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.     

A Cucumber Disease Caused by Alternaria alternata and its Control

A severe leaf spot disease of cucumber caused by a pathotype of Alternaria alternata (Fr.) Keissler was recorded recently in plastic houses in Crete. Lesions ranged in size of a pin point to over 5 cm in diameter, with necrotic tissue on most of their area and a surrounding yellow zone. The pathogen grew satisfactorily on PDA at temperatures between 5 °C–40 °C and spore germination occurred in the range less than 10 °C to over 37 °C. Optimum temperature in both cases was near 26 °C. Of,13 fungicides tested in vitro, sodium omadine, etem, dichlofluanid, captan and folpet were the most inhibitory on spore germination, and iprodione, sodium omadine and dichlofluanid on mycelial growth. Of 25 fungicides applied on two leaf cucumber plants 24 h before inoculation, maneb, etem, dichlofluanid and chlorothalonil were the most effective. When the last fungicides, plus mancozeb, were applied 24 h after inoculation only maneb was effective. In greenhouse experiments, iprodione, prochloraz-manganese-complex, chlorothalonil, dichlofluanid, guazatine, maneb and etem were the most effective for disease control, while mancozeb was less effective. The local cucumber cv. Knossos and the Dutch F₁ hybrids Evadan, Frella, Herta, Malfa, Mazourka, Pepinex 69 and Renova were all susceptible to infection.     

Effectiveness of acibenzolar-S-methyl, fungicides and antibiotics for the control of brown eye spot, bacterial blight, brown leaf spot and coffee rust in coffee

This study was carried out to evaluate the potential of acibenzolar‐S‐methyl (ASM), combined or not combined with fungicides and antibiotics for the control of brown eye spot (Cercospora coffeicola) and bacterial blight (Pseudomonas syringae pv. garcae) in coffee seedlings, and ASM combined with conventional fungicide application schedules for the control of coffee rust (Hemileia vastatrix) and brown leaf spot (Phoma costarricencis) under field conditions in two coffee crops in the State of São Paulo, Brazil. ASM protected coffee seedlings against C. coffeicola when applied at the rates of 2.5 and 5 g of active ingredient per hectolitre of water (g a.i. hL^?1), providing 34–55% of disease control, and against bacterial blight, when applied at the rates of 2.5, 10 and 20 g a.i. hL^?1, with 38–57% of disease control. Tebuconazole (100 g a.i. hL^?1) and azoxystrobin (10 g a.i. hL^?1) showed the best results for brown eye spot control. Oxytetracycline + streptomycin, kasugamycin hydrochloride, oxytetracycline + metallic copper, copper oxychloride and mancozeb + copper oxychloride also controlled bacterial blight in levels similar to those shown by ASM. In the field experiments, all fungicide application schedules tested, cyproconazole (December, February, April), epoxiconazole (December, March), tetraconazole (December, February, April), cyproconazole (December, February) and azoxystrobin (January, March) were effective for coffee rust control and provided partial control of brown leaf spot. The results also showed that for all experiments, there was no synergistic effect of the combination of ASM with azoxystrobin, cyproconazole or cupric fungicides.     

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.     

Isolates of Didymella bryoniae from South Carolina Remain Sensitive to DMI Fungicides Despite Multiyear Exposure

Triazole fungicides, which are sterol demethylation inhibitors, have become the primary systemic fungicides applied to cucurbits to control gummy stem blight caused by Didymella bryoniae. Isolates of D. bryoniae from South Carolina that were never exposed to tebuconazole or exposed for several years were tested for sensitivity to tebuconazole and difenoconazole. Colony diameters, percentage germination of ascospores and conidia, and germ tube lengths were measured when isolates were grown on agar amended with 0.10–10.0 mg/l tebuconazole and 0.01–1.0 mg/l difenoconazole. All 147 isolates tested were sensitive to tebuconazole and difenoconazole with mean EC₅₀ values of 0.41 and 0.054 mg/l, respectively. Ascospore germination was greater than conidia germination on fungicide‐amended agar. Although the length of germ tubes arising from both spore types was reduced by both fungicides, the reduction was greater for ascospore germ tubes than for conidia germ tubes. Because many watermelon growers rotate crops among fields every two years, local populations of D. bryoniae have not been exposed repeatedly to tebuconazole. In addition, growers often apply a rotation of systemic and contact fungicides. Thus, despite exposure to tebuconazole for up to nine years, isolates of D. bryoniae from South Carolina remain sensitive to triazole fungicides.     

