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A laboratory bioassay was conducted to determine the allelopathic potentials of aqueous extracts from either roots or leaves of seventeen sweet potato [Ipomoea batatas L. (Lam)] cultivars (SP0, SP1, SP2, SP3, SP4, SP5, SP6, SP7, SP9, SP10, SP11, SP13, SP14, SP15, SP16, SP18, and SP19). Most inhibitory rates on Lactuca sativa calculated for leaf or root extracts from the seventeen sweet potato cultivars exhibited positive values and significantly increased with increasing concentration. Germination was totally inhibited at a concentration of 0.05 g·mL−1 for leaf water extracts of SP13, SP15, SP18 and at a concentration of 0.05 g·mL−1 for both leaf and root water extracts of SP19. Inhibition of root length was clearly greater than inhibition of shoot length for both leaf and root water extracts. Biomass inhibition increased with increasing concentration, but some cultivars showed stimulatory effects at low concentrations, and inhibition was generally more pronounced for root water extracts than for leaf water extracts. Moreover, most synthetical inhibitory rates for both leaf and root water extracts from the seventeen cultivars exhibited positive values and significantly increased with increasing concentration. Comparing the synthetical inhibitory rates for both leaf and root water extracts among the seventeen cultivars, SP19, SP6, SP11, and SP7 had the highest allelopathic inhibition. The inhibitory activity on germination index was the greatest, followed by germination rate, root length, biomass, and shoot length in all bioassays. Inhibition by leaf water extracts was generally greater than inhibition by root water extracts, except in the case of shoot length or biomass. Overall, we conclude that all seventeen sweet potato cultivars have strong inhibitory effects on L. sativa, but that these effects vary with cultivar and plant part, with SP19, SP6, SP11, and SP7 exhibiting the highest rates of allelopathic inhibition.

China has become one of the countries most seriously affected by invasive alien weeds in the world. Weeds impact agriculture, the environment and human health, and conventional control methods such as herbicides are expensive, damaging to human health and unsustainable. As the impacts and costs of weed control in China increase, there is an urgent need to manage some of the more important weeds through more sustainable methods. Classical biological control of invasive alien weeds is environmentally-friendly and sustainable. Biological control in China began in the 1930s with the introduction of two agents into Hong Kong for the control of Lantana camara. Since then, a further seven biological control agents have been introduced into China to control four weed species. In addition, 11 biological control agents targeting seven weed species have naturally spread into China. Together, these biological control agents are helping to control some of China's worst weeds. However, these efforts are only a small portion of the weeds that could be targeted for weed biological control. This paper reviews the current status of weed biological control efforts against introduced weeds in ten provinces and regions in southern China and provides a platform to identify the most effective and appropriate weed biological control opportunities and programmes to pursue in the future. Introducing additional safe and effective biological control agents into China to help manage some of the worst weeds in the region should reduce the use of herbicides and impacts on human health and the environment, while increasing productivity and food security.

The status of weed biological control in the six Greater Mekong Subregion (GMS) countries was assessed, and opportunities to develop biological control in the region are proposed. Twenty biological control agents targeting nine weed species have been introduced into GMS countries, with 13 agents establishing on seven weed species. Another nine biological control agents have spread unintentionally into the region. These agents are having a slight to high impact on their target weeds. However, the number of weeds in the region that have been targeted for biological control is only a fraction of the number of weeds (45) in the region that have been targeted for biological control elsewhere. This presents a tremendous opportunity to expand weed biological control in the region and reduce the dependency on herbicides while increasing productivity. There are numerous highly effective biological control agents present elsewhere that could be introduced to assist with the management of the region's most important weeds, such as Pistia stratiotes , Salvinia molesta , Chromolaena odorata and Mikania micrantha . Along with the introduction of biological control agents, there is also a scope to increase the capacity and training in biological control within GMS countries to develop effective weed control and management.

The white-backed planthopper (WBPH), Sogatella furcifera (Horváth), is a destructive pest of rice in the Greater Mekong Subregion (GMS) countries including Cambodia, Laos, Myanmar, Thailand, Vietnam, and China’s Yunnan Province. Our previous study not only confirmed the immigration sources of the WBPH in China’s Yunnan Province were from Myanmar, Vietnam, and Laos, but also indicated that Cambodia was likely an additional migration source. To further clarify the migration sources and patterns of the WBPH in the GMS, we investigated the genetic structure of 42 WBPH populations using microsatellite loci markers. The analysis of genetic diversity, heterozygosity deficit, and heterozygosity excess based on the nuclear markers suggest that there is extensive gene flow between the 42 sampled populations from the GMS. The genetic structure confirmed the immigration sources of WBPH as revealed by mitochondrial markers and trajectory analyses methods in previous studies. These findings will aid in the sustainable regional management of this insect pest in the GMS.

Alien invasive plants are a serious threat to natural and agricultural systems, especially in areas with sensitive habitats and high value crops. Dehong Prefecture, western Yunnan Province, China is vulnerable to invasive plants and its current status of invasive alien plants is assessed in this article. We compiled a comprehensive list of invasive alien plants with background information from 2013 to 2015, including origin, life form, habit, distribution, affected crop, and damage. The 90 invasive alien plant species in Dehong Prefecture are represented by 28 families and 66 genera, with the three largest families, Asteraceae, Poaceae and Fabaceae, accounting for 48.9% of all species. The proportion of invasive alien plants originating from the Americas, Europe, Asia, and Africa were 68%, 11%, 10%, and 9%, respectively. Almost all invasive alien plants were found in five cities or counties in Dehong Prefecture, and there were more invasive plant species in Ruili City, Luxi City, Yijiang County, and Longchuan County than Lianghe County. Most invasive alien plants were herbs (84.4%), with annual and perennial plants forming equal proportions (both comprised 43.3%). There were 44 invasive plant species rated as causing minor damage, destructive I grade (49% of all species), followed by 27 species rated at intermediate II grade (30%) and 19 species at heavy damage III grade (21%). Most invasive alien plants were both agricultural and environmental species thus negatively impacting both crop production and ecosystems, often significantly. The major infested crops were vegetables, sugarcane, maize, and orchard crops. Given the large number of alien plant invaders, it was concluded that Dehong Prefecture has become a major “window” for foreign alien plants entering in Yunnan Province and even for China as a whole. More attention should be paid to this issue, and effective measures should be developed to manage the expansion and damage caused by invasive alien plants.

Mikania micrantha Kunth, commonly known as bitter vine, American rope, or mile-a-minute, is a rapidly growing vine, native to tropical America. Mikania micrantha is present in 20 Pacific island countries and territories, including Australia, the Cook Islands, Fiji, French Polynesia, Micronesia, Papua New Guinea, Samoa, Solomon Islands, and Vanuatu. A CLIMEX model based on native distribution of M. micrantha suggests that most of the islands in the Pacific, southern Asia, and parts of southern and central Africa are climatically suitable for M. micrantha, leaving these areas vulnerable to new or further incursions. Its rapid spread is a threat to both natural and agricultural environments, where it kills or reduces growth of preferred species, severely impacting on biodiversity and production. Large numbers of wind-dispersed seeds and ability to propagate vegetatively from stem fragments facilitate rapid invasion. Management of M. micrantha is difficult. Several postemergence herbicides exhibit s...

