Avena fatua (wild oat)

There are some effective non-chemical methods for controlling A. fatua. These are mainly soil cultivation and crop rotation. The most effective non-chemical control was achieved by the shallowest cultivation possible, carried out as late as possible (Zorner et al., 1984). Tine cultivation, besides favouring increase of an uncontrolled population, results in a faster population decline than ploughing (Wilson and Cussans, 1983). Depth of burial and crop rotation influence the seed bank (Froud-Williams, 1987). Peters (1991) found no viable seeds after 3 years of intensive soil tillage. Under zero tillage the numbers of A. fatua are generally reduced, but the control of surviving plants with herbicides can be less effective (Bowren, 1983). Summer treatment of soil after cereal harvest (stubble ploughing, summer deep tillage and spring seed-bed preparation), which buries A. fatua seeds, can create good conditions for weed seed germination and help to markedly reduce weed seed banks (Demo, 1999). Palys et al. (1999) reported that direct sowing and no ploughing caused the greatest increases in the densities of A. fatua in a faba bean/winter wheat/spring barley rotation prior to harvest. Post-harvest soil cultivation can promote weed seed germination and emerged weeds can be controlled with glyphosate prior to drilling. This treatment combined with a pre- or post-emergence herbicide programme resulted in reduced numbers and a decline in A. fatua over a 4-year period (Hutcheon et al., 1998). Straw burning kills many seeds and reduces the dormancy of survivors (Ivens, 1978; Moss, 1985). In contrast, stubble cultivations have a smaller effect on the germination of A. fatua (Cussans et al., 1987). Delayed sowing results in a consistently high degree of A. fatua control but can also result in significant losses in grain yield and quality (Hunter, 1983). In many cases farmers have had to seek alternative methods in their control of A. fatua. In a study on the LIFE pilot farm in the UK, the presence of the wild oats in such abundance caused a switch to spring cropping of oilseed rape and peas in addition to a ley period of 1 year grass-clover mix (Davies et al., 1997). In cereal crops, reducing the seed bank of weed seeds is the optimum control method. This can be done through changes in the crop sequences (Malik et al., 1996).Schoofs and Entz (2000) reported forage systems (e.g. triticale) were at least as effective as the sprayed wheat control in suppressing wild oat. In contrast to these indirect control methods there are only a few non-chemical measures for direct control of A. fatua. Mechanical methods are mostly less successful because of the large seed and dense root system (Koch and Hurle, 1978). Nevertheless, harrowing or hoeing may break dormancy and therefore increase late emergence (Raju et al., 1988). A. fatua and other grasses are not susceptible to thermal control methods (Ascard, 1995). However, a flame weeder used in an onion crop resulted in 31-93% control of A. fatua (Mojzis, 2002). Tsuruuchi (1986) reported that emergence of A. fatua in wheat and barley can be reduced by flooding. Soil solarization is used in Israel, the USA, Italy and India (Arora and Yaduraju, 1998) to control A. fatua as well as other weeds and pests (Cartia, 1985). Composting has been found to kill weed seeds (Tompkins et al., 1998). In an experiment conducted using feedlot manure containing 12 weed species of which A. fatua was one, composting reduced the viability drastically within two weeks and killed all seeds within four weeks (Tompkins et al., 1998).Olson et al. (1999) found that shoot extracts and living tissue extracts from wheat (Triticum aestivum) resulted in a significant decrease in total biomass, pigment, carbohydrate and protein content of A. fatua. In a field trial in Pakistan, sorghum water extract reduced the density and biomass of A. fatua by 22-27% (Cheema et al., 2002). Parthenin, a natural extract from Parthenuim hysterophorus reduced germination of A. fatua and inhibited shoot and root growth (Batish et al., 2002). In a study on the allelopathic effects of Triticum speltoides (a wild relative of wheat), one out of 17 accessions were found to reduce the radicle length of A. fatua by 50% (Hashem and Adkins, 1998).Enhanced crop competition can also reduce the growth and yield reduction effect of A. fatua. Increasing the sowing rate of five varieties of barley improved the competitiveness of all varieties as evidenced by reduced wild oat shoot dry matter and seed production and, in some cases, improved barley yields (O'Donovan et al., 2000a). In field trials in Canada, hybrid rape varieties were twice as competitive against A. fatua as open-pollinated varieties (Zand and Beckie, 2002). Xue and Stougaard (2002) showed that the combined effects of large seed size and increased wheat sowing rate could decrease A. fatua biomass and seed production by 20%.A commercially available smoke-water solution has also been shown to stimulate the germination of A. fatua (Adkins and Peters, 2001).

