氟虫腈对斑马鱼和小菜蛾毒性的手性选择性研究

手性农药分子的不同对映体在环境中的降解速率和对于生物的毒性可能存在很大的差异,因此拆分并使用对靶标生物毒性较高或对非靶标生物毒性较低的单一或浓缩的对映体配方可以有效地降低杀虫剂的环境风险.本文用手性柱拆分了一种广泛使用的手性农药,氟虫腈的两种对映体,研究了这两种对映体和消旋体对靶标生物小菜蛾和非靶标生物斑马鱼的急性毒性.结果表明氟虫腈对受试靶标和非靶标生物的毒性均无手性选择性,说明无法通过对氟虫腈进行手性拆分并使用单一对映体配方来降低氟虫腈的环境风险.这一结论间接支持了农业部新近出台的禁止氟虫腈用于防治农田害虫的政策.     

Made in conflict. Local residents' construction of a local environmental problem

The aim of this paper is to understand how local residents participate in the construction of local environmental problems and to evaluate a particular analytical approach in environmental sociology to study this phenomenon. The paper is based on an interview study with a sample of local residents. The analysis demonstrates how the local residents attempt to construct a local environmental problem. In particular, the study focuses on how involved actors are positioned, how different sorts of knowledge claims are used, and how the neglect the residents perceive from the authorities affects the attempt to construct a local environmental problem. The study shows that the local residents play a central role in the construction of the situation and that the evaluated model could be very helpful as an analytical tool in the investigation of local residents' participation in the construction of environmental problems.     

Assessing the impact of biological control of Plutella xylostella through the application of Lotka–Volterra model

The Lotka–Volterra model was applied to the population densities of diamondback moth (DBM), Plutella xylostella (L.) and its exotic larval parasitoid Diadegma semiclausum (Hellen) data that was collected earlier by icipe's DBM biological control team. The collections were done for 15 months before the release and 36 months after release of the parasitoid in two areas; in Werugha, Coast Province of Kenya and Tharuni, Central Province of Kenya, respectively. For each area in pre- and post-release periods, we estimated Lotka–Volterra model parameters from the minimization of the loss function between the theoretical and experimental time-series datasets following the Nelder-Mead multidimensional method. The model estimated a reduction in the value of the steady state of DBM population from 4.86 to 2.17 in Werugha and from 6.11 to 3.76 and 3.45 (with and without exclusion of the time before D. semiclausum recovery) in Tharuni when transiting from the pre- and post-release periods, respectively. This change was a consequence of the newly introduced parasitoid, in the areas. The study presented a successful and detailed technique for non-linear model parameters restoration which was demonstrated by the correct mimicking of empirical datasets from the classical biological control with D. semiclausum, in different areas of Kenya. The applied model has measured the parasitoids impact on the DBM biological control through a quantitative estimate of the effectiveness of the newly introduced species D. semiclausum. These equations may therefore be used as tool for decision making in the implementation for such pests’ management system strategy.     

Evaluation of discrete host–parasitoid models for diamondback moth and Diadegma semiclausum field time population density series

The performance of discrete mathematical models to describe the population dynamics of diamondback moth (DBM) (Plutella xylostella L.) and its parasitoid Diadegma semiclausum was investigated. The parameter values for several well-known models (Nicholson–Bailey, Hassell and Varley, Beddington, Free and Lawton, May, Holling type 2, 3 and Getz and Mills functional responses) were estimated. The models were tested on 20 consecutive sets of time series data collected at 14 days interval for pest and parasitoid populations obtained from a highland cabbage growing area in eastern Kenya. Model parameters were estimated from minimized squared difference between the numerical solution of the model equations and the empirical data using Powell's method. Maximum calculated DBM growth rates varied between 0.02 and 0.07. The carrying capacity determined at 16.5 DBM/plant by the Beddington et al. model was within the range of field data. However, all the estimated parameter values relating to the parasitoid, including the instantaneous searching rate (0.07–0.28), per capita searching efficiency (0.20–0.27), search time (5.20–5.33), handling time (0.77–0.90), and parasitism aggregation index (0.33), were well outside the range encountered empirically. All models evaluated for DBM under Durbin–Watson criteria, except the May model, were not autocorrelated with respect to residuals. In contrast, the criteria applied to the parasitoid residuals showed strong autocorrelations. Thus, these models failed to estimate parasitoid dynamics. We conclude that the interactions of the DBM with its parasitoid cannot be explained by any of the models tested. Two factors may be associated with this failure. First, the parasitoid in this integrated biological control system may not be playing a major role in regulating DBM population. Second, and perhaps more likely, poor correlations reflect gross inadequacies in the theoretical assumptions that underlie the existing models.     

Environmental management of oak wilt disease in central texas

Oak wilt disease, for which there is no known cure, is one of the most destructive tree killers in the United States today. This analysis reports on the patterns of disease transmission, along with the methods of treatment used to suppress the severity of the pathogen's attack on trees in central Texas. The practical problems inherent in the linkage between people and their relationship with this environmental disorder are addressed. The environmental controls implemented have application to other areas of the United States and western Europe, where tree species are subject to infections.     

