bluuebunny/crossref_metadata_2025 huggingface dataset:
THE PHYTOTOXICITY OF MINERAL OILS AND HYDROCARBONS
Authors: Ivens G. W.
Published: February 2008

Mineral oils are being increasingly used as herbicides, and there is little doubt that they could be used more effectively if the phytotoxic properties of any particular fraction could be predicted from knowledge of its physical and chemical properties without the need for extensive testing in the field. This paper reviews some of the work that has been done on the correlation of toxicity with physical and chemical properties of oils, and presents some of the results obtained in an investigation into the toxicity of mineral oils and hydrocarbons to plants, being carried out by the Agricultural Research Council Unit of Experimental Agronomy.
TECHNIQUES IN THE BIOASSAY OF SYSTEMIC FUNGICIDES
Authors: Crowdy S. H.
Published: February 2008

In the limited time at my disposal, it would be out of the question to attempt an exhaustive survey of the techniques used in testing compounds for the internal treatment of plant diseases, particularly as some of these tests will be considered by the later speakers. This talk will, in fact, be devoted largely to describing the test which we have developed at Long Ashton, and I will try to indicate some of the difficulties which we have encountered. However, before I deal with the particulars, I will try to outline some general principles.
THE INFLUENCE OF THE HOST ON THE DIMENSIONS OF THE PLANT PARASITIC NEMATODE, DITYLENCHUS DESTRUCTOR
Authors: GOODEY J. BASIL
Published: February 2008

Measurement data and body ratios from eleven populations of Ditylenchus destructor are presented. The data for lengths of males and females have been analysed for variance, and many differences between population means are shown to be significant. The essential importance of structural characters and the care with which sizes and dimensional ratios must be used, in the identification of a species, is emphasized.
STUDIES IN THE RELATIONSHIP OF EELWORMS AND BACTERIA TO CERTAIN PLANT DISEASES
Authors: CROSSE J. E. , PITCHER R. S.
Published: February 2008

Two types of organism are known to be present in strawberry plants suffering from cauliflower disease, namely, eelworms, Aphelenchoides ritzema‐bosi and/or Aphelenchoides fragariae, and a bacterium, Corynebacterium fascians. Neither type, inoculated separately, has consistently reproduced the disease.

An experimental investigation of a possible obligate etiological relationship between the eelworm and the bacterium is described, in which Aphelenchoides ritzema‐bosi and several strains of Corynebacterium fascians were inoculated together and separately.

No abnormalities appeared in the absence of the eelworm. Typical cauliflower symptoms were reproduced only by a combination of the eelworm and strains of C. fascians originally isolated from cauliflower strawberries. Small alaminate leaves and enations appeared in all treatments where the eelworm was introduced, including those where no bacteria were co‐inoculated. Subsequent isolations, however, demonstrated the presence of contaminant strains of C. fascians in the latter plants. The severity of the enation symptom was related to the presence of a particular strain of C. fascians, but the alaminate leaves showed no such correlation. Evidence on the source of the contaminant strains found in the experimental plants is discussed.

In parallel field investigations it was established that eelworm‐infested strawberries showing no cauliflower symptom frequently bore alaminate leaves, with which C. fascians was consistently associated. It is suggested therefore that cauliflower is simply the least frequent of a range of symptoms of a bacterial disease endemic in strawberry plants infested with Aphelenchoides spp.
STUDIES IN RUBUS VIRUS DISEASES
Authors: CADMAN C. H.
Published: February 2008

Degenerate plants of the raspberry variety Lloyd George are usually infected with a complex of viruses that produces mosaic 2 diseases on Baumforth's Seedling B and Norfolk Giant. This complex comprises mild yellows and at least two other viruses, one of which, raspberry leaf‐spot virus, is transmitted by the aphid, Amphorophora rubi. This virus produces characteristic symptoms on Baumforth's Seedling B, Burnetholm Seedling and Norfolk Giant, and it is carried without symptoms by St Walfried, Lloyd George and many other European and North American varieties. Both mild yellows and leaf spot viruses seem to be only subsidiary causes of raspberry degeneration.
ACUTE DIE‐BACK OF CLOVE TREES IN THE ZANZIBAR PROTECTORATE
Authors: NUTMAN F. J. , ROBERTS F. M.
Published: February 2008

The most widespread die‐back of clove trees (Eugenia aromatica) in the Zanzibar Protectorate is caused by Cryptosporella eugeniae sp.nov. The most noticeable symptom is the death of a branch or a portion of a branch, or, in young saplings, of the entire tree; in mature trees infection eventually leads to the semi‐moribund trees now common in almost every clove plantation. The fungus invariably enters through a wound, most often one resulting from harvest damage. Pycnidia, and later perithecia, develop near the point of entry. Internally the infected wood is clearly distinguishable from the healthy by a dark red‐brown stain.

Experimental infections that reproduce typical symptoms can rarely be caused in plants aged 18 to 36 months, and not at all in young seedlings. Experimental infection of older plants becomes more certain with increasing age, and with saplings of 7–10 years old failure is rare.

