Abtou pencycuron: Identification, Infection Process and Telemorph Formation of the Pathogen of Chinese Amaranth Leaf Spot in Taiwan

A new leaf spot disease of Chinese amaranth (Amaranth mangotanus L.) caused by Rhizoctonia solani was frequently observed at the so-called organic farms in Taiwan during the summer season. The hyphae of RSA-03 and RSA-09 isolates obtained from Chinese amaranth leaf spot were able to anastomose in high frequency (> 70%) with R. solani AG 2-2 IIIB (ATCC 76124), but in low frequency (< 5%) with R. solani AG 2-1 (ATCC 76168), AG 2-2 IV (ATCC 76125), AG 2-3 (R6) and AG BI (ATCC 76132). When five isolates from Chinese amaranth leaf spot were respectively cultured in liquid glucose asparagine (GA) medium with or without thiamine-HCl, they were auxtrophic for thiamine-HCl and more closely resembled the ATCC 76124 isolate of R. solani AG 2-2 IIIB. The optimum temperature for mycelial growth of RSA-09 isolate from Chinese amaranth leaf spot was similar to one of R. solani AG 2-2 IIIB (ATCC 76124). Inoculation tests revealed that both RSA-03 and RSA-09 from Chinese amaranth leaf spot and R. solani AG 2-2 IIIB (ATCC 76124) were pathogenic to Chinese amaranth. Based on the anastomosis, thiamine-HCl requirement, growth temperature, and pathogenicity tests, the isolates from Chinese amaranth leaf spot were recommended as R. solani AG 2-2 IIIB. According to Koch’s postulates tests, it was proved that the Chinese amaranth leaf spot was caused by the basidiospores of T. cucumeris, the telemorph of R. solani AG 2-2 IIIB. The basidiospores (105 spore/ml) of the pathogen were sprayed to leaf surface of Chinese amaranth. The inoculated plants were put in the moist chamber at 28℃. Primary lesions appeared as small, circular water-soaked spots on leaves of Chinese amaranth six days after inoculation. After additional incubation, claw-like lesions growing out from the primary lesions expanded into the leaves tissues and caused secondary lesions with large-sized irregular necrotic spots. When Chinese amaranth leaves were inoculated, basidiospores of the pathogen germinated and penetrated into the epidermal cell walls nine hours after inoculation. Mass mycelia were formed 18hrs after inoculation, then development of mass mycelia into stroma-like structure 21hrs after inoculation. In the study, Naito’s soil-over-culture method for production of hymenia was modified. It was found that the peat moss and soil-over culture method (PSC method) was much more effective in producing hymenia of T. cucumeris RSA-03 and RSA-09. The procedures of PSC method were as follows: (1) to inoculate the fungus onto potato- yeast extract-dextrose agar plate in a 9-cm petri dish, (2) to incubate at 28℃for 4 days until the fungal colony covered the agar plate surface, (3) the agar plate surface was covered with 90ml soil [included 40% (v/v) BVB No. 4 peat moss and maintained the soil moisture at 40 ~ 50% (v/v)], (4) experiments were kept in moist chamber. After 4-day-incubation hymenial formation was observed. The PSC method was suitable for hymenial formation of the pathogen and able to markedly produce 3-4 fold hymenial amount compared to Naito’s soil-over-culture method. The factors affecting hymenial formation of the pathogen included temperature, humidity, light, aeration, and culture substrate. The temperatures were favorable for R. solani RSA-03 and RSA-09 hymenial formation at 24 ~ 28℃and the covered soil was at pH 5 ~ 7. The amendments of covered soil with various organic and inorganic materials, antagonists, and fungicides did significantly influence the hymenia formation of T. cucumeris RSA-03 and RSA-09. The hymenia of the fungus were completely inhibited in the covered soils amended with 1﹪(v/v) fish meal, tea seed pomace and chinaberry meal. Amendments of covered soil with Stretomyces padanus PMS-702, S. sioyaensis PMS-502, S. saraceticus SS-31 and S. misionensis PMS 101 also inhibited hymenial formation, but Bacillus pumilus PMB-102, B. thermoglucosidasius PMB-101 and B. subtilis BS-001 did not. The fungicides, mancozeb, benomyl, carbendazim, flutolanil, PCNB, iprodione and pencycuron were significantly effective in inhibiting the hymenial formation.

