Effects of fungicide residues on the survival, fecundity, and predation of the mites Tetranychus urticae (Acari: Tetranychidae) and Galendromus occidentalis (Acari: Phytoseiidae)

Representative fungicides from three or four families used for management of powdery mildew and other diseases in tree fruits were evaluated for their effects on a common spider mite and predator mite species, respectively. A modified Munger cell technique was effective in measuring the response of phytophagous and predaceous mites to fungicide residues on detached leaves in the laboratory. Demethylation-inhibiting (DMI) (imidazole [triflumazole] and triazole [myclobutanil]) and strobilurin (trifloxystrobin) fungicides were not toxic to female Tetranychus urticae Koch and Galendromus occidentalis (Nesbitt), and no sublethal effects were found on fecundity and predation rate after 3-5-d exposure to residues. Benomyl, a benzimidazole fungicide, increased adult mortality and reduced fecundity for both mite species; however, it did not alter the predation rate of G. occidentalis females on T. urticae eggs and larvae. Female G. occidentalis that survived the lethal effects of benomyl and the comparison acaricide pyridaben were unimpaired in predation. Our results for benomyl substantiate those of earlier studies and provide evidence for nontoxic effects of DMI and strobilurin fungicides on mites. We propose that DMI and strobilurin fungicides are a good fit for integrated mite management programs due to conservation of phytoseiid predatory mites.     

Application of iprodione by thermal fogging for the control of grey mould of tomato

A ready-to-fog' formulation of iprodione applied with themal foging equipment was a satisfactory alternative to high-volume (HV) sparys of iprodione for the control ofnatural infecton with grey mould (Botrytis cinerea) in an unheated tomato crop. There were no significant differences in numbers of droped fruit nor in the control of naturally-occurring lesions in stems or leaves, nor of ghost-spotting on fruit, between the HV sprays and fogs applied every fortnight. Except for ghost-spotting, control by fogs applied weekly was better than by eihter for nightly treatment. In contrast, the control of infection from B.cinerea inoculations on peitoles was significantly better by the fortnightly HV treatment than by either frequency of foging. Control of infection imporved with increase in the number of fungicide applications to the peitole before inoculation; two HV sprays gave complete control but six fog applications did not. The variation in the conrrol of infection by fogs and presumbly therefore in the distribution of fungicide within the 61 m² glasshouse compartments was small. Application of the iprodione fogging formulation significantly reduced the number of fruits see by about 5% compared with the HV treatment.     

Use of potassium bicarbonate (Armicarb) on the control of powdery mildew (Sphaerotheca mors-uvae) of gooseberry (Ribes uva-crispa)

Powdery mildew (Sphaerotheca mors-uvae) severely infects young shoots, stems and fruits of gooseberry (Ribes uva-crispa). Environmental friendly and biological control measures are being sought throughout the world. Especially in organic gooseberry growing effective control measures are needed, because powdery mildew infections may result in a total loss of the crop. In organic currant growing the number of adequate control methods is very limited. Sulphur as a fungicide against powdery mildew in e.g. gooseberry or table grape growing is not recommendable due to possible bleaching of berries and scorching of tender shoots. Various bicarbonate salts are suggested as a good option to control powdery mildew. In a field trial the effect of potassium bicarbonate (Armicarb) on the on the control of powdery mildew of gooseberry was evaluated. Four treatments; i.e. two preventive strategies and two curative strategies, were applied. PLants were sprayed until runoff. The percent of infected fruits and disease severity were assessed. In the unsprayed control plots very high disease incidences were observed; on average more than 90% of the berries were infected with powdery mildew. The weekly (preventive) spray applications with potassium carbonate reduced the disease incidences on fruits significantly. On average approximately 10% of the fruits were affected by powdery mildew. However, the number of spray applications was high. In conclusion, our results indicate that applications of potassium bicarbonate (as Armicarb) are effective in reducing the incidence and severity of American powdery mildew in gooseberry. Early spray applications are necessary to protect berries against powdery mildew infections. Future research will focus on reducing the number of applications, e.g. warning models based on powdery mildew of rose (Sphaerotheca pannosa).     

