Fate and short-term persistence of permethrin insecticide injected in a northern Ontario (Canada) headwater stream

1·275 dm³ of a l·3g dm^?3 aqueous emulsion of permethrin (i.e. 1·658 g permethrin) was applied to the surface of a fast-flowing stream by manual injection. Water samples were collected from the top 1-cm layer at different intervals of time at various distances downstream from the site of application. Caged samples of stream detritus, crayfish, brook trout and stonefly nymphs, bottled sediment and potted aquatic plants were placed 280 m from the treatment site, and collected afterwards for residue analysis. The downstream movement of the chemical was not uniform with peak concentrations of about 12 ng ml^?1 at 30 m and 0·1 ng ml^?1 at 730 m from the treatment site. The peak concentrations (ng g^?1) in potted aquatic plants, caged detritus, crayfish and brook trout were about 18, 39, 14 and 11 respectively. The residues were higher than the ambient water concentration (1·67 ng ml^?1) and dissipated slowly. The peak concentration in the bottled sediment was 2·75 ng g^?1, and the residues were lost rapidly. In contrast, the naturally occurring sediment in a beaver pond showed high residues that persisted for a longer period of time. Permethrin concentrations in invertebrate drift ranged from 9 to 357 ng g^?1, depending on the distance from the application site. The study demonstrated that aquatic invertebrates, plants and stream detritus acted as the major sink for the chemical.     

Inhibition of ergosterol biosynthesis in Ustilago maydis by the fungicide 1-[2-(2, 4-dichlorophenyl)-4-ethyl-1, 3-dioxolan-2-ylmethyl]-1H-1, 2, 4-triazole

Inhibition of sporidial multiplication in cultures of Ustilago maydis by 1-[2-(2, 4-dichlorophenyl)-4-ethyl-1, 3-dioxolan-2-ylmethyl]-1H-1, 2, 4-triazole^a (CGA-64251), at concentrations of 0.1, 1.0 and 5.0 μg ml^?1, increased from about 15% during the first 4 h, to 58–70% during the subsequent 4 to 12-h period. Sporidia became swollen and highly branched in the presence of the fungicide. Total lipid content as a percentage of the dry weight was not affected after exposure of the sporidia to the fungicide at 0.1 or 5 μg ml^?1 for 4 h, but synthesis of ergosterol and other demethyl-sterols was inhibited by 87–92%. Large quantities of methyl-sterol precursors of ergosterol and of free fatty acids accumulated in the treated sporidia. Fungitoxicity of CGA-64251 is attributed to inhibition of ergosterol biosynthesis at the stage of sterol C-14 demethylation.     

Host-pathogen interaction of root-knot nematode <Emphasis Type="Italic">Meloidogyne incognita</Emphasis> on pepper in the southeast of Spain

The feeder roots of pepper plants (cv. California Wonder) in Campo de Cartagena (southeast Spain) were found to be severely infected by Meloidogyne incognita. Morphometric traits, differential host test and DNA analysis based on PCR were used to characterize the nematode. Naturally and artificially infected pepper plants showed severe yellowing and stunting, with heavily deformed and damaged root systems. Root galls were spherical and commonly contained more than one female and egg masses with eggs. Typical giant cells with a granular cytoplasm and many hypertrophied nuclei were observed in histological preparations. The relationship between initial nematode population density (Pi) and pepper plant growth was tested in greenhouse experiments with inoculum levels that varied from 0 to 64 eggs and second-stage juveniles (J₂) ml⁻¹ soil. A Seinhorst model was fitted to plant height and top fresh weight data of inoculated and non-inoculated plants. The tolerance limit with respect to plant height and fresh top weight of pepper to M. incognita was estimated as 0.85 eggs and J₂ ml⁻¹ soil. The minimum relative values (m) for plant height and top fresh weight were 0.15 and 0.16, respectively, at Pi ≥ 64 eggs and J₂ ml⁻¹ soil. The maximum nematode reproduction rate (Pf/Pi) was 315.4 at an initial population density (Pi) of 4 eggs and J₂ ml⁻¹ soil. The obtained results could be used as a base to establish field experiments that allow strategies to prevent surpassing the threshold of nematodes in fields that are infested.     

