Biological Control of Weeds

An indigenous fungal culture, isolated from diseased water hyacinth, in Bolpur, Santiniketan, West Bengal, India, was found to be causing severe blight and dieback disease on water hyacinth, under laboratory and field conditions. It was subjected to morphological and molecular characterization by amplification of 18S RNA gene fragment from genomic DNA using 18S gene universal primers. Subsequently with sequencing, Gen Bank database comparisons and phylogenetic analysis, the fungus was determined as Alternaria japonica Yoshii. Further the pathogen was evaluated for its host specificity to be developed as mycoherbicidal agent against this invasive weed. Host range of A. japonica was screened against 48 plant species in 42 genera representing 22 families in pot experiment. Water hyacinth was the only species strongly susceptible to spore suspension (5 × 105 conidia/ml) of A. japonica. Minor infection was observed on goosefoot which is not only a weed but also ecologically separated fro...

This chapter mainly informed about the management of the weeds of different grain crops, vegetables, flower crops, oil crops, and others. The weeds were very damaging to main product the quality crops/fruits and this paper study on the inform about weed and how to management the weeds in field. Here is also focus on the common crops and their weeds and common name, scientific name and also added the herbicide name to manage weeds in different plants. The farmers used balance fertilizer and also used chemical insecticides to minimize crop damage. It has been estimated that of the average at 36.5% of total losses where 6.2% by weeds. This chapter has efforted the prescription to the weed management in farmer fields. Hence, I think if this book is available for all agriculturists and farmers then they will benefit.

The possibility of pathogenic fungi studied on Avena fatua in the laboratory and greenhouse of Islamic azad university- arak branch at 2012-13. Mycoherbicide activity of the fungi which resulted finaly to intraducing the isolate 1 of Alternaria alternata as a biologic control agent for the weed. Result of this study indicated that there is a significant difference between used fungus and glyfosate fungicide (as a chemical fungicide) in dry weight of root (gr) and total dry weight root in %1 and %5 subsequently. Disease severity in the isolate A1was significantly more than the others.

Chenopodium album is a worldwide-distributed plant species growing in disturbed habitats. It is an abundant and very competitive weed in spring-sown crops, particularly if they retain an open structure for a relatively long period. In most crops it is currently controlled by herbicides. In some crops, such as maize, chemical control is difficult, because C. album has become resistant to

Weeds are a major constraint to crop production, and are responsible for considerable yield losses in maize production systems throughout the world. Herbicides are widely used for weed control in maize production systems, but can have negative environmental consequences. Researchers have evaluated the use of crop competition and suppression to manage weeds in various crop combinations, including maize-based systems. Crop competition in maize may involve techniques such as reduced row spacing, increased planting density, and the use of competitive cultivars that exhibit weed suppressive potential. In this review, examination of the literature has revealed the considerable value of using crop competition in integrated weed management programs. Research has demonstrated that narrowing row spacing to half the standard distance reduced weed biomass by 39e68%, depending on weed species. Researchers have also demonstrated that increasing maize planting density by up to twice the standard rate achieved a reduction in weed biomass of 26e99%. While little research has been conducted into the use of competitive maize cultivars for weed management, several studies have documented cultivars with potential to suppress weeds. Attributes of weed competitive cultivars include high leaf area index, and other elements of leaf architecture that improve light interception by the crop, so increasing the shading of weeds. Combining crop competition methods with other agronomic practices can increase their effectiveness in controlling weeds. For example, biomass of Setaria italica (L.) Beauv was reduced by 60% when maize planting density was increased by 1.5 times the recommended spacing, and this effect was more pronounced when fertilizer was banded rather than broadcast. In summary, the strategic use of crop competition to control weeds has been a success in many regions, and is an important tool in integrated weed management. The importance of crop competition methods has particular relevance where farmers are unable to afford herbicides, as making use of crop competition is more economical.

One of the major issues facing humankind is global food security. A changing climate, coupled with a heightened consumer awareness of how food is produced and legislative changes governing the usage of agrichemicals for improving plant health and yield, means that alternative, more integrated and sustainable approaches are needed for crop management practices. To this end, there is increasing recognition of the value of the role of microbial inoculants in agriculture. The focus of this review is to understand how plant-growth-promoting bacteria and arbuscular mycorrhizal fungi can play a part in improving crop yield by promoting the health status of the plant through the sequestration of various nutrients and in the control of plant diseases.

