Creation of a non-mycorrhizal control for a bioassay of AM effectiveness

and application times 2 weeks before sowing, at sowing and 1 week after sowing were investigated. Various Finnish field soils with their indigenous AMF communities were used. The main test plant species was oil-seed flax (Linum usitatissimum). In a comparison of sampling time, barley (Hordeum vulgare) was also used and phytotoxicity was studied additionally on red clover (Trifolium pratense), barley and pea (Pisum sativum) mutants. Sampling in the spring after the thaw resulted in the highest infectivity and AM response and the clearest differences between soils with varying AM potential. No evidence of temporal variation in benomyl effectiveness on mycorrhiza was found. The dose of benomyl sufficient to create a control with suppressed mycorrhization was 20 mg per kg soil at target moisture incorporated in the soil. Plant growth reduction in irradiated soil was observed with benomyl application 1 week after sowing only with flax and red clover. The most effective application time for benomyl was immediately before sowing.     

The effect of fungicides on incidence of Sporobolomyces spp. and Cladosporium spp. on flag leaves of winter wheat

Sprays of benomyl, thiophanate methyl, NF 48 and captafol considerably decreased incidence of Sporobolomyces spp. and Cladosporium spp. on flag leaves of winter wheat. BAS 3170 F affected both genera but much less. Tridemorph and triforine had relatively little effect on Sporobolomyces spp. but tridemorph did decrease Cladosporium spp. Sandoz 52.133 affected only Cladosporium spp. and ethirimol affected neither genus.     

Effects of chemical treatments for mildew control at different times on the growth and yield of spring barley

Experiments in 1973 and 1974 tested the effects of ethirimol seed treatment and the timing of single sprays of ethirimol or tridemorph, on mildew control and the growth and yield of spring barley. These treatments were compared with selected combinations of two treatments designed to give longer protection. In 1973, combinations of seed treatment and spray, or two sprays, did not yield better than the best component treatment applied alone or the most effective single spray of tridemorph applied on 1 June. In 1974, mildew developed usually early and yields were increased by applying ethirimol to the seed plus a tridemorph spray or two tridemorph sprays. However, barley sprayed once with tridemorph on 20 May, the expected best date, yielded more than barley receiving a seed treatment of ethirimol plus a tridemorph spray applied on either 3 or 12 June. Sprays of captafol and tridemorph, applied as separate treatments, successively to the same plots on three occasions, gave the best yields in both years. Treatments most affected ear number but they did have some effect on all components of yield. In 1974 there was a significant relationship between ear number and the variance of the number of grains per ear.     

Effect of Four Fungicides on Barley Net Blotch Caused by Drechslera teres

The effect of four fungicides (benomyl, carbendazim, triadimefon and sulp hur), used in intensive barley cropping on the epidemiology of Drechslera teres f. maculata and f. teres, was investigated under a controlled environment. Two fungicides (benomyl and carbendazim) increased disease development, especially at the recommended field rate, sulphur had the same effect at lower concentrations and triadimefon promoted net blotch caused by D. teres f. teres. At the recommended field rate, carbendazim enhanced sporulation in the two pathogen forms, whereas benomyl and sulphur enhanced 14 sporulation only on the maculata form. The results showed that, under controlled conditions, most of the fungicides promotednet blotch development and that sporulation increased either as a result of the pathogen form or of the concentration of the active ingredient.     

Influence of benomyl on photosynthetic capacity in soybean leaves

This investigation was performed to study the influence of benomyl on photosynthetic pigments and enzymes in soybean leaves. Chlorophyll and pheophytin levels were reduced by benomyl 45 days after greening. These results indicate that chlorophylla andb, and pheophytin must be controlled by benomyl. SDS-PAGE analysis showed that 50 and 14.5 kD polypeptides represented as the large and small subunits of rubisco. In the both of these subunits, the band intensity of the control was significantly higher than that after benomyl treatment, indicating that these two subunits are affected by benomyl. Benomyl strongly inhibited both the activity and content of rubisco as its concentration was gradually increased. However, it remains unclear whether this reduction of rubisco level was due to a reduced level of rubisco activase. Two major polypeptides of 46 and 42 kD were identified as rubisco activase subunits by SDS-PAGE. The intensity of these two bands was shown to be higher in the control than after benomyl treatment. These results indicate that the rubisco decrease resulting from increased benomyl concentrations was caused by rubisco activase. A significant decrease in both the activity and content of rubisco activase by benomyl was also observed. These results suggest that the decrease in rubisco level caused by benomyl is accompanied by a decrease in both the activity and content of rubisco activase.     

The fate of carboxin, benomyl and thiabendazole in seed- and soil-treated plants, as shown by in vitro and in vivo bioassays on some epiphytic yeasts

The yeast, Sporobolomyces roseus, when added to leaves of barley and pea seedlings seed- and soil-treated with carboxin, benomyl or thiabendazole (TBZ), sporulated little or not at all from both sides of the first leaves. Second leaves of barley and third of pea gave similar results. Tests in vivo showed that all three chemicals reduced sporulation of S. roseus at lower concentrations than they did growth, and also delayed sporulation. Leaves from benomyl- or TBZ-treated plants inhibited the growth of sensitive test organisms (S. roseus, Leucosporidium scottii and Aureobasidium pullulans), on agar: it is considered that fungitoxic substances are excreted from both faces of leaves of barley and pea treated with these chemicals. Leaves from carboxin-treated plants, however, did not inhibit sensitive test organisms (S. roseus, L. scottii and Ustilago hordei), so their inhibitory action in vivo is deemed to result from hormonal imbalance in treated plants: carboxin-treated barley plants were greener than control plants, no guttation occurred on leaves, and stomata tended to remain open; treated barley and pea were more sensitive to drought than were controls. Carboxin-treated barley and pea plants sprayed with the cytokinin antagonist, abscisic acid, behaved as did plants without carboxin. It is considered likely that carboxin affects the epiphytes by creating a leaf surface incapable of sustaining them, possibly through dryness.     

Effects of fungicide timing on control of Rhynchosporium secalis in barley plants

Sprays of captafol, carbendazim, carbendazim + tridemorph + maneb, diclobutrazol, triadimefon or triadimefon + carbendazim all completely protected barley plants in a glasshouse against R. secalis for at least 30 days. However, their effectiveness in preventing disease development when applied after inoculation differed: triadimefon, traidimefon + carbendazim, or diclobutrazol were the most effective, completely preventing symptom development when applied up to 5 days after inoculation to plants grown above 16 °C, and up to 8 days below 8 °C. All the fungicides decreased the number of viable conidia produced by leaf blotch lesions, and when applied to infected plants at G. S. 30, greatly decreased the upward spread of the disease under simulated rain conditions; the most effective fungicides in these respects were triadimefon and triadimefon + carbendazim. The above fungicides and fungicide mixtures, together with the recently introduced materials fenpropimorph and propiconazole were applied to diseased winter barley crops in winter or in spring. All treatments decreased leaf blotch development and increased yields. In most cases, a winter application was more effective than spring applications, particularly if applied in mid-November. The most effective fungicides were triadimefon and propiconazole. The field trials data fitted well with the predictions of performance indicated by the glasshouse investigations.     

Effect of some fungicides on the yield of grass swards

When benomyl, drazoxolon, thiabendazole or zineb were applied as soil drenches to established grassland drazoxolon reduced the incidence of rhizoplane fungi. Benomyl and thiabendazole significantly increased yield at one harvest but only benomyl had a significant effect on total yield. When benomyl was applied at monthly intervals from March to July significant increases in total yield were obtained with the June applications which also significantly increased yield at the first harvest in the following year. Repeated applications from March to July also had a significant residual effect on total yield. Yield increases were not significantly affected by increasing the benomyl level from 2.5 to 5.0 g/m².     

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.     

