Fate of epoxiconazole and kresoxim-methyl in wheat according to time of application

During the 2000-2001 season a field trial was conducted with the aim of quantifying the distribution and persistence of epoxiconazole and kresoxlm-methyl in the different leaf layers of winter wheat plants. In the case of applications before flag leaf emergence, the redistribution of the two active ingredients in the newly formed leaves following the applications was also measured. Allegro (125 g/L epoxiconazole and 125 g/L kresoxim-methyl, SC) was applied at the manufacturer's recommended rate (1 L/ha) either in a single treatment at stages GS32, GS39 and GS59 or in 2, 3 or 4 split applications. Following spraying, leaf samples were collected over time, from each leaf layer, and the two active ingredients were quantified by gas chromatography with electron capture detection (GC-ECD). Fungicide distribution varies according to time of application. A descending gradient through the leaves was observed in the case of application at GS59. When sprayed at stage GS39, on the other hand, the second leaf intercepted more fungicide than the flag leaf. Kresoxim-methyl was found to degrade faster than epoxiconazole. With split treatments, the last spraying appears to be very significant in terms of final fungicide quantities. Redistribution appears possible, especially in the case of epoxiconazole, though in very small quantities.     

Effect of Neem and Selected Fungicides on Viability and Virulence of the Entomopathogenic Nematode Steinernema feltiae

Entomopathogenic nematodes are often used in conjunction with other pest management tactics and the lack of compatibility information is a major impediment in further expansion of their use. We evaluated the effects of different formulations of neem and selected fungicides commonly used in greenhouses on Steinernema feltiae which is used for the control of fungus gnats. Neem as pure oil at the field recommended concentrations (5- 10 mL L -1 ) had no effect on the viability and virulence of S. feltiae up to 120 h incubation. However the neem formulation, Nimbecidine and neem oil when mixed with a bactericidal soap (commonly used as a surfactant with neem oil) caused 13- 25% mortality of S. feltiae. This toxic effect was entirely due to the soap that alone caused about 24% mortality. Neither neem oil, Nimbecidine or soap had any effect on nematode virulence. The fungicide cinnamaldehyde (Cinnamate) was highly toxic, resulting in 100% nematode mortality after 4 h of incubation, followed by hydrogen dioxide/peroxyacetic acid mixture (ZeroTol) that caused 100% mortality after 120 h of incubation. Another fungicide, azoxystrobin (Abound) caused no nematode mortality. This investigation concludes that neem and the fungicide azoxystrobin (Abound) can be safely tank mixed at the field recommended concentrations with the infective juveniles of S. feltiae for application, but cinnamaldehyde (Cinnamate) and hydrogen dioxide/peroxyacetic mixture (ZeroTol), are incompatible. Also the surfactants that are usually recommended as 'tank-mix' applications can be toxic to the nematodes and should therefore be evaluated for compatibility prior to use.     

Integrated control of fruit rot and powdery mildew of chilli using the biocontrol agent Pseudomonas fluorescens and a chemical fungicide

A combined strategy of chilli fruit rot and powdery mildew control consisting of reduced fungicide dose and biological control with antagonistic Pseudomonas fluorescens (Pf1) was evaluated. The sensitivity of P. fluorescens to fungicide azoxystrobin at different concentrations (100, 150, 200, 250 and 300 ppm) was tested by turbidometric method. The grown bacterium (Pf1) was tolerant to all concentrations of azoxystrobin. In two field trials, Pf1 tested in combination with reduced concentration of azoxystrobin was highly efficient in management of both diseases of chilli. Biological control of Colletotrichum capsici and Leveillula taurica with P. fluorescens (Pf1) was effective but less so than fungicide alone at the standard dose. However, combination of the biological control agent with a 50% reduction of fungicide dose was as effective as the standard fungicide alone. Application of P. fluorescens along with azoxystrobin significantly increased the survival of Pf1 in the phylloplane of chilli. Further, there were ‘twofold’ increases in activities of peroxidase, polyphenol oxidase, phenylalanine ammonia-lyase, β-1,3-glucanase, chitinase and phenolics in plants treated with Pf1 plus azoxystrobin.     

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.     