The prevalence of Cryptosporella die‐back is almost entirely attributable to the destructive methods of harvesting now practised, combined with the presence of much infected material present in the plantations. Suggested control measures are based on the removal of old sources of infection and prevention of future damage, combined with remedial treatment where possible.
Saprophytic Behaviour Of Some Cereal Root‐Rot Fungi
Authors: BUTLER F. C.
Published: February 2008

Factors influencing the saprophytic colonizing ability of two cereal root‐rot fungi, Curvularia ramosa, a vigorous competitive saprophyte, and Helminthosporium sativum, a weak competitive saprophyte, have been investigated. The observed difference in their competitive saprophytic ability could not be ascribed either to a difference in rate of growth or to the ability of the stronger saprophyte, C. ramosa, to produce an antibiotic. The weaker saprophyte, H. sativum, proved, however, to be more sensitive than C. ramosa to antibiotics produced by other soil micro‐organisms. Thus, in spore germination tests with purified fungal antibiotics in vitro, H. sativum proved more sensitive to eight of the ten substances tested than did C. ramosa and was only slightly less sensitive than C. ramosa to the remaining two antibiotics. H. sativum was found also to be generally more sensitive than C. ramosa to the antagonistic effects of certain common soil bacteria. Of the seven bacterial species tested, five caused an appreciable reduction in germ tube development and two reduced germination in H. sativum whereas none of the bacterial species inhibited either spore germination or germ tube development of C. ramosa, and three actually stimulated germ tube development by this fungus.
SOME EFFECTS OF TEMPERATURE AND NITROGEN SUPPLY ON WHEAT POWDERY MILDEW
Authors: LAST F. T.
Published: February 2008

The wheat variety Red Standard was more susceptible to infection by Erysiphe graminis at 14–20° C. than at c. 7° C. Conidia were produced per unit area of pustule more than ten times as rapidly at 14° C. as at 7° C.

The increased susceptibility of wheat to mildew after applying nitrogenous fertilizer (N) was associated with changes in its growth rate. Both growth rate and susceptibility increased to a maximum and then declined; the curves for the two were parallel, with a lag of some days between effect on growth rate and effect on susceptibility. Plants that had passed through the susceptible phase and became resistant to mildew, again became susceptible when supplied with more N. Nitrogen‐deficient plants continuously resisted infection.

The higher the average growth rate during an experiment the greater was the total amount of infection. Increasing the average growth rate was soon followed by a sharp increase in the amount of infection. When plants of two size groups received the same amount of N the initially smaller plants became more heavily infected than the larger plants.
Verticillium Wilt Of The Hop
Authors: KEYWORTH W. G.
Published: February 2008

The two hop varieties Fuggle and OR55 have respectively low and high resistance to wilt caused by virulent strains of Verticillium albo‐atrum. When the pathogen enters through the roots it grows vigorously in the stems of Fuggle plants and slightly in the stems of OR55 plants. Leaf symptoms are correspondingly severe and mild.

If Fuggle stems are grafted on to OR55 roots and vice versa, and the fungus thus invades the stems from roots of the opposite resistance type, it now grows slightly in the Fuggle stems and vigorously in the OR55 stems. Leaf symptoms are correspondingly mild and severe, and thus wilt intensity is related to the variety of root and not to the variety of stem. Evidence is available which shows that this is not due to the transfer of a ‘resistance factor’ generated in the resistant roots.

The variety Fuggle has low resistance to virulent strains of V. albo‐atrum but high resistance to mild strains. As in the case of varietal type this resistance is expressed by vigorous or slight growth of the fungus in the stems (and corresponding leaf symptoms) when the fungi are introduced through Fuggle roots. When they are directly inoculated into the stems there is no differentiation of the strains. If a small inoculum is used both strains induce mild wilt. If a large inoculum is inserted into a pith cavity both strains induce severe wilt. The reaction of the Fuggle stem is thus governed by conditions relating to the type of invasion and not to the strain of pathogen.

It is suggested that this also applies with root inoculations. Normal stems of both Fuggle and OR55 varieties have a high resistance to invasion from a weak source of the pathogen (such as exists in a highly resistant root), and the fungus can invade the stems heavily only from a suitable inoculum source (i.e. a root of low resistance).

Heavy invasion of the stem from a root may be due to

A lowering of stem resistance by:

toxins diffused from the invaded root,

an impairment of normal root function.

An increase in invasive power of the pathogen by:

the establishment of a ‘food base’ in the root,

the diffusion of a ‘fungal accelerator’.

The main conclusions that the primary focus of the disease is in the root and that the normal stems of all varieties possess a similar (and possibly high) resistance is supported by other researches on Fusarium wilt of tomatoes and other wilt diseases and may be of general application.
FACTORS AFFECTING THE PRODUCTION OF LOCAL LESIONS BY PLANT VIRUSES
Authors: MATTHEWS R. E. F.
Published: February 2008

Under uncontrolled glasshouse conditions the number of local lesions produced by a tobacco necrosis virus in beans depended on time of day at which plants were inoculated. Inoculations in the afternoon produced most lesions and inoculations near the end of the night produced least. Tobacco mosaic virus in Nicotiana glutinosa, and lucerne mosaic and turnip mosaic viruses in tobacco showed similar but smaller effects. The variations could affect the results of quantitative experiments with local‐lesion counts.
OBSERVATIONS ON THE INCIDENCE OF CLUB‐ROOT DISEASE OF BRASSICAE IN LIMED SOILS IN RELATION TO TEMPERATURE
Authors: COLHOUN JOHN
Published: February 2008

When cabbage plants growing in artificially contaminated, heavily limed soil were maintained at greenhouse temperatures (mean about 23d̀ C.) for periods of up to 12 days and then at shade temperatures in an open‐air verandah (mean not exceeding 12.5d̀ C.) for up to 21 days only slight attacks of club root developed. Exposure to greenhouse temperatures for at least 6 days and then in a verandah to a mean air temperature of about 16d̀ C. permitted severe attacks to develop. A very severe attack occurred when plants remained in the greenhouse throughout an experiment, but all the plants were healthy when verandah temperatures only were employed.

It is suggested that exposure to favourable temperatures for infection and development of the disease for 12 hr. daily may permit the occurrence of a moderately severe attack.
STUDIES ON THE BACTERIAL DIE‐BACK AND CANKER DISEASE OF POPLAR
Authors: SABET K. A.
Published: February 2008

Artificial freezing caused leaf necrosis and twig die‐back but did not produce cracks or cankers on living branches of three varieties of poplar. Freezing increased the damage caused by a well‐established infection of the bacterial die‐back and canker but checked new lesions. Freezing prior to infection has no appreciable effect on the establishment of the disease.
FIELD STUDIES ON THE INFLUENCE OF WEATHER CONDITIONS ON EGG‐LAYING BY THE CABBAGE ROOT FLY, ERIOISCHIA BRASSICAE BCHÉ. I
Authors: MILES MARY
Published: February 2008

The duration and intensity of egg‐laying by the spring generation of Erioischia brussicue Bché has been studied by removing daily the soil around the stems of cabbage plants on an observation plot. In 1952, eggs were first found on 22 April; the peak period of egg‐laying lasted from 30 April to 22 May, and in the last week of May the rate of egg‐laying declined rapidly. In the peak period the rate of egg‐laying was 5–46 eggs per day per plant with a mean rate of 23 eggs per day per plant. The spring infestation on observed plants was 258–817 eggs with a mean of 533 eggs per plant.

Variation in the daily rate of egg‐laying was associated with weather conditions. Warm sunny weather induced heavy egg‐laying but in cool, wet and windy weather fewer eggs were laid.

A summer peak of egg‐laying associated with the second generation of E. brassicae occurred in late June and early July. Attack in summer was less intense than in spring, a total of 1298 eggs being recorded for the summer peak period (24 June‐14 July) compared with 5796 eggs during a similar period (30 April‐20 May) in spring.

Observations on the numbers of flies that emerged from alternate plants on the observation plot showed that the low rate of egg‐laying in summer was not the result of a lack of adults. Consideration of biotic and climatic factors suggested that while high temperatures and long periods of sunlight stimulated the summer flies to great activity the environment provided little food to sustain them, and in consequence they did not survive to complete oviposition.

The puparia were collected from the undisturbed alternate plants in order to obtain information on the numbers of E. brassicae that reached maturity. It was estimated that 5–6% of the eggs reached the pupal stage; approximately two‐thirds of the puparia gave rise to flies and one‐third were parasitized. About 9% of the puparia remained viable in the soil to give rise to the following spring generation, about 90% having given rise to flies in the year in which they were formed.
TESTS OF SYNERGISM BETWEEN NICOTINE AND THE PYRETHRINS
Authors: TURNER NEELY , BLISS C. I.
Published: February 2008

Synergism between nicotine and pyrethrum applied by injection to adult Oncopeltus fasciatus Dal. has been reported by Turner (1951).

When these insecticides were applied alone and as a mixture to adult Tribolium castaneum Hbst., using a dipping technique, the data indicated that independent joint action occurred. Similar action could be eliminated because the two insecticides had varying relative potency.

Since the effect of the pyrethrins has been short‐lived in some insects, it was postulated that the absence of synergism might be caused by failure of the nicotine to reach a site of action while the pyrethrins were still acting.

Application of nicotine, followed later by treatment with pyrethrins, gave evidence of synergism. A test in which the interval between treatments was varied from ¾ to 6 hr. showed that toxicity was greatest with the shortest interval between applications, and evidence of synergism had practically disappeared after 6 hr. The maximum amount of synergism observed was about twofold.
BIOASSAY SYSTEMS FOR THE PYRETHRINS: IV. STOICHIOMETRIC RELATIONS WITH PYRETHRUM SYNERGISTS*
Authors: BLACKITH R. E.
Published: February 2008

The sharp limitation of synergistic action when equimolecular proportions of the pyrethrins and some of their synergists are tested against flying mosquitoes has been confirmed when such mixtures are employed in assays using Calandra granaria L. crawling on oil‐films on filter‐paper.

Limitation of the relative potencies of pyrethrum‐synergist mixtures appears to be a general property, and except for piperonyl butoxide the limiting relative potency is attained at equimolecular proportions of insecticide and synergist.

These observations are discussed in connexion with a general theory of insecticidal action.
BREEDING PEARS FOR RESISTANCE TO THE PEAR SCAB FUNGUS, VENTURIA PIRINA ADERH.
Authors: STANTON W. R.
Published: February 2008

Clonal isolates of Venturia pinna, shown in a previous paper to differ in range of pathogenicity, have been used to inoculate the following pear seedlings: (i) resistant seedlings from families which appeared to be segregating for resistance under field conditions, (ii) two whole families of field‐resistant × field‐susceptible parentage.

In (i), it was found that clones of the fungus could infect some of the seedlings hitherto regarded as field‐resistant. In (ii), segregation for susceptibility in the two families varied, according to the clone of the fungus used, from approximately a 1:1 ratio down to ‘all resistant’. Resistance to individual clones appeared to be dominant to susceptibility, but further data are required before attempting a complete interpretation.

