摘要:

Summary: Résumé: ZusammenfassungSelective control or suppression ofCyperus rotundusL. in carrot (Daucus carotaL.) was investigated in Brazil using post‐emergence applications of nitrofen (2,4‐dichlorophenyl 4‐nitrophcnyl ether) or a herbicidal oil (11–7% aromatics). Night applications of nitrofen in water, nitrofen in the herbicidal oil and the herbicidal oil alone were more effective in suppressing the growth ofC. rotundusfoliage than day applications. Nitrofen and the herbicidal oil were, respectively, 50 and 30% more active in suppressingC. rotundusduring the warm, wet season (October to March) than the cool, dry season (April to September) in Viçosa. Night applications of nitrofen (1, 2 and 4 kg/ha) in water and the herbicidal oil alone (100, 200 and 400 1/ha) suppressedC. rotundusby 60% or more, and resulted in similar carrot yields to the hand‐weeded control. Combinations of nitrofen in the herbicidal oil were more effective in suppressingC. rotundusthan either herbicide applied alone, but the combinations tested were toxic to the carrots.Elimination duCyperus rotundusL. dans les cultures de carrottes au moyen d'applications nocturnes de nitrofène ou d'une hui

ISSN:0043-1737    

DOI:10.1111/j.1365-3180.1975.tb01320.x

出版商:Blackwell Publishing Ltd    

年代:1975

数据来源: WILEY

摘要:

SummaryAtrazine, simazine, diuron, and linuron applied to soil increased the percentage moisture of oat (Avena sativaL.) shoots in bioassays at the lowest dose tested of 0·25 ppm. Further increases occurred up to 2 ppm but at higher concentrations the percentage moisture decreased. At all doses of each herbicide, shoot dry weight was decreased. In oats grown on soil collected from a peach orchard which had received repeated annual applications of these herbicides, the percentage moisture of the oat shoots was higher than the control value whenever the oat dry weight was decreased and provided a method of residue detection as sensitive as dry weight measurements. Treatment of oats by soil application of the above herbicides in bioassays also caused increases in the electrical conductivity of an aqueous extract of the oat shoots per mg of dry weight and this characteristic was slightly more sensitive than dry weight in detecting herbicides in orchard soil. The conductivity of the extract per mg of water in the shoots, however, only increased as percentage moisture decreased. The weight of neutral water‐soluble material in oat shoots decreased much more rapidly than dry weight in bioassays with standard herbicide concentrations. Determination of the weight of neutral water‐soluble material in oat plants grown on orchard soil samples indicated the presence of herbicide residues in 50% of the cases in which residues were not detectable by dry weight. The weight of neutral material as a percentage of dry weight was almost as sensitive. Chemical analysis of soil in which oat plants had a decreased level of neutral water‐soluble compounds indicated that this characteristic had a lower limit of detection for herbicide residues of approximately 0.

ISSN:0043-1737    

DOI:10.1111/j.1365-3180.1975.tb01321.x

出版商:Blackwell Publishing Ltd    

年代:1975

数据来源: WILEY

摘要:

SummaryExperiments were undertaken to define the conditions under which seeds and seedlings ofAgropyron repensandAgrostis giganteamay start infestations in cereal crops.When seedlings were planted early or late in spring wheat and spring barley, most growth of shoots and rhizomes was produced byAgropyronplanted early in wheat. Late planting halved the amount of shoot growth and severely inhibited rhizome formation. In winter wheat given a moderate or zero amount of nitrogen fertilizer in spring, growth of the weed seedlings was slow. Rhizomes were not produced during the time the crop was growing but only after harvest.Agrostismade more growth thanAgropyronin most treatments throughout most of the experiment. Late planting decreased growth more than in the spring cereals. Nitrogen fertilizer, although it had little effect on the amount of growth made by winter wheat, increased the growth of the early‐planted seedlings but decreased that of the late‐planted ones of both weed species. When planted into plots given nitrogen, more seedlings of both species died after late than after early planting.Clearly, the amount of growth and rhizome produced by seedlings of these two species will depend on the type of cereal, the time of emergence of the seedlings in relation to the cereal, and on other factors affecting the relative vigour of cereal and weed. Evidently, where the weed seedlings emerge early in weakly or moderately competitive cereal crops or when growth is unchecked in the cereal stubble, seedlings could give rise to infestati

ISSN:0043-1737    

DOI:10.1111/j.1365-3180.1975.tb01322.x

出版商:Blackwell Publishing Ltd    

年代:1975

数据来源: WILEY

摘要:

SummaryExperiments are described in which plants from six different populations of the outbreeding annual weedTripleitrospermum inodorumwere grown with barley in field plots and sprayed with 4‐chloro‐2‐melhyIphenoxyacetic acid (MCPA) at a number of doses. The populations showed significant differences in reduction of weight, the most resistant population having an ED50of 181 ± 36·9 mg/m2a.e.MCPA, 2·49 limes as great as the ED50of the least resistant population. In a second experiment in which plants from these two populations were again grown with barley in field plots and sprayed with several doses of MCPA at three different stages of growth, their resistance to MCPA was found to differ consistently at all three stages of growth, the more resistant population having a mean LD50of 1103 ± 161·5 mg/m2a.e. MCPA, 2·09 times as great as the mean LD50of the less resistant population. The populations were similar in other respects. The differences in the spraying histories of the two populations were consistent with the supposition that the differences in resistance to MCPA had resulted from natural selection for MCPA resistance in the more intensively sprayed population, but other processes may also have be

