Synergism of teflubenzuron and chlorfluazuron in an acylurea-resistant field strain of Plutella xylostella L. (lepidoptera: Yponomeutidae)     

Fauziah Ismail  Denis J. Wright 《Pest management science》1992,34(3):221-226

Topical application of the synergists piperonyl butoxide (PB) and S,S,S-tributyl phosphorotrithioate (DEF) to second-instar larvae of a standard laboratory strain (FS) and an unselected Malaysian field strain (CH) of the diamondback moth Plutella xylostella had no significant effect on the toxicity of the acylurea insecticides, chlorfluazuron and teflubenzuron, in a subsequent leafdip bioassay. In contrast, pre-treatment with PB or DEF in acylurea-selected subpopulations of the CH strain with varying levels of cross-resistance to chlorfluazuron and teflubenzuron significantly increased (up to 34-fold and 28-fold, respectively) the toxicity of both compounds, suggesting that microsomal monooxygenases and esterases may be involved in resistance. The addition of a mineral oil, ‘Sunspray 6E’, to topically-applied chlorfluazuron consistently reduced its LD₅₀ value, and the effect of the oil appeared to be greatest on the most resistant population of P. xylostella. However, the effects of the oil were not significant (P > 0·05) and further studies are necessary to determine whether a penetration factor is present in the CH strain.  相似文献   

Speed of action and toxicity of acylurea insect growth regulators against Spodoptera exempta (Walk.) and Spodoptera littoralis (Boisd.) larvae: Effect of inter-moult age     

Tanya Fisk  Denis J. Wright 《Pest management science》1992,35(4):331-337

Ultra-low volume (ULV) spray bioassays at droplet densities (20–80 drops cm^?2) corresponding to field deposits were used to determine the efficacy of two acylurea insect growth regulators, teflubenzuron (‘Nomolt®’) and flufenoxuron (‘Cascade®’) against three different age groups of third-instar Spodoptera exempta and Spodoptera littoralis larvae. While no response (mortality and/or abnormal moulting with impaired ability to feed) was observed with one-day-old larvae until 48 h after treatment, two-day-old larvae showed some response (27–93% abnormal moulting and 3–10% mortality when larvae were sprayed; 80–100% abnormal moulting and up to 83% mortality when larvae and plants were sprayed) after 24 h and up to 100% mortality at 120 h. Studies with non-feeding, pre-moult larvae showed that cuticular uptake of acylureas was sufficient to affect an appreciable proportion of larvae after 24 h, with up to 100% mortality at 120 h. More detailed studies with pre-moult S. littoralis larvae showed that, while a few larvae which moulted between 1 and 5 h after treatment showed abnormal moulting to the L4 stage, a much larger proportion of larvae which moulted 6–20 h after treatment were affected. Previous studies with S. exempta have shown that different larval instars show similar levels of sensitivity to acylureas. The present work suggests that, while the age distribution within instars has little influence on the end-point mortality of acylureas, it can profoundly modify the speed of response, the majority of larvae within an instar being effectively controlled at the moult following treatment. The significance of these observations in relation to the crop protection activity of acylureas against field populations of Spodoptera larvae is discussed.  相似文献   

The dissipation of 1,3-dichloropropene in ditch bottom sediment and associated aerobic ditch water     

Denis A. Yon  Grant A. Morrison  Alec S. McGibbon 《Pest management science》1991,32(2):147-159

The aerobic aquatic metabolism of [¹⁴C]1,3-dichloropropene has been studied in two ditch waters and their associated sediments using a modification of the requirements of Section G.2. of the Dutch Registration Guidelines. Preliminary experiments showed that (a) the evaporation of 1,3-dichloropropene from water had a half-life of less than 5 h, and (b) in a soil/water slurry, 1,3-dichloropropene was rapidly converted to 3-chloropropenoic acid. In the definitive experiment conducted in two sediments, the overall recovery of radioactivity was good (84·5%) given the volatile nature of the chemical. In both sediment types, 1,3-dichloropropene evaporated rapidly from water. In the Letcombe samples (organic silty clay loam) more radioactivity was associated with the sediment (40%) than ditch water (5%) than in Marcham samples (medium clay, 12% in sediment and 10% in water) and this may reflect the organic matter content of the two sediments (10·5% and 2·9% respectively). The 1,3-dichloropropene in the ditch water was rapidly converted to 3-chloropropenoic acid and other minor polar products. The material in the soil was not investigated further.  相似文献   

