The current Australian sugarcane industry transition towards adoption of an ‘alternative’ herbicide strategy as part of improved environmental stewardship is increasingly complicated by recent farming system, regulatory and herbicidal product changes. This study quantified and compared the efficacy, economic costs and environmental risk profile s of a range of established, emerging, and recently registered pre -emergent herbicides across field trials in the Wet Tropics region of North Queensland. Several herbicides were effective on certain weed species, but lacked broad spectrum control. Better efficacy results from products with multiple active ingredients (i.e., imazapic -hexazinone) demonstrated the benefits of using mixtures of active ingredients to widen the spectrum of weed control efficacy. All tested pre – emergent herbicides behaved quite similarly in terms of their propensity for off-site movement in water (surface runoff losses generally > 10 % of active applied), with their losses largely driven by their application rate . Herbicides with lower application rates consistently contributed less to the total herbicide loads measured in surface runoff. Results demonstrated alternative choices from the more environmentally problematic herbicides (such as diuron) are available with effective alternative formulations providing between 4 and 29 less risk than the traditional diuron -hexazinone ‘full rate’. However, considerable challenges still face canegrowers in making cost -effective decisions on sustainable herbicide selection. Additional research and effective grower extension are required to address information gaps in issues such as specific weed control efficacy of alternative herbicides and potential blending of some herbicides for more effective broad spectrum weed control, while also minimizing environmental risks.

Introduction

The decline of fresh and marine water quality associated with land -based runoff from adjacent agricultural catchments is a major cause of the poor state of many of the coastal ecosystems of Australia’s Great Barrier Reef (GBR) World Heritage Area (Waterhouse et al., 2017). Pesticides have been specifically identified as among the most important diffus e source pollutants from catchment areas of the GBR (Brodie et al., 2012). High value freshwater, estuarine and inshore waters of the GBR lagoon are regularly exposed to pesticide runoff from agricultural lands, particularly during wet season riverine flood events (December to April) (e.g. Lewis et al., 2009 ; Davis et al., 2012). The pesticides that have been most commonly detected in the GBR lagoon are herbicides that inhibit electron transport at photosystem II (PSII) in plants and include diuron, atrazine, hexazinone, ametryn, simazine and tebuthiuron (Haynes et al., 2000a ; Shaw and Müller, 2005 ; Shaw et al., 2010). Concentrations during elevated stream flow events can at times exceed ecological water quality protection guideline trigger values for up to several weeks for some of these PSII herbicides (Lewis et al., 2009 ; 2012 ; Brodie et al., 2012 ; Davis et al., 201 3 ; O’Brien et al., 2016; Novic et al., 2018).

Viable seeds of numerous plant species are not capable of germinating immediately after harvest under conditions suitable for the germination process. Such seeds are termed primarily dormant. Primary dormancy is established during seed development and maturation on the mother plant. This type of dormancy is particularly common in wild plants. Dormancy is a very important phenomenon which prevents germination on mother plants, facilitates seed dispersal, ensures plant survival of natural catastrophes, and reduces intra-specifc competition (Bewley et al. 2013). The phenomenon has turned out to be non-obligatory, its expression depending on environmental factors, e.g., temperature. Seeds can be fully dormant; such seeds are not able to germinate at any temperature (Hilhorst 2007). There are also seeds which are not capable of germination only within a certain temperature range, whereas they germinate at temperatures outside that range. Thus, the expression of dormancy in such seeds depends on temperature, and dormancy release is associated with widening the range of germination temperature. Under natural conditions, primarily dormant seeds are exposed to fuctuating environmental conditions, e.g., light, temperature, moisture, and the presence of gases, which leads to dormancy state cyclicity (Finkelstein et al. 2008). Primary dormancy can be removed also by cold stratifcation, dry storage, light, or chemicals (Bewley et al. 2013). It is commonly accepted that the balance between abscisic acid (ABA) and gibberellins (GAs) and/or sensitivity to these hormones are responsible for regulation of the dormancy state and germination of seeds in response to environmental signals (Finkelstein et al. 2008; Rodríguez-Gacio et al. 2009). ABA is considered as the most important hormone responsible for the establishment of dormancy during seed development and for maintenance of dormancy during seed imbibition. In turn, GAs have been cited as factors involved in dormancy release and/or germination. Dormancy release has been shown as involving a decline in the ABA content and an increase of the GAs level (Bewley et al. 2013).