ISSN:0043-1737    

DOI:10.1111/j.1365-3180.1975.tb01323.x

出版商:Blackwell Publishing Ltd    

年代:1975

数据来源: WILEY

摘要:

SummaryForty‐eight populations of Tripleurospermum inodorum (L.), Schultz Bip. (scentless mayweed) were collected from southern Britain and northern France between 1970 and 1972 and screened simultaneously for resistance to the herbicides ioxynil and MCPA. The mean fresh weights per plant in different population samples sprayed with ioxynil at 28 mg/m2a.i. ranged from 2·2 to 39·5% of those of the corresponding controls, with a mean for all populations of 20·0 ± 1·09%, and the mean fresh weights per plant in different population samples sprayed with MCPA at 175 mg/m2a.e. ranged from 10·3 to 60·1% of those of the corresponding controls, with a mean for all populations of 43·0 ± 1·60%. Resistance to ioxynil differed significantly between populations from different geographic areas but showed no correlation with spraying history. Resistance to MCPA also differed significantly between populations from different geographic areas, and showed a strong positive correlation with ioxynil resistance, but MCPA resistance was significantly greater in populations with a history of heavy spraying than in other populations. Spray retention and other physical characteristics were measured in six populations, but showed no correlation with herbicide resistance. It is suggested that most of the differences in herbicide resistance between populations ofT. inodorumare side effects of genotypic differentiation in physiological characters not directly related to herbicide resistance, but that there has been some direct selection for resista

ISSN:0043-1737    

DOI:10.1111/j.1365-3180.1975.tb01324.x

出版商:Blackwell Publishing Ltd    

年代:1975

数据来源: WILEY

摘要:

SummaryA sample of 100 seedlings from a weed population of T. inodorum which had been found to be relatively sensitive to MCPA was exposed to an MCPA concentration sufficient to give a 38% kill, and the five most vigorous survivors were combined in a polycross. When sprayed with MCPA, the progeny of the polycross had an LD5015·4% greater and a mean fresh weight per plant 30·2% greater than that of unselected controls. In a similar selection among plants from the same population for ioxynil resistance, the initial kill was 81% and (he progeny of selected plants had an LD5077·3% greater and a mean fresh weight per plant 43·3% greater than that of unselected controls; and in a similar selection for simazine resistance, the initial kill was 99% and the progeny of a selected plant had an LD5017·0% greater and a fresh weight per plant 88·4% greater than that of unselected controls. The increase in resistance to MCPA and ioxynil was less than the differences between populations observed in previous screenings, and the selected plants were considerably less resistant than the most resistant wild popula

ISSN:0043-1737    

DOI:10.1111/j.1365-3180.1975.tb01325.x

出版商:Blackwell Publishing Ltd    

年代:1975

数据来源: WILEY

摘要:

SummaryTemperatures from 13°C to 30°C had no significant effect on the formation of shoots on root segments ofRubus procerusP. J. Muell. Shoots were not produced at 8°C. Some new roots were produced on root segments at all temperatures between 8°C and 30°C, although significantly more (P= 0·05) roots were produced at 26°C. The polarity of the root system was maintained in root segments. More shoots were formed towards the basal end, i.e. nearest the crown, and more roots towards the apical end of the root se

ISSN:0043-1737    

DOI:10.1111/j.1365-3180.1975.tb01326.x

出版商:Blackwell Publishing Ltd    

年代:1975

数据来源: WILEY

摘要:

SummaryNutgrass tubers were planted in pots on thirteen occasions at 4‐weekly intervals, and growth and development followed by sampling at 5‐day intervals from 10 to 45 days after planting. Growth rates, final shoot numbers, dry weights and rhizome lengths, and new tuber production were highest in plantings made 1 and 29 March and 26 April. Correlation coefficients suggested that mean daylength during growth was a major factor influencing growth and development, but mean temperature appeared to be important in determining new tuber size and the proportion of dry‐matter as new tubers. Shoot number appears to be a reliable guide to rhizome and tuber produ

ISSN:0043-1737    

DOI:10.1111/j.1365-3180.1975.tb01327.x

出版商:Blackwell Publishing Ltd    

年代:1975

数据来源: WILEY

ISSN:0043-1737    

DOI:10.1111/j.1365-3180.1975.tb01328.x

出版商:Blackwell Publishing Ltd    

年代:1975

数据来源: WILEY

ISSN:0043-1737    

DOI:10.1111/j.1365-3180.1975.tb01329.x

出版商:Blackwell Publishing Ltd    

年代:1975

数据来源: WILEY