Fungicides Iprodione Research Articles

Application of thymol and iprodione to control garlic white rot (Sclerotium cepivorum) and its effect on soil microbial communities

The effect of different dosages of thymol alone, iprodione alone and combinations of thymol and iprodione on white rot disease of garlic and its impact on soil microbial community structure were investigated under greenhouse conditions. Thymol alone or in combination with the fungicide iprodione did not appear to reduce either white rot incidence or soil sclerotia density as compared to an infected control. However, iprodione alone or in combination with thymol reduced soil fungal biomass. In addition, iprodione alone decreased soil microbial activity as estimated by fluorescein diacetate (FDA). Soil bacterial community structure as estimated by phospholipid fatty acid (PLFA) profiles was also was affected by both thymol and iprodione applications. The correlation biplot of the individual PLFAs and biocide treatment indicated that the treatments with thymol alone increased cyclopropyl fatty acid (cy17:0 and cy19:0), while the treatments with iprodione alone increased some saturated and branched fatty acids (principally i16:0, a15:0 and 18:0). In addition, taking into account PLFA biomarkers, thymol applications reduced Gram-negative bacteria in soil. To our knowledge, this research is the first report about the effect of a monoterpene (thymol) on soil microflora.

Sensitivity to iprodione and boscalid of Sclerotinia sclerotiorum isolates collected from rapeseed in China

Baseline sensitivity of Sclerotinia sclerotiorum, causal agent of stem rot of rapeseed, to a dicarboximide fungicide iprodione was determined using 50 isolates (historic population) collected in 2001 from the rapeseed fields without a previous history of dicarboximide usage. The 50% effective concentration (EC 50) values to iprodione of these wild-type isolates ranged from 0.163 to 0.734 μg/ml with a mean of 0.428 μg/ml. In 2007 and 2008, 111 isolates (current population) were collected from rapeseed fields with 4–5 years of iprodione application. The EC 50 values of these 111 isolates ranged from 0.117 to 0.634 μg/ml. The historic and current populations were not significantly ( P > 0.05) different in sensitivity to iprodione. The EC 50 values of these 161 isolates to a carboxamide fungicide boscalid ranged from 0.002 to 0.391 μg/ml with a mean of 0.042 μg/ml. In the laboratory, three iprodione-resistant (IR) isolates HA17-IR, SZ31-IR, and SZ45-IR were induced from wild-type isolates HA17, SZ31, and SZ45, respectively. The EC 50 values of the IR isolates were 200-fold higher than those of the original wild-type parents. The IR isolates showed an increase in osmotic sensitivity. The IR isolate HA17-IR lost its ability to produce sclerotia, and showed a significantly lower virulence on rapeseed leaves than its parent isolate HA17. In contrast, the IR isolate SZ31-IR had a significantly higher virulence than its wild-type parent SZ31. PCR assays showed that the partial two-component histidine kinase ( os-1) gene, which is the putative target gene of iprodione, was deleted in the low virulent IR isolate HA17-IR. DNA sequence analysis showed that each of the other two IR isolates SZ31-IR and SZ45-IR had two point mutations in their partial os-1 genes. These results indicate that the mutations in os-1 gene may be associated with dicarboximide sensitivity, sclerotial development, and virulence in S. sclerotiorum.

Combining physical, chemical and biological methods for synergistic control of postharvest diseases: A case study of Black Root Rot of carrot

