Potential uses of small unmanned aircraft systems (UAS) in weed research

Small unmanned aerial systems (UAS) with cameras have not been adopted in weed research, but offer low‐cost sensing with high flexibility in terms of spatial resolution. A small rotary‐wing UAS was tested as part of a search for an inexpensive, user‐friendly and reliable aircraft for practical applications in UAS imagery weed research. In two experiments with post‐emergence weed harrowing in barley, the crop resistance parameter, which reflects the crop response to harrowing, was unaffected by image capture altitude in the range from 1 to 50 m. This corresponded to image spatial resolution in the range from 0.3 to 17.1 mm per pixel. This finding is important because spatial resolution is inversely related to sensing capacity. We captured 20 plots comprising a total of about 0.2 ha in one image at 50 m altitude without losing information about the cultivation impacts on vegetation compared with ground truth data. UAS imagery also gave excellent results in logarithmic sprayer experiments in oilseed rape, where we captured 37 m long plots in each image from an altitude of 35 m. Furthermore, perennial weeds could be mapped from UAS images. These first experiences with a small rotary‐wing UAS show that it is relatively easy to integrate as a tool in weed research and offers great potential for site‐specific weed management.     

Use of mesotrione and tembotrione herbicides for post-emergence weed control in alkaloid poppy (Papaver somniferum)

Two field experiments were carried out a year apart on the alkaloid poppy (Papaver somniferum) in 2012 and 2013 in north-west Hungary, to assess the efficacy of mesotrione and tembotrione herbicides for post-emergence weed control. Our experiments tested (1) a single application of mesotrione at 144 g active ingredient (a.i.) ha^–1, (2) two separate applications of mesotrione at 144 g a.i. ha^–1, (3) a single application of tembotrione at 88 g a.i. ha^–1, (4) two separate applications of mesotrione at 88 g a.i. ha^–1, and (5) the combination of a single application of mesotrione at 144 g a.i. ha^–1 followed by a single application of tembotrione at 88 g a.i. ha^–1. Both non-treated and hand-weeded plots were used as controls. Among the most important weeds, Chenopodium album was most successfully controlled in the majority of the test treatments, but Fallopia convolvulus and Polygonum aviculare tolerated each herbicide application in 2012, likely due to the dry weather conditions. Because of the botanical similarity to the crop, none of the treatments proved to be significant against Papaver rhoeas. One dosage of tembotrione alone never reduced the dry weights of the target weed species or weed numbers significantly. The cuticular wax layer of the opium poppy can provide a natural defence against these herbicides, but some temporary phytotoxic yellowish discoloration occurred after tembotrione treatments. Our results show that mesotrione in combination with tembotrione is the most effective treatment and should be employed in poppy cultivation.     

Alligator weed (Alternanthera philoxeroides) in New South Wales,Australia: A status report

Alligator weed, Alternanthera philoxeroides (Martius) Grisebach, of the family Amaranthaceae, has become a weed in many countries outside of its natural range in South America. In Australia, it is classified as a weed of national significance because of its potential to devastate agricultural and natural ecosystems. In New South Wales, the weed management officers of local government areas are charged with its control. In 2007, we surveyed this group to determine the status of alligator weed in each jurisdiction and to determine the methods and resources used in its control. Half of the local government area officers who responded reported its presence. The age, number, and size of the infestations indicated that the weed continues to spread into new areas, and is well established in others, at least within local government areas. The resources provided for the weed's management across the local government areas was less than had been expended annually on its removal from a single swamp. The respondents acknowledged that the current approach was inadequate and the need for research into its management was identified. We conclude that, with current management, the weed will continue to spread and recommend that the community should be mobilized to identify new areas of infestation and appropriately train people (e.g. bush restoration consultants, Landcare groups) to remove the weed.     

Characterization and pathogenicity of Fusarium solani causing foot rot on hemp (Cannabis sativa L.) in Southern Italy

Journal of Plant Diseases and Protection - Symptoms of foot rot were observed on hemp (Cannabis sativa) plants in Campania region (Southern Italy) in 2018. The symptoms consisted of brownish areas...     

Biology,ecology and management of the invasive parthenium weed (Parthenium hysterophorus L.)

