Activity of carbendazim,dimethachlon, iprodione,procymidone and boscalid against Sclerotinia stem rot in Jiangsu Province of China

Carbendazim (MBC) was widely used to control Sclerotinia stem rot routinely during the 1980s in China, but development of MBC resistance in the causal agent Sclerotinia sclerotiorum led to control failures of this disease. In this study it was found that the MBC resistance in S. sclerotiorum populations was widespread throughout Jiangsu Province with a resistance frequency of 29.54% in the 1786 collected isolates during the growing seasons of 2006 to 2008. The resistance frequencies differed among sampled cities, ranging from 3.1% to 54.9%. The field MBC-resistant isolates showed comparable mycelial growth, sclerotia production and pathogenicity to the wild-type sensitive isolates, which suggested that the field MBC-resistant isolates might have sufficient parasitic fitness to compete with the field MBC-sensitive isolates in the field. In the in vitro sensitivity test, boscalid showed greater activity against S. sclerotiorum than dicarboximide fungicides (dimethachlon, iprodione and procymidone). The treatment 50% boscalid (WG) 125 g a.i. ha⁻¹ was comparable in efficacy to the treatment 50% iprodione (WP) 600 g a.i. ha⁻¹, and better than other treatments of 6% dimethachlon (WP) 690 g a.i. ha⁻¹ and 50% procymidone (WP) 337.5 g a.i. ha⁻¹, whereas MBC failed to control Sclerotinia stem rot (control efficacy only 16.0%). The most active agent for controlling Sclerotinia stem rot was boscalid in our study.     

In vitro inhibition of Sclerotinia sclerotiorum by mixtures of azoxystrobin, SHAM, and thiram

The necrotrophic fungal phytopathogen Sclerotinia sclerotiorum (Lib.) de Bary has a broad host range and frequently causes destructive diseases. The extensive use of common fungicides to control these diseases has selected for resistance in populations of S. sclerotiorum. In this study, 105 isolates of S. sclerotiorum from different geographical regions in Jiangsu Province of China were characterized for baseline sensitivity to azoxystrobin, and the average EC₅₀ value was 0.2932 μg/mL for mycelial growth. Of the mixtures of the fungicides thiram and azoxystrobin that were tested using an in vitro mycelial growth assay, the 1:4 ratio provided the greatest inhibition of S. sclerotiorum. When tested against nine isolates, the 1:4 mixture resulted in a mean synergy ratio of 2.31, indicating synergistic inhibition. Mycelial respiration was inhibited for about 2 h by azoxystrobin alone but for 48 h by the mixture of thiram and azoxystrobin. Salicylhydroxamic acid (SHAM, a known inhibitor of alternative respiration) also increased the inhibition of mycelial growth and respiration caused by azoxystrobin. These results suggest the need for further study of effects of combinations of azoxystrobin with thiram or SHAM in planta to evaluate their potential for management of diseases caused by S. sclerotiorum.     

Molecular and biochemical characterization of boscalid resistance in laboratory mutants of Sclerotinia sclerotiorum

The plant‐pathogenic fungus Sclerotinia sclerotiorum has a broad host range and a worldwide distribution. Boscalid, an inhibitor of succinate dehydrogenase in the electron transport chain of fungi, is highly effective in controlling sclerotinia stem rot caused by S. sclerotiorum. The current study characterized the S. sclerotiorum boscalid‐resistant (BR) mutants obtained by fungicide induction. Among the bioactive fungicides against S. sclerotiorum, cross‐resistance was not detected between boscalid and dimethachlon, fluazinam or carbendazim; positive cross‐resistance was detected between boscalid and carboxin; and negative cross‐resistance was detected between boscalid and kresoxim‐methyl. Compared to their parental isolates, BR mutants had slower radial growth, no ability to produce sclerotia, lower virulence and oxalic acid content but higher mycelial respiration and succinate dehydrogenase (SDH) activity. Moreover, BR mutants had decreased sensitivity to salicylhydroxamic acid (SHAM) but not to oxidative stress. All the results indicated that the risk of resistance to boscalid in S. sclerotiorum is low to moderate. DNA sequence analysis showed that all of the BR mutants had the same point mutation A11V (GCA to GTA) in the iron sulphur protein subunit (SDHB). Interestingly, expression of the cytochrome b (cytb) gene was reduced to different degrees in the BR mutants, and this might be correlated with the negative cross‐resistance between boscalid and kresoxim‐methyl. Such information is vital in the design of resistance management strategies.     

