A film technique for the biological evaluation of pyrethrum-in-oil insecticides for use against stored product insects in warehouses

There is need for a technique whereby a given insecticidal preparation can be compared with a standard containing 0.8% (w/v) pyrethrin 1 in a heavy white oil and pronounced biologically equal or inferior to the standard within known and reasonable limits. A film method was investigated, Tribolium castaneum beetles being used as the test insects.
Numerous factors which may influence the kill achieved are discussed. The results of preliminary work, planned to help in the standardization of some of these factors, are summarized.
Several materials were tested to ascertain their suitability for reception of the insecticidal film and, as thin greaseproof paper showed promise, its possibilities were explored. Although 0.3 % pyrethrin I could be distinguished from 0.4%, 0.5% could not be distinguished from 0.8%, and the results throughout were very heterogeneous.
Woven Nylon proved more satisfactory, since the test just failed to establish a significant difference between 0.6 and 0.8% pyrethrin 1. The origin of a pink coloration of the substrate, when T. castaneum beetles were confined on Nylon sprayed with pyrethrum in oil, was investigated.
Whatman filter paper no. 544 proved the best substrate, and a comparative test on it will distinguish 0.65% pyrethrin 1 from the standard 0.8%; the limit could probably be raised to 0.7%.
The influence of several factors on the homogeneity of the results was investigated, and the importance was shown of allowing beetles time to recover from the mechanical shock inherent in the method of counting into batches.
Directions are given for carrying out the film technique for comparing preparations of relatively high pyrethrin content. The method does not measure the direct spray or fumigant action of the insecticide.
The technique described is compared with the Peet-Grady method for evaluating liquid household insecticides of low pyrethrin content. A simplified, but less accurate, design for the test is indicated.     

Response of insecticide-resistant and susceptible houseflies (Musca domestica) to a commercial granular bait formulation containing methomyl

Female houseflies (Musca domestica L.) from a susceptible and a multi-insecticide-resistant strain were used to evaluate the relative toxicity of an insecticide bait formulation of the carbamate insecticide methomyl. Individual flies were allowed to feed on bait granules for an unrestricted period or for 5 s. Resistant flies took longer than susceptible flies to initiate a feeding response. When allowed to feed continuously, those from the resistant strain spent longer feeding than susceptible ones. The time taken to knock-down (KD), including feeding times, was significantly greater for resistant than susceptible flies (P less than 0.001), but once the proboscis was withdrawn from the granule there was no difference in KD times between the strains. All flies from both strains were knocked down, and only a very small number of resistant and susceptible flies recovered. The toxic effects of methomyl on flies which were restricted to a 5 s feed ranged from no observed effect to KD in less than 1 min. After feeding for 5 s, 81% of resistant and 98% of susceptible flies developed signs of methomyl poisoning. More resistant than susceptible flies recovered from KD, giving final mortalities of 46% and 88% respectively. With both feeding regimes, some flies of both strains which had apparently recovered from KD had lost their ability to fly. Observations have also shown that 8% of resistant flies may have been repelled by methomyl granules. The implication of these results on the survival of M. domestica in intensive animal units following exposure to methomyl bait is also discussed.     

The Potassium Iodide Method for Determining Protection Factors in Open-fronted Microbiological Safety Cabinets

A method for determining operator protection factors in Class I and Class II microbiological safety cabinets and for evaluating product protection factors in Class II cabinets, is described. The technique employs an aerosol of potassium iodide droplets produced by a spinning disc generator together with special centripetal air samplers detecting any aerosol escape. The method meets the requirements of British Standard (BS) 5726 and is an alternative to the microbiological technique.
The method has been used to evaluate the performance of a number of safety cabinets in relation to the requirements of BS 5726.
Working procedures and unsuitable environments have been shown to prejudice the containment performance of open-fronted cabinets by several orders of magnitude.
The relationship between inflow air velocity and protection factors in Class I safety cabinets has confirmed the optimum requirements defined in the British Standard.     

