Iprodione Research Articles

Reasoned opinion on the modification of the existing MRL for iprodione in celeriac

Reasoned opinion on the modification of the existing MRL for iprodione in celeriac

Control of Postharvest Gray Mold of Table Grapes in the San Joaquin Valley of California by Fungicides Applied During the Growing Season

Fungicides applied before harvest were evaluated to control postharvest gray mold of table grapes, caused by Botrytis cinerea. The concentrations of thiophanate methyl (THM), iprodione (IPR), cyprodinil (CYP), pyraclostrobin + boscalid (PS+BO), pyrimethanil (PYR), or fenhexamid (FEN) that inhibited the growth of four isolates sensitive to these fungicides by 50% (EC50) were 12.4, 2.5, 0.61, 0.29/0.57, 0.26, or 0.17 mg liter-1, respectively. THM, IPR, CYP, PS+BO, PYR, or FEN were applied to detached 'Thompson Seedless' berries at the equivalent of the maximum approved rates of 600, 500, 270, 59/116, 370, or 290 mg liter-1, respectively, except PS+BO, which were used at 54.2% of their current registered maximum rates. The berries were inoculated with B. cinerea 48 or 24 h before treatment or 24 or 48 h after treatment. Gray mold 2 weeks after treatment and storage at 15°C was lowest after FEN application, followed by PYR, CYP, IPR, PS+BO, and THM. In commercial vineyards, one application of FEN, PYR, CYP, or PS+BO, all at their current maximum approved rates, 2 weeks before harvest reduced postharvest gray mold by approximately 50%. When fungicides were applied repeatedly after berry set either in mixtures or alternated with fungicides of different mode of action classes, postharvest gray mold was reduced by about 50% using a commercial air-blast sprayer and by 70 to 87% using a hand-held sprayer that was directed into the clusters. The fungicide sensitivity of isolates collected in numerous vineyards indicated those with reduced sensitivity to all of the tested fungicides, except FEN, were common. The efficacy of preharvest fungicide regimes was not sufficient to replace postharvest sulfur dioxide fumigation.

Semi-selective media for the isolation of Phaeomoniella chlamydospora from soil and vine wood.

Two semi-selective culture media, F10S (PDA + folpet 10 ppm + streptomycin sulphate 1 g l -1 ) and RB150S (PDA + rose bengal 150 ppm + streptomycin sulphate 1 g l -1 ), were developed for the isolation of the phytopathogenic fungus Phaeomoniella chlamydospora from soil samples and vine tissues. The media were selected so that they would allow proper growth of the pathogen and would partially inhibit eleven other common fungal genera. Eight antifungal agents were tested: Folpan (a.i. folpet), Captazel (a.i. captan), Benlate (a.i. benomyl), Chipco (a.i. iprodione), Switch (a.i. cyprodinil + fl udioxonil), rose bengal, and the bactericidal antibiotic streptomycin sulphate at several doses. Recovery of Pa. chlamydospora from wood samples was 40% better on RB150S and 50% better on F10S than on PDA, while the contaminants were reduced by 42% with RB150S, and by 48% with F10S. Pathogen reisolation from artificially contaminated soil samples was improved with F10S, while RB150S facilitated pathogen detection in samples containing moderate amounts of Rhizopus, Trichoderma, Penicillium, Alternaria or Trichoderma or in soils heavily contaminated with bacteria. F10S and RB150S improved the isolation of Pa. chlamydospora from wood and soil and can be used as alternatives to current culture media.

Iprodione delays male rat pubertal development, reduces serum testosterone levels, and decreases ex vivo testicular testosterone production

