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The fate of [14C]-dimethoate and [14C]-parathion after topical application to strains of Myzus persicae resistant and susceptible to organophosphorus compounds was investigated. In 4 h approximately 65% of the dimethoate or para-thion applied was lost from the aphids by evaporation, and this limited the amount available for penetration into the insect. Only approximately 25% of the dose applied penetrated, of which a very small proportion was excreted as metabolites. There was no difference in the amounts penetrating into the resistant and susceptible strains, indicating that penetration was not a factor contributing to the observed resistance. These findings emphasise that evaporation from the cuticle can greatly influence results when insecticides are applied topically.

The insecticidal activities against houseflies (Musca domestica L.) and mustard beetles (Phaedon cochleariae Fab.) of 29 new 5-benzyl-3-furylmethyl 2,2-dimethyl-cyclopropane-carboxylates are compared with those of the corresponding chrysanthe-mate (bioresmethrin) to assess the influence of non-ethylenic and isobutenyl substituents at position 3 of the cyclopropane ring. Of the new groups investigated, only 3-methoxyiminomethyl gives equal or enhanced activity; 3-(2-furyl) esters are moderately effective, but 3-phenyl and 3-alkoxycarbonyl compounds show weak activity. A 3-(2,2,2-trihaloethyl) compound was more active than compounds with other saturated groups, such as isobutyl.

Esters of 2,2-dimethyl-3-(2,2-dichlorovinyl)-cyclopropanecarboxylic acid with appropriate alcohols are more active insecticides than the corresponding 3-isobutenyl compounds (chrysanthemates). (±)-Cis and (±)-trans forms of the dichloro acid are obtained by fractional crystallisation of the mixed acids or by hydrolysis of the ethyl esters separated by fractional distillation. The (±)-cis and (±)-trans acids are resolved into their (+)- and (-)-forms with α-methyl-benzylamine and threo-l-p-nitrophenyl-2-N,N-dimethyiamino-propane-1,3-diol respectively. As for the corresponding chrysanthemates, the (+)-cis and (+)-trans acids give esters more active as insecticides than their enantiomers.

The influence of the nature, number and relative dispositions of substituents on the furan ring of furfuryl and 3-furylmethy chrysanthemates on insecticidal activity to two insect species is described. 5-Benzyl-3-furylmethyl chrysanthemate was the most active compound developed in the investigation.

Eighteen esters of resolved cis- and trans-3-(2,2-difluoro, -dichloro or -dibromovinyl)-2,2-dimethylcyclopropanecarboxylic acids with 5-benzyl-3-furylmethyl, 3-phenoxybenzyl and α-cyano-3-phenoxybenzyl alcohols were prepared and evaluated for insecticidal activity against Musca domestica L. and Phaedon cochleariae Fab. Chlorine and bromine substituted esters are more active, in general, than those with fluorine, and in the most active esters, the cis isomer is more effective than the trans.

Following the failure of insecticides to control Myzus persicae on sugar beet, populations from the field were examined for susceptibility to dimethoate. Topical application of discriminating doses of dimethoate showed a 30-fold variation in susceptibility between different populations. After this preliminary screening, clones were established from some populations and their resistance determined by both topical application and a systemic bioassay. This confirmed resistance to dimethoate and demonstrated resistance to demeton-S-methyl. There was no resistance to some other compounds tested. In all populations tested, resistance was associated with increased carboxylesterase activity.

A technique is described for applying insecticide solutions accurately and rapidly to aphids. Radiochemical measurements showed that volume of 0.02 to 0.2 μl could be applied accurately and that more than 90% of the dose remained on the aphids when 0.08 μl or less was applied. There was good agreement between the radiochemical calibration land the toxicological results.