The parameters of comparative evaluation of insecticidal activity of preparations in aerosol containers

On the basis of experimental data, the authors present a group of parameters for the purpose of unification of comparative evaluation of the insecticidal effect of preparations in aerosol containers designed for combatting flying and non-flying domestic insects. The advisability of evaluation of the effect of the preparations for combatting flying insects according to the concentration of insecticides ensuring death of flies in the course of 15 min and the corresponding expenditure of the mixture has been substantiated. Preparations designed for combatting non-flying insects should be evaluated according to the coefficients of acute action, ovicidal and residual effects. To facilitate analysis and evaluation of the preparations in aerosol containers, the authors propose their classification according to the parameters of the insecticidal effect. Classification of the preparations under study according to their parameters is presented. It has been demonstrated that compositions containing pyrethroids and their mixtures with DDVP--Neofos, Neofos-2 and Pif-Paf are the most efficient.     

A note on the efficiency of a pyrethrum spray in controlling Ephestia elutella Hb. moths in a granary

A stowage in a London granary containing 500 tons of Manitoba wheat was sprayed with 0.8 % w/v pyrethrins in Shell oil P31, in an attempt to control an Ephestia elutella infestation. The mean deposit on the surface of the wheat was 1-5 mg./sq.cm., of which one-sixth was due to the settling of mist.
All the moths in the stowage at the time of spraying, estimated at 68,900, were killed or fatally affected within 24 hr., and those which emerged later, estimated at 7500, were killed by the insecticidal film.
The spray was not observed to have any marked effect on the size of the migrating larval population.     

Laboratory methods for studying non-preference resistance to cabbage root fly in cruciferous crops

A laboratory method for testing cruciferous plants for their non-preference resistance to cabbage root fly is described. Test plants were fully randomized on a turntable inside a large chamber containing cabbage root flies. The apparatus was housed in a controlled environment room. The root-fly eggs, laid in the sand surrounding test plants, were extracted using a flask flotation method which was quicker and more efficient than the stirring technique which it superseded. Two batches of plants were tested alternately, one being exposed to the flies, while the other was sampled for eggs. Each batch of test plants received three 1-day exposures to egg-laying, their positions within the test chamber being changed for each exposure to ensure complete randomization. This test method gave highly consistent results and indicated that there were differences in the flies' preference both between cultivars of radish and cauliflower and for individual plants within cultivars. Plants representing the extremes of preferences discovered in the two crops were saved for further study. It was not possible to correlate seed weight, time of seedling emergence, foliage surface area, or hypocotyl attitude in relation to soil level, with the egg-laying preference of the cabbage root flies.     

Model-Based Investigations of Different Vector-Related Intervention Strategies to Eliminate Visceral Leishmaniasis on the Indian Subcontinent

The elimination of infectious diseases requires reducing transmission below a certain threshold. The Visceral Leishmaniasis (VL) Elimination Initiative in Southeast Asia aims to reduce the annual VL incidence rate below 1 case per 10,000 inhabitants in endemic areas by 2015 via a combination of case management and vector control. Using a previously developed VL transmission model, we investigated transmission thresholds dependent on measures reducing the sand fly density either by killing sand flies (e.g., indoor residual spraying and long-lasting insecticidal nets) or by destroying breeding sites (e.g., environmental management).Model simulations suggest that elimination of VL is possible if the sand fly density can be reduced by 67% through killing sand flies, or if the number of breeding sites can be reduced by more than 79% through measures of environmental management.These results were compared to data from two recent cluster randomised controlled trials conducted in India, Nepal and Bangladesh showing a 72% reduction in sand fly density after indoor residual spraying, a 44% and 25% reduction through the use of long-lasting insecticidal nets and a 42% reduction after environmental management.Based on model predictions, we identified the parameters within the transmission cycle of VL that predominantly determine the prospects of intervention success. We suggest further research to refine model-based predictions into the elimination of VL.     

Evidence for a juvenile hormone receptor involved in protein synthesis in Drosophila melanogaster

The larval fat body of newly eclosed adults of Drosophila melanogaster was found to contain a single major binding protein specific for juvenile hormone (JH). Binding to this protein was saturable, of high affinity, and specific for JH III. The protein has a subunit molecular weight (Mr) of 85,000, as determined by photoaffinity labeling. The same or similar JH-binding protein was found in larval fat body and cuticle of third instar larvae and in male accessory glands and heads of newly eclosed adults. It was not found in several other tissues in adults. Male accessory gland cytosol from wild-type flies was found to contain a single binder with a dissociation constant (KD) of 6.7 nM for JH III; a binder in similar preparations from the methoprene-tolerant (Met) mutant had a KD value 6-fold higher. JH III stimulated protein synthesis in glands cultured in vitro, but this effect was reduced in Met flies as compared to wild-type flies, establishing a correlation between JH binding and biological activity of the hormone. In addition, glandular protein accumulation during the first 2 days of adult development was less in Met flies than in wild-type flies. These results strongly suggest that the binding protein we have identified mediates this JH effect in male accessory glands and thus is acting as a JH receptor.     

