摘要:

Summary:Losses of about 40% in cane yields due to natural stands of weeds were found in experiments conducted in sugarcane var. Co 527 in the year of planting at Guneid Sugarcane Research Station, Sudan. Weed competition lowered millable stalks per metre row by 32%, stalk height by 24%, stalk thickness by 15% and number of nodes per stalk by 14%. Tillering was the growth phase most affected by weed competition.Cane yields were increased as number of hand weedings increased, but four weedings were not markedly better than three. The average yield (67·04 t ha−1) obtained from four weedings was not significantly (P= 0·05) better than that of three weedings carried out at 3, 6 and 9 weeks after cane planting.Juice analysis components were also affected by weeds and a 15% reduction in sucrose recovery was recorded. Reductions in the other components were only 4–7%.Atrazine and diuron (3·3 kg ha−1), metribuzin (2·4 kg ha−1) and metribuzin (1·3 kg ha−1) in tank mixture with diuron (1·5 kg ha−1) gave excellent residual weed control of the dominant weed species,Ipomoea cordofanaChoisy.,Brachiaria eruciformis(Sm.) Griseb.,Corchorus fascicularisLam.,Ocimum basilicumL. andDinebra retroflexa(Vahl) Panz., for most of the first growing season. Excellent control of weeds achieved by the herbicide treatments resulted in comparable yields to frequently‐weeded cane. These herbicides were not phytotoxic to su

ISSN:0043-1737    

DOI:10.1111/j.1365-3180.1984.tb01558.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

Summary:Studies were made in the Sudan for microorganisms pathogenic to water hyacinth (Etchhornia crassipesSolms) for biological control purposes. Many fungi and bacteria were isolated from plant parts showing disease symptoms. Pathogenicity tests revealed that only five out of the twenty‐five fungal and bacterial isolates were damaging to the weed plant. These includedAcremonium zonatum, Drechslera speciferaandFusarium equiseti. Phoma sorghinaand a bacteriumBacillussp. are reported for the first time as potential pathogens of water hyacinth. Pathogenic isolates were also found to produce toxic metabolites in liquid culture

ISSN:0043-1737    

DOI:10.1111/j.1365-3180.1984.tb01559.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

Résumé:Nous avons disposé de DNTBP et de DNOC uniformément marqués au14C sur le noyau benzénique. La pénétration foliaire et racinaire, ainsi que la translocation du DNTBP sont lentes. Il a été possible de mettre en évidence, après 3 jours déjà, des composés de dégradation très éloignés des herbicides de départ. Un catabolite cinquante fois moins actif que le DNTBP a été identifié: le méthyl‐2(hydroxy‐2′dinitro‐3′5′‐phényl)‐2 propanol‐1. Sur le plan biologique, le DNTBP et le DNOC exercent un effet dèsorganisateur des membranes lipidiques.Penetration, tr

ISSN:0043-1737    

DOI:10.1111/j.1365-3180.1984.tb01560.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

Summary:In greenhouse studies, the efficacy of the herbicide safeners NA(1,8‐naphthalic anhydride), R‐25788 (N,N‐diallyl‐2,2‐dichloroacetamide), cyometrinil and CGA‐92194 [N‐(1,3‐dioxolan‐2‐yl‐methoxy)imino‐benzeneaceto‐nitrile] in protecting grain sorghum (Sorghum bicolor(L.) Moench, cv. ‘Funk G623’) against injury from pre‐emergence or early post‐emergence applications of the herbicides chlorsulfuron, fluazifop‐butyl and sethoxydim was examined. NA as a seed dressing at 0·5 or 1·0% (w/w) was the most effective of the four safeners and offered partial to good protection to sorghum against injury from the lower rates of pre‐emergence applications of all three herbicides. R‐25788 was totally ineffective as a sorghum protectant against fluazifop‐butyl injury but it did antagonize partially the injurious effects of the lower rates of sethoxydim and chlorsulfuron on sorghum. Cyometrinil and CGA‐92194 offered partial protection to sorghum against injury from the lowest rate of all herbicides but their efficacy against higher rates of the three herbicides was very limited. None of the four safeners was effective in protecting grain sorghum against injury from post‐emerge

ISSN:0043-1737    

DOI:10.1111/j.1365-3180.1984.tb01561.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

Summary:The initial and residual activities of wettable powder formulations of atrazine comprising different particle sizes were investigated in field and glasshouse experiments. A flowable formulation was also compared with these. Oats were used as the test species for the glasshouse studies while in field trials effects on control of broadleaf weeds in maize were studied. No marked differences were noted in the activity of wettable powders of different particle sizes in the glasshouse as pre‐emergence applications. As a post‐emergence treatment the fine particle size was more phytotoxic than the coarse material, especially when a wetting agent was added to the spray solution. In the field trials, no appreciable differences in weed control or crop tolerance could be established regardless of the time or rate of application. The flowable formulation was less active than the wettable powders in some glasshouse experiments but no such trend was apparent in field trials. Bioassays showed that the residual activity of the flowable formulation was lower than wettable powder formulations in both glasshouse and field studies but no consistent differences were noted in the persistence of the three forms of wettable powd

ISSN:0043-1737    

DOI:10.1111/j.1365-3180.1984.tb01562.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

Summary:Soil from arable areas in Scotland was examined macroscopically for seeds. In terms of the percentage of sites at which they were recorded,Chenopodium albumL. (33%),Poa annuaL. (22%),Polygonum aviculareL. (41%),Polygonum persicariaL. (39%),Spergula arvensisL. (42%) andStellaria media(L.) Vill. (44%) were the most common species found. They accounted for 78% of the seeds recovered. There were eighty different species found over the 5 years of the survey. Estimated total weed populations (m−2) ranged from nil to 170000 with an average of 16000 m−2in the top 20 cm of s