Combining different control methods can improve control efficacy, increase the spectrum of controlled pathogens and reduce the possibility of resistance development. To be successful, however, the different methods need to be compatible: the first treatment should not have any deleterious effect on the succeeding one; preferably, it should contribute to its efficacy. In the last few years, carrot growers in Israel have begun to brush carrots before storage to remove the outer peel of the root. In the present study we show that this practice enhances the appearance of Black Root Rot during storage, a postharvest disease caused by the fungus Thielaviopsis basicola. The chemical fungicide iprodione is usually applied before storage to reduce the development of postharvest diseases. We evaluated the efficacy of combining physical, low-residue chemical and biological control agents as an alternative to the conventional chemical control approach. A technology for the precise application of steam and combined application with stabilized hydrogen peroxide (Tsunami ® 100) or a yeast commercial product (Shemer™) were tested. Used alone, both the steam and Tsunami were highly effective at reducing disease decay but were phytotoxic to the roots. Application of combined treatments of sublethal steam followed by a sublethal dosage of Tsunami or Shemer improved efficacy and disease control by 80 and 86%, respectively. These combinations showed a synergistic effect as compared to each of the treatments alone. The same pattern, effecting up to 54% disease control, was observed with the non-compatible combination of applying Tsunami first, washing it off with water and then applying Shemer. Thus disease-control agents can potentially be used for a short period, then washed off, if needed, and efficiently followed by application of a biological control agent. The biological pathway and mode of action are still under investigation but to the best of our knowledge, this is the first study to mathematically demonstrate synergistic effects of sublethal treatments applied sequentially to control postharvest disease as a potential method to reduce the use of chemicals in fruit and vegetables.

Dissipation rates of iprodione and thiacloprid during tomato production in greenhouse

The behaviour of the insecticide thiacloprid and the fungicide iprodione was investigated in greenhouse tomato fruits, when both pesticides were applied in two different rates (normal dose-ND, and double dose-DD). Thiacloprid residues were below the already established EU MRLs (0.5 mg/kg) 2 and 7 days after ND and DD application, respectively. Iprodione residues were always below EU MRLs (5 mg/kg) in both application rates. The impact of storage on pesticide residues in tomatoes was also assessed. Significantly higher iprodione residue levels were observed during post harvest storage compared with those determined in fresh harvested tomatoes. Mean residue levels determined in fresh harvested tomatoes 12 days after iprodione application were 0.69 mg/kg whereas, in post harvest tomatoes stored for the same period was 0.86 mg/kg. On the contrary, no differences were noticed in thiacloprid residues between post harvest stored and fresh harvested tomatoes. Model equations that best describe the dissipation curves obtained from the experimental data of iprodione and thiacloprid in tomatoes showing different behaviour of the two pesticides. Half-life period of iprodione in ND treatment, calculated by the best fitted experimental data, (2nd order model) was 6.8 days, whilst for thiacloprid the best fitted to experimental data, model equation (R.F. 1st order model) gave a half-life of 1.9 days.

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

AbstractThis 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.

Molecular characterization of field azoxystrobin-resistant isolates of Botrytis cinerea

Sensitivity of 184 Botrytis cinerea field isolates to a Qo inhibitor (QoI) fungicide azoxystrobin was determined in this study. Among the 184 isolates, seven showed resistance to azoxystrobin. All these seven azoxystrobin-resistant (AR) isolates were also resistant to a benzimidazole fungicide carbendazim, and a dicarboximide fungicide iprodione. Negative cross-resistance between azoxystrobin and a carboxamide fungicide boscalid was not observed in AR isolates of B. cinerea. Analysis structure of partial cytochrome b ( cyt b) gene from B. cinerea showed that a 1204-bp intron inserted directly after the codon 143 of cyt b gene was detected from 79 out of 184 isolates, and all the isolates having this intron were sensitive to azoxystrobin. This intron was not detected from any AR isolate. Sequence analysis of partial cyt b gene showed that all AR isolates had a point mutation at codon 143, which caused a change of glycine to alanine (G143A) at this codon position. Based on the point mutation, an allele-specific PCR assay was developed for the rapid detection of AR isolates of B. cinerea.

Biocontrol of Lettuce Drop Caused by Sclerotinia sclerotiorum and S. minor in Desert Agroecosystems.

