Chlorogenic acid,a metabolite identified by untargeted metabolome analysis in resistant tomatoes,inhibits the colonization by Alternaria alternata by inhibiting alternariol biosynthesis

Tomato fruits can be contaminated by saprophytic strains of Alternaria alternata which is the reason for the frequent occurrence of Alternaria toxins like alternariol, alternariol monomethylether or tenuazonic acid in these types of products. It was shown earlier that alternariol is a colonization factor for tomatoes. In the current analysis two different tomato genotypes were analysed by untargeted comprehensive two-dimensional gas chromatography mass spectrometry (GC×GC-MS). This analysis revealed clear differences in the metabolic profiles which were paralleled by differences in resistance towards Alternaria colonization. One of the genotypes was more resistant against A. alternata infection and contained high amounts of chlorogenic acid in contrast to the other genotype which was sensitive against infection. In in vitro analysis, chlorogenic acid reduced alternariol biosynthesis during the first days of growth of A. alternata. Expression analysis of the alternariol polyketide synthase gene, a key gene in the biosynthesis of alternariol, also revealed a temporal reduction in its expression in the first phases of growth. However by chromatographic analysis it could be demonstrated that chlorogenic acid was degraded over time. This degradation leads to a relief of inhibition resulting in an only temporal inhibition of alternariol biosynthesis. In vivo colonization experiments revealed that chlorogenic acid reduces colonization of tomatoes by A. alternata in a concentration dependent manner, which however is partly counteracted by the addition of alterariol.     

Organophosphorus insecticide residues in virgin Greek olive oil, 1988–1990

Organophosphorus insecticide residues have been monitored for two years in virgin olive oil after dimethoate and fenthion treatments to control the olive fruit fly. No dimethoate residues were detected in any of the samples. For the first and second years, 50% and 21%, respectively, of the samples contained no detectable fenthion residues, while 4% and 6%, respectively had residue concentrations exceeding the Codex Alimentarious Maximum Residue Limit (1 mg kg^?1). The mean concentration was 0·236 mg kg^?1 oil and the estimated daily intake of fenthion 0·0002 mg kg^?1 body weight (Acceptable Daily Intake 0·001 mg kg^?1 body weight). The parent compound was the most important residue in fresh samples, while aged samples contained a higher amount of the metabolite fenthion sulfoxide. The contribution of the oxygen analogues (P= 0 metabolites) of fenthion to the total residue concentration was<5% in most cases.     

Control of infection of tomato fruits by <Emphasis Type="Italic">Alternaria</Emphasis> and mycotoxin production using plant extracts

Tomato fruits are susceptible to infection by Alternaria species. In addition, Alternaria species may contaminate the fruits with mycotoxins. There is thus interest in control systems to minimise pathogenicity and control toxin production. The objectives of this study were to examine the effect of plant extracts of Eucalyptus globulus and Calendula officinalis on the growth of strains of Alternaria alternata and A. arborescens, on pathogenicity of tomato fruits and mycotoxin production. The growth bioassays showed that the ethanolic and chloroformic fractions of E. globulus were the most effective in reducing growth of A. alternata (66–74 %) and A. arborescens (86–88 %), respectively at 2500 μg/g. The effects of plant extracts on mycotoxin biosynthesis were variable and strain dependent. The most effective fractions in decreasing mycotoxin accumulation were the ethanolic and chloroformic extracts of E. globulus, which reduced tenuazonic acid by 89 %, alternariol by 75–94 % and almost complete inhibition of alternariol monomethyl ether. All the tested fractions reduced percentage of infected tomato fruits when compared to the controls. The ethanolic and chloroformic fractions of E. globulus completely inhibited growth of A. alternata and A. arborescens on unwounded fruits and reduced the aggressiveness on wounded fruits of strains of both species significantly.     

Systemic fungicide residues in oil from field-treated olive1

A survey was carried out in Sardegna (IT) on residues in olive oil from olive treated against Spilocaea oleugina with several systemic fungicides at normal and double dose rate: benomyl, thiophanate-methyl, bitertanol, penconazole and fenarimol, all currently not registered for this use in Italy. There was a rapid decrease in benomyl, thiophanate-methyl, and bitertanol in the samples of oil from treated olives collected 0, 10, and 20 days after last treatment, but the degradation of fenarimol appeared slower. In contrast, the concentration of penconazole increased with time. It is suggested that registration of the first four compounds for use on olive would be justified.     