Impact of recently emerged sterol 14{alpha}-demethylase (CYP51) variants of Mycosphaerella graminicola on azole fungicide sensitivity

The progressive decline in the effectiveness of some azole fungicides in controlling Mycosphaerella graminicola, causal agent of the damaging Septoria leaf blotch disease of wheat, has been correlated with the selection and spread in the pathogen population of specific mutations in the M. graminicola CYP51 (MgCYP51) gene encoding the azole target sterol 14α-demethylase. Recent studies have suggested that the emergence of novel MgCYP51 variants, often harboring substitution S524T, has contributed to a decrease in the efficacy of prothioconazole and epoxiconazole, the two currently most effective azole fungicides against M. graminicola. In this study, we establish which amino acid alterations in novel MgCYP51 variants have the greatest impact on azole sensitivity and protein function. We introduced individual and combinations of identified alterations by site-directed mutagenesis and functionally determined their impact on azole sensitivity by expression in a Saccharomyces cerevisiae mutant YUG37::erg11 carrying a regulatable promoter controlling native CYP51 expression. We demonstrate that substitution S524T confers decreased sensitivity to all azoles when introduced alone or in combination with Y461S. In addition, S524T restores the function in S. cerevisiae of MgCYP51 variants carrying the otherwise lethal alterations Y137F and V136A. Sensitivity tests of S. cerevisiae transformants expressing recently emerged MgCYP51 variants carrying combinations of alterations D134G, V136A, Y461S, and S524T reveal a substantial impact on sensitivity to the currently most widely used azoles, including epoxiconazole and prothioconazole. Finally, we exploit a recently developed model of the MgCYP51 protein to predict that the substantial structural changes caused by these novel combinations reduce azole interactions with critical residues in the binding cavity, thereby causing resistance.     

Azoxystrobin and soil interactions: degradation and impact on soil bacterial and fungal communities

Aims: To provide an independent assessment of azoxystrobin effects on nontarget soil bacteria and fungi and generate some baseline information on azoxystrobin’s persistence in soil. Methods and Results: Plate based assay showed that azoxystrobin exhibited differential toxicity upon cultured fungi at different application rates. While ¹⁴C labelled isotopes experiments showed that less than 1% of azoxystrobin was mineralized, degradation studies revealed over 60% azoxystrobin breakdown over 21 days. PCR DGGE analysis of 16S and 18S rRNA genes from different soil microcosms showed that azoxystrobin had some effects on fungal community after 21 days (up to 84 days) of incubation in either light or dark soil microcosms. Light incubations increased fungal diversity while dark incubations reduced fungal diversity. Bacterial diversity was unaffected. Conclusions: Significant biotic breakdown of parent azoxystrobin occurred within 21 days even in the absence of light. Azoxystrobin under certain conditions can reduce fungal soil diversity. Significance and Impact of the Study: One of the few independent assessments of azoxystrobin (a widely used strobilurins fungicide) effects on soil fungi when used at the recommended rate. Azoxystrobin and metabolites may persist after 21 days and affect soil fungi.     

Prenatal epoxiconazole exposure effects on rat postnatal development

Although some studies have pointed out to embryo/fetal toxicity, knowledge about the potential toxicity of the fungicide epoxiconazole is still limited. Once the results of these previous studies have raised some concern, this study studied the effects of epoxiconazole maternal exposure on the physical endpoints in the development of rat pups. To accomplish that, the effects of epoxiconazole (50.0, 100.0, and 150.0 mg/kg) were examined when rats were exposed at two different developmental stages: during the first 6 days of pregnancy or in the organogenesis period (6-15 days). After parturition, pups were tested for growth and maturational milestones. Maternal exposure to the fungicide, independently of phase, resulted in significantly early mean time to vaginal opening and delayed time to testes descent in pups. Weight gain rate in pups and their mothers was not affected for the tested exposure period. The findings of this study emphasize that epoxiconazole maternal exposure may lead to alterations in developmental patterns in nursing pups, consistent with the known influence of epoxiconazole on steroid hormone synthesis.     

