Effect of short exposures to a high concentration on the subsequent toxicity of low concentrations of methyl bromide to diapausing larvae of the warehouse moth,Ephestia elutella (Hübner)

Ephestia elutella larvae in diapause were exposed at 25°C to methyl bromide at 12 mg litre^?1 for 3.5 or 7.5 h and then immediately exposed to a lower concentration. The minimum effective concentration (that at which Haber's rule, concentration × time = k, a constant for mortality, still applied) was about 3 mg litre^?1 in tests with no previous exposure toa high concentration, but it was about 2.5 mg litre^?1 for individuals surviving a 3.5 h exposure to 12 mg litre^?1, and was about 1.6 mg litre^?1 for those surviving a 7.5 h exposure to 12 mg litre^?1. These exposures to 12 mg litre^?1, respectively, killed 2–20% and 50–75% of larvae exposed, and hence the smaller the proportion of survivors of exposure to a high concentration, the lower the minimum effective concentration needed against them. Thus the low concentration persisting at the end of a practical fumigation should contribute significantly to the success of the treatment and be much more effective than any similar low concentration present soon after the introduction of gas.     

Pesticidal properties of parthenin (from Parthenium hysterophorus) and related compounds

Eleven sesquiterpene lactone derivatives of parthenin ( 1 ), obtained from wild feverfew, Parthenium hysterophorus, were prepared by chemical and photochemical transformations. The compounds tested were a pyrazoline adduct ( 2 ) of parthenin, its cyclopropyl ( 3 ) and propenyl ( 4 ) derivatives, anhydroparthenin ( 5 ), a dihydro‐deoxygenated product ( 6 ), a formate ( 7 ) and its corresponding alcohol ( 8 ) and acetate ( 9 ), a rearranged product ( 10 ), lactone ( 11 ) and hemiacetal ( 12 ). All these derivatives, along with parthenin, were tried for their antifeedant action against sixth‐instar larvae of Spodoptera litura, for insecticidal activity against the adults of store grain pest Callosobruchus maculatus, for phytotoxic activity against Cassia tora, and for nematicidal activity against the juvenile stage‐II (J₂) of the root knot nematode Meloidogyne incognita. Antifeedent bioassay revealed that parthenin is moderately antifeedant. Among the derivatives, the saturated lactone ( 11 ) was found to be about 2.25 times more active than parthenin. The pyrazoline adduct ( 2 ) was found to be the most effective as an insecticide, with LC₅₀ values after 24, 48 and 72 h of 96, 43 and 32 mg litre⁻¹, respectively, which are comparable with neem extract. Compound 4 was found to be the most effective inhibitor of germination and seedling growth of C tora, with ID₅₀ values for germination, plumule length and radicle length of 136, 326 and 172 compared with 364, 738 and 427 mg litre⁻¹, respectively, for parthenin. Compound 10 was found to be the most effective in terms of nematicidal activity. The LC₅₀ values for this compound were 273 and 104 mg litre⁻¹, respectively, after 48 and 72 h compared with 862 and 512 mg litre⁻¹ observed for parthenin after 48 and 72 h. © 2001 Society of Chemical Industry     

Laboratory Evaluation of the Novel Naturally Derived Compound Spinosad against Ceratitiscapitata

Laboratory studies were conducted to determine the effect of the naturally derived compound spinosad on Ceratitis capitata Wied. (Diptera, Tephritidae). The organophosphate fenthion was used as a standard. Direct dose-dependent mortality and reduced fecundity were observed in oral treatment of adults with spinosad. The LC₉₀ values 14 h and seven days after treatment were 19·50 and 0·49 mg litre⁻¹ respectively. Fenthion was less active (the LC₅₀ eight days after treatment was 1·17 mg litre⁻¹) and did not affect the fecundity of the fly. Adults were also very susceptible to spinosad and fenthion via residual contact. For spinosad, 100% mortality was recorded 48 h after treatment for a dose of 10 mg litre⁻¹. Spinosad was more effective than fenthion in suppressing larval development when neonate larvae were reared on treated diet supplemented with a range of concentrations from 0·02 to 0·83 mg kg⁻¹ diet. Last-instar larvae were much less susceptible to spinosad or fenthion when exposed via dipping or when they pupated in treated medium and both products had similar performance. A lack of ovicidal activity was observed in direct egg-treatments with spinosad but significant reductions from 1 mg litre⁻¹ onwards were recorded for fenthion.     

