Eradicant Activity Research Articles

Pre- and post-anthesis activity of fenbuconazole and triforine against blueberry flower infection by Monilinia vaccinii-corymbosi

The fungus Monilinia vaccinii-corymbosi infects open blueberry flowers via stigma and style, causing mummy berry disease. Management of flower infection in this pathosystem relies on multiple fungicide applications during bloom. However, flowers that open between spray applications may remain prone to infection because the stigmatic surface (infection court) is not exposed to active ingredient, unless there is systemic movement in the pistil and/or eradicant activity in the ovary. To quantify and compare pre- and post-infection fungicidal activity in flowers, we examine here the ability of two systemic fungicides to prevent flower infection and subsequent fruit colonization by M. vaccinii-corymbosi. The fungicides were applied before or after anthesis (first day of open bloom) in an experimental system where flower development stages and inoculation timing were monitored and controlled precisely. In greenhouse experiments with potted rabbiteye blueberry plants, treatment with fenbuconazole, triforine, or water was made when sufficient numbers of flower clusters at anthesis and earlier pre-anthesis stages were present simultaneously. Treated flowers (n = 10,992) were tagged, observed daily, and individual flowers were pollinated and inoculated 1 day after opening. Fruit from treated flowers were assessed for incidence and severity of mummification. Both fungicides provided excellent protection to newly opened flowers that were at the anthesis stage during fungicide application, but differed in their activity in unopened flowers at pre-anthesis stages during application. Fenbuconazole suppressed infection in unopened flowers that were on average 2.5 days pre-anthesis at the time of application, whereas triforine provided substantial protection to earlier flower stages up to 6.5 days pre-anthesis. In a separate experiment to quantify post-infection activity (n = 13,068 flowers), fenbuconazole and triforine significantly suppressed fruit mummification when applied within 2 and 5 days after anthesis, respectively (with inoculation and pollination 1 day after anthesis). Thus, the total window of activity of fenbuconazole in blueberry flowers was 4.5 days, whereas that of triforine was at least 11.5 days. Prevention of ovary colonization by eradicant activity appeared to be the predominant mode for superior activity of triforine against M. vaccinii-corymbosi in flowers. To better manage flower infection by this pathogen, active ingredients such as triforine with superior activity in floral tissues need to be identified and characterized.

Management of tomato leaf mould caused by Cladosporium fulvum with trifloxystrobin

The protective, curative and eradicant activity of the strobilurin fungicide trifloxystrobin against Cladosporium fulvum on tomatoes was determined under growth chamber and greenhouse conditions. In growth chamber experiments chlorothalonil applied at 100 μg ml −1 was used as standard fungicide treatment. Seven-week-old tomato plants, hybrid Alma F1, were inoculated by conidial suspension. Protective treatments were carried out by spraying plants 24, 48 and 96 h before inoculation at the doses of 5, 10 and 20 μg a.i. ml −1. Curative treatments were carried out with the same doses, at the same time intervals after inoculation. Additionally, spray treatments were applied after the appearance of the symptoms to evaluate the anti-sporulant activity of the fungicides tested. Protective treatments of trifloxystrobin applied 24 and 48 h before inoculation provided disease control higher than 88% at all the application doses tested, while only the dose of 20 μg a.i. ml −1 was highly effective when applied 96 h before the inoculation of the plants (IOP). The curative treatments were less effective than the protective treatments. Post-inoculation treatments of trifloxystrobin at 10 or 20 μg ml −1 were efficacious only when applied 24 or 48 h after IOP, with limited activity when applied 96 h after inoculation. Eradicant treatments of trifloxystrobin provided satisfactory anti-sporulant activity when applied at the dose rate of 20 μg ml −1. Applications of trifloxystrobin at the rates of 5 or 7.5 g a.i. 100 l −1 of spray solution carried out during a 2-year period (2004–2005), in the greenhouse, demonstrated the validity of the above findings, providing control efficacy values higher >90%. Moreover, during both years of the study, applications of trifloxystrobin either at 5 or 7.5 g a.i. 100 l −1, reduced spore production significantly on diseased tomato leaves. The results of the study showed that trifloxystrobin may play a crucial role as part of an integrated chemical control programme for tomato leaf mould caused by C. fulvum.

A foliar disease model for use in wheat disease management decision support systems

AbstractA model of winter wheat foliar disease is described, parameterised and tested for Septoria tritici (leaf blotch), Puccinia striiformis (yellow rust), Erysiphe graminis (powdery mildew) and Puccinia triticina (brown rust). The model estimates disease‐induced green area loss, and can be coupled with a wheat canopy model, in order to estimate remaining light‐intercepting green tissue and hence the capacity for resource capture. The model differs from those reported by other workers in three respects. First, variables (such as weather, host resistance and inoculum pressure) that affect disease risk are integrated in their effect on disease progress. The agronomic and meteorological data called for are restricted to those commonly available to growers by their own observations and from meteorological service networks. Second, field observations during the growing season can be used both to correct current estimates of disease severity and to modify parameters that determine predicted severity. Third, pathogen growth and symptom expression are modelled to allow the effects of fungicides to be accounted for as protectant activity (reducing infections that occur postapplication) and eradicant activity (reducing growth of presymptomatic infections). The model was tested against data from a wide range of sites and varieties and was shown to predict the expected level of disease sufficiently accurately to support fungicide treatment decisions.

Iprovalicarb has potential for the control of downy mildew of pearl millet

The effect of Melody Duo 66.75 wp was assayed on pearl millet downy mildew (PMDM). This novel fungicide, a combined preparation of iprovalicarb and propineb, controlled all developmental stages of Sclerospora graminicola. The protective effect of this preparation was due to iprovalicarb and was equipotent to metalaxyl-containing Apron 35 sd and Ridomil 72 MZ wp, whereas the eradicant activity of Melody Duo exceeded that of the two latters at comparative doses. Iprovalicarb was translocated acropetally and exhibited systemically an excellent curative activity. The downy mildewed pearl millet plants recovered after foliar treatments with the preparations. The exploitation of Melody Duo 66.75 wp is recommended against pearl millet downy mildew disease.

The use of sodium carbonate to improve curing treatments against green and blue moulds on citrus fruits.

The effectiveness of curing oranges and lemons at 33 degrees C for 65h followed by storage under ambient and cold-storage conditions was investigated. This treatment effectively reduced the incidence of Penicillium digitatum (Pers) Sacc and P italicum Wehmer decay on inoculated and naturally infected oranges and lemons stored at 20 degrees C for 7 days. However, it failed to control green and blue mould infections on fruits placed in long-term cold storage, except green mould on oranges, which was effectively controlled. Dipping fruits in a sodium carbonate solution (20 g litre(-1)) for 2.5 min following a curing treatment at 33 degrees C for 65 h satisfactorily reduced green and blue mould incidence during subsequent long-term storage at 4 degrees C on oranges and at 10 degrees C on lemons. The efficacy was greater on injured fruits inoculated after the combination of treatments was applied, achieving a 60-80% reduction in decay in comparison with the curing treatment alone in all cases. A significant reduction of blue mould was also observed on fruits inoculated both before the treatments and on those re-inoculated after the treatments, demonstrating both protectant and eradicant activity. Thus, combining curing at 33 degrees C for 65 h with sodium carbonate treatment effectively controlled these post-harvest diseases on artificially inoculated citrus fruits and protected against re-infection. With naturally inoculated lemons, curing followed by sodium carbonate significantly reduced both green and blue mould incidence, but was not superior to curing alone. With naturally infected oranges, curing significantly reduced blue mould, but decay was not reduced further when followed by sodium carbonate treatment.

Protective, Curative and Eradicant Activity of the Strobilurin Fungicide Azoxystrobin against Cercospora beticola and Erysiphe betae

AbstractThe protective, curative and eradicant activity of the strobilurin fungicide azoxystrobin against Cercospora beticola and Erysiphe betae on sugar beet was determined under growth chamber conditions. Difenoconazole and chlorothalonil were used as standard fungicides against C. beticola, while chlorothalonil was replaced by sulphur against E. betae. Fungicides were applied before (protective treatments) and after (curative treatments) inoculation at 24, 48 and 96 h intervals, respectively. An additional spray treatment was applied after the appearance of the symptoms to evaluate the eradicant activity of the fungicides tested. Applications of azoxystrobin at 16 μ/ml provided 89–94% and 95–97% disease control against C. beticola and E. betae, respectively. Curative treatments of azoxystrobin either at 8 or 16 μg/ml provided control of Cercospora leaf‐spot higher than 90% only when it was applied 24 h after inoculation of the plants. Comparatively, chlorothalonil (100 μg/ml) provided satisfactory control of C. beticola when applied in protective treatments (83–87% disease control) but showed little activity when applied after the inoculation of the seedlings (45–76% disease control). High control efficacy against E. betae was also obtained by protective applications of sulphur (600 μg/ml) but the fungicide failed to provide satisfactory disease control, particularly when applied for 48 or 96 h after inoculation of seedlings. Difenoconazole (8 μg/ml) gave excellent protective and curative activity against both pathogens. Eradicative treatments with azoxystrobin provided high antisporulant activity of 94–96% and 85–93% against C. beticola and E. betae, respectively. Similarly, high antisporulant activity was also provided by difenoconazole, while postsymptom applications of chlorothalonil and sulphur provided significantly lower antisporulant activity against C. beticola and E. betae, respectively. Such results encourage the evaluation of azoxystrobin under field conditions to determine optimal treatment schedules and to select possibly partner fungicides for use in mixtures.

Residual and Eradicant Activity of Fungicides against Apple Sooty Blotch Caused by Gloeodes pomigena

Residual and Eradicant Activity of Fungicides against Apple Sooty Blotch Caused by <I>Gloeodes pomigena</I>

Effects of fungicide spray timing on winter wheat disease control

A field experiment of novel systematic design was established on 17 sites in the three years 1988–90 to compare the effect of spray timing on the disease control provided by fungicides. At each site one set of plots received applications of a mixture of fenpropimorph and prochloraz or triadimenol, tridemorph and chlorothalonil fungicides, applied at successively later start dates to produce a series of temporally and spatially related, but discrete, epidemics curtailed at consecutively later stages of development between GS32 and GS75. A second set of plots was treated with a single spray of one of a set of the nine candidate fungicides between GS32 and GS71. Disease developed at each site, with moderate septoria leaf spot (Septoria tritici) at five of the eight sites in 1988 and four of the seven sites in 1989. Erysiphe graminis f.sp. tritici was present at two sites in 1988, four sites in 1989 and one site only in 1990. Puccinia striiformis (four sites only in 1989 and 1990) and brown rust (one site in each year) were less common. The systematic treatments showed consistent relationships between green leaf retention during grain filling and yield. They also provided clear indications that epidemics of foliar disease initiated before flag leaf emergence had the greatest impact on yield. After this stage, yield loss averaged 27.2 kg ha−1 for each day that elapsed before fungicide was applied. The sequential single spray treatments showed marked differences between the protectant and eradicant activity of the different fungicides used. Each disease was most effectively controlled on the final leaf by treatment at or immediately after its emergence. Chlorothalonil was as effective as any of the fungicides tested against septoria, when applied before flag leaf emergence, but was inferior when applied after this stage. The fungicides were equally effective against yellow rust when applied just before symptoms were detected, when spray timing appeared to be more important than choice of fungicide. The response of brown rust to fungicides was similar, except that chlorothalonil was the least effective. For mildew, timing seemed to be less important, although sprays applied immediately after leaf emergence provided the best control on each individual leaf layer. Yield was well related to disease and green leaf area late in the season, these factors being more important than which disease was present, which fungicide, and which cultivar were used.

Time of Infection ofGloeodes pomigenaandSchizothyrium pomion Apple in North Carolina and Potential Control by an Eradicant Spray Program

Infection of apples (Malus × domestica) by Gloeodes pomigena (cause of sooty blotch) occurred by mid-May, 10-21 days after petal fall. Infection by Schizothyrium pomi (cause of flyspeck) occurred by late May or early June. Infection by both pathogens was extensive by the first week of June. The time that sooty blotch and flyspeck symptoms became visible was related to the frequency of rainfall in June. Benomyl combined with captan or mancozeb applied when sooty blotch first was observed in the orchard demonstrated eradicant activity in 1987 but not in 1989 or 1990. At harvest, coverage of the fruit surface with sooty blotch and flyspeck (severity) in eradicant treatments which included benomyl was not significantly different from the standard protectant treatments (.)

Effect of Temperature and Wetness Duration on Apple Fruit Infection and Eradicant Activity of Fungicides Against Botryosphaeria dothidea

Effect of Temperature and Wetness Duration on Apple Fruit Infection and Eradicant Activity of Fungicides Against Botryosphaeria dothidea

The use of rainfall and accumulated mean temperature to indicate fungicide activity in the control of leaf diseases of winter wheat in the UK1