Micronised and non-micronised sulphur applications control peach scab equally well with negligible differences in fruit quality

In a 2-year study, micronised (finely ground) and non-micronised sulphur spray programmes were investigated for peach scab control and influence on peach fruit quality variables including fruit colouration, soluble solids content and flesh firmness. Both sulphur programmes, applied six or 11 times at 15 kg ha⁻¹, controlled scab equally well in both years on cultivars (cvs) Contender and Cresthaven. Six applications of a half dosage of both micronised and non-micronised sulphur programmes were significantly less effective ( P  < 0.05) compared with all other programmes when scab incidence was >90% on cv. Contender. None of the sulphur programmes influenced significantly ( P  < 0.05) colouration and flesh firmness of harvested fruits compared with the industry standard (a chlorothalonil–captan programme). Only soluble solids concentrations showed significant differences among fungicide programmes ( P  < 0.05), but these differences were not consistent with either particle sizes of sulphur fungicide or reduced application fungicide programmes. In conclusion, our study showed that (a) micronised sulphur did not control peach scab more effectively compared to non-micronised sulphur; (b) six applications of sulphur were sufficient to control peach scab when disease pressure was low to medium; and (c) neither six nor 11 applications of sulphur-based products applied at 15 kg ha⁻¹ had commercially relevant negative impacts on important peach fruit quality variables.     

Patulin accumulation in apples by Penicillium expansum during postharvest stages

AIMS: The aim of this study was to assess the opportunities of Penicillium expansum to develop and produce patulin in apples during cold storage and in the steps prior to processing of apple products. METHODS AND RESULTS: Two lots of apples var. Golden with different ripeness degree were used. Half of each lot was fungicide treated. Apples were inoculated with P. expansum and stored at 1 degrees C for 6 weeks. The extent of lesions and patulin accumulation both at the end of cold storage and after 3 days at 20 degrees C were assessed. Short storage at 20 degrees C aimed to simulate the transport and storage steps at room temperature before processing. Lesion size significantly increased during the storage at 20 degrees C. An interaction between fungicide treatment and ripeness degree was found; efficiency of fungicide treatment was higher for ripe apples. Although lesions were evident after cold storage, no patulin was detected. Patulin was detected only when fruits were further stored at 20 degrees C. Neither ripeness degree nor fungicide treatment affected patulin accumulation. CONCLUSIONS: Cold storage periods of 6 weeks do not lead to patulin accumulation. SIGNIFICANCE AND IMPACT OF THE STUDY: Shortening preprocessing times at warm temperatures would result into a reduction in patulin content at initial steps of fruits entering the processing plants.     

Influence of selenium on the efficiency of fungicide action against certain fungi

Aspergillus funiculosus was isolated from rotted banana fruits, whereas Alternaria tenuis and Fusarium sp. were isolated from rotted tomato fruits. The isolated fungi tolerated relatively high levels of the fungicide, Dithane, up to 2560 ppm on solid medium, but grew well at 40 ppm when supplemented with liquid medium. They are able to tolerate selenite up to 2% (w/v) sodium selenite. A. funiculosus showed no growth in the presence of mixture of 2.5 ppm selenium and 20 ppm Dithane, whereas Fusarium sp. failed to grow at 2.5 ppm selenium and 10 ppm Dithane, or at 10 ppm of each. Nevertheless, Alternaria tenuis is more tolerant; it showed growth in the presence of relatively high levels of selenium and Dithane; up to 10 ppm selenium and 40 ppm Dithane, however, its growth was inhibited by the presence of a mixture of both. The results suggested new form of highly active fungicides. Selenium as an essential nutrient at such very low concentrations, as well as the application of very low concentrations of the fungicide, would certainly reduce the hazardous effect of such pollutant in the environment.     