Fungicide resistance in Cercospora species causing cercospora leaf blight and purple seed stain of soybean in Argentina

Cercospora species cause cercospora leaf blight (CLB) and purple seed stain (PSS) on soybean. Because there are few resistant soybean varieties available, CLB/PSS management relies heavily upon fungicide applications. Sensitivity of 62 Argentinian Cercospora isolates to demethylation inhibitor (DMI), methyl benzimidazole carbamate (MBC), quinone outside inhibitor (QoI), succinate dehydrogenase inhibitor (SDHI) fungicides, and mancozeb was determined in this study. All isolates were sensitive to difenoconazole, epoxiconazole, prothioconazole, tebuconazole, and cyproconazole (EC₅₀ values ranged from 0.006 to 2.4 µg/ml). In contrast, 51% of the tested isolates were sensitive (EC₅₀ values ranged from 0.003 to 0.2 µg/ml), and 49% were highly resistant (EC₅₀ > 100 µg/ml) to carbendazim. Interestingly, all isolates were completely resistant to azoxystrobin, trifloxystrobin, and pyraclostrobin, and insensitive to boscalid, fluxapyroxad, and pydiflumetofen (EC₅₀ > 100 µg/ml). The G143A mutation was detected in 82% (53) of the QoI-resistant isolates and the E198A mutation in 97% (31) of the carbendazim-resistant isolates. No apparent resistance mutations were detected in the succinate dehydrogenase genes (subunits sdhB, sdhC, and sdhD). Mancozeb completely inhibited mycelial growth of the isolates evaluated at a concentration of 100 µg/ml. All Argentinian Cercospora isolates were sensitive to the DMI fungicides tested, but we report for the first time resistance to QoI and MBC fungicides. Mechanism(s) other than fungicide target-site modification may be responsible for resistance of Cercospora to QoI and MBC fungicides. Moreover, based on our results and on the recent introduction of SDHI fungicides on soybean in Argentina, Cercospora species causing CLB/PSS are insensitive (naturally resistant) to SDHI fungicides. Insensitivity must be confirmed under field conditions.     

Sensitivity of Rhizoctonia solani causing rice sheath blight to fluxapyroxad in China

Fluxapyroxad,3-(difluoromethyl)-1-methyl-N-(3’,4’,5’-trifluorobiphenyl-2-yl) pyrazole-4-carboxamide (C₁₈H₁₂F₅N₃O, Fig. 1), is a SDHI fungicide, which is a new active ingredient that interferes with succinate ubiquinone reductase in the electron transport chain of fungi. Between 2008 and 2010, a total of 128 isolates of Rhizoctonia solani from Anhui Province of China were characterized for the baseline sensitivity to fluxapyroxad. The isolates collected between 2008 and 2010 all showed similar sensitivity to fluxapyroxad. Baseline sensitivity was distributed as unimodal curves with an average EC₅₀ value of 0.054?±?0.014 μg ml^?1. However, EC₅₀ values of boscalid for inhibition of mycelial growth of R. solani isolates ranged from 1.89 to 2.68 μg/ml and the average (±SE) EC₅₀ value was 2.212?±?0.228 μg/ml, indicating that the R. solani isolates were less sensitive to boscalid than that of fluxapyroxad. Fluxapyroxad exhibited excellent protective and curative activity against rice sheath blight and provided 82.6–94.2 % protective or curative control efficacy. In field trials, control efficacy of fluxapyroxad at 100 g a.i/ha 15 days and 30 day after second application was 83.4–88.0 %, suggesting excellent activity against sheath blight. Control efficacy of boscalid at a dosage of 600 g a.i/ha 15 days and 30 day after second application was about 51.7–57.0 %. There was a significant difference in the efficacy between fluxapyroxad and boscalid or jinggangmycin. These results suggested that fluxapyroxad is a good alternative fungicide to jinggangmycin for the control of rice sheath blight.     