Failure to detect highly resistant strains in dicarboximide resistant field populations of Botrytis cinerea1

Field isolates of Botrytis cinerea with moderate levels of resistance to dicarboximide fungicides (ED50 1.0–4.9 μg ml^?1) and to dicloran were obtained from glasshouses where vinclozolin and iprodione failed to control grey mould. From sensitive and moderatcly-resistant cultures, laboratory isolates were selected on dicarboximide-amended medium, which were highly resistant to these fungicides (ED50 125->3000 μg ml^?1). Conidia of all the resistant isolates germinated well on media amended with 100 μg ml^?1 of the dicarboximides vinclozolin, iprodione, procymidone and myclozolin and with 5 μg ml^?1 of metomeclan. However, the spores of the moderately resistant isolates did not germinate on 100 μg ml^?1 metomeclan while the spores of the highly resistant isolates germinated well. Using media with 100 μg ml^?1 of metomeclan to distinguish between the two phenotypes, no highly resistant strain was detected among 312 resistant samples from five cucumber glasshouses with a high frequency of moderately resistant strains. From air-borne inoculum of five glasshouses with 100% resistant populations, 1604 colonies were recovered on vinclozolin-amended (100 μg ml^?1) medium and none on metomeclan-amended (100 μg ml^?1) medium. It is concluded that strains of B. cinerea highly resistant to dicarboximides are absent from field populations.     

Simultaneous determination of benzimidazole fungicides by HPLC on apples,pears and their pulps

The simultaneous HPLC determination of carbendazim, thiabendazole and thiophanate-methyl in apples, pears and their pulps is described. The method is based on a clean-up procedure carried out on an Extrelut 20 cartridge followed by HPLC analysis on a Diol column using hexune+isopropanol as mobile phase. Average recoveries of 83.8% for carbendazim, 82.9% for thiabendazole and 68.8% for thiophanate-methyl on apple matrix were obtained; recoveries on pear matrix were in the same range. Detection limits with UV detection at 285 nm of 100 ng ml^?1 for carbendazim, 140 ng ml^?1 for thiabendazole and 500 ng ml^?1 for thiophanate-methyl were achieved.     

Factors affecting the biological efficiency of small pesticide droplets against Tetranychus urticae eggs

Using monosized oil-based droplets of dicofol against Tetranychus urticae eggs on 1 cm² discs of bean leaf, the effects of varying droplet diameter (18–146 μm) and concentration of active ingredient (0.5–40 g litre^?1) on egg mortality were investigated. A positive curvilinear relationship was found between the spacing of droplets required to produce 50% kill (LS₅₀) and the original diameter of the droplet, D, such that: where b varied from 0.65 to 1.44 and bore a U-shaped relationship to concentration. Thus, there was an optimum concentration of about 10 g litre^?1, with control efficiency reducing as much as nine times at the extreme concentrations, and even more from the smallest to the largest droplets. The theoretical, practical and economic implications are discussed.     

Pathogenicity and host‐parasite relationships of the root‐knot nematode Meloidogyne incognita on celery

Pathogenicity and host‐parasite relationships in root‐knot disease of celery (Apium graveolens ) caused by Meloidogyne incognita race 1 were studied under glasshouse conditions. Naturally and artificially infected celery cv. D’elne plants showed severe yellowing and stunting, with heavily deformed and damaged root systems. Nematode‐induced mature galls were spherical and/or ellipsoidal and commonly contained more than one female, males and egg masses with eggs. Feeding sites were characterized by the development of giant cells that contained granular cytoplasm and many hypertrophied nuclei. The cytoplasm of giant cells was aggregated along their thickened cell walls and consequently the vascular tissues within galls appeared disrupted and disorganized. The relationship between initial nematode population density (Pi) and growth of celery plants was tested in glasshouse experiments with inoculum levels that varied from 0 to 512 eggs and second‐stage juveniles (J₂) mL^?1 soil. Seinhorst's model y = m + (1 – m)z^P–T was fitted to height and top fresh weight data of the inoculated and control plants. The tolerance limit with respect to plant height and fresh top weight of celery to M. incognita race 1 was estimated as 0·15 eggs and J₂ mL^?1 soil. The minimum relative values (m) for plant height and top fresh weight were 0·37 and 0·35, respectively, at Pi ≥ 16 eggs and J₂ mL^?1 soil. The maximum nematode reproduction rate (Pf/Pi) was 407·6 at an initial population density (Pi) of 4 eggs and J₂ mL^?1 soil.     

Influence of common carp on apple snail in a rice field evaluated by a predator - prey logistic model

The hypothesis that common carp can be used for the control of apple snails in rice fields was tested experimentally. In a rice field, 12 plots of 4 2 5 m were set and enclosed by plastic walls to prevent snail emigration and immigration. The experiment continued from June to September. Three replicated treatments were used for the plots: zero, four and 12 carp were released, giving carp densities of 0.0, 0.2 and 0.6 m^?2, respectively. Snail densities were estimated by the Jolly-Seber mark-recapture method. Newly laid egg masses were counted and measured for size, and hatching was monitored. The numbers of eggs per egg mass (y) were estimated using a regression equation obtained from the product of the maximum length and width of the egg mass (x): y =0.10x^1.24. Using these measures and the monthly mean hatching rate obtained from eggs laid in two outdoor aquaria from April to September, the number of hatched eggs was used to estimate the birth rate over a given time. A logistic model incorporating these estimates revealed that the snail population proliferated only in the zero-carp plot throughout the experiment. The study, together with other reports on snail longevity, predicts that a snail population would be eliminated in 2 years at a stocking density of 2000 carp hectare^?1, if no immigration of the snail occurred.     

Disposition kinetics of cypermethrin and fenvalerate in black bengal lactating goats

Disposition kinetics of cypermethrin and fenvalerate were investigated in lactating black Bengal goats following single dose intravenous administration at 57 and 45 mg kg^?1 respectively. The maximum and minimum blood concentrations of cypermethrin were 18.49 (±3.17) and 0.06 (±0.002) μg ml^?1, while the corresponding values for fenvalerate were 14.58 (±2.37) and 0.04 (±0.005) μg ml^?1 respectively. Both cypermethrin and fenvalerate remained present in blood for 36 h. The mean t1/2β) and Vd_area values were 5.56 (±0.28) h and 10.38 (±2.20) litre kg^?1 for cypermethrin and 5.66 (±0.35) h and 11.31 (±2.20) litre kg^?1 respectively for fenvalerate. Both cypermethrin and fenvalerate persisted in goat milk for 36 h. The t1/2β) and AUC values of fenvalerate were 7.37 (±1.84) h and 122.38 (±11.65) μg h ml^?1 whilst the corresponding values for cypermethrin were 6.66 (±1.54) h and 99.48 (±7.81) μg h ml^?1 in milk respectively.     

Effects of some foliar fungicides on the chrysomelid beetle Gastrophysa polygoni (L.)

