Enhanced repellency of binary mixtures of Zanthoxylum piperitum pericarp steam distillate or Zanthoxylum armatum seed oil constituents and Calophyllum inophyllum nut oil and their aerosols to Stomoxys calcitrans

BACKGROUND: The repellency to stable fly, Stomoxys calcitrans (L.), of Zanthoxylum piperitum (L.) DC pericarp steam distillate (ZP‐SD), Zanthoxylum armatum DC seed oil (ZA‐SO) and their constituents alone or in combination with Calophyllum inophyllum L. nut oil (CI‐NO), as well as six aerosol formulations containing ZP‐SD or ZP‐SO and CI‐NO, was compared with that of a synthetic repellent, DEET, using an exposed human hand bioassay. RESULTS: At 0.20 mg cm^?2, ZP‐SD treatments resulted in 91 and 68% repellency following 30 and 60 min exposure respectively, while DEET gave 100 and 84% repellency. ZA‐SO was less effective than ZP‐SD. At 0.2 mg cm^?2, the most active constituents, cuminaldehyde, cuminyl alcohol, limonene and methyl cinnamate, gave 82, 74, 74 and 64% repellency at 30 min respectively, but DEET gave 100 and 87% repellency at 30 and 60 min. An increase in effectiveness and duration of repellency was produced by binary mixtures of ZP‐SD, ZA‐SO or bioactive constituents (each 0.01 mg cm^?2) and CI‐NO (0.99 mg cm^?2). The repellency of aerosols containing 2.5% ZP‐SD or 2.5% ZA‐SO and 2.5% CI‐NO was comparable with that of 5% DEET aerosol. CONCLUSION: Mixtures formulated from ZP‐SD, ZA‐SO or bioactive constituents and CI‐NO could be useful as potential repellents for the control of stable fly populations in light of global efforts to reduce the level of highly toxic synthetic repellents. Copyright © 2010 Society of Chemical Industry     

Inhibition of DNA synthesis by diflubenzuron in pupae of the stable fly Stomoxys calcitrans (L.)

Biochemical assays of stable fly pupae treated with diflubenzuron at the white prepupal stage and then injected with either [³H]thymidine or [¹⁴C]thymidine showed no differences in uptake of the thymidine at 0–4, 0–24, 20–21, or 22–24 hr after injection of the radiolabeled thymidine. However, at 32–36 hr the diflubenzuron pupae incorporated only 10–11% of the amount of labeled thymidine incorporated by the untreated pupae. Autoradiographs taken from diflubenzuron-treated pupae at 22–24 and 32–36 hr after injection of the labeled thymidine showed that a reduction in DNA synthesis had occurred in cells originating from the imaginal epidermal histoblasts. The reduction in DNA synthesis at 22–24 hr was not detectable by the biochemical assay since the number of proliferating epidermal cells was too small a proportion of the total number of cells undergoing histogenesis at this time period. Thus, the insect growth regulator, diflubenzuron, appears to be cell specific in this species of fly in that the reduction in DNA synthesis is observed only in cells originating from the imaginal epidermal histoblasts. However, it is not known at this time whether this effect is primary or secondary.     

An olfactometer for measuring the repellent effect of chemicals on the stable fly Stomoxys calcitrans (L.)

An olfactometer is described that permits the evaluation of chemicals acting in the vapour phase against the stable fly Stomoxys calcitrans (L.). Hungry flies, held in a metal frame cage covered with soft gauze, are attracted to a target held adjacent to one side of the cage, and emitting an attractive airflow. Flies landing on the target are counted at intervals of 15s. Flies starved for 24h were tested in the olfactometer when 2, 3 and 4 days old. With the exception of the first exposure of the 4-day-old flies, all the flies of the three ages showed greater than 80% attraction to the olfactometer target after exposure for 2 min, for each of four successive exposures at 10-min intervals. For all ages there was a significant increase in attraction at the second exposure but no further increase with subsequent exposures. It is likely that the sensillae, stimulated by the first exposure, subsequently responded faster. Eight chemicals were incorporated into the airflow behind the target to test their effect on flies. Permethrin (a low vapour pressure pyrethroid) and crotoxyphos (a low vapour pressure organophosphate) did not act in the vapour phase. Empenthrin (a high vapour pressure pyrethroid) and dichlorvos (a high vapour pressure organophosphate) both exhibited the toxic effect of knock-down on the flies without repellency. Oil of citronella and citronellol, two known fly repellents, gave a general reduction of attraction that was dose dependent; fewer flies found the target and those that did stayed a shorter length of time. Natural pyrethrum gave a similar effect to these two at lower concentrations, but at higher concentrations, it also showed a repellent effect. N,N-Diethyl-m-toluamide gave a low reduction in attraction. The olfactometer shows potential for use with other flying insects, both to observe the effects of an insecticide and also to study the behavioural responses in the absence of insecticides.     