Toxicity of phosphine to five species of stored-product insects in atmospheres of air and nitrogen

The responses of five species of adult stored-product insects [Tribolium castaneum (Herbst), T. confusum (DuVal), Rhyzopertha dominica (F.), Sitophilus oryzae (L.) and S. granarius (L.)] to various doses of phosphine in atmospheres of air or nitrogen were determined. A few S. oryzae and S. granarius survived phosphine concentrations up to 80 mg litre^?1 for 24 h in normal (air) or nitrogen atmospheres. By contrast, T. castaneum, T. confusum and R. dominica could not tolerate more than 0.2 mg phosphine litre^?1 in air for 12 h. However, they could tolerate up to 10 mg phosphine litre^?1 in nitrogen for that period. Increasing the phosphine concentration resulted in increased mortalities of the last three species. The possible mechanism underlying this response is discussed. The reproductive potential of insects surviving phosphine exposure in a nitrogen atmosphere was unaffected.     

Depression of the minimum concentration of methyl bromide effective against diapausing warehouse moth larvae at 15°c by prior exposure at a moderate concentration

Warehouse moth (Ephestia elutella) larvae in diapause were exposed at 15°C to methyl bromide at 8 mg litre^?1 for 14.5 h and then immediately exposed at a lower concentration. The exposure at 8 mg litre^?1 killed 44–69% of the larvae treated. Subsequent concentrations down to 1.1 mg litre^?1 obeyed Haber's rule (concentration × time= k, a constant for mortality), but a higher concentration-time product (ct) was required for over 90% kill at 0.8 mg litre^?1. Only concentrations down to 1.9 mg litre^?1 obey Haber's rule if there is no prior exposure at a higher concentration. Although minimum effective concentrations are lower at 15°C than at 25°C, exposure at a higher concentration depresses the subsequent level to a similar extent at each temperature. The contribution to the efficacy of a treatment, of low concentrations persisting at the end of fumigation, is thus likely to be even greater at moderate to low temperatures than at 25°C. The implications for the development of resistance to methyl bromide are discussed.     

Effect of temperature on the toxicity of low concentrations of methyl bromide to diapausing larvae of the warehouse moth Ephestia elutella (Hübner)

The performance of low concentrations of methyl bromide against diapausing larvae of Ephestia elutella at 15 and 25°C was assessed in extended exposure periods. At concentrations of 1.9 mg litre^?1 and below, test batches required higher concentration-time (ct) products for 100% kill at 25°C than at 15°C. The minimum concentration at which the concentration: time relationship still applied was between 1.3 and 1.9 mg litre^?1 at 15°C, whereas at 25°C it was between 2.7 and 4.0 mg litre^?1. For many individuals within each population sample, however, lower concentrations at moderate dosage levels remained lethal. At 25°C, a ct product of about 90 mg litre^?1 h gave between 53 and 77% kill at 6.1, 4.0, 2.7 and 1.9 mg litre^?1. The trends observed suggest that the most tolerant members of the population have an enhanced ability to detoxify methyl bromide at the higher temperature. The implications of the results for the build-up of resistance and for practical control measures are discussed.     

A monoclonal antibody‐based ELISA for the analysis of the insecticide flucythrinate in environmental and crop samples

A competitive enzyme‐linked immunosorbent assay (ELISA) has been developed for the detection of the insecticide flucythrinate in environmental and food samples. Two types of haptens, the acid moiety that is the hydrolyzed product of flucythrinate, and the carboxylated propyl derivative of the alcohol moiety, were used to prepare monoclonal antibodies (MAbs). Five MAbs, which raised against the former hapten, were reactive with flucythrinate. Among them, MAb F1A27‐4 showed the highest activity toward flucythrinate, and did not cross‐react with other pyrethroids such as cycloprothrin, fenvalerate, fluvalinate, etofenprox and silafluofen. The assay conditions of indirect competitive ELISA with MAb F1A27‐4 were studied to optimize the detection of flucythrinate in environmental and food samples. Incubation at 4 °C in the assay buffer, pH 8, with 300 mM sodium chloride improved the sensitivity. The addition of rabbit serum albumin or rabbit antiserum and the presence of 50 ml litre^?1 of methanol reduced matrix effects of the samples. Under optimized conditions, the ELISA detected flucythrinate spiked in water, soil, and extracts of apple and tea samples down to 10 mg litre^?1, 0.2 mg litre^?1, 0.3 mg litre^?1 and 0.3 mg litre^?1, respectively. The mean recovery and CV ranged from 91% to 120% and from 5% to 12%, respectively. The ELISA results in apple samples correlated well with those from LC–MS analysis (r² = 0.99, n = 12). © 2001 Society of Chemical Industry     

