摘要:

Summary.Inoculation by leaf‐mutilation with the foliage of normal potatoes produced no disease in tomato. Nine varieties of potato were tested.Similar inoculation with foliage of mosaic potatoes produced a characteristic disease in tomato. Five varieties of potato were used, of which three had been tested in the experiments with normal foliage.The characters of the disease are described. It is transmissible back to potato again and to other solanaceous plants. The virus is filterable, is still infectious after high dilution of the extracted juice, and remains active on keeping for several months. It is less resistant to heat and alcohol than ordinary tobacco mosaic.The disease resembles closely the spot‐necrosis disease described by Johnson as obtained by inoculation of tobacco with foliage of normal potatoes, the chief difference being the greater resistance of the potato mosaics here described.It is probable that there exist several strains, differing in resistance, of the virus causing mosaic in the pot

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1928.tb07774.x

出版商:Blackwell Publishing Ltd    

年代:1928

数据来源: WILEY

摘要:

Summary.1 “Breaking” in Tulips is infectious and can be induced by bringing the internal tissue of a normal bulb in contact with tissue from a “broken” bulb during the resting stage.2 The degree of “breaking” appears to be proportional to the amount of infected tissue introduced.3 The phenomenon of “parrotting” has appeared in the “broken” flowers from bulbs infected with a small amount of “broken” tissue.4 Injections of filtrate from “broken” tissue

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1928.tb07775.x

出版商:Blackwell Publishing Ltd    

年代:1928

数据来源: WILEY

摘要:

Summary.1 A summary is given of the history of the Bermuda Easter lily (Lilium longiflorumvar.eximiumBaker), known to the trade as “Lilium Harrisii.”2 It is known that about 1893 “a peculiar sickness” appeared in the lily fields of Bermuda, which caused a very marked decline in the yearly amount of bulbs exported from the Colony.3 Subsequent to 1919 a resuscitation of the industry has taken place, and especially in recent years, when the chief cause of its failure has been ascertained.4 A summary of the methods of cultivation in Bermuda is given.5 Theories as to the cause of the disease were put forward by Woods, Bishop, and others. It is shown that there were two types of disease, one resembling a mosaic, the other characterised principally by very marked stunting and downward curling of the leaves. The latter is here dealt with.6 Photographs taken in the United States Department of Agriculture greenhouse at Washington in 1915 show clearly examples of the disease. The disease came prominently to the notice of the writer in 1925 when certain aspects of it suggested that it was a virus disease. It was called “yellow flat” by the grower who first observed it.7 The general appearance of a plant grown from an infected bulb is a flat rosette or cylinder. The leaves are very markedly curled downwards and are slightly chlorotic in colour, but without streaks or spots.8 In current season infection the leaves which are mature at the time of infection do not show the symptoms. The young leaves show considerable twisting besides curling.9 Plants from affected bulbs do not show the symptoms till about 4 weeks after coming above ground.10 Transmission experiments are described in which positive results were secured by the use ofAphis gossypiiGlover. Experiments with the following were unsuccessful: Aphis Ogilviei Theob., MacrosiphumgeiKoch.,Neotoxoptera violaePerg., andPseudococcus citriRisso. Attempts at mechanical transfer were also unsuccessful. There is no evidence that the disease is carried in the soil.11 Aphis gossypiiis described. Its biology is discussed. It is parasitised byLysiphlebius (Aphidius) testaceipesCress, and attacked bycertain Coccinellids, larvae of Syrphids, etc.12 Spread of the disease takes place mainly early in the season.Affected plants occur in patches in the fields, the average number of infected plants round a bulb‐infected plant being about 15.It appears that the disease is transmitted to the scales and side shoots of affected plants.Affected plants begin to die down about flowering time, about two months before healthy plants.The root system is affected and is attacked by secondary organisms, fungi and the bulb mite.Bulbs from affected plants are flat, small and compact, and resemble bulbs of poor types ofLilium longifiorum.There is a marked tendency to splitting of the bulbs, so that in successive years smaller and smaller bulbs are produced. Amongst weeds or in shady situations the affected plants are not so markedly stunted.Plants from affected bulbs seldom produce flowers. In current season infection the number of flowers is considerably reduced, the flowers twisted and blistered and the pedicels turned stiffly downwards.1 In the writer's opinion recovery from the disease never occurs.2 At temperatures of about 70° F., under greenhouse conditions, the internodes are often lengthened and the leaves twisted rather than curled.3 The disease has been observed on “Lilium formosum” and “Lilium giganteum” and apparently occurs in Japan. It is apparently not connected with any virus diseases of other plants occurring in Bermuda.4 Similar symptoms brought about by other causes are described.5 The disease was probably introduced into Bermuda from Japan about 1893, either direct or via the United States.6 The means of control recommended are roguing, spraying with contact insecticides, and clean cultivation.The official inspection carried out by the Government since 1925 has already reduced the disease to a practically negligible quantity.19. The disease is compared with other virus diseases. It is apparently the f

