bluuebunny/crossref_metadata_2025 huggingface dataset:
STUDIES OF FLUCTUATIONS IN INSECT POPULATIONS XII. FURTHER EVIDENCE OF PROLONGED LARVAL LIFE IN THE WHEAT‐BLOSSOM MIDGES
Authors: BARNES H. F.
Published: February 2008

Contarinia tritici emerges the same year as the larvae are in the wheat ears and up to 3 years later. Its parasites emerge up to 2 years after the larvae are in the wheat ears, but never the same year. This indicates that the supernumerary generation of C. tritici that occurs on couch grass in August and September may be expected to be free from parasites and so constitutes a dangerous source of replenishment of the pest.

Emergence of Sitodiplosis mosellana can take place after the larvae have been in the soil up to twelve winters. Most of any one year's larvae do not necessarily emerge as midges after one winter, although usually this is so. Any one year's flight is probably a composite one derived from several previous generations of this one‐generation‐a‐year gall midge.
INSECTICIDES FOR PREVENTING BARNACLE SETTLEMENT
Authors: WAUGH G. DUNCAN , HAWES F. B. , WILLIAMS F.
Published: February 2008

During the summer of 1950 experiments were made to test the use of insecticides for preventing the fouling of oyster spat collectors by the barnacle Elminius modestus.

The insecticides used were DDT, BHC (benzene hexachloride‐γ‐isomer) and dieldrin (hexachloro‐epoxy‐octahydro‐dimethano‐naphthalene), made up as 5% solutions and tested on egg‐box collectors and quarry tiles. The tiles were used for frequent observations on settlement.

When the solutions were sprayed on to the surfaces, in sufficient quantity to give a covering of 200 mg./ft.2 of active insecticide, none of them interfered with either barnacle or oyster settlement.

When the test surfaces were dipped in the solutions, DDT and BHC prevented barnacle settlement almost completely, while dieldrin reduced it by approximately 50%. Settlement of Ostrea edulis was also reduced on the treated surfaces.

Urea‐formaldehyde resins made up as varnishes, to which DDT or BHC had been added, were also tested. A varnish incorporating 20% by weight of DDT provided an effective anti‐fouling compound which lasted at least 3 months and completely prevented barnacle settlement.

The possibility of insecticides dissolving into the water and inhibiting barnacle growth on adjacent surfaces is discussed.
ANTIBIOTICS AS SYSTEMIC FUNGICIDES AND BACTERICIDES
Authors: Brian P. W.
Published: February 2008

We have not done a lot, as yet, about systemic fungicides at the Butterwick Research Laboratories, but what we have done has been based on an approach rather different from that of other workers, and may for that reason be of some interest to you.
THE BIO‐ASSAY OF POTATO‐ROOT DIFFUSATE
Authors: FENWICK D. W.
Published: February 2008

The effect of diluting potato‐root diffusate is investigated. It is found that for any given sample the hatching ability is inversely proportional to the logarithm of its dilution and there is, moreover, for each sample a ‘threshold’ value of dilution beyond which it is inactive. The slope of dilution curves for different diffusates are all parallel. Use is made of these relationships in estimating the strength of any given sample.
RESOLUTION OF STRAWBERRY VIRUS COMPLEXES
Authors: PRENTICE I. W.
Published: February 2008

Strawberry virus 4 produces vein chlorosis and necrosis on strawberry (var. Royal Sovereign) and slight chlorotic spotting on wild strawberry (Fragaria vesca L.). No vector is known. Virus 5 produces leaf curling and vein necrosis on Royal Sovereign and F. vesca. It is transmitted by strawberry aphids (Pentatrichopus fragaefolii Cock.) which have fed on an infected plant for 1 hr. or more and persists for about 1 hr. in the vector.

The names strawberry mottle, mild yellow‐edge, crinkle, vein chlorosis and leaf‐curl virus are proposed for strawberry viruses 1, 2, 3, 4 and 5 respectively.
STUDIES IN RUBUS VIRUS DISEASES
Authors: CADMAN C. H.
Published: February 2008

Yellows diseases of raspberry, previously considered to be physiological disorders, have causes, presumably viruses, that are transmitted by grafting. Several can be distinguished by the severity of symptoms produced in different raspberry varieties, but whether they are caused by distinct viruses or by related strains is uncertain. Two, called mild and severe yellows, are thought not to be related to the yellow mosaic and yellows virus described in North America.
THE INFLUENCE OF PLANTING DATE AND MANURING ON THE INCIDENCE OF VIRUS DISEASES IN POTATO CROPS
Authors: BROADBENT L. , GREGORY P. H. , TINSLEY T. W.
Published: February 2008

Field experiments with Majestic potatoes were made over six years at Rothamsted to test the effects of varying date of planting and manuring on the yield of tubers and the incidence of the aphid‐transmitted leaf roll and Y (rugose mosaic) viruses. Yield was increased by early planting, and by all the manures, especially dung. Early planting also usually increased the incidence of virus disease. Different manures had different effects on disease incidence; the average results from all comparisons showed the largest increase in incidence of both viruses from the use of dung; sulphate of ammonia increased the incidence of leaf roll, and muriate of potash that of rugose mosaic. Counts in two years showed that aphid populations were highest on the earlier planted potatoes, and were increased by dung, sulphate of ammonia and superphosphate, but were reduced by muriate of potash.
THE PENETRATION OF THE INSECT CUTICLE BY DDT AND RELATED COMPOUNDS
Authors: ARMSTRONG G. , BRADBURY F. R. , BRITTON H. G.
Published: February 2008

The penetration of pp‐DDT and some related compounds into grain weevils has been studied by a micro‐analytical technique.