Background and objectives Sweet potato [Ipomoea batatas (L.) Lam] is an important locally grown cash crop in China; it was demonstrated to suppress the invasive plant Mikania micrantha (M. micrantha) H.B.K through strong competitiveness, but its allelopathic effects on this weed were unknown. The present study aimed to explore the allelopathic potential of sweet potato on M. micrantha. Materials and methods The allelopathic effects of water extracts and soil incorporation from leaves of three sweet potato cultivars (SP1, SP0 and SP9) on the sprout seedling growth of invasive plant M. micrantha in Yunnan Province, China, were studied under laboratory and greenhouse conditions. Results Stem length, root biomass, aboveground biomass and total biomass of M. micrantha were significantly reduced with increasing concentration in both leaf water extracts and leaf soil incorporation of three sweet potato cultivars. Among these, SP1 had the strongest inhibition and the next highest impact was from SP0 with the lowest effect from SP9. The highest inhibition rates were seen for root biomass, followed by total biomass, whereas the lowest impact was on aboveground biomass. The strong correspondence between results for both leaf water extracts and leaf soil incorporation provided a good demonstration that compounds produced by sweet potato have allelopathic effects on M. micrantha. The general inhibition of M. micrantha by sweet potato followed the order among the three sweet potato cultivars tested as SP1, SP0 and SP9. Moreover, the synthetical allelopathic indices of leaf soil incorporation of three cultivars on M. micrantha were generally higher than these of leaf water extracts. Conclusion Competition and allelopathy have primarily been seen as separate ecological weed management tools, but as these have demonstrated in the case of sweet potato where both mechanisms inhibit weed growth, there is potential for synergism between competition and allelopathy in the reduction of weed infestations.

The competitive and allelopathic effects of wild rice (Oryza longistaminata) accessions on barnyard grass at different growth stages determined by days after sowing (0, 30, 60 and 90 days) were studied in greenhouse pot experiments. Wild rice accession RL159 exhibited the greatest height and tillering. The weed suppression rates of wild rice accessions OL and F1 on barnyard grass were significantly higher than for other rice accessions, with the lowest being O. sativa cultivar RD23. The highest suppression rates of OL and F1 were 80.23 and 73.96% at barnyard grass growth stages of 90 days and 60 days. At a 90 growth stage, wild rice accessions RL159 and RL169 caused 61.33 and 54.51% inhibition in barnyard grass growth, respectively. Under the same conditions, the competitive inhibition rates of OL, F1, RL159, RL169 and RL219 against barnyard grass were markedly lower than their weed suppressive effects, but were relatively similar for RD23. The allelopathic inhibition of OL and F1 on barnyard grass was significantly higher than other rice accessions. The highest allelopathic rates of OL and F1 were 60.61 and 56.87% at the 0 day growth stage. It is concluded that wild rice accessions OL and F1 exhibited the highest allelopathic activity along with moderate competitive ability against barnyard grass; wild rice accession RL159 had the highest competitive ability and moderate allelopathic activity on barnyard grass. Thus, the three wild rice accessions OL, F1 and RL159 could be used as ideal breeding materials for cultivated rice improvement.