Uptake of aminotriazole from humectant-surfactant combinations and the influence of humidity

Uptake of aminotriazole (3-amino-1,2,4-triazole) by bean leaves (Phaseolus vulgaris var. Canadian Wonder) was not greatly influenced by the addition to the spray solution of dimethylformamide (DMF), ethylene glycol and polypropylene glycol 400 (PPG 400) over the concentration range 1.0–50.0 ml litre^?1. However, the addition of polyoxyethylene 20 sorbitan monolaurate (polysorbate 20) (0.2–1.0 g litre^?1) to spray solutions of the above additives and glycerol (5.0 ml litre^?1; except for DMF, 50.0 ml litre^?1) substantially increased uptake to 80–100% in all cases at 50 ± 10% relative humidity (r.h.). Similar penetration figures were recorded when a range of polysorbate surfactants (polysorbate 20, 40, 60, 80 and 85; 0.2 g litre^?1) were applied to spray solutions containing either dimethyl sulphoxide (DMSO) or glycerol (5.0 ml litre^?1). Humidity was found to have a critical effect upon the humectant-surfactant combinations tested, i.e. DMSO + polysorbate 20, ethylene glycol+ polysorbate 20 and PPG + 400-polysorbate 20 (5.0 ml litre^?1+0.2 g litre^?1). With DMSO + polysorbate 20 the following uptake figures were recorded: < 30% r.h., 3.1 %; 45 ± 10% r.h., 86.8%; 55–65% r.h., 48.2 % and 100% r.h., 0.3%. Similar trends were recorded with all three humectant-surfactant combinations. Further studies revealed that the adverse effect of humidity on DMSO-polysorbate mixtures could be at least overcome partially by regulating the DMSO concentration.     

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.     

Eradication of over-wintering mildew (Podosphaera leucotricha) in apple buds by nitrogen-containing surfactants

The eradicant activities of 24 nitrogen-containing preparations, comprising primary, secondary or tertiary amines, amine acetates, diamines, amine oxides or quaternary ammonium salts, were assessed in trials with potted dormant apple rootstocks, heavily infected with the powdery mildew fungus Podosphaera leucotricha. The surfactants consisted of mixtures in which C₁₂/C₁₄ or C₁₆/C₁₈ alkyl or alkenyl compounds predominated. Of the amine acetates (at 50g litre^?1), only the formulation containing C₁₂/C₁₄ primary amine acctates was considered worthy of further evaluation. Some amine oxides and quaternary ammonium compounds (at 35 g litre^?1) were good eradicants and were as effective as ‘PP222’ a (nonylphenol-ethoxylate mixture) which was included for comparison. All the compounds showing good activity contained one C₁₂/C₁₄ alkyl group whereas C₁₆/C₁₈ compounds, whether saturated or unsaturated, were relatively inactive. In a field trial, C₁₂/C₁₄ (dimethyl) amine oxide, C₁₂/C₁₄bis (2-hydroxyethyl) amine oxide, and C₁₂/C₁₄ amine acetate (35 g litre^?1) greatly reduced the amount of primary mildew on trees that were previously heavily infected, but there were signs that the fruit yield was reduced.     

Comparative fungitoxicity of the insecticide permethrin and ten degradation products

The toxic effects of permethrin and ten of its degradation products on the growth of ten fungi were determined. Permethrin was relativelynon-toxic, with an EC₅₀ of > 100 mg litre^?1 but six of the degradation products were significantly (P= 0.05) more inhibitory. The ester hydrolysis products, 3-phenoxybenzyl alcohol and 3-(2,2-dichlorovinyl)-2,2-dimethylcyclopropanecarboxylic acid, had EC₅₀ values ranging from 8 to > 100 and 20 to > 50 mg litre^?1, respectively. Other degradation products that were more toxic than permethrin included 3-phenoxybenzaldehyde and 3-phenoxybenzoic acid, with EC₅₀ values as low as < 1 mg lite^?1. Hydroxylated and substituted-benzene metabolites were non-toxic. Combinations of selected test compounds yielded both synergistic, antagonistic and additive interaction responses, depending upon the test system employed.     