Field experiments were conducted over 2 years in Yuma County, AZ, and Imperial County, CA, to determine the efficacy of several biocontrol agents for the management of lettuce drop caused by Sclerotinia spp. Commercial formulations of Trichoderma harzianum (Plantshield, Supersivit), Gliocladium virens (Soilgard), Coniothyrium minitans (Contans), and Bacillus subtilis (Companion) were evaluated and compared with the chemical fungicide iprodione (Rovral) against Sclerotinia sclerotiorum and S. minor. A single application of biocontrol products or of Rovral did not reduce lettuce drop caused by either Sclerotinia species. However, two applications of Contans, one at planting and one at post-thinning, significantly reduced the incidence of lettuce drop caused by S. sclerotiorum and increased yield but had no effect on S. minor at both locations in both years. Two applications of other biocontrol products did not significantly reduce disease incidence despite medium to high recovery following application. In contrast, Contans was only sporadically recovered following application. In vitro fungicide sensitivity evaluation revealed that both Trichoderma and Gliocladium species were tolerant to iprodione, dicloran (Botran), and vinclozolin (Ronilan) up to 1,000 ppm a.i., whereas both Sclerotinia spp. and C. minitans were sensitive to all three fungicides above 1 ppm. In summary, Contans was the most effective treatment for the control of lettuce drop caused by S. sclerotiorum, but no treatment was effective against S. minor in the desert lettuce production systems.

Activity of a microencapsulated mixture of constituents of essential oils against grey mould and powdery mildew in grapes and vegetables

In an effort to fend off microbial invaders, plants have evolved biosynthetic pathways to produce a variety of products, such as essential oils, that act as natural pesticides. In the current study, the in vivo activity of a microencapsulated mixture of eugenol, thymol and geraniol that are constituents of essential oils against grey mould (Botrytis cinerea) and powdery mildew (Uncinula necator, Sphaerotheca fuliginea) in grape and vegetables was investigated. Wine grape (cv. Agiorgitiko) field trials showed that the mixture, applied curatively close to harvest, was significantly (P=0.05) more effective in reducing B. cinerea bunch rot (43% reduction) than the fungicide iprodione (26%). Preventive spray applications of the mixture to greenhouse grown tomato (cv. Kalisti) had an overall efficacy of 30% under conditions of high grey mould pressure (max 74% infected leaf area on control). However, when the mixture of essential oils was applied curatively the gray mould severity on treated tomato (cv. Optima) plants did not differ significantly (P=0.05) from that of the control. Preliminary studies showed that the mixture did not affect the must/wine quality or the concentration of antioxidants in tomato fruit. In in vitro bioassays, B. cinerea mycelial growth was inhibited by 95% at the concentration of 0.14µg ml-1 (EC95 value) of the mixture. Although the mixture was less effective than wettable sulphur against powdery mildew (U. necator) on wine grape (cvs Merlot, Syrah) leaves, it reduced disease severity on bunches at the same level as sulphur. In greenhouse trials, the mixture had no effect against powdery mildew (S. fuliginea) in potted zucchini (cv. Pepo) plants.

Vegetative compatibility grouping in Botrytis cinerea using sulphate non-utilizing mutants