Background Xishuangbanna of Yunnan Province, southwest of China belongs to a global biodiversity and cultural hotspot. Agrobiodiversity plays an essential role in local livelihoods and traditional culture in the region. However, preliminary studies suggest that diversity of crop plants and livestock species is declining. We hypothesized that agrobiodiversity and traditional means of preserving agrobiodiversity are threatened because of changes in government policy in favor of commercial plantations, land use change and changes in traditional agricultural practices. We investigated whether or not agrobiodiversity was declining, the specific causes, and signs of active biodiversity conservation practices in ethnic minority communities of Xishuangbanna which could form the basis for extensive in situ conservation programmes. Methods A series of field studies to document trends in agrobiodiversity were conducted in different ethnic minority communities in Menghai County, Mengla County and Jinghong City of Xishuangbanna of Yunnan Province, southwest of China between July 2015 and February 2016. Data was obtained through the use of semi-structured questionnaires, field observation and participatory rural appraisal (PRA) tools. A total of 360 ethnic households provided information on current status, functions, characteristics, changes, and threatened factors of farming crop and livestock resources. Some measures for in situ conservation of agricultural biological resources were also researched using PRA methods. Results Two hundred twenty-six crop varieties belonging to 31 families, 71 genera and 101 species were identified in Xishuangbanna, which included 83 vegetable crops, 77 food crops, 24 spice crops, 22 fruit crops, 13 cash crops, 6 oil crops, and 1 cloth crop, respectively. There were 15 livestock varieties, belonging to 6 major species: cattle, pigs, goats, chickens, ducks, and geese. Different crop and livestock resources had their own characteristics, functions and threatened factors. Since 2002, agroecosystem, crop diversity and livestock diversity have declined greatly over the Xishuangbanna region as a whole under implementation of the Sloping Land Conversion Program (SLCP). Swidden agriculture was completely eliminated under this program and gradually replaced by large land areas devoted to rubber, tea and banana plantations. Villager numbers engaging in farming production and population of crops and livestock were greatly decreased, particularly in terms of production of local traditional varieties. However, some in situ conservation measures such as seeds preservation, planting of traditional crops and raising livestock have played an important role in local agrobiodiversity conservation. Conclusion Abundant agricultural resources and agrobiodiversity are critical to the local livelihood and maintenance of traditional culture in Xishuangbanna. However, agrobiodiversity and related traditional culture have been greatly impacted by implementation of the SLCP since 2002. Therefore, in future conservation of agrobiodiversity, incorporating some sustainable protection measures based in local communities such as convening seed exchange fairs, conserving traditional varieties in permanent plots, making a visual documentary of indigenous cultivation, and providing traditional agricultural products to tourists should be carefully considered and adopted.

Because cropping systems can greatly affect the establishment and spread of alien species populations, the design of cropping systems to control invasive weeds is an important approach for invasive species management in agro-ecosystems to avoid excessive increases in other control measures such as herbicides. The annual weed Phalaris minor Retz. (P. minor) is one of the most troublesome invasive weed species of winter crops in Yunnan Province, China, but the development of cropping systems for ecological control of this weed have received limited research attention. Here, we studied seed dormancy, germination characteristics and reproductive responses of P. minor to various cropping systems to show how cropping systems could be better designed to control P. minor in China. Our research showed that cropping systems significantly affected seed dormancy in submerged paddy fields. Phalaris minor seed remained dormant and the germination rates (less than 10%) were significantly lower (p &lt, 0.05) than in maize fields and dry, bare soil conditions. Wheat, faba bean and rapeseed crops had no significant influence (p &lt, 0.05) on the seed germination rate of P. minor, but increasing soil depth significantly decreased (p &lt, 0.05) the germination rate and germination index of this weed. Total biomass, spike biomass, spike number and seed number of P. minor were significantly reduced (p &lt, 0.05) with increasing proportions of the three crops (wheat, faba bean and rapeseed), with rapeseed having the strongest inhibition effects among the three crops. The reproductive allocation and reproductive investment of P. minor were also significantly reduced (p &lt, 0.05) in mixed culture with wheat and rapeseed. With increasing proportions of wheat or rapeseed, the specific leaf area of P. minor significantly increased (p &lt, 0.05), but the reverse was true for leaf area and specific leaf weight. Moreover, the net photosynthetic rate, stomatal conductance and transpiration rate for P. minor also decreased significantly (p &lt, 0.05) when grown with wheat or rapeseed. These results suggest that optimal cropping systems design could involve planting rapeseed in conjunction with deep plowing and planting rice (continuous submergence underwater) in summer. Such a system could reduce the field populations and seed bank of P. minor, thus providing a sustainable and environmentally friendly means of suppressing P. minor.

Background As a means of biologically controlling Mikania micrantha H.B.K. in Yunnan, China, the influence of sweet potato [Ipomoea batatas (L.) Lam.] on its reproductive characteristics was studied. The trial utilized a de Wit replacement series incorporating six ratios of sweet potato and M. micrantha plants in 25 m2 plots over 2 years. Results Budding of M. micrantha occurred at the end of September; flowering and fruiting occurred from October to February. Flowering phenology of M. micrantha was delayed (P