Detection and characterization of fungicide resistant phenotypes of Botrytis cinerea in lettuce crops in Greece

The development of resistance to chemical control agents needs continuous monitoring in Botrytis cinerea. 790 isolates from lettuce and other vegetable crops were collected from six widely separated sites in Greece and tested for their sensitivity to 11 fungicides from nine unrelated chemical groups. 44 of the isolates exhibited multiple resistance to fenhexamid (hydroxyanilides), azoxystrobin and pyraclostrobin (QoI’s), boscalid (SDHI’s), cyprodinil and pyrimethanil (anilinopyrimidines), fludioxonil (phenylpyrroles), carbendazim (benzimidazoles) and iprodione (dicarboximides). Thirty per cent of such phenotypes were detected in an experimental glasshouse with lettuce crops, the third year after commencing fungicide applications. The average resistance factor (R_f) for mycelial growth to fenhexamid, pyraclostrobin, boscalid, cyprodinil and fludioxonil, was over 40, 1,000, 100, 700 and 50, respectively. Some strains with high resistance to anilinopyrimidines (14 %) or moderate to fludioxonil (7 %) were detected even in isolates collected from vegetable crops prior to commercial use of these fungicides in Greece. Isolates with fludioxonil moderate resistance and fenhexamid high resistance, were detected for the first time in Greece. The results suggested the high risk in chemical control of grey mould due to development of resistance to most fungicides with site-specific modes of action. Isolates with resistance to fluazinam (phenylpyridinamines) and to chlorothalonil (phthalonitriles) were not found. The inclusion of appropriate multi-site inhibitors like chlorothalonil in fungicide anti-resistance strategies was indispensable.     

Chemical and biological control of Sclerotinia sclerotiorum in witloof chicory culture

BACKGROUND: Sclerotinia sclerotiorum (Lib.) de Bary is a major pathogen of witloof chicory. For lack of authorised field treatment, post‐harvest sprays with dicarboximide fungicides have been standard practice since the 1970s to prevent root rot and chicory heart decay during the forcing phase. However, the registration of procymidone and vinclozolin has been withdrawn in Europe. The development of organic agriculture and the necessity to reduce fungicide applications in conventional agriculture prompted an assessment of the efficacy of new fungicides and the use of the mycoparasite Coniothyrium minitans (Campbell). RESULTS: A mixture of the fungicides fludioxonil and cyprodinil (Switch^®) applied on chicory roots achieved a very good control of S. sclerotiorum (up to 95%). The use of C. minitans limited root infection, both when applied in the field (50–65% efficacy) and before the forcing period (post‐harvest treatment up to 80%). CONCLUSION: In organic agriculture, two treatments with C. minitans (in field and later at the forcing period) could improve protection against S. sclerotiorum. In conventional agriculture, after the field biological treatment, a post‐harvest chemical treatment could be applied. The addition of other prophylactic methods could lead to a high level of performance in practice against decay caused by S. sclerotiorum. Copyright © 2010 Society of Chemical Industry     

Combining sanitation and disease modelling for control of grapevine powdery mildew

Chasmothecia of Erysiphe necator form in one season, survive winter and discharge ascospores that cause primary infections and trigger powdery mildew epidemics in the next season. A strategy for powdery mildew control was developed based on (i) the reduction in overwintering chasmothecia and on (ii) spring fungicide applications to control ascosporic infections timed based on estimate risk (two to five sprays per season). Several fungicides, the hyperparasite Ampelomyces quisqualis, and a mineral oil product were first tested as separate applications in a greenhouse and in vineyards. In the greenhouse, A. quisqualis suppressed chasmothecia formation by 41 %; fungicides and mineral oil suppressed chasmothecia formation by 63 % and ascospore viability by 71 %. In vineyards, application of boscalid + kresoxim-methyl or meptyldinocap once after harvest, as well as application of A. quisqualis pre- and post-harvest, delayed disease onset and epidemic development in the following season by 1 to 3 weeks and lowered disease severity (up to the pea-sized berry stage) by 56 to 63 %. Risk-based applications of sulphur and of synthetic fungicides provided the same control as the grower spray program but required fewer applications (average reduction of 47 %). Sanitation strategies were then tested by combining products and application times (late-season, and/or pre-bud break, and/or spring). Adequate disease control with a reduced number of sprays was achieved with the following combination: two applications of A. quisqualis (pre- and post-harvest), one application of mineral oil before bud break, and model-based applications of sulphur fungicides between bud break and fruit set.     

