Reduced sensitivity of tomato early blight pathogen (Alternaria solani) isolates to protectant fungicides,and implication on disease control

The sensitivity of Alternaria solani isolates to the fungicides mancozeb and chlorothalonil was evaluated, to determine if inadequate disease management by these fungicides could be attributed to reduced sensitivity of A. solani isolates to these fungicides. The sensitivity of 60 isolates of A. solani was assessed using the inhibition of radial mycelial growth (RG) method, using fungicide concentrations of 0, 1.0, 10, 100, 500 and 1000 μg a.i ml^?1 medium. EC₅₀ was calculated for each isolate and fungicide combination. The EC₅₀ values of different A. solani isolates to mancozeb ranged from 9.05 to 712.65 μg ml^?1. EC₅₀ values of different isolates to chlorothalonil ranged from 4.25 to 849.4 μg ml^?1. The percentage of isolates with reduced sensitivity was 46.7 and 53.3% for mancozeb and chlorothalonil, respectively. Results of the in vivo tests demonstrated decline in disease control by the two fungicides with the reduced-sensitivity isolates compared to the sensitive ones.     

Baseline sensitivities to azoxystrobin and tebuconazole in Sclerotinia sclerotiorum isolates from sunflower in Iran related to sensitivities to carbendazim and iprodione

In this study, sensitivities of 156 Sclerotinia sclerotiorum isolates collected from sunflower fields of West Azarbaijan province, Iran, were assessed to carbendazim and iprodione, and the baseline sensitivities were established for azoxystrobin and tebuconazole. Resistance to carbendazim and iprodione was observed in 53.85% and 4.49% of the isolates, respectively. The 50% effective concentration (EC₅₀) values of azoxystrobin for the isolates ranged from 0.017 to 3.515 μg/ml with a mean of 0.330 μg/ml, and 8.97% of the strains showed low levels of resistance to the fungicide. However, in the presence of salicylhydroxamic acid, all isolates were sensitive to azoxystrobin and EC₅₀ values ranged from 0.015 to 0.263 μg/ml with a mean of 0.086 μg/ml. All isolates were found to be sensitive to tebuconazole, and EC₅₀ values ranged from 0.003 to 0.177 μg/ml with a mean of 0.036 μg/ml. Among the multiple-resistant isolates, the strains exhibiting resistance to both carbendazim and iprodione were detected in the highest frequency (4.49%). No correlation was observed between mycelial growth and aggressiveness with fungicide sensitivity of the isolates suggesting the absence of fitness cost associated with resistance to the studied fungicides. The results indicated that iprodione, azoxystrobin and tebuconazole could be effectively used in rotation or mixture in spray programmes to manage S. sclerotiorum in the region. The baselines established for azoxystrobin and tebuconazole would be useful in monitoring the fungal populations in the province to assess possible shifts in fungicide sensitivity of S. sclerotiorum isolates in the future.     

The incidence of benomyl tolerance in Verticillium fungicola, Mycogone perniciosa and Hypomyces rosellus in mushroom crops

Of the 229 isolates of Verticillium fungicola examined 63 % were found to show some benomyl tolerance and 53% were very tolerant having EDg, values in excess of 50 ppm. There was a tendency for the tolerant isolates to have a slower growth rate than the sensitive ones on unamended potato dextrose agar (PDA) and forty-five isolates (19 %) showed growth stimulation at 5 ppm benomyl. No major differences were found in ten isolates of V. fungicola tested on benomyl, thiabendazole and thiophanate methyl agars or of twelve isolates compared on benomyl and carbendazim hydrochloride agars. Tolerant isolates of V. fungicola and higher levels of crop loss were linked in the east and north of the country but not in the south-east. Tolerance was not found in sixty-six isolates of Mycogone perniciosa or twenty-four of Hypomyces rosellus. Benomyl was used on 89 % of the farms in the survey either applied to the casing (34%) or as a spray (55 %) or both (10%).     

