The discovery of pyridalyl: a novel insecticidal agent for controlling lepidopterous pests

Synthesis of analogues of two compounds with known insecticidal activity, both of which contain a 3,3-dichloro-2-propenyloxy group, produced 2-(trifluoromethyl)-4-phenoxyphenyl 3,3-dichloro-2-propenyl ether, which had weak activity against lepidopterous larvae. Structural modifications around this lead compound led to the development of pyridalyl [Pleo, S-1812; 2,6-dichloro-4-(3,3-dichloroallyloxy)phenyl 3-[5-(trifluoromethyl)-2-pyridyloxy]propyl ether], which belongs to a new class of insecticides. Pyridalyl gives very good control of various lepidopterous and thysanopterous pests on cotton and vegetables, without phytotoxicity. It controls populations of Heliothis virescens F and Plutella xylostella (L) which are resistant to various currently used insecticides. It also produces unique insecticidal symptoms, so it may have a different mode of action from other existing insecticides. Pyridalyl is also less harmful than existing insecticides to various beneficial arthropods, so it should provide an important tool in IPM and insecticidal management programmes for the control of lepidopterous and thysanopterous pests. The first market introduction is expected in Japan and some Asian countries in the years between 2004 and 2005.     

Fenoxycarb,an insect growth regulator with juvenile hormone activity: A candidate for Heliothis virescens (F.) control on cotton

Tobacco budworm eggs, deposited on cotton plants (Gossypium hirsutum L.) treated with fenoxycarb, do not produce viable larvae. The insects die either at the end of embryonic development or during 1st-2nd larval instars, even when the larvae hatching on the treated leaves are transferred to untreated plants. This ovo-larvicidal activity and indications of good foliar persistence make fenoxycarb a promising candidate for the control of tobacco budworm on cotton. This type of application could open new aspects for the control of lepidopterous pests with this novel compound.     

The kinetics of insecticide action. Part III: The use of stochastic modelling to investigate the pick-up of insecticides from ULV-treated surfaces by larvae of Spodoptera littoralis boisd

The pick-up of pesticide by lepidopterous larvae walking across ultra-low volume pesticide treated surfaces has been stochastically modelled and simulated using a computer. The duration of the random walk was considered as a series of small, discrete time intervals during which the mode of pick-up varied, depending upon the behavioural state (resting, feeding or walking) of a larva. Estimates can be obtained for the total mass picked up by the larva (gross) and the net amount eliminated, the internal exposure to insecticide, and the proportion of insects knocked down and killed with increasing time. The results of the simulation of Spodoptera littoralis larvae confined to permethrin-treated surfaces were in agreement with experimental data, and suggested that a high pick-up of insecticidal droplets resulted from adhesion of the pesticide to larvae following encounter. However, the availability of drops at the leaf surface decreased with time, probably as a result of droplet spread and subsequent uptake by the cuticular waxes. Droplet stability on leaf surfaces may be related to droplet size.     

苏云金芽孢杆菌防治柑桔害虫的后效作用

1985年在广西隆安县从未施过Bt菌剂的柑桔园中喷洒Bt菌剂(Bt5a5b).1986年对该园的土壤和柑桔叶片取样分析,结果表明,施菌区土壤及叶片的Bt(H5a5b)检出率均高于不施菌剂的对照区。1987年检测果园的鳞翅目害虫,施菌区活虫的Bt检出率为51.4％,其中Bt(H5a5b) 占60.2％,死虫的Bt检出率为81.3％,其中Bt(H5a5b)占67.1％。对照区活虫Bt检出率为20.5％,其中Bt(H5a5b)占34.3％,死虫的Bt检出率为35.7％,其中Bt(H5a5b)占10％。说明施用菌剂两年后,果园中仍残留一定量的Bt,对害虫有致死的作用。     

Resistance selection and mechanisms of oriental tobacco budworm (Helicoverpa assulta Guenee) to indoxacarb