Effect of the fungicide benomyl on spore germination and hyphal length of the arbuscular mycorrhizal fungus Glomus mosseae.

The fungicide benomyl inhibited spore germination and hyphal length of the arbuscular mycorrhizal fungus Glomus mosseae when applied at doses of 21.25 microg/ml (agronomic dose), 10.62 microg/ml and 10 microg/ml. G. mosseae was able to germinate in the presence of 2.12 microg/ml of benomyl, and the percentage of spore germination was unaffected by dosis of 0.1, 0.01 and 0.001 microg/ml of the fungicide. However, all doses of fungicide tested in this study decreased the hyphal length. When ungerminated G. mosseae spores previously exposed to benomyl were transferred to water-agar medium without benomyl, the maximum germination was 16%. Small spores of G. mosseae were more resistant to benomyl than the larger ones. Our results show some of the factors which can explain the variability of the effect of benomyl on arbuscular mycorrhizal fungi.     

The effect of carbendazim-generating fungicides with and without a mineral oil additive on tomato stem lesions caused by carbendazim-sensitive and tolerant strains of Botrytis cinerea

Isolates of Botrytis cinerea were obtained from tomatoes in several localities in the West Scotland. Some isolates grew on agar containing 100 mg/1 benomyl (carbendazim-tolerant), while others did not (carbendazim-sensitive). Pot-grown tomato plants treated with benomyl and other carbendazim-generating fungicides, applied either as sprays or soil drenches, were inoculated on the leaf scars with some of these isolates. On treated plants the carbendazim-tolerant isolates formed lesions which were about as large as those on untreated plants. Sensitive isolates formed much smaller lesions on treated plants. There was evidence that the increase in lesion size during the period 7–14 days after inoculation with a carbendazim-sensitive isolate was less on plants sprayed with benomyl or carbendazim with added mineral oil (2% Actipron) than on plants to which the fungicides alone had been applied. No such effect was recorded with thio-phanate-methyl. There was also an indication that the addition of Actipron to a benomyl spray improved the effect of the fungicide against two tolerant isolates, though there was no effect on the relative increase in lesion size during the second week after inoculation. In two tests the addition of 2% and 4% Actipron to benomyl soil drenches did not improve the level of leaf scar lesion control.     

Induced Phytoextraction of Lead Through Chemical Manipulation of Switchgrass and Corn; Role of Iron Supplement

The effects of combined chemical application of benomyl, ethylenedianinetetraacetate (EDTA), and iron (Fe) (foliar and root) on lead (Pb) phytoextraction by switchgrass (Panicum virgatum) and corn (Zea mays) was examined. Switchgrass was grown in Pb-contaminated urban topsoil with the following treatments: (C) Control, (B) benomyl, (E) EDTA, (F) foliar-Fe, (BE) benomyl + EDTA, (BF) benomyl + foliar-Fe, (FE) foliar-Fe + EDTA, (BFE) benomyl + foliar-Fe + EDTA. Corn was grown in sand-culture supplemented with Pb (500 mg kg^?1) with the following treatments: (C) control, (B) benomyl, (E) EDTA, (F) root-Fe, (BE) benomyl + EDTA, (BF) benomyl + root-Fe, (FE) root-iron + EDTA, and, (BFE) benomyl + root-Fe + EDTA. All treatments were replicated three times and pots were arranged in a completely randomized design. Plants were analyzed for element concentration (Fe, Zn, P, and Pb) using either inductively coupled plasma (argon) atomic emission spectroscopy (ICP-AES) or graphite furnace atomic absorption spectrometer. Iron supplementation (foliar and root) affected Pb-translocation in plants. Foliar-Fe treatment increased translocation ratio of Pb (TF-Pb) significantly compared to other treatments with the exception of plants treated with benomyl and BF. Root-Fe treatment in combination with EDTA (FE) increased TF-Pb significantly compared to other treatments. Phytoextraction was improved by the combined chemical application; plants treated with BFE treatment increased Pb-total-phytoextraction by 424% compared to Control plants.     

Mitochondria and nuclei move by different mechanisms in Aspergillus nidulans

We have examined the effects of the antimicrotubule agent benomyl and several mutations on nuclear and mitochondrial movement in germlings of the filamentous fungus Aspergillus nidulans. While, as previously reported, benomyl inhibited nuclear division and movement, it did not inhibit mitochondrial movement. To test the effects of benomyl more rigorously, we germinated two benomyl super-sensitive, beta-tubulin mutants at a benomyl concentration 50-100 times greater than that required to inhibit colony formation completely. Again nuclear division and movement were inhibited, but mitochondrial movement was not. We also examined conditionally lethal beta-tubulin mutations that disrupt microtubule function under restrictive conditions. Nuclear division and movement were inhibited but, again, mitochondrial movement was not. Finally we examined the effects of five heat-sensitive mutations that inhibit nuclear movement but not nuclear division at restrictive temperatures. These mutations strongly inhibited nuclear movement at a restrictive temperature but did not inhibit mitochondrial movement. These data demonstrate that the mechanisms of nuclear and mitochondrial movement in Aspergillus nidulans are not identical and suggest that mitochondrial movement does not require functional microtubules.     

Inhibition of yeast respiration and fermentation by benomyl, carbendazim, isocyanates, and other fungicidal chemicals

The inhibition of yeast (Saccharomyces cerevesiae) metabolism by fungicidal chemicals was investigated. Glucose- or ethanol-dependent yeast respiration was measured with an oxygen electrode, and manometric determination of carbon dioxide release was used to measure fermentation. Both respiration and fermentation were inhibited more by benomyl than by identical molar concentrations of its breakdown product, carbendazim. Butyl isocyanate, another benomyl breakdown product, inhibited respiration more but inhibited fermentation less than the parent compound. Of the isocyanates tested, hexyl isocyanate was the most inhibitory towards both activities. Captan was more active and iprodione less active than benomyl. Because benomyl rapidly broke down to carbendazim when it was prepared in 80% ethanol, only 59% of the dissolved benomyl was intact when it was added to yeast to determine its effect on respiration or fermentation.     

The effects of sowing date and choice of insecticide on cereal aphids and barley yellow dwarf virus epidemiology in northern England

During the mid-1980s, Sitobion avenae became recognised as an important vector of barley yellow dwarf virus (BYDV) in the Vale of York. A field trial at the University of Leeds Farm, North Yorkshire, was carried out during the autumn/winter of 1984-85 to evaluate different control procedures against S. avenae-transmitted BYDV and to investigate its epidemiology. Winter barley was sown on three dates in September, and plots were sprayed with either deltamethrin, demeton-S-methyl or pirimicarb on one of three dates between mid-October and mid-November, making a factorial design. Rhopalosiphum padi, the main vector of BYDV in southern England, were rarely found during the experiment, but the numbers of S. avenae were much higher, reaching a peak of 21% of plants infested in the unsprayed plots of the first sowing date. Single applications of each insecticide reduced populations of S. avenae to zero. Some treatments, particularly in the early sown plots and those treated with pirimicarb, however, did allow some recolonisation, and thus led to increased virus incidence and decreased yields. Sprays applied before the end of the migration of S. avenae were more efficient at controlling BYDV if the insecticide was persistent, otherwise a spray after this period, in November, was more effective. Virus incidence, although reduced by sprays, was generally low in plots sown on 18 and 27 September. In contrast, about 11% of plants were infected in unsprayed plots sown on 6 September and a small yield benefit was obtained with insecticidal treatments. Enzyme-linked immunosorbent assay (ELISA) of plants taken from the plots indicated that MAV- and PAV-like strains were present, and were most likely to have been transmitted by S. avenae.     

Chemical control of frit fly on winter cereals sown after grass

From 1978 - 1985, 14 trials were conducted, mainly in Northern England, to assess the efficacy of different insecticides, formulations and application times for the control of frit fly (Oscinella frit) on winter cereals (13 on winter wheat and one on winter barley). Treatments were compared by assessing shoot damage in December-January, numbers of healthy tillers in April and harvested yield. A chlorpyrifos spray to the grass before ploughing or at crop emergence gave the most consistently good results, significantly reducing damage and increasing yield by 0·61 and 0·31 t/ha respectively when taken over all trials. Sprays or granules of other insecticides applied from before drilling to 8 wk after emergence gave variable but sometimes good control and enhanced yield. Chlorpyrifos applied from crop emergence to 8 wk after emergence was generally more effective than other insecticides. Cypermethrin at emergence or 2wk later gave promising results in the two trials where it was used. Of the seed treatments fonofos was the most effective though it did not match the spray treatments. In additional trials, where insecticides were applied after damage occurred, sprays of chlorpyrifos and pirimphos-methyl reduced damage and increased yield.     

The effects of fungicide benomyl (benlate) on growth and mitosis in onion (Allium cepa L.) root apical meristem

In this study, the effects of benomyl, a systemic fungicide were investigated in the mitotic cell division in onion (Allium cepa) root tip cells during germination. For this aim, different concentrations (1, 2, 5, 10 and 20 mM) of benomyl solutions were used. All the concentrations used caused several abnormalities in mitotic cell divisions and the mitotic frequency in the onion root tip cells decreased as the concentration of benomyl solution increased. Based on our findings, it is reported that benomyl has some negative effects on mitotic divisions in onion root tip cells.     

Benomyl tolerance in isolates of Botrytis cinerea from tomato plants

Three hundred and forty-nine isolates of Botrytis cinerea were collected from tomato crops on forty-one nurseries and 173 (40/6 %) were found to be tolerant to benomyl. There was no obvious association between disease incidence and the occurrence of tolerance. In a fungicide comparison experiment on tomatoes in 1973, twenty of the sixty-four (31 %) isolates examined were benomyl tolerant, the majority of these were from benomyl sprayed plants. In 1974 in a similar experiment, 384 of the 394 (97-5 %) isolates examined were tolerant. Tolerance was monitored in two tomato experiments in relation to a spray programme in which benomyl and dichlofluanid were used in various combinations. There was no marked effect of the spray programmes on the incidence of tolerance on either site. In the experiments B. cinerea was controlled and significant increases in yield were obtained with benomyl in 1973 but not in 1974. This difference is attributed to the change in the pathogen population with a large increase in the incidence of tolerance on the experimental site in 1974.     

Disease measurement in a study of apple scab epidemics

The growth and yield increases in red raspberry which followed the repeated application of benomyl were not due to the suppression of pests. Benomyl had little effect on numbers of aphids and nematodes which, anyway, were insufficiently abundant to cause damage. Benomyl did, however, decrease the earthworm population. In the following years, when benomyl was no longer applied, significantly more canes died from midge blight in the plots treated most frequently with benomyl than in the untreated. This was probably a consequence of increased infestation by larvae of the raspberry cane midge (Resseliella theobaldi) in the benomyl-treated plots because benomyl increased the extent of cane splitting and hence the number of egg-laying sites for cane midge.     

The effect of benomyl on growth and ultrastructure of two isolates of Phytophthora infestans from Egypt

The effect of benomyl as a fungicide on the growth rate and ultrastructure of two isolates (P1319 and P623) of Phytophthora infestans is compared. Benomyl caused a concentration-dependent inhibition of the mycelial growth of both isolates. The isolate P1319 was found to be more sensitive to benomyl than the isolate P623. Ultarstructural studies confirmed these observations. The hyphae of isolate P1319 subjected to 100 and 500 ppm benomyl showed more severe changes in the cytoplasm than those of isolate P623. An increase in lipid bodies and vacuoles in the hyphal cytoplasm was the characteristic phenomenon after treatment with benomyl, particularly at a concentration of 500 ppm.