六种植物精油对褐飞虱和稻虱缨小蜂行为的影响

为研发基于植物精油的褐飞虱Nilaparvata lugens驱避剂和稻虱缨小蜂Anagrus nilaparvatae引诱剂,利用嗅觉仪测试了6种植物精油在不同浓度下对褐飞虱和稻虱缨小蜂的行为反应。结果表明,6种植物精油对褐飞虱和稻虱缨小蜂行为的影响具有种类差异性,不同植物精油对昆虫的行为影响有较大差异。此外,褐飞虱和稻虱缨小蜂对植物精油的嗅觉反应还与精油浓度有关,精油浓度范围在100～5 000 mg/L时,山楂油、白木香油、金银花油、肉桂油和鱼腥草油对褐飞虱雌成虫表现出明显的趋避效果,其中山楂油和金银花油的驱避效果最好,二者在100、500、1 000和5 000 mg/L这4个浓度下均能显著驱避褐飞虱。0.1 mg/L和1 mg/L浓度的山楂油、0.1 mg/L浓度的白木香油和1 mg/L浓度的丁香花蕾油对稻虱缨小蜂雌成虫有较强的吸引力。较高浓度10 mg/L的鱼腥草油对稻虱缨小蜂有明显的驱避性。表明植物精油可以明显地影响褐飞虱和稻虱缨小蜂的行为,可作为行为调控物在"推-拉"策略中防控褐飞虱。     

Insecticidal and repellent properties of nine volatile constituents of essential oils against the American cockroach,Periplaneta americana (L.)

The toxic and repellent properties of nine major constituents of essential oils, comprising benzene derivatives and terpenes, were evaluated against Periplaneta americana (L.). Contact and fumigant toxicities to adult females and repellency to nymphs were determined. The decreasing order of knockdown activity via contact was methyl-eugenol>isosafrole=eugenol>safrole. The killing effect via contact was in the order eugenol=methyl-eugenol=isosafrole>safrole. Fumigant toxicity was only observed for safrole and isosafrole, with safrole being the more potent. Isoeugenol and the tested terpenes had neither contact nor fumigant toxic effect. The decreasing order of repellency to nymphs was safrole>isosafrole>methyl-eugenol=α-pinene> eugenol>isoeugenol. The benzene derivatives were generally more toxic and repellent to P. americana than the terpenes. The distance of the side chain double bond from the aromatic ring and the substitution of a methoxy group to these compounds appeared to be important determinants of their toxicity and repellency. © 1998 Society of Chemical Industry     

Response of winter wheat (Triticum aestivum L.) and weeds to tank mixtures of 2,4-D plus MCPA with clodinafop propargyl

Field and greenhouse experiments were conducted in 2004 and 2005 to study weed control and the response of winter wheat to tank mixtures of 2,4-D plus MCPA with clodinafop propargyl. The field experiments were conducted at Yazd and Oroumieh, Iran, with factorial combinations of 2,4-D plus MCPA at 0, 975, and 1300 g ai ha⁻¹ and with clodinafop propargyl at 0, 64, 80, 96, and 112 g ai ha⁻¹ in four replications. The greenhouse experiments further evaluated the effect of these tank mixtures on weed control, where each herbicide mixture was considered as one treatment and the experiment was established in a randomized complete block design with four replications. In the field experiments, the herbicides were applied at wheat tillering, while in the greenhouse experiments they were applied at the beginning of the tillering stage and at the four-leaf stage of the grass and broadleaf weeds, respectively. The results indicated antagonistic effects between 2,4-D plus MCPA and clodinafop propargyl. The best tank mixture with regard to weed control efficacy was 2,4-D plus MCPA at 975 g ai ha⁻¹ with clodinafop propargyl at 96 g ai ha⁻¹. The wheat grain yield was also increased by the tank mixture of clodinafop propargyl with 2,4-D plus MCPA. Generally, to inhibit clodinafop propargyl efficacy reduction due to tank-mixing with 2,4-D plus MCPA, it is recommended that the application dose of 64 g ai ha⁻¹ should be increased to 96 g ai ha⁻¹.     

Behavioural responses of the maize weevil,Sitophilus zeamais,to host (stored‐grain) and non‐host plant volatiles

BACKGROUND: Four‐arm olfactometer bioassays were conducted to assess the behavioural responses of the adult maize weevil, Sitophilus zeamais (Motschulsky) (Coleoptera: Curculionidae), to harvested seeds of host plants, i.e. white maize, yellow maize (Zea mays L.) and winter wheat (Triticum aestivum L.) (Poaceae), and non‐host plant materials, i.e. alligator pepper, Aframomum melegueta (Rosk) K. Schum (Zingiberaceae), rhizomes of ginger, Zingiber officinale (Roscoe) (Zingiberaceae), and West African black pepper, Piper guineense Thonn and Schum (Piperaceae). Additional bioassays with host plant volatiles were conducted in the presence of three doses of non‐host plant materials. RESULTS: Both sexes of the weevil showed strong attraction to maize and wheat seed volatiles, but were significantly repelled (P < 0.001) by odours from A. melegueta, Z. officinale and P. guineense. Furthermore, S. zeamais avoided maize and wheat seeds presented in combination with the non‐host plant material at 10% (w/w) and 33% (w/w) levels. CONCLUSIONS: A. melegueta, Z. officinale and P. guineense have the potential for use in the protection of stored grains by resource‐poor farmers with local access to these plants. Copyright © 2009 Society of Chemical Industry     

The role of cytochrome P450 monooxygenase in the different responses to fenoxaprop-P-ethyl in annual bluegrass (Poa annua L.) and short awned foxtail (Alopecurus aequalis Sobol.)