Few papers have been published concerning biological approaches for controlling A. fatua. They are resultant of fungal infections such as those by Erysiphe graminis f.sp. avenae (Sabri and Clark, 1996; Sabri et al., 1997), Puccinia coronata (Chong and Seaman, 1996, 1997; Salmeron-Zamora et al., 1996; Johnston et al., 2000), P. coronata f.sp. avenae (Carsten et al., 2000), P. graminis (Harder and Anema, 1993), P. recondita (Pfleeger et al., 1999), Pyrenophora (Kastanias and Chrysayi Tokousbalides, 2000), nematodes (Riley and McKay, 1991) or hydroxamic acids that have allelopathic effects (Perez, 1990). A. fatua is generally susceptible to the same range of parasites as cultivated oats (Sharma and van den Born, 1978). Research into fungal pathogens for the biological control of A. fatua is occurring in many countries including Vietnam (Hetherington et al., 1996), Australia, USA, Netherlands, Japan and South Africa (McRae, 1998).A. fatua has been confirmed, via virological analysis, to be a natural host plant for the Oat blue dwarf virus (Vacke, 1998). The majority of host plants identified in this study exhibited characteristic symptoms of the infection. Another pathogen, Drechslera avenacea, was identified and isolated and found to be specific to A. fatua over wheat (Zhang and Li, 1996) and has been investigated as a potential bioherbicidal organism for A. fatua (Hetherington et al., 2002). Chong and Seaman (1997) isolated 101 virulence phenotypes from 189 isolates from A. fatua and commercial field oats in Manitoba and Ontario, Canada. Hot dry weather was seen to slow the infection of the fungus. The effect of Erysiphe graminis f.sp. avenae on the photosynthesis and respiration of A. fatua was studied by Sabri et al. (1997). It was evident from these studies that E. graminis [Blumeria graminis] reduced levels of photosynthesis and chlorophyll. In a comparison of wild oats with cultivated crops in their tolerance to B. graminis it was seen that the wild oats were significantly more tolerant, due to the lower sensitivity of their metabolism to B. graminis (Sabri and Clarke, 1996).The ant species Messor barbarus has been shown to preferentially predate A. fatua seeds (Detrain and Pasteels, 2000).

