bluuebunny/crossref_metadata_2025 huggingface dataset:
The control of coffee rust in Kenya by fungicides
Authors: RAYNER R.W.
Published: February 2008

The results are reported of a series of four factorial field trials carried out at Ruiru, Kenya, to determine the effect on the control of coffee rust (Hemileia vastatrix B. et Br.) of the main variables associated with the application of copper fungicides, i.e. concentration, volume per acre, leaf surface to which applied, time of application, and types of fungicide and application used.

Rust control increased with log concentration, there being evidence for a linear relationship. As neither asymptotic nor optimal values occur the optimum for commercial practice must be determined by economics and possible phytotoxic effects.

Control also increased with volume per acre, but adjusting the amount of spray residue via concentration was more effective and less wasteful of fungicide than via volume. Upper‐surface application was as effective as lower in one trial at all concentrations, and in another at the higher concentrations. It is considered that liberation of fungicide from upper surface residues by rain, and the presence of thick aggregations of these residues may be of importance for rust control.

Differences in rust control following the use of three spraying machines were correlated with the differences in amount of spray residue on the leaves, there being a linear relation to log residue. For the same rust control, a mist‐blower with swirl‐plate atomisation required the greatest expenditure of fungicide per acre and a pneumatic hand‐sprayer, closely approached by a mist‐blower with spinning‐cage atomisation, the least. However, to obtain as heavy residues and as good rust control as with the hand‐sprayer, higher concentrations were necessary. At the same copper content of spray fluid no differences in rust control by Burgundy mixture, cuprous oxide (as ‘Perenox’) and copper oxychloride (as ‘Blitox’) were found. Some observations on the fungicides fermate, cuprous oxide in oil and captan were made. Captan did not increase foliage density. Evidence that this is directly influenced by copper sprays is presented.

For reducing the amount (but not the percentage) of rust attack March and April sprays were most effective, January least, and October was intermediate. The earlier sprays reduced the effect of later ones. Reduction of inoculum in January to March did not reduce the July‐August rust peak. The implications are discussed.
Thysanopteran populations overwintering in hedge bottoms, grass litter and bark
Authors: LEWIS T. , NAVAS D. E.
Published: February 2008

A qualitative and quantitative survey was made of thysanopteran populations overwintering in hedge bottoms, grass litter and bark. The sampling methods used are described. The most common thrips found in these habitats were grass‐infesting species, particularly Aptinothrips rufus (Gmelin) in litter and Limothrips cerealium Hal. in bark. L. denticornis Hal. occurred in both, but preferred litter, whereas Chirothrips manicatus Hal. was almost entirely confined to dead grass inflorescences and litter. Populations were generally more dense in litter than in bark, bark with the most crevices containing most thrips. None of the populations examined showed a significant decline during the winter. Possible predators of thrips were collected from bark.

L. cerealium aggregated in bark crevices of suitable width, and touch was probably more important in the selection of crevices than light. In thick pine bark, this species seemed to penetrate into the deeper layers to spend the most severe winter months.
The behaviour and control of the blackcurrant gall mite Phytoptus ribis (Nal.)
Authors: SMITH B.D.
Published: February 2008

By placing groups of potted blackcurrant bushes at weekly intervals in a plantation infested with Phytoptus ribis during 1959, 1960 and 1961 it was shown that the maximum rate of mite emergence and infestation coincided with the blossom period and that approximately half of the total infestation took place at this growth stage.

Effective migration continued for 12–14 weeks and during the early part of this period the rates of emergence and infestation were directly affected by temperatures below 50° F. Temperatures above 50° F., particularly towards the end of the migration period increased the rate of desiccation of the old buds and forced mites to emerge.

When lime sulphur was placed, by hand, in all new leaf axils at weekly intervals, on bushes where there were large mite infestations, complete control was achieved, but this was not found where all the old wood or all infested buds were covered with lime sulphur. These investigations indicate that, for commercial control, repeated treatments must be made especially during the blossom period.

Single applications of 1% lime sulphur with a wetting agent were made at various developmental stages on blackcurrants at Long Ashton in 1961 and the percentage reduction of infestations of the blackcurrant gall mite estimated. The most effective were those during the blossom period and particularly where they coincided with the periods of greatest mite emergence and penetration of new axillary buds. Applications were made from the first open flower stage until early June; some control, although progressively decreasing, was given by applications made up to 6 June. More than one spray was necessary for adequate commercial control.

Two commercial wettable sulphur powders, applied at the first open flower stage and again 2 weeks later, were found to be approximately as effective as lime sulphur. A wetting agent was used in all the sprays but at half the concentration with the wettable powders.