Yangzhou pioneer chemical CO.,LTD. 

About dicamba: Cancer incidence among pesticide applicators exposed to dicamba in the agricultural health study

BACKGROUND:
Dicamba is an herbicide commonly applied to crops in the United States and abroad. We evaluated cancer incidence among pesticide applicators exposed to dicamba in the Agricultural Health Study, a prospective cohort of licensed pesticide applicators in North Carolina and Iowa.
METHODS:
Detailed pesticide exposure information was obtained through a self-administered questionnaire completed from 1993 to 1997. Cancer incidence was followed through 31 December 2002 by linkage to state cancer registries. We used Poisson regression to estimate rate ratios and 95% confidence intervals for cancer subtypes by tertiles of dicamba exposure. Two dicamba exposure metrics were used: lifetime exposure days and intensity-weighted lifetime exposure days (lifetime days x intensity score).
RESULTS:
A total of 41,969 applicators were included in the analysis, and 22,036 (52.5%) reported ever using dicamba. Exposure was not associated with overall cancer incidence nor were there strong associations with any specific type of cancer. When the reference group comprised low-exposed applicators, we observed a positive trend in risk between lifetime exposure days and lung cancer (p = 0.02), but none of the individual point estimates was significantly elevated. We also observed significant trends of increasing risk for colon cancer for both lifetime exposure days and intensity-weighted lifetime days, although these results are largely due to elevated risk at the highest exposure level. There was no apparent risk for non-Hodgkin lymphoma.
CONCLUSIONS:
Although associations between exposure and lung and colon cancer were observed, we did not find clear evidence for an association between dicamba exposure and cancer risk.

Yangzhou pioneer chemical CO.,LTD. 

US pesticide and produce companies sued over banana pesticide

Source:Bloomberg

Dole Food Co., Fresh Del Monte Produce Inc. and Dow Chemical Co. are being sued by more than 1,000 banana plantation workers from Costa Rica, Ecuador and Panama in a new round of cases claiming injury from a pesticide.
Eight separate complaints filed since May 31 in federal court in Delaware over the use of dibromochloropropane.
The pesticide, which was banned in the US back in 1979, was sprayed on fields to eliminate nematode worms. Workers claim they were not advised to wear protective clothing and were never warned they were in any danger.
Around 16,000 Latin American workers have sued over similar cases in US courts over the last 20 years. However, most cases are dismissed with judges saying that they must use the courts in their native countries.
In 2010, a California appeals Judge threw out a $2.3 million 2007 verdict after Dole argued that the plaintiffs had lied about becoming sterile as a result of spraying chemicals.

Yangzhou pioneer chemical CO.,LTD. 

About pencycuron：Compatibility of Beauveria bassiana with chemical pesticides for the control of the coffee root mealybug Dysmicoccus texensis Tinsley (Hemiptera: Pseudococcidae)

BY：Vanessa Andaló; Alcides Moino Jr.; Lenira V.C. Santa-Cecília; Giselle C. Souza