Herbicide weed control of A. fatua has been found to be more effective than cultural control (Stevenson et al., 2000a) and many herbicides have been successfully used (Milne, 1997). Good levels of control are given by herbicides belonging to the urea family (e.g. isoproturon or chlorotoluron) and phenoxypropionates (e. g. diclofop-methyl). In a review by Fisher and May (2000), advice is given for the chemical control of A. fatua, along with a list of new herbicide registrations for 2000. Zahradnicek and Kohout (1996) also examined various graminicides for use against wild oats in sugarbeet crops.Many selective herbicides sprayed alone, in mixtures or sequences are known for their high efficacy against A. fatua. These include the following: atrazine (Stork, 1998), benzoylprop-ethyl, chlorsulfuron, chlorotoluron, clethodim (Szilvasi, 1996), clodinafop, cycloxydim, diclofop-methyl (Balyan and Malik, 1996; Koscelny and Peeper, 1997; Troccoli et al., 1997; Fayed et al., 1998), difenzoquat, diflufenican, dimethenamid + trifluralin (Soliman et al., 1998), fenoxaprop-ethyl (Koscelny and Peeper, 1997; Fayed et al., 1998; Mathiassen and Kudsk, 1998), flamprop-isopropyl (Fayed et al., 1998), fluazifop-P-butyl, fluoroglycofen (Lueschen et al., 1997; Hutchinson et al., 1999), flucarbazone sodium (Kirkland et al., 2001), haloxyfop-P-ethoxyethyl, imazamox (Lueschen et al., 1997; Hutchinson et al., 1999), imazamethabenz (Hsiao et al., 1996; Koscelny and Peeper, 1997; Wille et al., 1998), isoproturon (Angiras and Vinod Sharma, 1996; Balyan and Malik, 1996; Pandey et al., 1996), linuron, linuron + monolinuron + fluazifop-butyl (Soliman et al., 1998), methabenzthiazuron, oxyfluorfen (Arnold et al., 1998), pendimethalin (Pandey et al., 1996), pirifenop-N-butyl, propaquizafop (Gimenez-Espinosa et al., 1997; Gimenez Espinosa et al., 1999), pyridate (Gimenez Espinosa et al., 1999), quizalofop-ethyl, rimsulfuron, sethoxydim, sulfometuron (Arnold et al., 1998), sulfonylaminocarbonyl, triazolinone (Santel et al., 1999; Scoggan et al., 1999), terbutryn (Balyan and Malik, 1996; Fayed et al., 1998), tralkoxydim (Balyan and Malik, 1996; Fayed et al., 1998; Belles et al., 2000; Stevenson et al., 2000b), tri-allate and tria-allate sulfoxide (Kern et al., 1996) and trifluralin (Lueschen et al., 1997; Scursoni and Satorre, 1997). Several herbicides derivatives have been examined for potential use in wild oat control. A herbicide called CGA184927 (2-proponyl(R)-2-(4-(5-chloro-3-fluoro-2-pyridinyloxy)-phenoxy)-propionate/5-chloro-8-quinolinoxyacetic acid-1-methylhexylester) was evaluated in its efficacy of A. fatua control (Blackshaw and Harker, 1996). It was evident that CGA184927 is sensitive to environmental conditions as the application rate needed to produce >90% control over several years varied from 22 to 90 g/ha. This herbicide was also compatible in tank mixes with bromoxynil, clopyralid and 2,4-D ester, whereas tank mixing with metsulfuron or dicamba reduced the effectiveness in controlling wild oats. Examination of other derivatives found that derivatives of 2-[4-(3,5-dichloro-2-pyridyloxy) phenoxy] propionamidoxyacetic acid to show selectivity between oats and wheat and N-ethyl-2-[4-(3,5-dichloro-2-pyridyloxy) phenoxy] propionamidoxyacetamide to have a higher herbicidal action than diclofop-methyl while retaining similar selectivity (Matsumoto et al., 1996).A new cyclohexanedione herbicide, tepraloxydim, provided effective control of A. fatua in broadleaf crops in Poland (Stachecki and Krawczyk, 2002). A new additive, consisting of the pyrimidine allopurinol and molybdenum trioxide, formulated in 50% monolaurate, was found to boost the activity of sulfosulfuron used mainly for the control of wild oats (A. fatua). This increased activity led to the effective control of wild oat populations which are not normally controlled by the herbicide (Cairns et al., 2001)Chao et al. (1997) examined whether the efficacy of imazamethabenz could be improved when applied to the tillers of wild oats plants. They found that the presence of tillers neither improved nor decreased the efficacy of imazamethabenz. Hsiao et al. (1996) found that when imazamethabenz was tank mixed with 1 and 2% ammonium sulphate, the phytotoxicity of the herbicide was increased when applied to A. fatua at the 2 to 3 or 3 to 4 leaf stage. If ammonium sulphate was applied at 10%, the phytotoxicity of the herbicide was reduced. There was also a difference in effects of ammonium sulphate on the herbicide toxicity according to application method (Hsiao et al., 1996).The uptake of some herbicides is also influenced by temperature and moisture levels, which may be important for the successful control of A. fatua (Olson et al., 1999). Control of A. fatua was greater when the temperature after application of MON 37500 (1-(2-ethylsulfonylimidazo[1,2-a]pyridin-3-ylsulfonyl)-3-(4,6-dimethoxypyrimidin-2-yl)urea) was 25/23°C or soil moisture was at full pot capacity compared to when the temperature was at 5/3°C or soil moisture was at one-third pot capacity (Olson et al., 2000). Holm et al. (2000) found the optimal graminicide rate depended on the level of A. fatua infestation and the best time to control A. fatua depended upon the type of graminicide. Xie et al. (1996) found that water stress influenced the phytotoxicity of herbicides. Adkins et al. (1998) examined the efficacy of glyphosate on wild oats in relation to soil moisture content, irradiance, temperature and relative humidity and found that the efficacy was greatest under well-watered, warm (30/25°C) and humid (>92/90%) conditions and was not altered by irradiance. Xie et al. (1996) also found that in A. fatua, fenoxaprop-ethyl and imazamethabenz-methyl absorption is affected by temperature and irradiance. There was an increase in absorption with higher temperatures of 30/20°C and under 70% shading, the phytotoxicity of both the herbicides was enhanced. Sharma et al. (1996) also examined herbicide application and found that the distribution of the herbicides was dependent on the content and concentration of the surfactant and the surface characteristics of the herbicide droplets.The uptake of diclofop-methyl in A. fatua was higher after root application compared to foliar application, whereas the uptake of fenoxaprop-p-ethyl after foliar application was lower than that for diclofop but greater if applied to the roots (Dahroug, 1996). The translocation of these herbicides was faster from roots to shoots.Stevenson et al. (2000b) found that the efficiency of tralkoxydim in controlling A. fatua in Canada was affected by the rate of herbicide application, water volume, spray mixture pH, diurnal application time and sodium bicarbonate concentration of the water source. At Scott, the negative effects of tralkoxydim rates lower than 200 g/ha applied with 50 or 1000 L of water per hectare on wild oat fresh weight were most apparent when applications were made in the morning, especially with an unbuffered spray mixture. However, at Saskatoon, spray mixture pH or time of application did not modify the effects of tralkoxydim rate and water volume on wild oat fresh weight.When plants are stressed the phytotoxic effects of herbicides are often diminished. A study in Canada (Xie et al., 1997a) demonstrated that when A. fatua was subjected to drought conditions or drought and high temperatures, the reduction in phytotoxicity was most evident following fenoxaprop and diclofop applications. Flamprop and imazamethabenz also had reduced phytotoxicity but to a lesser degree. It appeared that imazamethabenz was mostly affected by high temperatures, whereas fenoxaprop was mostly affected by drought. However, the combination of both drought and high temperatures was sufficient to markedly reduce the efficacy of all herbicides examined. The phytotoxicity of herbicides can be increased by the addition of surfactants (Xie et al., 1997b); ammonium sulphate ([NH4]2SO4) in the case of fenoxaprop; sodium bisulphate (NaHSO4) for imazamethabenz (Xie et al., 1997b); methylated seed oil and urea ammonium nitrate with quizalofop (Stougaard, 1997) and specific temperatures (Xie et al., 1997a, b). The combination of methylated seed oil and urea ammonium nitrate with quizalofop enabled greater than 90% control when the quizalofop was applied at the lowest level of 20 g/ha (Stougaard, 1997).Alternative methods to broadscale spraying to control weeds have been examined. In the UK patch spraying to control wild oats in wheat crops have been developed (Lutman et al., 1998). Herbicide resistance has evolved in response to intense selection pressure (a result of high herbicide application frequencies and efficacy) (Morrison et al., 1996). O'Donovan et al. (2000a) found that the evolution of resistance was positively correlated with the number of triallate or difenzoquat applications over a 9 year period. To delay the onset of herbicide resistance, repeated usage of the same herbicide or group (mode of action) should be avoided and wherever possible, integrated use of alternative control strategies is