The toxicity as contact insecticides of the esters of (±)-3-methyl-2-allyl-cycfopent-3-en-4-ol-i-one with the natural (+)-trans and with synthetic (±)-cis-trans-chrysaii-themum monocarboxylic acids has been compared with that of the natural pyrethrins. The comparison was carried out on five species of test-insects. It was found that the figure for both the absolute and the relative toxicities of these compounds varied with the species used as test-subject. The factors involved in this variation are discussed. The extremes of variation of relative toxicity for the compounds with the natural acid were from about one-eighth as toxic as the pyrethrum standard when the aphid Macrosiphum solanifolii was used as test subject to nearly four times as toxic as the standard with the larvae of the moth Plutella maculipennis. The fully synthetic material varied from about one-sixteenth as toxic as the standard to Macrosiphum solanifolii to nearly twice as toxic to the larvae of Plutella maculipennis. The compound with the natural acid was approximately twice as toxic as the fully synthetic material to three of the insect species, but the fully synthetic material was considerably more than half as toxic as the partially synthetic to the fourth test-species. It is pointed out that while it is widely recognized that large differences in relative toxicity may occur when the effect of chemicals of widely different structure and mechanism of action are compared on a number of different test-species, the fact that these differences may also occur with related chemicals with, presumably, a similar mechanism of action, has not been clearly stated. Even when the differences in relative toxicity are taken into account, the two synthetic pyrethrin-like esters still show high insecticidal activity. It seems reasonable to suppose from the results that economic commercial synthesis of pyrethrin-like insecticides is not impossible.

The insecticidal activities to houseflies and to mustard beetles of the 19 methylbenzyl (±)‐cis‐trans‐chrysanthemates were measured to establish the patterns of substitution that produce the greatest toxicities to these insects. The two species of insect differ in their responses to the various compounds in the series. The most active compounds to houseflies and mustard beetles are, respectively, 2,4,6‐and 2,3,6‐trimethylbenzyl (±)‐cis‐trans‐chrysanthemates.

Department of Insecticides and Fungicides, Rothamsted Experimental Station, Harpenden, Herts. The relative toxicities of esters related to the natural pyrethrins and to allethrin were evaluated against Phaedon cochleariae (mustard beetle), Tenebrio molitor (yellow mealworm beetle), Dysdercus fasciatus (cotton stainer) and Plutella maculipennis (diamond-back moth) and the results were compared with those of workers who used Musca domestica (housefly). With the insect species used here there were no outstanding reversals of the toxicity ratings established in the studies with M. domestica. However, the toxicities of the esters depended more on the nature of the alcohol when two acids were compared and on the acid component with different alcohols. (+)-Allethrolone and (+)-cinerolone gave more toxic esters than their optical isomers but there was less difference than had been found with other insect species between esters from trans-and cis-chrysanthemic acids.

A range of 5‐benzyl‐3‐furylmethyl cyclopropane carboxylates and other esters are evaluated against house‐flies, mustard beetles and two mosquito species. The results show the importance for activity of a gem‐dimethyl group on the cyclopropane ring and that substitutions at C3 give wide variations in insecticidal activity and marked species specificity. Some of the compounds had considerable knockdown activity against houseflies, but the structural requirements for this type of action differ markedly from those for kill. RESP-6378

RESP-4434

SUMMARY A new portable insect suction sampler, powered by a small petrol engine, is described. It has been in use for three seasons, and examples given of samples taken from oil-seed rape demonstrate that the suction method is more informative than visual counts or sweep-net sampling for assessing blossom beetle populations. RESP-9012

SUMMARY Wettable powder and emulsifiable concentrate formulations of endosulfan and azinphos-methyl and an emulsifiable concentrate of malathion were sprayed on oil seed rape in full flower to assess their relative toxicities to foraging honeybees. Endosulfan was very much safer to honeybees than the two organophosphate insecticides, but there was little difference between the two types of formulation.

(1966). Insecticides and Beekeeping in England and Wales. Bee World: Vol. 47, No. 2, pp. 65-70.

