In vitro and in vivo effects of some pesticides on carbonic anhydrase enzyme from rainbow trout (Oncorhynchus mykiss) gills

Here we investigated the in vitro and in vivo effects of the pesticides, deltamethrin, diazinon, propoxur and cypermethrin, on the activity of rainbow trout (rt) gill carbonic anhydrase (CA). The enzyme was purified from rainbow trout gills using Sepharose 4B-aniline-sulfanilamide affinity chromatography method. The overall purification was approx. 214-fold. SDS-polyacrylamide gel electrophoresis showed a single band corresponding to a molecular weight of approx. 29 kDa. The four pesticides dose-dependently inhibited in vitro CA activity. IC₅₀ values for deltamethrin, diazinon, propoxur and cypermethrin were 0.137, 0.267, 0.420 and 0.460 μM, respectively. In vitro results showed that pesticides inhibit rtCA activity with rank order of deltamethrin > diazinon > propoxur > cypermethrin. Besides, in vivo studies of deltamethrin were performed on CA activity of rainbow trout gill. rtCA was significantly inhibited at three concentrations (0.25, 1.0 and 2.5 μg/L) at 24 and 48 h.     

In vitro inhibition of the carbonic anhydrase from saanen goat (Capra hircus) with pesticides

This study was conducted to determine the in vitro effects of four commonly used pesticides (Nuarimol™, Fenarimol™, Parathion-methyl™ and 2,4-D™) on erythrocyte carbonic anhydrase (CA) activity from Saanen goats (SG). The enzyme was 262.57-fold purified by affinity chromatography and the purity was confirmed by SDS-PAGE. Inhibitory effect of the pesticides on the purified enzyme was determined using the CO₂-hydratase activity method. IC₅₀ values of the pesticides that caused inhibition were determined by means of activity percentage diagrams. The concentrations of Nuarimol™, Fenarimol™, and 2,4-D™ that inhibited 50% of the enzymatic activity were 0.352, 0.924 and 2.04 mM, respectively. Conversely, the enzyme activity was increased by parathion-methyl.     

In vitro and in vivo effects of some pesticides on glucose-6-phosphate dehydrogenase enzyme activity from rainbow trout (Oncorhynchus mykiss) erythrocytes

We investigated the in vitro and in vivo effects of some pesticides on rainbow trout erythrocyte glucose-6-phosphate dehydrogenase enzyme. The enzyme was purified 1691-fold with a specific activity of 16.235 U/mg protein and a yield of 63%. Cypermethrin, and propoxur inhibited glucose-6-phosphate dehydrogenase enzyme in vitro and deltamethrin inhibited both in vivo and in vitro. The obtained IC₅₀ values for deltamethrin, cypermethrin, and propoxur were 0.63, 1.02, and 12 mM, respectively. The activity of the control was determined as 5.17 ± 0.62 U/g Hb in in vivo studies. The enzyme activities of the groups treated with 0.25 g/L deltamethrin were measured at 6, 12, 24, 48, and 72 h, and found to be 4.32 ± 0.47, 3.57 ± 0.39, 3.47 ± 0.45, 2.86 ± 0.37, and 2.31 ± 0.32 U/g Hb. In vivo experiments showed that deltamethrin significantly inhibited the G6PD enzyme activity after the 48th h (p < 0.05).     

Comet assay in gill cells of Prochilodus lineatus exposed in vivo to cypermethrin