Ecologists have recognized two important successions: initial succession, which is the occurrence of ecosystem expansion on the sites that have not been previously occupied by living organisms (such as bare rocks and frozen surfaces); and secondary succession, which happens in the ecosystems, which have been previously occupied by organisms. Tilled felds, clear-cut forests, and burned areas are all exposed to secondary succession (Letcher 2010; Podda et al. 2011; Rezvani et al. 2013). During the succession, vegetative variations are not coincidental, and spread of vegetation is regularly carried out with the following functional variations (Dölle et al. 2008; Schmid et al. 2017). The early stages in succession include species, which have light seeds (Rockwood 1985), high seed production (Hyatt and Casper 2000), extensive distribution (Samuel and Hart 1994), and rapid growth rate (Lambers et al. 2008). Species with large seeds have longer life period, meaning they are more competitive and dominant in the fnal stages of succession (Fenesi et al. 2014). In such stages, perennial weed species replace the annual ones (Corbin and D’Antonio 2004) in a period of one (Brown et al. 1987) to 40 years (Bornkamm 1981). The rate of these events depends on factors such as soil (Dzwonko and Loster 1997; Fanelli and Lucchese 1998), climate (Calvo et al. 2005), weed seed bank (Bekker et al. 2000), and the initial density of perennial weed species (Turner et al. 1998). The establishment of juvenile plants, bush, and weed under the tree shadow idiomatically is called ‘understory’ (Leopold and Solozar 2008) that have interference with trees. The interactions between weed growth and tree behaviour have been addressed by diferent studies (Cantarelli et al. 2006; Rondon 2006; Bonari et al. 2017). For example, Larpkern et al. (2010) have identifed specifc species of weeds under the trees after tillage. It is preferable that such weeds be controlled at the early stage of growth, or the use of repair trends become difcult. Increased frequency of species is largely controlled by seed production, species growth rate (Chapin et al. 1997), and competitiveness (Tilman 1988). The chemicals characteristics of soil such as nutrients, salts, and organic matter may cause the appearance of specifc weed species (Garnier et al. 2004; Salama et al. 2017). Some research work has shown a correlation between variation of soil nutrients and plant composition (Shaltout et al. 2014; Angiolini et al. 2017). For example, when soil nitrogen and organic matter reduces, bushes are replaced with grasses (Reynolds et al. 1999; Suding et al. 2008).

Biological control of weeds, based on applications of ecological, evolutionary and experimental science, is a highly successful discipline with a rich history, going back over 115 years. It is a global practice: the development of every weed biological control organism, and its subsequent release in the country of introduction, requires collaborative research on at least two continents and typically includes the involvement of several countries. Weed biocontrol practitioners, comprising researchers, land managers and policy makers, constitute a community with a shared goal, namely the suppression of invasive alien plants in agriculture and in conservation areas, through the deployment of suitably-tested and environmentally safe (i.e. sufficiently host-specific), plant-feeding insects, mites and pathogens. A complete record of every deliberate instance of weed biocontrol, worldwide, up to December 2012 (see Table 1 in Winston et al. 2014; and updated at http://www.ibiocontrol.org/catalog/) has been compiled in the expansive 5th edition of ‘Biological control of weeds—A world catalogue of agents and their target weeds’. This compilation records successes and failures, with accounts of the circumstances in each case, and a summary of the information by Schwarzla¨nder et al. (2018) is the subject of the opening paper in this Special Issue of BioControl.

1.1. Background and motivation

Weeds are one of the big challenges in agriculture because they appear everywhere randomly, and compete with the plant for resources. As a result of this competition for resources, crop yields suffer. Yield losses depend on factors such as weed species, population density, and relative time of emergence and distribution as well as on the soil type, soil moisture levels, pH and fertility (Papamichail et al., 2002). Numerous researchers have identified a strong link between weed competition and crop yield loss, with a wide range of crop varieties. For example, according to the study by Stall (2009), an annual loss of 146 million pounds of fresh market sweet corn and 18.5 million pounds of sweet corn for processing occurred in the United States from 1975 to 1979 due to weed competition, which corresponds to revenue losses of $13,165,000 and $9,155,000 respectively. Besides, the dry and head weight of crop yield are measured to evaluate losses. Based on a study carried out in 1996/1997 and repeated in 1997/1998 in central Jordan (Qasem, 2009), it was found that the average reduction in shoot dry weight and head yield were 81% and 89% respectively. An effective and efficient weed management system is necessary to minimise yield losses in valuable crops. The critical period for weed control must be taken into account to enhance weed management strategies (Swanton and Weise, 1991), as the duration of co-existence of weed and crop is an important indicator of yield losses due to weed competition (Kropff et al., 1992). Zimdahl (1988, 1993) defined the critical period of weed control (CPWC) as ‘‘a span of time between that period after seeding or emergence when weed competition does not reduce crop yield and the time after which weed competition will no longer reduce crop yield”. A more quantitative definition is as the number of weeks after crop emergence during which a crop must be weedfree in order to prevent yield losses greater than 5% (Hall et al., 1992; Van Acker et al., 1993; Knezevic et al., 1994).