STUDIES ON THE SYNERGISTIC EFFECT OF PIPERONYL BUTOXIDE AND ISOBUTYLUNDECYLENEAMIDE ON PYRETHRINS AND ALLETHRIN

Experiments are described to compare the toxicity of natural pyrethrins and allethrin, the completely synthetic homologue of cinerin I, and to show the effect of the two synergists, piperonyl butoxide and iaobutyl undecyleneamide (IN 930) on both these active ingredients, using a measured-drop technique with Mucca domestiur L. the housefly, and a residual-film technique with Cimex lectularius L. the bed bug. In the conditions of the experiment, pyrethrins were shown to be twice as toxic as allethrin to flies, and 5.5 times as toxic as allethrin to bugs. The two synergists were tested at several ratios to the two insecticides, ranging from 1 : 1 to 20 : 1. The results were plotted as series of log. concentration/probit regression linea. These were parallel for the bug tests; but in the fly tests, the slope of the line increased with a rise in the proportion of Synergist to insecticide. The estimated median lethal concentrations indicated, in all cases, that the toxicity increased with a rise in the ratio of synergist to insecticide, at least up to 20 : 1. However, the enhancement of toxicity was greatest for the smaller ratios and fell off as the ratio increased. Piperonyl butoxide was the more powerful synergist, increasing the potency of pyrethrins 5 times and allethrin 4 times to flies, and pyrethrins twice and allethrin 3 times to bugs, whereas IN 930 did not increase the potency of either ingredient more than twice to either test insect.
The addition of piperonyl butoxide to residual films of pyrethrins greatly prolonged their effectiveness; but an experiment designed to investigate the effect of the synergist on the stability of this insecticide showed that this action, if it exists, must be slight.     

A Comparison of Methods to Measure Operator Protection Factors in Open-fronted Microbiological Safety Cabinets

Comparative tests to measure operator protection factors in microbiological safety cabinets in accordance with British Standard 5726 have demonstrated good agreement in the results obtained by a microbiological method using a Collison nebulizer and the technique producing an aerosol of potassium iodide. Either method is suitable for testing for operator protection factors in Class I and Class II safety cabinets.
The Collison nebulizer should be considered as the standard aerosol generator for the microbiological method; alternative nebulizers meeting the general requirements of BS 5726 should be compared in performance with this nebulizer if they are to be used for containment tests.
Any microbiological safety cabinet specified for a new installation should have been 'type' tested to ensure compliance with BS 5726. However, in order to ensure adequate performance, on-site commissioning tests (and routine maintenance checks thereafter) are necessary to verify that air velocity, filtration and operator protection factor requirements are met.     

Screening method for insecticidal activity using first instars of black blow fly (Diptera: Calliphoridae)

A bioassay method suitable for rapid mass screening of fermentation and synthetic organic compounds for insecticidal activity is described. The test, which uses first instars of susceptible black blow fly, Phormia regina (Meigen), in a bovine serum medium, detects insecticidal activity with reproducible results. It is capable of selecting the most active compound in structure-activity relationships by minimum effective dose concentration studies. The bioassay system is easy to operate and requires only a minute quantity of chemical compound.     