ISSN:0043-1737    

DOI:10.1111/j.1365-3180.1984.tb01563.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

Summary:Field experiments were conducted in the early and late cropping seasons of 1979 on a loamysand Oxic Ustropept in a subhumid environment in Nigeria, using 40000, 50000 and 30000 + 40000 plants ha−1of maize (Zea maysL. cv. TZB), cowpea (Vigna unguiculata(L.) Walp. cv. VITA‐5) and maize/cowpea intercrop respectively. These indicated that weed interference effects on crops under no‐tillage depended on cropping season, cropping pattern and crop species. In the early and late seasons respectively, thirty‐five and twenty‐nine different weed species were recorded and weed dry weights of approximately 10·4 and 5·7 t ha−1from the plots kept weedy throughout the season reduced corresponding food energy yields by 60 and 82%. Except for the intercrop, which in the early season showed significant yield reduction when exposed to 4 weeks’ weed interference after sowing, all cropping patterns needed more than 4 weeks’ interference to show significant yield reductions, regardless of cropping season. In the early season, weed interference accounted more for the yield reductions in monocultures than it did for those in the intercrop, but in the late season all cropping patterns were equally sensitive to weed association. Maize, which performed much better in the early season, showed greater yield reductions than cowpea under early weed interference but less under full‐season interference irrespective of cropping pattern and season. Cowpea seed quality was more reduced by intercropping than by weed interference in the early season but neither of these factors affected seed quality significantly

ISSN:0043-1737    

DOI:10.1111/j.1365-3180.1984.tb01564.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

Summary:Early growth and nutrient content of crops and weeds from weed‐free and weedy no‐tillage maize (Zea maysL, cv. TZB), cowpea (Vigna unguiculata(L) Walp. cv. VITA‐5) and maize/cowpea intercrop at populations of 40000, 50000 and 30000 + 40000 plants ha−1grown on a loamysand Oxic Ustropept in a subhumid tropical location were monitored in the early and late 1979 cropping seasons. In the first 6 weeks of growth in the early season, cropping pattern had no effect on weed growth; weeds did not suppress crop growth significantly until 5–6 weeks after sowing and total crop dry weights were not affected by cropping pattern. Three weeks after sowing, weeds from weedy crop plots had taken up two to four times as much nutrient (N, P, K, Ca + Mg) as was taken up by corresponding weed‐free crops. In the late season, weed dry weight 6 weeks after sowing was depressed in the intercrop compared to monocultures and dry‐matter production of the intercrop was higher than those of monocultures. The resource use index (RUI), defined as the amount of an environmental resource used by a weed‐free crop divided by the combined amount of the same resource used by the corresponding weedy crop and the associated weeds, increased with age of crop and was higher for the intercrop than the monocultures only in

ISSN:0043-1737    

DOI:10.1111/j.1365-3180.1984.tb01565.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

Summary:The persistence of bromoxynil (3,5‐dibromo‐4‐hydroxybenzonitrile), [14C]dicamba (3,6‐dichloro‐2‐methoxybenzoic‐7‐14C acid) and propanil [N‐(3,4‐dichlorophenyl)propionamide] at rates equivalent to 1 kg ha−1, were studied under laboratory conditions in a clay loam, a heavy clay and a sandy loam at 85% of field capacity and at 20±1°C, both singly and in the presence of herbicides normally applied with these chemicals as tank‐mix or split‐mix components.The degradation of bromoxynil was rapid with over 90% breakdown occurring within a week in the heavy clay and sandy‐loam soils, while in the clay‐loam approximately 80% of the bromoxynil had broken down after 7 days. In all three soils degradation was unaffected by the presence of asulam, diclofop‐methyl, flamprop‐methyl, MCPA, metribuzin or propanil.Propanil underwent rapid degradation in all soil treatments, with over 95% of the applied propanil being dissipated within 7 days. There were no noticeable effects on propanil degradation resulting from applications of asulam, barban, bromoxynil, dicamba, MCPA, MCPB, metribuzin or 2,4‐D.The breakdown of [14C]dicamba in a particular soil was unaffected by being applied alone or in the presence of diclofop‐methyl, flampropmethyl, MCPA, metribuzin, propanil or 2,4‐D. The times for 50% of the applied dicamba to be degraded were approximately 16 days in both the clay loam and sandy

ISSN:0043-1737    

DOI:10.1111/j.1365-3180.1984.tb01566.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

Summary:A series of glasshouse experiments was conducted to evaluate the activity of fluazifop‐butyl, butyl 2‐[4‐(5‐trifluoromethyl‐2‐pyridyloxy)phenoxy] propionate, againstElymus repens.Foliar applications of doses 0·25–1·0 kg ha−1consistently gave better control than did soil applications. The most obvious phytotoxic symptoms were chlorosis and necrosis, beginning with the youngest leaves 5–6 days after spraying, which spread to all leaves within 2 weeks. Translocation was measured by defoliating plants at different times after spraying and assessing regrowth and by evaluating rhizome‐bud viability. At low doses (0·125 and 0·25 kg ha−1) translocation to rhizomes occurred mainly between 6 and 48 h. When fluazifop‐butyl was sprayed at a dose range of 0·125–1·0 kg ha−1, at least 90% of the rhizome buds had accumulated a lethal dose within 72 h of spraying. In another experiment, with a dose of 0·25 kg ha−1, 31, 72 and 92% of rhizome buds were found to be non‐viable when sampled 2, 24 and 48 h respectively after spraying. At 1·0 kg ha−1all the buds had accumulated sufficient herbicide

ISSN:0043-1737    

DOI:10.1111/j.1365-3180.1984.tb01567.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY