A Comparison of the Efficacy of Nuclear Polyhedrosis and Granulosis Viruses in Spray and Bait Formulations for the Control of Agrotis segetum (Lepidoptera: Noctuidae) in Maize

Agrotis segetum nuclear polyhedrosis virus (AsNPV) and granulosis virus (AsGV), propagated in laboratory cultures of A. segetum in England and A. ipsilon in Spain, respectively, were applied to plots of maize plants at the one‐ to four‐leaf stage of growth. Plots were arranged in a 6 x 6 Latin square design and infested with second‐instar A. segetum larvae (the common cutworm). Each virus was applied in separate treatments by two application methods; as an aqueous spray containing 0.1% Agral as a wetting agent, and as a bran bait. The NPV was applied at a rate of 4 X 10¹² polyhedra/ha, and the GV at 4 X 10¹³ granules/ha. Soil and plants were sampled for larvae on three occasions following virus treatment: 24 h, 4 days and 11 days. The larvae were reared on diet in the laboratory, until death or pupation, to examine the rate and level of viral infection. Infection data showed 87.5% and 91% NPV infection and 12.5% and 55% GV infection in spray and bait treatments, respectively, in larvae sampled 24 h after treatment. In larvae sampled 4 days after treatment, the results were 78% and 100% NPV infection, and 13% and 6% GV infection. A total of only six larvae were retrieved on day 11. In both treatments larvae infected with AsNPV died significantly more rapidly and at an earlier instar than those infected with AsGV, indicating that AsNPV appears to have better potential as a control agent for A. segetum.     

植物附生微生物与叶部病害生物防治研究进展

人们早已发现绿色植物叶面(phylloplane)栖居有大量微生物。在一百多年前微生物学家就从植物叶面分离到许多真菌和细菌。1910年Potter首先证实,叶面附生微生物在干扰真菌引起的叶部病害中起着重要作用。至本世纪上半叶,叶面微生物仍为人们所忽视。相反,在这期间土壤微生物得到很大发展,在土传植物病原菌生物防治研究方法上取得了很大进展,为后来的植物叶部病害生物防     

利用普通怯寄蝇防治菜粉蝶初探

1 前言 从外地引进寄蝇或人工助长当地寄蝇种类防治农林害虫,是有效的生防手段之一,国外已有很多成功的报道。King等(1981)在路易斯安娜州蔗田中人工大量释放螟利索寄蝇(Lixophaga diatraeae)成虫防治第1代小蔗杆草螟(Diatraea saccharalis),不同地区的寄生率分别达到4.1、8.7和35.7％;由于降低了农药的使用量,奇痣窄径茧蜂(Agathis stigmatera)的自然寄生率也相应提高,很好地控制了蔗田害虫的发生。在寄蝇的田间释放技术方面,国外还没有详细的报道。在我国,利用寄蝇防治害虫的工作也是刚刚起步,很多具体问题有待于进一步研究。     

Kairomones ofheliothis armigera andcorcyra cephalonica and their influence on the parasitic potential oftrichogramma chilonis (Trichogrammatidae: hymenoptera)

Kairomones from moth scales tend to influence the parasitic potential byTrichogramma chilonis Ishii. Hexatriacontane, pentacosane, heptadecane, docosane and 2, 6, l0-dodecatrienal-3, 7, 11-trimethyl were identified from the active moth scale extract ofHeliothis armigera Hubner (its natural host) andCorcyra cephalonica Stainton (a laboratory host). The significance of an array of compounds from moth scales with kairomonal activity for manipulating entomophagous insects in biological control programmes is discussed.     

DDT resistance in Anopheles gambiae declines with mosquito age

Adult Anopheles gambiae Giles mosquitoes from Zanzibar were tested on a standard discriminating dose of DDT which reliably kills susceptible mosquitoes. Adults from wild-caught larvae reared in the laboratory, and from the F1 progeny of wild-caught adults, showed less than 5% test mortality when newly-emerged, but mortality rose with age to over 90% when they were 12-14 days old. Wild-caught mixed-age adults showed an intermediate mortality rate of 25%, close to the rate predicted from laboratory results for a fully resistant population with an age-structure typical of this species in natural conditions. It is inferred that older, genetically resistant insects may be scored as susceptible, so that routine susceptibility tests with wild-caught adults underestimate the frequency of resistance. In Zanzibar, such tests probably helped to persuade spraying authorities to continue spraying DDT in spite of resistance. Resistance which is restricted to younger insects may nonetheless reduce the effectiveness of spraying.     

