeria maculans, is a serious disease on canola or rapeseed in Canada, Australia and Europe. Disease levels have increased in western Canada recently and additional tools are needed to improve blackleg management. Seed treatment can be a cost-effective approach against blackleg, but there is currently no registered seed-treatment product targeting aboveground blackleg infection. In this study, a range of fungicides was evaluated for control of cotyledon infection by L. maculans and blackleg of canola. Under controlled environmental conditions, fluopyram showed greater efficacy than fluquinconazole (used against blackleg in Australia) in limiting cotyledon infection, while Prosper® EverGol and Helix® Vibrance (industry standards) were ineffective. Fluopyram at a rate of 30–150 g/100 kg seed generally inhibited cotyledon infection and this efficacy was not affected by delayed soil moisture for 3 weeks after planting. This indicates that the efficacy will unlikely be affected by a slight delay in germination due to a soil moisture deficit after seeding. In addition to typical mechanisms of succinate dehydrogenase inhibitor fungicides, fluopyram also induced expression of the indicator gene coding PR-1 proteins substantially, indicating the potential for inducing disease resistance. In field trials at 75 and 150 g/100 kg seed, fluopyram reduced the infection on cotyledons resulting from pricking inoculation on both susceptible and resistant canola cultivars, potentially limiting the infection into the stem. These seed treatment rates reduced the disease severity index (DSI) substantially on the susceptible cultivar, while DSI was low on a resistant cultivar with or without fluopyram treatment.

Evaluation of Fungicides and Management Strategies against Cercospora Leaf Spot of Olive Caused by Pseudocercospora cladosporioides

Cercospora leaf spot of olive (CLSO), caused by Pseudocercospora cladosporioides, is one of the most important foliar diseases of olives worldwide. This study aimed to evaluate the effect of a wide range of fungicides on mycelial growth and conidial germination of P. cladosporioides in vitro, and to evaluate the effect of several fungicides, application timings and management strategies (conservative and risky) to control CLSO under field conditions. Of the studied fungicides, strobilurin compounds and benomyl were the most effective active ingredients, followed by folpet, captan and maneb, in inhibiting mycelial growth and conidial germination. The pyraclostrobin + boscalid treatment was effective under field conditions, even without the application of supplementary copper. Treatments conducted in October or March were more effective than those conducted in May. Management strategies based on the author’s experience reduced copper applications up to 32.0% and 50.0% (conservative and risky strategy, respectively) in comparison to the reduction with the traditional strategy, without increasing CLSO incidence. This work provides useful information about effective formulations against CLSO and a reduction in unnecessary fungicide applications in an effort to implement IPM in olive orchards under Mediterranean conditions.

Novel Combinations of Agents Targeting Translation That Synergistically Inhibit Fungal Pathogens.

A range of fungicides or antifungals are currently deployed to control fungi in agriculture or medicine, but resistance to current agents is growing so new approaches and molecular targets are urgently needed. Recently, different aminoglycoside antibiotics combined with particular transport inhibitors were found to produce strong, synergistic growth-inhibition of fungi, by synergistically increasing the error rate of mRNA translation. Here, focusing on translation fidelity as a novel target for combinatorial antifungal treatment, we tested the hypothesis that alternative combinations of agents known to affect the availability of functional amino acids would synergistically inhibit growth of major fungal pathogens. We screened 172 novel combinations against three phytopathogens (Rhizoctonia solani, Zymoseptoria tritici, and Botrytis cinerea) and three human pathogens (Cryptococcus neoformans, Candida albicans, and Aspergillus fumigatus), showing that 48 combinations inhibited strongly the growth of the pathogens; the growth inhibition effect was significantly greater with the agents combined than by a simple product of their individual effects at the same doses. Of these, 23 combinations were effective against more than one pathogen, including combinations comprising food-and-drug approved compounds, e.g., quinine with bicarbonate, and quinine with hygromycin. These combinations [fractional inhibitory combination (FIC) index ≤0.5] gave up to 100% reduction of fungal growth yield at concentrations of agents which, individually, had negligible effect. No synergy was evident against bacterial, plant or mammalian cells, indicating specificity for fungi. Mode-of-action analyses for quinine + hygromycin indicated that synergistic mistranslation was the antifungal mechanism. That mechanism was not universal as bicarbonate exacerbated quinine action by increasing drug uptake. The study unveils chemical combinations and a target process with potential for control of diverse fungal pathogens, and suggests repurposing possibilities for several current therapeutics.