LABORATORY STUDIES ON THE CHEMO-SENSORY REACTIONS OF BLOWFLIES

Attraction of various blowflies to sheep wool has been demonstrated under laboratory conditions using a choice-chamber technique. The attractive factor in wool is intimately associated with the wool fibre for it does not disappear during storage and it is not completely removed by washing.
Only female flies were attracted to wool. The highest degree of attraction was obtained from fertilized females which had daily access to meat. Even in the absence of fertilization and meat, attraction was not completely abolished.
The species and strains tested can be placed in the following order in terms of strength of response to sheep wool: Lucilia sericata (British), L. cuprina (tested on damp floor)>L. sericata (Danish: country)> L. sericata (Danish: city), L. sericata (Australian) > L. illustris, L. caesar. No response was given by Calliphora vomitoria.
The olfactory organs involved in the response to wool are mainly on the antennae but antennaeless L. sericata and L. cuprina with some tarsi removed were still able to show some response to wool provided that they were tested on a damp floor. In the course of testing the olfactory responses it was also shown that the main humidity receptors are present on the antennae.
The existence of a 'wool-factor' to which only certain strains of L. sericata and L. cuprina are specially sensitive offers a possible explanation for the greater efficiency of these species as myiasis-producing forms.     

Dieldrin-resistant cabbage root fly in England

The existence of dieldrin resistance in Erioischia brassicae has been investigated in the main areas in England and Wales where brassicas are grown for human consumption. Dieldrin-susceptible and dieldrin-resistant flies were collected and bred as separate strains in the laboratory. In toxicity tests adult flies were treated with topically applied doses of insecticide in microdrops of cellosolve, and larvae were dipped in solutions of insecticide in 70% acetone and 30% water. Adults of the laboratory resistant strain showed a high level of resistance to dieldrin and aldrin and a lower level of resistance to γ-BHC. There was no cross-resistance with chlorfenvinphos or diazinon. Larvae of the resistant strain were shown to be resistant to dieldrin. Dieldrin resistance has been found in four areas in southern England, but not in a fifth major area, and resistant flies did not increase as rapidly in some areas as others. Sufficient migration of flies appeared to take place to produce similar percentages of resistant flies over areas of several square miles, but considerable differences were found in fly populations about 10 miles apart. It is suggested that the speed of development of insecticide resistance is affected by the proportion of brassica crops which are treated in an area, the amounts of insecticide applied to individual crops, and hence the insecticidal pressure applied to the E. brassicae population.     

Postharvest treatments against Western Flower Thrips [Frankliniella occidentalis (Pergande)] and Melon Thrips (Thrips palmi Karny) on orchids

Postharvest treatments, including insecticidal dips, isopropyl alcohol dips, insecticidal fogs and hot-water immersion, were evaluated to control mixed infestations of Western Flower Thrips (Frankliniella occidentalis) and Melon Thrips (Thrips palmi) on dendrobium orchid blossoms. The limiting factor for all postharvest treatments was phytotoxicity, characterised by a loss of vase life that differed among cultivars. Insecticidal dips and insecticidal fogs were less phytotoxic than hot-water immersion and isopropyl alcohol dips. Insecticidal fogs consisting of abamectin 2.0% e.c. and abamectin tank-mixed with Pyrenone e.c. (6% pyrethrins, 60% piperonyl butoxide) reduced the mean number of thrips per blossom by 93.8% and 92.3%, respectively and were nonphytotoxic. An insecticidal aerosol, Floragas (2% permethrin and 0.1% pyrethrum dissolved in high pressure liquified CO₂) reduced thrips by 33% to 54% with no phytotoxicity. Insecticidal dips for 3 min with agitation reduced the mean number of thrips per blossom by 43.7% to 99.1%. Of the 12 insecticides and one surfactant tested, only chlorpyrifos 44.4% e.c., fluvalinate 22.3% f., and chlorpyrifos 50% d.f. were both effective and nonphytotoxic. Immersion in water at 49.5°C for 15 and 20 s reduced the mean number of thrips per blossom by 88.1% and 95.3%, respectively. A 70% solution of isopropyl alcohol applied as a postharvest dip did not kill all thrips and was extremely phytotoxic to blossoms.     

Effect of the life-span of female Glossina palpalis gambiensis on the weight and size of its progeny

Abstract. Pupae and teneral flies of Glossina palpalis gambiensis originating from three successive reproductive cycles were compared for their size and weight. In general, pupal weight and fly weight increased, whereas fly size, measured as wing vein length, decreased with the number of reproductive cycles. The linear regression observed between weight and wing vein length of the fly demonstrated that, particularly for flies originating from the first and second larvipositions, small changes in wing vein length reflected substantial differences in weight.
The results of these laboratory experiments were compared with some field data on Glossina morsitans from Zambia and related literature. The life span of the female tsetse, affecting the size of her progeny, could clarify partially some of the field observed seasonal changes in size, whereas the correlation between fly size and weight could eventually explain the differential mortality of some size classes of tsetse flies. However, whether these laboratory observations can be extrapolated to the field has still to be confirmed.     