Grain weevils were exposed to filter papers, impregnated with the chemical under test, for periods varying from a few hours to several days. The chemical removed by washing the insects with cold methanol, which was not expected to dissolve anything which had penetrated below the wax layer of the epicuticle, was described as being ‘outside’ the insect; that which remained was extracted with ether after grinding the insects with anhydrous sodium sulphate and recorded as being ‘inside’ the insect. By plotting the amounts ‘inside’ and ‘outside’ after varying times of exposure a picture of the rate of penetration of these compounds was obtained.

The results are discussed in relation to similar curves published earlier for isomers of benzene hexachloride. The major difference revealed is the very slow penetration of pp‐DDT compared with γ‐BHC. This is ascribed to the vapour effect of γ‐BHC which has a vapour pressure much greater than that of pp‐DDT.
OBSERVATIONS ON APPLE CANKER
Authors: BYRDE R. J. W. , CROWDY S. H. , ROACH F. A.
Published: February 2008

Sodium pentachlorophenate and phenyl mercury chloride have been tested as eradicant sprays against apple canker. Trials with inoculated shoots showed that neither of these sprays would affect an established leaf‐scar canker. Both chemicals checked sporulation of Nectria galligena on cankers but phenyl mercury chloride was the more effective and reduced sporing up to 18 months after application.

The incidence of leaf‐scar infection was diminished by treatments reducing sporulation, such as spraying with phenyl mercury chloride or the removal of diseased material from the tree. Bordeaux mixture used as a protectant winter spray was ineffective in reducing leaf‐scar infection.
Studies On Plant Growth‐Regulating Substances
Authors: WAIN R. L. , WIGHTMAN F.
Published: February 2008

The physiological activity of all the mono‐, di‐ and trichloro‐phenoxyacetic acids has been investigated using the pea curvature and Avena cylinder tests. The highest activity was shown by the 4‐chloro‐, 2:4‐dichloro‐ and 2:4:5‐trichloro‐ acids, though the 2‐ and 3‐chloro, 2:3‐, 2:5‐ and 3:4:dichloro‐ and the 2:3:4‐trichloro‐ derivatives were appreciably active in both tests. Significant activity was also shown in either one or both tests by the 2:6‐dichloro‐, 2:3:5‐, 2:3:6‐ and 3:4:5‐trichloro‐ acids.

The activity of such compounds is considered in relation to two recent theories which attempt to relate capacity to induce a growth response with the position of substituents in the aromatic ring. It is concluded that neither theory can satisfactorily explain the relative activities of these compounds for all types of growth response.
EXPERIMENTS WITH ROOT CUTTINGS OF BRUSSELS SPROUT
Authors: NORTH C.
Published: February 2008

A technique for the propagation of Brussels sprout by means of root cuttings is described. Adventitious shoots arise exogenously on callus tissue which develops around the base of side roots. Cuttings sometimes rot without forming adventitious shoots, and cuttings which remain sound do not all produce shoots. Rotting may largely be prevented by planting cuttings with the proximal end exposed above the surface of the medium, and by allowing the root portions to dry before planting. Surface sterilization with mercuric chloride controls rotting but reduces bud formation. Individual plants differ in their capacity to form buds on root cuttings, and this difference is carried by the clones derived from them. Portions of root form more buds if cut into several pieces than if planted intact.
Saprophytic Behaviour of Some Cereal Root‐Rot Fungi
Authors: BUTLER F. C.
Published: February 2008

Records are given of the survival of Helminthosporium sativum, Curvularia ramosa and Ophiobolus graminis as saprophytes in infected wheat straw buried in un‐sterilized soil of different nitrate nitrogen content. Ample nitrogen supply prolonged the survival of O. graminis and C. ramosa but shortened that of H. sativum. Both the Australian isolate of H. sativum used for the survival experiment and a Canadian isolate of the fungus were able to utilize nitrate, as well as ammonium and peptone nitrogen; neither isolate required either thiamin or biotin for growth in pure culture. The depressing effect of nitrate nitrogen upon survival of H. sativum is ascribed to its encouragement of competing micro‐organisms also present in the infected straws.
STUDIES ON A CANKER DISEASE OF CYPRESSES IN EAST AFRICA, CAUSED BY MONOCHAETIA UNICORNIS (COOKE & ELLIS) SACC
Authors: JONES D. RUDD
Published: February 2008

A canker disease of cypresses, caused by Monochaetia unicornis, was first observed in Kenya in 1942. Outbreaks appear to have followed a spread from south‐east to north‐west, the direction of the south‐east monsoon, and the disease has now been recorded in nearly all the cypress‐growing areas of Kenya, Tanganyika and Uganda, in Southern Rhodesia and the Union of South Africa. The oldest known infections occurred in 1937.

The fungus grows in the bark and sapwood, forming cankers which spread rapidly up and down the stem or branch, more slowly round, frequently causing girdling. Cankered trees produce large amounts of resin and a periderm may be initiated in advance of the fungus. Infections occur most commonly at main branch crotches, but cankers also start at the tree collar, on the stem and at minor branch crotches.

The fungus exists in nature in three strains having differing levels of virulence, growth rate in culture, size of acervuli and conidia, and retention of viability in conidia. The distribution of one strain appears to be limited by ecological conditions.

