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.     

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.     

Penetration of bean leaves by aminotriazole as influenced by adjuvants and humidity

Penetration of bean leaves (Phaseolus vulgaris var. Canadian Wonder) by aminotriazole (3-amino-1,2,4-triazole) was greatly enhanced under high humidity conditions (ca 10% in 17 h at the low humidity level (LHL) compared with ca 80% in 2 h at the high humidity level (HHL)). The addition of polyoxyethylene 20 sorbitan monolaurate (polysorbate 20) to the spray fluid increased penetration on all occasions at the LHL. The increase obtained was found to be dependent on the concentration of polysorbate 20. The inclusion of polysorbate 20 at the HHL resulted in an increase in aminotriazole penetration at low polysorbate 20 concentrations 0.2–12.8 g/litre and a non-significant decrease over the aqueous control at a concentration of 40 g/litre. With additions of glycerol to the spray fluid, aminotriazole penetration was increased on all occasions at the LHL while at the HHL no concentration of glycerol was found to enhance penetration. The addition of polysorbate 20 (< 0.1 to 40 g/litre) to a spray solution containing glycerol (0.3 ml/litre) enhanced penetration at the HHL compared with the aqueous and glycerol controls. A polysorbate 20 plus glycerol combination (6.4 g+0.6 ml/litre) gave the same order of penetration (98.4 and 94.0%) at the HHL and LHL respectively. In both cases penetration exceeded that obtained with the corresponding polysorbate 20 and glycerol controls. Some of the practical implications of these findings are discussed.     

Assessment of a mathematical model to predict spray deposition under laboratory track spraying conditions. II: Examination with further plant species and diluted formulations

Mean spray depositions onto leaves of five plant species (Zea mays L., Vicia faba L., Sinapsis alba L., Glycine max (L.) Merr, Vitis vinifera L.) were measured following spraying of an array of 36 solutions of acetone + aqueous “Triton X-100” varying systematically in composition and properties. The spraying was carried out on five occasions using a standard laboratory track sprayer delivering the equivalent of 600 litre ha^?1 onto a plane surface around plant height. The results, plotted as response surfaces, showed that there was little variation in spray deposition with solution composition for V. vinifera, there were some slight decreases in deposition with increase in “Triton X-100” concentration on V. faba and S. alba, though not with increase in acetone concentration, and that there were slight systematic increases for G. max and large systematic increases for Z. mays with increase in acetone and “Triton X-100” up to concentrations of 350 ml litre^?1 and 0.5 g litre^?1 respectively. At higher concentrations of these components, there were no further increases in deposition on these latter species. The results were in agreement with those predicted by a mathematical model derived previously, with the exception of the slight decreases in deposition on V.fana and S.alba and smaller increases in deposition than predicted on G.max. The decreases in deposition on the former species were attributed to slight run-off from their easy-to-wet leaves at the higher “Triton X-100” concentrations at the spray volume rate (600 litre ha^?1) used. The poor fit of the observed and predicted spray depositions on G. max was attributed to the nature of its leaves. These are hairy and it is speculated that the fine hairs, rather than the true leaf surface, played a major role in capturing the small spray drops (115-130 μm) created by the laboratory sprayer used in this work. The observed and predicted spray depositions with a set of diluted commercial-type formulations were in good agreement for Setaria viridis (L.) Beauv., Pisum sativum L., Z. mays, with correlation coefficients (r) of 0.985, 0.988 and 0.935 respectively, and also for the more constant depositions on the easy-to-wet species Beta vulgaris L., but slightly less so for Triticum aestivum L. (r = 0.886) in this test. Overall the model was well-behaved, giving a good prediction of the variation in spray deposition on leaves of a range of plant species, provided that these were not extensively hairy, with variation in the dynamic surface tension of the spray solution.     

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     

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.     

Teratogenic effects of the fungicide benomyl on posterior segmental regeneration in the earthworm,Eisenia fetida

Earthworms, Eisenia fetida, were treated by surface exposure to the fungicide benomyl at various stages of posterior segmental regeneration. Teratogenic effects of benomyl were observed when worms were treated 7–11 days after amputation (i.e. during the normal period of segmental replication), but not during days 1–5, 13–17, or 19–23. Teratogenic effects included a reduction in the number of regenerated segments, an increased frequency of segmental groove anomalies, and a variety of monstrosities. The effects of benomyl treatment on the number of regenerated segments and frequency of anomalies were dose-dependent within a narrow concentration range (approximately 0.2–5.0 mg litre^?1); at higher concentrations (e.g. 25 mg litre^?1) teratogenic effects were less frequent because the onset of segmental delineation was delayed until well after exposure. Non-invasive electrophysiological recordings from treated worms indicated that functional integrity of giant nerve fibre conduction pathways was established in all anomalously regenerated tail segments, except in a two-tailed monstrosity. The evidence supports the hypothesis that these teratogenic effects derive from an antimitotic mode of action of benomyl on segmental regeneration.     

