摘要:

SUMMARYThe joint actions of pairs of like and unlike toxicants have been investigated. Four pairs of like toxicants were selected, 4,6‐dinitro‐2‐sec‐butylphenol and 4,6‐dinitro‐2‐n‐butylphenol, 2‐n‐valeryl‐I,3‐indandione (n‐valone) and 2‐n‐butyryl‐I,3‐indan‐dione, DDT and 2,2′‐bis(p‐fluoropheny1)‐I,I,I‐trichloroethane, and dieldrin and endrin. Six pairs of unlike toxicants were formed by taking the first‐mentioned of each like pair and using them in all possible combinations of two. Beetles were dosed topically with the toxicants dissolved in non‐volatile oil, and each pair of toxicants was used in a series of experiments, with the proportions of the toxicants varied in respective tests.Broadly speaking the results were clear, though quantitatively they were less regular than had been hoped. The toxicants of the mixtures relative to their components were measured primarily by a quantityJderived in theoretical investigations (Hewlett&Plackett, 1959). Values of η estimated in preceding work were used with the relationJ=λ/η to calculate estimates of a parameter λ, measuring the similarity of the actions (λ= o for complete dissimilarity, λ∼ I for complete similarity). For the pairs of like toxicants it was found that λ∼ I. For combinations ofsec‐butyl‐dinitrophenol orn‐valone with DDT or dieldrin, λ ranged from 0·18 to 0·30. For DDT with dieldrin λ∼ 0·81. Forsec‐butyl‐dinitrophenol withn‐valone λ∼ 1·00.Generally λ was greater the greater the chemical resemblance between the members of the pairs of toxicants. The high value of λ for sec‐butyl‐dinitrophenol withn‐valone is explained by the probability that the latter exists as an enol, implying a considerable resemblance to the former. However, the dinitrophenol stimulates the oxygen consumption of the beetle whereasn‐valone does not (Gostick, 1961), suggestin

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1963.tb03759.x

出版商:Blackwell Publishing Ltd    

年代:1963

数据来源: WILEY

摘要:

SUMMARYWheat seedlings absorb γ‐BHC freely when grown with their roots in a saturated water solution of the insecticide but less than 10 % of the γ‐BHC applied as a seed dressing finds its way into the plants from treated seed grown in compost. About the same proportion of the dressing is absorbed by cabbage seedlings grown from treated seeds, although the usual rate of application is higher in this case. The brassica seems better able than wheat to absorb the insecticide, with the result that concentration of γ‐BHC expressed as μg./g. fresh weight is greater and it is maintained for longer in cabbage than in wheat.The rate of loss of γ‐BHC from soil is shown to be slow compared with the expected life of a seed dressing.Phytotoxic damage to wheat seedlings grown from seed dressed at 1000 p.p.m. γ‐BHC was evident when they were planted in sand but not in compost. Particle size of γ‐BHC in the dressing appeared to be without effec

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1963.tb03760.x

出版商:Blackwell Publishing Ltd    

年代:1963

数据来源: WILEY

摘要:

SUMMARYTo evaluate the relative importance and possible interrelationships of insect, fungus, and nematode injury to the deterioration of roots of alsike clover plants,Trifolium hybridumL., heptachlor, chloropicrin, and ethylene dibromide were applied singly and in combinations to the soil prior to seeding. The most effective treatment was an insecticide plus a soil fumigant (heptachlor plus chloropicrin or ethylene dibromide), which improved the uniformity of stand, plant height and flowering, and reduced the density of weeds. In the second year this treatment greatly increased plant survival and yields of forage. All the plants died in the untreated control plots during the third year of the experiment.There was a significant relationship between the occurrence of vascular decay and the incidence of injury by the clover root curculio,Sitona hispidula(Fabr.). There was a less marked relationship between insect injury and cortical decay; but no apparent relationship between insect injury and rootlet rot. Although root lesion nematode,Pratylenchussp., was present, no direct relationship between nematode injury and root rots was established.The fungi most frequently isolated from alsike clover roots wereFusarium oxysporumSchl. sensu Snyd. and Han., a species ofPyrenochaetaand an unidentified fungus.Verticillium dahliaeKleb. was also present. Tests withF. oxysporum, thePyrenochaetasp., andV. dahliaeconfirmed their pathogenicity on alsike clover roots. In laboratory tests, plants with severe rootlet rot rapidly regenerated feeder rootlets in the presence of adequate soil moisture.