Acervuli ripen and conidia are liberated from 3 to 8 weeks after the start of the rains. Infections start during the rains and misty weather, the slimy spores being dispersed for short distances only. Conidia may retain their viability for up to 28 months.

The local spread of the disease in Kenya has been traced and differing levels of virulence east and west of the Great Rift valley, associated with differences of climate, have been observed.

Trees 2 years old are the most susceptible and older trees are only infected in the rapidly growing parts. Cupressus macrocarpa is more susceptible than C. lusitanica, the latter species being heavily infected only where it is growing close to diseased C. tnacrocarpa.

Occlusion of cankers occurs in both species but is more effective in halting the spread of the fungus in C. lusitanica.

It is suggested that the disease originated from a single focus and may represent the mutation of a strain of Monochaetia unicornis parasitic on cypresses from a strain only parasitic on an indigenous host, Juniperus procera. The fungus may, however, have been imported from abroad.
OBSERVATIONS ON FUNGICIDE CONTROL OF WITCHES‘ BROOM, BLACK‐POD AND PINK DISEASE OF THEOBROMA CACAO
Authors: THOROLD C. A.
Published: February 2008

Spraying experiments were started in Trinidad in 1940 and continued in Nigeria in 1950 to determine the control of certain cacao diseases obtainable by relatively frequent applications of copper fungicides, and also to test modified procedures designed to reduce spraying costs.

It was found that a spray applied only to the cropping regions of the trees reduced pod losses, which may include Phytophthora and Diplodia infections in addition to witches' broom disease (Marasmius perniciosus).

Experiments in Trinidad on witches' broom disease showed that monthly applications of 1% Bordeaux mixture reduced the incidence of both vegetative brooms and affected pods. The number of cushion brooms was not reduced; there was an apparent increase associated with spray applications to one particular cacao clone (ICS 4). There was no apparent advantage when the interval between spray applications was reduced to 1 or 2 weeks, because vegetative brooms occurred in spite of such frequent applications. However, if pod losses can be controlled directly, the occurrence of vegetative brooms would be unimportant.

Pink disease (Corticium salmonicolor) was completely controlled by applications of Bordeaux mixture. It appeared that there was at least a 12 months' residual effect from spraying.

Experiments were carried out in Nigeria on the control of black‐pod disease (Phytophthora palmivora), using carbide Bordeaux, prepared by adding solid calcium carbide to 1% copper sulphate solution. Satisfactory disease control was obtained with applications at intervals of 1–4 weeks. Perenox (0.1%) was less effective than carbide Bordeaux. Knapsack spraying failed to protect all pods more than 7 ft. from the ground.

In Fernando Po, where Bordeaux mixture is used for the control of black‐pod disease, two to four applications are made per season. Black‐pod control is almost universal on plantations in Fernando Po, where there are consequently relatively few sources of infection.
THE TRANSMISSION OF PLANT VIRUSES BY BITING INSECTS, WITH PARTICULAR REFERENCE TO COWPEA MOSAIC
Authors: DALE W. T.
Published: February 2008

Experiments on the virus‐vector relationship of the Trinidad cowpea mosaic virus, transmitted by Ceratoma ruficornis, gave the following results: ability to infect decreased with increasing time after ceasing to feed on infected plants, but vectors remained infective for 14 days (much longer than the longevity in vitro of the virus at glasshouse shade temperatures of 23–31°C.); the beetles transmitted more consistently after longer feeding on infected plants, though feeds of under 5 min. made them efficient vectors; the proportion of plants infected increased with the amount of feeding damage on them; fasting the vectors before feeding on infected plants increased voracity but had no effect on their ability to transmit; beetles became infective immediately after feeding on infected plants. Cowpeas were infected by inoculation with macerated infective vectors or with juice regurgitated by vectors. There is no evidence that aphids or other sucking insects can transmit the virus. It seems similar to squash mosaic and turnip yellow mosaic, for vectors of all three viruses probably transmit by regurgitating infective juice during feeding.
QUANTITATIVE STUDIES ON THE TRANSMISSION OF CABBAGE BLACK RING SPOT VIRUS BY MYZUS PERSICAE (SULZ.)
Authors: HAMLYN BRENDA M. G.
Published: February 2008

Factors affecting the transmission of cabbage black ring spot virus by Mysus persicae (Sulz.) were studied quantitatively using the local lesions produced on tobacco leaves. Aphids prevented from feeding for 15 min. or more, before feeding for a few minutes on an infected plant, caused more infections than unfasted aphids. Fasted aphids acquired virus from infected plants in feeding times as short as 10 sec., and infected healthy plants in test‐feeding times of 5 sec. Increasing test‐feeding times to 30 min. increased the numbers of infections. Increasing infection‐ feeding times from 10 sec. to 5 min. had little effect, but increasing to more than 5 min. greatly reduced the number of transmissions. This reduction was partly offset if the aphids were prevented from feeding continuously while on the infected plants. With undisturbed infection‐feeding periods of 15 min. or longer, previously fasted aphids caused no more infections than unfasted aphids.

Infective aphids lost their ability to produce lesions more rapidly when feeding than when fasting.

Winged and wingless aphids were equally efficient vectors.
THE SYSTEMIC INSECTICIDAL ACTION OF SODIUM FLUOROACETATE AND OF THREE PHOSPHORUS COMPOUNDS ON THE EGGS AND LARVAE OF PIERIS BRASSICAE L.
Authors: DAVID W. A. L. , GARDINER B. O. C.
Published: February 2008

Four compounds, bisdimethylaminophosphonous anhydride (anhydride), bis(dimethylamino)fluorophosphine oxide (oxide), diethyl paranitrophenyl phosphate (E600) and sodium fluoroacetate (acetate), previously shown to have systemic insecticidal activity against aphids, have now been tested against the eggs and larvae of Pieris brassicae L.