Chlorpyrifos-methyl plus bioresmethrin; Methacrifos; Pirimiphos-methyl plus bioresmethrin; and synergised bioresmethrin as grain protectants for wheat

Field trials with various pesticide combinations were carried out on bulk wheat in commercial silos in Queensland, South Australia and Western Australia. Laboratory bioassays on samples of treated grain at intervals over 8 months using malathion-susceptible and malathion-resistant strains established the following orders of efficacy: against Sitophilus oryzae (L.), chlorpyrifos-methyl 10 mg kg^?1 + bioresmethrin 1 mg kg^?1 = methacrifos 15 mg kg^?1 in aerated storage > pirimiphos-methyl 4 or 6 mg kg^?1 + bioresmethrin 1 mg kg^?1 = bioresmethrin 4 mg kg^?1 + piperonyl butoxide 16 mg kg^?1; against Rhyzopertha dominica (F.), bioresmethrin 4 mg kg^?1 + piperonyl butoxide 16 mg kg^?1 > methacrifos 15 mg kg^?1 > chlorpyrifos-methyl 10 mg kg^?1 + bioresmethrin 1 mg kg^?1 = pirimiphos-methyl 4 or 6 mg kg^?1 + bioresmethrin 1 mg kg^?1. All treatments completely prevented production of progeny in Sitophilus granarius (L.), Tribolium castaneum (Herbst), T. confusum Jackquelin du Val and Oryzaephilus surinamensis (L.). The biological efficacy of methacrifos was greater and the rate of degradation lower in aerated than in non-aerated storage. Residue levels of all compounds were determined chemically and were below proposed international residue levels to be considered by the Codex Alimentarius Commission.     

In vitro and in vivo toxicity of nano chitosan against Curvularia lunata,the causal microorganism of fruit rot and blight,a new disease of olive (O. europaea L.)

During 2019, fruit blight and rot symptoms were observed on olive (O. europaea L.) fruits on trees grown in the Experimental Farm, Faculty of Agriculture, Sohag University, Egypt. Fungal isolates recovered from symptomatic fruits were identified as Curvularia lunata (Walker) Boedijn (two isolates) and A. alternata (Fr.) Keissl. (one isolate). Koch’s postulates were fulfilled by a pathogenicity test conducted in vitro on olive fruits wounded before inoculation with fungal isolates and incubation at 25?±?0.2 °C in a moist chamber for a week. During incubation, we observed the development of blight and rot symptoms on fruits inoculated with both isolates of C. lunata, similar to the natural symptoms described. Conversely, A. alternata was nonpathogenic to olive fruits. PCR amplification using the specific P1 and P2 primers to C. lunata based on the Clg2p Ras protein gene sequences resulted in approx. 870 base pairs for all DNA of C. lunata analyzed, confirming the identification of C. lunata. In vitro, both chitosan nano and non-nano scale effectively inhibited mycelial growth by reducing linear mycelium and biomass and sporulation of C. lunata. In vivo, chitosan nanoscale at 2.0 mg mL^?1 greatly reduced the infection and the lesion diameter of C. lunata inoculated fruits after a week and effectively induced defense-related enzyme activity of PO, PPO, and PAL. This report is the first recording of fruit blight and rots on olive caused by C. lunata, as a new disease. Also, we report the in vitro and vivo toxicity of nanoparticles of chitosan as a natural elicitor, effectively inducing defense-related enzymes against C. lunata.

     

Organophosphorothioates and synergised synthetic pyrethroids as grain protectants on bulk wheat

Organophosphorothioates and synergised synthetic pyrethroids were used in duplicate field trials carried out on bulk wheat in commercial silos in Queensland and New South Wales. Laboratory bioassays using malathion-resistant strains of insects were carried out on samples of treated grain at intervals over 9 months. These established that all treatments were generally effective. Deltamethrin (2 mg kg^?1)+ piperonyl butoxide (8 mg kg^?1), fenitrothion (12 mg kg^?1)+ fenvalerate (1 mg kg^?1)+ piperonyl butoxide (8 mg kg^?1), fenitrothion (12 mg kg^?1)+ phenothrin (2 mg kg^?1)+ piperonyl butoxide (8 mg kg^?1) and pirimiphos-methyl (4 mg kg^?1)+ permethrin (1 mg kg^?1)+ piperonyl butoxide (8 mg kg^?1) controlled common field strains of Sitophilus oryzae (L.) and Rhyzopertha dominica (F.). Against a highly resistant strain of S. oryzae, deltamethrin (2 mg kg^?1)+ piperonyl butoxide (8 mg kg^?1) was superior to the remaining treatments. All treatment combinations completely prevented progeny production in Tribolium castaneum (Herbst), T. confusum Jacquelin du Val and in Ephestia cautella (Walker). Residues of deltamethrin, fenvalerate, permethrin and phenothrin were determined and shown to be highly persistent on stored wheat. During milling, residues accumulated in the bran fractions and were reduced in white flour. They were not significantly reduced during baking.     