Effect of five fungicides with different modes of action on cobweb disease (Cladobotryum mycophilum) and mushroom yield

The fungicides chlorothalonil, metrafenone, prochloraz‐Mn, thiabendazole and thiophanate‐methyl were tested in vitro and in vivo for their effect on Cladobotryum mycophilum, the mycoparasite that causes cobweb disease in white button mushroom. In vitro experiments showed that metrafenone (EC₅₀= 0.025 mg L^?1) and prochloraz‐Mn (EC₅₀= 0.045 mg L^?1) were the most effective fungicides for inhibiting the mycelial growth of C. mycophilum. Selectivity indexes of the tested fungicides on both C. mycophilum and Agaricus bisporus indicated that metrafenone was also the most selective fungicide, while chlorothalonil was the most toxic fungicide against A. bisporus mycelium. The in vivo efficacy of fungicides for controlling cobweb was evaluated in three mushroom cropping trials, which were artificially inoculated with C. mycophilum (10⁶ conidia m^?2). Prochloraz‐Mn provided good control, although the surface colonised by cobweb reached 12% by the end of the crop cycles. None of the inoculated cropping trials treated with metrafenone showed any cobweb disease symptoms, and neither were any significant phytotoxic effects on mushroom yield recorded. These results indicated that metrafenone can be used as an alternative to prochloraz‐Mn in the control of cobweb disease.     

Sensitivity to boscalid in field isolates of Sclerotinia sclerotiorum from rapeseed in Henan Province,China

Sclerotinia stem rot caused by Sclerotinia sclerotiorum is an important disease of oilseed rape in Henan province of China. Boscalid belongs to succinate dehydrogenase inhibitor (SDHI) fungicides, many of which have strong antifungal activity against S. sclerotiorum. In 2015, a total of 175 isolates of S. sclerotiorum were collected from diseased oilseed rape plants in seven different regions of Henan Province. The EC₅₀ values of 175 isolates of S. sclerotiorum to boscalid ranged from 0.0073 to 0.3880 μg ml^?1, and the mean EC₅₀ value was 0.15 ± 0.09 μg ml^?1. The frequency distribution was unimodal. There was no cross‐resistance between boscalid and carbendazim, procymidone, iprodione, dimethachlone, fludioxonil or fluazinam. Field experiments showed that control efficacies of treatments with boscalid (50% WG) at 225, 300 and 375 g ai ha^?1 were 71%, 81% and 90%, respectively. In contrast, the control efficacy of carbendazim (50% WP) at 1,500 g ai ha^?1 was only 52%.     

Fungicide resistance of Botrytis cinerea in tomato greenhouses in the Canary Islands and effectiveness of non-chemical treatments against gray mold

Tomato greenhouses in the Canary Islands, Spain, were surveyed to estimate frequencies of resistance to benzimidazoles, dicarboximides, anilinopyrimidines and N-phenylcarbamates in Botrytis cinerea. Resistance to carbendazim, iprodione, pyrimethanil and diethofencarb was found in 74.2, 86.4, 28.8 and 31.8 % of isolates, respectively. Benzimidazole- and anilinopyrimide-resistant isolates were highly resistant, showing EC₅₀ values above 500 µg/ml carbendazim and a mean EC₅₀ value of 28.42 µg/ml pyrimethanil, respectively. By contrast, a low level of resistance was observed among dicarboximide-resistant isolates (mean EC₅₀ value of 1.81 µg/ml iprodione). Phenotypes with double resistance to carbendazim and iprodione, and triple resistance to carbendazim, iprodione and pyrimethanil were the most common, occurring in 36.4 and 28.8 % of isolates. The surveyed greenhouses had never been treated with fenhexamid and Signum? (pre-packed mixture of boscalid and pyraclostrobin), and baseline sensitivities of B. cinerea isolates to these fungicides were determined. The EC₅₀ values were within the range of 0.009–0.795 µg/ml fenhexamid and of 0.014–0.48 µg/ml Signum. In addition, available formulations based on elicitors of plant defense response and biocontrol agents were evaluated against B. cinerea in tomato plants under semi-controlled greenhouse conditions, the yeast Candida sake CPA-1 being able to reduce gray mold significantly when it was applied on petiole wounds and the plants were inoculated 24 h later. Likewise, C. sake was effective against B. cinerea in harvested tomato fruits, yeast-treated tomatoes showed a 70.66 and 30.31 % reduction in the diameters of decay lesions compared with controls after 10 days of storage at 20 and 9 °C, respectively.     