The anhydride proved to have very little toxic action on Pieris, but the other three compounds showed both contact toxicity and systemic insecticidal action when taken up by the roots of cabbage plants from solution and from soil. The acetate, but more especially the E600, also showed systemic action following application to the leaves.

In all cases the order of decreasing toxicity was E600 > acetate > oxide > anhydride. E600 is the only compound which is outstandingly toxic to Pieris eggs and larvae. It has the added interest that when watered on to the roots of cabbage plants it kills larvae in egg batches on the leaves. Death takes place at the stage when the larvae are biting through the shells. The oxide and acetate proved to be surprisingly innocuous.

Unless it is felt to be too poisonous E600 is worthy of consideration as an insecticide against Pieris eggs and larvae, since it is highly effective as a contact insecticide and also has some systemic action.
THE INFLUENCE OF INFECTION WITH NOSEMA APIS ON THE ACTIVITIES AND LONGEVITY OF THE WORKER HONEYBEE
Authors: HASSANEIN M. H.
Published: February 2008

Infection of the adult worker honeybee with Nosema apis reduces or obviates brood feeding and causes her to commence foraging earlier than a healthy bee. The length of foraging activity and the total length of life of infected bees is reduced.

In colonies infected with N. apis the rate of brood rearing is severely depressed during April, May and June, the degree of depression being proportional to the percentage infection.

Infection decreases during July, August and September, and consequently the rate of brood rearing increases, but the resulting addition in foraging population is usually too late to increase the honey crop.
THE SPREAD OF DISEASES CAUSED BY SPECIES OF VERTICILLIUM
Authors: ISAAC IVOR
Published: February 2008

An investigation has been made of the spread of Verticillium disease of tomato and antirrhinum by root contact between diseased and healthy plants, and by the growth of the fungi through the soil. V. alboatrum and V. Dahliae spread rapidly by root contact, while V. tricorpus, V. nigrescens and V. nubilum showed no appreciable spread. Where the tomato and antirrhinum hosts wilted and died the causal organism was invariably isolated from the soil near the roots of the dead plants, but where the inoculated host harboured species without showing disease symptoms, as in the case of V. tricorpus and V. nubilum in antirrhinum, the parasite was never obtained from the soil. Moreover, these species in antirrhinum, and V. nigrescens and V. nubilum in tomato would appear to be mild pathogens since when they were already well established V. alboatrum was later actually found to enter and parasitize the respective hosts and bring about its own typical disease symptoms.

Spread through the soil in the absence of hosts was tested by the insertion into it of infected wheat grains followed by later attempts to isolate the fungi at varying distances from the point of infection. V. alboatrum, V. Dahliae and V. tricorpus showed little or no growth through the soil, whereas V. nigrescens and V. nubilum spread saprophytically to some extent, though never attaining sufficient concentration to cause appreciable infection of later planted tomatoes.

The conclusion is reached that spread of disease caused by species of Verticillium takes place mainly by root contact, with a rapidity relatively proportional to that of the death of the host. This finding, together with the lack of spread from antirrhinum plants infected with the non‐lethal V. tricorpus and V. nubilum, suggests that the parasites remain in the vascular tracts until the death of the hosts.
FUNGICIDAL ACTIVITY AND CHEMICAL CONSTITUTION
Authors: BYRDE R. J. W. , WOODCOCK D.
Published: February 2008

2:3–Dichloro‐1:4‐naphthahydroquinone and several derivatives were prepared and tested in aqueous acetone solution against four fungi using a spore germination technique. The hydroquinone showed the same order of fungicidal activity as 2:3‐dichloro‐1: 4‐naphthaquinone, but was no less phytotoxic. Whilst the dibenzoyl ester and the dimethyl ether proved virtually inactive, the diacetyl ester was found to be as effective as 2:3‐dichloro‐1:4‐naphthaquinone against Sclerotinia laxa, Botrytis fabae and Cladosporium fulvum, and also less phytotoxic to plum fruitlets and tomato and broad bean foliage. Reduced fungicidal activity was shown when the substance was formulated as an aqueous suspension suitable for field application.

The rates of alkaline hydrolysis of these esters have been determined, and a relationship between ease of hydrolysis and fungicidal activity is apparent. It is suggested that these compounds, whilst not inherently active, are similarly hydrolysed to 2:3‐dichloro‐1:4‐naphthahydroquinone in the presence of a fungal esterase.

* Byrde, R. J. W., Crowdy, S. H. & Woodcock, D., ‘Studies on Systemic Fungicides. III’, Ann. appl. Biol. 40, 152, is regarded as Part I of this series.
THE EFFECTS OF VARYING THE WATER SUPPLY OF PLANTS ON THEIR SUSCEPTIBILITY TO INFECTION WITH VIRUSES
Authors: TINSLEY T. W.
Published: February 2008

Increasing the amount of water supplied to plants before they were inoculated with viruses greatly increased their susceptibility to infection; plants that received unlimited water produced 10 or more times as many local lesions as plants that received only enough to prevent wilting. Susceptibility was increased throughout the year, but the full response occurred in 2 weeks in winter and 4 weeks in summer. Plants that received unlimited water for the 2 weeks immediately preceding inoculation were no more susceptible than those that received it during the previous 2 weeks, although the external appearance of the plants differed at the time of inoculation. Varying water supply after inoculation did not affect the numbers of lesions.

