THE SYSTEMIC INSECTICIDAL ACTION OF SODIUM FLUOROACETATE AND OF THREE PHOSPHORUS COMPOUNDS ON THE EGGS AND LARVAE OF PIERIS BRASSICAE L.

Four compounds, bis dimethylaminophosphonous anhydride ( anhydride ), bis (dimethylamino)fluorophosphine oxide ( oxide ), diethyl paranitrophenyl phosphate ( E 600) and sodium fluoroacetate ( acetate ), previously shown to have systemic insecticidal activity against aphids, have now been tested against the eggs and larvae of Pieris brassicae L.
The anhydride proved to have very little toxic action on Pieris , but the other three compounds showed both contact toxicity and systemic insecticidal action when taken up by the roots of cabbage plants from solution and from soil. The acetate, but more especially the E600, also showed systemic action following application to the leaves.
In all cases the order of decreasing toxicity was E600 > acetate > oxide > anhydride. E600 is the only compound which is outstandingly toxic to Pieris eggs and larvae. It has the added interest that when watered on to the roots of cabbage plants it kills larvae in egg batches on the leaves. Death takes place at the stage when the larvae are biting through the shells. The oxide and acetate proved to be surprisingly innocuous.
Unless it is felt to be too poisonous E600 is worthy of consideration as an insecticide against Pieris eggs and larvae, since it is highly effective as a contact insecticide and also has some systemic action.     

THE SYSTEMIC INSECTICIDAL ACTION OF CERTAIN COMPOUNDS OF FLUORINE AND OF PHOSPHORUS ON PHAEDON COCHLEARIAE FAB.

Four compounds— bis dimethylaminophosphonous anhydride (schradan), bis (dimethylamino)fluorophosphine oxide ( dimefox ), diethyl paranitrophenyl phosphate ( paraoxon ) and sodium fluoroacetate ( acetate )—have been tested against the mustard beetle, Phaedon cochleariae Fab. When the four compounds are compared by a direct contact technique in which insects can also imbibe some of the test solutions, or the insects are caged with foliage which has been dipped and then dried, the order of toxicity to adults and larvae was found to be Paraoxon > acetate ≏ dimefox > schradan.
The paraoxon is very much more toxic than the other compounds. In all cases the adults are more resistant than the larvae.
When the insecticides are applied systemically the order of toxicity changes to Paraoxon > dimefox > acetate ≏ schradan because the acetate causes the plants to wilt and less of it is absorbed. Both paraoxon and dimefox give complete kills of adult Phaedon which is the most resistant stage, at practical concentrations.
When the insecticides were applied to the outer leaves and translocated to the inner untreated leaves an effect was observed with the dimefox and paraoxon after numerous application, but with a single application very inconsistent results were obtained.
It is concluded that schradan and the acetate are ineffective systemically against Phaedon. The dimefox and paraoxon are very effective, but because of their high mammalian toxicity they would require very careful handling in practice.     

THE INSECTICIDAL ACTIVITY OF SUBSTANCES RELATED TO THE PYRETHRINS

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.     

STUDIES ON THE MECHANISM OF INSECTICIDAL ACTION OF ORGANO-PHOSPHORUS COMPOUNDS WITH PARTICULAR REFERENCE TO THEIR ANTIESTERASE ACTIVITY

The preparation of an extract of the mealworm larvae, Tenebrio molitor L. which hydrolyses ethyl butyrate and o -nitrophenyl acetate, but not acetylcholine, is described. The inhibition of this esterase by TEPP-containing materials and parathion was determined.
An enzyme that hydrolysed o -nitrophenyl acetate and was inhibited by a TEPP-containing material was demonstrated in the five other insect species used.
The relative toxicities as contact insecticides to adult Tribolium castaneum Hbst. of ten samples of TEPP-containing materials were compared with their relative activities as esterase inhibitors. There was not an exact quantitative correlation between TEPP content estimated chemically, insecticidal activity and anti-esterase activity; but the correlation was sufficient to suggest interdependence of these factors.
Eggs of Diataraxia oleracea L. and Ephestia kühniella Zell, were shown to contain an enzyme that hydrolysed o -nitrophenyl acetate and was inhibited by the TEPP-containing materials. This enzyme was present in eggs less than 24 hr. old, i.e. before there was any visible signs of development. The TEPP was shown to be toxic to these eggs and in high concentrations kills at an early stage of development before differentiation of the nervous system. This, in conjunction with the other evidence, suggests that esterases other than the choline-esterase of the nervous system are important when considering the toxic action of these compounds.
Comparison of the anti-esterase activity and toxicity of parathion and TEPP-containing materials as insecticides showed that although the TEPP materials were the more potent enzyme inhibitors, parathion was the more potent contact insecticide to five species of insects. This appears to be due to the relative instability of TEPP. The study of the rates of action of the two poisons applied at different concentrations supports this view.     