There was a general correlation between susceptibility to the different clones. Those that produced the most infection were isolated from the parental varieties of the seedlings. This correlation was not, however, complete and clones differing in host origin tended to attack different groups of seedlings.
THE EFFECT OF REPEATED SPRAYING OF INSECTS IN INCREASING THEIR RESISTANCE TO INSECTICIDES: I. DEVELOPMENT OF RESISTANCE TO DDT IN A STRAIN OF DROSOPHILA MELANOGASTER MEIG.
Authors: TATTERSFIELD F. , KERRIDGE JILL R. , TAYLOR JEAN
Published: February 2008

Successive spraying with DDT suspensions of the adults of a wild colony of Drosophila melanogaster and the progeny of survivors enhanced the resistance to that insecticide.

The rate at which resistance increased depended on: (1) the relative proportion of resistants to susceptible individuals, or (2) the intensity of selection as measured by the concentration of DDT, the proportion killed or on both. The resistance of the populations of the insects fluctuated considerably whether subjected to successive sprayings or not, and in one sprayed series there was some indication of a rhythm with peaks of susceptibility occurring at regular intervals.

Enhanced resistance may show a change of slope in the probit log concentration regression line, leading to different relative values at different levels of mortality, or by a parallel shift of the regression line. The former appears to be a preliminary stage of selection and indicates a change in the frequency distribution within a population.

Increasing the concentration of DDT, slowly or rapidly, may have enhanced resistances at an increased rate, but the series sprayed with the lower initial concentration reached finally the same end point, as judged by the values of log lc. 50.

During the course of these experiments the insects developed sensitivity to carbon dioxide (used in anaesthesis). Its bearing on our work is considered in Part II.
STUDIES ON THE FEEDING OF MYZUS PERSICAE (SULZ.) ON RADIOACTIVE PLANTS
Authors: WATSON MARION A. , NIXON H. L.
Published: February 2008

Adult apterae of Myzus persicae (Sulz.), were fed, after a period of fasting, on leaves containing radioactive phosphorus. The weight of sap imbibed by the aphids after varying feeding times was estimated by relating their radioactivity, at the end of each feeding period, to the activity per unit fresh weight of the leaf lamina on which they fed. The calculations were made on the assumption that 32P is uniformly distributed in the leaf tissues.

The mean rates of uptake so estimated were about 10 μg. of sap for the first hour of feeding; 40 μg/hr. between 1 and 4 hr. feeding, and 17 μg./hr. between 6 and 24 hr. feeding. The decrease in apparent rate of uptake with the longer feeding times is attributed to loss of 32P in nymphs born during the feeding period.

When aphids were fed on seedlings raised in water culture solution containing 32P no activity was detected after 5 min. feeding and an insignificant fraction after 15 min., but when the isotope was introduced by immersing the leaves for several days in the culture solution, aphids fed for 5 and 15 min. became appreciably active.

The increase in rate of uptake after 1 hr. of feeding indicates that aphids do not start to feed normally until they reach the phloem, but the activity after short feeding times suggests that previously starved aphids feed to some extent on other tissues, possibly only on the epidermis.
FACTORS AFFECTING THE PRODUCTION OF LOCAL LESIONS BY PLANT VIRUSES
Authors: MATTHEWS R. E. F.
Published: February 2008

Beans inoculated with tobacco necrosis virus were kept in the dark at different temperatures for 1 hr. before and 1 hr. after inoculation; in this experiment the number of lesions increased with temperature over the range 55–82° F.

The effect of 30 min. periods of darkness before or after inoculation depended on the time of day, the number of local lesions usually being decreased. Prolonging the night period before inoculation sometimes increased the number of lesions.

Light appeared to be more important than temperature in controlling the daily variation in susceptibility. However, in a test over a 30 hr. period this variation continued even when plants were placed under constant conditions before and after inoculation.

When plants that had been kept in the dark were exposed to light of about 800 f.c. intensity for 1 min. immediately before inoculation the number of local lesions was doubled.
STUDIES ON THE EFFECT OF ASSOCIATED SOIL MICROFLORA ON FUSARIUM UDUM BUTL., THE FUNGUS CAUSING WILT OF PIGEON‐PEA (CAJANUS CAJAN (L.) MILLSP.), WITH SPECIAL REFERENCE TO ITS PATHOGENICITY
Authors: VASUDEVA R. S. , GOVINDASWAMY C. V.
Published: February 2008

The interaction of certain soil saprophytes and Fusarium udum, the wilt organism of pigeon‐pea, with special reference to their effect on pathogenicity, has been studied. The filtrates of Aspergillus niger, Rhizopus nigricans and mixed filtrates of all the saprophytes inhibited the growth of Fusarium udum on solid medium. This inhibition of F. udum has been shown to be due to unfavourable reaction of the medium rather than to food exhaustion or the presence of toxic substances. The culture filtrates after passage through soil beds failed to affect adversely the growth of F. udum because of the change in pH. Inoculation experiments have indicated that only Rhizopus nigricans is effective in reducing the incidence of wilt because of its faster rate of growth. The mixed inocula of the organisms and mixed filtrates of all the saprophytes have also been observed to be effective in reducing wilt incidence. Aspergillus terreus appears to enhance the virulence of Fusarium udum.
PHYSIOLOGICAL RACES OF PHYTOPHTHORA INFESTANS: A COMPARISON OF THE DIFFERENTIAL HOSTS AT THE PLANT BREEDING INSTITUTE, CAMBRIDGE, WITH THOSE OF THE SCOTTISH SOCIETY FOR RESEARCH IN PLANT BREEDING
Authors: HOWARD H. W.
Published: February 2008

At the Plant Breeding Institute, Cambridge, there have been recognized three physiological races of blight (Phytophthora infestans), A, B and C; and at the Scottish Society for Research in Plant Breeding, Edinburgh, there have been used five races, A, B1, B2, C and D, obtained in the British Isles.