The increasing interest in organic and low-input farming systems has renewed attention toward alternative methods of weed management, such as the development of innovative mechanical solutions (Avola et al., 2008; Pannacci and Tei, 2014; Melander et al., 2015). Organic and low-input farming systems mainly relied for its crop nutrients on legume crops (De Ponti et al., 2012). In general, increasing legume cultivation could bring benefits for the environment and resource use at a range of scales, from the field to the global; their precrop effect, nitrogen provision, and potential to improve nutrient conservation and soil structure add to the sustainability of farm productivity while saving resources and reducing emissions (Covarelli et al., 2010; Reckling et al., 2014). Among the grain legume crops, soya bean and faba bean are considered very important, although due to different reasons. In fact, soybean (Glycine max (L.) Merr.) is one of the most important grain legume and oilseed crops in the world, accounting for more than 50% of the global oilseed production (Datta et al., 2017). Faba bean (Vicia faba L.) is grown world-wide as a protein source for food and feed, offering ecosystem services such as renewable inputs of nitrogen (N) into crops and soil via biological N2 fixation, and a diversification of cropping systems (Jensen et al., 2010). It is well known that prolonged weed interference not only causes heavy crops yield losses, but increases production costs and reduces the quality of produce, thus requiring early-season weed management to achieve economically acceptable yields (Knezevic et al., 2003; Sardana et al., 2017). In particular, the presence of weeds up to beginning of seed stage of soya bean (R5) may cause 8–55% reduction in yield (Van Acker et al., 1993). Weeds are managed in soya bean primarily by herbicides (Niekamp and Johnson, 2001; Datta et al., 2017), although mechanical and cultural weed control methods showed to be effective (Chauhan and Opeña, 2013; Pannacci and Tei, 2014). Faba bean is known to compete weakly against weeds in the early growth phase (Lee and Lopez-Ridaura, 2002); so the pre-emergence herbicides are commonly used in order to control weeds until the crop is big enough to suppress any additional emerging weeds (Köpke and Nemecek, 2010). However, over the last twenty years, environmental and human health impact of herbicides use, increasing of herbicide resistance, the scarce availability of herbicides for minor crops and the increased of organic farming were the main factors that stimulated the interest to develop alternative methods to chemical weed control, such as mechanical weed control (Melander et al., 2005; Pannacci et al., 2017).

Reduction in economic losses in agricultural production due to abiotic and biotic factors is of utmost importance in modern day inputintensive agricultural systems. Sustaining the production levels demands devising newer strategies for mitigating the ill-effects of these adverse factors. As with abiotic causes, especially the lack or excess of moisture in the growth season, extreme temperatures, high or low irradiance and nutrient supply, biotic stresses have the potential to reduce yields substantially (Oerke, 2006). Among the major biotic constraints, weeds are considered as the most harmful to agricultural production besides affecting agrobiodiversity and natural water bodies. They also affect the crop production indirectly, by competing with the crop for resources, sheltering crop pests, interfering with water management, reducing the yield and quality, and subsequently increasing the cost of processing (Zimdahl, 2013). Therefore, weed management is the major and important part of crop production. In India, reduction in crop yield was estimated as 31.5% (22.7% in winter and 36.5% in summer and rainy seasons) by weeds (Bhan et al., 1999). Whereas, the economic losses due to weeds in India was estimated as INR 20 to 28 billion about two decades ago (Sahoo and Saraswat, 1988; Sachan, 1989). In another study, it was reported that loss in agricultural production due to weeds amounts to INR 1050 billion per annum (NRCWS, 2007; Varshney and PrasadBabu, 2008). In general, the yield loss due to weeds is almost always caused by a group of different weed species, and these weeds may have substantively different competitive ability (Weaver and Ivany, 1998; Milberg and Hallgren, 2004). Practically, it is very difficult to estimate the yield loss due to single weed species and therefore, it is estimated as the collective efforts by all the weeds. Overall, weeds produced the highest potential loss (34%), with animal pests and pathogens being less important (losses of 18 and 16%) worldwide (Oerke, 2006). As far as studies on yield loss at global level is concerned, Milberg and Hallgren (2004) explored the large-scale patterns in yield loss in cereals due to weeds in Sweden and mentioned that weed biomass explained 31% of the variation in yield loss due to weeds. Whereas, O’Donovan et al. (2005) developed various regression equations in western Canada to estimate the effects of weeds on yield loss of field crops. Oliveira et al. (2014) also presented that insect, pests cause an average annual production loss of 7.7% in Brazil, which is a reduction of approximately 25 million tonnes of food, fibre and biofuels.