Iprodione (IPRO) is a dichlorophenyl dicarboximide fungicide similar to procymidone and vinclozolin. All three of these fungicides induce Leydig cell tumors in the rat testis in long-term studies and an endocrine mode of action has been hypothesized to mediate this effect. Although both procymidone and vinclozolin antagonize the androgen receptor (AR) in vitro and in vivo, IPRO does not appear to be an AR antagonist. We proposed that pubertal exposure to IPRO would delay male rat pubertal development and reduce testosterone production within the testis. Sprague–Dawley weanling rats were dosed by gavage with 0, 50, 100, or 200 mg/kg /day of IPRO from post-natal day (PND) 23 to 51/52. The onset of puberty (progression of preputial separation (PPS)) was measured starting on PND 37. Organ weights, serum hormones, and ex vivo testis steroid hormone production under stimulated (+human chorionic gonadotropin (hCG)) and unstimulated (−hCG) conditions were measured at necropsy. IPRO delayed PPS at 100 and 200 mg/kg/day and decreased androgen sensitive seminal vesicle and epididymides weights at 200 mg/kg/day. Furthermore, IPRO increased adrenal and liver weights at 200 mg/kg/day, presumably by different mechanism(s) of action. Serum testosterone levels were decreased along with serum 17α-hydroxyprogesterone and androstenedione whereas serum LH was unaffected. IPRO reduced ex vivo testis production of testosterone and progesterone. Taken together, these results suggest that IPRO affects steroidogenesis within the testis, not through disruption of LH signaling, but possibly through enzyme inhibition of the steroidogenic pathway before CYP17. These data, along with the reported failure of IPRO to elicit an AR antagonism in vitro, provide evidence that IPRO differs from the dicarboximides procymidone and vinclozolin in that the effects on male rat pubertal development result from an inhibition of steroidogenesis and not AR antagonism.

IPRODIONE DELAYS MALE RAT PUBERTAL DEVELOPMENT, REDUCES SERUM TESTOSTERONE, AND DECREASES EX VIVO TESTICULAR TESTOSTERONE PRODUCTION

Iprodione (IPRO) is a dichlorophenyl dicarboximide fungicide similar to procymidone and vinclozolin, which are both known to antagonize the androgen receptor (AR). Based upon a pilot study, we hypothesized that pubertal exposure to IPRO would delay male rat pubertal development and reduce testosterone production within the testis. Sprague-Dawley weanling rats were dosed by gavage with 0, 50, 100, or 200 mg/kg/day of IPRO from postnatal day (PND) 23 to 51/52. The progression of preputial separation (PPS) was measured starting at PND 37. Organ weights, serum hormones, and ex vivo testis production under stimulated (+human chorionic gonadotropin (hCG)) and unstimulated (−hCG) conditions were measured at necropsy. IPRO delayed PPS at 100 and 200 mg/kg/day and decreased androgen sensitive seminal vesicle and epididymides weights. Furthermore, IPRO increased adrenal and liver weights. Serum testosterone levels were decreased along with serum progesterone and 17alphahydroxyprogesterone whereas serum LH was unaffected. IPRO reduced ex vivo testis production of testosterone, progesterone, and 17alphahydroxyprogesterone. Taken together, these results suggest that IPRO affects steroidogenesis within the testis, not through disruption of LH signaling, but possibly through inhibition of CYP11A (P450scc), Steroidogenic Acute Regulatory protein (StAR), or at some other point in the steroidogenic pathway before CYP17. These data, along with the reported failure of IPRO to elicit an AR antagonism response, provide evidence that IPRO differs from the dicarboximides procymidone and vinclozolin in that the effects on male rat pubertal development results from an inhibition of steroidogenesis and not AR antagonism. CRB supported through USEPA/NCSU Cooperative Training Agreement. This abstract does not necessarily reflect US EPA policy. (poster)