Agricultural chemicals can induce genetic alterations on aquatic organisms that have been associated with effects on growth, reproduction and population dynamics. The evaluation of DNA damage in fish using the comet assay (CA) frequently involves the utilization of erythrocytes. However, epithelial gill cells (EGC) can be more sensitive, as they are constantly dividing and in direct contact with potentially stressing compounds from the aquatic environment. The aim of the present study was to evaluate (1) the sensitivity and suitability of epithelial gill cells of Prochilodus lineatus in response to different genotoxic agents through the application of the CA, (2) the induction of DNA damage in this cell population after in vivo exposure to cypermethrin. Baseline value of the CA damage index (DI) for EGC of juvenile P. lineatus was 144.68 ± 5.69. Damage increased in a dose-dependent manner after in vitro exposure of EGC to methyl methanesulfonate (MMS) and H₂O₂, two known genotoxic agents. In vivo exposure of fish to cypermethrin induced a significant increase in DNA DI of EGC at 0.150 μg/l (DI: 239.62 ± 6.21) and 0.300 μg/l (270.63 ± 2.09) compared to control (150.25 ± 4.38) but no effect was observed at 0.075 μg/l (168.50 ± 10.77). This study shows that EGC of this species are sensitive for the application of the CA, demonstrating DNA damage in response to alkylation (MMS), oxidative damage (H₂O₂), and to the insecticide cypermethryn. These data, together with our previous study on DNA damage induction on erythrocytes of this species, provides useful information for future work involving biomonitoring in regions where P. lineatus is naturally exposed to pesticides and other genotoxic agents.     

Impacts of hypersaline water on the biotransformation and toxicity of fenthion on rainbow trout (Oncorhynchus mykiss), striped bass (Morone saxatilis X Morone chrysops) and tilapia (Oreochromis mossambicus)

Hypersaline water derived from agricultural practices primarily in arid landscapes can impact fisheries in streams receiving run-off from fields. Previous studies have indicated significant elevation in the toxicity of thio-ether pesticides by hypersaline water in certain species of euryhaline fish due to enhanced formation of sulfoxide metabolites which may be more toxic than the parent compounds. The objectives of this study were to evaluate the effects of salinity on the toxicity of the thio-ether organophosphate pesticide, fenthion in three species of euryhaline fish: rainbow trout (Oncorhynchus mykiss), striped bass (Morone saxatilis X Morone chrysops), tilapia (Oreochromis mossambicus) and determine whether a relationship was observed between toxicity and enantioselective sulfoxidation. Stereochemical formation and total sulfoxide formation did not mirror acute toxicity in the three species exposed in fresh or hypersaline conditions. Mortality of striped bass and rainbow trout due to fenthion exposure was enhanced by hypersaline treatments and a trend towards increased toxicity was observed in tilapia. In liver microsomes of rainbow trout, inhibition of cytochrome P450 (CYP) caused a respective 7- and 3-fold increase in sulfoxide formation in liver microsomes fresh and saltwater fish, and a significant increase in the formation of the (+)R-sulfoxide. CYP inhibition also caused a significant elevation of the (+)R-sulfoxide in freshwater striped bass, but not in hypersaline-treated bass. The results indicated contribution by CYP in the sulfoxidation of fenthion as well as the formation of other metabolites in all three species. In summary, hypersaline conditions impacted fenthion toxicity under conditions that appeared to be independent of fenthion sulfoxide formation indicating a much more complex mechanism of action for compounds with phosphorothioate and thio-ether structural features potentially involving multiple oxidative pathways.     

Mutagenic, genotoxic and enzyme inhibitory effects of carbosulfan in rainbow trout Oncorhynchus mykiss

Rainbow trout (Oncorhynchus mykiss; 116.88 ± 21.69 g) were exposed to sublethal concentrations (25 μg/L) of carbosulfan for 60 days to test if the long term exposure of fish to carbosulfan affects red blood cells acetylcholinesterase (AChE), δ-aminolevulinic acid dehydratase (ALA-D) and paraoxonase (PON) enzyme activity and induces genotoxic and/or mutagenic effects. The exposure resulted in inhibition of AChE and ALA-D activity of rainbow trout when compared to control fish. The activity of PON was not affected by carbosulfan. Interestingly, carbosulfan was found to induce DNA damage in red blood cells (comet assay) and proved to be mutagenic as revealed by the Ames test. Results indicate that blood AChE and ALA-D of rainbow trout may be a sensitive biomarker for assessment of carbosulfan contaminated water bodies. Furthermore, because the Ames test and comet assay were proven successful to detect the genotoxicity of carbosulfan, we proposed that nonlethal techniques such as blood collection from caudal vein of fish should be used to determine potential toxic effects of other pesticides to surrounding environment.     