Tests of fungicides against Alternaria brassicicola and studies on some factors enhancing attack by the fungus

When various fungicides were sprayed on detached cabbage cotyledons in the laboratory and on young plants in the glasshouse, propineb and mancozeb at 0·2 % a.i. consistently gave good protection against subsequent infection by spores of Alternaria brassicicola. Copper oxychloride, zineb, thiram and maneb showed promise in the laboratory, but were less successful in the glasshouse. Two fentin compounds were active at low concentrations against the fungus but were phytotoxic. Increased pathogenicity of A. brassicicola in the presence of cabbage pollen and of downy mildew infection in the laboratory is reported.     

Comparison of fungicides for control of leaf spot (Septoria apiicola) of celery

Of twenty-one fungicides tested at recommended rates of application for their effectiveness in controlling leaf spot of celery grown in Ireland on peat and on a clay-loam soil, three formulations containing fentin acetate with maneb and formulations of fentin hydroxide and fentin chloride were most effective. Benomyl was superior to the other non-tin fungicides tested and, at moderate disease levels, it resulted in marketable yields of celery equal to those recorded after treatment with the organotin compounds. Generally, the organotin compounds and benomyl were followed in descending order of effectiveness by copper oxychloride, captafol, Daconil 2787 and maneb. None of the fungicides tested in the three seasons caused visible symptoms of phytotoxicity and, on disease-free celery in 1969, none had a significant effect on yield.     

Pathogenicity of fungi associated with wheat and barley seedling emergence and fungicide efficacy of seed treatment

Presented study focused on the influence of Cochliobolus sativus isolates origin on pathogenicity towards wheat and barley seedlings in comparison with pathogenicity of certain Fusarium species and Microdochium nivale. The efficacy of fungicide seed treatment against C. sativus was estimated. The C. sativus isolates were collected from different locations and were isolated from wheat, barley and sunflower seeds. The pathogenicity of C. sativus, Fusarium species and M. nivale towards germinating seedlings were expressed as germination (GA) retardation and coleoptile growth rate retardation (CGR). Of wheat only, the CGR was significantly influenced by the isolate origin. The C. sativus isolates obtained from sunflower seeds were the most aggressive. Of the barley seeds, the barley isolates were the most aggressive. Barley was significantly more susceptible to damage by C. sativus isolates than wheat. The pathogenicity of tested fungal species declined in the order: F. culmorum, F. graminearum, C. sativus, F. avenaceum, M. nivale, F. poae for both barley and wheat. The results highlighted high pathogenicity potential of C. sativus equal to that of F. avenaceum and M. nivale. The symptoms of C. sativus on coleoptile and roots were very similar or the same as the symptoms caused by Fusarium species and M. nivale, except of white, pink or red colours. Of wheat sprouts, the fungicide efficacy (FE) against C. sativus declined in the order: tebuconazole + thiram, carboxin + thiram, quazatine, difenoconazole, iprodione + triticonazole (in term of GA) and carboxin + thiram, iprodione + triticonazole, tebuconazole + thiram, difenoconazole, quazatine (in term of CGR). In barley, the FE declined in the order: carboxin + thiram, iprodione + triticonazole, tebuconazole + thiram, difenoconazole, quazatine (in term of GA) and carboxin + thiram, tebuconazole + thiram, difenoconazole, iprodione + triticonazole, quazatine (in term of CGR).     