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1928.tb07776.x

出版商:Blackwell Publishing Ltd    

年代:1928

数据来源: WILEY

摘要:

Summary.1 In the present investigation necrosis of the tubers was found to be due to two distinct diseases: (1) Sprain or Internal Rust Spot, and (2) a disease hitherto unrecorded, which has been named Corky Bacteriosis of the xylem. The former is much the more important and accounts for 98 per cent. of the tissue destruction.2 In Sprain the tissue attacked is the parenchyma both within and without the vascular ring. The lesions vary greatly in form and may consist of spots, arcs, streaks or irregular blotches. The larger lesions are generally hollow in the centre.3 The histological structure of the lesions of Sprain varies slightly according to whether these occur in the starch‐packed cortical tissue or in the pith where the cells are less densely filled with starch, but in either case, is characteristic. A feature of the spots is that they are more or less completely invested with a zone of cork the inner layers of which are suberised.4 The soil on which. Sprain occurs in a virulent form is a light sandy loam deficient in organic matter and one on which potatoes scab severely.5 The disease is apparently slight when the crop is lifted but develops rapidly and continuously during storage.6 Infection of the crop arises mainly from contaminated soil and not from affected seed.7 The causative organism of Sprain has been isolated and typical spots of the disease have been reproduced by inoculation with it. It consists of a very short Bacterium, which, being new to the literature, has been namedBacterium rubefaciens.8 There is little evidence that this organism enters the fully formed tuber through its skin, and isolated spots which have no apparent connection with the peridenn are a feature of the disease. It is suggested that the organisms enter at a very early stage through the stomata or lenticels of the tuber‐bearing stolon, remaining quiescent in the water‐filled intercellular spaces of the tuber and becoming active only when the latter ripens.9 In potatoes affected with Sprain a certain necrosis of the xylem vessels may occur but may easily be overlooked. This Tracheomycosis is essentially different from that of Corky Bacteriosis.10 Corky Bacteriosis produces a browning and lignification of the vascular ring macroscopically resembling the Ring Bacteriosis ofB. solanacearum.11 It is essentially a disease of the xylem vessels which thereby become closely invested with a thick layer of suberised cork.12 Corky Bacteriosis is transmitted from the mother tuber to its progeny by way of the stolons. It is also contracted from infected soil apparently by infection of the stolon or the stolon end of the tuber.13 The causative organism of this disease has been isolated and the disease reproduced by inoculation. The organism being new to the literatur

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1928.tb07777.x

出版商:Blackwell Publishing Ltd    

年代:1928

数据来源: WILEY

摘要:

Summary.1 The viability of the chlamydospores ofV. avenaeandU. levishas been under investigation since 1925. Samples of spores were tested dating back to 1921. The results are expressed in terms of percentage germination. Tests were carried out for the most part on 2 per cent. cane‐sugar solution or on an extract made from the pales of oats.2 Samples ofU. levisshowed a short “after ripening” period. They reached a maximum germination figure about two months after harvest and showed no loss in viability during a period of 2 to 21/2 years. Some samples were viable after 51/2 years.3 Panicles ofU. avenaecollected soon after exsertion yielded immature spores which quickly lost their viability. Mature samples, collected by covering the panicles with pollen‐proof bags, showed only a slight loss in viability after nearly 2 years in storage.4 The influence on viability of several methods of storage was investigated.5 The data emphasise the importance of maturity as a critical factor in the viability of samples. Divergent results obtained with the same species from time to time are probably to be explained by differences in the maturity and age of the samples tested.6 The significance of the results in connection with the different methods of contamination and infection current in the two species of oa