Twenty-one strains of Botrytis cinerea isolated from six plant species on ten sites throughout Israel, as well as a strain from France, were tested for vegetative and mycelial incompatibility, pathogenicity, resistance to the fungicides carbendazim and iprodione, and colony morphology. Selenate-resistant mutants were isolated from the strains as spontaneous, fast-growing sectors arising from restricted colonies on medium amended with sodium selenate with a mean frequency of 0.04 sectors/colony; 81% of the sectors were sulphate non-utilizing (sul) mutants. One hundred and four sul mutants were divided into two complementary groups: resistant (66 mutants) and sensitive to chromate. Based on compatibility reactions between chromate-resistant and chromate-sensitive sul mutants, 12 strains were compatible only with themselves and were each classified as belonging to different vegetative compatibility groups (VCGs). Nine strains were each compatible with one to three other strains, and were assembled into three multi-member VCGs. Mycelial incompatibility between wild-type strains (barrage), in the form of a zone of dark pigmentation or sparse mycelium with or without dark pigmentation of the agar along the line of confrontation, was observed for 70% of the inter-strain pairings. There was no correspondence in compatibility between strains revealed by two approaches: strains in different VCGs did not necessarily produce a barrage. However, self-compatibility was observed both as heterokaryon formation between complementary sul mutants and as an absence of barrages between mycelia of wild-type strains; wild-type strains belonging to the same VCG did not exhibit strong barrages, although weak antagonistic reactions were observed. Strains in two multi-member VCGs showed the same patterns of resistance to carbendazim and iprodione; the third multi-member VCG contained isolates with different patterns of resistance. Four morphological types were revealed among wild-type strains: conidial (five strains), sclerotial (six strains), intermediate (ten strains), and mycelial (one strain). On bean leaves, conidial strains were more aggressive than sclerotial strains.

Characterization of Genetic and Biochemical Mechanisms of Fludioxonil and Pyrimethanil Resistance in Field Isolates of Penicillium digitatum

Genetic and biochemical mechanisms of fludioxonil and pyrimethanil resistance in isolates of Penicillium digitatum were evaluated and compared to those characterized in other fungi. Resistant isolates were naturally occurring in packinghouses and were not associated with crop losses. For the phenylpyrrole fludioxonil, EC50 values were 0.02 to 0.04 microg/ml for sensitive, 0.08 to 0.65 microg/ml for moderately resistant (MR), and > 40 microg/ml for highly resistant (HR) isolates. Two fludioxonil-sensitive isolates evaluated were also significantly more sensitive to the unrelated dicarboximide fungicide iprodione, that also disrupts osmotic regulation, than the MR and HR isolates. There was no consistent relationship, however, between the HR and MR isolates and their sensitivity to iprodione or osmotic stress. Although, two nucleotide substitutions were found in a sequence analysis of the N-terminal amino acid repeat region of the os-1-related histidine kinase gene among isolates of P. digitatum, these were not correlated with fludioxonil resistance. In mycelia not exposed to fludioxonil, the amount of phosphorylated OS-2-related protein (PdOS-2) was higher in fludioxonil-sensitive isolates and lowest in the HR isolate. An increase in PdOS-2 was observed for sensitive and resistant isolates after exposure to fludioxonil. In addition, glycerol content in untreated mycelia of the fludioxonil-sensitive isolate was significantly higher than in resistant isolates. After exposure to fludioxonil, glycerol concentrations significantly increased in the sensitive and MR isolates, but not in the HR isolate. Thus, our studies indicate that the mode of action of fludioxonil in P. digitatum is probably the mitogen-activated protein kinase pathway that stimulates glycerol synthesis in sensitive and MR isolates. The general suppression of this pathway in resistant isolates was supported by the fact that growth and sporulation of MR and HR isolates were significantly reduced from that of sensitive isolates. In studies on the mode of action of anilinopyrimidines (AP), EC50 values for mycelial growth of P. digitatum and the previously characterized Botrytis cinerea were determined for cyprodinil and pyrimethanil using a defined culture medium without and with the addition of selected amino acids and homocysteine. The addition of amino acids resulted in a reduced toxicity of the two AP fungicides in both fungi, but the effect of each additive was significantly lower for P. digitatum than for B. cinerea. This suggests that methionine biosynthesis is not the primary target site of APs in P. digitatum.