The effects of the fungicides benomyl, thiophanate-methyl and triadimefon on the chrysomelid beetle Gastrophysa polygoni were investigated in the laboratory. Contact with a suspension of benomyl (1.5 g a. i. litre^?1 did not affect the hatchability of the eggs. Larvae were reared on shoots of knotgrass (Polygonum aviculare) that had been sprayed with suspensions of benomyl, ranging in concentration from 0.1 to 5.0 g a. i. litre^?1. The mortality to the adult stage, of larvae reared on shoots treated with concentrations of benomyl of 0.5 g a. i. litre^?1 and above, was significantly higher than that of control larvae. At concentrations of 2.0 g a. i. litre^?1 and above, no larvae survived to the adult stage. The LD₅₀ was 0.78 g a. i. benomyl litre^?1. The LT₅₀ values at concentrations of 1.0, 2.0 and 5.0 g a. i. benomyl litre^?1 were 22.6, 12.6 and 5.3 days, respectively. The mean weights of adults bred from larvae that had been reared on shoots treated with benomyl (0.5 and 1.0 g a. i. litre^?1) were significantly less than those of adults bred from control larvae. The mortality of larvae, reared on shoots of P. aviculare treated with triadimefon (0.5 g a. i. litre^?1) or thiophanate-methyl (1.0 g a. i. litre^?1), was also significantly higher than that of control larvae. Females kept on plants of P. aviculare treated with benomyl (1.5 g a. i. litre^?1) laid similar numbers of eggs to those kept on untreated plants, and the hatchability of the eggs was not affected.     

Biological activity of neem seed kernel extracts and synthetic azadirachtin against larvae of Plutella xylostella L

The activity of two neem extracts, AZT and NEEM-AZAL (containing 30 and 3 mg azadirachtin ml^?1 respectively) and synthetic azadirachtin (AZ) against second-instar larvae (L2) of Plutella xylostella L. was examined using leafdip bioassays. On Chinese cabbage, AZ was significantly (P <0.05) less toxic (3 to 4-fold; LC₅₀ 0.54 μg AZ ml^?1) than either neem extract against a laboratory strain of P. xylostella (FS). The LC₅₀ values for AZT against the FS and another laboratory strain (Wellcome) were not significantly different on Chinese cabbage. The activity of AZT against the FS and Wellcome strains was similar on Chinese cabbage and Brussels sprout. AZT was significantly less toxic (3-fold) on Brussels sprout against an acylurea-resistant field strain (Sawi) when compared with the FS strain on Chinese cabbage. Larval mortality (at day 13) was found to increase with increasing exposure time of P. xylostella (FS) larvae to AZT-treated Chinese cabbage, although there was little difference in mortality between 48 and 120 h exposure. When AZT, NEEM-AZAL and AZ were applied at a dose (1 μg AZ ml^?1) which gave end-point mortalities between 50 and 90% (at day 13), all treatments delayed the development of a proportion of surviving larvae but no morphogenetic abnormalities were observed in larvae which reached pupation. Evidence for antifeedant (reduced weight gain) and repellant effects (choicechamber) for AZT were observed with L2 P. xylostella (Wellcome) on Chinese cabbage. AZT was also shown to have ovicidal activity against P. xylostella (Wellcome) at relatively high dose ranges (10-1000 μg AZ ml^?1) as well as some contact activity (FS strain) in topical bioassays. In residual bioassays on glass with adults of the hymenopteran endo-larval parasitoid of P. xylostella, Diadegma semiclausum (Ichneumonidae), AZT showed little or no activity at rates up to 1000 μg AZ ml^?1. In medium-volume (MV, 200 litre ha^?1) and ultra-low-volume (c. 1 litre ha^?1) spray bioassays on Brussels sprout, AZT gave 16-92% and 88-100% mortality respectively (Wellcome strain) at rates approximating to 1-20 g AZ ha^?1. The residual activity of AZT and NEEM-AZAL against P. xylostella (FS) on Brussels sprout (MV spray) was observed to decrease appreciably after three days, the decline in activity being particularly marked for NEEM-AZAL.     

Laboratory studies on benzimidazole resistance in Septoria tritici1

A technique is described for testing isolates of Septoria tritici from winter wheat for resistance to benzimidazole fungicides. Secondary spores from 23 isolates were tested on Czapek Dox V-8 agar amended with benomyl at 1–10 μg ml. Twenty-one isolates were recovered from eight crops in England in 1984 and two (PBI isolates) were obtained in 1973. Thirteen isolates, including both PBI isolates, were sensitive to benomyl at 1 μg ml^?1 and nine were resistant at 10 μg ml^?1. The remaining isolate had a low proportion (1:3.7 x 10⁴) of resistant spores. The minimum inhibitory concentration for sensitive isolates was 0.2–0.4 μg ml ¹ benomyl and for resistant isolates was more than 1000 μg ml ¹. Benomyl-resistant isolates were cross-resistant to carbendazim, thiabendazole and thiophanate-methyl, but not to 12 other fungicides with different modes of action. The implications of these findings are discussed.     

