摘要:

Experiments showed that a stem midge collected locally on couch grass (Agropyron repens) and similar midges collected on wheat, barley and rye were of the same species, i. e. the hessian fly,Mayetiola destructorSay. There were three main flights per year, with some overlapping of the generations. In experiments,Aegilops ovata, Triticum compactum, T. dicoccoides, T. durum, T. speltaandT. turgidumwere successfully used as host plants besides wheat, barley, rye and couch grass. Individual female midges when moved from plant to plant gave rise to families on the different host plants; similarly, succeeding generations of midges were able to breed on various host plants other than those from which they themselves were reared. Oviposition also took place on plants on which larvae failed to establish themselves.Wheat seemed more favourable for the hessian fly than couch grass, and more midges were reared from young plants than from mature ones.Unisexual families occurred in about half the experiments. The following parasites were bred:Trichacis didasWalker,Eupteromalus? hemipterusWalker,Platygastersp.,Chrysocharissp. andTetrastichussp.

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1957.tb00448.x

出版商:Blackwell Publishing Ltd    

年代:1957

数据来源: WILEY

摘要:

Different traps were compared to find the type most suitable for studying aphid vectors of plant viruses quantitatively.A Moericke water trap caught more aphids than a flat sticky trap of equal area. A flat sticky trap (930 sq. cm.) caught half as many aphids as a cylindrical trap (945 sq. cm.), which caught about one‐third as many as a water trap (1200 sq. cm.) or a Johnson suction trap (9 in. fan) when operated at between 2 and 3 ft. over bare soil.Yellow traps caught proportionally moreTuberculoides annulatus, and in summer moreCapitophorusspecies than a suction trap, but significantly fewerAnoecia corni, Sitobiumspp. andPemphigus bursarius.Traps with a level surface caught proportionally moreBrevicoryne brassicae, Aphis fabaeandMyzus persicae, but fewerAnoecia corniandDrepanosiphum plantanoidesthan vertical cylindical traps. Attraction by colour influences the catch on horizontal traps more than on cylindrical traps because there is less impaction by the wind.Only suction traps indicate the number of aphids per unit volume of air and are non‐selective, but they are expensive and require an electric power supply. Water traps effectively catch those aphids that are attracted to yellow, but they require frequent attention. Sticky traps catch fewer aphids than either suction or water traps, but they can be left unattended for about 2 weeks. Flat sticky traps catch aphids likely to land on a crop, and cylindrical traps show when aphids are in the air, but not if those aphids are able or wanting to land. For routine work cylindrical sticky traps have other advantages; they are cheap and do not require skilled handling, and their catches of alateMyzus persicaehave been correlated with the spread of some plant viru

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1957.tb00449.x

出版商:Blackwell Publishing Ltd    

年代:1957

数据来源: WILEY

摘要:

A study has been made of the antagonistic effects of a range of phenoxy and other acids on the growth‐promoting activity of a number of auxins as assessed by theAvenacylinder and pea curvature tests. The compounds examined as inhibitors were selected on a logical basis, these molecules not possessing the structural requirements considered necessary for growth‐regulating activity, yet possessing groupings which might allow them to accumulate at a site of action from which the growth response by auxins might be initiated. Our previous demonstrations that inactive stereoisomers of x‐aryloxy propionic acids can competitively inhibit the activity of their active enantiomorph has been confirmed and a similar antagonism has been found to operate with other inactive aryloxy acids. Such competitive antagonism is discussed in relation to a ‘three‐point’ contact theory on mod

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1957.tb00450.x

出版商:Blackwell Publishing Ltd    

年代:1957

数据来源: WILEY

摘要:

A wide range of aryloxyacetic acids and corresponding acids with alkyl groups in the side chain, their arylthio‐ analogues and the antibiotic griseofulvin have been assessed in the plate test for fungistatic effect on six fungi, and as systemic fungicides againstBotrytis fabaein broad beans andAlternaria solaniin tomatoes. The results indicate that in general, arylthio‐ derivatives are more fungicidal than their aryloxy‐ analogues. The systemic fungicidal performance of x‐(2‐chlorophenylthio)propionic acid in the tomato test at 1–100 p. p. m. was found to be of the same order as that shown by griseofulvin at 50–500 p. p. m. Variable results were obtained with griseofulvin in the tornato test and its performance in the bean test was consistently poor. Further evidence is presented which indicates that the protection conferred by certain compounds may not be due to a