Potential of 11 Pesticides to Initiate Downstream Drift of Stream Macroinvertebrates

Downstream drift of lotic macroinvertebrates induced by toxicants is a well-known ecologically relevant phenomenon. However, little is known about which toxicants can initiate drift, and potential drift-initiating effects of contaminants are not taken into account in ecotoxicological risk assessment. The aim of the present study was to evaluate potential drift-initiating action of 11 pesticides having different target groups and modes of action. Sublethal concentrations of the pesticides were tested in stream microcosms with amphipods (Gammarus pulex), blackfly larvae (Simulium latigonium), and mayfly larvae (Baetis rhodani). The results show that 6 out of 11 pesticides tested can initiate drift of macroinvertebrates at sublethal concentrations 7-22 times lower than acute LC(50)s (thiacloprid, imidacloprid, acetamiprid, iprodione, fenvalerate, and indoxacarb). All the toxicants that exhibited drift-initiating action are neurotoxic insecticides belonging to the groups of pyrethroids and neonicotinoids except the fungicide iprodione. The pesticides that did not initiate drift are fungicides (cyprodinil, prochloraz, and azoxystrobin), a juvenile-hormone mimic (fenoxycarb), and a pyrazole insecticide (tebufenpyrad) affecting cell energy production. Remarkably, for all the drift-initiating toxicants, drift of the tested animals was detected within 2 h after contamination. This shows that macroinvertebrate drift can be induced even by short-term pulse exposures to neurotoxic insecticides, at field-relevant concentrations. The present results imply that the possibility of drift-initiating effects of pesticides should be considered within the risk assessment framework for pesticides, as all neurotoxic substances that were investigated did initiate drift at sublethal concentrations.

Molecular characterization of benzimidazole-resistant isolates ofCladosporium fulvum

The benzimidazole fungicide thiophanate-methyl is commonly applied to control leaf mould of tomato caused by Cladosporium fulvum in China. In this study, 32 isolates of C. fulvum were examined for their sensitivities to thiophanate-methyl, and two benzimidazole-resistant (BenR) phenotypes BenR1 and BenR2 were identified. The BenR1 isolates were resistant to thiophanate-methyl, but were more sensitive to the phenylcarbamate fungicide diethofencarb than the wild-type isolates. The BenR2 isolates resistant to thiophanate-methyl were insensitive to diethofencarb. All tested isolates were sensitive to the dicarboximide fungicide iprodione. The complete beta-tubulin gene was isolated from this fungus to study its potential role in benzimidazole resistance. Analysis of the DNA sequence of the beta-tubulin gene showed that the BenR1 isolates had a point mutation at codon 198, causing a substitution of glutamic acid to alanine. In the BenR2 isolates, a point mutation at codon 200 causing a substitution of phenylalanine to tyrosine was detected. Based on these point mutations, a multiplex allele-specific PCR method was developed successfully for the first time to detect two point mutations at the beta-tubulin gene simultaneously in single PCR amplifications.

Resistance of Botrytis cinerea Isolates from Vegetable Crops to Anilinopyrimidine, Phenylpyrrole, Hydroxyanilide, Benzimidazole, and Dicarboximide Fungicides.

During February 2005, 55 single-spore isolates of Botrytis cinerea were collected at the end of the season from vegetable crops grown in 18 greenhouses on the island of Crete, Greece. They were tested for sensitivity to the anilinopyrimidine fungicides pyrimethanil and cyprodinil, the hydroxyanilide fungicide fenhexamid, the phenylpyrrole fungicide fludioxonil, the dicarboximide fungicide iprodione, and the benzimidazole fungicide carbendazim. Results of the study showed the existence of benzimidazole- and dicarboximide-resistant strains at frequencies of 61.8 and 18%, respectively. Moreover, for first time, the development of resistance to anilinopyrimidine fungicides by B. cinerea was detected in greenhouse vegetable crops on the island of Crete. High resistance frequencies of 49.1 and 57.4% were observed for pyrimethanil and cyprodinil, respectively. In addition, one isolate was found to be resistant to the hydroxyanilide fungicide fenhexamid, while no strains resistant to the phenylpyrrole fungicide were detected. Among the 55 isolates tested, 13 were resistant only to carbendazim, 6 were resistant only to anilinopyrimidines, 3 were resistant to both benzimidazoles and dicarboximides, 17 were resistant to both benzimidazoles and anilinopyrimidines, 6 were resistant to both dicarboximides and anilinopyrimidines, 1 was simultaneously resistant to benzimidazoles, dicarboximides, and anilinopyrimidines, 1 was resistant to both anilinopyrimidines and hydroxyanilides, and 8 were sensitive to all fungicides tested. A strong cross-resistance relationship was found between the two anilinopyrimidine fungicides tested when log transformed EC50 values of the isolates were subjected to a linear regression analysis (r = 0.71). Despite the detection of several phenotypes with simultaneous resistance to chemically unrelated active ingredients, in none of the remaining possible fungicide pairs was there observed any kind of cross-resistance relationship.