The differences in susceptibility to infection produced by differential watering were decreased, but not abolished, by growing plants under shade or by incorporating a diatomaceous earth in the inoculum.

Increasing water produced plants with larger and more succulent leaves; the cuticular layer was thinner, and the palisade tissue was less regularly arranged than in the plants kept dry. The increased susceptibility caused by an abundant water supply may be at least partly due to these structural differences, which allow the leaf to be damaged more easily when rubbed with inocula and so present more entry points for virus particles.
TRACE‐ELEMENT TOXICITIES IN OAT PLANTS
Authors: HUNTER JAMES G. , VERGNANO ORNELLA
Published: February 2008

Excessive amounts of nickel, cobalt, chromium, copper, zinc, manganese, molybdenum and aluminium in nutrient solutions supplied to oat plants in sand culture produce (a) chlorosis and (b) other symptoms specific to the element involved. The specific symptoms are distinct for each metal, although those of cobalt and nickel might be confused.

The toxic effects of nickel, cobalt, copper, zinc, manganese and molybdenum are associated with high concentrations of the element in the leaf tissue, but this is not always so with chromium and aluminium.

The toxic effects of nickel, chromium, copper and molybdenum are associated with a reduced nitrogen content of the plant. Nickel, cobalt, chromium, zinc and manganese increase the concentration of phosphorus in the tissue whilst aluminium decreases it, probably to a deficiency level.

Aluminium reduces the intensity of toxic symptoms produced by nickel—probably by reducing the uptake of nickel and phosphorus. Copper effectively reduces the leaf necrosis produced by nickel, but not the nickel content of the leaf tissue; it is suggested that one factor in nickel toxicity may be inhibition of one or more functions of copper. The other elements slightly increase chlorosis and some increase necrosis.

The order of activitjl of the elements in producing chlorosis is found to be Ni>Cu>Co>Cr>Zn>Mo>Mn. This order, which is related to that giving yield reduction and is similar to the order of stability of metal complexes, is discussed in relation to induced iron deficiency.
COMPARATIVE PHYSIOLOGICAL STUDIES ON THE GROWTH OF FIELD CROPS
Authors: WATSON D. J. , WATSON MARION A.
Published: February 2008

Infection with beet yellows virus depressed the dry‐matter yield of sugar‐beet plants by decreasing both leaf area and net assimilation rate (N.A.R.). It did not reduce the number of leaves.

The lower N.A.R. of infected plants may occur because photosynthesis is slowed by chlorosis of the leaves or by changes associated with it. Plants infected at the end of June had 30‐50% of their leaf area yellowed from mid‐August. Later infection caused less yellowing. The yellowing almost sufficed to account for the decrease in N.A.R., if yellowed parts of leaves do not photosynthesize. However, the similar diurnal fluctuations of carbohydrate in the laminae of healthy and infected leaves suggests that photosynthesis may not be much slowed by infection; if so, the decrease in N.A.R. indicates a large increase in respiration rate, especially of the root.

The effects of yellows on leaf area and N.A.R. appear to be independent; late‐sown plants suffered a greater reduction of leaf area, but a smaller reduction in N.A.R., than early‐sown plants; similarly treated plants showed the same reduction of leaf area in two successive years, but the decrease in N.A.R. was much greater in the second.

Most of the loss of dry matter was in the root; the dry weight of the petiole (including stem tissue) was also decreased but the dry weight of leaf lamina was little affected.

Yellows greatly increased the reducing sugars in the leaf lamina, and caused smaller increases in sucrose and starch. These effects appeared when the leaves showed only etch symptoms. The increase in starch was greatest at this time, but the effect on sugar content subsequently increased with the development of yellowing.

Yellows reduced the water content, nitrogen content and the arealweight ratio of the leaf lamina. The change in nitrogen content, but not the others, could be accounted for by the rise in carbohydrate.

Yellows had no effect on the water content of petiole and root; it increased the nitrogen content of these parts. It reduced the sucrose content of the root, but the loss of sugar yield was mainly attributable to decreased root weight.

Infection with beet mosaic virus decreased the dry weight of sugar‐beet plants only when nitrogenous fertilizer was applied. As with yellows infection, the loss of dry matter resulted from reductions in both leaf area and N.A.R. Unlike yellows, mosaic depressed the dry weight of leaf lamina, as well as of petiole and root.

Mosaic had no effect on carbohydrate content, water content or arealweight ratio of the leaf lamina, or on water content of petiole and root. It increased the nitrogen content of all parts of plants that received no nitrogenous fertilizer, but not of nitrogen‐treated plants. It slightly increased the sucrose content of the root.