THE natural pyrethrins (see refs 1 and 2 for references) (for example, pyrethrin I (1)) and related synthetic insecticides3 (allethrin (2), bioallethrin (3), resmethrin (4), bioresmethrin (5), Cismethrin (6) and the ethanochrysanthemate (7)) are unstable in air and light (see refs 1 and 2 for references, and ref. 4). This property restricts their use, particularly against pests of agricultural crops, in spite of other favourable characteristics (see refs 1–3 for references) (outstanding potency against many insect species, rapid action, and low mammalian toxicity5). We describe here new synthetic esters, ten to one hundred times more stable in light than previous pyrethroids, yet as active against insects as bioresmethrin (5) and with low mammalian toxicity.

SummarySeventeen experiments with spring barley testing seven amounts of nitrogen were made on commercial farms in Somerset, Devon and Cornwall between 1965 and 1968. Crop measurements and determinable site factors were only partially successful in accounting for differences between sites and between years in optimal N and efficiency of N use below optimum.The actual optima were found to differ considerably from predicted N requirements based on past cropping and summer rainfall.

SummaryExamples of response surfaces for pairs of nutrients and results of 41 multi-level experiments with N only were used to compare the goodness-of-fit of polynomial, inverse polynomial, exponential and intersecting-straight-lines models.Whereas no one model fitted best at every site, many results were well represented by two intersecting straight lines and on average, this model had the least residual mean square. Of 17 experiments with spring barley in south western England the few results best represented by smooth curves were from crops much affected by leaf diseases.Fertilizer response was poorly represented by models without a falling asymptote, like the simple exponential and inverse linear. Study of residuals after fitting the quadratic showed that this widely used model consistently over-estimated both the amount of fertilizer needed for maximum yield and the yield loss when too much fertilizer was given.When fitted to the mean yields of each nitrogen treatment, most models had residual mean squares equal to or less than the error mean square, repeating a result obtained at Rothamsted as early as 1927. We question the validity of some well-known evidence for block and treatment additivity.For 12 experiments in 1970, between-site differences in the parameter values of the two straight lines representing grain yield were related to leaf area at ear emergence.

Scanned PDF of POISONING OF HONEYBEES BY PESTICIDES: INVESTIGATIONS OF THE CHANGING PATTERN IN BRITAIN OVER 20 YEARS, part of Rothamsted Experimental Station Report for 1977 Part 2

WE describe a new insecticide, related to the pyrethrins, and considerably more active than any other available compound, of whatever class (LD50 about 0.0003 µg per insect, equivalent to about 0.03 mg kg−1).

THE natural pyrethrins (see refs 1 and 2 for references) (for example, pyrethrin I (1)) and related synthetic insecticides3 (allethrin (2), bioallethrin (3), resmethrin (4), bioresmethrin (5), Cismethrin (6) and the ethanochrysanthemate (7)) are unstable in air and light (see refs 1 and 2 for references, and ref. 4). This property restricts their use, particularly against pests of agricultural crops, in spite of other favourable characteristics (see refs 1–3 for references) (outstanding potency against many insect species, rapid action, and low mammalian toxicity5). We describe here new synthetic esters, ten to one hundred times more stable in light than previous pyrethroids, yet as active against insects as bioresmethrin (5) and with low mammalian toxicity.&nbsp

The effects on foraging bees of spray formulations of demeton-methyl and granular formulations of disulfoton and phorate applied to field beans in flower, were compared. Sprays killed honeybees foraging on the beans, whereas granules did not, either immediately after application or later. After becoming systemic in plants, the insecticides seemed harmless to bees.

RESP-3858

Methods are described for detecting insecticides in dead bees. Bees received by the Chief Bee Advisory Officer of the Ministry of Agriculture, Fisheries & Food have been analysed by these methods and it is evident that each year some are killed by insecticides. Most such happenings are in Eastern England and are caused by spraying, especially from the air, with organo-phosphates to control aphids on pea and bean crops. The use of poison baits to kill wasps is another cause. Such happenings could mostly be prevented by taking a few elementary precautions.