The effects of organic pesticides on inner membrane permeability in <Emphasis Type="Italic">Escherichia coli</Emphasis> ML35

We have tested whether some pesticides might cause inner membrane leakage in ML35 Escherichia coli cells, which express β-galactosidase (lacZ; EC 3.2.1.23) constitutively but lack the permease (lacY) required for substrate entry. The activity of β-galactosidase (indicative of substrate leakage through the inner membrane) was increased by various concentrations of pesticides, including the organometallic fungicides maneb and mancozeb, the insecticide Thiodan, and the herbicide Ally, as well as by antibiotics such as ampicillin, gramicidin D, and the calcium ionophore A23187. The enzyme activity was increased by up to ∼30% when the E. coli ML35 strain was exposed to various concentrations (between 50 and 250 ppm) of both fungicides. Thiodan had only a slight effect on β-galactosidase activity (increase of 12.8%), whereas, among the antibiotics, the calcium ionophore at 20 μg/ml caused a significant increase in enzyme activity by up to 61.8%. This effect is similar to that of sodium dodecyl sulfate, used as positive control (∼70% increase). Accumulation of maneb and mancozeb by bacterial cells was also studied taking advantage of their metal content and using atomic absorption spectrophotometry. In parallel with the increase in enzyme activity, both fungicides accumulated in the cells as a function of their concentration. Time course experiments (3, 6, and 9 h) of fungicide accumulation and of bacterial growth at various pesticide concentrations were also carried out. Maneb seems to inhibit the bacterial growth better than mancozeb. In addition, maneb uptake increases with time up to 9 h at all tested concentrations, whereas the accumulation of mancozeb is similar at all the exposure times tested. This indicates a different uptake and/or metabolizing strategy by E. coli cells for the two fungicides.     

Determination of manganese‐ and manganese‐containing fungicides with lucigenin–Tween‐20‐enhanced chemiluminescence detection

A flow‐injection (FI) method is reported for the determination of Mn(II), maneb and mancozeb fungicides based on the catalytic effect of Mn(II) on the oxidation of lucigenin and dissolved oxygen in a basic solution. The Tween‐20 surfactant has been reported for first time to enhance lucigenin chemiluminescence (CL) intensity in the presence of Mn(II) (53%) and maneb and mancozeb (89%). The calibration graphs were linear in the concentration range of 0.001–1.5 mg L^–1 (R² = 0.9982 (n = 11) with a limit of detection (S/N = 3) of 0.1 µg L^–1 for Mn(II) and 0.01–3.0 mg L^–1 [R² = 0.9989 and R² = 0.9992 (n = 6)] with a limit of detection (S/N =3) of 1.0 µg L^–1 for maneb and mancozeb respectively. Injection throughputs of 90 and 120 h^–1 for Mn(II) and maneb and mancozeb respectively, and relative standard deviations of 1.0–3.4% were obtained in the concentration range studied. The experimental variables, e.g., reagents concentrations, flow rates, sample volume, and photomultiplier tube voltage, were optimized and potential interferences were investigated. The analysis of Mn(II) in river water reference materials (SLRS‐4 and SLRS‐5) showed good agreement with the certified values incorporating an on‐line 8‐hydroxyquinoline chelating column in the manifold for removing interfering metal ions. Recoveries for maneb and mancozeb were in the range of 92 ± 5 to 104 ± 3% and 91 ± 2 to 100 ± 4% (n = 3) respectively. The effect of 30 other pesticides (fungicides, herbicides and insecticides) was also examined in the lucigenin–Tween‐20 CL system. Copyright © 2015 John Wiley & Sons, Ltd.     