Comparison of fungicides for the control of Rhizoctonia solani causing datnping-off of mung bean (Phaseohis aureus)

Of 41 fungicides tested in the laboratory, copper carbonate, copper sulphate, mercuric chloride, Agrosan GN, quintozene, kasugamycin, carboxin, pyracar-bolid, carbendazim, chloroneb, benomyl, Ohric, RH 893 (2-n-octyl-4-isothiazole-3-one) and Terrazole were most inhibitory to the mycelial growth of Rhizoctonia solani on Czapek's agar plates and had EC₅₀ values of less than 1 μg a.i./ml, while copper oxychloride, Udonkor, zineb, ziram, F 319 (3-hydroxy-5-methyl isoxazole) and anilazine were much less toxic, ziram being least inhibitory with an EC₅₀ of 214 μg a.i./ml. Of 17 fungicides tested in the greenhouse as seed treatments, thiabendazole, carbendazim, benomyl, thiophanate-methyl, dichlozoline and Ohric gave 80–90% control of damping-off of mung bean seedlings. A single soil drench with thiophanate-methyl and two drenches with benomyl gave about 90% disease control, More seedlings with R. solani infection survived when thiophanate-methyl was used as a post-inoculation soil drench than when benomyl or chloroneb were used.     

Control of Botrytis cinerea on glasshouse tomato by high volume sprays

The new fungicides iprodione, vinclozolin and prochloraz, and also a mixture containing carbendazim and maneb, were compared with the established protectant fungicides dichlofluanid and chlorothalonil for effectiveness against grey mould ( Botrytis cinerea ) in an unheated tomato crop. Iprodione and vinclozolin gave the best control of lesions on leaves and stems but dichlofluanid was the most effective in controlling ghost-spotting of fruit. The carbendazim/maneb mixture was effective against a carbendazim-sensitive isolate but not against an insensitive isolate of B. cinerea . When applied 1 or 2 days after inoculation, all five protectant fungicides controlled the insensitive isolate better than the sensitive isolate.     

In vitro studies on the effects of fungicides on beneficial fungi of peach twig mycoflora

In vitro studies were carried out to investigate a possible integrated use of chemical and biological means to control the peach twig blight pathogen,Monilinia laxa. Three fungal antagonists ofM. laxa (Penicillium purpurogenum, Penicillium frequentans andEpicoccum nigrum) and six fungicides (vinclozolin, iprodione, thiram, captan, benomyl and thiophanate-methyl) were used in the study. Sensitivity of the fungal isolates to the fungicides was determined in vitro by calculating ED50 values. Benomyl and thiophanate-methyl were the most fungitoxic compounds and captan was the least fungitoxic.M. laxa andP. purpurogenum were the most sensitive to all chemicals tested, whileE. nigrum andP. frequentans presented bigger differences in their sensitivity to chemicals compared toM. laxa. E. nigrum was consistently less sensitive to benomyl (ED50=2.26 ppm), thiophanate-methyl (ED50=9.61 ppm) and vinclozolin (ED50=3.89 ppm) than the other fungi.P. frequentans was less sensitive to captan, vinclozolin, iprodione, thiophanate-methyl and thiram thanM. laxa (8, 7, 5, 4 and 2 times respectively). These results suggest thatE. nigrum andP. frequentans could be successfully used in an integrated control programme that combines biological and chemical methods.     