recommended (Morrison et al., 1996).Herbicide resistance has been reported in A. fatua to the following active ingredients: tri-allate in Canada (Thai et al., 1985; Morrison and Devine, 1994; Blackshaw et al., 1996; Kern et al., 1996; Beckie and Jana, 2000; O'Donovan et al., 1996, 2000b) and the USA (O'Donovan et al., 1994; Davidson et al., 1996; Kern et al., 1997), diclofop-methyl in America (Seefeldt et al., 1996b, 1998), Australia (Powles and Holtum, 1990; Mansooji et al., 1992), Canada (Devine et al., 1993) and in South Africa (Malik et al., 1996), difenzoquat in Canada (O'Donovan et al., 2000b), sethoxydim in Canada (Maurice and Billett, 1991), fluazifop in Australia (Mansooji et al., 1992), fenoxaprop-ethyl (Devine et al., 1993; Cavan and Moss, 1997), and imazamethabenz in Canada (Heap, 1997; Friesen et al, 2000) and America (El-Antri and Nalewaja, 1997), flamprop and fenoxaprop-P in Canada (Friesen et al., 2000), imazamethabenz-methyl (Nandula and Messersmith, 2000), and difenzoquat (O'Donovan et al., 1994; Kern et al., 1996; Rashid et al., 1997), diallate (Kern et al., 1996), tralkoxydim (Marshall et al., 1996; El-Antri and Nalewaja, 1997; Cocker et al., 2000) in the USA and EPTC (Rashid et al., 1997). Up-to-date records of the extent of herbicide resistant A. fatua populations are given by Heap (2003).Several surveys have been conducted across Canada to assess the distribution of herbicide resistant A. fatua (Beckie et al., 1998, 1999b; Beckie and Juras, 1998). Resistance to aryloxyphenoxypropionic acids has been reported in France (Letouze et al., 1997) and the UK (Cocker et al., 2000) and resistance to phenylureas has also been reported in France (Letouze et al., 1997) with some resistant populations surviving more than 100 times the normally lethal dose. Murray et al. (1996) tried to elucidate the inheritance of aryloxypenoxypropionate resistance in different populations exhibiting different cross-resistance patterns and found that the resistance in both populations is encoded at the same gene locus. In Montana, USA, triallate resistance was surveyed and found to constitute 94% of all patches/areas in 1993 but this declined to 77% in 1995 (Davidson et al., 1996). Management strategies were said to have an important role in the pattern of dispersal. Blackshaw et al. (1996) examined triallate resistant populations in Alberta, Canada, and found that they could be controlled by atrazine, ethalfluralin, fenoxaprop-p, flamprop, imazamethabenz and tralkoxydim but that integrated weed management practices should also be implemented. Kern et al. (1997) examined several triallate resistant lines of A. fatua to determine the effects on wax and lipid biosynthesis. They found that by greenhouse application of tri-allate, the epicuticular waxes were dramatically reduced as were the elongated fatty acid fractions in susceptible varieties (also reported in Rashid et al., 1997) but not resistant varieties. However, treatment with tri-allate sulfoxide reduced the in vivo concentrations of elongated fatty acids equally in the resistant and susceptible lines. This infers that tri-allate sulfoxide is more inhibitory towards fatty acid elongases than tri-allate. This is turn suggests that in vivo tri-allate sulfoxidation is necessary for herbicidal action and so reduced rates of tri-allate sulfoxidation can confer resistance. Rashid et al. (1997) also examined the effect of tri-allate and difenzoquat on the fatty acid chains. They found results similar to those by Kern et al. (1997) for tri-allate whereas the difenzoquat did not cause any change in the fatty acid composition of susceptible or resistant lines, hence suggesting that fatty acid biosynthesis is not involved in cross-resistance to this herbicide.Having fallow in the crop rotations slowed the rate of evolution of tri-allate resistance in wild oat (Beckie and Jana, 2000). Resistance was not detected in herbicide untreated continuous spring wheat cultivar Neepawa and wheat-fallow plots and herbicide treated wheat-fallow plots. While resistance was not detected in herbicide treated continuous spring wheat cultivar Neepawa plots in 1996, 3% of the seeds screened in 1997 and 14% of the seeds in 1998 were resistant. In 1996, 53.9 and 98.7% of wild oat plants had dormant seeds in the Neepawa and wheat-fallow rotations, respectively. The enhanced dormancy of seed selected by fallow treatment may also have contributed to delaying the evolution of resistance in wheat-fallow.Mechanisms of resistance in A. fatua for diclofop were examined (Seefeldt et al., 1996b). It was evident that resistance could not be attributed to differential absorption, translocation or metabolism of diclofop, nor membrane plasmalemma repolarisation. Cross-resistance to fenoxaprop was also more likely in diclofop-resistant biotypes (Seefeldt et al., 1996b). Baerg et al. (1996) found that tribenuron antagonized diclofop control, which was attributed to a reduction by tribenuron in the basipetal translocation of diclofop to meristematic regions of A. fatua.Multiple herbicide resistance in A. fatua is not rare. Friesen et al. (2000) reported resistance to imazamethabenz, flamprop and fenoxaprop-P in three Avena populations in the north-west agricultural region of Manitoba, Canada. The evolution of herbicide resistance in the absence of direct selection (cross resistance) is a very serious development as producers with resistance to multiple herbicides in A. fatua are left with a very limited number of herbicide options for selective control in crops commonly grown in western Canada (Friesen et al., 2000).Cavan et al. (2001) utilised a model to predict the time required to develop field resistance of A. fatua to aryloxyphenoxypropionate (AOPP) and cyclohexanedione (CHD) herbicides in a number of field situations. The model predicts that plough cultivation could delay the development of resistance relative to tine cultivation and that herbicide rotation can dramatically increase the times required for field resistance to develop in a tine cultivation system. Resistance can be delayed for at least 66 years if three herbicides, each with a different mode of action, are rotated and each herbicide causes 90% mortality in a tine cultivation system. Tri-allate and tri-allate sulfoxide pytotoxicity have been evaluated by comparing the metabolism occurring during growth. Tri-allate metabolised 12 times slower than the resistant populations tested, although the end result was the same. However, tri-allate sulfoxide was metabolised rapidly in both the susceptible and resistant lines (Kern et al., 1996). It was therefore concluded that resistance to tri-allate is the result of reduced rate of formation of the sulfoxide from tri-allate. O'Donovan et al. (1996) developed a bioassay for determining triallate resistance in A. fatua where routine samples suspected of resistance are collected.Modes of resistance to herbicides are largely unknown. In A. fatua the mechanism to the pre-emergent thiocarbamate herbicide tri-allate was examined (Kern et al., 1998). It was found that the metabolism of tri-allate was more than 12-fold slower in the resistant than the susceptible seedlings, suggesting there is a slower rate of tri-allate activation (and slower accumulation) in resistant plants. From this study it was also found that resistance occurs prior to the conversion of tri-allate sulfoxidation to metabolites and that tri-allate sulfoxidation requires two enzymes, both of which need mutations to confer this resistance. Studies to determine the application timing on the efficiency of herbicides on wild oats populations suggested that efficacy was governed by growth stage, weed demographics and environmental considerations (Stougaard et al., 1997).Diclofop can infer differences in the membrane transport and the plasma membrane potential of resistant and susceptible biotypes (Renault et al., 1997). Further evaluation of this showed no differences between herbicide resistant and susceptible biotypes in plasma membrane lipid structure or lipoxygenase (LOX) activity (Renault et al., 1997).The resistance of A. fatua to herbicides is likely to spread rapidly and become a serious problem if farmers do not quickly adopt measures to check its development (Davis, 1992). A study by Greenwood et al. (1999) found that several populations of A. fatua exhibited resistance to different herbicides and at different rates. Investigations into the evolution of herbicide resistance among several populations of A. fatua and A. sterilis ssp. ludoviciana in England, UK, concluded that hybridization had occurred between the species and that resistance had spread from one population to another (Cavan et al., 1998). Rotational strategies for weed control are also likely to be effective in delaying or minimizing the development of herbicide resistance (Martin and Felton, 1993). A survey across northern New South Wales, Australia, identified A. fatua resistance to aryloxyphenoxypropionate herbicides and methods were given to manage herbicide resistant wild oats (Storrie and Edwards, 1998).

The widespread evolution of resistance to herbicides for the selective control of A. fatua highlights the need for integrated weed management strategies that do not rely on herbicides alone. Beckie et al. (2001) discuss proactive and reactive strategies for the management and containment of herbicide-resistant weeds. They suggest greater awareness and consideration of the relative risks of different modes of action to select for resistance, effective herbicide mixtures and the incorporation of management practices that reduce weed seed production and spread. Jones and Medd (1997) estimate the economic benefit associated with an integrated weed management approach for wild oats (A. fatua and A. ludoviciana) in Australia, involving fallow, herbicide and crop rotational options and suggest a population based approach to the control of A. fatua which goes beyond efforts to minimise the effect of A. fatua in any single year. This study and those by Scursoni et al. (1999) and O' Donovan et al. (1999b), confirm the importance of strategies which prevent seed production and deplete the seed bank. In a Russian study by Dudkin (1999), it was concluded that mechanical soil treatments and crop rotations resulted in reduction of A. fatua by depleting the seed bank. Watson et al. (1999) found that the seed bank of A. fatua in the UK was reduced in integrated and conventional wheat after beans during a 7 year rotation. The occurrence of A. fatua in Canada was also effectively suppressed in cereal fields that had previously contained Medicago sativa in crop rotations (Ominski et al., 1999). Inclusion of 75% or more cereals in a crop rotation study by Derylo (1997) resulted in decreased barley yields and increased weed infestation, both in numbers and dry weight of A. fatua. Catch crops reduced weed infestation in spring barley but could not completely compensate for the effect of less desirable crop rotations. Young et al. (1996) writes one of the more thorough reviews on integrated weed management that examines control strategies for A. fatua.Within a barley crop, A. fatua was controlled by a combination of applying trifluralin herbicide (there was no effect of time of application) and conventional planting rather than deep planting pattern (Scursoni and Satorre, 1997). Experiments conducted into the control of A. fatua in rape crops in Canada showed that if high density plantings were used, low rates of quizalofop were required to reduce A. fatua seed production (O'Donovan et al., 1996). Angiras and Vinod Sharma (1996) also examined combinations of bi-directional sowing, row orientation and row spacing in combination with isoproturon for weed control in wheat.Extracts from the residues of crops were trialed to determine whether they had any influence on the control of weed species. Although they were found to control other species, A. fatua was not affected (Moyer and Huang, 1997). Analysis of the various control strategies for the management of wild oats for economic evaluation has determined that out of all the control strategies examined, the most economically beneficial ones are those which involve the removal of the weed seed and the reduction of seed in the soil seed bank (Jones and Medd, 1997). In the UK an ECO-tillage project involving soil preparation to encourage weed germination followed by application of glyphosate prior to drilling has resulted in >50% reduction of the use of herbicides compared to conventional systems with a decline in the numbers and levels of A. fatua over a 4 year period (Hutcheon et al., 1998).