Effects of foliar applications of fungicides during plant growth on grain development and grain germinability in spring barley

In 1990 and 1991 grain samples of spring barley were obtained from plots in which fungal diseases were controlled until ear emergence using fungicide sprays, and from comparable plots which had received no fungicide applications. The grain was stored at 10^oC, and tested for germination at intervals during storage. Grain from plots treated with fungicide consistently exhibited more dormancy than grain from untreated plots. In 1992, grain development was monitored from anthesis to harvest-ripeness in treated and untreated plots of cvs Blenheim, Camargue and Tyne. In cvs Blenheim and Camargue, grains in fungicide-treated plots had a greater dry weight at harvest-ripeness, and dehydrated later in development than grains in untreated plots. Neither of these differences was observed in cv. Tyne. Possible interpretations of the effects of fungicide treatment of the parent plant on the physiology of the grain are discussed.     

Integrating cultural control methods for tomato late blight (Phytophthora infestans) in Uganda

Cultural control measures against tomato late blight (Phytophthora infestans) were evaluated in six field experiments over 3 years in Uganda. Each experiment included sanitation (removal of diseased plant tissues), fungicide (mancozeb) application, and an untreated control, as standard treatments. Late blight incidence and severity were greatly reduced by sanitation, without reducing the number of healthy leaves; however, tomato growth and production were adversely affected. Fungicide treated plants retained the highest numbers of flowers and attached fruits and gave the highest yields. Three cultural practices were evaluated in repeated experiments for their effectiveness in alleviating the adverse effects of sanitation. Tomatoes grown within plastic shelters early in the production cycle were taller, and had more healthy leaves than those grown late. The numbers of diseased leaves and disease severity were equally low in sanitation alone and plastic shelter/with sanitation treatments. Flower and fruit production were significantly higher when tomatoes were grown under early shelters with sanitation than with sanitation alone. Planting density was increased without significant effects on late blight and tomato growth and production. Intercropping tomato with soybean (Glycine max) or sesame (Sesamum indicum), with sanitation, limited late blight development, but taller intercrops suppressed tomato growth and production. Integrated treatments (combining plastic shelters, a sesame intercrop and high tomato planting density) were evaluated, with and without sanitation, against the fungicide mancozeb. The mean numbers of healthy leaves in the integrated treatments were not significantly less than with fungicide treatment. Late blight incidence and severity were higher in the integrated plots without than with sanitation. The numbers of flowers and attached fruits were not significantly less in integrated treatments than in fungicide treated plots, but tomato yield was highest with fungicide treatment.     

The effect of pyrimethanil on the growth of wine yeasts

Aims:  The toxicity of the fungicide pyrimethanil on the growth of wine yeasts was evaluated using in vivo and in vitro experimentation.
Methods and Results:  The effect of pyrimethanil in the must was studied during the spontaneous wine fermentation of three consecutive vintages and by the cultivation of Hanseniaspora uvarum and Saccharomyces cerevisiae yeasts in a liquid medium. The residues of the fungicide were measured using gas chromatography-mass spectrometry system and the sugar concentration in the must using HPLC-RI. Molecular and standard methods were used for identifying the yeast species. Although the pyrimethanil residues in grapes were below the maximum residue limits, they significantly affected the reduced utilization of sugars in the first days of fermentation. Its residues controlled the growth of H. uvarum during the fermentation and during in vitro cultivation as well.
Conclusions:  The fungicide pyrimethanil had an effect on the course and successful conclusion of spontaneous wine fermentation that was correlated with the initial concentration of yeasts in the must.
Significance and Impact of the Study:  The impact of pyrimethanil on the indigenous mixed yeast flora in fermenting must was investigated for the first time. The results showed that its residues might play an important role in the growth and succession of yeast during spontaneous wine fermentation.     

Effect of AM symbiosis exclusion on grassland community composition

Experimental data on grassland community response to exclusion of arbuscular mycorrhizal (AM) symbiosis using fungicide benomyl and to phosphate addition were evaluated after four years of continued manipulation using multivariate direct gradient analysis. While the community responded only to phosphate application in the third year (phosphate application suppressing forbs in favour of graminoids), the data from the fourth season indicate relative suppression of some forbs (includingPlantago lanceolata, Cerastium holosteoides) with both phosphate and fungicide applications. Positive response of graminoids to phosphate addition seems to interact with fungicide application, while an important community constituent —Achillea millefolium — seems to profit primarily from fungicide applications. The effect of the fungicide on the AM symbiosis was confirmed on roots ofPlantago lanceolata. The direct evaluation of frequency of AM fungal structures in plant roots also revealed a diverse response of different plant species to phosphate application. Nevertheless, in all species (except non-mycorrhizalLuzula campestris), phosphate decreased the frequency of arbuscules and increased the frequency of non-infected root segments.     