Parthenium weed (Parthenium hysterophorus L.) is one of the most aggressive invasive weeds, threatening natural ecosystems and agroecosystems in over 30 countries worldwide. Parthenium weed causes losses of crops and pastures, degrading the biodiversity of natural plant communities, causing human and animal health hazards and resulting in serious economic losses to people and their interests in many countries around the globe. Several of its biological and ecological attributes contribute towards its invasiveness. Various management approaches (namely cultural, mechanical, chemical and biological control) have been used to minimise losses caused by this weed, but most of these approaches are ineffective and uneconomical and/or have limitations. Although chemical control using herbicides and biological control utilising exotic insects and pathogens have been found to contribute to the management of the weed, the weed nevertheless remains a significant problem. An integrated management approach is proposed here for the effective management of parthenium weed on a sustainable basis. © 2014 Society of Chemical Industry     

我国农田杂草治理技术的发展

我国稻、麦、玉米、大豆及棉花等主要农作物农田杂草有580种,属于危害重而又难于防除的有17种,受杂草危害较重的农田有3 580万hm²,年平均受草害减产12.3％～16.5％(加权平均)。自1980年以来,全国化学除草面积以年增200万hm²的速度扩大,农田化学除草面积从20世纪70年代早期不到100万hm²扩大到近年来6 000万hm²。本文概述了我国农田主要作物杂草的发生危害、化学除草剂应用现状及其综合防治进展,并提出今后杂草防除的设想与建议。     

Reviewing research priorities in weed ecology,evolution and management: a horizon scan

Weedy plants pose a major threat to food security, biodiversity, ecosystem services and consequently to human health and wellbeing. However, many currently used weed management approaches are increasingly unsustainable. To address this knowledge and practice gap, in June 2014, 35 weed and invasion ecologists, weed scientists, evolutionary biologists and social scientists convened a workshop to explore current and future perspectives and approaches in weed ecology and management. A horizon scanning exercise ranked a list of 124 pre‐submitted questions to identify a priority list of 30 questions. These questions are discussed under seven themed headings that represent areas for renewed and emerging focus for the disciplines of weed research and practice. The themed areas considered the need for transdisciplinarity, increased adoption of integrated weed management and agroecological approaches, better understanding of weed evolution, climate change, weed invasiveness and finally, disciplinary challenges for weed science. Almost all the challenges identified rested on the need for continued efforts to diversify and integrate agroecological, socio‐economic and technological approaches in weed management. These challenges are not newly conceived, though their continued prominence as research priorities highlights an ongoing intransigence that must be addressed through a more system‐oriented and transdisciplinary research agenda that seeks an embedded integration of public and private research approaches. This horizon scanning exercise thus set out the building blocks needed for future weed management research and practice; however, the challenge ahead is to identify effective ways in which sufficient research and implementation efforts can be directed towards these needs.     

Evaluation of the allelopathic potential of Kava (Piper methysticum L.) for weed control in rice

Kava is a perennial pepper plant from the Oceanic region, which is commonly used as a drink by natives and for pharmacological purposes. Results of this study concluded that Kava has allelopathic potential and suppressed germination and growth of lettuce ( Lactuca sativa L), barnyardgrass ( E. crus-galli Beauv var. formosensis Ohwi.), and duck-tongue weed ( M. vaginalis Presl var. plantaginea Solms-Laub.) Moreover, Kava inhibited emergence of weeds in paddy soils. The inhibition of Kava became stronger as the applied concentration increased. In a greenhouse experiment, Kava had the greatest inhibition on emergence and weed growth in paddy soils when a dose of 1 ton ha⁻¹ of Kava was divided and applied at 3, 16, and 23 days after watering. Inhibition by Kava varied among weed species. Results from this study suggest that Kava might be useful for weed control in rice or reduce dependence on herbicide.     

Cover crops and mulches influence weed management and weed flora composition in strip‐tilled tomato (Solanum lycopersicum)

This study was conducted in the Mediterranean environment of Central Italy from 2011 to 2013 with the aim of evaluating the effects of winter cover crops and their residues on weed composition in a cover crop‐tomato sequence. Treatments consisted of five soil managements (three cover crop species ‐ hairy vetch, phacelia, white mustard, winter fallow mulched with barley straw before tomato transplanting and conventionally tilled soil), two nitrogen fertilisation levels (0 and 100 kg N ha^?1) and two weed management levels (weed free and weedy) on tomato. Cover crop residues were arranged in strips on the soil surface and then used as beds for transplanting the tomato seedlings in paired rows. Rotary hoeing was performed in the bare strips between paired tomato rows. At tomato harvesting, the weed aboveground biomass and density was higher in nitrogen‐fertilised tomato than unfertilised tomato, except in hairy vetch and barley straw that showed similar values. Hairy vetch used as a cover crop and dead mulch was the most suppressive species with the highest production of residues, while phacelia and mustard were not suitable for controlling weeds. The tomato yield was high in nitrogen fertilised and weed‐free treatments, except in barley straw mulch, which showed similar values among the weed management treatments. The mulch strips caused variations in weed species composition that was mainly composed of perennial ruderal weeds, while in tilled soil, the weed flora was dominated by annual photoblastic weeds.     

Comparison of crop and weed height,for potential differentiation of weed patches at harvest

Weeds and weed control are major production costs in global agriculture, with increasing challenges associated with herbicide‐based management because of concerns with chemical residue and herbicide resistance. Non‐chemical weed management may address these challenges but requires the ability to differentiate weeds from crops. Harvest is an ideal opportunity for the differentiation of weeds that grow taller than the crop, however, the ability to differentiate late‐season weeds from the crop is unknown. Weed mapping enables farmers to locate weed patches, evaluate the success of previous weed management strategies, and assist with planning for future herbicide applications. The aim of this study was to determine whether weed patches could be differentiated from the crop plants, based on height differences. Field surveys were carried out before crop harvest in 2018 and 2019, where a total of 86 and 105 weedy patches were manually assessed respectively. The results of this study demonstrated that across the 191 assessed weedy patches, in 97% of patches with Avena fatua (wild oat) plants, 86% with Raphanus raphanistrum (wild radish) plants and 92% with Sonchus oleraceus L. (sow thistles) plants it was possible to distinguish the weeds taller than the 95% of the crop plants. Future work should be dedicated to the assessment of the ability of remote sensing methods such as Light Detection and Ranging to detect and map late‐season weed species based on the results from this study on crop and weed height differences.     

A weed suppressive index for spring barley (Hordeum vulgare) varieties

A screening programme for crop variety competitiveness would ideally be based on only a few, non-destructive measurements of key growth traits. In this study we measured the weed suppressive ability of 79 varieties of spring barley in two ways: (i) directly, by weed coverage assessments under weedy conditions at three Danish locations in 2002–2004 and (ii) indirectly, by non-destructive measurements of varietal growth traits under weed-free conditions in 17 other experiments in Denmark in 2001–2003. Based on just four varietal growth traits (reflectance, leaf area index, leaf angle and culm length), we successfully developed a method for indexing the weed suppressive ability of spring barley varieties. The suppressive index ranged from 12% in Lux and 55% in Modena in proportion to the 90% quantile coverage of all varieties. The index was validated against independent data from two locations in 2005 with 14 and 24 varieties and was found valuable for future use in regular screening programmes.     

Weed flora and weed management in established olive groves in Albania

Weed flora were surveyed during 2000 and 2001 in 10 established olive groves that were located in the area of Vlora, in south‐western Albania. The effectiveness of six weed management treatments (soil tillage, straw mulch, cover cropping [a mixture of rye with peas], and grazing, as well as glyphosate and diuron application) on the weed flora, olive yield, and fruit quality also were investigated in two locations during 2000, 2001, and 2002. More than 80 weed species were recorded, representing a total of 14 families, in which the families Poaceae, Fabaceae, Asteraceae, Ranunculaceae, and Rosaceae predominated. The glyphosate application provided the highest and most consistent level of weed control, whereas diuron achieved sufficient weed control. The straw mulch provided acceptable weed control but the cover crop and the grazing did not sufficiently control the weeds. The highest fruit and oil yields were produced by the trees treated with the straw mulch as a result of the highest mean fruit weight in each year, followed by the soil tillage treatment. However, the olive trees in the plots treated with glyphosate or grazing provided lower or equal, respectively, fruit and oil yields than did those in the untreated plots (control). The results indicated that certain non‐chemical weed control methods, such as straw mulch, can be implemented successfully in established olive groves, providing satisfactory control of weeds and promoting the highest fruit and oil yields.     