White blister disease control in radish seed crops

Albugo candida is a significant pathogen of many brassica species causing leaf spotting but, more importantly, hypertrophy of flowering stems (“stagheads”) resulting in yield loss. No chemicals are currently registered for white blister control in New Zealand. Little research has been carried out on white-blister management. The implications of seed transmission and subsequent disease expression in radish are not fully understood and control has relied on products containing metalaxyl-m+mancozeb. A range of fungicides were evaluated in two field trials and a pot trial for both efficacy against the disease and effect on radish yield. While metalaxyl-m+mancozeb improved yields in field trials and provided good disease suppression in pot trials, the fungicides azoxystrobin, boscalid+pyraclostrobin and cyazofamid were also equally effective or better than metalaxyl-m+mancozeb. Treatments were able to suppress leaf spotting by up to 90% and inflorescence infection by 50%. Seed yield increases of up to 67% were recorded. Potential new control options for white blister were identified providing alternatives to metalaxyl-m+mancozeb and thus contributing to an anti-resistance strategy.

Widespread contamination of wildflower and bee-collected pollen with complex mixtures of neonicotinoids and fungicides commonly applied to crops

There is considerable and ongoing debate as to the harm inflicted on bees by exposure to agricultural pesticides. In part, the lack of consensus reflects a shortage of information on field-realistic levels of exposure. Here, we quantify concentrations of neonicotinoid insecticides and fungicides in the pollen of oilseed rape, and in pollen of wildflowers growing near arable fields. We then compare this to concentrations of these pesticides found in pollen collected by honey bees and in pollen and adult bees sampled from bumble bee colonies placed on arable farms. We also compared this with levels found in bumble bee colonies placed in urban areas. Pollen of oilseed rape was heavily contaminated with a broad range of pesticides, as was the pollen of wildflowers growing nearby. Consequently, pollen collected by both bee species also contained a wide range of pesticides, notably including the fungicides carbendazim, boscalid, flusilazole, metconazole, tebuconazole and trifloxystrobin and the neonicotinoids thiamethoxam, thiacloprid and imidacloprid. In bumble bees, the fungicides carbendazim, boscalid, tebuconazole, flusilazole and metconazole were present at concentrations up to 73nanogram/gram (ng/g). It is notable that pollen collected by bumble bees in rural areas contained high levels of the neonicotinoids thiamethoxam (mean 18ng/g) and thiacloprid (mean 2.9ng/g), along with a range of fungicides, some of which are known to act synergistically with neonicotinoids. Pesticide exposure of bumble bee colonies in urban areas was much lower than in rural areas. Understanding the effects of simultaneous exposure of bees to complex mixtures of pesticides remains a major challenge.

Influence of Selected Fungicides on Efficacy of Clethodim and 2,4-DB

Abstract A range of fungicides and herbicides can be applied to control pests and optimize peanut yield. Experiments were conducted in North Carolina to define biological and physicochemical interactions when clethodim and 2,4-DB were applied alone or with selected fungicides. Pyraclostrobin consistently reduced large crabgrass [Digitaria sanguinalis (L.) Scop.] control by clethodim. Chlorothalonil and tebuconazole plus trifloxystrobin reduced large crabgrass control by clethodim in two of four experiments while prothioconazole plus tebuconazole and flutriafol did not affect control. Palmer amaranth [Amaranthus palmeri S. Wats] control by 2,4-DB was not affected by these fungicides. Although differences in spray solution pH were noted among mixtures of clethodim plus crop oil concentrate or 2,4-DB and fungicides, the range of pH was 4.40 to 4.92 and 6.72 to 7.20, respectively, across sampling times of 0, 6, 24, and 72 h after solution preparation. Permanent precipitates were formed when clethodim, crop oil concentrate, and chlorothalonil were co-applied at each sampling interval. Permanent precipitates were not observed when clethodim and crop oil concentrate were included with other fungicides or when 2,4-DB was mixed with fungicides. Significant positive correlations were noted for Palmer amaranth control by 2,4-DB and solution pH but not for clethodim and solution pH.