Characterization of Alternaria species associated with potato foliar diseases in China

The population structure of Alternaria species associated with potato foliar diseases in China has not been previously examined thoroughly. Between 2010 and 2013, a total of 511 Alternaria isolates were obtained from diseased potato leaves sampled in 16 provinces, autonomous regions or municipalities of China. Based on morphological traits and molecular characteristics, all the isolates were identified as Alternaria tenuissima, A. alternata or A. solani. Of the three species, A. tenuissima was the most prevalent (75·5%), followed by A. alternata (18·6%) and A. solani (5·9%). Phylogenetic analysis based on sequences of the internal transcribed spacer (ITS) region of ribosomal DNA (rDNA) of representative Alternaria isolates showed that A. solani was distinct from the two small‐spored Alternaria species. Phylogenetic analysis of the partial coding sequence of the histone 3 gene divided the same collection of isolates into three main clades representing A. tenuissima, A. alternata and A. solani, respectively. The pathogenicity of the isolates on detached leaves of potato cv. Favorite did not differ significantly between the three species or between isolates from different geographical origins. The results indicate that the population structure of Alternaria species associated with potato foliar diseases differs from that reported previously in China. This is the first report of A. tenuissima causing potato foliar diseases in China.     

<Emphasis Type="Italic">Alternaria alternata</Emphasis>: A new seed-transmitted disease of coriander in South Africa

This is the first report of Alternaria leaf spot disease on coriander (Coriandrum sativum L.) in South Africa. Using the agar plate method, Alternaria alternata was isolated from coriander seed lots together with four other fungal genera, which included Aspergillus, Fusarium, Penicillium and Rhizopus. Standard seed germination tests of coriander seed lots infected with seed-borne mycoflora showed a positive correlation with the number of diseased seedlings (r?=?0.239, p?<?0.01). Pathogenicity tests demonstrated that this seed-borne A. alternata was pathogenic on coriander and symptoms on leaves first appeared as small, dark brown to black, circular lesions (<5 mm diam.) that enlarged and coalesced to form dark brown blotches as time progressed. Leaf spot disease was most severe (64%) on wounded leaves inoculated with A. alternata. Re-isolation of A. alternata from diseased coriander plants satisfied the Koch’s postulates, thus confirming it as the causal agent of Alternaria leaf spot disease. Parsimony analysis based on rpb2 (GenBank Accession No. KT895947), gapdh (KT895949) and tef-1α (KT895945) sequences confirmed identity of the Alternaria isolate, which grouped within the A. alternata clade. Alternaria alternata was shown to be transmitted from infected coriander seed to the developing plants.     

Natural occurrence of <Emphasis Type="Italic">Fusarium</Emphasis> species and fumonisin on maize grains in Ethiopia

Fusarium species causing maize kernel rot are major threats to maize production, due to reduction in yield as well as contamination of kernels by mycotoxins that poses a health risk to humans and animals. Two-hundred maize kernel samples, collected from 20 major maize growing areas in Ethiopia were analyzed for the identity, species composition and prevalence of Fusarium species and fumonisin contamination. On average, 38 % (range: 16 to 68 %) of maize kernels were found to be contaminated by different fungal species. Total of eleven Fusarium spp. were identified based on morphological characteristics and by sequencing the partial region of translation elongation factor 1-alpha (EF-1α) gene. Fusarium verticillioides was the dominant species associated with maize kernels (42 %), followed by F. graminearum species complex (22.5 %) and F. pseudoanthophilium (13.4 %). The species composition and prevalence of Fusarium species differed among the areas investigated. Fusarium species composition was as many as eight and as few as four in some growing area. The majority of the maize samples (77 %) were found positive for fumonisin, with concentrations ranging from 25 μg kg^?1 to 4500 μg kg^?1 (mean: 348 μg kg^?1 and median: 258 μg kg^?1). Slight variation in fumonisin concentration was also observed among areas. Overall results indicate widespread occurrence of several Fusarium species and contamination by fumonisin mycotoxins. These findings are useful for intervention measures to reduce the impact of the main fungal species and their associated mycotoxins, by creating awareness and implementation of good agricultural practices.     