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.     

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     

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     

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.     

Laboratory studies with antifeedants against larvae of Boarmia (Ascotis) selenaria on alfalfa

The antifeedant effect of five organotin compounds (fentin acetate, fentin hydroxide, fentin chloride, cyhexatin and fenbutatin oxide) and of three other compounds known to possess antifeeding activity (guazatine triacetate, 4′-chloroacetophenone isobutyrylhydrazone and thiram) was investigated by feeding treated alfalfa to larvae of Boarmia selenaria. The three fentins and cyhexatin were highly active at 0.1 g litre^?1, the order of activity at this concentration being fentin chloride > fentin hydroxide > fentin acetate ? cyhexatin, whereas the other compounds were practically inactive at either this or a somewhat higher concentration (0.5 g litre^?1). Guazatine triacetate had a concentration-independent antifeedant effect at much higher concentrations (5–20 g litre^?1).     

Morphogenetic effects of diflubenzuron,an inhibitor of chitin deposition,on the coconut black-headed caterpillar (Nephantis serinopa myer)

Feeding the last instar larvae of Nephantis serinopa, the coconut black-headed caterpillar, on coconut leaves that had been dipped in diflubenzuron suspensions (0.2-4.0 g litre^?1) and dried, inhibited the moulting process and caused morphogenetic deformities of their pupae. The inhibition of moulting ranged from 27.5 to 75% The maximum effect was produced by suspensions of 4.0 g litre^?1 when only 5% of the larvae survived to become adults against 97.5% of untreated larvae.     

Insecticidal activity of surfactants and oils against silverleaf whitefly (Bemisia argentifolii) nymphs (Homoptera: Aleyrodidae) on collards and tomato

The insecticidal activities of four surfactants (Cide‐kick, Silwet L‐77, M‐Pede and APSA‐80), a dishwashing detergent (New Day), a mineral oil (Sunspray oil), a cotton seed oil and a vegetable oil, alone or in combination, were tested against nymphs of Bemisia argentifolii Bellows & Perring on collards and tomato. Silwet L‐77 was more effective (>95% mortality) than Cide‐Kick or APSA‐80 at rates from 0.25–1.00 g AI litre⁻¹ but caused severe phytotoxicity to tender tomato leaves at all but the lowest rate. New Day dish detergent at 2.0 ml litre⁻¹ caused mortality (95%) comparable to M‐Pede insecticide soap at 10‐fold greater concentration. A New Day ingredient, cocamide DEA, was considerably more active than the other ingredients or the commercial mixture. Additional surfactants added to Sunspray oil increased efficacy in some treatments, but not others. Toxic responses of 2nd‐ and 3rd‐ instar whiteflies to vegetable oil and cotton seed oil at 5.0 and 10.0 ml litre⁻¹ plus 0.4 g AI litre⁻¹ APSA‐80 ranged from 22.1 to 79.9% and 66.3–88.7% mortality, respectively. Whitefly mortality was greater on tomato than on collard in six of seven instances when differences between host plants were significant. Our results indicate that the these surfactants and oils have good potential for controlling B argentifolii. © 2000 Society of Chemical Industry     

Influence of wetting agents on the foliar uptake and herbicidal activity of glufosinate

The influence of four different wetting agents on the foliar retention, uptake and herbicidal activity of the glutamine synthetase inhibitor, glufosinate, was examined in growth-chamber experiments on barley (Hordeum vulgare L. cv Roland) and barnyard grass (Echinochloa crus-galli (L.) P.B.) as test species. The non-formulated monoammomum salt, glufosinate-ammonium, was applied as a spray, either alone or mixed with a wetting agent. The dose rates of herbicide and wetting agent were 0.5 g a.i. litre^?1 and 2.0 g litre^?1, respectively, on barnyard grass, and 2.0 g a.i. litre^?1 and 60 g litre^?1, respectively, on barley. Herbicide damage, rated 10 days after spraying, was greatest when glufosinate was used with a sodium C₁₂/C₁₄-alcohol-diglycolether sulfate (FAEO-sulfate) and least with polyoxyethylene (POE)(8) tridecyl ether; intermediate effectiveness was obtained with a combination of herbicide and a POE(15) tridecyl ether or POE(15)-tallow amine. The activity of the target enzyme, glutamine synthetase, measured 2 h after spraying, was reduced most when FAEO-sulfate was present and least with POE(8) tridecyl ether. The behaviour of the glufosinate wetting agent solutions on plant foliage was analysed by measurements of spray retention, droplet contact angles and foliar uptake of [¹⁴C]glufosinate. The results led, for both grass species, to the conclusion that differential ability of the wetting agents to enhance the permeation of glufosinate from the leaf surface deposit into the leaf tissue was the main factor responsible for the differences in herbicidal effectiveness of the glufosinate/wetting agent combinations used in this study.     

