摘要:

SUMMARYWhen sixth abdominal or metathoracic ganglia of the cockroachPeriplaneta americanaL. were irrigated continuously with diazoxon (O, O‐diethylO‐(2‐isopropyl‐6‐methyl‐4‐pyrimidinyl) phosphate) solutionin situ, the log. of the time required to block conduction in certain nerve pathways in the ganglia was directly proportional to the log. of the concentration of diazoxon applied. Inhibition of cholinesterase began peripherally before function was affected, and had begun to affect the neuropile by the time that conduction was first blocked. Longer exposure to diazoxon disrupted nerve function even more, especially in the sixth abdominal ganglion, and inhibited more cholinesterase, but much longer exposure was needed to inhibit nearly all the cholinesterase. Irrigation with saline, begun when block first occurred, failed to restore completely either nerve function or cholinesterase activity.The cholinesterase activity of ganglia from cockroaches treated topically with an LD90 of diazoxon and examined at intervals after treatment decreased steadily to a level similar to that of ganglia treated directly with diazoxon until conduction was just blocked, but rarely became less, even in moribund insects. Nerve function in metathoracic ganglia became badly affected and remained so in all cockroaches that failed to recover, but sixth abdominal ganglia, though usually badly affected for a time, always recovered normal function, even in prostrate cockroaches. The condition of a poisoned insect, therefore, corresponded much more closely to the functional condition of the metathoracic ganglion than to that of the sixth abdominal ganglion.Applying the insecticide close to a ganglion advanced the time of onset of symptoms but affected the final outcome very little.It was calculated that the highest concentration of diazoxon in the haemo‐lymph in contact with the nervous systems of cockroaches treated topically with LDgo's of diazoxon

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1966.tb04394.x

出版商:Blackwell Publishing Ltd    

年代:1966

数据来源: WILEY

摘要:

SUMMARYThe number of flying insects in the sheltered zone to leeward of artificial windbreaks of 0, 25, 45 and 70% permeability was greater than in unsheltered areas. Insects accumulated in the air nearer to dense windbreaks than to more permeable ones, and the position of maximum aerial density of insects coincided with that of maximum shelter. The more dense the windbreak the greater the numbers in the air to leeward. Absolute wind speed slightly affected the position of maximum aerial density behind a 45% permeable fence.

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1966.tb04395.x

出版商:Blackwell Publishing Ltd    

年代:1966

数据来源: WILEY

摘要:

SUMMARYFlying Cecidomyiidae, Mycetophilidae and Aphididae accumulated to leeward of a windbreak of 45 % open area. There were relatively more of these insects in sheltered than in unsheltered air the greater the angle of the incident wind to the windbreak, and the greater the free wind speed. Mycetophilidae and Aphididae accumulated relatively less as turbulence in the free air increased. The accumulation of Mymaridae to leeward of a solid windbreak was affected only by wind speed. No relationship was detected between the accumulation of Psychodidae, parasitic Hymenoptera, Thysanoptera and Staphylinidae and the incident angle of wind, wind speed or turbulence.

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1966.tb04396.x

出版商:Blackwell Publishing Ltd    

年代:1966

数据来源: WILEY

摘要:

SUMMARYIn a turnip crop natural infection with turnip mild yellows virus was greatest in two narrow zones, one to leeward of an artificial windbreak, the other in a long shallow depression in the earth. Both zones were approximately across wind whenMyzus persicaeflew in early summer. Later in the summer, similar windbreaks facing different prevailing winds increased the number of larvae ofScaptomyza apicalison the plants immediately to leeward and windward of the windbreaks, probably because shelter affected adults that were flying and laying eggs in the crop.

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1966.tb04397.x

出版商:Blackwell Publishing Ltd    

年代:1966

数据来源: WILEY

摘要:

SUMMARYTwo isolates of groundnut rosette virus from East Africa (GRVE1and GRVE2) and from West Africa (GRVW1and GRVW2) were transmitted byAphis craccivoraobtained from West Africa. A third isolate from West Africa (GRVW3) was not transmitted byA. craccivorafrom three widely separated sources. GRVW1, GRVW2and GRVW3caused leaf‐symptoms in groundnut of a mosaic pattern in light and dark green. GRVE1and GRVE2caused chlorosis or chlorosis and leaf distortion as well as mosaic symptoms. Groundnut plants with GRVW1could not be infected by means of aphids with GRVE1, and GRVE1gave similar protection against GRVW1, which suggests that they are strains of the same virus.All isolates were transmissible manually from groundnut to groundnut (Arachis hypogea), Trifolium incarnatumandT. repens, and caused systemic infection. InoculatedNicotiana clevelandiiandN. rusticadeveloped symptoms but virus could not be recovered from them.Chenopodium amaranticolor, C. hybridumandC. quinoashowed local lesions on inoculated leaves. Virus could be acquired by aphids from groundnut orTrifolium repensinfected by means of aphids, but not from those infected by manual inoculation. Virus could not be recovered fromT. incarnatummanually or by aphids, but was transmitted by cleft‐grafting from clover to groundnut.Saps extracted in borax buffer plus zinc sulphate at pH 9 from plants infected with GRVW1and GRVE1remained infective at 18° C. for 1 week, and at — 20° C. for up to 4 weeks. Virus could be recovered from frozen leaves. Buffered saps lost infectivity when heated above 50° C. for 10 min.; most were still infective when diluted 1/10 and some at 1/100.Electron micrographs of partially purified preparations contained spherical particles 25–28 mμ in diameter. There were usually only about five per microscope field and they resembled those of some ot