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1963.tb03761.x

出版商:Blackwell Publishing Ltd    

年代:1963

数据来源: WILEY

摘要:

SUMMARYIn transverse sections of cacao stems, 164 of 345 stylets ofPlanococcoides(=Pseudo‐coccus) njalensiswere seen to end in the phloem. Passage through the cortex was intra‐cellular and the stylets entered the phloem by avoiding the peripheral blocks of sclerenchyma. Stylets ofFerrisiana virgata, which transmits cacao viruses less readily than P.njalensis, were also seen in the phloem, but less often.Phenococcus madeiriensis, which is not a vector of cacao viruses, fed differently; of the few stylets seen in sections of stems none ended in the phloem, and, though its stylets are long enough to reach this tissue, they did not extrude for the full length when the mealybugs were fed on a

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1963.tb03762.x

出版商:Blackwell Publishing Ltd    

年代:1963

数据来源: WILEY

摘要:

SUMMARYLesion production by tomato aucuba mosaic virus was inhibited when the surfaces of infectedNicotiana glutinosaleaves 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 ofN. glutinosaon 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.SprayingN. glutinosaleaves 4 days before and 5 days after inoculation significantly increased lesion production. Spraying kinetin on to infected N.tabacumleaves 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 petiol

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1963.tb03763.x

出版商:Blackwell Publishing Ltd    

年代:1963

数据来源: WILEY

摘要:

SUMMARYSugar‐beet mild yellowing virus (SBMYV) was much more common than beet yellows virus (SBYV) in beet in south‐eastern England during 1961 and 1962. SBYV strains and strain‐mixtures, typical of those in East Anglia between 1958 and 1961, decreased sugar yield of a commercial sugar‐beet variety inoculated in the field slightly more than did SBMYV isolates. Simultaneous inoculation with SBYV and SBMYV decreased yield more than did either virus alone. SBMYV probably caused about three times as much sugar loss as SBYV in England during 1961 and about ten times as much during 1962.Aphis fabaeScop. did not transmit SBMYV from sugar beet to sugar beet or toClaytonia perfoliataand this aphid seems not to spread SBMYV in the field. The surveys of 1955‐62 showed that SBW is common in most years only in parts of Essex and Suffolk; it is suggested that the main overwintering sources of SBYV were confined to those areas, whereBeta maritimais probably an important source of SBW. The sources of SBMYV were probably very much more widespread and numerous. The facts that SBMYV persists longer than SBYV inMyxus persicaeSulz. and is not lost during moulting apparently also favour the wider distribution of t

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1963.tb03764.x

出版商:Blackwell Publishing Ltd    

年代:1963

数据来源: WILEY

摘要:

SUMMARYNo 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 measure

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1963.tb03765.x

出版商:Blackwell Publishing Ltd    

年代:1963

数据来源: WILEY

摘要:

SUMMARYThe hatch of beet eelworm (Heterodera schachtiiSchm.) larvae from cysts in 0–1% aqueous solutions of rivanol (3,9‐diamino‐7‐ethoxyacridine lactate) was greatest and fastest in 1 % rivanol, which also inhibited the growth of micro‐organisms. The hatching effect of rivanol was specific to beet eelworm out of fiveHeteroderaspecies tested. Larval hatch from cysts on nylon sieves at the surface of 1% rivanol was not lessened by a thin layer of debris, nor was hatch affected by soil storage and drying times except with new cysts.Measuring the density of beet eelworm infestations in fields by larval hatch in rivanol would avoid errors from inclusion of related species, observer bias, and difficulties of determining viability. The number of cysts used could easily be increased to help reduce sampli

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1963.tb03766.x

出版商:Blackwell Publishing Ltd    

年代:1963

数据来源: WILEY

摘要:

SUMMARYA study of thirteen species of nematode‐trapping Hyphomycetes demonstrated wide differences in their growth rate, competitive saprophytic ability, effect on free‐living nematode populations and ability to produce traps spontaneously.The species producing adhesive reticulate traps tended to have the most rapid growth rates and the highest saprophytic ability ratings. In the soil they appeared to be pre‐daceously inefficient and did not form traps in pure culture. In contrast the ring‐formers had slow growth rates and lower saprophytic ability ratings. They tended to be predaceously efficient and two of the four species studied formed traps spontaneously. The adhesive branch or knob‐forming fungi resembled the ring‐formers in their growth rates, predaceous efficiency and spontaneous trap formation.Thus it appears that the development of predaceous efficiency has been accompanied by a tendency to lose those characters associated with an efficient saprophytic existence in the soil; namely rapid growth rate and good competitive saprophy

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1963.tb03767.x

出版商:Blackwell Publishing Ltd    

年代:1963

数据来源: WILEY

摘要:

SUMMARYAll isolates ofVerticillium albo‐atrumfrom lucerne are virulently pathogenic to this host, whereasV. dahliaeis 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’ ofV. albo‐atrumandV. dahliae.However, both these strains can infect broad bean, strawberry, Italian clover (Hedy‐sarum coronarium) and pea, whileV. albo‐atrummay also attack potatoes and runner beans.V. albo‐atrumspreads 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‐atrumspreads 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 vulgarisandAnthemis 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

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1963.tb03768.x

出版商:Blackwell Publishing Ltd    

年代:1963

数据来源: WILEY