In vitro antagonism of bioluminescent fungi by Trichoderma harzianum

Two species of bioluminescent fungi, Panellus stypticus and Omphalotus olearius were placed in contact with three different strains of interfungal pathogenic Trichoderma harzianum. Subsequent light emission by the luminous fungi and advance of the interfungal pathogens were compared. Relative differences among the pathogens were reflected in their rate of mycelial advance, the total area over which they produced spores upon the host fungi, and decreases in host bioluminescence. After ten days differences in the total surface areas of spore production varied from 1 to 53 per cent. Differences in the reduction of bioluminescence of the same material ranged over 2 orders of magnitude. Final reduction in luminescence ranged over 6 orders of magnitude. A marked reduction in bioluminescence was observed to precede the advance of spore production. The greatest reduction in luminescence was correlated with the presence of T. harzianum hyphae. Two strains of T. harzianum, NRRL 1698 and ATCC 58674, were effective against both bioluminescent fungi within the study period while a third strain, NRRL 13019, was only effective against Omphalotus olearius.     

Distribution of salmon gonadotrophin releasing-hormone in the brain and pituitary of the sea bass (Dicentrarchus labrax)

Summary The distribution of salmon gonadotrophin-releasing hormone (sGnRH) was studied in the brain and pituitary of two-year-old immature sea bass (Dicentrarchus labrax) by means of an enzymoimmunoassay (EIA) for sGnRH and immunocytochemistry. The EIA for sGnRH is a competitive assay using a tracer made of sGnRH coupled to acetylcholinesterase from an electric eel. The separation of free and bound tracer is achieved by coating the plates with mouse anti-rabbit IgG monoclonal antibodies. Displacement curves generated by sGnRH and extracts from pituitary and different brain regions showed a good parallelism allowing the assay to be used for sGnRH measurements in this species. Although all parts of the brain contained measurable levels of sGnRH, the highest concentrations were found in the pituitary, the olfactory bulbs and the telencephalon. These data were confirmed by immunocytochemistry. Cell bodies were found in the olfactory bulbs, ventral telencephalon, preoptic region and mediobasal hypothalamus. Immunoreactive fibers could be observed in all parts of the brain including the optic tectum, the cerebellum (corpus and valvula), the vagal lobe, the medulla oblongata and the rostral spinal cord. In most cases, these fibers do not form well defined bundles; however, there was clearly a continuum of immunoreactive fibers, extending from the olfactory bulbs to the pituitary, and along which all the cell bodies described above were located. In the ventral telencephalon and the preoptic region, clear pictures of varicose positive fibers contacting immunoreactive perikarya could be observed. These data indicate that sGnRH is most likely an endogenous peptide in the brain of the sea bass, although the presence of other forms of GnRH cannot be excluded at this point. This study also demonstrates that the general organization of the GnRH systems in the sea bass is highly similar to what has been described in most freshwater teleost species, and provides basis for further studies on the neuroendocrine control of gonadotrophin release in this commercially important species.     

Evidence for the involvement of a SchistoFLRF-amide-like peptide in the neural control of locust oviduct

Summary The presence of a SchistoFLRFamide-like peptide associated with the oviducts of Locusta migratoria has been shown using sequential reversed-phase high performance liquid chromatography separation coupled with radioimmunoassay and bioassay. The peptide is present in areas of the oviduct which receive extensive innervation, with sixfold less peptide in areas that receive little innervation. Material with FMRFamide-like immunoreactivity (determined by radioimmunoassay) is also present in the oviducal nerve and VIIth abdominal ganglion.SchistoFLRFamide is a potent modulator of contraction of this visceral muscle, inhibiting or reducing the amplitude and frequency of spontaneous contractions, relaxing basal tonus, and reducing the amplitude of neurally-evoked, proctolin-induced, glutamate-induced and high potassium-induced contractions. The FMRFamide-like immunoreactivity within the oviducts which co-elutes with SchistoFLRFamide on two separations is also capable of reducing the amplitude of neurally-evoked and proctolin-induced contractions, and of inhibiting spontaneous contractions and relaxing basal tonus.The effects of SchistoFLRFamide upon this visceral muscle are not abolished by the -adrenergic receptor antagonist phentolamine and do not appear to be mediated by cyclic AMP. Thus the receptors for Schisto-FLRFamide are distinct from those of octopamine which mediate similar physiological effects but which are blocked by phentolamine and which are coupled to adenylate cyclase.The results indicate that SchistoFLRFamide, or a very similar peptide, which has previously been identified as a modulator of locust heart beat, is also associated with visceral muscle of the reproductive system, and may play a neural role in concert with octopamine, at modulating muscular activity.Abbreviations BPP Bovine pancreatic polypeptide - BSA Bovine serum albumin - EJP Excitatory junctional potential - FaRPs FMRFamide-related peptides - FLI FMRFamide-like immuno-reactivity - LMS Leucomyosuppressin - RIA Radioimmunoassay - RP-HPLC Reversed-phase high performance liquid chromatography - TFA Trifluoroacetic acid     

The course control system of beetles walking in an air-current field

The wind-orientated walk of carrion beetles Necrophorus humator F. was analysed under closed-loop conditions with a walking compensator and under openloop conditions with a paired tread wheel (Fig. 1).

Waterstriders (Gerris paludum F.) compensate for drift with a discontinuously working visual position servo

Waterstriders on ponds and creeks compensate for displacement caused by wind or water current with periodical jumps against the direction of drift. This behavior is mediated by visual stimuli.