مقاله سال 2016

زیرگونه‌های خربزه‌های کوچک وحشی اگرستیس، یک نوع گیاه مهاجم در بسیاری از نواحی آسیا و شمال آمریکا هستند. تولیدمثل این‌ گونه‌ها از طریق دانه انجام می‌شود. بنابراین ، آزمایشات آزمایشگاهی به منظور تعیین دمای کاردینال و تأثیر نوسانات دما، گرما ، استرس غوطه‌وری در آب، PH، طول عمر دانه، و عمق کاشت دانه خربزه برای جوانه‌زنی و پیدایش جوانه انجام شدند. از بین سه مدل نمونه آزمایش شده، مدل خطوط تقاطعی بهترین برآورد را در مورد دمای کاردینال داشت. دمای پایه ، بهینه و ماکسیمم برای جوانه زدن دانه خربزه به ترتیب 20 ، 35، و 45 درجه سانتی‌گراد تخمین زده شد. بالاترین میزان جوانه‌زنی خربزه وحشی در °C 20 /30 و °C 35 /25 (روز / شب) مشاهده شد. فقط قرارگیری طولانی‌مدت آن‌ها ( تا 10 روز) در دمای °C 90 و یا بیش از 5 دقیقه در °C 120 در کاهش جوانه‌زنی دانه خربزه وحشی اثرگذار بود. غوطه‌وری در آب تا زمانی که 3 ماه از انجام آن گذشته باشد، تأثیر ناچیزی در کاهش جوانه‌زنی دانه خربزه دارد. دانه‌های این علف هرز در طیف گسترده‌ای از مقادیر PH جوانه‌زده ، اما میزان جوانه‌زنی تحت شرایط اسیدی (PH 5) بیشتر از شرایط پایه (PH 8 , 9) بود. جوانه‌زنی دانه‌های خربزه وحشی با گذشت 23 ماه از کاشتن آن‌ها در خاک در عمق 15 سانتی‌متری تا 50% کاهش پیدا کرد. پیدایش جوانه‌های خربزه وحشی در عمق‌های کمتر بیشتر از عمق‌های بیشتر بود. این نتایج نشان می‌دهند که گسترش موفق خربزه وحشی در منطقه تا حدودی می‌تواند با تحمل آن در برابر شرایط محیطی توضیح داده شود. ترکیبی از طول عمر دانه ، عدم رکود دانه و جوانه‌زنی سریع دانه تحت شرایط نامطلوب آب و هوایی ممکن است توضیحی برای رشد سریع دانه‌های هرز در محصولات تابستانی باشد. در بین استراتژی‌های مدیریت که می‌توانند برای محدود کردن هجوم خربزه‌های وحشی در زمین‌ها بکار برده شوند، به نظر می‌رسد که کاشت عمیق دانه در طی آماده‌سازی خاک ، امیدوارکننده‌تر باشد.

1. مقدمه
خربزه‌های کوچک وحشی و خوش بوی اگرستیس ، مختص منطقه اوراسیا می‌باشند و از گونه‌های مهاجم در بسیاری از قسمت‌های جهان هستند. آن به‌عنوان یکی از دانه‌های هرز مهم خانواده کدو محسوب می‌شود و محصولاتی مانند کتان ، ( پروستکو و چاندلر ،1998، تینگل و همکاران ،2003)، بادام زمینی ( گریچار ، 20007a) و دانه سویا ( پریچار، 2007b، سهرابی و همکاران ،2013) را موردحمله قرار می‌دهد. این خربزه‌های وحشی ، تاک‌های بالارونده‌ای هستند که دارای گل‌های نر و ماده در یک گیاه می‌باشند و از طریق دانه تولیدمثل می‌کنند. ویژگی‌های اصلی که این گونه‌های خودرو را از خربزه‌های کاشته شده متمایز می‌کند، اندازه گیاه و میوه آن است. گیاهان و میوه‌های گونه‌های کاشته شده آن، بزرگ‌تر از گونه‌های خودرو هستند. میوه‌های این گیاهان خودرو به شکل بیضوی و کروی هستند و دارای قطر 1.9 تا 2.5 سانتی‌متر و طول 2 تا 4.5 سانتی‌متر می‌باشند که هر یک تقریباً حاوی 180 دانه است( کونون و همکاران، 2009؛ سهرابی و همکاران ،2014).