Thiodan did not appear to provide a better control of the gall mite than lime sulphur when two applications of each were made with a wetting agent. Three applications gave better results than two and the addition of a wetting agent was of great importance: where none was used an increase of infestation resulted after three applications, whilst a 94.1% reduction was achieved by three applications of 1% lime sulphur with 0.025 dinonyl sodium sulphosuccinate (0.0125% active ingredient). Hand lances using high volumes of liquid were used throughout.
Resistance in oak (Quercus spp.) to defoliation by Tortrix viridana L. in Roudsea Wood National Nature Reserve
Authors: SATCHELL J. E.
Published: February 2008

Resistance in oak (Quercus spp.) to defoliation by caterpillars of Tortrix viridana L. was studied in an oak wood and a mixed wood in Roudsea Wood National Nature Reserve. When defoliation is severe in the oak wood a few trees there and most of the oaks in the mixed wood retain relatively undamaged canopies. Their resistance was found to be phenological. The resistant trees in the oak wood flush either later or earlier than those that become defoliated; those in the mixed wood flush later. On late‐flushing trees the buds open too late for newly hatched larvae to penetrate them, the resultant mortality reducing the larval population below the level at which damage is severe. The early‐flushing trees carry as many larvae per leaf cluster as non‐resistant trees but do not show severe defoliation because they produce more foliage and ‘grow away’ from the attack.
A method of assessing caterpillar populations on large forest trees, using a systemic insecticide
Authors: SATCHELL J. E. , MOUNTFORD M. D.
Published: February 2008

A method is described of obtaining estimates of numbers of leaf‐feeding caterpillars on oak trees which might be applied to other large, irregularly‐branched forest trees. A systemic insecticide was introduced to tree boles through cuts in the bark, and poisoned larvae were collected on sheets as they fell off the foliage. Larvae remaining on the trees were subsequently sampled and included in the population estimate. Apart from the cuts, which eventually callused over, the method did not injure the trees.
A study of the absorption of 14C‐labelled DDT from water by fish
Authors: HOLDEN A. V.
Published: February 2008

The distribution of DDT in brown trout poisoned by low aqueous concentrations of a labelled form of the insecticide has been studied. A direct‐mount technique for determining the carbon‐14 activity extracted from various organs is described.

The DDT was rapidly removed from the water by the fish and by detritus, and relatively high concentrations were found in all organs and tissues examined. Storage occurs principally in the stomach, pyloric caeca, intestine, spleen, muscle and skin. The concentrations found in lipid extracts from the various organs generally showed much more uniformity than concentrations in terms of unit weight of tissue. It is suggested that the concentration of DDT present in the lipids may determine the toxicity to fish, thus explaining the greater susceptibility to DDT of fish in poor condition or of low fat content. DDT extracted from ovaries and testes indicates the possible danger to reproduction.

The use of static water for fish toxicity tests involving insecticides is criticized.
The infection of strawberry and raspberry fruits by Botrytis cinerea Fr.
Authors: JARVIS W. R.
Published: February 2008

Botrytis cinerea occurs abundantly throughout the year as a saprophyte and facultative parasite on a wide variety of plant materials in raspberry and strawberry plantations. Despite high concentrations of airborne spores at the time of fruit development, relatively few infections have resulted from penetration of fruit surfaces following the germination of spores in drops or films of water, uninfluenced by the presence of necrotic tissues. The majority of fruit infections are initiated from mycelium growing saprophytically in contiguous plant material or from spores germinating in solutions trapped between such material and the fruit surface.

Dry spores of B. cinerea on the surface of strawberry fruits do not readily germinate in a saturated atmosphere but germinate rapidly in a water film. Although ripe and unripe fruits differ markedly in susceptibility, fruit maturity induces only small differences in the rates of spore germination. Field observations suggest that water films generally do not persist on the surface of the fruit long enough for the post‐germination infection process to be completed. Such films, however, may persist much longer when trapped between floral parts, and spores germinating there are able to initiate infections almost as soon as the buds open. The process may be accelerated by the presence of necrotic tissue, for example, in flowers damaged by frost. Mycelium infecting floral parts may subsequently invade the proximal end of both strawberry and raspberry receptacles. This mycelium may remain quiescent until the fruit ripens; consequently infected fruit may escape notice during picking and marketing.

Some methods of supplementing fungicidal control measures by reducing the incidence of sources of infection are suggested.
The cumulative action of insecticides on adult mosquitoes
Authors: HADAWAY A.B. , BARLOW F.
Published: February 2008

DDT, dieldrin, γ‐BHC, malathion, diazinon and Sevin were all cumulative to some extent in their action on adult mosquitoes, Aedes aegypti. Mosquitoes receiving a sublethal dose of each insecticide were more susceptible to it 48 hr. later than were untreated mosquitoes from the same population. The greatest effect was obtained with dieldrin; the least with γ‐BHC.
‘Eyespot’, a foliar disease of bananas caused by Drechslera gigantea (Heald & Wolf) Ito
Authors: MEREDITH D. S.
Published: February 2008

The external symptoms of a hitherto undescribed leaf‐spot disease of young Lacatan bananas are described. The name ‘eyespot’ is suggested since the mature lesion has a white or grey centre and a narrow, well‐defined, brown border. Drechslera gigantea (Heald & Wolf) Ito was consistently isolated from eyespot lesions and, in pathogenicity tests, conidia of the fungus caused typical spots to develop within 48 hr.

Conidia of D. gigantea germinated after 30–60 min. in a film of water on the leaf surface, one to five germ tubes being produced from each terminal cell. After 12 hr., germ tubes were up to 75 μ long and swollen at the tip into appressorium‐like bodies. Penetration of the host occurred within 24 hr. Similar stages in the infection process were observed on naturally infected leaves. Sometimes, one conidium caused two distinct lesions as a result of bipolar germination and infection.