The oriental tobacco budworm, Helicoverpa assulta, is one of the most destructive pests for numerous commercial crops, and these organisms are responsible for enormous economic losses in Chinese agriculture. Insect larvae often feed within host plant fruits, providing protection from many currently used insecticides and making field control of H. assulta very difficult. Owing to its novel mode of action, high insecticidal activity, and low mammalian toxicity, the nonsystemic insecticide indoxacarb has been considered a promising alternative for the control of lepidopterous pests of agricultural significance. Indoxacarb evidences an elevated insecticidal activity against H. assulta. After 13 generations of selection with indoxacarb and bifenthrin insecticides under laboratory conditions, the LC₅₀ of these compounds for H. assulta increased by 4.19-fold and 10.67-fold, respectively. The synergists diethyl maleate (DEM) and triphenyl phosphate (TPP) increased indoxacarb toxicity by 2.76-fold and 4.10-fold in resistant strains and, comparatively, 1.58-fold and 1.75-fold in susceptible strains, suggesting that carboxylesterase (CarE) and glutathione-S-transferases (GSTs) may be involved in the development of indoxacarb resistance in H. assulta. Activity and kinetic parameters observed in detoxification enzymes further demonstrated that the enhanced activity of CarE and GSTs may be critical in development of indoxacarb resistance in H. assulta. The data provides a foundation for further study of the indoxacarb resistance mechanism observed in H. assulta and the rational use of indoxacarb as a rotation insecticide with other insecticide classes for the control of H. assulta.     

Quantitative structure–activity studies of insect growth regulators: XVI. Substituent effects of dibenzoylhydrazines on the insecticidal activity to Colorado potato beetle Leptinotarsa decemlineata

Insecticidal activity against the Colorado potato beetle, Leptinotarsa decemlineata, was measured for a series of substituted N-tert-butyl-dibenzoylhydrazines, in which one of the benzoyl moieties closer to the tert-butyl group was fixed as being 2-chloro-substitued and the other variously substituted singly or doubly. The effects of substituents on the activity were quantitatively analysed using the classical quantitative structure–activity relationship (QSAR) procedure. The activity against the Colorado potato beetle increases with the molecular hydrophobicity. In addition, various types of steric effect are at work, depending upon the positions. Hydrogen-bonding acceptor substituents at the para position enhance the activity. There seem to be threshold (or optimum) values, albeit position-dependent, in the molecular hydrophobicity, above which the activity starts to decrease. This biphasic contribution of the molecular hydrophobicity to activity against coleopterous larvae is the most conspicuous difference in substituent effects from those found for similar compounds against lepidopterous pest insects, and may be the basis of the variations in the activity spectrum for certain compounds in this series. The introduction of bulkier substituents into the meta- and para-positions of the benzene ring, apart from the tert-butyl group, is unfavorable to activity. LD₅₀ values against Colorado potato beetle larvae of methoxyfenozide (RH-2485) and tebufenozide (RH-5992) were in the order of 10⁻⁷ mol per insect, whereas those of RH-5849, and halofenozide (RH-0345) were very low, 10⁻⁹–10⁻¹⁰ mol per insect being selective to the coleopterous larvae. © 1999 Society of Chemical Industry     

Interactions among herbivores,microbial insecticides and crop plants

Knowledge of the interactions among lepidopterous insects, microbial insecticides and plants is either lacking or incomplete. In some of the interactions, plant allelochemicals antagonized the insecticidal activity of the microbe by means of feeding reduction. In others, microbe activity was enhanced either by causing insect toxicity or by a potentiation of the crystal protein. Nutritional evaluations of the interactions amongHeliothis virescens. Bacillus thuringiensis crystal protein and tannin showed that microbe toxicity in the larva was antagonized by this phytochemical.     