THE INSECTICIDAL ACTIVITY OF PARATHION, ITS ISOMERS AND SOME RELATED COMPOUNDS

Heat treatment of parathion at 140° C. and above resulted in isomerization and then thermal decomposition; the loss of toxicity to Calandra granaria being correlated with a reduction of the thiono-sulphur content. Similar results were obtained with O:O-dimethyl-(4-nitrophenyl)-thiophosphate. Paraoxon, O:S-diethyl-(4-nitrophenyl)-thiophosphate, and O:O-diethyl-S-(4-nitrophenyl)-thiophosphate, although all possessing considerable contact activity, were less insecticidal than parathion; O:O-dimethyl-(4-nitrophenyl)-thiophosphate, on the other hand, was considerably more effective than parathion. O:O- bis (2-chloroethyl)-O-(4-nitrophenyl)-thiophosphate was considerably less toxic than parathion and appeared to have a different mode of action. Compounds, S-ethyl- bis -(4-nitrophenyl)-thiophosphate, O-ethyl- bis -(4-nitrophenyl)-thiophosphate, and triethyl thiophosphate were ineffective as contact insecticides.
In the series of compounds examined, replacement of the group P = S by P = O or alteration in size of the groups attached to the central phosphorus atom caused a reduction of insecticidal activity.     

INSECTICIDAL ACTIVITY AND CHEMICAL CONSTITUTION: ANALOGUES AND ISOSTERES OF DDT

A number of isosteres of DDT and related compounds have been synthesized and examined for insecticidal activity using the grain-weevil, locust and cotton stainer. A marked loss of activity follows replacement of the chlorine atoms of DDT by methyl and hydroxyl groups. In the nitroalkane series, the optimum structure for maximum toxicity was present in i:i-di-/>-chlorophenyl-2-nitropropane. The significance of these results has been reviewed in the light of current theories of DDT structure and activity. Many of the compounds expected to be toxic were found not to be so, and this inactivity can be attributed either to the initial hypotheses being invalid or to the operation of biological factors preventing concentration of the compound at the site of action.     

三氯杀虫酯类似物的化学结构与生物活性的关系

以合成的系列三氯杀虫酯类似物,对家蝇和棉蚜进行药效测定。结果表明:羧酸烷基为甲基,苯环上的取代基为Br或F时,对家蝇无效。在苯环的邻位上有-OCH₃取代时也无效,如在间位上有-OCH₃取代的化合物,则有一定的杀虫效果,但不如在邻位和对位上都有-OCH₃取代的化合物的药效高。当α-碳上苯环的取代基为3,4-次甲二氧基,而只变换羧酸酯上的烷基(R)时,对家蝇的杀虫效果,趋向于随着α-碳原子与羧酸酯基的R碳链增长而递减。但R为苯基时,则效果不明显。同时从结果中也可以看出所测化合物,可能由于对家蝇和棉蚜的作用机理不同,因而其杀虫效果不成平行关系。     

Insecticidal activity of five Chinese medicinal plants against Plutella xylostella L. larvae

Twenty-five extracts of five Chinese medicinal plant species were screened for insecticidal activity against the diamondback moth, Plutella xylostella L., larvae by a leaf dipping bioassay method. The ethyl acetate, ethanol, and acetone extracts of Veratrum nigrum L. root and rhizome, the ethyl acetate extract of Phytolacca americana L. root, and the petroleum ether extract of Pseudolarix kaempferi Gord. root bark were effective against P. xylostella. Among them, the ethyl acetate extract of V. nigrum showed the strongest insecticidal activity against the second and third instar larvae of P. xylostella, with LC₅₀ values of 225 and 335 ppm, respectively. The other extracts gave little or no insecticidal activity against P. xylostella. These results indicated that V. nigrum may be a promising naturally occurring agent for P. xylostella larval control, and that the organic solvent used for plant extraction can affect its insecticidal activity.     