Air‐borne conidia of D. gigantea were caught by means of a Hirst spore trap. They displayed regular diurnal periodicity, being maximal between 08.00 and 14.00 hr. E.S.T. and practically absent at all other times. Conidia were violently discharged under drying conditions. Highest conidium concentrations were recorded after rain. In the vicinity of the trap, the major source of conidia was Bermuda grass (Cynodon dactylon L.) which was bearing zonate eyespot lesions caused by D. gigantea.

This appears to be the first record of D. gigantea in Jamaica. In addition to Musa spp., the grass Anthephora hermaphrodita (L.) Kuntze is now added to Drechsler's host list for D. gigantea.
Experiments on the use of ethyl mercury phosphate and other materials for treating sugar‐beet seed
Authors: BYFORD W. J.
Published: February 2008

Steeping sugar‐beet seed in ethyl mercury phosphate solution controlled Pleospoya betae and increased the emergence of seedlings in the field more than did ‘short‐wet’ fungicide treatments, spraying EMP solution on to the seed, or steeping in other fungicides.
Further studies of green petal and other leafhopper‐transmitted viruses infecting strawberry and clover
Authors: POSNETTE A. F. , ELLENBERGER CHRISTINA E.
Published: February 2008

Strawberry green petal, clover witches' broom, stolbur and Delphinium yellows viruses were distinguished from one another and from aster yellows, tomato big bud (lucerne witches' broom) and cranberry false blossom viruses by vector species, host range, host symptoms and reactions to heat in vivo.

Euscelis plebejus (Fall.) leafhoppers transmitted green petal virus from, but not to, strawberry plants. Aphrodes bicinctus (Schrank) was an efficient vector and is probably chiefly responsible for green petal disease in strawberry crops.

Green petal virus did not protect clover plants from the effects of witches' broom virus, but the latter seemed to interfere with the transmission of green petal virus by E. plebejus. The witches' broom virus also retarded the development of E. plebejus vectors and apparently reduced their longevity. This virus was not transmitted by A. bicinctus.

Strawberry plants did not become infected with stolbur virus, but did with Delphinium yellows virus, which caused a bronze‐leaf‐wilt syndrome indistinguishable from that caused by clover witches' broom virus. Stolbur and Delphinium yellows viruses both killed clover; stolbur was occasionally transmitted by E. plebejus and frequently by A. bicinctus, neither of which transmitted Delphinium yellows. Cuscuta campestris Yunck. transferred Delphinium yellows virus from Vinca rosea L. to strawberry and V. Yosea but not to clover or aster; only a single white clover plant was infected by Macrosteles sexnotatus (Fall.). Delphinium yellows virus was inactivated in V. Yosea plants kept at 42°C. for 3 weeks, whereas green petal virus was not, although virus‐free cuttings were propagated from heat‐treated plants.
Withertip disease of limes (Citrus aurantifolia) in Zanzibar
Authors: WHEELER B. E. J.
Published: February 2008

In field trials aimed at developing a successful control for withertip disease of limes, applications of fungicides containing phenylmercuric salts, copper, captan, zineb and nickel were compared. Of these, the organo‐mercurial fungicides were the most effective. A light mineral oil as a carrier for this type of fungicide proved less satisfactory than water.

Timing of the spraying programme should be determined by two particular periods of flowering—that associated with showers at the end of August and that with the vuli rains (November‐December). These flowering periods provide the greater part of the crop in the following year.

The number of spray applications necessary to obtain good disease control was found to depend mainly on rainfall during periods of new growth. In one trial, however, regular applications every 5th day, irrespective of rainfall, gave good control.
The ameliorating effect of zinc on symptoms of phyllody virus (strawberry green‐petal) in white clover
Authors: CARR A. J. H. , STODDART J. L.
Published: February 2008

Water‐culture experiments with six concentrations of zinc between a trace and 20 p.p.m. showed that the symptoms of clover phyllody were ameliorated by zinc. The proportion of symptomless flower‐heads increased with higher concentration, and when pollinated these set viable, virus‐free seed. Infected plants produced approximately twice as many inflorescences as uninfected plants at each concentration, but the addition of zinc decreased the number produced. Leaf‐bronzing typical of the phyllody syndrome was greater in infected plants and increased with higher concentration, but necrotic spotting attributable to zinc toxicity was more marked in uninfected plants. Zinc at 20 p.p.m. was generally toxic. The dry weight of shoot and root decreased at the higher levels of zinc, and at a lower level with infected than with uninfected plants. Zinc content of root and shoot increased with greater concentrations in the culture solution, being higher in the roots of infected plants than of uninfected ones but less in the shoots. Stolons of infected plants bearing symptomless inflorescences reverted to the full phyllody condition when transplanted into normal soil.