Arbuscular-mycorrhizal fungi: potential roles in weed management

The importance of interactions between arbuscular-mycorrhizal fungi (AMF) and weeds of agro-ecosystems is reviewed. Considerable evidence suggests that AMF can affect the nature of weed communities in agro-ecosystems in a variety of ways, including changing the relative abundance of mycotrophic weed species (hosts of AMF), and non-mycotrophic species (non-hosts). These effects may merely change the composition of weed communities without affecting the damage that these communities cause. However, it is quite plausible that interactions with AMF can increase the beneficial effects of weeds on the functioning of agro-ecosystems. Through a variety of mechanisms, weed:AMF interactions may reduce crop yield losses to weeds, limit weed species shifts, and increase positive effects of weeds on soil quality and beneficial organisms. If beneficial effects of AMF on the composition and functioning of weed communities can be confirmed by more direct evidence, then AMF could provide a new means of ecologically-based weed management. Intentional management will be required to increase diversity and abundance of AMF in many cropping systems, but these actions (e.g. conservation tillage and use of cover and green-manure crops) typically will confer a range of agronomic benefits in addition to potential improvements in weed management.     

Weed infestation and tea growth under various weed management methods in a young tea (Camellia sinensis[L.] Kuntze) plantation

A field experiment was conducted in the low country of Sri Lanka, during the period 1994–1995 to investigate the severity of weed infestation and tea growth in relation to weed management methods in newly established tea ( Camellia sinensis [L.] Kuntze). Manual weeding (hand and slash weeding) at various intervals was compared with various herbicides, with or without mulching. Weed control with herbicides was superior to that of hand weeding at 6-week intervals or more. Weed control with oxyfluorfen at 0.29 kg ai ha⁻¹ + paraquat at 0.17 kg ai ha⁻¹ or glyphosate at 0.99 kg ai ha⁻¹ + kaolin at 3.42 kg ha⁻¹ were superior. Plots unweeded for 12 weeks or more produced significantly greater ( P  < 0.05) weed biomass than plots unweeded for 6 weeks. Although the least weed dry weight ( P  < 0.05) and the greatest number of weed species were recorded with hand weeding at 2 week intervals, there was no particular benefit on tea growth when compared with hand weeding at 6 and 12 week intervals. Inter row mulching in chemically treated plots was more favorable for tea growth than no mulching, while living weed cover in unmulched slash weeded plots suppressed tea growth. A combination of mulching and herbicides, particularly oxyfluorfen and paraquat, followed by hand weeding at least every 6–8 weeks was considered the most appropriate weed management system for young tea.     

Weeds and weed management in rice production in Japan

The area of paddy rice fields in Japan was 1.79 million ha in 1998 almost all of which was planted with young seedlings from nursery boxes by a mechanical rice transplanter. Japanese farmers controlled paddy weeds mainly by chemical herbicides, which were applied around 1.8 times in one growing season of rice by sequential treatment. The cost of herbicides was 35 320 ¥/ha on average, the main of which was ‘one‐shot’ herbicides, while weeding labor for the paddy field, including herbicide application, was 19.0 h/ha, or 29 976 ¥/ha in labor cost, in 1998. Under the Integrated Weed Management (IWM) for sustainable paddy rice production, other technologies for weed management are also recommended to paddy farmers, such as ecological or cultural, mechanical, biological methods and so on.     

Development of chemical weed control and integrated weed management in China

More than 200 species of weeds are infesting main crop fields in China, among which approximately 30 species are major weeds causing great crop yield losses. About 35.8 million hectares of crop fields are heavily infested by weeds and the annual reduction of crop yields is 12.3–16.5% (weighted average). Along with rural economic development, approximately 50% of the main crop fields undergo herbicide application. Chemical weed control has changed cultural practices to save weeding labor in rice, wheat, maize, soybeans and cotton. At the same time, continuous use of the same herbicides has caused weed shift problems and weed resistance to herbicides. Consequently, integrated weed management in main crops is being developed.     

Agronomic practises for weed control in turmeric (Curcuma longa L.)

