摘要:

Resistance of the oat plant to infestation by the frit fly is not correlated with either carbohydrate or silica content. By increasing the number of eggs placed on an oat variety, proved to be resistant in the field, its resistance can be reduced below that of the most susceptible type, the inference being that resistance is indirect and due to some form of plant attractiveness which determines extent of oviposi‐tion. Oviposition studies in the held show that oviposition on susceptible varieties of oats, such as Victory and Star, is three times as great as on resistant types, such as Summer and Spet; selections from crosses between susceptible and resistant types, intermediate in resistance, receive a proportionate number of eggs, resistance being inherited. Some oviposition data for wheat and barley are included. Fly orientation is not controlled by either chemotaxis or hydrotaxis, but is influenced by stereotaxis; negative results have so far been obtained from phototaxis studies. Trie resistance to infestation in the field of twenty‐two named varieties of oats is compared with that of a standard variety; none is so resistant as Summer, while Richland Iowa 411 and Eagle approach Sandford in possessing moderate resistance. The marked difference between Victory and Summer in regard to stem infestation in spring is not extended to the grain infestation, no marked difference being observed. Susceptibility to sterility of grain shows significant differences, and there is an indication that segregation may be transgressive. Late nitrogenous dressings have no effect on extent of either grain infestation or sterility. The recovery capacity of Sandford almost equals that of Gris de Houdan, a good tillering variety. Maize exhibits varietal differences in extent of resistance to attack. The protective effect of D.D.T. is considerable, but not complete.The essential statistical analyses have been lodged with the Librarian of the British Museum. A statement of significance of result means significance at the 1 % point of distribut

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1946.tb06324.x

出版商:Blackwell Publishing Ltd    

年代:1946

数据来源: WILEY

摘要:

Counts of aphides infesting potato crops in north‐west Derbyshire at altitudes between 340 and 1360 ft. were made during the summer of 1945.Mysus persicaewas abundant on almost all crops, and peak figures on some reached over 1500 per 100 lower leaves. In many fields two peaks were noted, one towards the end of July and the second in mid‐September, and in some fields there were still heavy infestations when the haulms died. The number of aphides varied considerably from field to field; sheltered fields were the least infested. In this area in 1945 there was no evidence to support the contention that the altitude and aspect of the field have any influence on the intensity of infestation. Tuber samples from six fields showed that there was a considerable spread of leaf r

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1946.tb06325.x

出版商:Blackwell Publishing Ltd    

年代:1946

数据来源: WILEY

摘要:

Detached potato sprouts have been grown successfully in ammonium and nitrate culture solutions for 5 weeks. The pH and concentration of each solution were such that a similar rate of nitrogen absorption took place from both. The general appearance, increase in fresh and dry weight and the nitrogen distribution in the shoots and roots of sprouts removed at intervals for analysis have been compared. Sprouts, previously grown in nitrate or ammonium culture solutions, have been transferred and grown for 8 days on a minus‐nitrogen culture solution, and the changes in appearance, growth rate and nitrogen distribution followed in a similar manner.The importance of aerating the culture solution, of frequent solution renewal and of an adequate supply of soluble iron for successful solution culture of potato sprouts is stressed.The ammonium sprouts developed more evenly and ultimately more rapidly than the nitrate sprouts. The nitrate sprouts were a lighter green, showed a tendency for the lower leaves to yellow and dry up and, when transferred to the minus‐nitrogen solution, rapidly developed symptoms of nitrogen deficiency. Evidence is presented that, in young potato sprouts, the rate of nitrate reduction and assimilation are a serious limiting factor to the availability of nitrate nitrogen for protein synthesis.Ammonium assimilation takes place actively and mainly in the roots and stem bases. Nitrate assimilation takes place in both shoot and roots, but is more active in the shoot. Absorption of nitrate ions can take place even when a much higher concentration of nitrate ions is present in the root cells than in the external solution. The initial nitrate nitrogen present in the sprouts is not appreciably utilized during culture on ammonium solution.The ammonium shoots as compared with the nitrate shoots have a higher content of total nitrogen, protein nitrogen, non‐protein organic nitrogen, amide and amino‐acid nitrogen, but a lower content of inorganic nitrogen. The nitrate roots as compared with the ammonium roots have a higher content of total nitrogen, protein nitrogen and inorganic nitrogen, but a lower content of non‐protein organic nitrogen, amide and other nitrogen.The higher protein content of the nitrate roots is associated with a higher percentage dry weight and a lower content of ‘other’ nitrogen. The significance of this relationship is discussed.During ammonium culture both asparagine and glutamine accumulate, particularly in the shoot.Evidence is presented that asparagine is the amide primarily concerned in ammonia storage and also that it is formed during nitrate assimilation.Knowledge of the absorption and assimilation of ammonium and nitrate ions by plants is of fundamental importance for an understanding of fertilizer practice, and the present investigation, in which detached potato sprouts have been successfully grown in ammonium and nitrate culture solutions, forms part of a study of