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1928.tb07778.x

出版商:Blackwell Publishing Ltd    

年代:1928

数据来源: WILEY

摘要:

Summary.The autocatalytic equation in the form logx/(a ‐ x) =K (t‐t1) may be used to express closely the changes which occur during growth.The constantk, as given byK = ka, is not a constant which is independent of environmental conditions.The changes in growth may be more suitably expressed by means of the equationdx/dt= (k1+ k2x) (a‐x). In this casek1may be regarded as a constant, dependent upon external conditions, whilek2is a measure of the internal factors governing the growth proc

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1928.tb07779.x

出版商:Blackwell Publishing Ltd    

年代:1928

数据来源: WILEY

摘要:

Summary.An examination of the various theories put forward to account for the fungicidal action of sulphur when applied, not to the plant or fungus, but to a heated surface, has been carried out by chemical methods, and it is concluded:1 That, since the volatile agent is capable of passing a glass‐wool filter maintained at the temperature of the heated surface, it is gaseous in character.2 That the removal of the volatile agent by passage through a cooled glass‐wool filter is proof that it is neither sulphur dioxide nor hydrogen sulphide but is elementary sulphur.3 That the condensation of sulphur volatilised from the heated surface appears sufficient to account for the reactions ascribed to particulat

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1928.tb07780.x

出版商:Blackwell Publishing Ltd    

年代:1928

数据来源: WILEY

摘要:

Summary.1 Considerable diversity of opinion has existed regarding the practicability of controlling plant parasitic nematodes by means of granular calcium cyanide.2 Previous experiments with this substance have invariably been directed against eelworms of the genusHeterodera.3 The experiments described in this paper were carried out in South Devon and in the Isles of Scilly and with the exception of one withHeterodera radicicola, in tomato, relate toTylenchus dipsaci, in narcissus.4 Doses of granular calcium cyanide, ranging from 300 lbs. to 2000 lbs. per acre, were employed under various conditions. Only with doses of from 1500 lbs. to 2000 lbs. per acre was any real indication of satisfactory control ofT. dipsaciobtained, whileH. radicicolaremained unaffected by similar doses.5 In the opinion of the writers the successful use of granular calcium cyanide for the control of plant parasitic nematodes, on a commercial scale, is not possible under conditions pertaining to this country. At the same time, where expense is of no account, small areas of soil may be rid of nematodes by means of exceedingly heavy doses of the

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1928.tb07781.x

出版商:Blackwell Publishing Ltd    

年代:1928

数据来源: WILEY

摘要:

Summary.1 A convenient technique for experiments with insecticides for biting insects is described.2 The silicofluorides of sodium, potassium, aluminium and calcium, used in the form of spray‐fluids, showed considerable toxicity to young larvae of several species of moths. The degree of resistance varies with different species and is greater with older larvae. Considerable, but irregular, injury to foliage was noted, and much further work is required to establish the conditions under which these compounds could be safely used.3 Foliage sprayed with extracts of certain tropical plants is extremely repellent to young larvae. Even with high dilutions of the extracts, the foliage remained uneaten and the larvae eventually died of starvation.4 A short review of some recent work on laboratory experiments with non‐arsenical insecticides for biting insec

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1928.tb07782.x

出版商:Blackwell Publishing Ltd    

年代:1928

数据来源: WILEY

摘要:

Summary.Helophorus rugosusOl. andHelophorus porculusBedel, have caused serious damage to late sown white turnips in several cases in the east of England during the last few years.A case in which the growing points of white turnips (planted out for seed growing) were eaten out by the larvae is recorded.Swedes and rape are damaged by these pests but not to the same extent as white turnips.Kale and cabbages are only slightly damaged.Lettuces were seriously damaged in Surrey in 1924.One case of an attack on beans byH. rugosuswas also noticed. Most of the damage is caused by the larvae which gnaw or tunnel into the “bulb” of the turnip as well as feeding on the developing leaves. The adults also feed on the leaves.Eggs are probably laid in August and the larvae live from August until April or May.Pupation takes place in April or May and pupae live about three weeks.Adults were found from May until the following March.Descriptions of the larval, pupal and adult stages are given.Late sowing and frequent cruciferous crops appear to predispose plants to atta

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1928.tb07783.x

出版商:Blackwell Publishing Ltd    

年代:1928

数据来源: WILEY