Susceptibility of the spider Theridion impressum to 17 pesticides

Susceptibility of immature individuals of the spider Theridion impressum to 17 pesticides (6 insecticides, 4 acaricides, 4 fungicides and 3 herbicides) was tested in the laboratory. The pesticides were applied at recommended rates in a Potter tower. Mortality was evaluated for 4 subsequent days. Broad-spectrum insecticides, cypermethrin+chlorpyrofos (Nurelle), -cypermethrin (Vaztak), and deltamethrin (Decis), were toxic to spiders. Selective insecticides, pirimicarb (Pirimor), Bacillus thuringiensis (Novodor), and triazamate (Aztec), were harmless. All tested acaricides, pirimiphos-methyl (Actellic), flufenoxuron (Cascade), -fluvalinate+thiometon (Mavrik), and bifenthrin (Talstar) showed high toxicity. Of the fungicides, dithianon (Delan), benomyl (Fundazol), iprodione (Rovral), and dodine (Syllit), only dithianon was slightly harmful, while the remaining fungicides were harmful. All herbicides, metazachlor (Butisan), clomazone (Command), and clopyralid (Lontrel), were harmless to T. impressum. Three selective insecticides, 3 fungicides and 3 herbicides are recommended for use in plant protection.     

Efficacy of insecticide mixtures against pyrethroid‐ and organophosphate‐resistant populations of Spodoptera litura (Lepidoptera: Noctuidae)

BACKGROUND: Spodoptera litura (F.) is an important pest worldwide, with over 112 host plants, and is exposed to insecticides throughout the year, resulting in the rapid development of resistance. Insecticide mixtures can delay the development of resistance more effectively than sequences or rotations. Cypermethrin, deltamethrin, profenofos, chlorpyrifos and fipronil were assessed separately and in mixtures against laboratory susceptible S. litura and two field‐collected populations. RESULTS: The field‐collected population from Khanewal (KWL) was significantly more resistant to cypermethrin, deltamethrin, chlorpyrifos and profenofos than one collected from Muzaffar Garh (MGH). Mixtures of cypermethrin + chlorpyrifos or profenofos and of deltamethrin + chlorpyrifos or profenofos at 1:1, 1:10 and 1:20 ratios significantly increased (P < 0.01) toxicity to cypermethrin and deltamethrin in field populations. The combination indices of cypermethrin + chlorpyrifos at 1:1 and 1:10 ratios and cypermethrin + fipronil at 1:1, 1:10 and 1:20 ratios for the KWL strain and of cypermethrin + profenofos or fipronil at 1:1, 1:10 and 1:20 ratios for MGH were significantly below 1, suggesting synergistic interactions. The inhibitors DEF and PBO largely overcame resistance to deltamethrin, cypermethrin and profenofos, suggesting that resistance to the insecticides was associated with esterase and monooxygenase detoxification respectively. CONCLUSION: Chlorpyrifos, profenofos and fipronil could be used in mixtures to restore cypermethrin and deltamethrin susceptibility. These findings may have considerable practical implications for S. litura resistance management. Copyright © 2008 Society of Chemical Industry     

Management and cross-infectivity potential of Colletotrichum acutatum causing anthracnose on bell pepper in Florida