诱集植物香根草对大螟幼虫营养作用及消化酶的影响

香根草能够有效诱集水稻害虫大螟Sesamia inferens(Walker)在其上产卵,但孵化出的幼虫在香根草上不能完成生活史,香根草对大螟幼虫表现出致死作用。为明确香根草对大螟幼虫致死的作用机制,本研究分析测定了取食香根草后大螟幼虫的营养指标及体内消化酶的变化。结果表明,取食香根草能显著影响幼虫的生长效率及体内消化酶活性。与取食水稻的幼虫相比,取食香根草的幼虫粗生长效率ECI和净生长效率ECD显著降低;除蔗糖酶外,其他消化酶的活性在特定龄期呈显著下降的趋势,具体表现为4龄幼虫蛋白酶比活力、2~4龄幼虫淀粉酶比活力和1~4龄幼虫海藻糖酶比活力显著降低,而1~3龄幼虫蔗糖酶比活力显著提高。本文为进一步阐明香根草对大螟的致死作用机制奠定了基础,为开发以香根草为基础的稻螟绿色防控新技术提供了理论依据。     

Toxicity and biochemical study of two insect growth regulators, buprofezin and pyriproxyfen, on cotton leafworm Spodoptera littoralis

Lethal and sublethal effects of two insect growth regulators (IGRs) buprofezin and pyriproxyfen were evaluated on larvae of cotton leafworm Spodoptera littoralis. Activity of chitinase and polyphenol oxidase (PPO) in surviving larvae after treatment was carried out in order to investigate the biochemical influences of these compounds. The compounds were low toxic against the larvae at 0.05, 0.1, 0.25, 0.5, and 1.0-fold of the field application rate. However, the overall mortalities within 6 days of feeding at 2.0-fold were 46.67% and 100% for buprofezin and pyriproxyfen, respectively. Larval weight gain was considerably decreased as concentration increased. Pyriproxyfen showed high antifeedant activity in a concentration-dependent manner, and larvae stopped to eat from the third day with high dose. Conversely, buprofezin did not significantly show antifeedant except with high concentration (3000 mg (a.i.)/kg diet) that gave 80.68%. The high doses of both compounds showed adverse effects on pupae, and emergence of adults. Buprofezin at the recommended dose (1500 mg (a.i.)/kg diet) caused 93.33% pupation and 53.33% emergence of adults. Otherwise, pyriproxyfen caused 21.33% pupation and zere emergence of adults at the recommended dose (75 mg (a.i.)/kg diet) compared to 100% pupation, and 96.30% emergence of adults in the control. Both compounds varied in their influences on chitinase and PPO activity, and these enzymes could have relation with toxicity of buprofezin and pyriproxyfen against S. littoralis larvae.     

A biochemical approach to potentiate the activity ofBacillus thuringiensis against corn borers

Due to the fact that the persistence ofBacillus thuringiensis (B.t.) is very short in the field as affected by exposure to ultraviolet radiation, some biochemical approaches have been adopted in an attempt to increase potentiation of the pathogen against the two lepidopterous corn borers,Chilo agamemnon andOstrinia nubilalis. These approaches were based on the incorporation of some selected non-toxic chemical compounds with different modes of action with the endotoxin ofB.t. fed to the larvae and thus resulting in its potentiation. Among the compounds tested, some representatives of inorganic salts, organic acids, protein and lipid solubilizing agents, amino acids and amides showed an obvious potentiation to the endotoxin activity against the target insects. Inorganic salts, such as, calcium oxide, calcium carbonate, zinc sulphate and potassium carbonate at 0.1% potentiated the activity of the product Dipel 2X (B.t. var.kurstaki) against the two tested species in varying degrees. With regard to protein solubilzing agents, urea, sodium thioglycollate and EDTA enhanced the potency ofB.t. againstO. nubilalis with a fold increase of 1.4–2.3. The lipid emulsifying agent Tween 80 (0.5%), caused 1.3 fold increase in the potency ofB.t. With respect toC. agamemnon, sodium thioglycollate and EDTA (0.1%) were effective in potentiating the activity ofB.t. with fold increase of 3.1 and 1.2, respectively, while urea caused a decrease in the potency ofB.t as compared with the control. The lipid emulsifying agent Tween 80 (0.5%) caused 1.3 fold increase in the potency ofB.t. The potentiating effect of aromatic compounds is not obvious with respect to the tested insect species. With amino acids and amides, it appears that some of the tested compounds enhanced the potency ofB.t. against the tested insect species but in varying degrees. The mode of action of the tested compounds has been discussed in the light of the results obtained.     