EXPERIMENTS ON SPRAYING WITH DDT TO PREVENT THE FEEDING OF SCOLYTUS BEETLES ON ELM AND CONSEQUENT INFECTION WITH CERATOSTOMELLA ULMI

Experiments were done for three years on street elms at Folkestone and Aldenham to repeat American work on the use of insecticidal sprays to prevent feeding by Scolytus beetles, which carry Ceratostomella ulmi , the cause of elm disease. Although the fungus can remain alive in the older annual rings of an infected tree, active disease usually results from fungus freshly introduced by Scolytus. Thus spraying is of value on infected, as well as uninfected elms.
The results of the experiments supported American conclusions that DDT was superior to benzene hexachloride. A 1.5% solution of DDT in miscible oil gave reasonably good, but not perfect, control, and was much superior to solutions made from DDT in the form of a dispersible powder.
Spraying of trees 20–30 ft. high cost over £1 per tree per year, which is considered prohibitive, except for small trees of special amenity or sentimental value.     

A laboratory method for studying the biology and control of pests in mushroom compost

A Petri dish technique, devised by Eger (1960, 1962) for studying mycelial growth through mushroom compost and casing material, has been modified for pest investigations. The method provides a sensitive test for phytotoxic and insecticidal action of applied chemicals, and experiments are described which indicate that thionazin is a suitable insecticide for use against Heteropeza pygmaea Winnertz (Dipt.: Cecidomyiidae). Examples are also given of the use of this method in the study of the biology and population dynamics of paedogenetic Cecidomyiidae.     

Effect of tin and lead chlorotriphenyl analogues on fruit fly Drosophila hydei and liposomes membrane

This article presents the results of a study investigating the biological activity of triphenyltin chloride (TPhT) and two metalloorganic compounds, triphenyllead chloride (TPhL) and triphenylmethane chloride (TPhC), in their interaction with model membranes and the living organisms of fruit flies Drosophila hydei. The study of model membranes (sonicated liposomes) was conducted using the electron spin resonance (ESR) spin probe technique, whereas the experiment on fruit flies involved investigating their viability on media containing the studied compounds. The test results clearly demonstrate that TPhT affects fruit flies more actively than TPhL (complete lethality after 7 days of culture with a TPhT-containing medium). No toxic effect of TPhC on fruit flies was shown. The results of the biological experiment were reflected in the physical experiment involving an ESR study of liposomes: TPhT activity manifested itself as a considerable increase in fluidity of the central region of the liposome lipid bilayer.     

Arabian sandflies (Diptera: Psychodidae) prefer the hottest nights?

Abstract. A vehicle-mounted net was used to collect hourly samples of sandflies on 15 nights during June in northern Oman. Every half hour, the temperature, relative humidity, wind velocity and light intensity were measured (there was no cloud or rainfall during this period).
The sandflies caught were mainly Phlebotomus alexandri and Sergentomyia clydei. Their circadian activity increased rapidly after sunset (18.50 hours). The high level of activity was fairly constant during 9 h of darkness until dawn, when it decreased rapidly. A few flies were still active at 07.00 hours, 1.5 h after sunrise.
A multiple regression showed that the main factor affecting sandfly activity was light intensity. When this factor was removed, by considering only the 135 catches collected during the 9 h of darkness, the second most important factor was low relative humidity, followed by low wind velocity. Temperature was not a significant factor in the analysis, because of its strong negative correlation with humidity. However, when the effect of humidity was removed from the regression, high temperature became significant, but less important than wind.
The regressions showed that, for flight activity, the optimum humidity was around 10%; the probable maximum wind velocity was 3.5 ms^-1 and 11^oC was the probable minimum temperature. Thus, when the 4 nights with highest catches (200–260 flies/night) were compared with the 4 nights with lowest catches (50–120 flies/night), the best nights had a low humidity (10–25%) and low wind speed (<0.3ms-¹) in combination with highest temperatures (31–43^oC).