Comparative insecticidal acitvity of sumithrin and neopinamine

The examination of insecticidal properties of the new pyrethroid--sumithrin--showed this compound in contact action to be a highly effective insecticide, superior in activity to neopinamine. The intestinal action of sumithrin is less pronounced in comparison with neopinamine. Sumithrin is more selective in its effect on insects as compared with neopinamine. In the form of earosols, sumithrin and its mixtures with DDVP are less active than compositions based on neopinamine.     

灰毛豆树皮中的杀虫成分及其杀虫活性

为确定灰毛豆Tephrosia purpurea树皮甲醇提取物中的杀虫成分,以白纹伊蚊Aedes albopictus4龄幼虫为靶标昆虫,在活性跟踪的基础上利用色谱技术分离其活性成分,然后根据各化合物的核磁共振网谱和质谱数据确定化合物的结构,并利用玻片载蚜法和点滴法测定了各化合物对桃蚜Myzus persicae无翅蚜...     

小桐子果壳提取物杀虫活性的生物测定

以水、乙醇、正丁醇、乙酸乙酯、氯仿和石油醚为溶剂,采用冷浸法对小桐子果壳进行粗提,并分别测定各粗提物对豌豆长管蚜和菜青虫的毒力,从中筛选出毒力最强的粗提物进一步对菜青虫进行作用方式的测定.6种溶剂粗提物对豌豆长管蚜和菜青虫的毒力测试结果表明:三氯甲烷提取物和乙醇提取物的活性显著高于其它溶剂提取物,且两种提取物对豌豆长管...     

trans-2,5-Hexadien-l-yl Chrysanthemates and Related Esters

As a simplified model of natural pyrethrins, trans-2,5-hexadien-l-yl chrysanthemate (V), and its 2- or 3-methyl substituted homologues (III and IV), were prepared and tested for insecticidal activities against houseflies. All these compounds retained sufficient insect toxicity to illustrate an interesting relationships between chemical structure and insecticidal activity.

The cis isomer (XII) of compound V and two positional isomers, 2-methylene-4-penten-l-yl and 1,5-hexadien-3-yl chrysanthemates (XIII and XIV), were also synthesized. Of these isomers, XIII was very slightly active, but the other isomers (XII and XIV) were completely ineffective.

On the other hand, the insecticidal activity of 5-hexen-2-yn-l-yl ester (XV), en-yne analogue of V, was almost the same as that of V.     

ANNONA SPECIES AS INSECTICIDES

By extraction and precipitation from several solvents the toxic principle present in Annona reticulata and A. squamosa seeds and roots has been concentrated up to one hundred-fold. A preliminary chemical examination of this concentrate is described, leading to the conclusion that the toxicity is due to a glyceride or glycerides of a hydroxylated unsaturated acid or acids of high molecular weight.
These extracts have been examined for contact and stomach poison and ovicidal properties in a variety of media. When used as a contact insecticide against Aphis fabae, Macrosiphoniella sanborni and Macronphum solanifolii , the concentrate exhibited a toxicity of the same order as that of rotenone, but against Oryzaephilus surinamensis the toxicity was considerably less. As a stomach poison the ether extract was both toxic and repellent to Plutella maculipennis larvae, but was neither toxic nor repellent to Diataraxia oleracea larvae. Ovicidal tests against the eggs of Plutella maculipennis and of Ephestia kühniella were inconclusive. The potency of this concentrate is therefore of a limited nature and although of roughly the same order as that of rotenone to certain aphides, it has neither the intensity of effect nor the range of insecticidal action of that compound.     

Progesterone potentiating effect of Dipsacus mitis D. Don for its contraceptive action in hamster

A pure compound, isolated from ethyl acetate extract (root) of D. mitis D. Don, prevented pregnancy by 100% in adult female hamster but partially in rat when administered orally on Days 1-7 and 1-10 post-coitum respectively. The effective dose in both species was 150 mg/kg. Using uterine wet weight in ovariectomized immature rat as bioassay method, the compound was found to be devoid of estrogenic and antiestrogenic property. On examination for progestational and antiprogestational activity, using trauma-induced deciduoma formation in immature rat uterus as end points, the compound (per se) did not show the former activity but in a conjoint treatment with progesterone it augmented the action of latter. The compound was assumed to act by potentiating progesterone biosynthesis, the excess of which might be the cause for interruption of pregnancy in hamster. This is the first study to report contraceptive efficacy and mode of its action at the uterine level.     

