Alternative Weed Control Methods Research Articles

Determinação de espécie indicadora e comparação de genótipos de girassol quanto ao potencial alelopático

Na agricultura atual, o método mais utilizado para o controle de plantas daninhas é o químico, em razão da facilidade de uso, elevada eficiência e baixa necessidade de mão de obra. No entanto, a utilização inadequada desses produtos provoca problemas ao ambiente e à saúde humana. Cresce, portanto, a busca por métodos alternativos de controle de plantas daninhas, menos demandadores de energia e menos tóxicos e agressivos ao ambiente. Este trabalho objetivou avaliar o efeito alelopático da cultura do girassol (Helianthus annuus) sobre diferentes espécies de plantas daninhas e cultivadas, em dois experimentos realizados em delineamento experimental completamente casualizado, utilizando o método da semeadura em substituição. O primeiro experimento foi realizado com quatro repetições, em esquema bifatorial. O primeiro fator foi constituído por seis espécies indicadoras: picão-preto (Bidens pilosa), corda-de-viola (Ipomoea grandifolia), caruru (Amaranthus hybridus), alface (Lactuca sativa, cultivar Aurélia), tomate (Lycopersicon esculentum, cultivar Santa Cruz), trigo (Triticum aestivum, cultivar BRS 208); e o segundo, pela presença ou não de plântulas de girassol. O segundo experimento foi composto por 24 tratamentos, representados por 23 genótipos de girassol e por uma testemunha sem girassol, utilizando-se quatro repetições. A espécie indicadora foi apenas o picão-preto. Em ambos os experimentos, no final do período de sete dias de convívio, foram avaliados o número de sementes germinadas e o comprimento radicular e da parte aérea das espécies indicadoras. Não foram observadas diferenças entre as porcentagens de germinação de quaisquer das espécies indicadoras avaliadas, em função da presença ou não das plântulas de girassol. A presença de plântulas de girassol estimulou o crescimento radicular das plântulas de tomate e trigo e inibiu o crescimento da parte aérea de picão-preto, trigo e corda-de-viola. Houve grande variabilidade de potencial alelopático entre genótipos de girassol sobre a germinação e o crescimento radicular e da parte aérea de Bidens pilosa. Os resultados demonstram que a técnica da semeadura em substituição é adequada para detectar efeitos estimulativos ou inibitórios de girassol sobre espécies indicadoras e para discriminar genótipos de girassol quanto à habilidade em inibir ou estimular plântulas de Bidens pilosa.

A review of pesticide policies and regulations for urban amenity areas in seven European countries

SummaryAn analysis of the regulations of herbicide use for weed control in non‐agricultural/urban amenity areas, including actual pesticide use, was carried out as a joint survey of seven European countries: Denmark, Finland, Germany, Latvia, the Netherlands, Sweden and United Kingdom. Herbicides constitute the major part of the pesticides used in urban amenity areas. Herbicide use on hard surfaces is the largest in terms of volume and potential contamination of surface and groundwater. The aim of the study was to investigate the differences in political interest and public debate on the ‘use of pesticides in public urban amenity areas’, regulations within each country at national, regional and local levels, possible use of alternative weed control methods and the amounts of pesticides used on urban amenity areas. A comparative analysis revealed major differences in political interest, regulations and availability of statistics on pesticide use. Denmark, Sweden, the Netherlands and Germany have, or have had, a strong public and political interest for reducing the use of herbicides to control weeds in urban amenity areas and also have very strict regulations. The UK is currently undergoing a period of increasing awareness and strengthening regulation, while Latvia and Finland do not have specific regulations for weed control in urban amenity areas or on hard surfaces. Statistics on pesticide/herbicide use on urban amenity areas were only available in Denmark and the Netherlands. Developing this kind of information base reveals the differences in herbicide use, regulations and policies in European countries and may enhance the transfer of knowledge on sustainable weed control across countries.