The essential oil composition of Juniperus phoniceae, Pistacia vera and Pistacia terebinthus was analyzed by GC and GC-MS analysis and their bioherbicidal activity was evaluated against four weeds species, Sinapis arvensis, Trifolium campestre (dicots), Lolium rigidium and Phalaris canariensis (monocots). Qualitative and quantitative differences between oils were observed. All oils were rich in monoterpene hydrocarbons, the major constituents of J. phoniceae were -pinene (49%) and -terpinene (8%) and the major components in P. vera and P. terebinthus were -pinene (16-19%),terpinene (32-41%) and limonene (4-25%). Tested oils strongly inhibited the germination and seedling growth of all weeds, in a dose dependent manner with dicots weeds being significantly more sensitive than monocots, indeed, at the dose of 4 l/ml, germination of S. arvensis and T. campestre was totally inhibited, while for the same dose, germination and seedling growth of L. rigidium and P. canariensis were partially reduced. Essential oils increased the level of proline and caused a severe electrolyte leakage from the roots of all tested weeds indicating membrane disruption and loss of integrity. Our results show that essential oils of forestry trees have an important phytotoxic effect on seed germination and seedling growth of weeds. The phytotoxic activity of the essential oils may be attributed to their relatively high content of monoterpene hydrocarbons. It can be suggested that these essential oils have the potential to be used as a bioherbicide.

Penelitian yang bertujuan untuk menguji potensi jamur Fusarium sp. sebagai agen pengendali hayati gulme eceng gondok telah dilakukan di rumah plastik Fakultas Pertanian Universitas Mataram, Percobaan faktorial dirancang dengan Rancangan Acak Lengkap (RAK) yang terdiri dari dua faktor yaitu lama kebasahan dan waktu aplikasi. Perlakuan lama kebasahan terdiri dari 0, 3, 6, 9, atau 12 jam dan aplikasi dilaksanakan pada pagi atau sore hari. Hasil penelitian menunjukkan bahwa penyakit yang ditimbulkan oleh Fusarium sp. pada eceng gondok lebih parah dan berkembang lebih cepat ketika eceng gondok dipaparkan pada suhu yang lebih tinggi segera setelah inokulasi, dan tidak tergantung pada lama kebasahan ketika diaplikasikan pada pagi hari. Jamur ini tidak dapat menginfeksi beberapa tanaman budidayam sehingga aman digunakan sebagai agen pengendali hayati gulma eceng gondok.

Herbivory is a fundamental process that controls primary producer abundance and regulates energy and nutrient flows to higher trophic levels. Despite the recent proliferation of small-scale studies on herbivore effects on aquatic plants, there remains limited understanding of the factors that control consumer regulation of vascular plants in aquatic ecosystems. Our current knowledge of the regulation of primary producers has hindered efforts to understand the structure and functioning of aquatic ecosystems, and to manage such ecosystems effectively. We conducted a global meta-analysis of the outcomes of plant–herbivore interactions using a data set comprised of 326 values from 163 studies, in order to test two mechanistic hypotheses: first, that greater negative changes in plant abundance would be associated with higher herbivore biomass densities; second, that the magnitude of changes in plant abundance would vary with herbivore taxonomic identity. We found evidence that plant abundance declined with increased herbivore density, with plants eliminated at high densities. Significant between-taxa differences in impact were detected, with insects associated with smaller reductions in plant abundance than all other taxa. Similarly, birds caused smaller reductions in plant abundance than echinoderms, fish, or molluscs. Furthermore, larger reductions in plant abundance were detected for fish relative to crustaceans. We found a positive relationship between herbivore species richness and change in plant abundance, with the strongest reductions in plant abundance reported for low herbivore species richness, suggesting that greater herbivore diversity may protect against large reductions in plant abundance. Finally, we found that herbivore–plant nativeness was a key factor affecting the magnitude of herbivore impacts on plant abundance across a wide range of species assemblages. Assemblages comprised of invasive herbivores and native plant assemblages were associated with greater reductions in plant abundance compared with invasive herbivores and invasive plants, native herbivores and invasive plants, native herbivores and mixed-nativeness plants, and native herbivores and native plants. By contrast, assemblages comprised of native herbivores and invasive plants were associated with lower reductions in plant abundance compared with both mixed-nativeness herbivores and native plants, and native herbivores and native plants. However, the effects of herbivore–plant nativeness on changes in plant abundance were reduced at high herbivore densities. Our mean reductions in aquatic plant abundance are greater than those reported in the literature for terrestrial plants, but lower than aquatic algae. Our findings highlight the need for a substantial shift in how biologists incorporate plant–herbivore interactions into theories of aquatic ecosystem structure and functioning. Currently, the failure to incorporate top-down effects continues to hinder our capacity to understand and manage the ecological dynamics of habitats that contain aquatic plants.