It is shown that the two Cambridge types of differential hosts, AbC and ABc (where A= resistant to race A, a= susceptible to race A, etc.), are Ab1b2CD and AB1B2cD respectively on the Scottish scheme, and that the Cambridge races A, B and C correspond to the Scottish races A, B1 and C respectively.

A number of blight isolates were tested on both the Cambridge and Scottish differential hosts. Isolates of race types A, B1, B1, C and D were found.

The identification and origin of physiological races of blight, and the breeding of blight‐resistant potatoes, are discussed.
VALSA EUGENIAE IN RELATION TO THE SUDDEN‐DEATH DISEASE OF THE CLOVE TREE (EUGENIA AROMATICA)
Authors: NUTMAN F. J. , ROBERTS F. M.
Published: February 2008

The sudden‐death disease of the clove tree is invariably associated with the fungus Valsa 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. Valsa is 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 of Valsa attack on young trees when these still retain some measure of juvenile resistance to it.
A METHOD FOR MEASURING THE NARCOTIC ACTION OF CHEMICALS USING THE GRAIN WEEVIL, CALANDRA GRANARIA
Authors: BRADBURY F. R. , ARMSTRONG G.
Published: February 2008

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 plane

Y= A +b1 log α+b2 log t,

where Y= 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 coefficients b1 and b2 are discussed in relation to the biological action of the narcotic vapours.
WIND DIRECTION AND THE INFESTATION OF BEAN FIELDS BY APHIS FABAE SCOP.
Authors: TAYLOR C. E. , JOHNSON C. G.
Published: February 2008

Bean fields are often attacked by Aphis fabae very 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 observed.
THE CONTROL OF BLOWFLIES INFESTING SLAUGHTER‐HOUSES
Authors: GREEN A. A. , KANE JOYCE
Published: February 2008

A field experiment has been conducted to control blowflies which fell as mature larvae from railway wagons carrying domestic refuse and infested the soil at the sidings of a refuse collecting and sorting depot.

The surface of the soil was treated so that the insects were exposed to insecticide both as migrating larvae and newly emerged adults. Dusts and emulsions of DDT and BHC were compared on the basis of equal cost. A method was evolved for obtaining quantitative measurements of the effectiveness of the treatments by trapping flies emerging from the soil.

DDT was more effective than BHC, dusts were more effective than emulsions, and small quantities applied twice weekly were more effective than a correspondingly heavy dose applied monthly. DDT dust applied twice weekly was estimated to have killed 79.7% of larvae and pupae and 95.7% of emerging adults: overall control was 99.1%. Equally high control was maintained when the method was adopted as a routine measure by the local authority.
GROUNDNUT ROSETTE DISEASE IN TANGANYIKA
Authors: EVANS A. C.
Published: February 2008

Rosette disease of groundnuts in Tanganyika is brought into the crop by infective alatae of Aphis craccivora: spread within the crop is by apterae and alatae. During the dry season the aphids maintain themselves on self‐set groundnuts and on two genera of Leguminosae: Vigna and Millettia or Lonchocarpus. No native source of the virus causing rosette disease has been discovered, but self‐set groundnuts carry over the virus from one cropping season to the next. Syrphid larvae and other predators are important in controlling the vector. Preliminary spraying trials with 0.5% schradan gave promising results in controlling the aphids on groundnut crops and consequently checking the spread of rosette disease. Selections of the variety Mwitunde showed the lowest incidence of rosette infection and gave the highest yields in trials in 1952.
SAP‐TRANSMISSIBLE MOSAIC DISEASES OF SOLANACEOUS CROPS IN TRINIDAD
Authors: DALE W. T.
Published: February 2008

Four sap‐transmissible viruses were isolated from cultivated Solanaceae in Trinidad: (1) tobacco mosaic virus, from tobacco, tomato and sweet pepper; (2) cucumber mosaic virus, from tobacco and petunia; (3) ‘pepper vein‐banding virus’, probably related to pepper mosaic viruses in Puerto Rico and Brazil, from peppers and tobacco; (4) ‘egg‐plant mosaic virus’, possibly related to the tobacco ring‐spot virus, from egg‐plant and tomato. Pepper vein‐banding virus causes leaf‐crinkling and vein‐banding in Physalis floridana, petunia, various Nicotiana spp. and most peppers; the Large Bell Hot pepper is killed; tomato and egg‐plant are immune. Egg‐plant mosaic virus produces mosaic, ring‐spotting, or both, on different solanaceous species. It also gives local and systemic ring‐spotting on Chenopodium hybridum and necrotic local lesions on the primary leaves of cowpea (var. Black‐eye); cucumber is a symptomless carrier. Only cucumber mosaic virus was found naturally infecting non‐solanaceous hosts, cucumber and certain common wild plants.