Control of Rhizoctonia solani in a tobacco-float system using low rates of iprodione- and iprodione-resistant strains of Gliocladium roseum

Results obtained using low rates of the fungicide iprodione- and iprodione-resistant strains of Gliocladium roseum to control Rhizoctonia solani Kühn (Teleomorph: Thanatephorus cucumeris (Frank) Donk) in a tobacco float system are reported. The objectives were three-fold: to obtain G. roseum (GNL) strains resistant to the fungicide iprodione; to verify that the mutants maintained the same characteristics of the wild type; and to control R. solani in a tobacco float system by the application of low doses of fungicide combined with a resistant biological control agent (BCA) strain. Two resistant strains were obtained and the IC50 values were 44.7 and 5000μgml−1 for GNL wild type and mutants, respectively. The results showed the same level of disease control in plots with a high rate of iprodione and in plots with a low rate of fungicide, applied together with GNLr1 (96%) and GNLr2 (98%) iprodione-resistant strains of G. roseum. Less-disease control was obtained by a reduced dose of iprodione, when applied alone.

EFEITO DE FUNGOS ANTAGONISTAS E PRODUTOS QUÍMICOS NO CONTROLE DA PODRIDÃO PARDA EM POMARES DE PESSEGUEIRO

Um experimento com controle biológico em campo foi conduzido no município da Lapa-PR, para o controle de Monilinia fructicola em pessegueiro cultivar BR-1. Agentes biológicos previamente selecionados de campo de produção foram comparados com o fungicida iprodione e com fosfitos de Ca e de K. O experimento contou com 10 tratamentos: seis fungos antagonistas (F1, F2 e F4 – Trichothecium roseum; F9 – Penicillium sp; F3 – Cephalosporium sp; F13 – Alternaria sp), dois fosfitos (Ca e K), iprodione e testemunha. A avaliação foi feita por incidência no campo e na pós-colheita, sendo os tratamentos aplicados por pulverização e imersão, respectivamente. Em relação à incidência em campo, destacaram-se o iprodione e, na seqüência, os fosfitos de K, com 71,4%, e de Ca, com 64,2% de controle. Entre os antagonistas, destacaram-se F3, F1 e F2, com nível de controle superior a 64% em relação à testemunha. Após a colheita, os frutos foram mantidos à temperatura ambiente e avaliados no terceiro dia de exposição pela incidência da doença. Nesse momento, foi observada uma baixa eficiência entre os tratamentos, somente destacando-se o fungicida. Também foram avaliados o peso médio dos frutos, diâmetro, firmeza da polpa e sólidos solúveis totais, não havendo diferença estatística entre os tratamentos. Paralelamente às avaliações de campo, frutos não pulverizados foram colhidos para receberem em pós-colheita os mesmos tratamentos executados no campo. Estes foram feridos, imersos nos tratamentos e avaliados pela incidência da doença no segundo e quarto dias de exposição no ambiente. Iprodione, fosfito de Ca e F1 exerceram o maior controle das infecções latentes. Nas áreas feridas, destacaram-se iprodione, F2 e F4.