Infection with beet mosaic virus at the end of June caused a 20 yo loss of sugar yield from plants that received nitrogenous fertilizer. Yellows infection of similar plants at the same date reduced the sugar yield by 50%.
EXPERIMENTS ON THE CONTROL OF BEET YELLOWS VIRUS IN SUGAR‐BEET SEED CROPS BY INSECTICIDAL SPRAYS
Authors: HULL R. , GATES L. F.
Published: February 2008

Field experiments made in eastern England between 1943 and 1951 showed that Myzus persicae lived on the stecklings throughout some winters, and that most plants with yellows in transplanted seed crops were from infections that occurred in the steckling bed. A larger proportion of stecklings sown at the end of July or in early August became infected than of those sown about a month later. The incidence of yellows was reduced by nicotine sprays which cleared the stecklings of aphids after autumn migrations had ceased, thus preventing spread of the disease during the winter. A greater reduction was obtained with persistent and systemic organo‐phosphorous insecticides; in one experiment three applications of E 605 reduced incidence to one‐ninth that in unsprayed plots. However, in years when stecklings were exposed to large migrations of aphids, even plots sprayed three times had 78% of the plants with yellows. Although spraying often greatly reduces the incidence of yellows, it is unlikely to give adequate control in years and districts in which many viruliferous aphids move in the autumn. Spraying in September and October was usually more effective than in August.
SYSTEMIC INSECTICIDAL ACTION OF NICOTINE AND CERTAIN OTHER ORGANIC BASES
Authors: DAVID W. A. L. , GARDINER B. O. C.
Published: February 2008

Nicotine and nicotine salts are taken up by the roots of plants from solutions, and when 0.01–0.001 % nicotine is used the plants become toxic to Aphis fabae and to Pieris brassicae larvae and can be shown to contain nicotine. The results with Phaedon cochleariae adults and larvae are less satisfactory. No systemic action is observed when the nicotine is watered on to soil in which plants are growing and no nicotine can be detected in the plants. Apparently the nicotine is decomposed in the soil.

When applied several times to the upper surface of a bean leaf nicotine kills aphids on the underside. There is some evidence that nicotine can be translocated further through the plant following leaf applications, but the toxic action at any distance is very weak in the plants used in the present experiments and can only be produced by frequent applications of rather concentrated nicotine solutions. Leaf absorption and subsequent translocation has not been observed with nicotine salts.

The various organic bases, including some piperidine phosphonites and allied compounds tested, are of very little interest as contact or systemic insecticides against aphids.
BIOASSAY SYSTEMS FOR THE PYRETHRINS: V. EXPERIMENTS WITH A RESISTANT STRAIN OF CALANDRA GRANARIA L.
Authors: BLACKITH R. E.
Published: February 2008

Some principles of testing for resistance in wild and laboratory stocks of insects are discussed, and experiments with Calandra granaria L. are described in which these insects are selected for pyrethrum resistance.

A new method is described of expressing relative tolerances when the relevant regression lines are not parallel, based on the ‘generalized distance’ of Mahalanobis. The method may equally be used for the comparison of two insecticides giving rise to lines of different slope. A limited increase in resistance occurred on selection. Non‐random oscillatory sequences of slopes were observed when the resistant strain was assayed, and regression parameters computed. The nature of these oscillations is considered.
STUDIES ON BEETLES OF THE FAMILY PTINIDAE: VIII. THE INTRINSIC RATE OF INCREASE OF SOME PTINID BEETLES
Authors: HOWE R. W.
Published: February 2008

The results of laboratory studies on nine species of warehouse Ptinid beetles at 25° C. and 70%r.h. are used to calculate by Leslie's methods, the statistic r measuring the intrinsic rate of increase of each species. Ptinus tectus Boield. has the highest value of r—0–38, equivalent to a 39 % weekly increase or tenfold in under 2 months. Four species, Gibbium psylloides (Czemp.), Mezium affine Boield., Stethomezium squamosum Hinton and Trigonogenius globulus Sol., are capable of tenfold increase in 3 months and the remaining four multiply more slowly, either because of a low oviposition rate (Eurostus), high developmental mortality (Niptus), or slow development (Ptinus fur (L.), P. sexpunctatus Panz.).

Generally the intrinsic rate of increase falls with temperature due to lengthening of development and reduction of oviposition, but near the maximum of development it also falls because of high developmental mortality. Niptus has a higher rate of increase at 20° C. than at 25° C. which is close to its developmental maximum. Relative humidity has little effect except at the limits of humidity tolerance, but water must be occasionally available for the adult to drink, or oviposition and thus rate of increase is markedly depressed. Food mainly affects the rate of increase through its effect on developmental speed. Other factors are briefly considered.

The statistic r applies to a population which has a stable age distribution. For Ptinids the stable age population was found by calculation to contain between 5 and 11% of adults, whereas in the warehouse never less than 15% of the population found were adults. In a warehouse actual observed rates of increase reached a value equivalent to r= 0.24 per week over a period of 8 weeks. From observed temperature means and laboratory results a maximum of r= 0.31 was predicted with a mean of 0.19 per week for a year. The value of r obtained using the oviposition rate estimated in the warehouse was 0.1. Warehouse values of r may be below those predicted from laboratory results because oviposition is restricted due to lack of drinking water and often to overcrowding, mortality increased due to disease, parasites, predators, and accidental cannibalism, and developmental speed retarded due to crowding.
THE RAPID DETERMINATION OF THE INTRINSIC RATE OF INCREASE OF AN INSECT POPULATION
Authors: HOWE R. W.
Published: February 2008

The primitive (single oviposition period) method for determining the finite rate of natural increase (Λ) of an insect species which lays all its eggs quickly is described, together with a summary of a more accurate method introduced by P. H. Leslie and L, C. Birch of calculating the infinite (infinitesimal) rate of increase (r) of any species. The parameter r is the natural logarithm of the parameter Λ. Two methods of simplifying this more accurate method are discussed and illustrated by six examples which are used to compare the results given by all four methods.