The thermal inactivation point of pepper vein‐banding virus is 62° C, its dilution end‐point 2×10‐5 and its longevity in vitro 6 day s at 23–30° C.; corresponding values for egg‐plant mosaic virus are 78° C., 10‐6 and over 3 weeks. Aphisgossypii transmits cucumber mosaic and pepper vein‐banding, but not egg‐plant mosaic, of which Epitrix sp. is an occasional vector. Tobacco mosaic, as elsewhere, probably has no regular insect vectors in Trinidad.
STUDIES IN THE MODE OF ACTION OF INSECTICIDES
Authors: HOPF H. S.
Published: February 2008

Homogenates of the thoracic nervous system of Locusta migratoria migratoriodes are able to hydrolyse acetylcholine (ACh) and o‐nitrophenylacetate (NPA), and this hydrolysis can be inhibited by tetraethylpyrophosphate (TEPP) at approximately the same molar concentration for both substrates. It is possible that one acetyl‐esterase is responsible for the breakdown of the two substances, and there is no reason to assume the existence of a specific acetylcholinesterase. In normal horse serum, on the other hand, the pseudocholinesterase is quite distinct from the enzyme responsible for the breakdown of NPA.

In an attempt to correlate the inhibition of the locust nerve cord acetylesterase with toxic activity to insects and mice, four chlorinated diethyl‐phenylphosphates were tested as contact poisons against a number of insects and by injection against locusts and mice, and also as in vitro inhibitors of locust nerve cord acetylesterase and horse‐serum pseudocholinesterase. The chemicals were the 2‐chloro‐, 4‐chloro, 2:4‐dichloro‐ and 2:4:5‐trichloro‐ analogues of diethyl‐phenylphosphate.

Good correlation exists between their in vitro activity against the nerve‐cord acetylesterase and their contact activity to aphids, but not between the former and injection toxicity to locusts. No correlation could be established between the inhibition of horse‐serum cholinesterase and injection toxicity to mice. It is thought likely that the inhibition of nerve‐cord acetylesterase is of greater importance in aphids than in other insects, where the toxic action of the phosphoric esters is at least partly concerned with other vital processes, and that a detoxication mechanism in the mammal breaks down some of the phosphoric esters, but not others.
THE PRODUCTION OF ANTIBIOTICS IN SOIL
Authors: WRIGHT JOYCE M.
Published: February 2008

Conditions affecting the production of gliotoxin by a strain of Trichoderma viride, known to produce this antibiotic in synthetic culture media, were studied in two types of soil, a highly acid, sandy podsol from Wareham Heath and a less acid garden soil. High yields of an antibiotic substance, which results from bioassays showed to be similar to gliotoxin, were obtained from both inoculated soils when autoclaved and supplemented with organic material. The autoclaved soils behaved differently when unsupplemented; Wareham soil supported production of the antibiotic but little or none was produced in the garden soil. No antibiotic activity could be demonstrated in soil which had not been inoculated with T. viride.

Acidification of unsupplemented garden soil by addition of sulphuric acid had a favourable effect on production of the antibiotic, but raising the pH of Wareham soil by addition of calcium hydroxide also increased the yield. These effects, therefore, cannot be due simply to the change in pH of the soil.

The beneficial effect of autoclaving the soil on production of the antibiotic assumed to be gliotoxin was analysed and separated into three distinct effects, elimination of the microflora, increase in availability of nitrogen compounds and increase in available carbon compounds. The last effect was considered to be of greatest significance.

The antibiotic was produced in normal Wareham soil if supplemented with additional carbon compounds, but not in garden soil unless this had also been acidified before inoculation. A chromatographic method of bioassay used in the later work gave more substantial evidence that the antibiotic produced in the soil was, in fact, gliotoxin.
THE RELATIONSHIP BETWEEN NICKEL TOXICITY AND IRON SUPPLY
Authors: CROOKE W. M. , HUNTER J. G. , VERGNANO ORNELLA
Published: February 2008

The influence of varying levels of iron and substrate pH on the uptake of nickel and the intensity of toxicity symptoms in oat plants have been investigated using sand‐and water‐culture techniques.

Nickel‐toxicity symptoms (both necrosis and chlorosis) are less severe when the concentration of iron in the nutrient solution is high. The reduction in degree of necrosis is related to a reduced content of nickel in the leaf blades, whilst that of chlorosis is related to the Ni/Fe ratio in the leaf blades—an internal antagonism being indicated in the latter case.

A reciprocal relationship exists between the nickel and iron contents of the leaf blades; the nickel content is materially reduced by high concentrations of iron in the nutrient solution, and the iron content by nickel, the former being the more pronounced effect.

Uptake of nickel increases with increasing pH for a constant iron level in the substrate, although the degree of necrotic symptoms is similar over pH range 4–7. Iron uptake is reduced by both nickel and increasing pH and results in chlorosis at pH values of 5·5 and above.

For a constant level of iron supply the phosphate content of the stem extracts is higher the greater the degree of nickel toxicity; the phosphorus status of the plant may be a factor in producing nickel toxicity but if so, it has to be considered in relation to other factors.
STUDIES ON A CANKER DISEASE OF CYPRESSES IN EAST AFRICA, CAUSED BY MONOCHAETIA UNICORNIS (COOKE & ELLIS) SACC
Authors: JONES D. RUDD
Published: February 2008

Strains A and B of Monochaetia unicornis produced cankers following inoculation into Cupressus arizonica, C. benthami, C. lusitanica, C. macrocarpa, C. sempervirens, C. torulosa, Cupressocyparis leylandii, Chamaecyparis lawsoniana, Juniperus procera and Thuja orientalis. Strain D was parasitic only on Juniperus procera.