Early anthracnose caused by Colletotrichum acutatum has become an increasingly serious disease on green, unripe bell pepper fruit in Florida. This contrasts with earlier reports of anthracnose occurring on bell pepper primarily as a ripe-rot disease of mature, colored pepper fruit caused by Colletotrichum gloeosporioides. Management of anthracnose on green bell pepper fruit using fungicides and a commercial inducer of systemic acquired resistance, acibenzolar-S-methyl (ASM), was evaluated during three seasons. In two of the three trials, all the fungicides tested including azoxystrobin, fludioxonil + cyprodinil, mancozeb, famoxadone + cymoxanil, copper hydroxide, and ASM significantly increased the number of marketable fruit compared with control plants. These trials identified fungicides that could contribute to a successful pest management program on pepper for controlling anthracnose caused by C. acutatum. The cross-infectivity potential of C. acutatum was investigated on tomato and strawberry by in vitro and field inoculation. Anthracnose lesions formed readily on wound-inoculated detached fruits of all hosts in in vitro assays. Under field conditions, after inoculation, anthracnose lesions occurred on pepper fruit but no lesions of anthracnose were found on either ripe or unripe tomato or strawberry fruit in adjacent plots.     

化学农药对段木栽培中黑木耳主要害虫黑光甲和食丝谷蛾的毒力测定和药效试验

本文采用18种杀虫剂,测定了它们对两种黑木耳害虫——黑光甲和食丝谷蛾的毒力和药效。试验了有关农药混用对防治黑光甲的增效作用。结果表明:溴氰菊酯、氯氰菊酯、百树菊酯、杀灭菊酯、杀螟松、二嗪农、氧化乐果、乐果、敌敌畏和杀虫双对黑光甲成虫和幼虫有较高的药效。4种拟除虫菊酯、杀螟松、二嗪农,氧化乐果,敌敌畏和敌百虫对食丝谷蛾幼虫有较高的药效。溴氰菊酯与西维因混用,敌百虫与乐果混用对防治黑光甲有明显的增效作用。     

The use of small enclosures to assess the toxic effects of cypermethrin on fish under field conditions

An emulsion concentrate formulation of cypermethrin (‘Ripcord’) was applied at seven different dose rates (between 5 and 500 g a. i. ha^?1) to the water surface of 1-m³ stainless steel enclosures, located in a small outdoor pond, to which were introduced small rainbow trout and common carp. A range of water quality parameters were monitored frequently in all of the enclosures and in the open pond. At daily intervals, the concentration of cypermethrin was determined in water samples, collected from the enclosures treated with 5, 50 and 500 g a. i. ha-^?1. Two further water samples were collected from these enclosures, and their toxicity was assessed by bioassay, using Gammarus pulex as the test organism. The experiment was terminated 96 h after application, when all the fish were removed and examined for mortality or adverse toxic effects. Throughout the study, the water quality parameters in all the enclosures remained similar to those recorded in the open pond. Cypermethrin residues, in the enclosures treated with 5 and 50 g a. i. ha^?1, attained peak concentrations 24 h after application, and thereafter declined to about 50% of this level. Maximum cypermethrin concentrations were not attained until about 72 h after application in the enclosure treated with 500 g a. i. ha^?1. Highly consistent responses, closely correlated with the applied dose rates, were obtained with G. pulex and both species of fish. Rainbow trout appeared to be about three times more susceptible to cyper-methrin than common carp, with calculated LD₅₀ values of 92 and 300 g a. i. ha^?1, respectively. It is therefore most unlikely that fish mortality would result from the use of cypermethrin in normal agricultural practice.     

Binary mixtures of pyrethroids produce differential effects on Ca influx and glutamate release at isolated presynaptic nerve terminals from rat brain