The importance of nerve terminal depolarization in pyrethroid poisoning of insects

The effects of several pyrethroids and DDT were examined on neuromuscular preparations from larvae of Musca domestica, Culex quinquefasciatus, Anopheles stephensi, and Trichoplusia ni, in order to determine the importance of the type I effect (repetitive firing) and the type II effect (increased miniature excitatory postsynaptic potential (mepsp) rate, indicating nerve terminal depolarization) in the poisoning process. α-Cyano pyrethroids were very potent in increasing mepsp rate, and although DDT and non-α-cyano compounds were more potent at inducing repetitive firing, all these compounds increased mepsp rate at higher concentrations. A variety of evidence showed that the mepsp rate-increasing activity could be an important factor in toxicity: among all of the compounds, there was a positive correlation between toxicity and mepsp rate-increasing activity; mepsp rate-increasing activity had a negative temperature dependence; nerves of kdr larvae in vitro were resistant to the mepsp rate-increasing activity, commensurate with resistance level; and finally, increased mepsp rate and neuromuscular block were observed in poisoned insects, associated with paralysis. Among type I compounds, repetitive firing activity was correlated negatively with toxicity, but positively with knockdown activity.     

炔类化合物对亚洲玉米螟拒食活性和电生理反应

利用饲料柱法测定了人工合成的 9个共轭二炔和 3个单炔类化合物对亚洲玉米螟 Ostrinia furnacalis(Guene'e) 5龄幼虫的拒食活性 ,并利用顶端记录技术 ,诱发该虫栓锥感受器感受细胞的电位脉冲反应。结果表明 :受试的炔类化合物对亚洲玉米螟幼虫具有不同程度的拒食活性 ,特别是化合物 2 (6,6-二甲基-2,4-庚二炔-1-醇、化合物 3(2,4-己二炔-1,6-二醇 )、化合物 9(1-苯基-2 ,4-己二炔 )和化合物 11(3-溴-2-丙炔-1-醇 ) ,实验剂量为 500μg/g饲料时 ,2 4 h非选择性拒食率在 80%左右。电生理测定结果表明 :浓度为 1mg/mL时 ,该系列化合物刺激中栓锥感受器能诱发感受细胞发放不同频率的脉冲和振幅 ,脉冲频率在 8.30～31.00imp/s,振幅在 400～1000μV之间。刺激侧栓锥感受器 ,也能诱发感受细胞发放不同频率的脉冲 ,脉冲频率在 6.00～ 15.66imp/s之间。将化合物诱发中栓锥感受细胞电位脉冲频率与生测拒食活性进行比较 ,发现二者存在一定程度的相关性。在剂量 -发放频率测试中 ,测得化合物 9诱发栓锥感受器脉冲频率具有浓度依赖性。     

Validation of RNA interference in western corn rootworm Diabrotica virgifera virgifera LeConte (Coleoptera: Chrysomelidae) adults