Biological Control of Sclerotinia Diseases of Rapeseed by Aerial Applications of the Mycoparasite Coniothyrium minitans

Indoor and field experiments were conducted to evaluate the efficacy of applying the mycoparasite Coniothyrium minitans to the aerial parts of rapeseed plants at the flowering stage to control sclerotinia diseases caused by Sclerotinia sclerotiorum. Under controlled conditions, a petal inoculation technique was used to determine the effect of conidial suspensions of C. minitans on suppression of sclerotinia leaf blight. Results showed that C. minitans was effective in inhibiting infection initiated by ascospores of S. sclerotiorum on flower petals by restricting mycelial growth of the pathogen. Suppression of lesion development was related to the conidial concentration of C. minitans, with larger lesions at low concentration (5×10³conidia ml⁻¹), but smaller lesions at high concentration (5×10⁴ conidia ml⁻¹ or higher). When C. minitans-treated rapeseed leaves were inoculated with mycelia of S. sclerotiorum, C. minitans failed to prevent infection of leaves, but caused a significant reduction in number of sclerotia produced on the diseased leaves. No significant difference in efficacy was detected between the two isolates of C. minitans, LRC 2137 and Chy-1, on the two rapeseed cultivars, Westar (spring type) and Zhongyou 821 (winter type). Results of field trials showed a significant reduction of stem rot of rapeseed in four (1997, 1999, 2003 and 2004) out of five years by aerial application of C. minitans, compared with controls. No significant difference in suppressive efficacy was observed between the treatments of C. minitans (10⁶ conidia ml⁻¹), C. minitans (10⁶ conidia ml⁻¹) + benomyl (50 μg ml⁻¹) and benomyl (100 μg ml⁻¹) in 2003, and between the treatments of C. minitans (10⁶ conidia ml⁻¹), C. minitans (10⁶ conidia ml⁻¹) + vinclozolin (100 μg ml⁻¹) and vinclozolin (500 μg ml⁻¹) in 2004. Sclerotia of S. sclerotiorum collected from diseased plants in plots treated with C. minitans in 1999, 2000 and 2003, or with C. minitans + benomyl in 2003 were infected by C. minitans at frequencies ranging from 21.3 to 54.5%. This study concludes that aerial spraying of C. minitans is an effective method for controlling sclerotinia diseases of rapeseed.     

The role of ferrous ions in the rapid degradation of oxamyl,methomyl and aldicarb in anaerobic soils

The carbamoyloxime pesticides methomyl, oxamyl and aldicarb, together with the oxidation products of aldicarb, are known to break down much more rapidly in certain anaerobic subsoils than in the aerobic topsoils from the same site. Ferrous ions have now been shown to be involved in this reaction. Oxamyl was degraded in aqueous solutions at 30°C containing 250 μg ml^?1 Fe²⁺ with a half-life of about 10 h, independent of pH in the range of 5.65–7.66; the observed products of this reaction were N,N-dimethyl-l-cyanoformamide and methanethiol. These same products, rather than the oximino hydrolysis product observed from degradation in aerobic soils, were rapidly and quantitatively formed from oxamyl in suspensions of anaerobic reduced subsoils (Fe²⁺ concentration 27–41 μg ml^?1 soil water), but oxamyl was rather stable in water-saturated Vredepeel subsoil (Fe²⁺ concentration 0.65 μg ml^?1) in which the redox potential was much higher. Methomyl behaved similarly. The rates of reaction in the suspensions of anaerobic subsoils were greater than expected from the concentrations of Fe²⁺ in the soil water, but most of the Fe²⁺ present in soil was bound to the soil particles by cation exchange and this bound Fe²⁺ may have participated. Breakdown of aldicarb was accelerated both in solutions of Fe²⁺ and in the suspensions of anaerobic reduced subsoils, though the rate enhancement was less than observed with methomyl and oxamyl; 2-methyl-2-methylthiopropionitrile and 2-methyl-2-methylthiopropionaldehyde were the observed products from aldicarb in anaerobic soil but only the former was produced in Fe²⁺ solutions; the corresponding nitriles and aldehydes were also yielded by aldicarb sulphoxide and aldicarb sulphone in the anaerobic, reduced subsoils.     