The effects of copper on microbial activity and the degradation of atrazine and indoxacarb in a New Zealand soil

Copper is present in a range of fungicides as well as in some animal manures and biosolids that are applied to agricultural soils as fertilisers. Elevated and increasing levels of copper in agricultural soils are of worldwide concern. Copper is toxic to soil microorganisms and has been reported to reduce the ability of soil microorganisms to degrade pesticides. A glasshouse study was undertaken to determine if copper inhibited the degradation of atrazine and indoxacarb in soil. A fine sandy loam agricultural soil was fortified with copper at five concentrations over a concentration range of 0–1000 mg/kg copper, then field-aged for 6 months prior to treatment with either indoxacarb or atrazine at a rate of 2 mg/kg. The soils were sampled twice at intervals based on published half-lives. The samples were analysed for a range of parameters including total and bioavailable copper, urease and phosphatase activity, ergosterol and either indoxacarb or atrazine and its degradation products. The soil microbial biomass and enzyme activities decreased with increasing copper concentration (p < 0.05). There were no significant differences in soil atrazine and indoxacarb concentrations between the copper levels. At sampling time two, the concentrations of hydroxyatrazine in treatments containing the three highest copper concentrations were significantly greater (p < 0.05) than for the control soil. Our results indicate that copper does not inhibit the first step of indoxacarb and atrazine degradation, but may affect degradation of secondary metabolites like hydroxyatrazine in soil.

Improving Fungicide-Based Management of Ray Blight Disease in Tasmanian Pyrethrum Fields.

Ray blight disease, caused by Phoma ligulicola var. inoxydablis, is a serious threat to the Tasmanian pyrethrum industry. The management of this disease relies upon the strategic application of fungicides in early spring. A range of fungicides were assessed for their efficacy in controlling ray blight disease in Tasmanian pyrethrum fields, and the primary objective of this study was to increase fungicide options available to growers in different resistance groups. Fungicides were assessed under in vitro conditions, within five replicated-plot field trials over three seasons (2004 to 2006) and in single-plot trials over eight fields in 2005. In each of the field trials, regular assessments of disease intensity (defoliation severity and the incidence of stems with ray blight), stem height, and the number of flowers produced on each stem were made using stems as the primary sampling unit. Canopy reflectance at 830 nm and the Difference Vegetative Index, measured using a handheld multispectral radiometer, also were used to compare fungicide effects on green leaf area. The effect of fungicides on the dry weight of flowers, pyrethrin content within the flowers, flower maturity, and pyrethrin yield were determined. Under in vitro conditions, boscalid reduced both conidial germination and mycelial growth at concentrations of at least 0.16 μg/ml. In field trials 1 and 2 (in 2004), the premixed formulation of pyraclostrobin + boscalid (Pristine) increased pyrethrin yield by an average of 79% compared with nontreated plots over the two locations. Furthermore, in single-plot trials, pyraclostrobin + boscalid increased pyrethrin yield by 134 and 60% compared with the industry-recommended protocol (single application of azoxystrobin at 150 g a.i./ha [Amistar WG] and two additional applications of a tank mixture of difenoconazole at 125 g a.i./ha [Score] and chlorothalonil at 1,008 liters a.i./ha [Bravo 720] at 14- to 21-day intervals) and nontreated plots, respectively. In field trials 3 (in 2005) and 4 and 5 (in 2006), similar yield benefits also were produced by applying pyraclostrobin (Cabrio SC) or boscalid (Filan) alone or in combination with chlorothalonil (Bravo 720) at 1.4 liters of product per hectare, regardless of the rates of pyraclostrobin (250 and 125 g a.i./ha) and boscalid (500 and 250 g a.i./ha) used. These data were used to recommend the incorporation of boscalid to improve the fungicide-based management of ray blight disease. This decreases the number of applications of both strobilurin and triazole fungicides which have been used extensively for the management of ray blight and other diseases in Tasmanian pyrethrum fields and are prone to fungicide resistance development.