Spectrophotometric determination of ferric dimethyldithiocarbamate (ferbam) in formulations,grain and apples using 1, 10-phenanthroline

A procedure has been developed for the determination of ferbam (ferric dimethyldithiocarbamate) by converting it into ferbam-phenanthroline complex, which is dissolved in acetone + water (1 + 1 by volume), and the absorbance measured at 490 nm against a reagent blank. Beer's law is obeyed over the concentration range 0–8–20-0 mg litre^?1 in the final solution. The method is sensitive, selective and can be used for the direct determination of ferbam in commercial samples, in mixtures with various other dithiocarbamates (ziram, zineb, maneb, etc.) and from grains (rice and wheat) and apples. The limit of determination from foodstuffs is 0–4 mg kg^?1.     

Some physicochemical factors influencing foliar uptake enhancement of glyphosatemono(isopropylammonium) by polyoxyethylene surfactants

Structure-concentration–foliar uptake enhancement relationships between commercial polyoxyethylene primary aliphatic alcohol (A), nonylphenol (NP), primary aliphatic amine (AM) surfactants and the herbicide glyphosatemono(isopropylammonium) were studied in experiments with wheat (Triticum aestivum L.) and field bean (Vicia faba L.) plants growing under controlled-environment conditions. Candidate surfactants had mean molar ethylene oxide (EO) contents ranging from 5 to 20 and were added at concentrations varying from 0·2 to 10 g litre^?-1 to [¹⁴C]glyphosate formulations in acetone–water. Rates and total amounts of herbicide uptake from c. 0·2–μl droplet applications of formulations to leaves were influenced by surfactant EO content, surfactant hydrophobe composition, surfactant concentration, glyphosate concentration and plant species, in a complex manner. Surfactant effects were most pronounced at 0·5 g acid equivalent (a.e.) glyphosate litre^?-1 where, for both target species, surfactants of high EO content (15–20) were most effective at enhancing herbicide uptake: surfactants of lower EO content (5–10) frequently reduced, or failed to improve, glyphosate absorption. Whereas, at optimal EO content, AM surfactants caused greatest uptake enhancement on wheat, A surfactants gave the best overall performance on field bean; NP surfactants were generally the least efficient class of adjuvants on both species. Threshold concentrations of surfactants needed to increase glyphosate uptake were much higher in field bean than wheat (c. 2 g litre^?-1 and < 1 g litre^?-1, respectively); less herbicide was taken up by both species at high AM surfactant concentrations. At 5 and 10 g a.e. glyphosate litre^?-1, there were substantial increases in herbicide absorption and surfactant addition could cause effects on uptake that were different from those observed at lower herbicide doses. In particular, the influence of EO content on glyphosate uptake was now much less marked in both species, especially with AM surfactants. The fundamental importance of glyphosate concentration for its uptake was further emphasised by experiments using formulations with constant a.i./surfactant weight ratios. Any increased foliar penetration resulting from inclusion of surfactants in 0·5 g litre^?-1 [¹⁴C]glyphosate formulations gave concomitant increases in the amounts of radiolabel that were translocated away from the site of application. At these low herbicide doses, translocation of absorbed [¹⁴C]glyphosate in wheat was c. twice that in field bean; surfactant addition to the formulation did not increase the proportion transported in wheat but substantially enhanced it in field bean.     

A laboratory evaluation of the effectiveness of diflubenzuron against Dermestes maculatus De Geer and other storage insect pests

The chitin synthesis inhibitor diflubenzuron, applied as a wettable powder spray to woven polypropylene at 100–500 mg m^?2, was effective against Dermestes maculatus De Geer for at least 12 weeks. D. maculatus was unable to develop on ox hide dipped in a suspension of diflubenzuron (125 mg litre^?1), or on fishmeal dusted at 1–10 mg of active ingredient kg^?1. Diflubenzuron prevented the development of infestations of Callosobruchus maculatus (L.) on peas and of Acanthoscelides obtectus (Say) on beans dusted at 1–5 mg kg^?1. The compound was also very effective against early instar larvae of Trogoderma granarium Everts on wheat. The persistence and activity of diflubenzuron at low dosage rates against D. maculatus appear to justify larger scale trials.     

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.     

Development of a nephelometric version of the CIPAC method for measuring dilute emulsion stability

The characterisation of emulsions at dilution rates greater than 1:20, currently used in most international specifications for agrochemical emulsifiable concentrate (EC) formulations, is becoming increasingly important. CIPAC MT36.2 is the internationally-accepted test method for determining the bulk stability of emulsions containing 10 ml litre^?1 or less of added EC. A new nephelometric version of this test method has been examined which, although not as accurate as the official method, gives more rapid results. An assessment of the new method against the official method at a working concentration of 5 ml litre^?1 is reported. Agreement is good, despite the semi-empirical nature of the new method, but only if emulsions are re-emulsifiable at the end of the standing period. The scope of the method is discussed and areas of application indicated.