Toxico‐kinetics,recovery efficiency and microsomal changes following administration of deltamethrin to black Bengal goats

A study of the toxico‐kinetics, recovery percentage from different substrates, cytotoxicity and role of cytochrome P₄₅₀ and b₅ of liver microsome in the metabolism of deltamethrin were carried out in female black Bengal goat. The ALD₅₀ value of deltamethrin in goat by intravenous route lies between 0.2 and 0.6 mg kg^?1. Intravenous disposition kinetics using a dose of 0.2 mg kg^?1 showed that the maximum blood concentration of deltamethrin was recorded at 0.5 min, followed by rapid decline, and a minimum concentration was detected at 6 min after administration. The following values were obtained : Vd_area 0.148 (± 0.02) litre kg^?1; t_1/2 (α) 0.22 (± 0.02) min; t_1/2 (β) 2.17 (± 0.37) min; K_el 1.05 (± 0.24) min^?1; AUC 4.30(± 0.45) µg min ml^?1; Cl_B 0.05 (± 0.006) litre kg^?1 min^?1; T～B 1.93 (± 0.58); fc 0.40(± 0.05). After 10 min, liver retained the maximum residue, and heart, adrenal gland, kidney, spleen, fat and brain also held the insecticide; liver, fat, heart and spleen retained residue after 30 min, and bone, liver and fat retained residue after 60 min of intravenous administration. Oral absorption of deltamethrin was poor and inconsistent, and approximately 65% of administered dose was recovered from faeces and gastrointestinal contents. The excretion of deltamethrin through urine was meagre, and only 0.01 and 0.013% of the administered dose was recovered after 3 and 5 days of oral administration respectively. All the tissues retained the residue after 3 days; while fat, rumen, reticulum, omasum, abomasum, large and small intestine and bone retained the residue after 5 days of oral administration; and the percentage recoveries were 1.73 and 0.027 respectively. Deltamethrin reduced the level of cytochrome P₄₅₀ content of liver microsomal pellet of goat after 5 days of oral administration. Histopathological examination of liver, kidney, heart, spleen brain and lung sections of treated goats did not reveal any pathological changes. © 2001 Society of Chemical Industry     

Effect of propiconazole on growth and sterol biosynthesis by Sclerotium rolfsii

Germination of sclerotia ofSclerotium rolfsii on agar nutrient medium was delayed or slightly inhibited by concentrations of propiconazole between 0.4 and 4.0 μg ml^?1, but was strongly inhibited by 8 μg ml^?1 and completely inhibited by 16 μg ml^?1. On the other hand, growth of hyphae from the germinated sclerotia was strongly inhibited by propiconazole at 1 μg ml^?1 or greater. Hyphal growth from agar discs on agar medium was about 8 times less sensitive than hyphal growth from the sclerotia or from hyphal inoculum in liquid media. Propiconazole at 0.25 and 1.0 μg ml^?1 strongly inhibited ergosterol biosynthesis, but this was not associated with large accumulations of C-14 methyl sterols. The ratio of eburicol to ergosterol in hyphae grown in the presence of 0.25 μg ml^?1 propiconazole for 16, 30 or 45 h was 0.11, 0.13 and 0.04, respectively, for the three intervals while for hyphae grown in the presence of 1 μg ml^?1, the ratios were 0.29, 0.36 and 0.30, respectively, for the same intervals. In view of a ratio of 23.5 for¹⁴C-acetate incorporation into the two sterols during the initial 6 h growth period in the presence of propiconazole, it is believed that the lack of large accumulation of C-14 methyl sterols is due to the feedback inhibition by eburicol or to cell lysis when the content of ergosterol becomes too low in the actively growing cells.     