Effect of fipronil seed treatments on the germination and early growth of rice

Fipronil seed treatments were evaluated to determine whether they directly influence germination and subsequent seedling growth in rice (Oryza sativa L). Continuous seed exposure to fipronil (four days) at 2 000 mg litre⁻¹ significantly impaired germination (P < 0.001). When exposure was restricted to a 1-h period 48 h after the initiation of germination, early post-germination growth was also impaired (assessment two days after exposure, P < 0.05). The proportion of seeds satisfying our criteria for normal germination fell by 2.3 and 2.6% respectively across 17 cultivars. Cultivar effects were highly significant (P < 0.001). When exposure to fipronil (2 000 mg litre⁻¹) was restricted to 2 h at initial seed wetting no significant growth impairment occurred. No significant differences (P > 0.05) were found between shoot lengths or root system dry weights of control plants and plants developing from seed exposed continuously (two days) to fipronil at rates of up to 2 000 mg litre⁻¹ during germination and harvested nine days after sowing. Treating germinated seed with fipronil for 1 h immediately prior to sowing at rates of up to 4 000 mg litre⁻¹ did not result in significant changes (P < 0.05) in plant growth parameters at either nine or 25 days after sowing. No evidence of fipronil having a direct phytostimulatory effect on rice was obtained. © 1999 Society of Chemical Industry     

The algaecidal activity of some substituted 1,3-diphenylureas, 1-phenyl-3-(2-pyridyl)ureas and the corresponding thioureas

Twelve ureas and thioureas with 1,3-diphenyl- and 1-phenyl-3-(2-pyridyl) were tested as potential herbicides in a simple screen against two species of algae Chlorella fusca and Anabaena variabilis. Several were shown to inhibit growth at 100 mg litre^?1 but only 1-[2,4-bis(azidosulphonyl)phenyl]-3-(2-pyridyl)urea and 1,3-bis(4-isopropyl- idenehydrazinosulphonylphenyl)thiourea showed any activity at 1 mg litre^?1. This compares with the well-established urea herbicide diuron which, in identical tests, gives similar inhibition of growth at concentrations as low as 0.01 mg litre^?1.     

The toxicity of cyromazine to Chironomus zealandicus (chironomidae) and Deleatidium sp. (leptophlebiidae)

The toxicity of cyromazine and a commercial formulation, ‘Vetrazin’®, to Chironomus zealandicus (thummi) Hudson and Deleatidium sp. was investigated. Under acute test conditions, the LC₅₀ values for each species were quite comparable. For C. zealandicus, the value varied according to instar, 100–400 mg litre^?1 for second- and third-instar to 1000–10000 mg litre^?1 for older fourth-instars. For the one size class of Deleatidium tested (c.10 mm long), the value was 300–400 mg litre^?1. High control mortalities of C. zealandicus limit that species' usefulness as an acute bioassay candidate. Under chronic test conditions, cyromazine showed a high toxicity to eggs or early-instar larvae of C. zealandicus. The maximum acceptable toxicant concentration for cyromazine against C. zealandicus was approximately 17.5 μg litre^?1. The possibility of water contamination at this level is discussed. Whole-of-life chronic tests with C. zealandicus indicated that the most susceptible stage was in the egg or soon after larval emergence. These results highlight the dangers of using short-term acute toxicity results to formulate environmental exposure limits for modern pesticides that do not have dysfunction of the nervous system as their mode of action.     