Effects of some fungicides used against cereal pathogens on the growth of Rhizobium trifolii and its capacity to fix nitrogen in white clover

Fungicide residues in soils may affect nitrogen fixation by legumes. Effects of nine systemic fungicides, used against cereal pathogens, on Rhizobium trifolii and white clover were measured. Fenarimol and oxycarboxin inhibited growth of R. trifolii in vitro. The weight of clover plants after 10 weeks' growth in soil containing carboxin, oxycarboxin, benodanil, tridemorph and pyracarbolid was reduced. Symbiotic nitrogen fixation was decreased by carboxin, oxycarboxin and tridemorph present in soil at concentrations somewhat greater than that likely to result from several applications of the fungicide. Only tridemorph reduced nodulation. None of the compounds seems likely to affect nitrogen fixation in the field if applied at the recommended rate.     

Effectiveness of SIMBLIGHT1 and SIMPHYT1 models for predicting Phytophthora infestans in north-eastern United States

Accurate prediction of Phytophthora infestans outbreak in a cropping season is crucial for the effective management of late blight on potato. The SIMBLIGHT1, SIMPHYT1 and modified SIMPHYT1 models were assessed for predicting late blight outbreaks relative to NOBLIGHT model by using climatic and crop data from field experiments at Presque Isle, ME, from 2004 to 2009. The dynamics of late blight infection pressures were computed by SIMPHYT3 model to assess the conduciveness of environmental conditions for late blight infection and potential for disease development. Infection pressure indicated conditions were moderately conducive for late blight development but varied across years. The SIMPHYT1 model recommended fungicide applications to commence on 11 July, 21 July, 8 July, 10 July, 7 July and 7 July for 2004, 2005, 2006, 2007, 2008 and 2009, respectively. The modified SIMPHYT1 model (US-version) recommended similar fungicide application dates for the same years with the exception of 2007. Model simulations of disease outbreak differed from actual recorded observations in untreated plots by 24–65 days. Simulation of SIMBLIGHT1 based on high and low soil moisture conditions in the field resulted in vast differences in dates of first fungicide application. Validation of the models (differences in the number of days between recommendation of fungicide treatment and late blight outbreak) indicated a better goodness of fit for the models (intervals of 6–20 days from the start of fungicide application to first disease outbreak). The NOBLIGHT model was accurate in forecasting the timing of first fungicide applications for late blight control. Significant improvements in late blight predictions could result if these models were modified to account for external sources of inoculum, by combining weather-based forecasts with spore traps, disease detection methods or complimentary systems.     

Optimization of Solutions for the One Plant Protection Problem

Plant protection problems are simulated by a system of ordinary differential equations with given initial conditions. The sensitivity and resistance of pathogen subpopulations to fungicide mixtures, fungicide weathering, plant growth, etc. are taken into consideration. The system of equations is solved numerically for each set of initial conditions and parameters of the disease and fungicide applications. Optimization algorithms were investigated and a computer program was developed for optimization of these solutions. 14 typical cases of the disease were simulated and optimized in order to determine optimal fungicide treatments. The optimized strategy for fungicide application differs considerably from the commonly used method and seems to be an important new principle in plant protection. The approach developed in this study may be useful for a wide spectrum of purposes in the simulation of leaf diseases. It may also help the biologist to decrease or pinpoint experimental work and analyze its results and is perspective for plant disease control.     