Adsorption-leaching study of the herbicides metamitron and chloridazon

Freundlich isotherms were obtained for the adsorption equilibrium of the herbicides metamitron and chloridazon with the components of a representative soil in a pesticide concentration range of 10-1000 γg ml^?1 for metamitron and 10-500 μg ml^?1 for chloridazon. The mobility of these herbicides through soil columns was also studied using the displacement technique described by Davidson (Soil Sci. Soc. Amer. Proc., 32 (1968) 629). The experiment was carried out simultaneously in three columns, two of which were fed with solutions of the herbicides while the third was used as a control. The herbicide solutions flowed down by gravity and were collected at the outlet at different times. The herbicide content of these outlet solutions was determined by Differential Pulse Polarography.     

The metabolism in the rat of the herbicidally active isomer (R)- flamprop-methyl in comparison with the racemic form

A single dose (4 mg kg^?1) of ¹⁴ C-labelled (R)-flamprop-methyl to rat was rapidly metabolised and 90% of the dose was eliminated in urine and faeces within 48 h. Four days after dosing, tissue residues were 0–1 μg equivalents g^?1 tissue or much less, with the exception of kidney (0–22 μg g^?1). There was a statistically significant sex difference in the routes of elimination; this may be attributed to differences in the biliary elimination of the major metabolite, flamprop acid, or its glucuronide conjugate. The fate of racemic flamprop-methyl was very similar to that of the (R)-isomer. The major metabolic routes were hydrolysis of the esters to the corresponding acids, hydroxylation of the benzoyl aromatic rings and conjugation. The flamprop acid derived from the (R)-flamprop-methyl was found to be partially converted to the (S)-form (R:S ratio, 87:13). This reaction is discussed in the context of other such biological racemisations recently reported.     

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).     

Effect of pyriproxyfen,a juvenile hormone mimic,on egg hatch,nymph development,adult emergence and reproduction of the Asian citrus psyllid,Diaphorina citri Kuwayama

BACKGROUND: The Asian citrus psyllid (ACP), Diaphorina citri Kuwayama, is a vector of bacteria presumably responsible for huanglongbing (HLB) disease in citrus. In this laboratory study, an investigation was made of the activity of pyriproxyfen, a juvenile hormone mimic, on ACP eggs, nymphs and adults to evaluate its potential as a biorational insecticide for inclusion in an integrated pest management (IPM) program for ACP. RESULTS: Irrespective of egg age, timing or method of treatment, a significantly lower percentage of eggs (5–29%) hatched after exposure to 64 and 128 µg mL^?1 of pyriproxyfen. Only 0–36% of early instars (first, second and third) and 25–74% of late instars (fourth and fifth) survived to adults following exposure to 16, 32 and 64 µg mL^?1 of pyriproxyfen. However, 15–20% of adults that emerged following treatment as late instars exhibited morphological abnormalities. Furthermore, pyriproxyfen adversely affected reproduction (fecundity and fertility) of adults that emerged from treated fifth instars or that were treated topically with 0.04 µg as adults. CONCLUSIONS: Application of pyriproxyfen at 64 µg mL^?1 resulted in greater inhibition of egg hatch and suppression of adult emergence compared with lower rates. Pyriproxyfen also markedly reduced female fecundity and egg viability for adults that were exposed either as fifth instars or as newly emerged adults. The ovicidal, larvicidal and reproductive effects against ACP suggest that pyriproxyfen is suitable for integration into an IPM program for ACP. Copyright © 2009 Society of Chemical Industry