The disappearance of benomyl from mushroom casing

The failure of Benlate (50% benomyl) to control Mycogone perniciosa on mushroom farms where isolates of the organism were benomyl sensitive was investigated. A comparison was made of carbendazim levels, the major fungitoxic breakdown product of benomyl, in unsterilised casing, autoclaved casing and autoclaved casing mixed with a small proportion (1.7%) of casing previously treated with benomyl but from which all detectable levels of carbendazim had disappeared. Added benomyl was effective in controlling M. perniciosa in autoclaved casing, less effective in unamended casing and ineffective in the amended casing mixture. The recovery of carbendazim from these treatments was directly related to disease occurrence. Studies on farms where benomyl or other carbendazim generating fungicides had been used indicated that a lack of control of M. perniciosa was associated with the disappearance of fungicide from the casing before cropping began. This was not so on a farm where carbendazim generating fungicides had not been used before these investigations. Thiabendazole, a fungicide closely related to the carbendazim generators showed only a slight decline in concentration in casing capable of degrading benomyl. Bacteria isolated from the casing were examined in vitro for their ability to degrade benomyl. Five groups of bacteria were compared and three bacteria, Pseudomonas putida, Pseudomonas aeruginosa and an unidentified member of the Entero-bacteriaceae were most able to degrade benomyl.     

Occurrence of fenhexamid resistance in Botrytis cinerea from greenhouse strawberries in China

This study assessed the fenhexamid sensitivity of 143 Botrytis cinerea isolates collected from greenhouse strawberries in five regions of China between 2012 and 2013, and identified four isolates with moderate levels of resistance: two from the Xinjiang Uygur Autonomous Region and two from Hebei Province. The baseline fenhexamid sensitivity of B. cinerea exhibited a unimodal distribution with a mean EC₅₀ value of 0.20 ± 0.10 μg/ml (SD). The EC₅₀ values of the fenhexamid‐resistant isolates ranged from 0.05 to 0.40 μg/ml. Molecular analysis of the fenhexamid target gene erg27 revealed that the resistant isolates collected from Xinjiang (163‐6 and 163‐22) contained three mutations that led to amino acid changes (V365A, E368D and A378T) known to be associated with fenhexamid resistance, but that the isolates from Hebei lacked any mutations, indicating that an alternative mechanism could be responsible for their resistance. Most of the biological characteristics of the fenhexamid‐resistant isolates, such as mycelial growth, sclerotia production and pathogenicity, did not significantly differ from those of the sensitive ones (p ≤ .05), but it was noted that some of the resistant isolates exhibited reduced rates of sporulation and spore germination. In addition, the resistant isolates exhibited lower osmotic sensitivity than the sensitive ones. The study found no evidence of cross‐resistance with other fungicides, but that there was negative cross‐resistance with procymidone, iprodione, carbendazim and pyraclostrobin, which indicates that the inclusion of these fungicides within an integrated pest management (IPM) programme could help to minimize the risk of fenhexamid resistance developing in B. cinerea.     

Contribution of Pathogens to Peach Fruit Rot in Northern Greece and their Sensitivity to Iprodione, Carbendazim, Thiophanate-methyl and Tebuconazole Fungicides

This study identified the main pathogens causing fruit rots of mature peaches in northern Greece, the major peach producing area of Greece. The brown rot pathogen Monilinia laxa was responsible for approximately 70% and 78% of rotted peaches in 2005 and 2006 respectively. Serious damage (up to 5%) was also caused with the fungus Phomopsis amygdali. Other pathogens isolated from rotted peaches at a low percentage were Alternaria alternata, Aspergillus niger, Aspergillus flavus, Botrytis cinerea, Sclerotinia sclerotiorum, Fusarium spp., Colletotrichum gloeosporioides, Rhizopus stolonifer and Gilbertella persicaria. Most fungal isolates originated from the rotted peaches were tested for their sensitivity to the fungicides iprodione, carbendazim, thiophanate methyl and tebuconazole at label recommended concentrations. All fungicides inhibited the growth of M. laxa, A. niger, A. flavus, S. sclerotiorum, P. amygdali and B. cinerea on poisoned agar. Apart from iprodione, all other fungicides inhibited the mycelium growth of the pathogen Fusarium sp. The mycelium growth of Fusarium sp. was significantly less with iprodione than control. Only iprodione and tebuconazole were effective against A. alternata and R. stolonifer. Tebuconazole inhibited the mycelium growth of R. stolonifer, while iprodione reduced significantly in comparison to control. The mycelium growth of the fungus C. gloeosporioides was inhibited by tebuconazole and reduced significantly by the fungicides thiophanate methyl, carbendazim and iprodione. Among all the fungi tested, only M. laxa and B. cinerea isolates were found resistant to benzimidazoles [the EC50 (50% effective concentration) value was 100–200 mg/l and 200–300 mg/l for the largest number of thiophanate methyl‐ and carbendazim‐resistant M. laxa isolates respectively, while the biggest number of B. cinerea thiophanate methyl‐ and carbendazim‐resistant isolates showed EC50 value 200–300 mg/l and 300–400 mg/l, respectively]. However, these strains were sensitive to tebuconazole and iprodione. Therefore, these fungicides can be used as an alternative method to control benzimidazole‐resistant Monilinia and Botrytis isolates.     