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1946.tb06326.x

出版商:Blackwell Publishing Ltd    

年代:1946

数据来源: WILEY

摘要:

The relative toxicity to the flour beetle,Tribolium castaneumHerbst, of films of 1‐6% w/v total pyrethrins or 0.8% w/v technical D.D.T. in Shell Oil P31 sprayed on to some common building materials has been investigated. Beetles were exposed on films for 6 days, starting 24 hr. after application of the insecticide, and relatively low kills were recorded even with deposits two to three times as heavy as those normally used in practice. The materials could be placed in order, according to the toxicities of the films formed on them, as follows:1.6 % pyrethrins 0.8 % D.D.T.1Rough deal, sacking Rough deal, limewashed brick Films more toxic2Fletton brick Fletton brick3Wallboard4Cement, cement‐sand, limewashed brick ceiling board, Cement, cement‐sand Films less toxicAn experiment carried out under practical conditions confirmed the low toxicities of films formed on limewash and wood.The effect has also been investigated of pretreating bricks with six substances, which might influence the rate of sorption of the oily insecticide into the substrate. Pretreatment with polyvinyl alcohol, starch paste, size, and waterglass greatly increased the toxicity of pyrethrum films on brick, but water and calcium chloride failed to do so. The toxicity of a pyrethrum film on cement‐sand blocks was also very greatly increased by a pretreatment with starc

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1946.tb06327.x

出版商:Blackwell Publishing Ltd    

年代:1946

数据来源: WILEY

摘要:

A stowage in a London granary containing 500 tons of Manitoba wheat was sprayed with 0.8 % w/v pyrethrins in Shell oil P31, in an attempt to control an Ephestia elutella infestation. The mean deposit on the surface of the wheat was 1‐5 mg./sq.cm., of which one‐sixth was due to the settling of mist.All the moths in the stowage at the time of spraying, estimated at 68,900, were killed or fatally affected within 24 hr., and those which emerged later, estimated at 7500, were killed by the insecticidal film.The spray was not observed to have any marked effect on the size of the migrating larval populat

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1946.tb06328.x

出版商:Blackwell Publishing Ltd    

年代:1946

数据来源: WILEY

摘要:

The toxicity of ethylene dibromide toCalandra oryzaeandTriboliumspecies was determined in the absence and presence of grain. Its toxicity by oral administration was studied on rats and guinea‐pigs. The quality of bread baked from flour fumigated with ethylene dibromide was found to be unimpaired. The germination capacity of wheat, barley, maize, peas and beans was not adversely affected by fumigation with ethylene dibromide. The results of large‐scale fumigations are reported and the conditions discussed under which ethylene dibromide can be used advantageously as a fumigant for grain and seed stores on a commercial scale. A concentration of 50‐75 g./m.2was found satisfa

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1946.tb06329.x

出版商:Blackwell Publishing Ltd    

年代:1946

数据来源: WILEY

摘要:

Under certain conditions dinitro‐o‐cresol (D.N.C.) is easily decomposed to reduction products devoid of ovicidal properties to eggs of apple sucker, winter moth and fruit tree red spider.Because of this, corrosion of containers in which D.N.C. products are stored may be accompanied by a deterioration of the product.At the concentration normally used in winter washes (0.1%), D.N.C. is equally effective whether present as cresol or as the sodium cresylate against eggs of apple sucker and of winter modi, but against eggs of fruit tree red spider the cresol is more ovicidal than the cresyl