The biological evaluation of Zato 50 WG in protection of carrot against Alternaria blight

Effectiveness of new fungicide Zato 50 WG (biologically active substances BAS - trifloxystrobin 50%) in the control of Alternaria blight on carrot was studied. Field experiments were carried out in the years 2003-2004 on carrot cv. Koral. As the standard fungicide Amistar 250 SC (BAS - azoxystrobin 250 g/dm3) was used. The results of health status of carrot leaves analysis in first and second year of experiment showed, that development of disease symptoms was lower on leaves of chemical protected plants than on leaves of control plants. The last estimation of infestation degree of carrot leaves made immediately before harvest showed, that standard fungicide Amistar had longer systemic influence on plants. This was confirmed the lower (statistically significant) infestation index of protected carrot in combination with Amistar. The estimations of health status of carrot roots were made directly after digging up indicate, that there wasn't difference of value of infestation index between protected combination and control. Experiment showed, significant effect of tested fungicides on crop quantity of carrot roots per 1 m2. Especially in the second year of study the crop of carrot roots in combination with Zato was higher - statistically significant - than in the rest combinations.     

Evaluation of Bacillus mycoides isolate BmJ and B. mojavensis isolate 203-7 for the control of anthracnose of cucurbits caused by Glomerella cingulata var. orbiculare

Bacillus mycoides isolate BmJ (BmJ) and Bacillus mojavensis isolate 203-7 (203-7) were tested in the greenhouse for their ability to control Glomerella cingulata var. orbiculare the causal agent of anthracnose of cucumber by induced systemic acquired resistance (SAR). BmJ and 203-7 delayed disease onset and reduced total (43% and 56%) and live spore production (38% and 49%) per mm² of lesion area when used to induce SAR in cucumber. 203-7 also reduced lesion diameter. Induction by G. cingulata conidia resulted in delayed disease onset, reduction of number of lesions per leaf and lesion diameter. Assays of cucumber apoplastic proteins extracted 6 days after induction showed that BmJ increased β-glucanase activity by 135%, and 203-7 increased β-glucanase activity by 72% and peroxidase activity by 79% when compared to the water control. Acibenzolar-S-methyl induced the highest (P = 0.05) levels of chitinase (950%) and peroxidase (420%) activity compared to water controls. Field experiments (2004 and 2005) evaluated applications of BmJ and fungicides for the control of anthracnose in cucumber (var. ‘General Lee’) and cantaloupe (var. ‘Athena’). BmJ was compared to full and half labeled rate alternate applications of azoxystrobin and chlorothalonil, and BmJ with half rate of azoxystrobin and chlorothalonil. BmJ applied seven days before inoculation reduced disease severity by 41% in cucumber in 2004 and by 24–21% in cantaloupe for both years compared to water controls which was statistically equal to the fungicide treatments. The full and half rate fungicide program provided 97–37% disease reduction compared to water controls. BmJ applied one week before inoculation significantly reduced AUDPC (P = 0.05) in cucumber compared to the water control in 2004 on cantaloupe for both years while the full and half rate fungicide program were equivalent and provided the lowest AUDPC. No yield reduction was noted as a result of the disease or treatment for either cantaloupe or cucumber.     

Signum, a new fungicide for control of leaf diseases in outdoor vegetables

During three years, the new fungicide Signum, containing 6.7% pyraclostrobine + 26.7 % boscalid and developed by BASF. has been evaluated in leek, carrots and cabbages in several outdoor field experiments under practical conditions and during one year in outdoor lettuce. In leek, Phytophthora porri is one of the major leaf diseases causing lesions on differ ent places on the leaves, resulting in at least extra labour costs for trimming or even worse sometimes resulting in complete crop loss. So far, crop protection consists of repeated applications of fungicides especially during autumn and winter. Pyraclostrobin + boscalid has been evaluated in comparison with the fungicides mancozeb, mancozeb + metalaxyl-M and azoxystrobin. The progress of the disease during the growth season is discussed. For all parameters evaluated, pyraclostrobin + boscalid gave comparable or even better results than reference products. Especially during 2003, a small drop of the activity of benalaxyl against P. porri has been observed after repeated applications. In carrots, Erisiphe heraclei and Alternaria dauci are both the most common leaf diseases causing yield and quality loss. During periods of very high pressure of A. dauci, pyraclostrobin + boscalid, applied in a three weeks interval, revealed a superior activity compared with triazole references or compared with azoxystrobin. Against E. heraclei, a good control but also a clear dose response activity have been observed with pyraclostrobin + boscalid. Yield gain was approximately 30 ton /ha compared wih untreated. In Brussels sprouts, good efficacy was obtained against Mycosphaerella spp., Albugo candida and Alternaria spp. In outdoor lettuce Botrytis cinerea and Sclerotinia sclerotiorum are the most important diseases causing crop damage and reducing the quality of the heads. Pyraclostrobin + boscalid was evaluated in comparison with the standard fungicide iprodione. The plant protection was better with the new fungicide pyraclostrobin + boscalid.     