The first modification of the Leslie‐Birch method provides a means of representing a long oviposition cycle by a single figure so that the final calculation resembles the primitive single period method. The oviposition period is divided into a number of convenient unit periods, and using a table of weighting factors provided, the number of eggs laid in each of these unit periods is converted into the number of eggs required to be laid in the first of these unit periods of oviposition to make an equivalent contribution to the rate of increase. The equivalent oviposition figures for all the unit periods are summed to provide one figure which represents the observed egg number and pattern.

The second modification provides a means of representing the observed egg pattern by a constant rate of oviposition. This requires the same table of weighting factors but also needs a series of charts which are provided. This method usually gives a good answer at the first attempt, whereas the first modification usually requires two trial and error solutions to give an accurate estimate of r and hence of Λ. Two of the examples show how the methods may be used for species for which information is scattered in the published literature. The minimum requirements for estimation of r are information on the length of the developmental cycle, the rate of egg output of adults, mortality of all stages and the sex ratio.
STUDIES ON SYSTEMIC FUNGICIDES
Authors: BYRDE R. J. W. , CROWDY S. H. , WOODCOCK D.
Published: February 2008

A number of mono‐, di‐and trichloro‐β‐naphthols and the corresponding naphthyloxy‐n‐carboxylic acids were prepared. They were tested as systemic fungicides against chocolate spot of broad bean (Vicia faba) caused by Botrytis fabae and as fungicides in vitro by their effect on the germination of spores of Sclerotinia laxa and the growth of the mycelium of Botrytis fabae.

The systemic fungicide tests showed no difference in the activity of the compounds associated with different side chains, though there were slight but significant effects associated with different chlorine substitutions in the naphthalene nucleus. The 3:4‐dichloro‐2‐naphthol derivatives were more effective than the other compounds tested.

Fungicide tests with the 1:3‐dichloro‐2‐naphthol derivatives suggested that there was some increase in toxicity to the spores of Sclerotinia laxa with increasing length of side chain. The effectiveness of the various chlorine‐substituted compounds in suppressing growth of Botrytis fabae was in the following descending order, 1:3:4‐trichloro‐, 1:3‐dichloro‐, 1:4‐dichloro‐and 3:4‐dichloro‐compounds. The concentrations required in agar culture to induce reductions of B. fabae growth comparable to those found in the leaf could reasonably be expected to occur in the bean plants treated with the 2‐naphthyloxyacetic acids at 10 p.p.m.
WHITE ROT (SCLEROTIUM CEPIVORUM) OF ONIONS IN WORCESTERSHIRE WITH SPECIAL REFERENCE TO CONTROL BY SEED TREATMENT WITH CALOMEL
Authors: CROXALL H. E. , SIDWELL R. W. , JENKINS J. E. E.
Published: February 2008

Observations in Worcestershire have shown that heavy losses of salad onions due to white rot may occur on sites which have not been known to carry a previous susceptible crop. Reasons for this are discussed. During five seasons a good control of the disease has been obtained by treating the seed with pure calomel applied with a resin‐alcohol sticker. The treatment also gave some control of damping off of seedlings due to Corticium solani. Broadcasting 4 % calomel dust at 2½‐3 cwt. per acre was less satisfactory in controlling white rot. In one season promising results were obtained with seed treatment of bulb onions.
THE CONTROL OF ONION SMUT (UROCYCTIS CEPULAE) BY SEED TREATMENT
Authors: CROXALL H. E. , HICKMAN C. J.
Published: February 2008

In field trials near Evesham, Worcestershire, a good control of onion smut was obtained by seed treatment with ferbam and 50 % thiram dusts applied with a resin‐potash sticker. A pentachloronitrobenzene compound also gave some control of the disease but reduced emergence. Greenhouse trials confirmed these results, but there was a fall off in control at high levels of infection. Chloranil and calomel were relatively ineffective and two organo mercury compounds caused serious seed injury.
BREEDING PEARS FOR RESISTANCE TO THE PEAR SCAB FUNGUS VENTURIA PIRINA ADERH.
Authors: STANTON W. R.
Published: February 2008

Three clones of Venturia pirina have been tested for their pathogenicity towards forty varieties of cultivated pear. From observations on the reactions of these forty varieties, twelve were selected for differentiating the pathogenicity of sixteen clones of the fungus.

These tests differentiated four main groups of biotypes of V. pirina. Clones isolated from Conference showed wide differences in range of pathogenicity. One isolate from Conference was shown to parasitize six of the most widely grown pears in England: other Conference biotypes had a narrow range.

No variety of pear was found immune to all the isolates. Beurré Giffard was lightly infected by an isolate from Durondeau, but was resistant to all the other isolates tested.
OBSERVATIONS ON THE EFFECT OF GROWTH‐STIMULATING COMPOUNDS ON THE HEALING OF WOUNDS ON APPLE TREES
Authors: CROWDY S. H.
Published: February 2008

Wounds were made at various times of the year on the trunks and large branches of apple trees with a 1 in. bit and treated with a number of organic compounds in lanoline paste. The healing of these wounds was followed through two growing seasons by tracing and measuring the area of exposed wood at different times after wounding.