During 1988/1990, a series of 21 experiments was established in commercial crops of winter wheat. Chlorothalonil, fenpropimorph and propiconazole were chosen as protectant, eradicant or curative fungicides active against leaf diseases of winter wheat in the UK. To test their properties each one was applied once only to separate plots during a period of 7–8 consecutive weeks in May and June (GS 32–39). Disease progress was assessed weekly on adjacent unsprayed control and sprayed plots up to GS 85. Septoria tritici leaf blotch (Mycosphaerella graminicola) was the disease that occurred most frequently and severely across the 21 sites. Powdery mildew (Erysiphe graminis), brown rust (Puccinia recondita) and yellow rust (P. striiformis) occurred at fewer sites and were sufficiently severe to distinguish differences between the active ingredients at only two or three sites. Analysis of the disease progress curves for 75% control of each disease at one site only indicated that chlorothalonil possessed very good protectant but shorter‐term eradicant activity against M. graminicola and P. striiformis. Fenpropimorph exhibited only short‐term eradicant control of M. graminicola, but gave excellent protectant and eradicant control of E. graminis and P. striiformis; against P. recondita only eradicant activity was apparent. Propiconazole showed activity similar to that of fenpropimorph against P. recondita and excellent protectant and eradicant activity against M. graminicola and P. striiformis; against E. graminis, it gave good protectant and eradicant control. From disease progress curves, it was possible to calculate the period of protectant and eradicant activity in thermal time (accumulated degree days above zero) for each of the three active ingredients and to identify the most effective timing(s) for fungicide application in relation to rainfall or imputed infection.

Tests of fungicides for the control of leaf blotch diseases: Cladosporium allii of leek and C. allii-cepae of onion

Propiconazole, fenarimol, fenpropimorph, captafol, iprodione and triadimefon when added to malt extract agar inhibited spore germination (at 0.1–10 μg a.i. ml −1) of Cladosporium allii-cepae and C. allii. Propiconazole, triadimefon and fenarimol inhibited mycelial growth of both fungi at 100 μg a.i. ml −1 in agar. Propiconazole applied at 1 kg a.i. ha −1 in 11201 water to leeks in the field was the most effective fungicide against C. allii in eradicant and protectant activity and eliminated the fungus from established lesions. Propiconazole and fenarimol applied at similar rates gave significant eradicant activity against C. allii-cepae, but triadimefon, chlorothalonil and iprodione were not effective.

Protectant and After-Infection Activity of Fungicides Against Botryosphaeria obtusa on Apple

Reduction of radial growth of Botryosphaeria obtusa on fungicide-amended potato-dextrose agar medium was determined. EC 50 values (μg/ml) were as follows; benomyl, 0.032; bitertanol, 0.043; flusilazole, 0.045; mancozeb, 10.26; myclobutanil, 0.426; penconazole, 0.132; and tebuconazole, 0.036. Six of the fungicides were tested for their protectant and eradicant activity against B. obtusa. When apple (Malus domestica) seedlings were inoculated 7 days after fungicide application, mean disease severities (lesions per 100 cm 2 ) were as follows: benomyl, 4.6; bitertanol, 4.6; flusilazole, 20.7; mancozeb, 0.4; penconazole, 11.6; tebuconazole, 0.9; and control (no fungicide), 101.0 (...)

Influence of fruit temperature and application time on the effectiveness of fungicides in controlling citrus green mould, Penicillium digitatum

The effects of fruit temperatures (10, 15, 20 and 25�C) on eradicant activities of 5 different fungicides against Penicilliurn digitatum on Washington Navel were studied. With the fungicide guazatine, applied as a 30 s dip at a concentration of 500 µg/mL, a decrease in fruit temperature did not significantly reduce the time permitted between harvest and treatment if complete control was to be achieved. Benomyl at fruit temperatures of 15 and 10°C gave mould control until 30.5 ± 9.7 and 25.5 ± 7.9 h (mean ± s.e.) after inoculation respectively. At 10°C fruit could be left for 42.3 ± 6.5 h before treatment with etaconazole and mould control could still be achieved. The fungicide imazalil had the most eradicant activity, with mould control being achieved 30 ± 2.9, 28.4 ± 4.2, 44.6 ± 9.2 and 73.2 ± 4.3 h after inoculation at fruit temperatures of 25, 20, 15 and 10°C respectively. At no time was complete mould control achieved with prochloraz, which suggests that a concentration higher than 500 µg/mL should be recommended.

Glasshouse evaluation of fungicides for the control of sunflower downy mildew (Plasmopara halstedii)

SUMMARYA precise, reproducible and easy‐to‐handle glasshouse test is described for the evaluation of the systemic activity of chemicals for the control of Plasmopara halstedii, the downy mildew pathogen of sunflower. Four‐day‐old sunflower germlings were inoculated by immersing them in a zoosporangium suspension. Seedlings were then immersed in appropriate concentrations of the chemicals to be tested. Plants were grown in a glasshouse and assessed on three occasions to determine successively antisporulant, curative (systemic fungistatic), and eradicant effects.Sporulation in general was inhibited by lower concentrations than those required to exert an eradicant effect. There was a highly significant correlation between the ED50 values for visually recognised disease symptoms (stunting, dampingsff and leaf chlorosis) and for both curative and eradicant effects.Among 13 compounds tested, metalaxyl, RE 26745, furalaxyl, LAB 149202F and cymoxanil showed sufficient eradicant activity, to justify field evaluation for eradication of seed infections.