Efficacy of phosphonate in controlling white powdery rot of fig caused by <Emphasis Type="Italic">Phytophthora palmivora</Emphasis>

Pre- and post-infection activities of phosphonate and fungicides (azoxystrobin, chlorothalonil, cyazofamid, copper hydroxide, and copper sulfate) against white powdery rot on fig leaves caused by Phytophthora palmivora were determined. Phosphonate and fungicides were applied at 3, 7, or 14 days before inoculation and 16, 24, or 40 h after inoculation. Phosphonate and four fungicides (except for chlorothalonil) had protectant activity for up to 14 days before inoculation. Protectant activity between phosphonate and the four fungicides did not differ significantly. These fungicides did not have a curative activity, whereas only phosphonate had a curative activity when applied 16 h after inoculation. The pre-infection activity of phosphonate was determined in fig fields. Phosphonate provided excellent protectant activity, and its activity did not differ significantly from that of the copper fungicides. The activity of phosphonate in the life cycle of P. palmivora was compared with that of the five fungicides. Half-maximal effective concentration of the inhibition of mycelial growth was low for phosphonate, chlorothalonil, and the two copper fungicides. Mycelial growth was least affected by azoxystrobin and cyazofamid, but n-propyl gallate, an alternative oxidase inhibitor, in combination with these fungicides, significantly inhibited mycelial growth. Sporangium formation was sensitive to all compounds. Germination of encysted zoospores was sensitive to azoxystrobin, cyazofamid, and chlorothalonil and least sensitive to phosphonate and the two copper fungicides. The activity of phosphonate on mycelial growth and sporulation of P. palmivora suggests it has potential for controlling the disease.     

Evaluation of Inhibitory Effect of Some Bicarbonate Salts and Fungicides Against Hazelnut Powdery Mildew

Hazelnut (Corylus avellana L.) which is intensively grown in the Black Sea region is the most important agricultural product of Turkey. Hazelnut production and quality are negatively affected by several diseases and pests. Powdery mildew is nowadays one of the most common diseases in almost whole hazelnut producing areas. The disease is caused by two different species, Phyllactinia guttata (Wallr. et Lev.) Fr. and Erysiphe corylacearum U. Braun & S. Takam. For the last 4 years, E. corylacearum, a newly invasive fungus in Turkey, has been caused significant economic losses. In the present study, the efficacy of ammonium, potassium and sodium bicarbonates, and two fungicides were evaluated in field trials against powdery mildew on hazelnuts in Samsun in 2016. The application rates of compounds used in the experiment were as follows: ammonium, potassium and sodium bicarbonates (Sigma-Aldrich, Seelze, Germany) at 1.5, 3, 4.5 and 6% (w/v); Collis® SC (100?g/l Kresoxim methyl +200?g/l Boscalid, BASF, Spain) at 30?ml/100?l and Sulflow® 80 WG (Sulphur 800?g/l, Agrofarm, Turkey) at 400?g/100?l. Of the compounds tested, except for fungicides, sodium was found to be the most effective in controlling the powdery mildew on hazelnuts, followed by potassium and ammonium, respectively. Among those three, ammonium bicarbonate was ineffective against fruit infections of the disease. There was also no significant difference between inhibitory effects of 6% sodium bicarbonate, Collis and Sulflow against the disease (P < 0.05). In addition, bicarbonate salts was phytotoxic to hazelnut leaves at concentrations greater than 1.5%. The results indicate that sodium or potassium bicarbonate solutions seems to be a useful biocompatible fungicide for controlling the powdery mildew on hazelnuts.     

Azoxystrobin and propiconazole offer significant potential for rice blast (<Emphasis Type="Italic">Pyricularia oryzae</Emphasis>) management in Australia

Fungicides are the preferred rice blast (Pyricularia oryzae) control option by farmers. However, no fungicides are yet registered for this purpose in Australia. Hence, it is important to test the baseline sensitivity of P. oryzae isolates collected from blast-affected regions across northern Australia, which have not yet been exposed to the fungicides, as part of a resistance management strategy. Further, it is also important to investigate and compare effect of application timing of fungicides on conidial development, including germination and germ tube growth, and penetration on susceptible rice. The EC₅₀ of a collection of fungicide-sensitive blast isolates were within the range of 0.02–2.02 and 0.06–1.91 mg L^?1 for azoxystrobin and propiconazole, respectively. Azoxystrobin was shown to have greater inhibitory effect on conidial germination than propiconazole. In addition, for pre-inoculation application, only germ tubes in the presence of external nutrients continued to grow from 24 to 48 hpi. On susceptible seedlings, both fungicides completely controlled blast disease when applied the same day as inoculation. However, for pre- or post-inoculation application of fungicide, the extent of disease control was reduced, with azoxystrobin more efficacious than propiconazole. A stimulatory effect of both fungicides at low dose was observed on certain P. oryzae isolates. This is the first study to assess the baseline sensitivity of the P. oryzae population in Australia and the first to report a stimulatory effect of low azoxystrobin concentration on growth of P. oryzae. The study highlights, for the first time, the critical role of external nutrients in promoting germ tube growth under fungicide stress conditions. Lastly, it demonstrates the high degree of efficacy of the fungicides and their potential for future rice blast management in Australia.     