Annual Medicago as a Smother Crop in Soybean

AbstractUse of conservation tillage and narrow row spacing in soybean [Glycine max (L.) Merr.] production has led to increased use of herbicides for weed control. Some producers are seeking alternative weed control methods, such as smother crops, that would reduce dependence on chemical weed control. A successful smother crop must compete strongly with weeds but minimally with the crop. In four environments, we intercropped three annual Medicago spp. (medics) with soybean to test their utility as a smother crop for weed control. Annual medics were intercropped with soybean at rates of 0, 85, 258, or 775 seeds m−2, and the intercrops were grown with and without weed control. Increasing medic seeding rate decreased weed yields but also reduced soybean herbage and grain yields. For the weed‐controlled treatment, average soybean grain yields declined 7 kg ha−1 for every 10 seeds m−2 increase in medic seeding rate. Soybean grain yield was lower when grown with Medicago scutellata L. cv. Sava than when grown with Medicago polymorpha L. cv. Santiago or Medicago lupilina L. cv. George. Soybean grain yield was negatively related (r=−81) to medic herbage production. In the autumn following soybean harvest, medic residue ranged from 200 to 3700 kg ha−1 depending on the location and seeding rate. Medics provided residue for soil protection, suppressed weeds, but also reduced soybean yields.

Herbicides are more cost-effective than alternative weed control methods for increasing early growth of Eucalyptus dunnii and Eucalyptus saligna

Effective weed control is an essential management task in establishing commercial tree plantations. Much of the current weed control strategies employed in Australian forestry relies on the use of available herbicides. However, given community concern regarding the use of herbicides, investigation of alternative weed control methods is warranted. We tested the ability and cost-effectiveness of mechanical (hand weeding and inter-row slashing), mulching (sawdust over newsprint, woodchips and jute), cover crops and herbicide applications for weed control in establishing eucalypt plantations. Jute matting and herbicide treatments reduced weed competition and increased seedling growth to age 2 years in plantations of Eucalyptus dunnii and Eucalyptus saligna in northern NSW, Australia. Growth increased by 269 % (Experiment 1) and 196 % (Experiment 2) in the Jute and by 216 % (Experiment 2) in the Herbicide treatments when compared to the control (no weed control) at 2 years age. As the Jute material deteriorated, after nearly 2 years, weed cover increased and there were significantly more weeds present in the Jute treatment compared to the Herbicide treatment. Jute matting costs approximately 15 times more than the herbicide regime used and, therefore, could not presently be considered a viable option for weed control in commercial eucalypt plantations. Other weed control treatments, including hand weeding, sawdust and woodchip mulches, slashing and sowing cover crops did not effectively control weeds and did not improve survival or increase seedling growth to age 2 relative to the control. We conclude that herbicides remain the most cost-effective weed control option available to commercial growers of eucalypt plantations.

219 Alternative Weed Control Methods for Production of Large Container Ornamentals

Non-target herbicide losses pose environmental concerns for nurseries. Therefore, the objective of this research was to determine the ability of each alternative mulch to suppress weed growth when compared to traditional chemical methods. Uniform quart liners of Lagersroemia indica × faurei `Natchez' were planted in 15-gal containers 15 June 1999, on a gravel container pad using overhead irrigation. Weed pressure was uniform. Treatments include Regal 0-0 3 G (3 lb ai/a) as a broadcast or individual container application, recycled newspaper pellets (1 inch thick), Spin-out coated recycled newspaper pellets (1 inch thick) geotextile disks (Spin-out coated), kenaf mulch, waste tire crumbles, wheat straw (2 inches thick), oat straw (2 inches thick), cereal rye straw (2 inches thick), paper mill sludge (2 inches thick), a handweeded control, and a weedy control. Treatments were organized in a RCBD consisting of eight single-plant replicates. The geotextile disks, newspaper pellets treated with spin-out, and shredded rubber tire treatments all had better than 80% weed control from 30 to 180 DAT. These alternative weed control methods can provide a good alternative to conventional weed control practices in large container-grown ornamental.