The relationship of zinc to normal metabolic processes in the host, including earlier work on hormone levels, is discussed. It is considered that the technique would be of practical value to the legume breeder.
Some new equipment for routine assessment of levels of soil infestation by the potato‐root eelworm, Heterodera rostochiensis Woll
Authors: FIDLER J. H.
Published: February 2008

In the examination of a soil sample for the cysts of potato‐root eelworm subjective errors are liable to occur at three particular stages of the technique, especially when large numbers of samples are being examined as a routine. Three pieces of equipment have been developed to mechanise these stages as far as practicable: (1) A centrifugal divider was adapted to obtain mechanically a uniform aliquot subsample from the full soil sample taken from the field; (2) A turntable was developed so that if cyst numbers are large the total may be estimated without picking off all the cysts present; (3) A magnetic stirrer was used to ensure that a reliable aliquot subsample is taken from the suspension of eggs for counting in the Fenwick slide. The inherent errors associated with each of these stages of the technique are examined.
Crop protection in the tropics
Authors: KEARNS H. G. H.
Published: February 2008

Address of the President of the Association of Applied Biologists Delivered to the Annual General Meeting on Friday, 5 April 1963
The effect of environment, and nutrition of pathogen and host, in the damping off of seedlings by Rhizoctonia solani
Authors: SHEPHARD M. C. , WOOD R. K. S.
Published: February 2008

Two isolates of Rhizoctonia solani which differed in their pathogenicity toward lettuce and cauliflower seedlings were obtained. Each was highly pathogenic toward one host and almost non‐pathogenic to the other. Mineral nutrition of the host, illumination and temperature had little effect on pathogenicity, although very different types of plants were produced. A resistance that developed rapidly with age depended on adequate nutrition and active growth of the seedlings. The nutrition of the fungus, its vigour, and the quantity of inoculum were important in establishing infection, but did not affect the pathogenicity to resistant hosts. High relative humidity reduced the resistance of cauliflower seedlings to the lettuce isolate and also increased the pathogenicity of the lettuce isolate to this host.

Pathogenicity depended mainly on intrinsic properties of the host and isolate, and environmental factors were rarely of more than secondary importance in determining whether or not an isolate would attack a particular host plant.
Withertip disease of limes (Citrus aurantifolia) in ZanzibarII.
Authors: WHEELER B. E. J. , PICKARD J. A. , MARTIN J. T.
Published: February 2008

Mature leaves from trees of lime (Citrus aurantifolia) given one small‐volume application of phenylmercuric nitrate showed a deposit of 0·68 p.p.m. mercury compared with 3·99 p.p.m. on similar leaves which were completely wetted. Repeated applications of the fungicide resulted in a build‐up of mercury on both mature and young leaves. Small amounts of mercury were found in new shoots which developed after spraying. Assessments of small‐volume spray deposits using Saturn Yellow as a fluorescent tracer showed good correlation with the analytical values.

Lime fruits produced during an intensive spraying programme using small‐volume applications of phenylmercuric nitrate, and harvested 3 months after the last application, showed a mercury content of 0·04 p.p.m., distributed between the peel (65%) and pith (35%). Juices prepared in the laboratory from these fruits and those extracted commercially from fruits similarly sprayed were substantially free from mercury. Fruits picked immediately after one full‐coverage application of phenylmercuric nitrate or acetate showed mercury contents of 0·10‐0·18 p.p.m. The implications of these results are discussed.
Tomato seed germination and emergence at controlled soil‐moisture tensions from 0·5 to 20 cm. mercury
Authors: HACK H. R. B.
Published: February 2008

A method of controlling the tension (hydrostatic head)—and hence soil moisture—in seed emergence tests, using porous ceramic plates, is described. In the compost employed emergence was good at 2 cm. mercury tension but severely retarded at 1 cm. mercury. This small difference in tension was associated with a large difference in the soil pore space occupied by air. Tensions below 1 cm. mercury would be expected in seed boxes watered according to customary practice. The results are discussed in the light of reports on gaseous diffusion in porous media and on gas balance in soil at different tensions. The need for ensuring an adequate distribution of pores large enough to be filled with air at the low tensions found in seed boxes is indicated.
The effect of weather on emergence and take‐off of overwintering Limothrips cerealium Haliday (Thysanoptera)
Authors: LEWIS T.
Published: February 2008

The temperature threshold for take‐off of Limothrips cerealium is 18·4° C., but a temperature‐dependent development period is necessary before thrips are ready to fly in spring. In April and May 1960 this ranged from 4 days at 25° C. to 42 days at 10° C. Thrips hibernating on the warm southern side of trees are therefore ready to fly sooner than those on the cooler northern side.

Overwintering thrips were observed emerging from pine bark and their take‐off was recorded by a suction trap. Most thrips emerged when the sun shone on the bark and they usually took off a few minutes later, after combing and flexing their wings.

Temperature was the most important single factor influencing take‐off: apparent temperature thresholds for take‐off ranged from 14° C., using air temperature, to 19° C., using bark temperature. These arbitrary values, which were only reflexions of the real temperature threshold, indicated the importance of standard procedures for measuring temperatures, and were a guide to expected behaviour in the field. Take‐off was not retarded by temperatures up to 35° C.