Isolated rat brain synaptosomes were used to evaluate the action of pyrethroid mixtures on Ca²⁺ influx and subsequent glutamate release under depolarizing conditions. In equipotent binary mixtures at their respective and/or estimated EC₅₀s with deltamethrin always as one of the two components, cismethrin, λ-cyhalothrin, cypermethrin, esfenvalerate and permethrin were additive and S-bioallethrin, fenpropathrin and tefluthrin were less-than-additive on Ca²⁺ influx. In binary mixtures with deltamethrin always as one of the two components, esfenvalerate, permethrin and tefluthrin were additive and λ-cyhalothrin was less-than-additive on glutamate release. Binary mixture of S-bioallethrin and cismethrin was additive for both Ca²⁺ influx and glutamate release. Only a subset of pyrethroids (S-bioallethrin, cismethrin, cypermethrin, and fenpropathrin) in binary mixtures with deltamethrin caused a more-than-additive effect on glutamate release. These binary mixtures were, however, only additive (cismethrin and cypermethrin) or less-than-additive (S-bioallethrin and fenpropathrin) on Ca²⁺ influx. Therefore, increased glutamate release evoked by this subset of pyrethroids in binary mixture with deltamethrin is not entirely occurring by Ca²⁺-dependent mechanisms via their action at voltage-sensitive calcium channels. These results suggest that pyrethroids do not share a common mode of toxicity at presynaptic nerve terminals from rat brain and appear to affect multiple target sites, including voltage-sensitive calcium, chloride and sodium channels.     

Variations among field isolates of Botrytis cinerea in their sensitivity to antifungal compounds

Seventeen field isolates of Botrytis cinerea were compared by determining their radial growth on synthetic media containing various amounts of 21 antifungal compounds. Twelve of these compounds were fungicides that are recommended for the control of Botrytis infections. There were marked differences between the isolates in their sensitivity to the compounds. Individual isolates displayed high levels of resistance to some of the fungicides, including benomyl, carbendazim, iprodione, thiabendazole, thiophanate-methyl, vinclozolin and zineb. The most potent growth inhibitors were benomyl and carbendazim (ED₉₅ values for most isolates <0.1 μg fungicide ml^?1 media), dichlofluanid, iprodione, nystatin, thiabendazole, thiophanatemethyl and vinclozolin (ED₉₅ values for most isolates < 1.0 μg ml^?1), and captan, chlorothalonil, dicloran and thiram (ED₉₅ values for most isolates < 6.0 μg ml^?1). Zineb was much less potent than the other recommended anti-Botrytis fungicides; it was no more effective than carboxin, dinocap and mancozeb (ED₉₅ values for most isolates > 25 μg ml^?1).     

Dissipation of three organochlorine and four pyrethroid pesticides sprayed in a greenhouse environment during hydroponic cultivation of gerbera

A wide range of pesticides (insecticides, acaricides and fungicides) is used in the hydroponic cultivation of gerbera. The fate and behaviour of some of these commonly used pesticides (organochlorine and pyrethroid insecticides/acaricides) in a greenhouse installation was investigated. The concentrations of endosulfan, dicofol, tetradifon, permethrin, bifenthrin, cypermethrin and deltamethrin in the air of the greenhouse were related to their physicochemical properties and respective application rates. Of these compounds, endosulfan exhibited the highest concentration in the greenhouse air 2 h after application (10 microg m(-3)), due to its highest volatility; afterwards, up to 12 h post-application, a rapid decrease was recorded which finally led to a concentration of 0.41 microg m(-3) at 6 days post-application. Dicofol exhibited the same trend of dissipation in the greenhouse air; its concentration decreased from 0.27 microg m(-3) immediately after the application to 0.12 microg m(-3) at 6 days post-application. Tetradifon, bifenthrin and permethrin were found at concentrations lower than 0.1 microg m(-3) at 2 h post-application, and cypermethrin and deltamethrin could not be detected. The concentrations of all the above pesticides in the drain water of the open hydroponic system were relatively high immediately after application and decreased rapidly during the following 3 days. In the closed hydroponic system, all the pesticides accumulated in the nutrient solution during the first 24 h after application and slowly decreased in concentration over the following 3 days. The spray operators applying these pesticides were exposed to rather high concentrations and the spray deposits were monitored on the chest and forehead of the operator. Endosulfan exhibited the highest concentrations of the seven pesticides. The organochlorine pesticides (endosulfan, dicofol and tetradifon) were usually detected at higher concentrations on the chest than on the forehead of the operator; pyrethroids were detected at higher concentrations on the forehead than on the chest of the operator.     