烟草米根霉对6种杀菌剂的敏感性及菌株保存条件筛选

采用孢子萌发法测定了烟草上米根霉Rhizopus oryzae对6种杀菌剂 (代森锰锌、多菌灵、嘧霉胺、嘧菌酯、啶酰菌胺及氟啶胺) 的敏感性,并就其适宜的保存条件进行了筛选,同时采用离体叶片法测定了上述6种杀菌剂对烟叶霉烂病的防治效果。结果表明:6种杀菌剂对米根霉孢子萌发和烟叶霉烂病均表现出了不同的抑制活性。其中,抑制孢子萌发活性最为明显的是氟啶胺和啶酰菌胺,其EC₉₀值分别为0.67 和1.53 mg/L;其次为代森锰锌和嘧菌酯,15.16和17.66 mg/L;最弱为嘧霉胺和多菌灵,71.87和81.96 mg/L。对烟叶霉烂病防效最好的为嘧菌酯,50 mg/L处理的防效为85%;其次为啶酰菌胺,200 mg/L处理时防效为83%;氟啶胺的防效较差,1 000 mg/L处理时仅为48%;而代森锰锌、多菌灵和嘧霉胺在最高使用剂量 (分别为4 000、800和800 mg/L) 时防效均低于20%。病原菌保存方法筛选结果表明,保存后米根霉的孢子萌发率均发生了不同程度降低。其中,4 ℃保存于20%甘油组的孢子悬浮液萌发率为60%;4 ℃保存的孢子干样萌发率为36%;4 ℃保存的孢子悬浮液和 –20 ℃保存于20%甘油的孢子悬浮液萌发率均低于20%;20 ℃保存的孢子干样萌发率为11%;–20 ℃保存的孢子悬浮液萌发率为6%。研究结果可为烘烤期烟叶霉烂病防治和米根霉孢子的保存提供参考依据。     

The control of sclerotinia stem rot on oilseed rape (Brassica napus): current practices and future opportunities

Sclerotinia stem rot (SSR) caused by the phytopathogenic fungus Sclerotinia sclerotiorum is a major disease of oilseed rape (Brassica napus). During infection, large, white/grey lesions form on the stems of the host plant, perturbing seed development and decreasing yield. Due to its ability to produce long‐term storage structures called sclerotia, S. sclerotiorum inoculum can persist for long periods in the soil. Current SSR control relies heavily on cultural practices and fungicide treatments. Cultural control practices aim to reduce the number of sclerotia in the soil or create conditions that are unfavourable for disease development. These methods of control are under increased pressure in some regions, as rotations tighten and inoculum levels increase. Despite their ability to efficiently kill S. sclerotiorum, preventative fungicides remain an expensive gamble for SSR control, as their effectiveness is highly dependent on the ability to predict the establishment of microscopic infections in the crop. Failure to correctly time fungicide applications can result in a substantial cost to the grower. This review describes the scientific literature pertaining to current SSR control practices. Furthermore, it details recent advances in alternative SSR control methods including the generation of resistant varieties through genetic modification and traditional breeding, and biocontrol. The review concludes with a future directive for SSR control on oilseed rape.     