Pyridalyl, a novel insecticide: potency and insecticidal selectivity

Pyridalyl is an insecticide of a novel chemical class (unclassified insecticides). Toxicity of pyridalyl to two insect pest species, Spodoptera litura and Frankliniella occidentalis, an insect predator, Orius stringicollis, and a pollinator, Bombus terrestris, was evaluated in the laboratory. The insecticidal activity of pyridalyl against S. litura was evaluated using the leaf-dipping method. The potency of pyridalyl was highly effective against all development stages (2nd to 6th instar larvae) of S. litura. This compound was also evaluated against F. occidentalis using the direct spray method. For F. occidentalis, toxicity of pyridalyl was almost similar to that of acrinathrin, but greater than acrinathrin for adults. Then the toxicity of this product to the natural enemies, Orius stringicollis and the pollinating insect Bombus terrestris, was evaluated using the body-dipping method or direct spray method. No acute toxicity of this product was observed on these non-target insects. Moreover, the influence of pyridalyl to the nest of Bombus terrestris was evaluated using the direct spray to the inside of the nest. No apparent influence of this compound was observed by 21 days after treatment. The cytotoxicity of pyridalyl to the Sf9 insect cell line and the CHO-K1 mammalian cell line was evaluated using the trypan-blue exclusion method. High toxicity to the insect cell line, but almost no toxicity to the mammalian cell line, was observed. Thus, pyridalyl exhibited high selectivity in cytotoxicity between the insect and mammalian cell line as well as in insecticidal activity among insect species. We infer pyridalyl may be useful for IPM programs of greenhouse cultivation system.     

Juvenile hormone antagonistic activity of secondary metabolites from Streptomyces lactacystinicus and their insecticidal activity against Plutella xylostella

Due to their specificity to target insects and low toxicity to non-target organisms, insect growth regulators (IGRs) have been promising alternatives to neurotoxic insecticides. Actinobacteria produce a wide range of secondary metabolites with insecticidal and insect growth regulatory activities. In this study, the culture media of 25 actinobacteria isolates showing high juvenile hormone antagonist (JHAN) activity were assessed for their insecticidal activity to identify novel IGR compounds toxic to Plutella xylostella. Among them, four isolates exhibited high insecticidal activity against 3rd instar larvae of P. xylostella. Two isolates of IMBL-1412 and IMBL-1823 showing relatively high insecticidal activities (greater than90% mortality) were identified as Streptomyces lactacystinicus based on colony color on various International Streptomyces Project (ISP) media and nucleotide sequences of the 16S rRNA gene. The ethyl acetate fractions of both isolates showed high JHAN and insecticidal activities against P. xylostella larvae at a concentration of 100 ppm when the culture media of these two isolates were extracted sequentially using hexane, ethyl acetate, and butyl alcohol. These results suggested that secondary metabolites of these actinobacterial isolates could be efficiently applied to develop novel IGR insecticides for the control of P. xylostella.     

Synthesis and insecticidal activities of novel 1,3,4-thiadiazole 5-fluorouracil acetamides derivatives: an RNA interference insecticide

A series of novel 1,3,4-thiadiazole 5-fluorouracil acetamides derivatives were designed and synthesized. Their structures were confirmed by infrared, (1)H NMR spectroscopy, and elemental analysis. The insecticidal activities against Tetranychus cinnabarinus and Aphis craccivora of these new compounds were evaluated. The bioassay tests showed that most of these title compounds possessed a good combination of stomach toxicity as well as contact toxicity against Tetranychus cinnabarinus and Aphis craccivora. In particular, the insecticidal activity of the title compound IVe against Aphis craccivora was better than the commercialized thiacloprid and was also comparable to another commercialized product, imidacloprid. The introduction of fluorines to meta and para-position of the benzene ring was essential for high bioactivity.     