Application of fungicides to reduce yield loss in anthracnose-infected lupins

A range of fungicides were evaluated for control of anthracnose ( Colletotrichum lupini) in lupin. Glasshouse investigation identified fungicides that reduced disease severity with varying degrees of efficacy. When applied 1 d prior to infection, azoxystrobin, chlorothalonil, mancozeb and copper oxychloride fungicides were highly effective. Systemic fungicides such as tebuconazole, benomyl and carbendazim were less effective. Application timing was important; fungicides such as chlorothalonil and mancozeb were less effective when applied 5 d prior to infection compared with 1 d prior. Application after infection was ineffective for all fungicides. In field experiments application of azoxystrobin, mancozeb or chlorothalonil during flowering and podding reduced incidence of anthracnose infection on pods. Yield responses occurred in moderately susceptible, moderately resistant or resistant cultivars. Seed infection was reduced but not eradicated. Application of foliar fungicides for anthracnose control is potentially a viable management option for lupin production in high anthracnose risk areas of Western Australia.

Disease management of winter wheat with reduced doses of fungicides in Northern Ireland

Trials in Northern Ireland from 1994–2002 with a range of fungicides, applied at a range of doses to winter wheat, generally showed improved retention of green leaf area (GLA) due to good control of the principal pathogen Mycosphaerella graminicola. This led to significant increases in yield, thousand grain weight and profitability particularly when cultivars susceptible to M. graminicola were treated. Frequently, the maximum profitability was achieved with fungicides applied at 50% or less of the manufacturer's recommended dose. Overall profitability with cultivars resistant to M. graminicola was higher than with susceptible cultivars and treatment of resistant cultivars with fungicides did not significantly increase profitability any further. This indicates that, for cereal growers in N. Ireland, use of resistant cultivars should be the primary method of control of M. graminicola. A comparison of a spray programme at GS 32 and 39 compared with one with an extra spray at GS 59, showed tendencies towards improvement in GLA retention and yield with a susceptible cultivar, but none with a resistant. However, this was not statistically significant and with current grain prices would not have been translated into increased profitability. Results generally point to the importance in N. Ireland of using resistant cultivars and to applications at GS 32 and 39 if susceptible cultivars are grown.

Evaluation of fungicides for the control of Botryosphaeria protearum on Protea magnifica in the Western Cape Province of South Africa

A range of fungicides was tested in vitro for their effect on mycelial inhibition. Selected products showing potential for disease control were then further tested under field conditions. The most effective fungicides in the in vitro tests were tebuconazole, benomyl, prochloraz mc, iprodione and fenarimol. In field trials, a 25–85% reduction in the occurrence of stem cankers caused by Botryosphaeria protearum was achieved if fungicides were applied or sanitation pruning was implemented. The best control was obtained with treatments of prochloraz mc alternated with mancozeb. Applications of bitertanol and fenarimol also significantly reduced the occurrence of cankers.

Disease management of spring barley with reduced doses of fungicides in Northern Ireland

Trials over 8 years in Northern Ireland with a range of fungicides, applied at a range of doses, to spring barley showed a reduction in disease and increase in green leaf area and yield, particularly from 1993 to 97, when mildew ( Blumeria graminis f.sp. tritici) was the main disease. Fungicides in those years had considerable effect even at low doses. In the latter years of the project, there was relatively little mildew or leaf blotch ( Rhynchosporium secalis) and the effect of fungicides was less. Results generally indicate that the potential of disease resistance of cultivars should be fully exploited and prophylactic spraying at present is unlikely to be profitable.