Cross-resistance between acylurea insect growth regulators in a strain of Plutella xylostella L. (Lepidoptera: Yponomeutidae) from Malaysia     

Fauziah Ismail  Denis J. Wright 《Pest management science》1991,33(3):359-370

The activities of the acylurea insect growth regulators, chlorfluazuron, teflubenzuron and difubenzuron, and the neurotoxic macrocyclic lactone, abamectin were assessed against a laboratory susceptible (FS) strain and a field (Cameron Highlands, Malaysia (CH)) strain of the diamondback moth, Plutella xylostella L. using a leaf-dip bioassay at 20°C. The time taken to achieve end-point mortality was found to vary considerably (9–17 days), being fastest with abamectin against the FS strain and slowest with difubenzuron against the CH strain. The order of activity (LC₅₀ at F6/7) against second-instar larvae of both strains was: abamectin > chlorfluazuron = teflubenzuron ? difubenzuron. Subsequent assays (F14) with the acylureas, flufenoxuron and hexaflumuron against the FS strain suggested that the former was slightly more active than chlorfluazuron or teflubenzuron, the latter slightly less active. The CH population was found to be 12.6-, 6.7-, 6.4- and 2.3-fold less sensitive to difubenzuron, teflubenzuron, chlorfluazuron and abamectin respectively than the FS strain. Selection of sub-populations of the CH strain with chlorfluazuron (CHL-SEL) and teflubenzuron (TEF-SEL) for six generations (F6-11), resulted in LC₅₀ resistance ratios of 109- and 315-fold respectively when compared with the FS strain, equivalent to an 18- and a 46-fold increase in resistance compared with the unselected CH strain. Marked cross-resistance was also demonstrated between chlorfluazuron and teflubenzuron in both sub-populations. However, there was no evidence of cross-resistance to dijlubenzuron and abamectin and little or no cross-resistance to flufenoxuron and hexaflumuron. Resistance to chlorfluazuron and teflubenzuron appeared to be relatively unstable in the TEF-SEL compared with the CHL-SEL sub-population (over 6–9 generations). However, reselection of the TEF-SEL population with chlorfluazuron (F18–20) led to a very rapid increase in resistance to chlorfluazuron and particularly teflubenzuron. For the latter compound, resistance factors of about 1000000 were obtained (F19, 21). Such values are probably only semi-quantitative, as above a certain level of resistance feeding bioassays with acylureas (compounds which are active to a significant extent by ingestion) are likely to become rate-limiting.  相似文献   

Factors influencing the reproduction and production performance of the Nguni cattle ecotypes in South Africa     

Sónia Maria Ataíde Maciel  Michael Denis Fair  Michiel Matthys Scholtz  Frederick Wilhelm Cornelius Neser 《Tropical animal health and production》2016,48(1):75-85

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Variability of stem and branch maintenance respiration in a Pinus pinaster tree     

Bosc A  de Grandcourt A  Loustau D 《Tree physiology》2003,23(4):227-236

The relationship between maintenance respiration (Rm) of woody organs and their structural characteristics was explored in adult Pinus pinaster Ait. trees. We measured Rm on 75 stem and branch segments of different ages (from 3 to 24 years) and diameters (from 1 to 35 cm). The temperature response of Rm was derived from field measurements based on a classical exponential function with Q10 = 2.13. Relationships between Rm and the dimensions of the woody organs were analyzed under controlled conditions in the laboratory. The surface area of a woody organ was a better predictor of Rm than volume, but surface area failed to account for the observed within-tree variability of Rm among stems, branches and twigs. Two simple models were proposed to predict the variability of Rm at 15 degrees C in an adult tree. Model 1, a linear function model based on the dry mass and nitrogen concentration of sapwood and phloem tissues, explained most of the variability of Rm in branches and stems (R2 = 0.97). We concluded that the respective contributions of the phloem and sapwood depend on the location and diameter of the woody organ. Model 2, a power-law function model based on the length, diameter and age of the sample, explained the same variance of Rm as Model 1 and is appropriate for scaling Rm to the stand level. Models 1 and 2 appear to explain a larger variability of Rm than models based on stem area or sapwood mass.  相似文献   