Alternative Methods of Weed Control in Apple Orchards

Alternative Methods of Weed Control in Apple Orchards

Cover crops and interrow tillage for weed control in short season maize ( Zea mays)

Weed competition can cause substantial maize ( Zea mays L.) yield reductions. Interseeding maize with cover crops or a combination of interrow cultivation and interseeded cover crops are possible alternative methods of weed control. This study was conducted to examine the potential of interrow cultivation plus cover crops to reduce weed density in maize without reducing the grain yield. Field experiments were conducted in 1993 and 1994 at two sites in Québec to determine the effects of planting 12 cover crops with maize on weed control. Fall rye ( Secale cereal L.), hairy vetch ( Vicia villosa Roth), a mixture of red clover ( Trifolium pratense L.) and ryegrass ( Lolium multiflorum Lam), a mixture of white clover ( Trifolium repens L.) and ryegrass, subterranean clover ( Trifolium subterraneum L.), yellow sweet clover ( Meliotus officinalis Lam), black medic ( Medicago lupulina L.), Persian clover ( Trifolium resupinatum L.), strawberry clover ( Trifolium fragiferum L.), crimson clover ( Trifolium incarnatum L.), alfalfa ( Medicago sativa L.), and berseem clover ( Trifolium alexandrinum L.) were seeded at two planting dates, 10 and 20 days after maize emergence. Interrow cultivation was carried out weekly until forage seeding, with a final cultivation being conducted just prior to cover crop seeding. Cover crop planting date did not affect maize yields or the ability of interrow tillage plus cover crops to suppress the development of weed populations. Maize yield was less affected by the interseeded cover crops under conditions of adequate rainfall. Corn planted in fields heavily infested with weeds resulted in substantial yield reductions even when rainfall was adequate. Except for 1993 at l'Assomption interrow tillage plus cover crop treatments had consistently lower weed biomass when compared to the weedy control. Most of the weed control was due to the interrow cultivation performed prior to seeding of the cover crops. The lowest weed density occurred in the herbicide treated plots. The ability of interrow tillage plus cover crops to suppress the development of weeds was affected by the level of weed infestation, the growing conditions and location. The cover crops provide additional weed control but the interrrow tillage or some herbicide application may still be necessary.

Future alternatives to the use of herbicides in British forestry

Weed control is often crucial for successful tree establishment in British forestry. Herbicides currently offer the most cost-effective means available for achieving this, but research into alternatives is required. Recent experiments have been conducted by the Great Britain Forestry Commission investigating the use of 19 alternative ground cover and silvicultural treatments for newly planted ash (Fraxinus excelsior L.) and Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) established on fertile lowland ex-agricultural sites. Most ground cover treatments proved difficult to establish and were more competitive to trees than naturally occurring vegetation. White clover (Trifolium repens L.) showed some potential for suppressing weed vegetation without reducing tree growth. Closer initial tree planting densities appeared to offer a practical means of reducing herbicide inputs, whilst still permitting good rates of growth. It is concluded that a comprehensive review of other alternative methods of weed control is now required to set a framework for future Great Britain Forestry Commission research in this field.

Time of hilling and interseeding affects weed control and potato yield

The current emphasis on reducing pesticide use has led to increased interest in alternative weed control methods. The purpose of this study was to evaluate the potential of hilling, in combination with subsequent interseeding of cover crops, to control weeds in potato and to determine the impact of these actions on potato yield and insects. Each cover crop, either hairy or lana vetch, oats, barley, red clover, or a combination of oats and hairy vetch, was interseeded, following hilling, 3, 4, or 5 wk after planting (WAP). Hilling and interseeding treatments were compared to a no-cover treatment and a chemical standard, metolachlor (1.7 kg ai ha−-1) plus linuron (1.7 kg ai ha−-1). Cultivation associated with the interseeding operation and cover crops reduced weed density 20 to 27% by 3 wk after interseeding. To prevent excessive competition, cereals interseeded 3 or 4 WAP and vetches interseeded 3 WAP were controlled at a height of 25 to 35 cm using fluazifop (0.22 kg ai ha−-1) plus metribuzin (0.28 kg ai ha−-1). Because of slow growth, it was necessary to control red clover (interseeded 3 WAP), only in 1996, at a height of 15 cm. Control of cereals resulted in a dead mulch that provided 0 to 95% weed control, whereas legumes regrew after herbicide application and provided 45 to 70% weed control. However, an adequate minimum of 70% weed control was achieved only with the chemical standard, cereals (1995 and 1996), and legumes (1996) interseeded 3 WAP when controlled with herbicides. In a dry season (1995), potato yields were highest with the chemical standard, whereas in a season with adequate precipitation (1996), potato yields equivalent to those of the chemical standard were obtained with early interseeding (3 WAP) of cereals. The observed changes in the densities of potato leafhopper and of its natural enemies were unlikely to have any effect on potato yield because of low overall insect populations. Thus, the results suggest that in good growing conditions, early (3 WAP) interseeding of cover crops supplemented with postemergence herbicides may both suppress weeds with 70% less herbicide (ai ha−-1) and provide yields comparable to those associated with conventional potato production.