Stimulation of Armillaria mellea by phenolic fungicides

SummaryPhenolic fungicides, which were initially fungicidal to mycelium of Armillaria mellea on the surface of well‐colonised wood billets, eventually stimulated the growth of A. mellea. An extensive growth of rhizomorphs was produced from A. mellea inoculum, which had been exposed to phenolic chemicals for 3 months, compared to few or no rhizomorphs produced from inoculum exposed to water or a suspension of a non‐phenolic fungicide, fenpropidin. Inoculated privet plants grown either in pots or under field conditions were treated with a range of fungicides; fenpropidin, phenyl phenol, cresylic acid or water (control) was applied every 6 months over 21/2 yr. Fenpropidin caused a slightly (but significantly) lower incidence of infection than occurred in untreated plants, but the phenolic fungicides, cresylic acid and phenyl phenol, did not reduce the incidence of infection. The severity of infection (% root circumference colonised at 5 cm depth) was greater following cresylic acid treatments than the other fungicides or water‐treated controls. Use of phenolic fungicides such as cresylic acid for the control of A. mellea may therefore be counter‐productive.

DMI sensitivity and cross-resistance patterns of Rhynchosporium secalis isolates from South Africa

Isolates of R. secalis were collected yearly from the Rûens area of the Western Cape during the 1993–1995 growing seasons. These isolates were evaluated in vitro to determine sensitivity to triazole fungicides (triadimenol, tebuconazole, flusilazole and propiconazole). The sensitivity fluctuated but in 1995 isolates were significantly less sensitive towards triadimenol than in the previous two years. In a second experiment, isolates collected from two fields with a 5–6 year history of triadimenol seed treatments and tebuconazole applications were evaluated for their fungicide sensitivity. A significant positive correlation was observed between tebuconazole and triadimenol sensitivity among R. secalis isolates from these fields. However, such a correlation was not found within the R. secalis population collected during 1993–1995 where shorter crop rotation patterns and a range of fungicides were applied. In a third experiment, the fungicide sensitivity of local R. secalis isolates was evaluated towards two new triazole fungicides, namely bromuconazole and triticonazole. Correlation coefficients observed between these new triazoles and those previously applied in South Africa were not significantly positive. The lack of significant cross-resistance has important practical implications for management of fungicide resistance.

Fungicidal control of foliar diseases of white lupin ( Lupinus albus)

A range of fungicides was tested against rust ( Uromyces lupinicolus) and brown spot ( Pleiochaeta setosa) on autumn-sown white lupin ( Lupinus albus) in three experiments in harvest years 1995, 1997 and 1998. Rust was severe in all three years but did not develop in an additional experiment in 1996. Brown spot occurred only in 1997 and 1998 when natural inoculum was augmented by an artificial source and weather conditions were favourable for inoculum dispersal and disease development. Tebuconazole was the only fungicide tested that controlled rust consistently, whereas iprodione+thiophanate-methyl, tebuconazole and prochloraz each decreased the severity of brown spot. Yield increases in 1997 and 1998 were thought to be attributable mainly to control of rust. Fungicides were most effective when applied as soon as symptoms were observed. Two applications of an effective fungicide generally controlled disease more than a single application; a third application gave no additional benefit.

Evaluation of fungicides for control ofAlternarialeaf spot ofPseudopanax

Abstract Alternaria tenuissima causes a leaf spot disorder of Pseudopanax ’Gold Splash’, a New Zealand native shrub with export potential. A range of fungicides viz., bitertanol, captafol, chlorothalonil, dichlofluanid, iprodione, mancozeb, prochloraz, procymidone, propineb, and vinclozolin were tested for efficacy against the pathogen. Three techniques were used based on growth on: (1) fungicide amended media; (2) leaf disc; and (3) intact plants. The efficacy of fungicides in agar was not directly related to their effectiveness on leaf discs or on intact plants. In contrast, all fungicides effective on leaf discs were also effective on intact plants. The leaf disc technique showed that bitertanol, chlorothalonil, iprodione, prochloraz, and vinclozolin became less effective 4 weeks following application. In contrast, captafol, dichlofluanid, and propineb were effective inhibitors throughout the 4 weeks tested by the leaf disc technique. On pot plants in a greenhouse, mancozeb was the most effective prote...