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1946.tb06330.x

出版商:Blackwell Publishing Ltd    

年代:1946

数据来源: WILEY

摘要:

Determinations have been made of the copper dissolved from pure copper compounds by water, by a standardized solution of the exudate ofNeurospora sitophilaspores, by standard solutions of malic and succinic acids and their sodium salts, and by glycine and mannitol.The results compared with the known fungicidal performances of the copper compounds show that the amounts of copper yielded to water and to the standardized spore extract or glycine solution provide an indication of fungicidal properties.Although soluble copper in excess of that dissolved by water can only appear from alkaline Bordeaux deposit by complex ion formation, results show that this is not necessarily the only means by which copper can dissolve from other copper compounds.In a chemical investigation of the exudate ofN. sitophilaspores, mannitol, succinate and fumarate have been isolated. None of these materials can dissolve an appreciable amount of copper from alkaline Bordeaux deposit. Malate, found by other workers to be a constituent of the exudate of N. sitophila spores cultured on potato dextrose agar, has not been detected in such a solution from spores grown on malt agar. The quantity of mannitol in spore exudate has been shown to depend on the nutrient medium on which the fungus is grown.

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1946.tb06331.x

出版商:Blackwell Publishing Ltd    

年代:1946

数据来源: WILEY

摘要:

In trials at Beaford, north Devon, and at Galmpton, south Devon, in 1945. proprietary preparations of copper oxychloride, cuprous oxide, and cuprammonium, used at low‐copper dosage (0.063 % Cu), were compared with Bordeaux mixture at the same and at higher dosages for the control of potato blight under two commonly recurring conditions of disease incidence, respectively early and late, which were closely defined by foliage decay curves.All the copper fungicides were tested with and without added adhesive of caseinate‐rosin soap type, and twosulphurfungicides: lime sulphur (1 in 50) and Dithane 14 (1 in 200) with zinc sulphate and lime, were also included.The trials were made on four‐times replicated plots at both centres; special precautions were taken to avoid confusion of the observations by concurrent mineral deficiency and virus disorders; and the treatments were compared by three criteria: (1) direct foliage protection, (2) spray retention and (3) indirect effect on yield. The number of spray applications was reduced to a minimum to avoid masking the superiority of the better treatments, and timed as nearly as possible for maximum effect in relation to weather conditions. Thus two applications were given at Galmpton and three at Beaford.None of the proprietary copper fungicides used at low‐copper dosage, with or without added adhesive, equalled plain (4.5.40) Bordeaux mixture in spray retention or direct protective effect; and none gave any significantly better protection than Bordeaux mixture at correspondingly reduced copper dosage (1.11/2.40).With the few well‐timed and thorough sprayings given, however, the 1% Bordeaux mixture itself gave almost sufficient protection for the production of a full crop, and the trials indicated horticultural conditions under which low‐copper fungicides can be used with success, while pointing to the important factor of safety secured by using 1 % Bordeaux mixture in routine agricultural practice.Both of the sulphur fungicides were less effective than i % Borde

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1946.tb06332.x

出版商:Blackwell Publishing Ltd    

年代:1946

数据来源: WILEY

摘要:

Trials in 1945 confirmed earlier work on the efficacy of mercurous chloride (calomel) for the control of Sclerotium cepivorum in spring‐sown onions. The application of 1 lb. 4% calomel dust to 50 yd. of seed drill at sowing time gave sufficiently good control of the disease in salad onions. Broadcast application of 1 oz. 4% calomel dust per sq.yd. before sowing was less effective but promising. Post‐emergence application of the dust was useless. In autumn sowings, seed‐drill treatment at 1 lb./so yd. controlled the disease in the following spring, but caused severe retardation and loss of crop.Onion seedlings raised in heat and dipped in an aqueous paste of calomel dust before transplanting showed a high degree of resistance to a severe attack. Similar treatment of shallot bulbs was also effective. In both cases, the treatment substantially increased the yield and somewhat reduced storage losses.Leek seedlings transplanted into dibber holes did not develop the di

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1946.tb06333.x

出版商:Blackwell Publishing Ltd    

年代:1946

数据来源: WILEY