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1966.tb04398.x

出版商:Blackwell Publishing Ltd    

年代:1966

数据来源: WILEY

摘要:

SUMMARYA laboratory study was made of re‐invasion of soils fumigated in closed containers at rates of 3 ml./sq.ft. 10 in. deep with chloropicrin, methyl bromide and a 67:33 mixture of the two materials (MBC–33), using the dilution plate method of determination. Counts after aeration, 3 weeks later, showed that all three fumigants eliminated practically all fungi. Chloropicrin and MBC–33 also killed almost all bacteria and actinomycetes, whereas fumigation with methyl bromide markedly increased numbers of bacteria without materially altering numbers of actinomycetes.Subsequently, in soils fumigated with chloropicrin or MBC–33, fungi recolonized rapidly, but up to 93 % of the colonies isolated wereTrichoderma viride.Increase of fungi in soils fumigated with methyl bromide was slower andPenicilliumspp. predominated. Bacteria at first declined in numbers, then increased rapidly in soils fumigated with all three materials. In soils fumigated with methyl bromide, actinomycetes, usually considered to include good antagonists, increased but did not exploit their initial advantage over fungi. In soils fumigated with chloropicrin and MBC–33 actinomycetes did not recolonize in appreciable numbers.The greatest variety of fungous genera occurred in isolates from rhizo‐spheres of red beet, but the greatest numbers of colonies of both fungi and bacteria were isolated from rhizospheres of pea and pumpkin. None of the crops tested greatly stimulated recolonization by actinomycetes. Compared with the drastic changes brought about by fumigants the influence of seed and root exudates on either the magnitude or the composition of re‐invading micro‐organ

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1966.tb04399.x

出版商:Blackwell Publishing Ltd    

年代:1966

数据来源: WILEY

摘要:

SUMMARYGermination of conidia ofErysiphe cichoracearumand hyphal growth in 3 days at 23° C. and 6 mb. saturation deficit was similar, whether conidia were applied dry or suspended for up to 1 hr. in glass‐distilled water before being sprayed on tobacco leaves.Growth of single conidial colonies whose hyphae were more than 333 μ long, was positively correlated with numbers per cm.2of leaf (P<0.01) on three of the eleven times tested, mostly when conidia were sparsely distributed; ten of the regressions were positive.A greater percentage of conidia germinated at 0–1.7 mb. saturation deficit than at 7–9 mb. Subsequent growth of hyphae was greater in the dr

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1966.tb04400.x

出版商:Blackwell Publishing Ltd    

年代:1966

数据来源: WILEY

摘要:

SUMMARYThe anthracnoses of coffee known in East Africa as ‘brown blight’ are denned with respect to coffee berry disease, both caused by strains ofColletotrichum coffeanumNoack(Ghmerella cingulata(Stonem.) Spauld.&von Schrenk). Pathogenicity of brown blight strains to twigs, leaves, blossoms and berries is investigated and discussed with the conclusion that consistent differences in pathogenicity are absent. Latent infections on green berries were observed to become active upon ripening. The general role ofC. coffeanum(other than CBD strains) appears to be confined to colonization of necrotic and moribund tissue, with sporadic active parasitism under certain local conditions.Maximum apparent losses are blemishing of 4% of parchment coffee and possible total loss of 2 %, both avoidable by regular picking. Other possible losses are discus

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1966.tb04401.x

出版商:Blackwell Publishing Ltd    

年代:1966

数据来源: WILEY

摘要:

SUMMARYStem rot of cucumbers, caused byMycosphaerella melonis(Passer.) Chiu&Walk, was present in Butcher's Disease Resister in every glasshouse in the Lea Valley examined in 1963 and was sometimes noticed as early as April. No correlation was detected between the severity of the disease and the type of bed used (straw bale or traditional), type of training (arch or cordon), thermostat setting, ventilation practice, date of planting, or routine fungicidal spraying practice.The disease could be transmitted on a pruning knife to any node of the plant. Infection by air‐borne spores was induced experimentally. Leaves could not be infected artificially.The frequency of air‐borne ascospores of the fungus showed a conspicuous evening peak. Numbers of spores were highest in wet dull weather.Dithiocarbamates appear to be the most effective fungicides now available for cont

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1966.tb04402.x

出版商:Blackwell Publishing Ltd    

年代:1966

数据来源: WILEY

摘要:

SUMMARYLaboratory bioassays of fungicides againstItersonilia perplexansshowed that disease developed more readily on outer mature chrysanthemum petals than on immature inner florets and that inoculations on floret tips were more successful than on bases. In glasshouse trials, seven of the fungicides tested significantly decreased disease development without inducing phytotoxicity: of these, maneb and mancozeb, but not zineb, left unsightly deposits.Tank‐mixed zineb was more fungitoxic, especially in continuing high humidities, but was also more phytotoxic than wettable powder and dust formulations, but this phytotoxicity could be avoided by spraying the crop at the opening bud stage and by increasing the interval between applications from 5 to 7 day

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1966.tb04403.x

出版商:Blackwell Publishing Ltd    

年代:1966

数据来源: WILEY