Radial profiles of sap flow with increasing tree size in maritime pine     

Delzon S  Sartore M  Granier A  Loustau D 《Tree physiology》2004,24(11):1285-1293

We investigated the radial variation of sap flow within sapwood below the live crown in relation to tree size in 10-, 32-, 54- and 91-year-old maritime pine stands (Pinus pinaster Ait.). Radial variations were determined with two thermal dissipation sensors; one measured sap flux in the outer 20 mm of the xylem (Jref), whereas the other was moved radially across the sapwood in 20-mm increments to measure sap flux at multiple depths (Jref). For all tree sizes, sap flow ratios (Ri = JiJref (-1)) declined with increasing sapwood depth, but the decrease was steeper in trees with large diameters. Correction factors (C) were calculated to extrapolate Jref for an estimate of whole-tree sap flux. A negative linear relationship was established between stem diameter and C, the latter ranging from 0.6 to 1.0. We found that neglecting these radial corrections in 10-, 32-, 54- and 91-year-old trees would lead to overestimation of stand transpiration by 4, 14, 26 and 47%, respectively. Therefore, it is necessary to account for the differential radial profiles of sap flow in relation to tree size when comparing tree transpiration and hydraulic properties among trees differing in size.  相似文献   

Genetic differences for nitrogen uptake and nitrogen utilisation efficiencies in winter wheat     

Jacques Le Gouis  Denis B  ghin  Emmanuel Heumez  Pierre Pluchard 《European Journal of Agronomy》2000,12(3-4):163-173

Due to economic and ecological factors, European agricultural practices are likely to go towards extensive systems with lower inputs of nitrogen (N) fertilisers. The objective of this study was to assess varietal differences for N use at two nitrogen levels. A set of 20 winter wheat (Triticum aestivum L.) genotypes was studied over 2 years in northern France on a deep loam soil without (N0) and with 170 kg ha⁻¹ N fertiliser (N+) as ammonium nitrate. Results were consistent on both years as the genotype×year or genotype×year×N level interactions were not significant. The genotype×N level interaction was highly significant except for total N utilisation efficiency (total above-ground dry weight/total above-ground N) and grain N concentration. The genotype×N level interaction for grain yield was mainly due to three contrasting genotypes: Cappelle, a cultivar from the 1940s, had the same yield at N0 and N+; Arche had a high yield at both N levels; and Récital had a high yield with added N and a very low one without N. The number of kernels/ear explained most of the variations of grain yield at N0 (48%) and N+ (80%), and of the interaction (67%). N uptake efficiency (total above-ground N/soil N supply) accounted for 64% of the variation in N use efficiency (grain yield/soil N supply), while at N0 and at N+ it accounted for only 30%. N utilisation efficiency (grain yield/total above-ground N) was then more important at N+ than at N0. Grain N explained most of total plant N variation at both N levels. The interaction for N use efficiency was best explained by the interaction of N uptake (63%). The applications of these results to a breeding programme to create varieties adapted to low-input management systems are discussed.  相似文献   

HlMyb3, a putative regulatory factor in hop (Humulus lupulus L.), shows diverse biological effects in heterologous transgenotes     

Matousek J  Kocábek T  Patzak J  Skopek J  Maloukh L  Heyerick A  Fussy Z  Roldán-Ruiz I  Keukeleire DD 《Journal of agricultural and food chemistry》2007,55(19):7767-7776

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Ovicidal and larvicidal effectiveness of insecticides applied by dipping apples on the small fruit tortrix Grapholita lobarzewskii     

Charmillot PJ  Pasquier D  Salamin C  Ter-Hovannesyan A 《Pest management science》2007,63(7):677-681

The larvicidal and ovicidal effectiveness of twelve insecticides on Grapholita lobarzewskii Nowicki was tested by dipping apples in different concentrations of the insecticides. Emamectin was the most effective larvicidal product, with an LC(50) of 0.01 mg kg(-1), closely followed by spinosad, methoxyfenozide and chlorpyrifos-methyl, with LC(50) values between 0.2 and 0.7 mg kg(-1). Products like imidacloprid, indoxacarb, phosmet and thiacloprid gave LC(50) values between 1 and 2 mg kg(-1). Lastly, chlorpyrifos-ethyl and phosalone had LC(50) values of around 4 mg kg(-1), whereas tebufenozide and diflubenzuron had almost no larvicidal effect. Most of the products tested had low ovicidal effectiveness, and only fenoxycarb and emamectin gave LC(50) values worthy of note, close to 2 mg kg(-1).  相似文献