Movement of pesticides to surface waters from a heavy clay soil

A field experiment at Cockle Park, Northumberland on a clay loam soil (Dunkeswick series) cropped with winter wheat investigated the effects of drainage and season of application on pesticide movement. Isoproturon, mecoprop, fonofos and trifluralin were applied in two consecutive seasons at normal agricultural rates to three hydrologically isolated plots each of 0.25 ha. Two of the plots were mole-drained and the third was an undrained control. Surfacelayer flow and drainflow from each plot were monitored at 10-min intervals. Samples of flow were analysed for pesticides to evaluate transport of applied chemicals from the site. Despite widely differing properties (K_oc 20–8000 ml g^?1, t_1/2 10–60 days), all four pesticides were found in surface-layer flow and mole drainflow from the site. Maximum concentrations of pesticides in flow ranged from 0.1 to 121 μg litre^?1 (aqueous phase) and < 0.2 to 48 μg litre^?1 (particulate phase). Over two contrasting seasons, total losses of pesticides in flow followed total amounts of flow and were approximately four and five times larger, respectively, in 1990/91 than in 1989/90. The maximum loss occurred from the undrained plot and was 2.8 g isoproturon (0.45% of that applied). Total losses of autumn-applied pesticides from an undrained plot were up to four times greater than losses from a mole-drained plot. Mole drainage decreased movement of pesticides from this slowly permeable soil by reducing the amount of surfacelayer flow. Maximum concentrations of mecoprop and isoproturon in drainflow were 10–20 times larger following spring application than after application in autumn. Bypass flow down soil cracks was an important process by which pesticide was lost from the site, with transport to the drainage system via mole channels (55 cm depth) after less than 0.5 and 6.7 mm net drainage in the two winters.     

Fumigant toxicity of volatile natural products from Korean spices and medicinal plants towards the rice weevil,Sitophilus oryzae (L)

The fumigant toxicity of various volatile constituents of essential oils extracted from sixteen Korean spices and medicinal plants towards the rice weevil, Sitophilus oryzae L (Coleoptera: Curculionidae), was determined. The most potent toxicity was found in the essential oil from Mentha arvensis L var piperascens (LC₅₀ = 45.5 µl litre^?1 air). GC–MS analysis of essential oil from M arvensis showed it to be rich in menthol (63.2%), menthone (13.1%) and limonene (1.5%), followed in abundance by β‐pinene (0.7%), α‐pinene (0.6%) and linalool (0.2%). Treatment of S oryzae with each of these terpenes showed menthone to be most active (LC₅₀ = 12.7 µl litre^?1 air) followed by linalool (LC₅₀ = 39.2 µl litre^?1 air) and α‐pinene (LC₅₀ = 54.9 µl litre^?1 air). Studies on inhibition of acetylcholinesterase activity of S oryzae showed menthone to have a nine‐fold lower inhibitory effect than menthol, despite menthone being 8.1‐fold more toxic than menthol to the rice weevil. Different modes of toxicity of these monoterpenes towards S oryzae are discussed. © 2001 Society of Chemical Industry     

Uptake of phorate by lettuce

Following experimental and commercial applications to soil of a granular formulalation of phorate (O,O-diethyl S-ethylthiomethyl phosphorodithioate), residues in the soil and in lettuce were determined by gas-liquid chromatography. When applied by the bow-wave method as a continuous logarithmically-changing dose ranging from approximately 0.9 to 16.0 kg a.i. ha^?1, the proportional rate of oxidation in soil of phorate sulphoxide to phorate sulphone was inversely related to dose. Ten weeks after application, total phorate residues in the soil had declined by about 35% at all dose levels. Residues in mature lettuce, from the 1-5 kg ha^?1 dose-range, comprised the parent and oxygen analogue sulphoxides and sulphones; the relative proportions of the individual metabolites were independent of dose. Over this dose-range, total residue concentrations in the crop became proportionally slightly greater with increasing dose. When single doses of 1.1, 2.0 or 2.2 kg a.i. ha^?1 were applied at drilling, the total residue concentrations in the lettuce declined from 5 mg kg^?1 in seedlings from some treatments to <0.05 mg kg^?1 at harvest. In plants raised in peat blocks containing 10 or 20 mg a.i. per block, however, residues in seedlings totalled 45-47 mg kg^?1 and declined to only 0.7 mg kg^?1 at harvest. It was concluded that bowwave applications of phorate when field-sowing lettuce were unlikely to lead to unacceptable residues in the harvested crop, but that residues in lettuce raised in phorate-treated peat blocks may be unacceptably high.     