The behaviour of residues of flamprop-isopropyl and its breakdown products in barley

Residue data are reported for flamprop-isopropyl ( I ) in barley grain and straw samples following applications of the herbicide to crops grown in eight countries. The samples were analysed for I and its hydrolysis product N-benzoyl-N-(3-chloro-4-fluorophenyl)-DL -alanine ( II ). Following recommended applications (normally 1 kg ha^?1 at Feekes scale G-I/J), residues of I and II in the grain were low (90% were <0.02 mg kg^?1 for I , 86% were <0.06 mg kg^?1 for II , levels which were essentially the limits of determination). Residues in straw were higher and more variable, but again 63 and 77% of samples were below 1 mg kg^?1 for I and II , respectively.     

Epidemiology of Toxigenic Fungi and their Associated Mycotoxins for Some Mediterranean Crops

Recent data on the epidemiology of the common mycotoxigenic species of Fusarium, Alternaria, Aspergillus and Penicillium in infected or colonized plants, and in stored or processed plant products from the Mediterranean area are reviewed. Emphasis is placed on the toxigenicity of the causal fungal species and the natural occurrence of well known mycotoxins (aflatoxins, ochratoxins, fumonisins, trichothecenes, zearalenone, patulin, Alternaria-toxins and moniliformin), as well as some more recently described compounds (fusaproliferin, beauvericin) whose toxigenic potential is not yet well understood. Several Fusarium species reported from throughout the Mediterranean area are responsible of the formation of mycotoxins in infected plants and in plant products, including: Fusarium graminearum, F. culmorum, F. cerealis, F. avenaceum, F. sporotrichioides and F. poae, which produce deoxynivalenol, nivalenol, fusarenone, zearalenone, moniliformin, and T-2 toxin derivatives in wheat and other small grains affected by head blight or scab, and in maize affected by red ear rot. Moreover, strains of F. verticillioides, F. proliferatum, and F. subglutinans, that form fumonisins, beauvericin, fusaproliferin, and moniliformin, are commonly associated with maize affected by ear rot. Fumonisins, were also associated with Fusarium crown and root rot of asparagus and Fusarium endosepsis of figs, caused primarily by F. proliferatum. Toxigenic A. alternata strains and associated tenuazonic acid and alternariols were commonly found in black mould of tomato, black rot of olive and citrus, black point of small cereals, and black mould of several vegetables. Toxigenic strains of A. carbonarius and ochratoxin A were often found associated with black rot of grapes, whereas toxigenic strains of A. flavus and/or P. verrucosum, forming aflatoxins and ochratoxin A, respectively, were found in moulded plant products from small cereals, peanuts, figs, pea, oilseed rape, sunflower seeds, sesame seeds, pistachios, and almonds. Finally, toxigenic strains of P. expansum and patulin were frequently found in apple, pear and other fresh fruits affected by blue mould rot, as well as in derived juices and jams.     

Identification and characterization of <Emphasis Type="Italic">Alternaria</Emphasis> species causing leaf spot on cabbage,cauliflower, wild and cultivated rocket by using molecular and morphological features and mycotoxin production

Alternaria species are common pathogens of fruit and vegetables able to produce secondary metabolites potentially affecting human health. Twenty-nine isolates obtained from cabbage, cauliflower, wild and cultivated rocket were characterized and identified based on sporulation pattern and virulence; the phylogenetic analysis was based on the β-tubulin gene. Isolates were identified as A. alternata, A. tenuissima, A. arborescens, A. brassicicola and A. japonica. Pathogenicity was evaluated on plants under greenhouse conditions. Two isolates showed low level of virulence on cultivated rocket while the other isolates showed medium or high level of virulence. Isolates were also characterized for their mycotoxin production on a modified Czapek-Dox medium. Production of the five Alternaria toxins, tenuazonic acid, alternariol, alternariol monomethyl ether, altenuene and tentoxin were evaluated. Under these conditions, about 80% of the isolates showed the ability to produce at least one mycotoxin.     