Impairment of reproductive health in women occupationally exposed to thiram

In two years a range of fungicides was used to control rust (Uromyces viciae-fabae) on spring-sown field beans (Vicia faba). In 1984 fenpropimorph, maneb, mancozeb, maneb plus mancozeb, propiconazole, thiram, triadimefon and zineb-polyethylene thiuram disulphide plus tridemorph were applied once or twice and compared with no fungicide. In 1985 the experiment was repeated with the addition of benodanil. In 1984 there was very little rust or other foliar disease and the effects of treatments on yield were small. In 1985 rust was first found in late June and became severe on untreated plots in August. All the fungicides reduced the incidence of rust but the amount of control differed with frequency of application and on different dates of disease assessment. In 1985 chocolate spot (Botrytis fabae) also became severe in late August. All the fungicides reduced chocolate spot but maneb plus mancozeb was the most effective. In 1985 yields were increased from 5 · 6 to 7 · 7 t/ha by maneb plus mancozeb applied once. Other fungicides gave smaller yield increases. Yield increases given were attributable mainly to control of rust but partly to control of chocolate spot. Yield increases given by non-systemic fungicides came mainly from increases in the weight of individual grains; those yield increases given by systemic materials came, in addition, from better pod retention.

Chemical control of powdery mildew in green peas.

A range of fungicides was assessed on late-sown green peas in south-east Queensland and north-west Tasmania for the control of powdery mildew caused by Oldium sp. Triadimefon (Bayleton 125 EC) at 500 mL/ha applied at early flowering gave excellent control under high disease pressure in both States, In Tasmania, single sprays with tebuconazole, propiconazole or fenpropimorph also reduced leaf and pod infections significantly with corresponding increases in yield. Wettable sulphur was effective in both States. It has a significant chemical cost advantage over systemic fungicides and is acceptable to biodynamic/organic growers.

Efficacy of reduced volume and reduced dose rate spray programmes in apple orchards

Four large-scale randomized block experiments in commercial apple orchards (cv. Cox) in Kent, Southern England, compared the efficacy of very-low-volume (VLV) spraying using Micron X1 spinning-disc nozzles at a volume rate of 50 l ha −1 with low-volume (LV) spraying using small-orifice hollow-cone hydraulic nozzles at a volume rate of 100 l ha −1 and conventional medium-volume (MV) spraying using standard hydraulic nozzles at a volume rate of 440–500 l ha −1. A range of fungicides, insecticides and plant growth regulators and nutrients was used in a full season's spray programme in each experiment, the full and one-quarter of the manufacturer's recommended dose rate being investigated. Conventional MV spraying with full manufacturer's dose rates was the most liability effective merthod of applying the full range of crop protection chemicals, but VLV and LV spraying at the full dose rate were often as effective, or nearly as effective, and satisfactory for commercial purposes. Exceptions were control of blossoms wilt ( Sclerotinia laxa f. sp mali) with sprays of vinclozolin, and extension growth cotrol with the plant growht regulator paclobutrazol where VLV spraying was significantly less effective than MV spraying. Reducing dose rate by 75% resulted in a significant, though small, reduction in efficacym and greatly reduced dose rates of calcium chloride application resulting from VLV (approximately one-tenth dose rate) and LV (approximately one-fifth dose rate) spraying at the same concentration as MV spraying were identified in raising the concentration of calcium in the fruits. Commercial success with greatly reduced dose and volume rates will require careful orchard monitoring for pests and diseases, coupled with a flexible management strategy of adjust choice of pesticide, frequency of application and dose and volume rate suit prevailing conditions.