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1957.tb00451.x

出版商:Blackwell Publishing Ltd    

年代:1957

数据来源: WILEY

摘要:

The relative importance of dissolved oxygen and dissolved carbon dioxide in determining the lethal effect of an environment for rainbow trout and perch has been investigated with an apparatus which controls the concentrations of these gases in a body of water. It is shown that concentrations of carbon dioxide which sometimes occur in polluted streams can more than double the minimum concentration of dissolved oxygen necessary for the survival of half a population of rainbow trout fingerlings for 24 hr. Increase in temperature between 12·5 and 19·5°C. shortens period of survival in solutions containing up to 67 p. p. m. CO2. Within the range of dissolved oxygen concentration which is lethal in the presence of 59 p. p. m. CO2or more, perch are more resistant than rainbow trout in the lower, but less resistant in the higher, oxygen concentrations. The relation between carbon dioxide concentration and the oxygen tension at which rainbow trout blood is half saturated with oxygen is similar to the relation between carbon dioxide concentration and the oxygen tension at which the median period of survival of this species is I

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1957.tb00452.x

出版商:Blackwell Publishing Ltd    

年代:1957

数据来源: WILEY

摘要:

Two aqueous suspensions, one containing crystals of uniform size and the other containing colloidal particles, were made with each of seven solid contact poisons (two DDT‐analogues, DDT, rotenone, 2‐bromomercurithiophen, dieldrin and endrin). The relative toxicity of each pair of suspensions was found in dipping or measured‐drop tests on as many as possible of the speciesOryzaephilus surinamensisL.,Tribolium castaneumHerbst andTenebrio molitorL. In addition, some tests were made by injection of colloidal suspensions.In each test, insects were kept after treatment at two temperatures: 28°C. and 11, 17 or 20°C.; counts of kill were made after 24 hr. The tests measured three different kinds of temperature coefficient of insecticidal action.In the contact tests, the colloid was nearly always more toxic than the crystals. In all the tests, except those with dieldrin, the relative toxicity (colloid: crystals) was greater at the lower after‐treatment temperature, i. e. the temperature coeficient of the relative toxicity was negative. But in the case of dieldrin, the coefficient was positive.The DDT‐analogues, DDT, rotenone and endrin were more toxic at the lower after‐treatment temperature, i. e. they had negativetemperature coefficients of kill by contact action.In all these cases the temperature coefficient of kill by contact action was greater for colloid than for crystals. Dieldrin and 2‐bromomercurithiophen had positive temperature coefficients of kill by contact action. With dieldrin, the temperature coefficient was greater for colloid than for crystals; but with 2‐bromomercurithiophen, the reverse was true.Thetemperature coefficient of kill by injectionwas negative for DDT, but positive for dieldrin and endrin; the other poisons were not tested by injection.A possible explanation for the results of the contact tests is given in an Appendix. The explanation is based on a number of assumptions about the penetration of insect cuticle by solid poisons. These assumptions lead to the conclusion that the effect of temperature on the relative toxicity depends on the temperature coefficient of kill by internal action of the poison on the insect. This can be measured by injection tests. If it is negative or zero, the ratio of toxicities (colloid: crystals) by contact action, measured quite soon after treatment of the insects, will be greater at a low temperature after treatment than at a high temperature after treatment; but if the coefficient is positive, the effect of temperature on relative toxicity cannot be foretold. The experimental results seem to confir

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1957.tb00453.x

出版商:Blackwell Publishing Ltd    

年代:1957

数据来源: WILEY

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1957.tb00455.x

出版商:Blackwell Publishing Ltd    

年代:1957

数据来源: WILEY

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1957.tb00456.x

出版商:Blackwell Publishing Ltd    

年代:1957

数据来源: WILEY

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1957.tb00458.x

出版商:Blackwell Publishing Ltd    

年代:1957

数据来源: WILEY

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1957.tb00459.x

出版商:Blackwell Publishing Ltd    

年代:1957

数据来源: WILEY