The susceptibility of the Indian field mouse,Mus booduga gray,to anticoagulant rodenticidal baits

The baseline susceptibility of the Indian field mouse, Mus booduga was established for warfarin, bromadiolone and brodifacoum by means of nochoice feeding tests. The mice were found to be more susceptible to the second generation anticoagulants bromadiolone (0.005 g kg^?1) and brodifacoum (0.002 g kg^?1) than warfarin (0-25 g kg^?1). They required 8–10 days feeding on warfarin (0.25 g kg^?1) diet for complete mortality. A feeding period of 8 days corresponding to 99% mortality was suggested as a checking test for registering future warfarin resistance in suspect samples of M. booduga.     

Grain protectants for the control of malathion-resistant insects in stored sorghum

Duplicate experiments were carried out on bulk sorghum stored in South Queensland and in Central Queensland. Bioassays of treated grain, conducted during 6 months' storage, established that fenitrothion (12 mg kg^?1)+ bioresmethrin (1 mg kg^?1), and pirimiphos-methyl (4 mg kg^?1)+ carbaryl (8 mg kg^?1), controlled typical malathionresistant strains of Sitophilus oryzae (L.), Rhyzopertha dominica (F.), Tribolium castaneum (Herbst), and Ephestia cautella (Walker). Chlorpyrifos-methyl (10 mg kg^?1)+ pyrethrins (1.5 mg kg^?1)+ piperonyl butoxide (12 mg kg^?1), and fenitrothion (12 mg kg^?1)+ (1R)-phenothrin (1 mg kg^?1), also controlled the strains of S. oryzae, T. castaneum and E. cautella, but were only partly effective against R. dominica. Methacrifos (15 mg kg^?1) controlled all the tested species except E. cautella. Chemical assays established that the residues and rates of breakdown of these grain protectants on sorghum conformed to the general pattern for other cereal grains; residues from the above treatments were below the individual Maximum Residue Limits recommended by the Codex Alimentarius Commission.     

Acaricides and their residues in Spanish commercial beeswax

BACKGROUND: The purpose of this work was to determine residues of acaricides in recycled Spanish beeswax. RESULTS: Chlorfenvinphos, fluvalinate, amitraz, bromopropylate, acrinathrin, flumethrin, coumaphos, chlorpyrifos, chlordimeform, endosulfan and malathion residues were determined by GC‐µECD/NPD/MS detection. Owing to the extreme instability of amitraz, this analyte was transformed into the stable end‐metabolite 2,4‐dimethylaniline, later derivatised with heptafluorobutyric anhydride and determined by GC‐µECD/MS. Recoveries from spiked samples ranged from 86 to 108%, while quantification limits varied from 0.10 to 0.30 mg kg^?1 using GC‐µECD/NPD, and from 12 to 85 µg kg^?1 by GC‐MSD. Of a total of 197 samples analysed, only eight samples (4%) were free of residues of chlorfenvinphos (0.019–10.6 mg kg^?1), fluvalinate was present in 93.6% of samples analysed (0.027 –88.7 mg kg^?1), while coumaphos was confirmed in only five of the 134 samples analysed at concentrations of less than 195 µg kg^?1. The remaining acaricides were identified with different levels of incidence at concentrations from 12 to 231 µg kg^?1. CONCLUSIONS: Residues of acaricides were found in an extensive number of beeswax samples. The contamination with chlorfenvinphos and tau‐fluvalinate was very relevant, particularly as chlorfenvinphos is not legally authorised for use in beekeeping. The possible impacts of the main acaricides detected on larval and adult honey bees are discussed. Copyright © 2010 Society of Chemical Industry     

Fenitrothion plus (1R)-phenothrin,and pirimiphos-methyl plus carbaryl,as grain protectant combinations for wheat

Duplicate field trials were carried out on bulk wheat in commercial silos in Queensland and New South Wales. Laboratory bioassays on samples of treated grain at intervals over 9 months, using malathion-resistant strains of insects, established that treatments were generally effective. Fenitrothion (12 mg kg^?1)+ (1R)-phenothrin (2 mg kg^?1) was more effective than pirimiphos-methyl (6 mg kg^?1) + carbaryl (10 mg kg^?1) against Sitophilus oryzae (L.) and Ephestia cautella (Walker); the order of effectiveness was reversed for S. granarius (L.). Against Rhyzopertha dominica (F.), Tribolium castaneum (Herbst), T. confusum Jackquelin du Val and Oryzaephilus surinamensis (L.), both treatments effectively prevented the production of progeny. The order of persistence was pirimiphos-methyl> (1R)-phenothrin>carbaryl or fenitrothion. During processing from wheat to white bread, residues were reduced by 98% for carbaryl, >44% for (1R)-phenothrin, 98% for fenitrothion and 85% for pirimiphosmethyl.     