Characterization of the host range and sensitivity to fungicides of Trichothecium spp. associated with fruit rot in the field and in storage

During 2017–2019, we observed Trichothecium spp. causing fruit rot in the field and in storage. This study was conducted to examine morphological differences of the species from different hosts, reveal the species’ potential host range, and evaluate the efficacy of five fungicides. Six strains of Trichothecium spp. isolated from nectarine, peach and walnut were selected. Although the colony morphology, mycelial growth rate and spore size differed among hosts, phylogenetic analysis based on the internal transcribed spacer and part of the 5ʹ end of the β-tubulin gene showed that all tested strains belonged to Trichothecium roseum. For its host range, 23 kinds of fruit were examined using T. roseum strain YT-1 as an inoculum; 10 kinds of fruit, including pear, apple, mango, Chinese chestnut, pepino melon, fig and durian, were susceptible to T. roseum, with minimum inoculation concentrations ranging from 10⁴ to 10⁵ spores/ml. The fungicides that most effectively inhibited the six isolates were fluazinam and fludioxonil, with EC₅₀ values of 0.07–0.1 and 0.01–0.04 μg/ml, respectively, followed by difenoconazole (0.81–2.96 μg/ml), boscalid (5.43–13.51 μg/ml) and azoxystrobin (9.18–27.25 μg/ml). Improvement of the shelf life of nectarines held in plastic trays was explored using allyl isothiocyanate (AITC) against T. roseum YT-1. The application of 10 μl/L AITC significantly suppressed disease symptoms. The findings provide useful information for future disease emergency management in the field and for food preservation.     

In vitro and field efficacy of three fungicides against <Emphasis Type="Italic">Fusarium</Emphasis> bulb rot of garlic

Fusarium proliferatum has been identified as the main causal agent of bulb rot of garlic (Allium sativum L.). This disease occurs after the drying process and can rot almost 30 % of the bulbs. Few studies are available regarding the effectiveness of chemical treatments to reduce F. proliferatum incidence in garlic. The efficacy of three commercial fungicides of different chemical groups to reduce seven strains of F. proliferatum mycelial growth was tested in vitro. These three fungicides were also evaluated by foliar spreading of aqueous suspension in a field crop. Fluopyram 20 % + tebuconazole 20 % and tebuconazole 50 % + trifloxystrobin 50 % were highly effective at reducing mycelial growth in F. proliferatum with EC₅₀ values <2 ppm. In general, the effectiveness of the fungicides was enhanced with increasing dosage. Our results indicate that the fungicides evaluated in this study may lead to a risk of resistance appearing in F. proliferatum at low concentrations and this risk is maintained at higher doses for the fungicide dimethomorph 7.2 % + pyraclostrobin 4 %. Although several of the fungicides affected in vitro mycelial growth of F. proliferatum, as a part of an strategy to measure the efficacy of resistance management it is necessary to monitor the ongoing efficacy of fungicides under commercial conditions. All fungicidal treatments tested in field application failed to control garlic bulb rot during storage.     

Using crop canopy modification to manage plant diseases

Modifying crop canopies can suppress plant diseases in some crops. For example, in carrot, lateral trimming of the canopy by 30–40 % after canopy closure reduced sclerotinia rot (Sclerotinia sclerotiorum) to zero under moderate disease pressure without the use of fungicides. Trimming reduced relative humidity within the carrot canopy and increased air and soil temperature, inhibiting the formation of apothecia of S. sclerotiorum. Trimming also severed infected petioles, which reduced the opportunity for infection to progress to the carrot crown. Trimming combined with application of foliar fungicide was even more effective. Trimming reduced carrot leaf blights (Alternaria dauci, Cercospora carotae) in 1 of 3 years, when disease pressure was low. However, there was no advantage of combining trimming and fungicide sprays for leaf blight control. Canopy modification also reduces disease in legume crops. Soybean cultivars with reduced height and lodging, and early maturity, had up to a 74 % reduction in apothecia of S. sclerotiorum within the crop, and up to an 88 % reduction in disease incidence at harvest. In field pea, artificially supporting plants to reduce lodging, in combination with fungicide application, reduced the severity of mycosphaerella blight (Mycosphaerella pinodes) on pods by 67 % and increased seed yield by 54 %. In chickpea, paired-row planting that opened the canopy increased seed yield by 12 %, likely by increasing fungicide deposition. Modifications of the crop canopy can reduce disease, the need for fungicide sprays, and sometimes improve fungicide efficacy, but the results are often pathosystem-specific.     