Sensitivity to prochloraz in populations of the eyespot fungus, Pseudocercosporella herpotrichoides, in relation to fungicide treatments and their efficacy in continuous winter wheat

Eyespot was assessed and grain yields determined in the eighth and ninth years (1992 and 1993) of a field experiment in which the fungicides carbendazim and prochloraz were applied, separately or in mixtures, to plots of successive crops of winter wheat. Populations of the eyespot fungus, Pseudocercosporella herpotrichoides, were characterised by the proportions of cultures grown on agar from infected stems that were W-type or R-type, or were carbendazim-resistant or carbendazim-sensitive. Sensitivity to prochloraz in agar was determined for isolates from populations sampled in 1992 using restricted maximum likelihood analysis of EC50s (concentrations needed to decrease colony growth by 50%), to deal with the unbalanced data, and comparisons were made by Wald statistics. Control by prochloraz was maintained but in 1992, as in some previous years, its application with carbendazim was more effective than its application alone. Selection by prochloraz for strains sensitive to carbendazim continued to occur and may have contributed to its sometimes relatively poorer performance in the absence of carbendazim. R-type isolates taken from prochloraz-treated plots, with or without carbendazim, in 1992 were less sensitive to prochloraz than were isolates from plots untreated with prochloraz. There was evidence of a greater range of sensitivities to prochloraz in R-type than in W-type isolates (although some uncertainty results from the small numbers of W-type isolates obtained from some treatments), which would explain the selection of the R-type by prochloraz. The significance of these findings to modern wheat growing practices is considered.     

Effects of wheat foliar fungicides on the aphid endoparasitoid Aphidius rhopalosiphi DeStefani-Perez (Hym., Aphidiidae) on glass plates and on plants

Abstract: The side-effects of several fungicides used in wheat to control disease at heading growth stage were assessed on the aphid parasitoid Aphidius rhopalosiphi by tests conducted in the laboratory on glass plates and in the greenhouse on young wheat plants. Very few formulations containing only one active ingredient (carbendazim, cyproconazole or epoxyconazole) or combinations of two (carbendazim + cyproconazole, carbendazim + hexaconazole) were harmless to A. rhopalosiphi in the glass-plate tests. There was no apparent synergism between fungicides tested in combinations. The parasitoid mortalities in tests carried out on plants were less and chlorothalonil, epoxyconazole, fenpropidin, fenpropimorph, flusilazole, flutriafol, prochloraz, tebuconazole, tridemorph and a number of combinations (carbendazim + flutriafol, chlorothalonil + cyproconazole, epoxyconazole + tridemorph, chlorothalonil + hexaconazole, chlorothalonil + flutriafol, cyproconazole + prochloraz, epoxyconazole + fenpropimorph, fenpropimorph + propiconazole, propiconazole + tridemorph, triadimenol + tridemorph) were harmless or only slightly harmful to the aphid parasitoid. Several combinations (carbendazim + epoxyconazole, carbendazim + fenpropimorph, carbendazim + flusilazole, carbendazim + tebuconazole, chlorothalonil + fenpropimorph, chlorothalonil + flusilazole, fenpropimorph + fenpropidin, fenpropimorph + prochloraz, fenpropidin + propiconazole, fenpropidin + tebuco nazole, tebuconazole + triadimenol) were toxic for wasps on plants. The parasitoid mortalities were less on plants than on glass plates but the wasps spent less time on treated leaves and in some cases parasitism of aphids was reduced to a large extent. These results suggest that in addition to study of the direct effects of pesticides on beneficial insects (mortalities, reduction of fertility) their effects on the behaviour of the insects should also be studied. Products that induced a repellent effect need further testing in field or semi-field conditions. However, many fungicide combinations that have little or no effect on A. rhopalosiphi can protect wheat against a wide range of diseases and the results obtained in this study indicate that an appropriate and effective protection of wheat at earing growth stage can be achieved with products that have no effects on aphid parasitoids.     