Several chemical substances are used to control insects, diseases and weeds, however many of these products are toxic to mankind and the animals, besides reducing the potential of pest control by predators, parasitoids and pathogens. The integrated control using selective chemical pesticides and entomopathogenic fungi is a viable strategy, however some of these products can impact these microorganisms, reducing vegetative growth, viability and sporulation. The objectives of this work were to evaluate the effect of chemical pesticides used in the coffee crop on the entomopatogenic fungus Beauveria bassiana (isolate UEL 114), for the control of the cofee root mealybug. A fungal suspension of 1 x 107 viable conidia/ml was added to solutions of the products at the recommended concentrations. After 1h, conidia were inoculated onto PDA medium, and quantification of germinated conidia assessed after 20h. The vegetative growth and sporulation were appraised eight days after the fungus inoculation onto PDA medium containing the products at recommended concentrations and maintained at the temperature of 25 ± 1ºC, 12h photofase and 70 ± 10% relative humidity. The mean diameter of the colonies was measured and conidial production quantified in a Neubauer chamber. Azafenidyne, Quintozene, Symazine + Ametryne, 2,4-D, Acetochlor and Oxyfluorfen affected the conidial germination. Thiamethoxan, Imidacloprid, Carbofuran and Pencycuron were compatible; whereas Glyphosate, Dimetilurea, Azafenidine, Quintozene, Symazine + Ametryne, 2,4-D, Acetochlor and Oxyfluorfen significantly impacted vegetative growth and sporulation of B. bassiana UEL 114.



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Dicamba monooxygenase: structural insights into a dynamic Rieske oxygenase that catalyzes an exocyclic monooxygenation

Dicamba (2-methoxy-3,6-dichlorobenzoic acid) O-demethylase (DMO) is the terminal Rieske oxygenase of a three-component system that includes a ferredoxin and a reductase. It catalyzes the NADH-dependent oxidative demethylation of the broad leaf herbicide dicamba. DMO represents the first crystal structure of a Rieske non-heme iron oxygenase that performs an exocyclic monooxygenation, incorporating O(2) into a side-chain moiety and not a ring system. The structure reveals a 3-fold symmetric trimer (alpha(3)) in the crystallographic asymmetric unit with similar arrangement of neighboring inter-subunit Rieske domain and non-heme iron site enabling electron transport consistent with other structurally characterized Rieske oxygenases. While the Rieske domain is similar, differences are observed in the catalytic domain, which is smaller in sequence length than those described previously, yet possessing an active-site cavity of larger volume when compared to oxygenases with larger substrates. Consistent with the amphipathic substrate, the active site is designed to interact with both the carboxylate and aromatic ring with both key polar and hydrophobic interactions observed. DMO structures were solved with and without substrate (dicamba), product (3,6-dichlorosalicylic acid), and either cobalt or iron in the non-heme iron site. The substitution of cobalt for iron revealed an uncommon mode of non-heme iron binding trapped by the non-catalytic Co(2+), which, we postulate, may be transiently present in the native enzyme during the catalytic cycle. Thus, we present four DMO structures with resolutions ranging from 1.95 to 2.2 A, which, in sum, provide a snapshot of a dynamic enzyme where metal binding and substrate binding are coupled to observed structural changes in the non-heme iron and catalytic sites. 

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France bans Syngenta pesticide linked to bee decline

Source:Farmers Weekly Interactive

The French government has banned a pesticide linked to the decline of bees that is widely used to treat oilseed rape.
Cruiser OSR (active ingredients: thiamethoxam + fludioxonil + metalaxyl-M), which contains the neonicotinoid insecticide thiamethoxam, was banned for use on oilseed rape by the French Ministry of Agriculture.
Made by the Swiss agrichemical company Syngenta, Cruiser OSR is a seed treatment, which is coated onto the rape seeds.
The decision to ban Cruiser follows two studies earlier this year, in the UK and France, which found evidence that neonicotinoids contain chemicals that disorientate bees and prevent them from finding their way back to hives, causing colony collapse disorder.
Announcing the ban, France"s Ministry of Agriculture said it would be pushing for a European-wide ban with the European Commission and the European Food Safety Agency (EFSA).
Bees are vitally important to agriculture for pollinating our food crops and maintaining biodiversity in the rural environment.
A recent Friends of the Earth report estimated bees are worth £510m a year to the UK economy.
However, bee numbers have been declining worldwide in recent years and conservationists claim that pesticides are a contributing factor, in particular neonicotinoids.
Syngenta has less than two weeks to submit its own evidence before any ban in France is implemented. The company said called the ban "a dark day for French and European agriculture".
In its defence, Syngenta claimed no cases of bee mortality have been identified as being linked to Cruiser OSR - although 650,000ha of treated seeds are grown in France.
DEFRA said it was investigating the reports before deciding whether to act in line with its pesticide safety policy.
"We are assessing recent studies on neonicotinoids and will report our findings very shortly," a spokesman said.
"The UK has a robust system for testing and reviewing pesticide use and if the evidence shows the need for action, we will not hesitate to act."
Cruiser is available to use in the UK as a broad spectrum seed treatment, providing fungicidal and insecticidal use on oilseed rape, fodder rape and mustard.