Monochaetta unicornis grew well on agar media prepared from bark and sapwood extracts of Cupressus species and Juniperus procera but only slowly on Podocarpus gracilior bark agar.

Test trees of five species of Cupressus, grown commercially in East Africa, were alternated with artificially inoculated trees of C. macrocarpa in field plots. The subsequent development of natural infections in trees of the test species confirmed field observations that C. macrocarpa was the most susceptible.

Plots (each of 340 trees) of the five species were inoculated with mycelium. In 4 months, the most extensive cankers had developed in C. benthami, and this species also had the largest number of active cankers and the most rapid height growth. When examined again 4 months later, C. macrocarpa had the most extensive cankers and 60% of them were still active as compared with 20% in C. lusitanica and 6% in C. benthami. Delayed inoculation following wounding confirmed these results and in the dry season the number of successful infections was always highest in C. macrocarpa.

Periderm was formed in the bark and sapwood of the Cupressus species in response to wounding, the process being slower in C. macrocarpa and C. torulosa than in other species. Secondary growth was most rapid in C. macrocarpa. It is suggested that rapid height growth coupled with rapid secondary growth in this host favour the growth of the pathogen rather than the host reaction, and C. macrocarpa is consequently very susceptible. During the rains the fungus develops as rapidly in species having a slower secondary growth rate but in the ensuing dry season such infections dry out and the cankers are occluded.
FUNGAL ROTS OF APPLES WITH SPECIAL REFERENCE TO GLOEOSPORIUM SPP.
Authors: Wilkinson E. H.
Published: February 2008

The storage of fruit under artificial conditions has increased considerably during the past thirty years despite the high capital charges and expense required for the erection and maintenance of the storage chambers. In 1925 there was storage space for 2570 tons of apples, whereas in 1950 this had increased to space for approximately 85,000 tons, consisting mainly of refrigerated gas‐storage installations. This total is equivalent to 5,000,000 bushels and does not include the large quantities of fruit stored under ‘barn’ conditions or the more recently introduced ‘moss’ storage system.
EFFECT OF CERTAIN CHLORONITROBENZENES ON GERMINATION, GROWTH AND SPORULATION OF SOME FUNGI
Authors: REAVILL MARY J.
Published: February 2008

When grown in an atmosphere saturated with tetrachloronitrobenzene (TCNB) vapour, Botrytis cinerea showed retarded germination and colony growth and its sporulation was completely suppressed. Retardation of growth was greater on dilute or acidified media and at lower temperatures.

Similar effects were shown by Bhizoctonia solani, Phytophthora parasitica, Mucor hiemalis and Trichoderma viride but none of these was as sensitive as Botrytis cinerea, especially as regards linear growth. Of two strains of Fusarium caeruleum, one was much more sensitive than the other, both in linear growth and sporulation. Pythium deBaryanum was unaffected in its growth rate.

TCNB, as a growth repressant, is fungistatic without being fungicidal.

With fungi which are sensitive, tetrachloronitrobenzene was more effective than the penta‐derivative, except for Trichoderma viride where the converse applied.
THE FUNGICIDAL CONTROL OF LETTUCE DOWNY MILDEW, CAUSED BY BREMIA LACTUCAE
Authors: POWLESLAND RUTH , BROWN W.
Published: February 2008

Protection experiments carried out in the greenhouse showed that preparations of thiram, zineb, ferbam and ziram were superior to cuprous oxide and copper oxy‐chloride preparations, in controlling downy mildew of lettuce and in lack of phytotoxic effect.

Tests made in winter on lettuce seedlings grown in Dutch lights, showed that Bremia lactucae attack reduced the stand of seedlings, diminished their size and weight, and, when the crop was planted out into the open ground, reduced survival in the field and slightly delayed the date of reaching maturity. The best overall results in protecting foliage against downy mildew were given by thiram and zineb preparations.
THE ABSORPTION, TRANSLOCATION AND BREAKDOWN OF SCHRADAN APPLIED TO LEAVES, USING 32P‐LABELLED MATERIAL
Authors: BENNETT S. H. , THOMAS W. D. E.
Published: February 2008

When 32P‐labelled schradan was sprayed on the leaves of apple stocks and seedlings, broad and runner beans, Coleus and chrysanthemums, some was absorbed, some evaporated and the rest remained for a considerable time on the leaf surface as a residue removable by aqueous leaching. Absorbed material is defined as that present on or in the plant and not removable by aqueous leaching at the time of harvest.

Evaporation losses even from glass slides were lower than theoretical expectation, from leaves they were much less.

It is possible that some breakdown of the schradan occurs within the cuticular layer. Comparisons of the absorption rates of upper and lower surfaces of leaves support the theory that absorption proceeds through the cuticle in preference to vapour phase entry through the stomata.

Temperature and illumination have important effects on absorption.

Young leaves have been shown to be generally more absorptive than the older leaves. Comparisons have also been made of the absorption by different species. Such data must be accepted with caution as, although physical conditions were the same for all the species within an experiment, the physiological stage of development of the different plant species will not be strictly comparable.
EXPERIMENTS ON BLACK LEG DISEASE OF SUGAR‐BEET SEEDLINGS
Authors: GATES L. F. , HULL R.
Published: February 2008

Phoma betae was usually the predominant pathogen attacking sugar‐beet seedlings in the field in eastern England, but Pythium spp. sometimes predominated when the seedlings were very young. Fusarium spp. were associated with acid soil conditions. Rhizoctonia solani only occasionally caused severe losses.