Physiological response of rainbow trout (Salmo gairdneri) to acute fenvalerate intoxication

The physiological responses of rainbow trout (Salmo gairdneri) to fenvalerate intoxication during aqueous exposure were examined to provide information about the pyrethroid mode of action in fish. Trout (n = 4) were exposed to 412 ± 50 μg/liter fenvalerate and died in 10.9 ± 1.5 hr. Brain, liver, and carcass fenvalerate concentrations associated with mortality were 0.16 ± 0.05, 3.62 ± 0.57, and 0.25 ± 0.05 mg/kg, respectively. Visible signs of intoxication included elevated cough rate, tremors, and seizures. Histopathological examination of gill tissue showed damage consistent with irritation. An evaluation of respiratory-cardiovascular and blood chemistry responses indicated an elevated rate of metabolism associated with increasingly severe seizures. A cessation of ventilatory and cardiac activity, occurring with the seizures, was also observed. Finally, urine osmolality, Na⁺ and K⁺ concentrations, and Na⁺ and K⁺ excretion rates were elevated with intoxicated trout. The physiological responses of rainbow trout to fenvalerate intoxication suggest that besides effects on the nervous system, effects on respiratory surfaces and renal ion regulation may be associated with the mechanism of pyrethroid action in fish.     

四种杀菌剂对烟草灰霉病菌的毒力及对烟草灰霉病的抑制作用

为筛选防治烟草灰霉病的有效药剂,采用菌丝生长速率法和孢子萌发法测定氟啶胺、咪鲜胺、苯醚甲环唑及代森锰锌4种杀菌剂对烟草灰霉病菌Botrytis cinerea的毒力,同时通过离体叶片评价这4种杀菌剂对烟草灰霉病的保护和治疗作用。结果表明,氟啶胺和咪鲜胺对菌丝生长活性抑制最强,有效抑制中浓度ECjs50平均值分别为0.02、0.03 mg/L,苯醚甲环唑次之,代森锰锌最弱,EC_(js50)平均值分别为0.39、7.86 mg/L;氟啶胺对孢子萌发活性抑制最强,代森锰锌次之,有效抑制中浓度EC_(mf50)平均值分别为0.06、0.16 mg/L,咪鲜胺和苯醚甲环唑最弱,ECmf50平均值均大于25.00 mg/L。离体试验表明,氟啶胺对烟草灰霉病保护作用最强,浓度为50 mg/L时,防治效果为100.00%,咪鲜胺和苯醚甲环唑次之,防治效果分别为88.62%和76.46%,代森锰锌最弱,浓度为1 000 mg/L时防治效果仅为75.81%;氟啶胺对烟草灰霉病治疗作用最强,浓度为100 mg/L时的防治效果为85.75%,咪鲜胺和苯醚甲环唑次之,浓度为200 mg/L时的防治效果分别为85.47%和76.48%,代森锰锌最弱,浓度为1 000 mg/L时防治效果为70.24%。表明氟啶胺和咪鲜胺更适合烟草灰霉病的防治。     

Potentiation/antagonism of deltamethrin and cypermethrins with organophosphate insecticides in the cotton bollworm, Helicoverpa armigera (Lepidoptera: Noctuidae)

The joint action of pyrethroids deltamethrin and cypermethrins in combination with organophosphates ethion, profenofos, chlorpyrifos, quinalphos, and triazophos was studied on putatively resistant field populations of Helicoverpa armigera from Pakistan by using a leaf-dip method. Ethion produced a good potentiation with deltamethrin, cypermethrin, alphacypermethrin, and zetacypermethrin, whereas profenofos, chlorpyrifos, quinalphos, and triazophos exhibited an antagonism with deltamethrin as well as cypermethrins. Implications of using mixtures for counteracting insecticide resistance are discussed.     

