摘要:

The investigations were carried out in nutrient solution with iron as ferric citrate and nitrogen in the form of nitrate.Addition of 2.5 p.p.m. vanadium to plants in which iron chlorosis was already‐established, either by a lack of iron or by excess manganese, failed to counteract the condition, and caused toxic symptoms.Reduction of the standard iron supply to ½ or ⅓ accentuated the toxicity of 2–5 or 5 p.p.m. V to soybean and flax, but a similar reduction in phosphorus had no influence. Toxicity to peas, however, was increased when the phosphorus was reduced to 1/10, provided the iron level was high (20 p.p.m. Fe).Raising the iron supply to 20 or 30 p.p.m. Fe counteracted the toxicity of manganese (10 p.p.m.), molybdenum (40 p.p.m.) and vanadium (2.5 p.p.m.), but the result was less marked when these three elements were combined. Iron supplied in successive, small doses proved less efficient in overcoming molybdenum or vanadium, but not manganese excess, than the same amount of iron supplied in fewer and larger quantities. Varying the iron supply had little effect when the concentration of the three elements was low. When increased iron supply had reduced the chlorosis caused by high manganese or vanadium, it also reduced the manganese and vanadium contents of the shoot (p.p.m./d.m.), but the molybdenum content was only lowered by high iron when given in non‐toxic concentration (0.1 p.p.m. Mo) combined with excess manganese.The iron content of the shoot (%/d.m.) was scarcely affected by the amount of iron supplied, but was generally reduced by high concentrations of manganese, molybdenum or vanadium.Results regarding the effect of vanadium on the phosphorus content of the shoot were conflicting, and differences occurred only when the iron supply was low. Here the phosphorus content of soybean and peas was generally reduced, while that of flax was increased.Yield data for soybean and flax indicated an interaction between manganese with both molybdenum and vanadium if the iron supply was low, but none between molybdenum and vanadium. The effect of all three metals was additive in respect

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1954.tb00913.x

出版商:Blackwell Publishing Ltd    

年代:1954

数据来源: WILEY

摘要:

The sudden‐death disease of the clove tree is invariably associated with the fungusValsa eugeniae.The pathogenicity of this fungus has been investigated experimentally, and it has been shown that it is a primary parasite on mature clove trees, that saplings are resistant to it, and that seedlings are immune. It has been experimentally demonstrated that water‐borne spores of the fungus can invade the absorbing and the fibrous roots of the clove tree. The slow‐decline disease, which affects clove saplings only, is associated with a slow and progressive root‐rot over a period of many years.Valsais also invariably associated with this disease, which occurs only in areas which have been replanted after the previous stand has been killed by sudden death. It is thought that slow decline is the symptom‐expression ofValsaattack on young trees when these still retain some measure of juvenile resista

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1954.tb00914.x

出版商:Blackwell Publishing Ltd    

年代:1954

数据来源: WILEY

摘要:

An instrument has been constructed for applying minute drops of liquid insecticide to selected parts of individual insects. The principle of the instrument, which is not original, is to express minute amounts of liquid from a hypodermic syringe, and blow the drop from the needle tip by a puff of air. This model is considered to have advantages over previous models working on the same principle. In particular, a very convenient form of fitting was developed for blowing the drop from the needle tip, and fittings of this type could be incorporated in existing similar applicators with little modification of the latter. The high directional accuracy of dropfire necessary for treating selected parts of small insects was achieved.An immersion method was developed for determining the sizes of individual drops of Shell oil P31delivered, and hence the uncontrolled variability of drop‐volume. It showed that the standard deviation in the volumes of drops intended to be equal in size was about 9% of a mean volume of 0.017 μ1. falling progressively to about 2% as the mean volume increased to 0.33 μl. These standard deviations, however, are of limited value, because the sizes of successive drops delivered appeared frequently to be correlated. A method in which the drops are delivered on to an oleophobic surface for measurement of the diameters of the oil lenses formed was found insufficiently accurate for determining the relative variability of drops of P31.A suction method was devised for manipulating, without anaesthetization or chilling, small beetles such asCalandraandTribolium.This enabled large numbers to be individually treated with the applicator in a reasonable time. A similar but slower method was used successfully with the larvae ofEphestia.The biological results achieved have been very satisfactory.The effects of uncontrolled variation in drop size on dose‐response data are disc

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1954.tb00915.x

出版商:Blackwell Publishing Ltd    

年代:1954

数据来源: WILEY

摘要:

A method of measuring narcotic potency is described. Grain weevils (Calandra granaria) are exposed to the narcotic vapour in 2l. round‐bottomed flasks illuminated from the bottom, and narcotic potency measured as number of grain weevils so affected as to be unable to climb the glass walls. Some common anaesthetics have been examined as an illustration of this method. Results are fitted by the probit planeY= A +b1log α+b2logt,whereY= a function of the number of insects affected (probit); α= the thermodynamic concentration of the narcotic vapour;t= time of exposure of insects to the narcotic vapour. The values of the coefficientsb1and b2are discussed in relation to the biological action of the narcotic vapo

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1954.tb00916.x

出版商:Blackwell Publishing Ltd    

年代:1954

数据来源: WILEY

摘要:

At a constant temperature of 24° C. the final larval instar ofDiataraxia oleracealasts about 10 days, during which its resistance to DDT and γ‐BHC as contact insecticides progressively increases up to the 5th or 6th day. It then suddenly decreases, this coinciding with cessation of feeding and the beginning of prepupal formation.Between the 2nd and the 6th days the gross body weight of the last‐instar larva increases from about 0.27 to 0.65g. Under the conditions of the experiments, the LD50 of parathion, as a stomach poison, was linearly related to body weight; on the same basis TEPP was slightly less, and lead arsenate, slightly more, toxic to the larger than to the smaller larvae. However, DDT as a stomach or contact insecticide, and γ‐BHC as a stomach poison were notably less toxic to the larger larvae. For example, the increase in LD50 for an increase in larval body weight of × 2 was about × 11 for DDT as a stomach poison and about × 12 as a contact insecticide.The order of effectiveness of the above insecticides as stomach poisons for the last‐instar larva ofD. oleraceawas parathion>DDT>γ‐BHC>TEPP = lead arsenate. Zinc fluoarsenate and rotenone were relatively non‐toxic. Larvae ofD. oleraceawere repelled by food leaf treated with an extract of

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1954.tb00917.x

出版商:Blackwell Publishing Ltd    

年代:1954

数据来源: WILEY

摘要:

Experiments on the feeding preferences and relative fecundity ofAphis fabaeamong leaves of different ages and kinds were extended to the comparison of different forms of the aphid: apterous and alate virginoparae and gynoparae.All three forms showed a preference for the primary host,Euonymus, over a secondary host, sugar beet, but this preference was strongest in the gynoparae, weaker in the alate virginoparae and weakest in the apterae. The relative fecundity of the aphids on the two kinds of leaf paralleled their feeding preferences most closely in the gynoparae, less so in the alate virginoparae and least in the apterae.All three forms also showed some preference for growing over mature leaves of the same kind, but this preference was strongest in the apterous virginoparae, weaker in the alate virginoparae and weakest in the gynoparae. The relative fecundity of the aphids on the two ages of leaf paralleled their feeding preferences most closely in the apterae, less so in the alate virginoparae and least in the gynoparae.The physiological, ecological and evolutionary significance of the results is discussed in the light of the dual discrimination theory of aphid host selection.

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1954.tb00918.x

出版商:Blackwell Publishing Ltd    

年代:1954

数据来源: WILEY

摘要:

Bean fields are often attacked byAphis fabaevery heavily along the edges: and on a field at Rothamsted in 1948 the sides facing the wind during the primary migration had more colonies than those in the lee of the crop (Johnson, 1950). Additional observations on the distribution of colonies were made on six bean fields at Sutton Bonington in 1950–2.At Rothamsted in 1948 it was assumed that the more numerous colonies on the windward sides of the field followed a heavier deposition of primary migrants there, though the migrants themselves were not observed on the crop. In 1950–2 the locations of primary migrants, as well as of colonies, were recorded in three out of the six fields obser

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1954.tb00919.x

出版商:Blackwell Publishing Ltd    

年代:1954

数据来源: WILEY

摘要:

Field trials on chemical control ofAphis fabaeScop, attacking spring‐sown field beans were carried out during the years 1950–2. The insecticide sprays were applied once only, soon after primary aphid migration into the bean crop had ceased. Destruction of the few aphids present at this early date stops build‐up of the big populations that often develop later.An 0.02% (w/v) parathion spray was used in all three field trials. This gave excellent control ofA. fabaeas did the systemic insecticides Isopestox and Systox at 0.05% (w/v) active ingredient, and nicotine at 0.1% (w/v). Sprays containing allethrin (0.05% (w/v) pure material), pyrethrins (0.05% and 0.02% (w/v) total pyrethrins plus piperonyl butoxide) and an 0.1 (w/v) DDT emulsion gave moderate control.A. fabaewas not controlled in plots treated with an 0.1% (w/v) DDT crystalline suspension, and the aphid population reached a higher peak than in the untreated plots; the suspension is not only relatively ineffective against the aphid, but is more toxic than the DDT emulsion to its Coccinellid predators.On the bean plant the 0.05% (w/v) Systox spray showed some residual toxicity toA. fabaefor at least 5 days after application, but stopped causing 100% kill within 24 hr. 0.02% (w/v) parathion and 0.1 (w/v) DDT emulsion had slight, and 0.02% (w/v) pyrethrins and 0.1% (v/v) nicotine, no residual toxicity.In the year 1950, aphid attack on the field plots was slight and damage insignificant. In 1951, there was a moderate attack and the yield of bean seed was significantly increased by all insecticidal treatments; where aphid control was most efficient (parathion and Isopestox treatments) the yield (16.7–17.1 cwt./acre) was about × 2.7 that of the untreated control (6.3 cwt./acre). In 1952, there was severe aphid attack, and the mean seed yield of the untreated control plots was 1.4 cwt./acre. Plots treated with the DDT suspension yielded 1.3 cwt. seed/acre, but all other insecticides, including the DDT emulsion, increased the seed yield to 10.3–14.8 cwt./acre.All preparations used in 1952, except nicotine, were destructive to adult Coccinellid predators ofA. fabae; Adalia bipunctatawas more susceptible thanCoccinella septempunctata.However, in 1952, predators on the experimental area were too uncommon to be economically

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1954.tb00920.x

出版商:Blackwell Publishing Ltd    

年代:1954

数据来源: WILEY

摘要:

Laboratory and field trials were carried out in the period 1948–52 with DDT, BHC, and other chlorinated hydrocarbon insecticides and with parathion for the control of mangold‐fly larvae (Pegomyia betaeCurtis) mining in the leaves of sugar beet. Kills ranging from 85 to 99% were obtained within 6 days with ‘high’‐ and ‘ low‐volume’ sprays using 6–24 oz. of DDT per acre in the form of an oil emulsion applied as a top cover only. Formulation in oil improved the action of the DDT, it being necessary to use dusts and wettable powders at excessive rates to obtain equivalent kills. DDT was usually superior to BHC when compared at customary rates of application for both insecticides. When oil emulsions were compared side by side, however, as ‘low‐volume’ sprays, DDT was not significantly better than BHC. In the same trial, toxaphene, aldrin and dieldrin also gave kills of the same order as BHC and DDT. With the possible exception of parathion, none of the insecticides used appeared to have any effect upon eggs.Plot yields of two of the trials were determined in the autumn, but only at one trial was there a significant increase in yield on the treated plots. At this trial the mangold‐fly infestation was severe, there being twenty‐five unhatched eggs and twenty larvae per plant at the time of treatment. Attempts were made to assess the degree of defoliation and to relate it to the larval population and to the effect on yield.Commercial insecticides of the ‘stock emulsion’ and ‘miscible oil’ types occasionally caused phytotoxicity when applied to sugar beet at excessive, ‘high‐volume’ rates and concentrations. More serious phytotoxicity was observed in tests of commercial insecticides used at ‘low‐volume’ rates and concentrations. Out of ten products tested, only three were acceptable over the whole range of rates and concentrations employed, whilst four caused injury over the whole range.The results obtained in the field and the laboratory were in agreement but did not always agree with the findings of other workers. BHC has previously been recommended largely on the basis of experiments on larvae mining very small beet plants when in, or just beyond, the cotyledon stage. All the trials by the authors were on sugar‐beet seedlings with about six foliage leaves and normal in size for the time of the year. On these plants BHC proved ineffective both as dust and ‘high‐volume’ spray when used at customary rates, but was effective as a ‘low‐volume’ spray in oil emulsion.The successful control of mining larvae by DDT and other chlorinated hydrocarbons is prob

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1954.tb00921.x

出版商:Blackwell Publishing Ltd    

年代:1954

数据来源: WILEY

摘要:

Experiments were done for three years on street elms at Folkestone and Aldenham to repeat American work on the use of insecticidal sprays to prevent feeding byScolytusbeetles, which carryCeratostomella ulmi, the cause of elm disease. Although the fungus can remain alive in the older annual rings of an infected tree, active disease usually results from fungus freshly introduced byScolytus.Thus spraying is of value on infected, as well as uninfected elms.The results of the experiments supported American conclusions that DDT was superior to benzene hexachloride. A 1.5% solution of DDT in miscible oil gave reasonably good, but not perfect, control, and was much superior to solutions made from DDT in the form of a dispersible powder.Spraying of trees 20–30 ft. high cost over £1 per tree per year, which is considered prohibitive, except for small trees of special amenity or sentimental val

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1954.tb00922.x

出版商:Blackwell Publishing Ltd    

年代:1954

数据来源: WILEY