THE chemical control of the green peach aphid Myzus persicae (Sulz.), which damages many crops both directly and by transmitting numerous virus diseases, is seriously jeopardized by the world wide occurrence of resistance to organophosphorus insecticides. In the United Kingdom resistance previously confined to glasshouse crops now occurs in the field. Nothing is known about the nature of the resistance mechanism(s) in these insects and little about the patterns of resistance. We wish to report (1) large differences in the activity of ali-esterases of susceptible and resistant aphids which can be used to determine resistance even in single aphids, (2) large differences in some properties of these enzymes between susceptible and resistant aphids and house flies, and (3) a marked decrease or increase in resistance when the aphids are treated with insecticides in the presence of ‘Sesamex’ (2-(3,4-methylene-dioxyphenyl)3,6,9-trioxaundecane). This is evidence that multi-function oxidases are involved in resistance to organophosphorus insecticides in aphids.

SummaryHoneybees foraging on plants sprayed with “Dieldrex 15” containing Saturn Yellow, a fluorescent pigment, were collected in front of, or within, the hive at intervals after spraying, and grou...

SUMMARY Apterous Myzus persicae resistant to dimethoate reproduce for the same length of time as susceptible aphids, but the resistant ones reproduce significantly faster during the first 10 days of adult life (especially during the first 5 days). Thereafter, they reproduce more slowly, and eventually the susceptible aphids produce approximately the same number of larvae. Resistant aphids die significantly younger. Resistant aphids as larvae develop faster than susceptible ones and are significantly heavier when they first become adult. The resistant aphids do not excrete faster during the first few days but, as they produce more larvae during the first 10 days of adult life and have developed faster, they probably feed faster during development and early adult life or obtain more nutritious food. Resistant aphids were at least as effective as susceptible ones in transmitting sugar-beet mosaic and pea mosaic viruses, and plants showed symptoms sooner when resistant aphids were the vectors.

WE describe a new insecticide, related to the pyrethrins, and considerably more active than any other available compound, of whatever class (LD50 about 0.0003 µg per insect, equivalent to about 0.03 mg kg−1).

FOLLOWING earlier work1, we have synthesized more non-ketonic esters of chrysanthemic acid. One new compound, 5-benzyl-3-furylmethyl (+)-trans-chrysanthemate (I), is fifty-five times as toxic to adult female Musca domestica L. (house-flies) as the mixed esters of the natural pyrethrins, nearly three times as toxic as parathion and more than five times as toxic as diazinon. The same ester is ten times as toxic to adult Phaedon cochleariae Fab. (mustard beetles) as the natural pyrethrins and thirteen times as toxic as parathion. The (±)-cis-trans-clarysanthemate (m.p. 43–48°) is the most toxic compound tested so far, of any class of insecticide, to 1–2 day old unfed females of Anopheles stephensi and Aedes aegypti (results provided by Dr. A. B. Hadaway). This insecticidal activity is greater than has been found before in a compound containing only carbon, hydrogen and oxygen. By contrast, its acute toxicity to mammals seems to be small; for example, the median lethal dose to female rats for the (±)-cis-trans-chrysanthemate administered orally is between 600 and 800 mg/kg (personal communication from Dr. J. M. Barnes).

THE natural pyrethrins1–3, of which the most important constituent is pyrethrin I (1), are very active against a wide range of insect species, do not leave persistent residues, and have a long record of safe use; despite surprisingly high intravenous toxicity, they have low oral toxicity to mammals4. The related synthetic compound, bioresmethrin (2)5,6, has greater insecticidal activity (for example, about fifty times that of pyrethrin I, by topical application5, to a normal strain of houseflies), yet is even less toxic to mammals, both orally and intravenously4,7. Pyrethrin I and bioresmethrin are esters of (+)-trans [1R,3R]-chrysan-themic acid. We have now found that a simple modification of the acid side chain in bioresmethrin by which the four carbon atoms in the isobutenyl group are redisposed to a but-1-enyl substituent (as in 7) produces still greater insecticidal activity (about 100 times that of pyrethrin I to houseflies) whilst retaining low mammalian toxicity. Other changes of the acid side chain in bioresmethrin increase insecticidal activity further; for example the compound (10) with a cis-(Z)-butadienyl group and the dichlorovinyl compound (12) are both 2–3 times as potent as bioresmethrin.

RESP-6190