BACKGROUND: RNA interference (RNAi) is commonly used in insect functional genomics studies and usually involves direct injection of double‐stranded RNA (dsRNA). Only a few studies have involved exposure to dsRNAs through feeding. For western corn rootworm (Diabrotica virgifera virgifera) larvae, ingestion of dsRNA designed from the housekeeping gene, vacuolar ATPase (vATPase) triggers RNAi causing growth inhibition and mortality; however, the effect of dsRNA feeding on adults has not been examined. In this research, WCR adults were fed with vATPase‐dsRNA‐treated artificial diet containing a cucurbitacin bait, which is a proven feeding stimulant for chrysomelid beetles of the subtribe Diabroticina to which rootworms belong. RESULTS: Real‐time PCR confirmed suppression of vATPase expression and western blot analysis indicated reduced signal of a protein that cross‐reacted with a vATPase polyclonal antiserum in WCR adults exposed to artificial diet treated with dsRNA and cucurbitacin bait. Continuous feeding on cucurbitacin and dsRNA‐treated artificial diet resulted in more than 95% adult mortality within 2 weeks while mortality in control treatments never exceeded 20%. CONCLUSIONS: This research clearly demonstrates the effect of RNAi on WCR adults that have been exposed to dsRNA by feeding and establishes a tool to screen dsRNAs of potential target genes in adults. This technique may serve as an alternative to target screening of larvae which are difficult to maintain on artificial diets. Copyright © 2011 Society of Chemical Industry     

Toxicity of the chitin synthesis inhibitors,diflubenzuron and its dichloro-analogue,to Spodoptera littoralis larvae

The activities of the chitin synthesis inhibitors, diflubenzuron and PH 60–38, against Spodoptera littoralis larvae were assayed by feeding treated alfalfa or poisoned wheat bran baits, by allowing the larvae to imbibe sucrose-containing aqueous dispersions of the compounds, and by injection into larvae. PH 60–38 was less active than diflubenzuron. On alfalfa, diflubenzuron had to be fed for at least 2 days to prevent formation of normal pupae and emergence of adults. For very big (480–540 mg) larvae, feeding diflubenzuron at concentrations of 50 mg/litre for 2 days or 2.5 mg/litre for 3 days prevented adult emergence. For 200–250 mg larvae, this was achieved by feeding concentrations of 100 mg/litre for 2 days, 5 mg/litre for 3 days or 3.5 mg/litre for 4 days. In all larvae > 150 mg, mortality in feeding experiments occurred in the prepupal or the pupal stage. Only with 30–50 mg and 100–150 mg larvae was there considerable mortality during moults between larval instars, the larvae being unable to liberate themselves from the old larval skins and head capsules. Diflubenzuron incorporated into wheat bran baits at concentrations of from 2.5 to 10 000 μg/g killed approximately 70–90% of the insects. When imbibed, diflubenzuron was much less toxic as a wettable powder than as a liquid formulation but the two formulations were equitoxic when injected into the larvae.     

天然杀线虫先导化合物Waltherione A类似物的合成及杀线虫活性

为了找出天然杀线虫先导生物碱Waltherione A的关键药效基团并简化其结构,以2,3-二甲氧基苯甲醛和3,4-二甲氧基苯甲醛为原料,经过分子内傅克烷基化反应形成苯并七元氧桥环,并用不同的取代基与桥环相连,合成了12个Waltherione A类似物,其中8个化合物未见文献报道,所有目标化合物的结构均通过核磁共振氢...     

Design, semisynthesis and insecticidal activity of novel podophyllotoxin derivatives against Brontispa longissima in vivo

In an attempt to find the effective phytopesticides, a series of novel podophyllotoxin derivatives were firstly synthesized and preliminarily tested for their antifeedant and insecticidal effects against the fifth-instar larvae of Brontispa longissima. The different antifeedant and insecticidal activity ranges of compounds 3a-l showed that variations of NR₁R₂ groups in the 4-position of podophyllotoxin skeleton markedly affected the activity profiles of this compound class, and some important SAR information has been revealed from it. To clarify their mode of action of insecticidal activity, the docking models as well as tubulin inhibitory effect of representative compound 3i were also investigated, and the result indicated that the insecticidal activity of these compounds was due to the tubulin inhibitory effect of these derivatives, thereby possibly providing some useful information for rational designs of novel podophyllotoxin-based insecticides.     