Mycorrhizal growth in pure cultures in the presence of pesticides

The effects of pesticides on 64 ectomycorrhizal fungi of boreal forest trees were studied in vitro. The pesticides (fungicides: benomyl, chlorothalonil, copper oxychloride, maneb and propiconazole; herbicides: chlorthiamid, glyphosate, hexazinone, linuron and terbuthylazine; insecticide: cypermethrin) were selected as those commonly used in Nordic forest nurseries and afforestation sites. In general, the fungicides proved to be more toxic to ectomycorrhizal fungi than the herbicides and cypermethrin. The fungicides, chlorothalonil and propiconazole, had the clearest inhibitory effect on growth of mycorrhizal fungi. Conversely, maneb, glyphosate and terbuthylazine stimulated the growth of some mycorrhizal fungi. Leccinum versipelle and L. scabrum, Paxillus involutus and Cenococcum geophilum were the most sensitive ectomycorrhizal fungi to the various pesticides.     

Evaluation of fungicides to control potato late blight (Phytophthora infestans) in the plains of Nepal

Fungicide application is an effective management option to control late blight of potato (caused by Phytophthora infestans). Field experiments were conducted to evaluate the efficacy of recently introduced and previously used fungicides on late blight management and potato yields in the western plains of Nepal in 2015 and 2016 crop seasons. Fungicides and a non-treated control (NTC) were replicated three times in a randomized block design planted with late blight susceptible cultivar Cardinal. Chlorothalonil, copper oxychloride, dimethomorph, fenamidone + mancozeb, mancozeb and metalaxyl were sprayed in 2015. In 2016, carbendazim was used instead of chlorothalonil. The area under disease progress curve (AUDPC) was consistently reduced in years by dimethomorph (90% and 65% in 2015 and 2016, respectively), fenamidone + mancozeb (68% and 62%) and mancozeb (40% and 47%) compared with the NTC. Similarly, tuber yield was increased with the application of dimethomorph (266% and 146% in 2015 and 2016, respectively), fenamidone + mancozeb (211% and 155%) and mancozeb (136% and 116%) compared with the NTC. Chlorothalonil reduced AUDPC by 43% and increased tuber yield by 170% in 2015. Other fungicides either had inconsistent results or did not reduce late blight severity and consequent effects on potato yield. The overall benefit–cost ratio was highest for dimethomorph in both years. These results show efficacy of dimethomorph, fenamidone + mancozeb and mancozeb in reducing late blight severity and increasing potato tuber yield in the plains of Nepal.     

Biology and Control of Entyloma eryngii (Cda.) de By., the Cause of a Leaf Spot Disease on the Blue Thistle (Eryngium alpinum L.)

The blue thistle (Eryngium alpinum L.), an indigenous perennial flower of the alps, is grown in mountainous regions of south-eastern Switzerland. The commercial value of the fresh cut flowers can be seriously reduced due to a leaf spot disease caused by the smut fungus Entyloma eryngii (Cda.) de By. The fungus produces thick walled chlamydospores and two types of conidia. The disease appears to be favoured by cool-rainy weather and a dense foilage resulting in long periods of leaf wetness. Control of the disease can be achieved with the protective fungicide mancozeb or even more efficiently with the systemic ergosterol-biosynthesis-inhibiting fungicides cyproconazole and difenoconazole.     