Effect of Age of Cocomposted MSW And Biosolids on Weed Seed Germination

The influence of municipal solid waste (MSW) and biosolids compost maturity on germination of several weed species seeds was evaluated. Ivyleaf morning glory (Ipomoea hederacea L.), barnyard grass (Echinochloa crus-galli L.), common purslane (Portulaca oleracea L.), and corn (Zea mays L.) were selected as plant indicators to determine the compost maturity stage with maximum germination inhibition. Extracts were prepared from immature (three day-old, four week-old, eight week-old), and mature (one year-old) composts. Extract from eight week-old compost decreased percentage germination, root growth, and germination index (a combination of germination percentage and root growth), and increased mean days to germination of each indicator specie. Extract from eight week-old compost was evaluated for effect on germination percentage of 14 economically important weed species. Extract from eight week-old compost inhibited germination of most weed species, except yellow nutsedge (Cyperus esculentus L.) for which tubers were used as propagules. Extracts from immature (three day, four week, and eight week-old) compost with acetic acid concentrations of 2474, 1790, and 1776 mg·kg−1, respectively, delayed and reduced germination percentage of important economic weed species. These results suggest that immature MSW-biosolids compost might be utilized as an alternative method of weed control in the alley-ways of row crops.

Crop Rotation Effects on Sweet Potato Yield and Quality

As the suite of fungicides, pesticides, and fumigants available to vegetable producers continues to shrink, growers may begin to reexamine crop rotations as an alternative method of disease, weed, and pest control. Although many studies have examined field crop rotations, relatively few have examined a vegetable crop as a part of that rotation. In 1985 a study was initiated to evaluate the effect of various crop rotations on sweet potato (Ipomoea batatas L.) yield and quality. Specific rotations were: (i) continuous sweet potato, (ii) sweet corn (Zea mays L. var. rugosa) and sweet potato, (iii) soybean [Glycine max (L.) Merr.] and sweet potato, (iv) 2 yr sweet corn and one yr sweet potato, (v) 2 yr bahiagrass (Paspalum notatum Flugge.) and 1 yr sweet potato, and, (vi) soybean, sweet corn and sweet potato. Two complete cycles (1988-1990 and 1991-1993) of the rotations were analyzed. The crop rotation producing the largest annual yield (4.70 tons/acre) and one of the largest cumulative (11.35 tons/acre) sweet potato yields was 2 yr of bahiagrass followed by sweet potato. Continuous sweet potatoes produced the lowest annual (2.12 tons/acre) and one of the highest total marketable cumulative yields (11.39 tons/acre) during the 6 yr. In general, a rotation containing a grass (bahiagrass, sweet corn) produced higher annual sweet potato yields than those without.

A Comparison of Alternative Weed Management Strategies for Field-grown Specialty Cut Flowers in Maine

A 2-year field study was initiated in May 1994 to show the effects of alternative weed control methods on weed suppression and cut flower yield. Cultural and economic analyses evaluate the feasibility of various management decisions. Gomphrena globosa cv. Woodcreek Pink seedlings were transplanted at 12-inch spacings with the following treatments: 10 mm chopped straw mulch, 10 mm shredded paper mulch, 1.25 mm black plastic mulch, bare soil with postemergent herbicide (Glyphosate) and bare soil with hand weed control. First-year results of the study show weed control was statistically equal between plastic, herbicide, and hand control. These methods provided significantly better barriers to weed growth than shredded paper and oat straw. Economic analyses show variation in the cost efficiency of these methods, however. It is expected that the results of the first year will be corroborated in 1995 for the herbicide, hand control, and plastic treatments, but will reflect change in the chopped straw and shredded paper treatments due to improved focus on experimental design and material selection.