The antiandrogenic effect of dimethachlon and its mechanism

To evaluate the antiandrogenic effect of heterocyclic fungicide dimethachlon and its mechanism. A combination of in vivo and in vitro assays was selected. Hershberger assay was used to determine the antiandrogenic potential of dimethachlon in vivo. Six-week-old castrated male SD rats were administrated once daily for 7 days with testosterone propionate (TP, 100 micro g/d, sc) plus gavage doses of dimethachlon (50, 100 or 200 mg x kg(-1) x d(-1)), or procymidone (150 or 300 mg x kg(-1) x d(-1), positive control), or iprodione (100 mg x kg(-1) x d(-1), positive control), or flutamide (50 mg x kg(-1) x d(-1), positive control). Transcriptional activation assay in vitro was employed to determine the mechanism of antiandrogenic activity of dimethachlon. Human hepatoma liver cells HepG2 were transiently cotransfected with human androgen receptor (AR) expression plasmid and AR-dependent luciferase report plasmid. Transfected cells were exposed to various concentrations of dimethachlon or flutamide with or without dihydrotestosterone to induce the expression of luciferase gene. In Hershberger assay, dimethachlon, as well as other known antiandrogens, caused decrease in weight of androgen dependent organs or tissues. In 200 mg/kg group, the weight of seminal vesicle, ventral prostate, dorsolateral prostate, Cowper's gland, and levator ani plus bulbocavernosus muscles decreased by 57.8%, 44.8%, 43.9%, 30.1%, and 34.1% respectively, but did not decrease in the vehicle control group. The order of their antiandrogenic potencies was: flutamide > procymidone > dimethachlon > iprodione. In transcriptional activation assay, dimethachlon could inhibit dihydrotestosterone-dependent AR activity in transfected HepG2 cells in dose-effect relationship. The inhibiting potency of dimethachlon was about 1/100 of that of flutamide. Dimethachlon has antiandrogenic effect, and acts as an AR antagonist. Its antiandrogenic potency is lower than flutamide and procymidone, but higher than iprodione.

Alternaria diseases of citrus - Novel pathosystems.

Citrus is affected by four diseases caused by Alternaria spp. Brown spot of tangerines, leaf spot of rough lemon, postharvest black rot of fruit occur widely in citrus areas of the world and are caused by different pathotypes of A. alternata. Mancha foliar occurs only on Mexican lime in western Mexico and is caused by A. limicola. Tangerine and rough lemon pathotypes produce host-specific toxins that affect membranes and respiration, respectively. Black rot is always associated with wounds and is caused by most citrus-associated isolates of A. alternata that produce endopolygalacturonase. Alternaria brown spot is a serious disease of susceptible tangerines and their hybrids in semi-arid Mediterranean climates as well as in more humid areas. Conidia, produced on lesions on mature and senescent leaves and stems under humid conditions, are dispersed by wind, and infect all juvenile tissues of susceptible cultivars when temperature and leaf wetness conditions are favorable. Commercially acceptable cultivars resistant to brown spot are being developed. Disease severity can be reduced by planting disease-free nursery stock on wider spacings, pruning tree skirts, and reducing irrigation and nitrogen fertilization. However, fungicides such as dithiocarbamates, triazoles, strobilurins, iprodione, or copper fungicides are used in most areas for disease control. A disease-forecasting model, the Alter-Rater, has been developed in Florida to assist in timing fungicide sprays.

Comparative acute renal effects of three N-(3,5-dichlorophenyl)carboximide fungicides: N-(3,5-dichlorophenyl)succinimide, vinclozolin and iprodione

A large number of carboximides have been synthesized, tested and, in some cases, marketed as agricultural fungicidal agents. One carboximide fungicide N-(3,5-dichlorophenyl) succimide (NDPS) proved to be both highly efficacious as a fungicide and a nephrotoxin. The purpose of this study was to compare the acute nephrotoxic potential of three N-(3,5-dichlorophenyl) carboximide fungicides [NDPS, vinclozolin (VCLZ) and iprodione (IPDO)] to determine if nephrotoxic potential correlated with fungicidal efficacy among this class of structurally-related agricultural agents. Male Fischer 344 rats (4 rats/group) received a single intraperitoneal injection of a fungicide (0.4 or 1.0 mmol/kg) or vehicle (sesame oil, 2.5 ml/kg), and renal function was monitored at 24 and 48 h. NDPS (0.4 or 1.0 mmol/kg)-induced renal effects were characterized by marked diuresis, increased proteinuria, elevated blood urea nitrogen (BUN) concentration and kidney weights, decreased organic ion accumulation by renal cortical slices and proximal tubular necrosis. In contrast, IPDO and VCLZ (0.4 or 1.0 mmol/kg) administration resulted in only minor or no alterations in the renal function parameters studied and renal morphology. These results suggest that fungicidal efficacy does not correlate with acute nephrotoxic potential among the N-3,5-dichlorphenyl) carboximide fungicides.