Herbicide resistance or tolerance in weeds mediated by cytochrome P450 monooxygenase is a considerable problem. However, cytochrome P450 mediated resistance or tolerance in weeds was less studied. Thus, in this work, the role of the cytochrome P450 monooxygenase in the different responses of Poa annua and Alopecurus aequalis to fenoxaprop-P-ethyl was studied. We found that the effect of fenoxaprop-P-ethyl could be synergized by piperonyl butoxide (PBO) in P. annua, but not by malathion. After being treated with fenoxaprop-P-ethyl (containing mefenpyr-diethyl), the contents of cytochrome P450 and cytochrome b₅ in P. annua increased significantly compared to plants treated with mefenpyr-diethyl only or untreated plants. However, the increase was less in A. aequalis, which was susceptible to fenoxaprop-P-ethyl. The activities of ρ-nitroanisole O-demethylase (PNOD), ethoxyresorufin O-deethylase (EROD), ethoxycoumarin oxidase (ECOD) and NADPH-dependent cytochrome P450 reductase mediated by cytochrome P450 monooxygenase increased in P. annua after treatment with fenoxaprop-P-ethyl, especially the activities of ECOD and cytochrome P450 reductase. Besides this, cytochrome P450 monooxygenase activity toward fenoxaprop-P-ethyl in P. annua increased significantly compared to untreated or treated with mefenpyr-diethyl plants and treated or untreated A. aequalis. Cytochrome P450 monooxygenase may play an important role in the different responses to fenoxaprop-P-ethyl in P. annua and A. aequalis.     

Responses of the cabbage seedpod weevil,Ceutorhynchus obstrictus (Marsham) (Coleoptera: Curculionidae), to seed treatments of canola (Brassica napus L.) with the neonicotinoid compounds clothianidin and imidacloprid

BACKGROUND: The cabbage seedpod weevil, Ceutorhynchus obstrictus (Marsham), is a major pest in the production of canola (Brassica napus L.) in North America and Europe, and effective population control is often essential for economical crop production. In North America, neonicotinoid insecticides have been used for several years in canola as seed treatments for reducing herbivory by flea beetles. The neonicotinoids clothianidin and imidacloprid were investigated to determine their effects on preimaginal development and on emergence of new‐generation adults of C. obstrictus in comparison with effects of lindane, a chlorinated hydrocarbon seed treatment. RESULTS: Mean numbers of second‐ and third‐instar larvae were significantly higher in plants seed‐treated with lindane than in plants treated with the neonicotinoid compounds, even though weevil oviposition was similar for all treatments. Emergence of new‐generation adults was reduced by 52 and 39% for plants seed‐treated with clothianidin and imidacloprid, respectively, compared with emergence from plants treated with lindane. CONCLUSION: Seed treatment with both clothianidin and imidacloprid produced systemic insecticidal effects on larvae of C. obstrictus, with clothianidin slightly more effective than imidacloprid. Use of clothianidin or imidacloprid as seed treatments can comprise an important component in the integrated management of cabbage seedpod weevil in canola. Copyright © 2009 Society of Chemical Industry     

Resistance of codling moth, Cydia pomonella (L.) (Lepidoptera: Tortricidae), larvae in Michigan to insecticides with different modes of action and the impact on field residual activity

BACKGROUND: The codling moth is one of the principal pests of apple in the world. Resistance monitoring is crucial to the effective management of resistance in codling moth. Three populations of codling moth in neonate larvae were evaluated for resistance to seven insecticides via diet bioassays, and compared with a susceptible population. In addition, apple plots were treated with labeled field rate doses of four insecticides. Treated fruit were exposed to neonate larvae of two populations from commercial orchards. RESULTS: Two populations of codling moth expressed two‐ and fivefold resistance to azinphos‐methyl, seven‐ and eightfold resistance to phosmet, six‐ and tenfold resistance to lambda‐cyhalothrin, 14‐ and 16‐fold resistance to methoxyfenozide and sixfold resistance to indoxacarb, but no resistance to acetamiprid and spinosad. The impact of the resistance to azinphos‐methyl, measured as fruit damage, increased as the insecticide residues aged in the field. In contrast, fruit damage in methoxyfenozide‐ and lambda‐cyhalothrin‐treated fruit was observed earlier for resistant codling moth. No differences in efficacy were found for acetamiprid. CONCLUSIONS: Broad‐spectrum insecticide resistance was detected for codling moth. Resistance to azinphos‐methyl, lambda‐cyhalothrin and methoxyfenozide was associated with reduced residual activity in the field. Broad‐spectrum resistance presents serious problems for management of the codling moth in Michigan. Copyright © 2008 Society of Chemical Industry