Effects of selected pesticides used against glasshouse tomato pests on colony growth and conidial germination of Paecilomyces fumosoroseus

Two isolates of a potential biological control agent, Paecilomyces fumosoroseus, for greenhouse whitefly, Trialeurodes vaporariorum, on tomato in greenhouses were tested for their compatibility with five fungicides (captan, dichlofluanid, iprodione, benomyl, and carbendazim) and six insecticides (malathion, carbaryl, primicarb, pymetrozine, cypermethrin, and deltamethrine) which are used on glasshouse tomato. Conidial germinations after 24 h and radial growths after 14 days of inoculation were determined in the presence of each pesticide at three concentrations (recommended rate, 0.1 and 10 times of the recommended rate by its manufacturer) and resultant variations were evaluated. Our results suggest that the tested pesticides, especially the fungicides, have potential to interfere with the success of P. fumosoroseus if they are to be employed together. The recommended concentration rate of primicarb and pymetrozine, and the lower concentrations of cypermethrin and deltamethrin were less hazardous than the others.     

Efficacy of benzimidazole and related fungicides against Rhizoctonia solani and R. bataticola

Five formulations of four benzimidazole derived fungicides, carbendazim, benomyl, thiophanate methyl and methyl 4-[2-(2-dimethylamino acetamide) phenyl]-3-thioallophanate were compared for their toxicity towards two pathogenic isolates of Rhizoctonia solani and three of R. bataticola. The isolates of two fungi showed significant differences in mycelial growth inhibition by the five fungicides. Benomyl and carbendazim were most inhibitory to all isolates of both fungi while the sesame isolate of R. bataticola was least sensitive to all fungicides. Disease control (90%) was obtained with low concentrations of benomyl against root rot of cowpea caused by R. solani, and with thiophanate methyl against root rot of sesame and sunflower, and leaf blight of mung bean caused by R. bataticola. The spread of stalk-end rot of sunflower heads was best checked with a spray of thiophanate methyl. The results suggest that benzimidazole fungicides having similar toxophores act differently for disease control in different host-parasite combinations.     

Detection and molecular characterization of carbendazim-resistant Colletotrichum truncatum Isolates causing anthracnose of soybean in Thailand

A loss of fungicide efficacy, particularly for carbendazim, was noted in soybean fields in Thailand and was considered to be due to the development of Colletotrichum truncatum resistance. The carbendazim sensitivity of C. truncatum populations isolated from various soybean fields in Thailand was thus evaluated with in vitro sensitivity assays and molecular characterization of mutations in the sequences of the ß₂-tubulin (TUB2) gene that confer carbendazim resistance in the pathogen. Among 52 isolates, 46 isolates were classified as highly resistant (HR) to carbendazim (EC₅₀ > 1,000 µg/ml). All HR isolates grew on PDA amended with carbendazim at 1,000 µg/ml. Six isolates were classified as carbendazim sensitive (S) (EC₅₀ < 1 µg/ml). Mycelial growth on PDA amended with 1 µg/ml carbendazim was inhibited by over 50% compared with growth on PDA alone. When a partial TUB2 gene from the isolates was amplified and analysed using predicted amino acid sequences, an alteration from glutamic acid to alanine at codon 198 (E198A) was found in 45 HR isolates for which the EC₅₀ was higher than 2000 µg/ml. This mutation resulted from a nucleotide substitution from adenine to cytosine (GA G → GC G). The other HR isolate, CtPhS_1, with EC₅₀ of 1,127 µg/ml, had an alteration at codon 200 (F200Y) (TT C → TA C).     