Black leg, caused chiefly by Phoma betae, was most prevalent at low soil temperatures when, in stands from untreated seed, up to 45 % of the seedlings were attacked. Disease decreased by 0·8 to 2·4 diseased seedlings per 100 in stands from untreated seed per 1° F. rise in soil temperature. Seed treated with Panogen,* thiram and ethyl mercury phosphate regularly gave better stands in small‐scale trials than seed treated with Ceresan or Agrosan. In large‐scale experiments average increase in seedling emergence following treatment with Panogen, thiram and Agrosan varied in different years between + 6·4 and + 19·2 %. Average response to BHC soil dressing was + 4·2 and + 8·6 %. Response to seed dressings increased as the time taken for emergence increased and as percentage emergence decreased; when emergence was 50 % of the possible, dressing gave on average 20 % more seedlings. Response to dressing increased as soil became more acid or alkaline than the optimum for beet, and was lower on heavy soils and on soils dressed with farmyard manure.

Maximum emergence varied from year to year between 2100 and 2700 seedlings per oz. seed; minimum between 690 and 1050. Emergence of both treated and untreated seed varied greatly and was related to time taken for emergence, suggesting that effects of soil moisture, temperature or texture are important. Emergence WM not correlated with pH, but when the pH was below 6·5 or above 8·7 it was not more than 75 % of that at pH 7·0–7·4. In 2 out of 3 years emergence was increased by 32 and 84 seedlings/oz. seed by each extra cwt. per acre of inorganic fertilizer (N, P, K). Seed rate, cultural operations and drill type had no consistent effect.

A 1 % increase in seedling stand increased the final plant population on average by 0·2%.
THE USE OF SEED DRESSINGS CONTAINING γ‐BHC IN THE ESTABLISHMENT OF SUGAR‐BEET SEEDLINGS
Authors: JONES F. G. W. , HUMPHRIES K. P.
Published: February 2008

From 1949 to 1952 field trials were made to determine the effect of seed dressings containing γ‐BHC, with and without the addition of organic mercurial compounds, upon the establishment of sugar‐beet seedlings. Most of the trials were made in fields where no serious pest problems were anticipated. The 1949 trials established the concentration of γ‐BHC non‐phytocidal to sugar‐beet seedlings. Later trials tested the effect on pre‐ and post‐singling plant populations of dressings applied to natural or rubbed seed sown at standardized rates. Parallel tests of dressed seed were made on farms representing a variety of soil types, It was found that the phytotoxiCity of γ‐BHC varied with season and soil type, but that a dressing containing 40 % was usually safe. In these trials, the benefits from seed dressing were, as a rule, slight. Generally the combined mercury‐γ‐BHC seed dressing gave the best pre‐singling stand of plants. Most of the improvement was attributable to the organic mercury rather than to the γ‐BHC, but where pest attacks occurred, γ‐BHC gave marked improvements in stand. Wireworm appeared to be the chief pest controlled: control of pygmy mangold beetle was only partial.
PROTECTION OF SORGHUM AGAINST SOIL FUNGI, SOIL PESTS AND COVERED SMUT BY COMBINED INSECTICIDE‐FUNGICIDE SEED DRESSINGS
Authors: TARR S. A. J.
Published: February 2008

Treatment of sorghum (Sorghum vulgare) seed with fungicide dressings controlled covered smut (Sphacelotheca sorghi), the major disease of sorghum in the Sudan, and usually resulted in appreciably better stands. In the Sudan Gezira, powder dressings containing 20–40%γ‐benzene hexachloride (γ‐BHC) applied at the rate of 1g./1b. of seed effectively protected sorghum seedlings from root attack by chafer grubs (Schixonycha sp.) and significantly increased stands and yields. No certain evidence of this effect was obtained with dolichos bean (Dolichos lablab) or groundnut (Arachis hypogaea), and the different responses shown by these plants as compared with sorghum are attributed largely to differences in seed germination and root system. An application rate of 0·08 %γ‐BHC/seed was sometimes slightly but appreciably phytotoxic to sorghum in the field and more markedly so in greenhouse experiments. A powder containing 25% thiram and 20%γ‐BHC applied at the rate of 1g./1b. of seed is recommended as the standard seed dressing for sorghum in the Sudan.
TOXIC EFFECTS OF HEAVY METALS ON CROP PLANTS GROWN IN SOIL CULTURE
Authors: FORSTERM W. A.
Published: February 2008

A number of pot experiments were made on various crops, to study the effects on the chemical composition of the plants of treating the soil with cobalt, copper or nickel sulphates, or with the cupric or ferric salts of ethylenediamine‐tetraacetic acid (EDTA).

The tops of copper sulphate‐treated plants usually contained higher concentrations of copper, manganese, calcium and magnesium and lower concentrations of potassium and phosphorus, than those of control plants.

The most marked effect of cobalt on oat was to increase the concentration of Ca+Mg in the tops; nickel had a profound effect on the composition of barley tops.

Total iron concentration was reduced in oat by cobalt and copper, and in barley by copper and nickel application. Symptoms of iron deficiency appeared only in the oat plants, their incidence being correlated with the reduction in iron concentration in the tops.

The ferric salt of EDTA tended to reduce the incidence of iron deficiency symptoms produced in oat by copper sulphate, but also gave rise to distinct toxic effects. Plants given the cupric salt of EDTA contained unusually large amounts of iron.