Evaluation of Entomopathogenic Fungus Metarhizium anisopliae Against Soil-Dwelling Stages of Cabbage Maggot (Diptera: Anthomyiidae) in Glasshouse and Field Experiments and Effect of Fungicides on Fungal Activity

The effect of two isolates of the entomopathogenic fungus Metarhizium anisopliae (Metchnikoff) Sorokin (389.93 and 392.93) on root-feeding stages of cabbage root fly, Delia radicum (L.), was studied under glasshouse and field conditions. In glasshouse studies, the effect of drenching a suspension of conidia (concentration 1 x 10(8) m(-1), 40 ml per plant, applied on four occasions) onto the base of cabbage plants infested with D. radicum eggs was compared with mixing conidial suspension into compost modules (concentration 1 x 10(8) ml(-1), 25 ml per plant) used to raise seedlings. Drench application reduced the mean number of larvae and pupae recovered per plant by up to 90%, but the compost module treatment had no statistically significant effect. Both application methods reduced the emergence of adult flies from pupae by up to 92%. Most conidia applied as a drench application remained in the top 10-cm layer of compost. Applications of the fungicides iprodione and tebuconazole, which are used routinely on brassica crops, were compatible with using M. anisopliae 389.93 against D. radicum under glasshouse conditions, even though these fungicides were inhibitory to fungal growth on SDA medium. In a field experiment, drench applications of M. anisopliae 389.93 to the base of cauliflower plants at concentrations of 1 x 10(6) to 1 x 10(8) conidia ml(-1) did not control D. radicum populations, although up to 30% of larval cadavers recovered supported sporulating mycelium. Drench applications often exhibited considerable lateral movement on the soil surface before penetrating the ground, which may have reduced the amount of inoculum in contact with D. radicum larvae.

Sorption, degradation and leaching of the fungicide iprodione in a golf green under Scandinavian conditions: measurements, modelling and risk assessment

In cold climates, fungicides are used on golf greens to prevent snow mould causing serious damage to the turf. However, fungicide residues have been detected in runoff from golf courses, which may lead to restrictions on use. There is therefore an urgent need to improve understanding of the processes affecting leaching of fungicides from turfgrass systems to allow identification of green construction and management practices that minimize environmental impacts. In this study we monitored the leaching of the fungicide iprodione in a putting green. Sorption and degradation of iprodione was measured in batch and incubation experiments, and the simulation model MACRO was used as a risk assessment tool. Degradation of iprodione was bi-phasic, with a rapid initial phase (half-life 17 h) caused by enhanced biodegradation. Degradation rates slowed considerably after 5 days, with half-lives of up to 38 days. Sorption of iprodione was linear, with a K(oc) value of ca 400 cm(3) g(-1). MACRO reasonably accurately matched measured drainflows and concentrations of iprodione in soil and drainflow. However, peak concentrations in drainage were underestimated, which was attributed to preferential finger flow due to water repellency. The results also showed the importance of the organic matter content in the green root zone in reducing leaching. It was concluded that, with 'reasonable worst-case' use, losses of iprodione from greens can occur at concentrations exceeding water quality limits for aquatic ecosystems. Snow mould problems should be tackled by adopting green root zone mixes that minimize leaching and 'best management practices' that would avoid the need for intensive prophylactic use of fungicides.

Cross-Enhanced Degradation of Dicarboximide Fungicide Residues in Soils

The dicarboximide fungicides iprodione, procymidone, and vinclozolin are widely used to control <i>Botrytis</i> bunch rot on grapes. The degradation rates of these chemicals in five vineyard soil samples in the Penedès region (Catalonia, Spain) had been previously determined. These soil samples had been treated with the fungicide iprodione, procymidone, or vinclozolin three times under laboratory conditions over 200 days. The objective of this study was to evaluate the cross-enhanced degradation of these fungicides in soils from the previous study to determine if a soil sample previously treated with a dicarboximide fungicide enhanced its own degradation but not the degradation of the other compounds. The analyses were conducted over a 77-day period beginning on the same day of each cross-treatment. Under these conditions, for each fungicide, the time to 90% degradation was ~7days if the soil was pretreated with the same fungicide and was 35 to 56 days if the soil was pretreated with one of the other fungicides, indicating that cross-enhancement of degradation did not occur. This study demonstrated a clear trend toward higher rates of fungicide loss in soils with three applications of the same fungicide.

Techniques and parameters used in compatibility tests between Beauveria bassiana (Bals) Vuill and in vitro phytosanitary products

The objective of this work was to test and compare different techniques used in tests for compatibility between the entomopathogenic fungus Beauveria bassiana (Balsamo) Vuill and phytosanitary products, in order to develop a protocol for in vitro tests. Four modes of contact were studied between B bassiana (CG432) and the fungicides iprodione (Rovral) 500 g litre(-1) SC) and azoxystrobin (Amistar) 500 g kg(-1) WG), and the insecticide endosulfan (Thiodan) 350 g litre(-1) EC), at three rates. The techniques consisted in incorporating the products into the culture medium (IM), combining the conidia into the products mix (MP) and spraying the products before (SB) and after (SA) inoculation of the fungus on Petri dishes. The fungitoxic effect of the products was studied on the basis of parameters such as germination, colony-forming units (CFUs), vegetative growth and sporulation. The effect of azoxystrobin on conidial germination was significantly higher in the IM technique than in the other techniques. With regard to CFUs, the IM and SB techniques showed the greatest differences relative to the control. Vegetative growth and sporulation were more affected when azoxystrobin was sprayed before the fungus was applied. At the commercial rate, iprodione had a greater effect on the CFU parameter in the IM and MP techniques, and on vegetative growth in the IM technique, than the other techniques used; however, there was no significant difference occurred between the techniques at the commercial rate with respect to germination and sporulation. Endosulfan was more toxic to germination in techniques SB and SA, and to the CFUs parameter in techniques IM and MP. As to vegetative growth and sporulation, regardless of rate, a more pronounced effect was observed in IM than in the other techniques. It can be inferred that there are differences between techniques and that a standardization of the compatibility tests is necessary. Another inference is that these techniques should reflect realistic exposure of the fungus to chemical formulations under field conditions.

The use of powder and essential oil ofCymbopogon citratus against mould deterioration and aflatoxin contamination of ?egusi? melon seeds

Experiments were carried out to determine the potential of using the powder and essential oil from dried ground leaves of Cymbopogon citratus (lemon grass) to control storage deterioration and aflatoxin contamination of melon seeds. Four mould species: Aspergillus flavus, A. niger, A. tamarii and Penicillium citrinum were inoculated in the form of conidia suspension (approx. 10(6) conidia per ml) unto shelled melon seeds. The powdered dry leaves and essential oil from lemon grass were mixed with the inoculated seeds at levels ranging from 1-10 g/100 g seeds and 0.1 to 1.0 ml/100 g seeds respectively. The ground leaves significantly reduced the extent of deterioration in melon seeds inoculated with different fungi compared to the untreated inoculated seeds. The essential oil at 0.1 and 0.25 ml/100 g seeds and ground leaves at 10 g/100 g seeds significantly reduced deterioration and aflatoxin production in shelled melon seeds inoculated with toxigenic A. flavus. At higher dosages (0.5 and 1.0 ml/100 g seeds), the essential oil completely prevented aflatoxin production. After 6 months in farmers' stores, unshelled melon seeds treated with 0.5 ml/ 100 g seeds of essential oil and 10 g/100 g seeds of powdered leaves of C. citratus had significantly lower proportion of visibly diseased seeds and Aspergillus spp. infestation levels and significantly higher seed germination compared to the untreated seeds. The oil content, free fatty acid and peroxide values in seeds protected with essential oil after 6 months did not significantly differ from the values in seeds before storage. The efficacy of the essential oil in preserving the quality of melon seeds in stores was statistically at par with that of fungicide (iprodione) treatment.