Synthesis and Antifungal Activities of Trichodermin Derivatives as Fungicides on Rice

Twenty new trichodermin derivatives, 2a – 5 , containing alkoxy, acyloxy, and Br groups in 4‐, 8‐, 9‐, 10‐ and 16‐positions were synthesized and characterized. The antifungal activities of the new compounds against rice false smut (Ustilaginoidea virens), rice sheath blight (Rhizoctonia solani), and rice blast (Magnaporthe grisea) were evaluated. The results of bioassays indicated that the antifungal activities were particularly susceptible to changes at 4‐, 8‐, and 16‐positions, but low to changes at 9‐ and 10‐positions. Most of these target compounds exhibited good antifungal activities at the concentration of 50 mg l^?1. Compound 4 (9‐formyltrichodermin; EC₅₀ 0.80 mg l^?1) with an CHO group at 9‐position displayed nearly the same level of antifungal activity against Ustilaginoidea virens as the commercial fungicide prochloraz (EC₅₀ 0.82 mg l^?1), while compound 3f ((8R)‐8‐{[(E)‐3‐phenylprop‐2‐enoyl]oxy}trichodermin; EC₅₀ 3.58 and 0.74 mg l^?1) with a cinnamyloxy group at C(8) exhibited much higher antifungal activities against Rhizoctonia solani and Magnaporthe grisea than the commercial fungicides prochloraz (EC₅₀ 0.96 mg l^?1) and propiconazole (EC₅₀ 5.92 mg l^?1), respectively. These data reveal that compounds 3f and 4 possess high antifungal activities and may serve as lead compounds for the development of fungicides in the future.     

In vitro and In vivo Effects of Some Fungicides against the Chickpea Blight Pathogen, Ascochyta rabiei

The effects of various fungicides on mycelial growth and spore germination of Ascochyta rabiei were determined by incorporating them into potato dextrose agar and measuring colony diameter and observing colony growth and spore germination at 20 ± 2°C. Eight fungicides prevented spore germination of the pathogen at concentrations of 0.125–2 μg/ml, three hindered mycelial growth at 2–4 μg/ml and seven failed to inhibit mycelial growth even at 128 μg/ml. The reference fungicide for the pathogen, chlorothalonil, stopped conidial germination at low rates but did not prevent mycelial growth at 128 μg/ml. Thirteen fungicides were tested against seed infections of the pathogen, and benomyl + thiram, carbendazim and carbendazim + chlorothalonil seed treatments gave more than 85% inhibition on both vacuum‐infiltrated and naturally infected seeds. Coating the seeds with polymers did not increase the effectiveness of fungicides. Three fungicides; (azoxystrobin, chlorothalonil and mancozeb), gave the highest protection in the field but protection decreased with increased inoculum pressure. Addition of humic acid to fungicide suspensions did not affect their performance.     

Erfahrungen mit Spitzenmeristemkulturen von Pelargonien (Pelargonium zonale-Hybriden)

Six fungicides, namely Benlate (benomyl) methyl 1-(butylcarbamoyl)benzimidazol-2-ylcarbamate, 50%WP; Dithane M45 (mancozeb) 1,2-ethanediybis carbamodithioato (2-)manganese +1,2-ethanediybis, 20%Mn + 2.5%Zn; Delsene M, (carbendazim + maneb) methyl benzimidazol-2-ylcarbamate, 10% carbendazim + 60% maneb; Rovral (iprodione), 3-(3,5-dichlorophenyl)-N-isopropyl-2-4-dioxoimidazolidine-1-carboxamide, 50%WP; Cupravit (copper oxychloride) 3Cu(OH)₂ · CuCl 2 , 50%WP; and Ridomil (metalaxyl) methyl N-(2-methoxyacetyl)-N-(2,6-xylyl-DL-alaminate), 50%WP were evaluated for their efficacy in the control of brown blotch disease of bambara groundnut caused by Colletotrichum capsici (Syd) Butler and Bisby in field trials. Two of the fungicides, Benlate and Delsene M gave significantlty (P = 0.05) better control of the disease and consequently higher grain yield than the other treatments. The performance of Rovral, Dithane M-45 and Ridomil did not differ significantly from each other and Cupravit did not perform significantly better than the check treatment.