蔬菜田常用农药对诺氏虫疠霉生长和产孢的影响

研究了17种蔬菜田常用杀虫剂、杀菌剂对诺氏虫疠霉生长及产孢的影响。结果表明，在10种杀虫剂中，恶二嗪类杀虫剂安打对菌落生长和产孢的影响最小，抑菌率仅为15．78％，产孢量与对照无显著差异。新烟碱类杀虫剂吡虫啉对诺氏虫疠霉抑制作用最强，抑菌率达到100％。7种杀菌剂对诺氏虫疠霉生长和产孢影响都很显著，其中取代苯基类杀菌剂乙霉威对其影响最小，抑菌率为31．51％，但产孢量不到对照的1／3。有机硫类杀菌剂代森锰锌对诺氏虫疠霉生长、产孢的影响最大，抑菌率为100％。     

Baseline toxicity of several pesticides to Hyaliodes vitripennis (Say) (Hemiptera: Miridae)

Hyaliodes vitripennis (Say) is a univoltine indigenous predacious mirid. It has been reported in several orchards where IPM programmes are used. It is a generalist, and feeds on phytophagous mites in addition to other arthropods. In Quebec, a foliar application of imidacloprid, deltamethrin or lambda‐cyhalothrin is used at least once per season to manage arthropod pests such as leafhoppers and leaf‐eating caterpillars. Meanwhile, several applications of metiram, flusilazole, myclobutanil and mancozeb are made to control apple scab [Venturia inaequalis (Cooke) Winter]. In laboratory trials, comparison of lethal concentrations of the three insecticides against H vitripennis nymphs and adults showed no significant difference. However, when lethal concentrations were compared between two growth stages for each insecticide, a significant difference was noted between adults and nymphs treated with lambda‐cyhalothrin, adults being more susceptible than nymphs. No such difference could be detected for imidacloprid or deltamethrin. When LC₅₀ values were compared with the manufacturer's label rates, deltamethrin and imidacloprid were toxic to the nymphs and adults, and lambda‐cyhalothrin was slightly toxic to the nymphs and moderately toxic to the adults. Among the fungicides evaluated in the laboratory, myclobutanil showed moderate toxicity to adults at the manufacturer's label rate. The remaining fungicides had no toxic effects to adults or nymphs, even at four times the manufacturer's label rate. © 2001 Society of Chemical Industry     

Persistence of resistance to fungicides in Sphaerotheca fuliginea

Isolates ofSphaerotheca fuliginea collected in 1981–1983 in cucumber glasshouses in the Netherlands were tested for their sensitivity to benzimidazole fungicides, dimethirimol, dinocap and pyrazophos.Resistance to dinocap was not observed, although this fungicide has been used for over 30 years. Resistance to benzimidazole fungicides and dimethirimol has been persistent since these fungicides were withdrawn for control of cucumber powdery mildew more than 10 years ago. Although pyrazophos has only been used incidentally after 1977, the level of resistance has not decreased.Factors possibly involved in the persistence of resistance and implications for disease control in practice are discussed.Samenvatting De gevoeligheid voor twee benzimidazool-fungiciden en dimethirimol, dinocap en pyrazofos werd getoetst vanSphaerotheca fuliginea isolaten die in 1981–1983 verzameld waren in komkommerkassen in Nederland. Resistentie tegen dinocap werd niet waargenomen, ofschoon dit fungicide al meer dan 30 jaar wordt gebruikt.De resistentie tegen benzimidazool-fungiciden en dimethirimol, die meer dan 10 jaar geleden werden teruggetrokken voor de bestrijding vanS. fuliginea, was persistent. Hoewel pyrazofos slechts incidenteel gebruikt is sinds 1977, is het resistentieniveau niet teruggelopen. Factoren die mogelijk betrokken zijn bij de persistentie van resistentie en de gevolgen voor de ziektebestrijding worden besproken.