Mechanism of binding of prothioconazole to Mycosphaerella graminicola CYP51 differs from that of other azole antifungals

Prothioconazole is one of the most important commercially available demethylase inhibitors (DMIs) used to treat Mycosphaerella graminicola infection of wheat, but specific information regarding its mode of action is not available in the scientific literature. Treatment of wild-type M. graminicola (strain IPO323) with 5 μg of epoxiconazole, tebuconazole, triadimenol, or prothioconazole ml(-1) resulted in inhibition of M. graminicola CYP51 (MgCYP51), as evidenced by the accumulation of 14α-methylated sterol substrates (lanosterol and eburicol) and the depletion of ergosterol in azole-treated cells. Successful expression of MgCYP51 in Escherichia coli enabled us to conduct spectrophotometric assays using purified 62-kDa MgCYP51 protein. Antifungal-binding studies revealed that epoxiconazole, tebuconazole, and triadimenol all bound tightly to MgCYP51, producing strong type II difference spectra (peak at 423 to 429 nm and trough at 406 to 409 nm) indicative of the formation of classical low-spin sixth-ligand complexes. Interaction of prothioconazole with MgCYP51 exhibited a novel spectrum with a peak and trough observed at 410 nm and 428 nm, respectively, indicating a different mechanism of inhibition. Prothioconazole bound to MgCYP51 with 840-fold less affinity than epoxiconazole and, unlike epoxiconazole, tebuconazole, and triadimenol, which are noncompetitive inhibitors, prothioconazole was found to be a competitive inhibitor of substrate binding. This represents the first study to validate the effect of prothioconazole on the sterol composition of M. graminicola and the first on the successful heterologous expression of active MgCYP51 protein. The binding affinity studies documented here provide novel insights into the interaction of MgCYP51 with DMIs, especially for the new triazolinethione derivative prothioconazole.     

Baseline Sensitivity of Australian Phoma ligulicola Isolates from Pyrethrum to Azoxystrobin and Difenoconazole

Ray blight caused by Phoma ligulicola is an important disease of pyrethrum in Australia, and successful management relies upon the fungicides, azoxystrobin and difenoconazole. Azoxystrobin and difenoconazole were introduced into pyrethrum production in 2001. The sensitivity of P. ligulicola isolates collected in 2003 to azoxystrobin (n = 56) and difenoconazole (n = 61) was tested. Testing for sensitivity to azoxystrobin and difenoconazole used a conidial germination and mycelial growth assay respectively. For each fungicide, the effective dose required to reduce mycelial growth or conidial germination by 50% (EC₅₀) was determined by probit analysis. The EC₅₀ values ranged from 0.007 to 0.193 μg/ml for azoxystrobin and 0.04 to 13.8 μg/ml for difenoconazole. No evidence was found for cross‐resistance between azoxystrobin and difenoconazole in this baseline population. This information serves as important baseline data for tracking future changes in sensitivities of P. ligulicola to these fungicides.     

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.     

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.     

Effects of foliar sprays of azoxystrobin on take-all in wheat

Average percentages of winter wheat plants with severe take‐all were decreased by up to half by azoxystrobin applied as foliar sprays in four field experiments. Decreased take‐all in three of the experiments was associated with increased grain yield but effects on other diseases may have contributed to these responses. Standard fungicide sprays were ineffective. The effects differed, but not consistently, among different cultivars that were tested in three of the experiments. One, two or three sprays of azoxystrobin or kresoxim‐methyl, in autumn, spring or summer, were tested in the fourth experiment. Unlike azoxystrobin, kresoxim‐methyl had no consistent effects but a smaller amount was applied. Two or three sprays of azoxystrobin were more effective than a single spray but their timing was unimportant. Such control of a root disease by a foliar‐applied fungicide is unusual but may help to explain some of the unexpectedly large yield responses to azoxystrobin that have been reported. This relatively broad‐spectrum fungicide may have the potential to contribute to the practical management of take‐all but further research is needed to determine how best to exploit its effects consistently.     