Energy analysis of tillage and herbicide inputs in alternative weed management systems

In view of the movement toward alternative weed management systems in crop production, the authors analyzed the energy efficiency of tillage practices and herbicide use in alternative systems featuring reductions in tillage and/or herbicide inputs. These systems were from an experimental trial near Elora, Ontario and a farm survey in southern Ontario, Canada. Because weed management represented only 20–25% of the annual energy cost for systems using synthetic herbicides and fertilizers, modifications in fertilizer use are more important for energy conservation than weed management. However, energy was conserved in alternative weed management systems by elimination or reduction strategies for tillage and/or herbicide use. Eliminating tillage was more energy efficient than eliminating herbicide use, and resulted in the two lowest energy budgets for weed control among the 12 farms surveyed. Elimination of herbicide use could conserve energy and maintain acceptable yields, particularly in conjunction with farmer experience, and were associated with the use of organic fertilizer and a smaller proportion of energy-intensive crops such as corn. Low-input systems in which tillage and/or herbicides were reduced but not eliminated were more efficient in converting energy into yield than high-input systems, provided that other inputs substituted for reduced inputs (e.g. mechanical inputs instead of chemical inputs) were used in moderation. Thus, most alternative methods of weed control (e.g. reduced herbicide and tillage inputs) are more energy efficient than conventional weed control practices (e.g. broadcast application of herbicides at recommended rates).

Frequency of post-emergence harrowing effects wild oat control and spring wheat yield

Crops grown by organic producers or others choosing not to use herbicides require alternative weed control methods. In a 3-yr study at Scott, Saskatchewan, several harrowing frequencies were applied to emerged wild oats infesting spring wheat. Two passes with diamond tooth harrows at the one- to two-leaf stage of wild oats reduced panicle density and fresh weight in 2 of 3 yr. Multiple harrowings reduced wheat culms, fresh weight, and yield in 2 of the 3 yr. In 1992, four harrowings reduced wheat culms and yield, but had no effect on wild oat. In 1993, two harrowings reduced wild oat panicles and fresh weight, but had no effect on wheat culms and fresh weight, suggesting that moisture conditions at and immediately following harrowing have a differential effect on the ability of the two species to recover. Key words:Avena fatua L., Triticum aestivum L., cultural control, organic production

The tolerance of spring wheat and barley to post-emergence harrowing

Use of herbicides in certain situations may not always be appropriate for controlling weeds because of cost or improper crop stage. Crops produced without the use of herbicides require alternative weed-control methods. A 12-yr study was conducted at Indian Head, Saskatchewan, under weed-free conditions to determine the tolerance of spring wheat and barley, with or without ammonium phosphate fertilizer placed with the seed, to post-emergence harrowing. Barley and spring wheat harrowed with diamond-toothed harrows as it was emerging, at the 1.5-leaf stage, or at the 2.5-leaf stage in the absence of weeds produced yields similar to those from a non-harrowed check when averaged across years and fertilizer treatments. Ammonium phosphate fertilizer placed with the seed significantly increased yields of both barley and spring wheat (averaged across years and harrowing treatments) but did not alter the tolerance of barley and spring wheat to post-emergent harrowing. This implies that a delay between seeding and harrowing due to rain or using a harrowing operation to break a surface crust should not result in yield losses for barley and spring wheat.Key words: Triticum aestivum L., Hordeum vulgare L., cultural control, organic production phosphorus