Low light intensity reduced take‐off 1–2 hr. before sunset, but in spring the temperature often fell below the take‐off threshold before this. Relative humidity and wind speed were less important, and take‐off occurred at humidities from 27 to 53% and wind speeds from 2·5 to 4·5 m.p.h. Sultry weather was not a necessity for spring flight.
Azobenzene derivatives as seed treatments
Authors: FOX H. M. , GEOGHEGAN M. J. , SILK J. A. , SUMMERS L. A.
Published: February 2008

4‐Amino‐4′‐hydroxyazobenzene and particularly some of its ring‐substituted derivatives are efficient seed protectants for the control of Pythium ultimum on peas. They are also active against Tilletia caries on wheat, but are ineffective against four other seed‐ or soil‐borne pathogenic fungi. A possible mode of action of the compounds is suggested. Mammalian toxicity data for 4‐amino‐4′‐hydroxyazobenzene and its 3′,5′‐dimethyl and 2,3′,5′‐trimethyl homologues are included.
Verticillium wilt of tomatoes—further experiments on the role of pectic and cellulolytic enzymes
Authors: BLACKHURST FRANCES M. , WOOD R. K. S.
Published: February 2008

An isolate of Verticillium albo‐atrum virulent on tomato produced polygalacturonase abundantly in suitable culture media. Secretion was greatly stimulated by pectic substances, and by organic, as compared with inorganic sources of nitrogen. Degradation of polypectate by culture filtrates decreased sharply when only about 25% of available glycosidic linkages had been hydrolysed.

Cellulase (Cx) activity of culture filtrates was relatively much lower and no cellulase (Cx) activity was detected.

The fungus produced pectic and cellulolytic enzymes when grown on sterilized pieces of tomato stem.

Culture filtrates liberated reducing groups from insoluble plant material and there was some evidence that this depended on the activity of pectic enzymes.

Polygalacturonase was strongly adsorbed by plant material but was eluted readily with O·2M‐NaCl.

When dilute solutions of polygalacturonase were taken up by tomato cuttings only a relatively small proportion could be recovered from the tissues by treatments which removed enzyme adsorbed by plant tissue. This indicates inactivation of the enzyme by living pieces of stem, but extracts from healthy and infected stems did not inactivate polygalacturonase in vitro.

Polygalacturonase was detected in extracts from the stems of root‐ and shoot‐inoculated plants. It was shown that the activity in these extracts was of the order to be expected from the activity of filtrates from cultures on media suitable for production of polygalacturonase.

In all respects tested, the material from resistant Loran Blood and susceptible Ailsa Craig plants reacted in the same way with pectic and cellulolytic enzymes.
Some factors affecting the transmission of sugar‐beet mosaic and pea mosaic viruses by Aphis fubue and Myzus persicae
Authors: COCKBAIN A. J. , GIBBS A. J. , HEATHCOTE G. D.
Published: February 2008

Alate Aphis fabae were often less efficient vectors than Myzus persicae of pea mosaic virus and sugar‐beet mosaic virus. Flight‐mature A. fabae rarely transmitted these viruses unless they had either flown (tethered) or fasted for several hours before feeding on infected plants; by contrast, flight‐mature M. persicae transmitted either virus before flying or fasting, though more frequently afterwards. There was little difference in the infectivity of the two species after they had flown and then fed for a short time on infected plants.

Aphids flown for 1–5 hr. and then allowed a short feed on infected plants transmitted only slightly more often than aphids flown for 15 min., but they remained on the host plants longer. After flying for 15–60 min., many A. fabae settled permanently on broad bean plants, and a few on sugar‐beet plants, but most M. persicae flew off after feeding on these plants for a few hours.

Many flight‐mature alatae of both species probed briefly before flying from a plant for the first time; more M. persicae than A. fabae transmitted after such pre‐flight probing on infected plants.

The infectivity of flying or fasting alatae, and fasting apterae, decreased at similar rates. The rate of decrease was accelerated as the temperature rose, and few aphids transmitted after 30 min. at temperatures above 30 °C.

PMV and SBMV, but not henbane mosaic virus, were transmitted more often by alatae than by apterae. The species of plant (broad bean or sugar beet) on which aphids developed did not affect their ability to transmit PMV or SBMV.
The uptake of hexoestrol by the roots of plants and its retention when applied to the foliage as a spray
Authors: GLASCOCK R. F. , HEWITT E. J.
Published: February 2008

Because of possible dangers to health arising from the use of oestrogens on fattening cattle, the uptake of tritium‐labelled hexoestrol by plants through their roots and its retention when applied in a spray has been investigated. Uptake through the roots was between 0·06 and 0·4% of that given, depending on root medium and species; uptake period had little effect. Hexoestrol was strongly adsorbed on the sand in which the plants were grown and much of it was transformed to unidentified compounds both in the nutrient medium and in the plants. The small amounts absorbed through roots were apparently translocated to foliage. When the hexoestrol was applied as a spray from 3 to 70% of it was retained depending on the interval between application and taking of samples, and on whether the leaves remained dry, or were sprayed with water periodically to simulate rain. About half of the hexoestrol applied as a spray was transformed to other chemical forms within a few hours. When the plants were cut the amounts present in later growth were negligible. There appears to be no danger to animal or human health in eating plants grown in soil containing hexoestrol. Although the amounts remaining on plants after surface contamination were appreciable this source is unlikely to be dangerous in practice.
The accuracy of the rating method for determining leaf area
Authors: HUMPHRIES E. C. , FRENCH S. A. W.
Published: February 2008

The errors involved in determining leaf area of intact potato plants by rating, i.e. by visual comparison with pictorial standards, are considered.