A novel green analytical procedure for monitoring of azoxystrobin in water samples by a flow injection chemiluminescence method with off‐line ultrasonic treatment

A simple and green flow injection chemiluminescence (FI‐CL) method for determination of the fungicide azoxystrobin was described for the first time. CL signal was generated when azoxystrobin was injected into a mixed stream of luminol and KMnO₄. The CL signal of azoxystrobin could be greatly improved when an off‐line ultrasonic treatment was adopted. Meanwhile, the signal intensity increases with the analyte concentration proportionally. Several variables, such as the ultrasonic parameters, flow rate of reagents, concentrations of sodium hydroxide solution and CL reagents (potassium permanganate, luminol) were investigated, and the optimal CL conditions were obtained. Under optimal conditions, the linear range of 1–100 ng/mL for azoxystrobin was obtained and the detection limit (3σ) was determined as 0.13 ng/mL. The relative standard deviation was 1.5% for 10 consecutive measurements of 20 ng/mL azoxystrobin. The method has been applied to the determination of azoxystrobin residues in water samples. Copyright © 2012 John Wiley & Sons, Ltd.     

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 modification of phytosterol profiles and in vitro photosynthetic electron transport of Galium aparine L. (cleavers) treated with the fungicide, epoxiconazole

Foliar application of the triazole fungicide, epoxiconazole, retarded the growth of Galium aparine L. (cleavers). GC-MS and GC analysis clearly indicated that phytosterol biosynthesis in stem and leaflet tissue was significantly affected by this treatment. For example, in leaflet tissues, 125 g ai ha^-1 (field rate) caused reductions in campesterol and sitosterol of 81percnt; and 75percnt; respectively. C14-methyl phytosterols such as 14agr;-methylergost-8-enol, obtusifoliol and dihydroobtusifoliol were detected in treated tissues indicating that epoxiconazole inhibits the cytochrome P-450 dependent obtusifoliol 14agr;-demethylase. In addition, ratios of campesterol to sitosterol were reduced. Stigmasterol was not detected in control or treated tissues. Preliminary determination of photosynthetic characteristics of isolated thylakoids from treated plants indicated that electron transport and oxygen evolution were impaired by epoxiconazole and these effects were dose-related. Ten days after treatment, oxygen evolution from thylakoids (determined as electron flow from water to ferricyanide) isolated from control plants was 24.2 micro;mol mg^-1 chl h^-1, whilst treatment with 125 g and 250 g ai ha^-1 reduced this rate to 15.2 micro;mol and 8.2 micro;mol mg^-1 chl h^-1 an inhibition of 37 and 67percnt; respectively. These results suggest that epoxiconazole influences thylakoid integrity and function in addition to phytosterol biosynthesis in G. aparine.     

Fungicide sprays can injure the stigmatic surface during receptivity in almond flowers

Fungicides can be detrimental to flower development, pollen function and fruit set in a number of crops. Almond is a self-incompatible nut crop that has a fruit set of only approx. 30 % of the total number of flowers. Thus, interference of pollination and fertilization by fungicide sprays is of concern, and identification of chemicals having the least detrimental effects would be desirable. The objective of this study was to evaluate the effect of fungicide sprays on stigma morphology in almond using a laboratory spray apparatus that simulated field applications. Four fungicides (azoxystrobin, myclobutanil, iprodione and cyprodinil) were applied, and fresh, unfixed stigmatic surfaces were observed using a scanning electron microscope at 4 and 24 h after spraying. Increased exudate accumulation was induced by azoxystrobin at both time periods, and localized damage and collapse of stigmatic cells were observed after 24 h. Damaged stigmatic papillae exhibited wrinkling, surface distortion or collapse. Likewise, myclobutanil caused significant damage to and collapse of papillae; these were more extensive at later observations. Iprodione had no effect on exudate accumulation but caused marked and severe collapse of stigmatic papillae which was pronounced at 24 h. Cyprodinil promoted a copious increase in exudate secretion and caused the most severe collapse of stigmatic cells of all the fungicides evaluated. Damage was somewhat localized at 4 h but more global at 24 h. This study has verified that certain fungicide sprays have direct detrimental effects on stigma morphology and enhance exudate production in almond flowers.