Callus growth was practically confined to the summer months. Development of callus was improved by applications of lanoline, and the lanoline effect could be further enhanced in the early part of the first growing season following treatment by the addition of certain growth‐stimulating compounds including 4‐chloro‐3:5‐dimethylphenoxyacetic acid and 2:4‐dichlorophenoxyacetic acid. Indolyl‐3‐butyric acid probably also caused some stimulation. After the period of initial stimulation the rate of callusing was approximately the same on treated as on untreated wounds.
EFFECTS OF REPEATED FIELD INJECTIONS OF D‐D MIXTURE AGAINST POTATO‐ROOT EEL‐WORM
Authors: FENWICK D. W. , PETERS B. G. , LIBBEY R. P.
Published: February 2008

Autumn injections of D‐D mixture have been annually repeated for three years on a silt soil at Moulton (Holland, Lincolnshire) and a black fen soil at Prickwillow (Ely, Cambridgeshire), with different results. At Moulton there was an increased yield of tubers each time D‐D was used, with no significant residual effects after the first year, and no marked long‐term effect on the eelworm population. At Prick‐willow D‐D gave an increased yield in the first season only, with no positive residual effects on yield, and an apparent stimulating effect on the eelworm population. At Moulton in 1948 and 1950 (but not in 1949) the cost of the D‐D treatment was heavily outweighed by the value of the resultant increase in crop. However, on the organic soil at Prickwillow D‐D treatment was ineffective in 1949 and 1950 and the eelworm population, initially higher than at Moulton, remained at a level inducing failure of the potato crops.
THE SIGNIFICANCE OF THE LIGHT AND DARK PHASES IN THE PHOTOPERIODIC CONTROL OF DIAPAUSE IN METATETRANYCHUS ULMI KOCH
Authors: LEES A. D.
Published: February 2008

The daily cycle of illumination is one of several agencies which control the onset of diapause in Metatetranychus ulmi. Both light and dark phases in the cycle are concerned in the determination process.

In general, a long light phase tends to suppress and a long dark phase to induce a diapause. In any combination, the path of development is decided by the balance between diapause‐preventing (light phase) and diapause‐inducing (dark phase) stimuli. However, as their effectiveness does not increase linearly with duration, the existing balance changes with the phase duration.

The effectiveness of the light phase in suppressing diapause increases most rapidly between 8 and 16 hr.; that of the dark phase rises very sharply between 8 and 12 hr. Longer dark periods of up to several days duration also induce diapause but are no more effective than a 13 hr. phase. The inclusion in the cycle of very long periods of light or darkness may also influence diapause by reducing the number of complementary phases experienced by the mite during the sensitive period of development.

M. ulmi is highly insensitive to the interruption of effective light and dark phases by short intervals of darkness or light—a further indication of the slow inception of the light‐and dark‐phase reactions.

These findings are discussed in terms of hypothetical mechanism involving cumulative synthesis and removal of some active substance, but the experimental results cannot yet be fully reconciled with a simple hypothesis of this kind.
THE EFFECT OF REPEATED SPRAYING OF INSECTS IN INCREASING THEIR RESISTANCE TO INSECTICIDES
Authors: TATTERSFIELD F. , KERRIDGE JILL R.
Published: February 2008

During the selection of a stock of Drosophila melanogaster for resistance to DDT, in which carbon dioxide was used for purposes of anaesthesis, a sensitivity to this gas developed. The phenomena closely paralleled those shown by the CO2‐sensitive ebony stock isolated by L'Héritier and his co‐workers. An experimental analysis of its effect upon DDT sensitivity was made. It was found that a stock selected for CO2 resistance gave the same probit regression line as the original stock. A CO2‐sensitive stock, whether anaesthetized with nitrogen or carbon dioxide, gave the same regression line at a temperature of 25° C. at which CO2 sensitivity disappeared, or at 15° C. if adjustment to the proportion of deaths in the control was made. The effect of CO2 was therefore to limit the population from which selection is made for DDT resistance, rather than to alter the distribution of DDT resistance within the stock.
THE MUTUAL EFFECT OF RYEGRASS AND CLOVER WHEN GROWN TOGETHER
Authors: MANN HAROLD H. , BARNES T. W.
Published: February 2008

Italian ryegrass and a late‐flowering red clover were grown together, with abundance of water and nutrients for both. It was found that even a small number of ryegrass plants reduced the growth of clover by 30%. This effect varied very little with increasing density of the clover crop.

The presence of clover reduced the ryegrass crop by an amount diminishing as the density of the ryegrass was increased. In a sparse crop of ryegrass, clover reduced the growth of the grass considerably more than did barley under comparable conditions.

There is no evidence of any specific effect of the roots of one plant on the other. When ample nitrogen is available the clover tends to take some that would otherwise be available for the grass and does not provide the grass with additional nitrogen.
HOST ALTERNATION IN APHIS FABAE SCOP.
Authors: KENNEDY J. S. , BOOTH C. O.
Published: February 2008

Experiments on the feeding preferences and relative fecundity of Aphis fabae among leaves of different ages and kinds were extended to the comparison of different forms of the aphid: apterous and alate virginoparae and gynoparae.

All three forms showed a preference for the primary host, Euonymus, over a secondary host, sugar beet, but this preference was strongest in the gynoparae, weaker in the alate virginoparae and weakest in the apterae. The relative fecundity of the aphids on the two kinds of leaf paralleled their feeding preferences most closely in the gynoparae, less so in the alate virginoparae and least in the apterae.

All three forms also showed some preference for growing over mature leaves of the same kind, but this preference was strongest in the apterous virginoparae, weaker in the alate virginoparae and weakest in the gynoparae. The relative fecundity of the aphids on the two ages of leaf paralleled their feeding preferences most closely in the apterae, less so in the alate virginoparae and least in the gynoparae.

The physiological, ecological and evolutionary significance of the results is discussed in the light of the dual discrimination theory of aphid host selection.