The true area was consistently underestimated but, while the error in estimating areas of single leaves may be large, it is only about 7% for the total area of a large sample of leaves.

It is shown that errors may arise from peculiarities in the standard pictures.

The standards increased in size logarithmically but further work is necessary to see if this is the best arrangement.
Factors affecting the growth of carnation plants from shoot apices
Authors: STONE OLWEN M.
Published: February 2008

Carnation plants were grown from shoot apices ranging from 200 μ to 1 mm. in length, derived from plants of different ages, at all times of the year. Tips grew best in small tubes on a simple nutrient medium, supported on wicks of ashless filter paper. The presence of rooting hormone in the medium was essential during the early stages of culture. Rooting was affected by the size of the tips and the time of year at which they were excised. Rooting of tips after heat treatment of the parent plants differed with variety, and virus infection also affected the rooting of some varieties.
The use of baits treated with α‐chloralose to catch wood‐pigeons
Authors: MURTON R. K. , ISAACSON A. J. , WESTWOOD N. J.
Published: February 2008

Wood‐pigeons were induced to take wheat, barley, oats, peas and beans when these were spread on fields where the birds were feeding. When these foods were scattered on pastures in winter (January‐March) they were taken in preference to the pigeons' normal food of clover. These results are discussed in relation to food preferences and the role of a ‘search image’ in the feeding behaviour of the species.

Cereal and pea baits containing 1·5% by weight of α‐chloralose were laid on a variety of feeding grounds used by wood‐pigeons during the periods 27 October 1959 to 21 March 1960 and 4 November 1960 to 18 June 1961. In a total of thirty‐four such trials 1408 birds were narcotized. Of these 57% were wood‐pigeons and 20% were legally protected or game species. Using cereal baits the risk to species other than wood‐pigeons was lowest on pasture, where 74% of the birds caught were wood‐pigeons, 5% were game species and less than 1% were protected birds.

Of the narcotized wood‐pigeons, 81% recovered unharmed, and partridges and pheasants had similar recovery rates. Only 38% of the stock‐doves recovered and the small finches (including house and tree sparrows) also had a low recovery rate of less than 50%. Baits normally disappeared within about I week. In a few cases they persisted for longer periods, the maximum being 31 days. Uneaten baits were lost through settlement in the soil, germination and ploughing operations. Birds were captured throughout the whole period during which bait was available.

Three trials using peas treated with 1·5% by weight of a‐chloralose were conducted between 7 November 1961 to 22 January 1962. Thirty‐nine wood‐pigeons and thirty‐one game birds were narcotized and captured but no small protected birds were affected. The recovery rates of the captured birds were similar to those narcotized by using cereal baits. The method is much cheaper than control by shooting or nest destruction.

The method of using stupefying baits is potentially a valuable means of wood‐pigeon control but further field tests are necessary. Only baits such as peas and beans are at present suitable as these appear to be too large to be eaten by the small protected species.
Toxicological studies on a beetle,Alphitobius laevigatus(F.)
Authors: HEWLETT P. S.
Published: February 2008

A series of experiments was done, in each of which a toxicant solution was applied to the mesoscutella of the beetles, to their hind coxae, and to both sites. An equation derived by Plackett & Hewlett (1952) was used to interpret the results; this equation assumes parallel probit‐log‐dose lines for single applications to the respective sites, and allows for the possibility that the amount of toxicant reaching the site of action is not directly proportional to the dose (here the volume of solution) put on the sites of application; by contrast the equation for similar action considered by Finney (1952) in effect assumes proportionality. Apart from one experiment with allethrin, the former equation fitted the data satisfactorily.

Forn‐valone, the joint action of the doses was interpretable on the assumption that the amount ofn‐valone acting was proportional to the volume of solution raised to the power of 0.76, a value significantly below unity(P< 0·001). The corresponding value for DDT was 0·89, but this was not significantly below unity (P= 0·12). The values for dieldrin and allethrin were 0·99 and 1·04, also not significantly different from unity.
Some effects of pancreatic ribonuclease and kinetin on tomato aucuba mosaic virus
Authors: DAFT M. J.
Published: February 2008

Lesion production by tomato aucuba mosaic virus was inhibited when the surfaces of infected Nicotiana glutinosa leaves were treated with pancreatic ribonuclease. Application of the enzyme shortly after inoculation with the virus produced the greatest effect, When incorporated with the inoculum the inhibitory action of the enzyme was found to depend on the relative concentration of the virus, the concentration of the enzyme and possibly on the enzyme activity.

Floating leaves of N. glutinosa on solutions of kinetin before inoculation with tomato aucuba mosaic virus slightly increased the number of local lesions produced, whereas floating on solutions containing P‐indoleacetic acid decreased the number. These effects could not be attributed to altered leaf ribonuclease activity.

Spraying N. glutinosa leaves 4 days before and 5 days after inoculation significantly increased lesion production. Spraying kinetin on to infected N. tabacum leaves increased the amount of infective virus produced. This stimulatory effect on lesion formation and on virus production is probably linked with the age of the leaf. Treatment with kinetin delayed the ageing of the detached leaves and greatly lessened the movement of cytidine, uridine, uracil and ribonucleic acid to the petiole.
Control of sugar‐beet downy mildew (Peronospora farinosa) by sprays
Authors: BYFORD W. J. , HULL R.
Published: February 2008

No fungicide tested gave more than partial control of sugar‐beet downy mildew in root crops or steckling beds and even frequent spraying beginning shortly after seedling emergence rarely did more than halve the incidence. This degree of control is not adequate for commercial use on root crops, but is helpful on steckling beds in conjunction with other control measures.
Wilt of lucerne caused by species of Verticillium
Authors: HEALE J. B. , ISAAC IVOR
Published: February 2008

All isolates of Verticillium albo‐atrum from lucerne are virulently pathogenic to this host, whereas V. dahliae is only slightly pathogenic. Isolates of both fungi from other crop plants do not produce symptoms when inoculated into lucerne, suggesting a degree of specialization in the ‘lucerne strains’ of V. albo‐atrum and V. dahliae. However, both these strains can infect broad bean, strawberry, Italian clover (Hedy‐sarum coronarium) and pea, while V. albo‐atrum may also attack potatoes and runner beans.

V. albo‐atrum spreads rapidly underground from diseased to healthy lucerne plants, particularly when they are closely planted. Resting mycelium remains viable for 9 months in pieces of moribund lucerne buried 12 in. in soil, for 7 months at 6 in. and for only 5 months at the surface. V. albo‐atrum spreads from buried infected lucerne debris to the adjacent soil and can be re‐isolated for up to 9 months from 12 in. and for 5 months from 6 in. levels. In pot experiments a correlation was found between the speed of symptom development and the number of conidia in contact with the root system.

Isolates of the fungus from lucerne can infect a number of common weeds (Plantago lanceolata, Polygonum persicaria, Sinapis arvensis, Rumex obtusifolius, Solanum nigrum, Papaver rhoeas, Capsella bursa‐pastoris, Senecio vulgaris and Anthemis cotula) and the fungus is still pathogenic to lucerne when re‐isolated.

Field observations in Norfolk show that harvesting machinery may be the carrier of both the initial infection and the later spread throughout the crop. The incidence of disease increases with the age of the stand; a significant decrease of dry‐weight yield of diseased lucerne occurs during the second harvest year: this often necessitates the ploughing‐in of badly wilted crops before they reach their third harvest.
Studies on the chemical control of Phytophthora palmivora (Butl.) Butl. on Theobroma Cacao L. in NigeriaV.
Authors: HISLOP E. C.
Published: February 2008

A pneumatic knapsack sprayer, a motorized shoulder‐mounted mist‐blower and an automatic tractor‐mounted mist‐blower have been compared for efficacy in controlling black‐pod disease of cocoa and for cost of operation. Preliminary evaluation of these machines was carried out using fungicide/dye mixtures applied to artificial paper‐covered pods. Fungicide deposits for different methods of spraying were determined from the simple colorimetric estimation of the dye. On the basis of these tests three blocks of Amazon cocoa were sprayed with cuprous oxide during the black‐pod season of 1962. Both knapsack machines gave good control of the disease but the cost of spraying with the mist‐blower was three times that for the more simple machine. The tractor‐mounted machine was expensive to use and gave poor disease control. It is suggested that the use of mist‐blowers might be economic only in areas where labour is expensive or scarce, and where yields and black‐pod losses are high.
The epidemiology of tomato mosaic
Authors: BROADBENT L. , COOPER A. J.
Published: February 2008

Tomato plants (vars. Moneymaker and Minimonk) inoculated at the cotyledon stage with tomato mosaic virus (TMV) developed about half as much root as did healthy plants, by the time the first trusses were flowering. Although infected plants recovered to some extent, their roots remained 10–25% smaller. Infection at the flowering of the first truss reduced the size of root system by about one‐third after 6 weeks, but the plants then recovered. Infection at later stages of growth did not significantly affect root growth. There was no significant relation between the dry weight of the root system and the fresh weight of the top including fruit.

Moneymaker and Potentate tomato plants, sown in November, March, June and September, showed similar seasonal changes in the volume of fruit produced weekly, whether or not the plants were healthy or infected with TMV. Infected plants always produced less than healthy ones, but the decrease varied with time of year and age of plant, being greatest in spring and in young plants; the decrease remained fairly steady in older plants. The initial period of acute decrease in volume of fruit production was greater when ovary swelling began early in the year than when it began later. Fewer fruits were produced by infected plants than by healthy ones, except during the winter in var. Moneymaker. During the winter and spring, mean fruit size was decreased by TMV, and was unaffected or increased during the summer and autumn, especially in older plants.
The influence of seedling competition on the amount of loose smut (Ustilago nuda (Jens.) Rostr.) appearing in barley crops
Authors: DOLING D. A.
Published: February 2008

A thoroughly mixed seed sample of Herta barley produced different percentages of smutted ears when grown at several centres throughout the country. From an analysis of the data it was concluded that crop density was not a major factor affecting this variation.

The effects of time of sowing, seed size and seed rate on the smut intensity were also examined.

By varying the seed rate, differences in the amount of smut were obtained. An examination of the number of infected and non‐infected plants and tillers established from each 100 seeds sown and of the tillering capacity of infected and non‐infected seedlings at each seed rate showed that the differences in smut intensity were the result of competition for establishment between the two kinds of seedlings.
‘Lyamungu dieback’ of arabica coffee in Tanganyika
Authors: BURDEKIN D. A. , BAKER R. M.
Published: February 2008

Coffee trees suffering from Lyamungu dieback showed restricted vegetative and fruit growth, leading to death. Both chemical and visual estimations of starch reserves in woody tissue demonstrated that affected trees had lower reserves than healthy trees. The starch deficit appears to be a causal factor in the condition. It is suggested that this deficit may be caused by an imbalance between crop and vegetative growth, associated with low soil fertility.
The effect of planting date and spacing on the incidence of groundnut rosette disease and of the vector, Aphis craccivora Koch, at Mokwa, Northern Nigeria
Authors: A'BROOK JOHN
Published: February 2008

At Mokwa in Northern Nigeria early planting and close spacing increased the yield of groundnuts and decreased rosette incidence. With late planting, increasing the plant population reduced both the rosette incidence and the number of aphid‐infested plants. It is suggested that winged Aphis craccivora Koch bring the virus into the crop, and that spacing and planting date affect rosette incidence because of the influence of groundcover on the optomotor landing response of the winged aphids.
Studies on sharp eyespot disease of cereals II. Viability of sclerotia: persistence of the causal fungus, Rhizoctonia solani Kühn
Authors: PITT D.
Published: February 2008

Sclerotia of Rhizoctonia solani survived for long periods in the laboratory. When left undisturbed in the soil, 79% of buried sclerotia survived for a period of 6 months. Sclerotia retained their infectivity towards seedling wheat plants throughout all viability tests.

Sclerotia germinated readily in response to various stimuli and were able to regerminate at least ten times: it is considered that this property enhances their survival value.

Although wheat stem isolates decomposed cellulose in pure culture and competitively colonized certain types of cellulose in soil, they were ineffective in colonizing cereal straws in the soil. The pathogen quickly died out in artificially infested soil and showed only limited survival in naturally infected cereal straw buried in soil. In pot experiments the pathogen persisted parasitically under a number of crops.
Organophosphorous and carbamate insecticides as soil treatments for the control of wireworms
Authors: GRIFFITHS D. C. , BARDNER R.
Published: February 2008

Laboratory methods are described for testing soil insecticides against wireworms, and the results obtained with some organophosphorus and carbamate compounds tried as possible alternatives to chlorinated hydrocarbons are reported. The most promising compounds in the laboratory tests were thionazin, O‐ethyl S‐p‐tolylethylphosphonodithioate (Bayer 38156) and fenthion. These were tested in a small‐plot field trial with cereals, on land severely infested with wireworms: the compounds were applied to the soil as sprays at 2·7 lb./acre active ingredient before the crop was drilled. Fenthion was ineffective, but thionazin and Bayer 38156 each increased yields significantly and the increases were associated with diminished wireworm populations.
Natural mortality of eggs of the black bean aphid, Aphis fabae Scop., on the spindle tree, Euonymus europaeus L
Authors: WAY M. J. , BANKS C. J.
Published: February 2008

Egg mortality of Aphis fabae Scop, ranged from 18 to 73% on individual bushes of Euonymus europaeus L. at different sites in Hertfordshire during the winters of 1958—59 and 1959‐60. Field and laboratory experiments indicated that the average mortality is unlikely to exceed about 40% and is probably relatively unimportant in limiting subsequent increase to pest density. Winter temperatures in. Southern England do not harm eggs except perhaps at hatching time. Some eggs are destroyed by Anthocoridae and by birds. Others either fail to develop, or develop fully but fail to hatch, even when the weather is apparently favourable and natural enemies are absent.
Studies on Septoria on celery seed
Authors: MAUDE R. B.
Published: February 2008

Studies of the relationship between the viability of Septoria on celery seed and the ability of the seed to give rise to infected plants have enabled the effectiveness of various fungicides against celery blight to be readily assessed by tests of treated seed. Seed of differing degrees of infectivity was obtained by storage over a period of 14 months or by various seed disinfection treatments.

The germination of spores derived from infected seeds was determined by streaking them on agar and the viability of the ‘total’ fungus (spores and mycelium within the seed) was assessed by inserting seeds into slits in celery petioles. The ability of the seed to give rise to infected seedlings was determined by sowing the seed on compost in seed boxes and retaining glass covers on the boxes for 14 days after seedling emergence.

Using the three tests concurrently on stored seed it was shown that the decline in the viability of the ‘total’ fungus was similar to that of the spores and was reflected in the decline in seedling infection. It was thus concluded that tests of the viability of spores from infected seed would indicate the ability of such seed to give rise to infected seedlings and that spore germination tests could be used for assessments of the effectiveness of seed treatments.

By this means it was shown that soaking diseased seeds in 0·2% thiram suspension for 24 hr. at 30° C. eliminated infection.