缩节胺处理棉株对棉铃虫的影响初报

棉株施用缩节胺后能减少棉铃虫(Heliothis armigera Habner)在棉株上的落卵量48.8%—88%,田间虫量减少39.5%—77.3%,取食嫩叶、花蕾后的2龄幼虫体重下降、发育历期延长,死亡率增加,化蛹率和羽化率都有下降,总的生存率降低了57.62%。测定表明施用缩节胺后,棉株各部组织内棉酚有增加趋势,以蕾内增加较多,为49%—92.1%,铃壳次之,为13.8%—65.5%,叶内较少,为3.6%—39.7%。而单宁量除大铃壳内有增外,大多下降。施用次数与剂量的增加,与棉酚量的提高有共同趋势。花蕾期施用,棉酚量的增加高于花铃期。     

The biology,damage and control of the poplar and willow borer,Cryptorrhynchus lapathi

Cryptorrhynchus lapathi has a two-year life cycle, during which it hibernates once as a first instar larva, and again as an adult. As a rule the adults emerge, feed and lay eggs in the even years, while the larvae have their main feeding period in the odd years. The species is harmful to poplar and willow, not only by its own feeding, but also indirectly by facilitating entrance of other insects and infection by micro-organisms. Control by insecticides should preferably not take place in the adult, but in the larval stage. In both cases very poisonous chemicals are required, but the amounts needed for controlling the larvae are smaller than those needed to control the adults and the techniques for applying them entail less risk of poisoning other organisms.     

The Effects of Agricultural Practices on Carabidae in Temperate Agroecosystems

Ground beetles (Coleoptera, Carabidae) occur in all temperate agroecosystems, and have been implicated as predators of many pests, including aphids, lepidopterous larvae, and slugs. Most are polyphagous, and some are primarily spermophagous. The species assemblage present in any particular crop is determined by multiple factors, but usually comprises a limited number of abundantly active species, which may be common to many crop types. Abiotic soil factors, especially soil type and moisture status are important in determining the species present. Crop type affects the carabid assemblage indirectly through cultivation practices and microclimatic changes. Any soil cultivation affects the carabid assemblage, but studies comparing ploughing with reduced tillage have shown varying results, according to local conditions. Pesticides, especially insecticides have a localised and short-term effect, as many carabids rapidly re-invade sprayed crops. The long-term effect of pesticide usage at a landscape scale is, however, more difficult to predict, and may have contributed to the observed decline in carabid diversity in the wider countryside. Whilst fertiliser application is generally beneficial to carabids, comparisons of conventional and organic farming systems suggest that localised short-term variations in species abundances are more important than the overall farming system used. Non-crop habitats are very important to Carabidae, as many use adjacent hedges and field margins for shelter, breeding or dispersal. But other features such as roads may act as barriers to dispersal. It is concluded that further measures need to be taken if Carabidae are to realise their potential in integrated pest management systems.     

转基因棉对棉铃虫幼虫生长及中肠蛋白酶活性的影响

室内测定了转慈姑蛋白酶抑制素(API)基因棉对棉铃虫幼虫的抗虫活性及对中肠蛋白酶活性的影响。结果表明，以转基因棉饲养棉铃虫，对幼虫拒食率24h达76．49％，72h达80．57％，试虫体重在取食48h后显著下降，72h后较对照低54．04％。试虫取食转API基因棉后，中肠的强碱性胰蛋白酶和类胰凝乳蛋白酶活性显著降低，取食24、48h后的强碱性胰蛋白酶酶活性分别只有对照组的68．1l％和55．89％；类胰蛋白酶活性分别为对照组的85．87％和64．61％；对弱碱性类胰蛋白酶活性不明显。显示转API基因棉对棉铃虫幼虫中肠蛋白酶的抑制作用与对棉铃虫生长发育的阻滞有良好的相关性。