Grass weed control with herbicide-treated crop seeds

Fluazifop-butyl applied in lung oil at rates of 4.4 to 0.5 g a.i. kg^?1 soybean seeds was evaluated in the glasshouse for control of Eleuisine indica. Soybean seeds pretreated with herbicide at 4.4 to 2.1 g a.i. kg^?1 gave 100% control of E. indica at the highest sowing rate of four seeds per pot and 90 to 80% control when sowed at one seed per pot. Soybeans were not injured by the seed treatment. Cotton seeds pre-treated with fluazifop at 2.2 g a.i. kg^?1 seeds and sown 4 cm apart in a row across a 20 ± 20cm tray of soil containing seeds of Echinochloa crus-galli produced a weed-free band 12 cm wide centred on the row of cotton, without injury to cotton. CGA-82725 (2-propynyl 2-(4-((3, 5-dichloro-2-pyridinyl)oxy)phenoxy) propanoate) at 2–3 g a.i. kg^?1 seeds was as effective as 4–4 g fluazifop-butyl in controlling E. indica. but growth of soybean was retarded. Sethoxydim gave less control than fluazifop butyl at comparable rates and did not injure soybeans.     

The behaviour of residues of benzoylprop-ethyl and its breakdown products in wheat

Samples of wheat grain and straw have been analysed from trials with the wild oat herbicide benzoylprop-ethyl ( I ) in several countries. Following recommended commercial treatments (application of 1.0–1.6 kg ha^?1 at Feekes growth stage G-J), total residues of I and its hydrolysis product N-benzoyl-N-(3,4-dichlorophenyl)-DL - alanine (free and conjugated) were low and in the majority of instances they were < 0.01 mg kg^?1 in samples of grain from the UK, although rather higher residues were detected in some grain samples from other countries. Residues in straw were higher, but normally did not exceed 2 mg kg^?1, and were rather variable, possibly as a result of differences in agricultural practice.     

Residues of zeta‐cypermethrin in bovine tissues and milk following pour‐on and spray application

The depletion of zeta‐cypermethrin residues in bovine tissues and milk was studied. Beef cattle were treated three times at 3‐week intervals with 1 ml 10 kg^?1 body weight of a 25 g litre^?1 or 50 g litre^?1 pour‐on formulation (2.5 and 5.0 mg zeta‐cypermethrin kg^?1 body weight) or 100 mg kg^?1 spray to simulate a likely worst‐case treatment regime. Friesian and Jersey dairy cows were treated once with 2.5 mg zeta‐cypermethrin kg^?1 in a pour‐on formulation. Muscle, liver and kidney residue concentrations were generally less than the limit of detection (LOD = 0.01 mg kg^?1). Residues in renal‐fat and back‐fat samples from animals treated with 2.5 mg kg^?1 all exceeded the limit of quantitation (LOQ = 0.05 mg kg^?1), peaking at 10 days after treatment. Only two of five kidney fat samples were above the LOQ after 34 days, but none of the back‐fat samples exceeded the LOQ at 28 days after treatment. Following spray treatments, fat residues were detectable in some animals but were below the LOQ at all sampling intervals. Zeta‐cypermethrin was quantifiable (LOQ = 0.01 mg kg^?1) in only one whole‐milk sample from the Friesian cows (0.015 mg kg^?1, 2 days after treatment). In whole milk from Jersey cows, the mean concentration of zeta‐cypermethrin peaked 1 day after treatment, at 0.015 mg kg^?1, and the highest individual sample concentration was 0.025 mg kg^?1 at 3 days after treatment. Residues in milk were not quantifiable beginning 4 days after treatment. The mean concentrations of zeta‐cypermethrin in milk fat from Friesian and Jersey cows peaked two days after treatment at 0.197 mg kg^?1 and 0.377 mg kg^?1, respectively, and the highest individual sample concentrations were 2 days after treatment at 0.47 mg kg^?1 and 0.98 mg kg^?1, respectively. © 2001 Society of Chemical Industry