Weeds are the main problem with turmeric (Curcuma longa L.) cultivation where herbicides are not allowed. This is because herbicides cause water contamination, air pollution, soil microorganism hazards, health hazards, and food risks. Considering turmeric's medicinal value and the environmental problems caused by herbicides, various agronomic practises have been evaluated for non‐chemical weed control in turmeric. One additional weeding is required before turmeric emergence and weed infestation is much higher when turmeric is planted in February and March, as compared to April, May or June planting. A similarly higher yield of turmeric is achieved when it is planted in February, March, and April, compared to late plantings. Weed emergence and interference are not affected by planting depth, seed size, planting pattern, planting space, ridge spacing, and the row number of turmeric until 60 days after planting. This is because turmeric cannot develop a canopy structure until then. Thereafter, weed infestation reduces similarly and significantly when turmeric is planted at depths of 8, 12, and 16 cm, compared to shallower depths. The yield of turmeric at these depths is statistically the same, but the yield for the 16 cm depth is difficult to harvest and it tends to decrease. Turmeric grown from seed rhizomes (daughter rhizomes) weighing 30–40 g reduces weed infestation significantly and obtains a significantly higher yield compared to smaller seeds. The mother rhizome also can suppress weed infestation and increase the yield markedly. Around 9% weed control and 11% higher yield are achieved by planting turmeric in a triangular pattern compared to a quadrate pattern. The lowest weed infestation is found in turmeric grown in a 20 or 30 cm triangular pattern and the highest yield is obtained with the 30 cm triangular pattern. Turmeric gown on two‐row ridges spaced 75 cm apart shows excellent weed control efficiency and obtains the highest yield. This review concludes that turmeric seed rhizomes of 30–40 g and/or the mother rhizome could be planted in a 30 cm triangular pattern at the depth of 8–12 cm on two‐row ridges spaced 75–100 cm apart during March to April in order to reduce weed interference and obtain a higher yield. Mulching also suppresses weed growth and improves the yield. The above agronomic practises could not control weeds completely; biological weed management practises could be integrated in turmeric fields using rabbits, goats, sheep, ducks, cover crops or intercrops.     

Potential allelopathic rice lines for weed management in Cambodian rice production

In Cambodia, the planting of rice lines with a competitive and/or allelopathic ability would be a very useful way to supplement weed management in the rain‐fed, low‐input production systems. The present study examines a wide range of rice germplasm, mainly from Cambodia, and uses a series of bioassay techniques to identify those that might have a weed growth‐suppressing, allelopathic trait. A laboratory bioassay study that involved 359 rice lines showed that there were 15 that could significantly reduce the growth of awnless barnyard grass seedlings. In a second laboratory bioassay, involving the best 96 rice lines that were identified in the first study, 14 were shown to suppress the shoot growth of awnless barnyard grass, 11 could suppress the shoot growth of barnyard grass, six could suppress the shoot growth of small umbrella sedge, four could suppress the shoot growth of two‐leaf fimbristylis, four could suppress the shoot growth of water primrose, and three could suppress the shoot growth of gooseweed. Of the 13 rice lines that were able to suppress the growth of at least two weed species, there were three lines that could suppress the growth of three weed species, one line that could suppress the growth of four weed species, and one line that could suppress the growth of five weed species. In a third soil‐based, pot bioassay that studied the 18 best lines coming from the second laboratory bioassay, all showed a significant weed growth‐suppressive ability. A linear regression analysis showed that there was no correlation between their weed growth‐suppressive ability and their physical seedling size, supporting the idea that the growth suppression was allelopathic in nature and not a physical competition effect. In summary, the results indicate that an allelopathic trait does exist in some Cambodian rice lines and that this trait is effective in the growth suppression of a number of major rice weeds.     

Weed seed germination and the light environment: Implications for weed management

Light regulates dormancy termination and the subsequent germination in many weed species. Under field conditions, the light environment of the seeds, which is perceived mainly by photoreceptors of the phytochrome family, provides essential information for cueing germination in the proper environmental situation. The light environment's spectral composition and irradiance allow weed seeds to sense their position in the soil profile, the presence of a leaf canopy capturing light and other resources and the occurrence of soil cultivation. From an agronomical point of view, the control of germination by light represents a potentially useful step in the life cycle of weeds for developing effective control practices. The goal of this article is to place current knowledge regarding photoreceptors, physiological and molecular bases of seed responses to light and their ecological implications within the context of weed management in agricultural systems. With that final objective, the authors intend to show how a better understanding of the way in which the light environment regulates dormancy termination and the subsequent germination of weed seeds could be used to develop more accurate control practices and to improve weed management strategies.