Subterranean clover living mulch: an alternative method of weed control

An alternative method to using herbicides in some crops may be the use of subterranean clover ( Trifolium subterraneum L.) as a living mulch for weed control. Subterranean clover is a self-seeding winter annual legume with a geocarpic type of growth for which it is also known as ‘subclover’. From 1986 to 1990 subterranean clover was used in our research with success in several agronomic and vegetable crops. Our initial work was with field corn ( Zea mays indentata L.). Included in this experiment were treatments of subterranean clover living mulch, rye ( Seacale cereale L.) dead mulch, and no-mulch. Included also were several tillage treatments superimposed on the mulch treatments. These were conventional, minimum, and no-tillage. We later included soy beans [ Glycine max (L.) Merr], sweet corn ( Zea mays saccharata L.) and several vegetables such as summer squash ( Cucurbita pepo L.), spring cabbage ( Brassica oleracea capitata L.), snap beans ( Phaseolus vulgaris L.), and tomatoes ( Lycopersicon esculentum Mill) in our research. We found that subterranean clover used as a living mulch in a no-tillage system provided excellent weed control in all experiments without the use of herbicides. All living mulch-tillage treatments reduced greatly weed biomass. Treatments without subterranean clover living mulch, including the conventional tillage-herbicide treated checks, had higher weed biomass. Yields of corn, sweet corn, cabbage, snap beans and tomato were not adversely affected by the subterranean clover living mulch.

Integrated Weed Management: The Rationale and Approach

A growing awareness of environmental issues in Canada has had a major influence on government policies. An initiative was launched by the government of Ontario to promote research toward the development of an integrated weed management (IWM) system. Research in IWM must take all aspects of the cropping system into consideration and evolve in a progressive manner. This approach must encompass the role of conservation tillage, knowledge of the critical period of weed interference, alternative methods of weed control, enhancement of crop competitiveness, modeling of crop-weed interference, influence of crop rotation and seed bank dynamics, and education and extension of the findings. The complexity involved in addressing these issues requires a multi-disciplinary approach.

Herbicide Applications in Tillered Winter Wheat for Doublecrop Soybean Weed Control1

AbstractEffective, doublecrop soybean [Glycine max (L.) Merr.] weed control usually requires a foliar‐active herbicide to control emerged weeds and one or two residual herbicides to control those that emerge after planting. This combination is expensive in relation to the narrow profit margin frequently experienced. If timely rainfall does not occur shortly after application, poor weed control may occur, resulting in reduced soybean yields. Field studies were conducted on a Weir silt loam (fine, montmorillinic, mesic Typic Ochraqualfs) to evaluate alternative methods of herbicidal weed control in doublecrop soybeans.Oryzalin (3,5‐dinitro‐N4, N4‐dipropylsulfanilamide) and USB 3153 (N3,N3‐di‐N‐propyl‐2,4‐dinitro‐6‐trifluoromethyl‐M‐phenylenediamine) applied after the winter wheat (Triticum aestivum L.) was fully tillered but prior to the jointing stage (full‐tiller) did not cause any visual injury or yield reduction any of the 3 years of the study. Oryzalin at 2.8 kg/ha in 1976 and at 1.68 kg/ha in 1977 and 1978 controlled at least 85% of all weeds and volunteer wheat in the doublecrop soybeans that followed the wheat harvest. USB 3153 applied at 1.12 kg/ha in 1977 controlled more than 85% of the large crabgrass [Digitaria sanguinalis (L.) Scop.], ivyleaf morningglory (Ipomoea hederacea), and Pennsylvania smartweed (Polygonum pennsylvanicum L.) but common ragweed (Ambrosia artemisiifolia L.) and volunteer wheat control was not acceptable (<80%). In 1978, USB 3153 at 0.84 and 1.12 kg/ha controlled 95% or more of all weeds and volunteer wheat. Herbicides applied after doublecrop soybean planting provided acceptable weed control in 1976 and 1977 but poor control in 1978. These results indicate that oryzalin and USB 3153 applied over‐the‐top of tillered wheat provide good weed control in doublecrop soybeans and do not affect wheat yields at rates needed for acceptable weed control. Similar studies are needed at other locations to fully evaluate these treatments under different soil and environmental conditions.

Selecting Appropriate Weed Control Systems for Developing Countries

Herbicides can increase agricultural productivity and rural welfare where agronomic considerations or labor shortages favor their utilization, but ecological, social, and economic conditions in developing countries often favor alternative weed control methods. Traditional hoeing by peasant farmers in a Northeast Brazil upland region was found to be both effective and economical in comparison with other methods. In another Northeast Brazil region, government herbicide subsidies and payroll taxes were projected to encourage excessive use of herbicides at the expense of displaced workers with few alternative employment opportunities.