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About pencycuron: Action mode Fungicide chemical group Common name

Action mode Fungicide chemical group Common name Nontarget effects Lipid, sterol, and other membrane components Lipid Aromatic hydrocarbons Dicloran Mutagen to Salmonella typhimurium [12] Etridiazole Retards nitrification by affecting ammonium oxidizers [13] Sterol Triazoles Triadimefon Long-term inhibiting effects on soil bacterial community [7] Triticonazole Increases total number of bacteria in soil [15] Cinnamic acid amide Dimethomorph Impacts nitrifying and ammonifying bacterial activities in sandy soils [17] Triazole Hexaconazole Impacts bacterial activities related to N cycling [19] Morpholine Fenpropimorph Inhibit general bacterial activity in wetland [16] Triazole Propiconazole Tebuconazole May retard plant-growth-promoting effects of Azospirillum brasilense on its hostplant [20] Intracellular membrane components Hydrochloride Acriflavine Thickens peripheral and cross cell wall of Staphylococcus aureus [18] Amino acid and protein synthesis Glucopyranosyl antibiotic Streptomycin Inhibits amino acid synthesis in bacteria [3] and is neurotoxic to amphibian [4] Tetracycline antibiotic Oxytetracycline Also used as bactericide [21] Signal transduction Phenylpyrroles Fludioxonil Toxic to algae [22] and potential risk to prokaryotes [23] Dicarboximides Iprodione Affects signal transduction in bacteria [24] Vinclozolin Inhibits total bacterial growth [25] Respiration NADH oxido-reductase (Complex I) inhibitors Pyrimidinamines Diflumetorim Unknown Succinate- dehydrogenase (Complex II) inhibitors Pyridine carboxamides Boscalid May affect growth of prokaryotes [26] Benzamides Flutolanil Gxathiin carboxamides Carboxin Inhibits denitrifying bacterial activity in wetland sediment [16] Oxidative phosphorylation uncouplers 2,6-dinitroanilines Fluazinam Have a potential risk to environmental microorganisms [27] Dinitrophenyl crotonate Dinocap Inhibits ammonifying bacterial activity and stimulate general bacterial respiration in soil [28] Mitosis and cell division Inhibitor of spindle microtubules assembly Methyl benzimidazole carbamate Benomyl May affect nitrifying bacteria [29] and arbuscular mycorrhizal fungi [30] Carbendazim Reduces the diversity of soil bacteria [31] Phenylurea Pencycuron May affect metabolically activated soil bacteria in short term [32]4 ISRN Ecology Table 1: Continued. Action mode Fungicide chemical group Common name Nontarget effects Nucleic acids synthesis RNA polymerase I inhibitors Acylalanines Metalaxyl Affects activities of ammonifying and nitrifying bacteria in soil [33] Oxazolidinones Oxadixyl Unknown Adenosin- deaminase inhibitors Hydroxypyrimidines Ethirimol Unknown Phthalonitrile Chlorothalonil Impacts bacterial activities related to N cycling [29] Multisite activity Dithiocarbamate Mancozeb Impacts bacterial activities related to nitrogen cycling [17] and carbon cycling [28] in soils Phthalimide CaptanI nhibits denitrifying bacterial Dithiocarbamate Thiramactivity [16] Anthraquinone Dithianon Reduces bacterial diversity in soil [34] Copper Copper sulfate Reduces the number of bacteria and streptomycetes in sandy soil [35]  

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