Vibrational signals in a gregarious sawfly larva (<Emphasis Type="Italic">Perga affinis</Emphasis>): group coordination or competitive signaling?

Group living confers both benefits and costs to the individuals involved. Benefits may include enhanced defense, thermoregulation, and increased foraging efficiency while costs often involve competition for resources such as food, shelter, and mates. Communication provides a medium of exchange among individuals engaged in either cooperative or competitive interactions. The functional analysis of signals within groups therefore requires testing both cooperative and competitive functions, although the latter is infrequently done. In this paper, I study the use of two vibrational signals in a gregarious, processionary Australian sawfly larva, Perga affinis: tapping and contractions. Tapping involves striking the substrate with the sclerotized portion of the abdominal tail and a contraction is a fast, whole-body twitch, which is both tactile and vibrational in its transmission. For tapping, I first demonstrate that it is a form of communication, as tapping of one larva elicits tapping in another, and that it is transmitted through substrate vibrations. I then test whether the signal is mostly cooperative or competitive in nature by examining it in light of two hypotheses: (1) the Group Coordination hypothesis, stating that the signal functions to maintain group cohesiveness and (2) the Competitive Signaling hypothesis, stating that tapping serves as a competitive assessment signal between larvae while feeding. For contractions, I test only the group coordination hypothesis that they serve to coordinate and initiate group movement. Results support the group coordination hypothesis for each signal. While feeding, lone larvae (without potential competitors) were significantly more likely to tap than those in groups, and this trend continued in non-feeding situations. Contractions regularly preceded periods of group movement during processions and were given with increasing frequency before departure from preforaging clusters. The vibrational signals in this processionary species likely function cooperatively to maintain group cohesiveness and coordinate movement.     

Summary of efficacy evaluations using aerially applied Gypchek® against gypsy moth in the U.S.A.

Abstract

Gypchek^®, the gypsy moth (Lymantria dispar L.) nucleopolyhedrosis virus product, is manufactured by the United States Department of Agriculture (USDA) Forest Service, and Animal and Plant Health Inspection Service under controlled conditions in a laboratory strain of gypsy moth larvae. Gypchek was registered with the U.S. Environmental Protection Agency in 1978 as a general use pesticide to control gypsy moth. This product has been the subject of intense research and development targeted toward maximizing efficacy while minimizing the cost of production and application. The current Gypchek tank mix is applied at 1.25 × 10¹²occlusion bodies (OB's) per hectare for each of two applications (3‐days apart) at 18.7 litres/ha per application.     

Appropriateness of needles of different conifer species for the feeding and growth of larvae from two populations of the Siberian moth

A comparison of two Siberian moth populations from the Altai Republic (feeding on Siberian fir) and the Tyva Republic (feeding on Siberian larch) has revealed no differences between them with respect to ecophysiological parameters of larval growth and feeding on needles of the same conifer species under laboratory conditions. The index of appropriateness of food plants for the larvae from both populations decreases in the series larch > fir > spruce > pine. The age-related dynamics of parameters characterizing the feeding and growth of larvae are independent of the population to which the insects belong.     

Pharmacological analysis of feeding in a caterpillar: different transduction pathways for umami and saccharin?

Neonate larvae of codling moth, Cydia pomonella (L.), modify their behavior in the presence of saccharin, monosodium glutamate (MSG), or L(+)-2-amino-4-phosphonobutyric acid (L-AP4) by commencing their feeding earlier. Previously published pharmacological analysis demonstrated that phagostimulatory effects of MSG and L-AP4 (which elicit umami taste sensation in humans) are reversed by adenylate cyclase activator and phosphodiesterase inhibitor. In this study, by measuring the time needed to start ingestion of foliage treated with mixtures of phagostimulants and signal transduction modulators, we show that phagostimulatory effects of l-aspartate (the third hallmark umami substance) are also abolished by both adenylate cyclase activator and phosphodiesterase inhibitor, but not by phospholipase C inhibitor. However, stimulatory effects of hemicalcium saccharin were affected only by phospholipase C inhibitor. The results suggest that codling moth neonates use different transduction pathways for perception of hemicalcium saccharin and umami.     

Pollinator insects benefit from rotational fallows

The importance of rotational fallows for pollinating insects in intensively cultivated farmland was studied in a three-year field experiment. The focus was on the establishment method (undersowing or seed mixture sown post-tillage), seed mixture (competitive Festuca pratensis-Phleum pratense-Trifolium pratense or less competitive Agrostis capillaris-Festuca ovina mixture) and duration (1 or 2 years) of the fallow. The seed mixture and duration affected the pollinators more than the method of establishment. Pollinator species richness was higher in fallows sown with less competitive than with competitive grasses and it increased in the second year. Stubble fields reached as high pollinator species richness already during the first year as fallows with less competitive grasses did in the second year. Pollinator abundance was highest in those treatments in which species richness of flowering plants was highest. The results suggest that the benefits of rotational fallows for pollinators increase when they are established as stubble or using seeds of less competitive grasses and when the field is fallowed for (at least) two summers.