A method for pre-harvest assessment of latent infections in fruits

A method was developed for the assessment of latent infections of Alternaria alternata in mango fruits. Fruit discs were sampled and assayed for fungal contamination under suitable growth conditions. By this method it was possible to evaluate the percentage of infections and the relative surface infected by Alternaria in mango fruits before harvest. The percentage of infections increased during the growing season but fungicide treatments prevented this increase. A significant positive correlation was found between the relative surface infected by latent Alternaria at harvest time and the incidence of black spots that developed on the fruit during storage.     

Determination of heavy metals in the fruit of date palm growing at different locations of Riyadh

Exposure of heavy metals to human beings has risen dramatically in the last 50 years. In today’s urban and industrial society, there is no escaping from exposure to toxic chemicals and heavy metals. Humans are more likely to be exposed to heavy metal contamination from the dust that adheres to edible plants than from bioaccumulation. This is because it is very difficult to wash off all the dust particles from the plant material before ingesting them. The objectives of this experiment were to determine the concentrations of lead (Pb) and cadmium (Cd) in washing residues and in the tissues of fruits of date palm growing in 14 sites of Riyadh and also to assess whether the fruits were safe for human consumption. The washing residues and tissue of date palm fruits collected from different sites showed the presence of significant amounts of the Pb and Cd. The concentration of Pb in the dust and fruit tissue increased with increasing anthropogenic sources. Therefore, fruits of date palm might be used as a pollution indicator; it might be recommend that fruits of date palm could be safe for human consumption after washing. The mean concentration of Pb and Cd in all the samples collected from different sites is within the safe limits recommended by FAO/WHO.     

Effects of Trichosporon sp. in Combination with Calcium and Fungicide on Biocontrol of Postharvest Diseases in Apple Fruits

The capability of yeast Trichosporon sp., an antagonist isolated from peach fruit, in biological control was evaluated in apple ( Malus domestica Borkh. cv. Fuji) fruits, when inoculated with different concentrations of Botrytis cinerea Pers. and Penicillium expansum (Link) Thom, as well as in combination with calcium and fungicide. The concentrations of the yeast cells and pathogen spores obviously influenced disease incidence and lesion development in apples. There was a significant negative correlation between concentrations of the yeast cells and infectivity of the pathogens. When the yeast cell suspensions reached the concentration of 108 colony-forming units (CFU)/mL, there was no infection caused by B. cinerea and P. expansum with spore concentrations below 106 spores/mL in apple fruits. The yeast at concentrations of 106-107 CFU/mL in combination with fungicide (iprodione at 50 μL/L) provided control of decay caused by B. cinerea and P．expansum better than separate application. Effect of controlling gray mould and blue mould rots was enhanced when Trichosporon sp., even at low concentration of 105 CFU/mL, was applied in the presence of 1%-2% CaCl2 in an aqueous suspension.     

Removal of pesticides from white wine by the use of fining agents and filtration

The effects of four clarification agents (bentonite, charcoal, PVPP and potassium caseinate) on the removal of residues of three fungicides (famoxadone, fluquinconazole and trifloxystrobin) applied directly to a racked white wine, elaborated from Airen variety grapes from the D.O. Region of Jumilla (Murcia, Spain) are studied. The clarified wines were filtered with 0.45 microm nylon filters to determine the influence of this winemaking process in the disappearance of fungicide residues. Hydro-alcoholic solutions with the three fungicides at concentrations of 1 and 2 ppm were then added through intense stirring to each of the containers. Two hours later, the corresponding clarifying agent was added with intense stirring for some minutes. The containers were then sealed and left to settle for five days. Once the clean wines had been racked, they were filtered through nylon 0.45 microm pore filters. All assays were performed three times. Analytical determination of fluquinconazole and trifloxystrobin was performed by gas chromatography with an electron captor detector (ECD), while that of famoxadone was made using an HPLC-DAD. For the three fungicides, the highest elimination is produced with the clarification by charcoal, reaching Levels of removal of 100% in all cases. For the four clarifying agents, the highest elimination is produced for the fluquinconazole residues. The fungicide which is retained most in the lees is famoxadone, since it has the lowest solubility of the three pesticides studied. The highest percentage of residues in the lees is obtained for the assay with charcoal. The filtration process of the clarified wines using the four agents studied is not effective, since the elimination percentage is generally lower than 10% of the initial residues in the non-clarified wines.     