Control of smoulder (Botrytis narcissicold) in narcissus with fungicides

Smoulder, caused by Botrytis narcissicola, is the most widespread foliar disease of narcissus (Narcissus cultivars) in the UK and causes significant losses in bulb and flower yield. A range of current and novel fungicide treatments was examined to determine if control of the disease could be improved and to measure the effect of treatments on bulb yield. In assays on pot-grown plants, carbendazim+flusilazole, epoxiconazole, iprodione + thiophanate-methyl, tebuconazole and vinclozolin reduced lesion size by more than 90%, compared with untreated plants, when applied 1 day before inoculation with the fungus; vinclozolin and tebuconazole were also effective when applied 2 days after inoculation. In field experiments in Cambridgeshire and Lincolnshire, significant reductions were observed in secondary smoulder symptoms (leaf lesions and stem rot) following fungicide sprays. Spray programmes of the novel fungicides azoxystrobin, cyprodinil, kresoxim-methyl, tebuconazole and pyrimethanil were as effective, or more so, than the standard treatments (chlorothalonil, vinclozolin) used by growers. Mixtures of carbendazim + tebuconazole and azoxystrobin + tebuconazole also gave effective control of smoulder. Programmes of four to six sprays, using two or three fungicides with different modes of action, applied alternately, reduced smoulder by 35–69% and increased bulb yields by 7–59%. Although treatment around and after flowering resulted in the greatest control of secondary smoulder, treatment before flowering was required for the highest bulb yields. The choice of fungicides for use in spray programmes to provide effective and reliable control of smoulder, and the possibility of control using fewer sprays, are discussed.     

Condition of Scots pine fine roots and mycorrhiza after fungicide application and low-level ozone exposure in a 2-year field experiment

 In a 2-year experiment at an open-air ozone fumigation field, the effects of fungicide application and low-level ozone exposure, single and combined, on fine root and mycorrhiza condition of Scots pine (Pinus sylvestris) seedlings were studied. Two different fungicides, copper oxychloride and propiconazole, with different modes of actions, were used. Propiconazole treatment reduced mycorrhizal infection in both years while copper oxychloride treatment and ozone exposure slightly stimulated mycorrhizal infection after the first year. Different mycorrhizal morphotypes showed different kinds of responses to the two fungicides. Light brown morphotype appeared to be the most sensitive one to propiconazole treatment. After the second year, ectendomycorrhizas disappeared in propiconazole treatment while in control treatment ectendomycorrhizas formed the majority of the light brown morphotype. The root biomass was not affected by fungicide treatments, but ozone exposure increased the total amount of short roots and the fresh weight of propiconazole treated roots. No significant differences in the concentrations of ergosterol, starch and total phenolics in pine roots between treatments were found. However, ergosterol concentration correlated positively with the mycorrhizal infection level. Both fungicides reduced the soil respiration compared to controls. At the ultrastructural level, both fungicides caused increased transparency and gradual granulation and degeneration of cytoplasm in the fungal symbiont of mycorrhizal short roots. Slightly elevated ozone did not have harmful effects on root ultrastructure. These results suggest that fungicides have deleterious effects on the quantity and quality of mycorrhizas in Scots pine roots and also side-effects on non-target soil fungi. Some of these deleterious effects were noticeable only at the ultrastructural level. Received: 23 June 1997 / Accepted: 11 December 1997     

Utility of six fungicides for selective isolation of Evlachovaea sp. and Tolypocladium cylindrosporum

The effects of the fungicides dodine, benomyl, thiabendazole, mancozeb, cupric sulfate, and copper oxychloride were examined in vitro upon germination and further development of Evlachovaea sp. and Tolypocladium cylindrosporum. Fungicidal activity depended on concentrations and varied among products, fungi and the strains tested. Depending on the fungicidal concentration, germination of conidia was induced but germlings produced neither mycelium nor new conidia. There was a good recovery of both Evlachovaea sp. and T. cylindrosporum from previously sterilized soils with fungicide-supplemented medium. Fungi were resistant to copper oxychloride up to 30 g/l, and this fungicide was found to have no utility for a selective medium. Minimal fungicide concentrations for successful isolations were 1 mg/l for benomyl, 200 mg/l for cupric sulfate, 50 mg/l for dodine, 100 mg/l for mancozeb, and 4 mg/l for thiabendazole. Thiabendazole, which is easy to obtain and can be used in low quantities, showed the greatest utility for a selective medium with these entomopathogenic fungi. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

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.     

Effect of carbendazim and mancozeb combinationon Alternaria leaf blight and seed yield in sunflower (Helianthus annus L.)