Fungicidal activity of the polyamine analogue,keto-putrescine

The polyamine analogue, keto-putrescine, was shown to provide substantial control of infections by six economically important plant pathogens, with EC₅₀ values ranging between 57 and 82 mg litre^?1. However, keto-putrescine was relatively less effective in vitro against Phytophthora infestans, Pyricularia oryzae and Pyrenophora avenae, with EC₅₀ values ranging from 145 to 340 mg litre^?1. In contrast, the polyamine analogue N-acetylputrescine had to effect on in-vitro growth of P. avenae or P. oryzae or infection of barley seedlings with powdery mildew. When P. avenae was grown in the presence of keto-putrescine, there were small, insignificant reductions in ornithine decarboxylase activity, with more substantial, significant reductions in S-adenosylmethionine decarboxylase activity. These changes were accompanied by a 43% reduction in spermidine concentration and increased concentrations of spermine and cadaverine.     

Efficacies of low- to high-volume (960-10 700 litre ha− 1) citrus sprayers for applying petroleum spray oil to control chinese wax scale

Petroleum spray oil (2, 4 and 6% in water) was applied to Valencia orange, Citrus sinensis (L.) Osbeck, for the control of Chinese wax scale, Ceroplastes sinensis del Guercio, using a low-volume ( <2000 litre ha^?1)air-blast (LV AB) sprayer, a low- to high-volume (L-HV) (up to 7000 litre ha^?1) sprayer with four fan-assisted rotary atomiser (FARA) spray heads mounted on a vertical tower, and a high-volume (>7000 litre ha^?1) oscillating boom (HV OB) sprayer. The most effective sprayer was the L-HV FARA sprayer. The most cost-effective treatment was a 20 ml litre^?1 (60 litre oil ha^?1) spray applied at 3000 litre ha^?1 by the L-HV FARA sprayer. It gave mortality equivalent to a standard 20 ml litre^?1, 10 700 litre ha^?1 spray (214 litre oil ha^?1) applied by the HV OB sprayer but with 72% less spray and significantly less oil deposited per cm² of leaf area. Equivalent or significantly (P = 0·05) higher mortality than that given by the 10 700 litre ha^?1 HV OB spray was given by the 40 ml litre^?1, 3000 (120 litre oil ha^?1) and 60 ml litre^?1, 2180 and 3000 litre ha^?1 (130·8 and 180 litre oil ha^?1) L-HV FARA sprays, but the 60 ml litre^?1 sprays deposited more oil per cm² than the 20 ml litre^?1 HV OB spray and were considered to be potentially phytotoxic. The least effective sprayer was the LV AB sprayer, which applied a 60 ml litre^?1 spray (57·6 litre oil ha^?1) at 960 litre ha^?1. Linear relationships were established for Chinese wax scale mortality, transformed using an angular transformation (arcsin proportion), versus log₁₀ spray volume for the 20, 40 and 60 ml litre^?1 sprays applied by L-HV FARA at 1260,2180 and 3000 litre ha^?1, mortality versus log₁₀ μg oil cm^?2 and log₁₀ μg oil versus log₁₀ volume of oil sprayed.     

Use of natural pyrethrum to control the red swamp crayfish Procambarus clarkii in a rural district of Italy

BACKGROUND: The crayfish Procambarus clarkii inflicts severe ecological and economic damages in Europe. To develop an efficient method for its control, four experiments were carried out to assess the impact of natural pyrethrum (i.e. Pyblast) on crayfish: (1) the 24 h LC₁₀₀ and LC₅₀ were quantified on crayfish; (2) the breakdown time of the 24 h LC₁₀₀ was assessed using Daphnia magna as a bioindicator; the effects of 24 h LC₁₀₀ on crayfish were investigated by applying the biocide into burrows (3) and in a drainage channel (4). RESULTS: Pyblast concentrations of 0.05 and 0.02 mg L^?1 corresponded to 24 h LC₁₀₀ and LC₅₀ respectively. The concentration of 0.05 mg L^?1 broke down after 72 h, whereas 0.02 mg L^?1 did not cause any significant mortality in D. magna after 24 h. However, 0.05 mg L^?1 had no effect on crayfish when introduced into the burrows, but led to a mortality of 95% when applied in the water. CONCLUSION: Experimental evidence is provided for the efficacy of Pyblast to control invasive crayfish. Obviously, before its use on a large scale, further studies are needed to find a concentration that will achieve the target 100% mortality with the shortest recovery time of the environment. Copyright © 2012 Society of Chemical Industry