THE INSECTICIDAL MATERIAL IN LEAVES OF PLANTS GROWING IN SOIL TREATED WITH PARATHION

After parathion solutions had been watered on to soil around the roots of cabbage plants with leaves infested with Brevicoryne brassicae, Myzus persicae or Pieris brassicae larvae, these leaves showed a toxic effect on the feeding insects. In comparable experiments, Aphis fabae on leaves of broad bean was not affected at dosages that damaged the plants. The effect on the cabbage plants was observed when the parathion was of the highest degree of purity, as shown by chemical tests and its negligible anticholinesterase activity, although it was greater with commercial grade material. It occurred when all possibility of a fumigant action was excluded.
When the roots of wheat plants were treated with solutions of pure parathion the leaf guttation fluid was toxic to Aëdes aegypti larvae and contained an active anticholinesterase. This was shown to be paraoxon; no parathion could be detected in the fluid. The paraoxon was formed rather slowly from the parathion when the roots and leaves of wheat seedlings were immersed in the solution but not in the presence of compost alone.
In plants treated with pure parathion the translocation of the paraoxon formed under the influence of the roots was sufficient to account for the toxic effects produced. With commercial parathion, analogues or isomers present as impurities may also be translocated. Both these sources of systemic poisons should be borne in mind when considering parathion treatment of greenhouse soil in which food crops are to be grown.     

Effect of Eugenia winzerlingii Extracts on Bemisia tabaci and Evaluation of its Nursery Propagation

The development of plant-derived products to control Bemisia tabaci Genn. (Hemiptera: Aleyrodidae) is an urgent need for production of horticultural crops. Plant extracts and essential oils of several species of the genus Eugenia (Myrtaceae) have shown insecticidal activity. In southern Mexico, leaf extracts from Eugenia winzerlingii showed nematicidal effect but its insecticidal properties have not been explored. Therefore, the objective of this study was to evaluate the insecticidal effect of aqueous and organic extracts from E. winzerlingii leaves on B. tabaci egg, nymph and adult stages, and else to explore its nursery propagation. Then, extracts of this species were obtained by maceration with different polarity solvents. Bioassays were carried out on Capsicum chinense leaves. Mortality assays showed that aqueous and total crude ethanol (TCE) extracts necrosed the eggs (LC50 = 0.21% w/v and 4.68 mg/mL, respectively), whereas hexane, ethyl acetate (ETA), residual ethanol and TCE extracts affected the nymphs (LC50 = 0.25 - 4.85 mg/mL). In adults, oviposition inhibition by free choice assay indicated that TCE and ETA extracts had major activity (EC50 = 14.62 and 27.86 μg/cm2, respectively). On other hand, the sexual and vegetative propagation of E. winzerlingii showed that this species can be easily cultivated by seeds. In conclusion, extracts of E. winzerlingii leaves are highly effective in controlling B. tabaci. TCE extract, in particular, was toxic to three stages of B. tabaci. This plant could be a potential alternative to develop a novel botanical insecticide to manage this destructive pest.     

The functional consequences of paraoxon exposure in central neurones of land snail, Caucasotachea atrolabiata, are partly mediated through modulation of Ca2+ and Ca2+-activated K+-channels

Toxicity of paraoxon has been attributed to inhibition of cholinesterase, but little is known about its direct action on ionic channels. The effects of paraoxon (0.3 microM-0.6 microM) were studied on the firing behaviour of snail neurones. Paraoxon significantly increased the frequency of spontaneously generated action potentials, shortened the afterhyperpolarization (AHP) and decreased the precision of firing. Short periods of high frequency-evoked trains of action potentials led to an accumulation in the depth and duration of post-train AHPs that was evidenced as an increase in time to resumption of autonomous activity. The delay time in autonomous activity initiation was linearly related to the frequency of spikes in the preceding train and the slope of the curve significantly decreased by paraoxon. The paraoxon induced hyperexcitability and its depressant effect on the AHP and the post-train AHP were not blocked by atropine and hexamethonium. Calcium spikes were elicited in a Na+ free Ringer containing voltage dependent potassium channel blockers. Paraoxon significantly decreased the duration of calcium spikes and following AHP and increased the frequency of spikes. These findings suggest that a reduction in calcium influx during action potential may decrease the activation of calcium dependent potassium channels that participate in AHP generation and act as a mechanism of paraoxon induced hyperexcitability.