Abstract

Leaf blight caused by Alternaria helianthi (Hansf.) Tubaki & Nishihara, is the major disease of sunflower affecting the successful cultivation across India. Five individual fungicides and two combination fungicides were evaluated against this pathogen in laboratory and in field experiments. Among them, the combination of carbendazim + mancozeb completely (100%) inhibited the mycelial growth of A. helianthi, irrespective of the concentrations tested followed by carbendazim alone and metalaxyl + mancozeb under in vitro condition. In field conditions, the combination of carbendazim + mancozeb was found to be highly effective in reducing the leaf blight disease of sunflower in all the three experiments as compared to other fungicides and unsprayed control. The reduction of Alternaria leaf blight was also directly associated with an increase in seed yield. The economics of the fungicides spray has been worked out and the benefit cost ratio for the combination of carbendazim + mancozeb at 2.0 g/l was 7.1 as compared to unsprayed control. The overall analysis of the results revealed that the combination of carbendazim + mancozeb at 2.0 g/l can be used for the management of foliar diseases such as Alternaria leaf spot/blight in agricultural crops.     

Effects in vitro of nine fungicides on growth of entomopathogenic fungi

The effects of nine fungicides were evaluated in vitro on the entomopathogenic fungi Beauveria bassiana, Conidiobolus coronatus, C. thromboides, Metarhizium anisopliae, Paecilomyces farinosus, P. fumosoroseus, Scopulariopsis brevicaulis and Verticillium lecanii. The susceptibility of the fungi to the fungicides varied. The dithiocarbamate derivations zineb + copper oxychloride, and mancozeb completely inhibited germination of C. coronatus, C. thromboides, B. bassiana, P. farinosus, M. anisopliae and V. lecanii. The fungicides triadimefon, copper oxychloride, metalaxyl, sulfur, sulfur + nitrothal‐isopropyl and hymexazol exhibited various effects on the fungi. Usually, fungistasis was more pronounced at 15°C than at 25°C and the inhibitory effects were in direct proportion to the dosage of active ingredient (recommended field rate, 10‐fold higher and 10‐fold lower). In a few combinations, fungi partially overcame or even recovered from the initial inhibition of growth which might have resulted from delayed germination. In other cases, inhibition of growth occurred only after a delay and its intensity increased with time. Stimulation of fungal growth when it occurred was rarely permanent. Generally, adverse effects were much greater against the entomophthoraleans C. coronatus and C. thromboides than against the Hyphomycetes. Extrapolation of the results to practice and to the field situation is difficult. Nevertheless, the data presented give an idea of possible side‐effects in nature.     

Susceptibility and Resistance of Citrus Genotypes to Alternaria alternata pv. citri

A survey of citrus cultivars in Israel in orchards where Alternaria brown spot was common on Minneola tangelos (mandarin × grapefruit), revealed the occurrence of the disease as typical foliar and fruit lesions on Dancy and Ellendale (mandarins), on Murcott tangor (mandarin × sweet orange), on Nova and Idith (mandarin hybrids), on Calamondin, and on Sunrise and Redblush (grapefruit). Isolates of Alternaria alternata from each of these hosts were proven to be pathogenic to Minneola tangelo.
The host range of A. alternata pv. citri from Israel was assayed by inoculating leaves of diverse citrus genotypes. Several mandarins and their hybrids (Dancy, Kara, King, Wilking, Satsuma, Minneola, Orlando, Mikhal, Idith, Nova, Page, Murcott), grapefruit (Marsh seedless), grapefruit × pummelo (Oroblanco), sweet orange (Shamouti, Valencia, Washington navel) Calamondin, and Volkamer citrus were susceptible. Several mandarins and their hybrids (Clementine, Avana, Yafit, Ortanique), Cleopatra, one sweet orange cultivar (Newhall), pummelo (Chandler), lemon (Eureka), Rough lemon, Rangpur lime, sweet lime, citron, limequat, sour orange, Troyer citrange and Alemow were resistant.