Studies on chlozolinate and PP192 for control ofBotrytis cinerea

Abstract The experimental fungicide PP192 showed high protectant activity against 18 isolates of Botrytis cinerea Pers.: Fr using beans as a test plant. Chlozolinate showed high protectant activity against dicarboximide-susceptible isolates but not against dicarboximide-resistant ones. This pattern of results was also found in fungicidal activity against hyphal growth in malt agar. On bean plants, PP192 showed protectant activity only, but chlozolinate and the other dicarboximide compounds also showed systemic, translaminar, and eradicant activity.

Treatments to control Phoma and Alternaria infections of brassica seeds

The screening of chemicals using agar plate tests for activity against cultures of Phoma lingam, Alternaria brassicicola and A. brassicae is described. Most fungicides which were inhibitory to growth at 20 μg/ml or less showed eradicant activity when used as seed treatments. Selected on this basis, thiabendazole, applied as a slurry at 2–5 g a.i./kg seed, showed excellent eradicant activity against seed‐borne Phoma but not Alternaria when tested under laboratory, glasshouse and field conditions. Triarimol, tridemorph and azepine‐A2151, nuarimol, fenarimol and imaza‐lil although effective in agar plate tests against Alternaria and Phoma were phytotoxic when applied to seeds at rates sufficient to eliminate these fungi, Iprodione and fenpropimorph inhi bited the growth of the fungi at concentrations of 0.625 to 4 μg/ml and subsequent treatment of infected seeds at 1.25–2.5 g a.i. fungicide/kg seed with these fungicides proved effective against all three pathogens. Neither chemical adversely affected germination or emergence.

Glasshouse tests of fungicides for apple powdery mildew control. II. Eradicant and anti-sporulant activity

SummarySmall apple plants with sporulating mildew colonies were sprayed with fungicide. The numbers of spores produced after treatment were taken as a measure of the eradicative and anti-sporulant activity of each fungicide. Eight of the materials tested greatly reduced sporulation in the nine days following treatment, but three had very little effect. Bupirimate, pyrazophos, binapacryl and ditalimfos were the most active fungicides tested. An overall rating for the activity of the fungicides against mildew is given.

EVALUATION OF FUNGICIDES FOR CONTROL OF ALBUGO CANDIDA IN TURNIP RAPE

Two applications of the protectant fungicides, Bravo, Manzate 200 and DPX 164 reduced foliar infection of turnip rape (Brassica campestris) by Albugo Candida. However, the fungicides had no apparent effect on staghead formation, the systemic phase of the disease. The acylalanine fungicides CGA 29212 and CGA 48988 showed excellent eradicant activity against foliar infection in growth room tests. In a field test, CGA 29212 significantly reduced the number of stagheads. CGA 38140 showed no activity against A. Candida on turnip rape.

Eradication of apple powdery mildew (Podosphaera leucotricha) with dormant season sprays of surface‐active agents

SUMMARYselection of surfactants (5%, w/v, a.i.) representative of the three main ionic types eradicated Podosphaera leucotricha from buds on dormant apple trees, cvs Cox's Orange Pippin, Jonathan and Michelin.The pathogen was apparently killed without undue damage to buds, although a phytotoxic response in the form of staining of vascular tissue and some crop reductions were observed. Treatments applied with hand lances were equally effective at reducing infections of vegetative buds on terminals, on non‐flowering spurs and flower buds. Indication of a positive correlation between the eradication of mildew from Cox's Orange Pippin trees and an increase in the incidence of apple canker (Nectria galligena) was found at Long Ashton, but this effect was negligible at sites in the West Midlands region.Efficacy of active formulations was reduced by rain soon after application or by a reduction in the concentration of applied material. Applications with a mist‐blower were effective on the cv. Cox's Orange Pippin, but less so on the cv. Jonathan, while on both cultivars efficacy of a spray containing 5 % a.i. decreased in the order 2240:1120:560 1/ha.Anti‐mildew activity was not associated with any particular chemical or ionic type of surfactant, and there was an indication that eradicant activity of alkyl phenol ethoxylates was related to their HLB value.The ecological and economic implications of the use of surfactants as fungicides are discussed.