<Emphasis Type="Italic">Ulocladium atrum</Emphasis> as a biological control agent for white mold of bean caused by<Emphasis Type="Italic">Sclerotinia sclerotiorum</Emphasis>

Field studies were conducted near Lethbridge, Alberta, Canada, in 2001, 2004 and 2005 to determine the efficacy of the antagonistic fungusUlocladium atrum for control of white mold of bean caused bySclerotinia sclerotiorum. Results of the 3 years of field trials showed that, compared with the untreated control, foliar application of a spore suspension ofU. atrum (300 ml m⁻² of 10⁶ spores ml⁻¹ suspension) significantly reduced incidence and severity of white mold, increased seed yield and reduced contamination of bean seed by sclerotia ofS. sclerotiorum. The level of control of white mold observed in the treatment ofU. atrum was similar to that of the mycoparasitic fungusConiothyrium minitans, but lower than the fungicide treatments of Ronilan (vinclozolin) at the rate of 1200 g ha⁻¹ per application in 2001, or Lance (boscalid) at the rate of 750 g ha⁻¹ per application in 2004 and 2005. The potential for use ofU. atrum as a biological control agent for sclerotinia diseases is discussed. http://www.phytoparasitica.org posting Nov. 12, 2006.     

申嗪霉素对油菜菌核病菌生物学活性的初步研究

申嗪霉素是一种新型微生物源杀菌剂,主要成分为吩嗪-1-羧酸。测定了申嗪霉素对油菜菌核病菌菌丝生长的抑制作用。结果表明,申嗪霉素对油菜菌核病菌51个菌株菌丝生长的平均有效抑制中浓度(EC50值)为3.31±0.77 μ g/mL,并且与常规杀菌剂多菌灵、菌核净无交互抗性关系。离体叶片和田间药效试验表明,申嗪霉素对油菜菌核病的防治效果随其处理剂量增加而提高,用有效成分200 μ g/mL药液处理时,抑制离体叶片发病的效果可达到67.08%,田间防效可达83.29％,优于对照药剂异菌脲。     

Control of seed-borne Sclerotinia sclerotiorum by fungicidal treatment of sunflower seed

Treatment of sunflower seeds with benomyl, vinclozolin, iprodione or procymidone virtually eliminated seed-borne Sclerotinia sclerotiorum. Applications of fungicides increased the number of surviving seedlings when seeds were sown in vermiculite or in steam-sterilized soil. With the exception of benomyl, fungicides were significantly more effective when applied in acetone solutions than when 100 g a.i./100 kg of seed was applied as conventional dry dressings. There was no difference in effectiveness between the two application methods when the dry dressings were applied at 200 g a.i/100 kg of seed. The acetone infusion method had no deleterious effects on germination of disease-free seed nor on seedling vigour. For a comparable level of control, less fungicide was needed in the infusion treatment than in the dust treatment. If fungicidal treatment of sunflower seeds is used routinely then the introduction of S. sclerotiorum into uninfested land could be controlled.     

河北省黄瓜霜霉病菌对甲霜灵和嘧菌酯的抗性动态及七种药剂的田间防效

为明确黄瓜霜霉病菌对甲霜灵和嘧菌酯的抗性动态及相应药剂对黄瓜霜霉病的田间防效,采用叶盘漂浮法监测了2011—2015年河北省黄瓜霜霉病菌对甲霜灵和嘧菌酯的抗性,采用茎叶喷雾法测定了含甲霜灵或精甲霜灵的混剂及嘧菌酯单剂等7种药剂的田间防效。结果表明:采自河北省不同地区的838株黄瓜霜霉病菌对甲霜灵和嘧菌酯普遍产生抗性,抗性频率为100.00%,抗性倍数为482.99和354.97,黄瓜霜霉病菌对甲霜灵和嘧菌酯的抗性随着监测地区和监测年限而波动,唐山、沧州、石家庄、衡水、廊坊和保定市的菌株对甲霜灵和嘧菌酯的抗性指数高于其它地区,黄瓜霜霉病菌对甲霜灵和嘧菌酯的抗性指数在不同年度间高位波动。按照田间推荐剂量喷施,250 g/L嘧菌酯悬浮剂对黄瓜霜霉病的防效为72.15%~74.13%;68%精甲霜灵·代森锰锌水分散粒剂和58%甲霜灵·代森锰锌可湿性粉剂的防效分别为65.30%~70.19%和63.26%~68.35%,与80%代森锰锌可湿性粉剂防效相当;50%烯酰吗啉可湿性粉剂、250 g/L双炔酰菌胺悬浮剂和687.5 g/L氟吡菌胺·霜霉威盐酸盐悬浮剂的防效达82.00%以上,对黄瓜霜霉病具有较好的防效,在黄瓜霜霉病菌对嘧菌酯、甲霜灵和精甲霜灵产生抗性的地区,可作为替代或混配药剂使用。