摘要:

Summary:The effects of handweeding and of varying timing of applications of nitrogen were examined in three experiments on maize grown in Southern Nigeria. At two weedy sites which had been cropped for several years, weed competition lowered maize yields by 50% and two hand weedings at 3 and 7 weeks after planting were as satisfactory as more extended weedings. At the third site after an extended fallow period weed competition was not severe. Splitting of nitrogen application generally had no advantage over a single application of the same amount. There was no significant interaction between nitrogen and weeding treatments at any site.

ISSN:0043-1737    

DOI:10.1111/j.1365-3180.1979.tb01577.x

出版商:Blackwell Publishing Ltd    

年代:1979

数据来源: WILEY

摘要:

Summary:Trifluralin in cotton and benfluralin in groudnut. incorporated pre‐planting. gave satisfactory control of grass weeds and increased crop yields substantially. Oxadiazon as a pre‐planting treatment did not give satisfactory additional control of dicotyledons resistant to the first two herbicides. A post‐sowing mechanical ridging operation controlled some herbicide resistant weeds, but its effects depended on timing, weed species and growing conditions. Supportive hand weeding of resistant weeds (mainly dicotyledons) was most effective 4 weeks after crop emergence. Crop yields similar to clean weeded controls were achieved by combining trifluralin or benfluralin with moderate supportive hand weeding and re‐ridging. Herbicide applications could be made several months before crop planting during the dry season, giving more effective use of spray equipment and operatives. Delays of up to 24 hours between spraying and incorporation by normal cultivation could be tolerated without loss of herbicidal a

ISSN:0043-1737    

DOI:10.1111/j.1365-3180.1979.tb01578.x

出版商:Blackwell Publishing Ltd    

年代:1979

数据来源: WILEY

摘要:

Summary:The effect of herbicide placemem in the soil on control ofCyperus rotundusL. was studied in the greenhouse with EPTC, alaehlor, norfiurazon, perlluidone, napropamide, trifluralin, and naptalam, EPTC was the mosl active herbicide, increasing the number of sprouts per tuber but inhibitmg bud development at an early stage of growth. The effect was greatest when EPTC was incorporated with the soil around the tubers. The effects of alaehlor were similar, but higher doses were required. Another active herbicide, norfiurazon, was taken up by the roots but its effect was to produce small, chlorotic leaves, Perfluidone was mosl effective when incorporated into the soil around the tubers or when placed in a layer 1 cm above them. Very little effect of napropamide trifluralin and naptalam was observed. In studies of growth and deveiopmenl with different planting depths,C. rotumtusproduced basal bulbs, roots and most of its early reproductive parts in a layer of soil 1–3 cm from the surface, irrespective of the depth at which the tubers were planted. Shoots etncrged from 35 im deep but not from 50 c

ISSN:0043-1737    

DOI:10.1111/j.1365-3180.1979.tb01579.x

出版商:Blackwell Publishing Ltd    

年代:1979

数据来源: WILEY

摘要:

Summary:Kivc main points have emerged from this study: (i) populations of the cactusOpuntia aurantiacaLindley are highly aggregated; (ii) searching efficiency of spray teams applying herbicides is low because they fail to locate small isolated plants; (iii) searching efficiency is positively correlated with aggregation of the target plant; (iv) the presence of the cochinealDactylopius austrinusDe Lotto is also positively associated with aggregations of the host plant and; (v) consequently, cochineal populations are selectively eliminated by current spraying techniques to the detriment of biological control. The implications of these findings are discussed in relation to future strategies for chemical and biological control of the weed.

ISSN:0043-1737    

DOI:10.1111/j.1365-3180.1979.tb01580.x

出版商:Blackwell Publishing Ltd    

年代:1979

数据来源: WILEY

摘要:

Summary:Hmergence of dodder (Cuseuta australisR. Br.) was unexpecledly prevented in plois of a sugarbeet field where ethofumesate had been applied at 1.6 Kg/ha. Appropriate laboratory tesls have shown that ethofumesate is a potent inhibitor of dodder seed germination (I D50= 10 μg/ml) and of early stem elongalion (ID50= 73μg/ ml). Wheat. a standard susceptible species to field applications of ethofumesate, is equally susceptible to inhibition of stem elongation (ID50=68 μg/ml), but it is far less susceptible to inhibition of germination (I D50=188 μg/ml). Compared to propyzamide. ethofiimesate is a stronger inhibitor of germination. Metolachlor and Hercules 22234 [eihylN‐chloroacetyl‐N‐(2,6‐diethylphenyl) aminoacetate] are also active in inhibiting dodder germination and stem elongation, but at higher concentrations than ethofumesate. Current methods of controlling dodder in sugarheets may be improved with inclusion of pre‐emergence use of

ISSN:0043-1737    

DOI:10.1111/j.1365-3180.1979.tb01581.x

出版商:Blackwell Publishing Ltd    

年代:1979

数据来源: WILEY

摘要:

Summary:The mechanism whereby Iinuron changes the functional and structural characteristics of chloroplast membranes was studied. The primary effect of the herbicide, the inhibition of phoiosynihetic electron transport results in an immuediatecessa‐tion of carbon dioxide fixation and alterations in the membrane energization. These are accompanied by secondary processes contributing to phytotoxicity. The fundamental action in its phytotoxicity, as shown in a model system of isolated chloro‐plasts, is the peroxidaiive breakdown of the polyunsaturated membrane lipids. This leads to destruction of the pigments, changes in the energy transfer, disorganization of the chloro‐plast membranes, and accumulation of toxic organic pero

ISSN:0043-1737    

DOI:10.1111/j.1365-3180.1979.tb01582.x

出版商:Blackwell Publishing Ltd    

年代:1979

数据来源: WILEY

摘要:

Summary:Application of several herbicides and a combination of herbicides in two vineyards resulted in a perfect control of Bermuda grass by glyphosate and mixed or alternate applications of MSMA and dalapon. Johnson grass was eliminated by MSM A with and without the addition of dalapon. Dalapon combined with MSMA reduced the yield of the grapevines and their growth, as measured by the weight of pruning. Yields were also significantly reduced by aminotriazole and in one vineyard also by simazine. Reduced vegetative growth was caused by MSMA and glyphosphate.MSMA and glyphosphate reduced the chlorophyll content of the grape leaves and the reducing sugar content of the canes in winter. Amino triazole reduced the reducing sugar content of both leaves and canes and the nitrogen content of the canes. In one vineyard simazine reduced the chlorophyll content of the leaves and increased the nitrogen content of the canes. MSMA alone and in combination with dalapon increased the arsenic content of leaves, canes and fruits of grapevines. Arsenic levels were the highest in the canes, but still did not exceed 0.6 ppm. Levels were lowest in fruits and did not exceed 0.1 ppm. Dalapon reduced the chlorophyll content of leaves in June and increased it in July. It also affected the reducing sugar content of leaves and canes without affecting yields or growth.

ISSN:0043-1737    

DOI:10.1111/j.1365-3180.1979.tb01583.x

出版商:Blackwell Publishing Ltd    

年代:1979

数据来源: WILEY

摘要:

Summary:I‘activité biologique d'un résidu de synthese du diuron, identi‐fiéåla 1.3‐his‐(3,4‐dichlorophényl) urée. a éiéétudiéesur E. coli. mitochondries de pomme de terre. chloroplasies et lipo‐somes.Ce composé inhibe la croissanee d'E. coliet semble modifier les permétions membraires. II ayit comme un découplant trés actif des oxydations phosphorylames: il bloque la réaction de Hill de chloroplastes isoles et modifie les pro‐priété des membranes liposomales. Cette activité est comparée à celle dea diuron technique et purifié et peut †tre responsablede

ISSN:0043-1737    

DOI:10.1111/j.1365-3180.1979.tb01584.x

出版商:Blackwell Publishing Ltd    

年代:1979

数据来源: WILEY

摘要:

Summary:Non‐competitive effects between lamb's quarters(Chenopodium albumL.) and maize (INRA 25H)Maize is extremely sensitive to competition from weeds, lamb's quarters (C.alhum) often being particularly competitive, Under controlled conditions in a growth chamber short term bioassay methods techniques have shown that lamb's quarters exerted inhibiting influences on maize growth which were not attributable to competition alone. These non‐compctitive, specific influences became apparent mainly from the early flowering stage of lamb's quarters both in soil and in nutrient solution. With an identical concentration of lamb's quarters roots, the growth‐inhibiting effects are more marked when the soil structure is modified than when it is not, similarly when the aqueous extract is obtained by placing soils in suspension, the inhibiting effects are more marked than when it is obtained by percolation. Finally, water leached from the leaves, roots or seeds of lamb's quaners shows inhibiting effects proport ional to the concentration on root growth of maize. The presence of phytotoxins in the culture media of lamb's quarters is disc

ISSN:0043-1737    

DOI:10.1111/j.1365-3180.1979.tb01585.x

出版商:Blackwell Publishing Ltd    

年代:1979

数据来源: WILEY

摘要:

Summary:Established Greenhouse grown plants of cogongrass Imperata cylindrica (L) Beauv.) and purple nutsedge (Cyperus rotundusL.) were given three different soil moisture regimes; field capacity, moderate stress and extreme stress, followed 6 weeks later by glyphosate [(N‐phosphonomeihyl) glydne] applications to the shoots at 0.2,0.4 and 0.8 kg/ha for Imperata and 0.3,0.6 and 1.12 kg/ha for Cyperus. Field capacity watering stimulated most vegetative growth in hoth species. Glyphosate given at field capacity decreased shoot dry weight in both species, and rhizome length, rhizome dry weight and total carbohydrate inImperataand total number of tuber‐bulbs inCyperus. In contrast. at extreme soil moisture stress, glyphosate showed reduced activity which appeared to be related to the physiological and morphological behaviour of the plants arising from the drought trealment. Application of waier to the roots of the plants grown at soil moisture stress. I week before and I week afler glypbosate spraying, enhanced glyphosate activity, probably because of the recovery of processes disturbed by ibe soil moisture defi

ISSN:0043-1737    

DOI:10.1111/j.1365-3180.1979.tb01586.x

出版商:Blackwell Publishing Ltd    

年代:1979

数据来源: WILEY