Induction of Systemic Resistance by Bacillus cereus Against Tomato Foliar Diseases Under Field Conditions

The ability of a rhizobacterium to protect tomato plants against naturally occurring diseases as well as to improve crop yield under field conditions was studied. The rhizobacterium was introduced to the plants through seed microbiolization. Treatments consisted of different frequencies of fungicide (Chlorothalonyl) sprayings (5, 10 or 20 applications) of tomato plants grown from either microbiolized or non‐microbiolized seeds over a 90‐day evaluation period. Treatment of non‐microbiolized seeds without fungicide application was included as a control. The progress of the following three naturally occurring diseases was evaluated in the field and quantified: early blight (Alternaria solani), late blight (Phytophthora infestans), and septoria leaf spot (Septoria lycopersici). All treatments resulted in reduced disease severity when compared with the control treatment. Highest final fruit yields were found after treatment of plants grown from non‐microbiolized seeds and sprayed with fungicide 20 times over 90 days, and for treatment of plants from microbiolized seeds that received 10 fungicide spray applications, although all treatments increased yield over that obtained in the control treatment. The results demonstrate that combined rhizobacterial and chemical treatments in the field may permit reducing fungicidal spraying frequency while at the same time increasing crop yields.     

Effect of timing of application Pseudomonas fluorescens in suppression Sclerotinia sclerotiorum, the causal agent of white mold in canola

Biological control of sclerotinia disease, as an important alternative to chemical control, has received considerable attention due to the lack of resistant varieties in most crop, and increasing concerns over fungicide resistance in population of Sclerotinia sclerotiorum, and fungicide residues in the environment. One biocontrol agent, Pseudomonas fluorescens PB-3, has been showed the antagonistic relationship between itself and S. sclerotiorum was investigated in this study. A petal infection technique was used to detect efficacy of timing of application strain PB-3 in the suppression of S. sclerotiorum on canola. Significant difference in disease severity (p<0.05) were found with respect to timing of ascospore applications in the control treatments (ascospores only). The superior competitive ability strain PB-3 was demonstrated by its complete suppression of disease severity when applied as a co-inoculation treatment or prior to ascospores inoculation. Analysis of effect of applying strain PB-3 after ascospores was indicated that treatment in which strain PB-3 was added to petals 48 or 24 h after ascospores, or when there were no bacteria present at all, had higher rates of disease progression. It would be appear that bacteria are able to significantly inhibit disease when applied before or even at the same time as ascospores. In a practical sense, this could mean that a field application of antagonist could be concurrent with infection by the pathogen.     

Pyrimethanil: Between efficient fungicide against Aspergillus rot on cherry tomato and cytotoxic agent on human cell lines

Pyrimethanil, a synthetic fungicide widely used for the treatment of pre‐ and postharvest fungal diseases on different agricultural crops, was explored for its antifungal activity on different fungal strains. The effect of pyrimethanil on fungal ergosterol was tested by using Aspergillus niger as a model organism. Furthermore, it was investigated, if pyrimethanil can effectively reduce the appearance of Aspergillus rot in wounded cherry tomato fruits. The fungicide cytotoxic effect on different human cell lines was evaluated. In addition, its influence on cell proliferation was studied. A. niger was the most resistant fungal strain (MFC 1.88 μg μL^?1) to the effect of pyrimethanil. Addition of ergosterol doubled the MFC on A. niger, indicating that the compound might interfere with ergosterol, main sterol of fungal cell membrane. Disease incidence of A. niger in wounded cherry tomato fruits was not detected with pyrimethanil treatment of 0.75 mg/wound. Some cytotoxic effects of pyrimethanil on human cell lines were recorded already at 50 ng μL^?1, while the expression of Ki67 marker of proliferation was decreased with 150 ng μL^?1. These results altogether indicate that pyrimethanil is effective in reducing various fungal pathogens, but further use of this fungicide should be reevaluated because of its cytotoxicity.