The invasive tree Solanum mauritianum Scop. has been targeted for biological
control in South Africa and New Zealand, by deploying insect agents that
could constrain its excessive reproductive output. The flower-feeding weevil
Anthonomus santacruzi (Curculionidae) was approved for release in South Africa
in 2007 but following the loss of the original culture in quarantine, new stocks
were introduced from Argentina in 2008
2009. This study was initiated to
confirm that the host range of the new culture was the same as that of the
previous one, but also to assess the risks associated with the weevil’s release in
New Zealand. Different testing procedures, including no-choice tests and multichoice
tests in different arenas, produced inconsistent and ambiguous results.
During no-choice tests, oviposition and larval development to adulthood
occurred on three non-target species including two native South African and
one native New Zealand Solanum species. However, subsequent multi-choice tests
and a risk assessment suggested that the risks of anything more than collateral
damage to non-target Solanum species are low. Overall, these data do not deviate
substantially from the results of the original quarantine tests which facilitated the
release of A. santacruzi in South Africa in 2009. Although we argue that none of
the New Zealand native and cultivated species are at risk, stronger evidence from
open-field trials and chemical ecology studies may be required to convince the
regulatory authorities that A. santacruzi is suitable for release in New Zealand.

As a result of the increasing environmental and health-related problems caused by the synthetic agrochemicals currently used, suitable and non-hazardous innovative alternatives are being sought. Antagonism and allelopathy, both in nature and in agro-ecosystems, have attracted these researchers' attention, with the main goal of using these phenomena in the biological control of weeds. This article presents a review on the use and efficacy of microbial secondary metabolites which have potential as natural herbicides, either directly or as templates for bio-rational eco-friendly agrochemicals (allelochemicals). Their merits as alternatives to synthetic chemicals and biological control agents have been highlighted for an holistic approach in integrated pest/weed management.

Weed control in smallholder farming systems of sub-Saharan Africa is labour intensive or costly. Many researchers have therefore advocated for the use of cover crops in weed management as an affordable alternative for smallholders. Cover crops may be grown in rotations to suppress weeds and reduce the reliance on herbicides. The use of cover crops creates microenvironments that are either conducive or inhibitive to the emergence of certain weed species. A study, initiated in 2008 in contrasting soils at four different locations of Zimbabwe, investigated the effect of maize (Zea mays L.)-cover crop rotations on the emergence of weeds that showed dominance in those soils. Weed assessments were however, carried out from 2011 to 2014. The weed species Galinsoga parviflora Cav., Commelina benghalensis L., and Richardia scabra L. showed dominance in all four locations with weed densities as high as 500 plants m À2 being recorded for R. scabra L. in a sandy soil. Maize-cover crop rotations resulted in higher densities of Bidens pilosa compared with maize monocropping (control treatment) due to its high nitrogen (N) requirement to produce more seeds. On the other hand, the integration of cover crops such as pigeon pea [Cajanus cajan (L.) Millsp.] that had poor shading qualities, due to large gaps or spaces and slower initial growth, had limited effects on competitive weeds such as Cyperus esculentus L. which tend to dominate exhausted soils. The density of C. esculentus was 38% greater in maizeepigeon pea rotations compared with the control treatment. Variability between seasons and sites affected emergence of all weeds in the present study, which masked long-term trends. The results suggest that there is need to identify the germination and emergence requirements of specific weeds and select cover crops best suitable for their control. The study provides useful information for farmers and advisors on the best cover crops for control of certain problematic weeds in different soil types of Zimbabwe.

Manjunath, T.M. and Mohan, K.S., 1999. Insect-resistant transgenic crops : A new tool in integrated pest management. Presented at the RYTHU UTSAVAM ‘99, Govt. of Andhra Pradesh and The Federation of Andhra Pradesh Chambers of Commerce and Industry, Hyderabad, March 18-22, 1999, 3 pages. - The insect-resistant transgenic crop has several unique features: (a) it has a built-in caterpillar control mechanism, independent of weather factors, (b) the toxin is expressed in the whole plant, day and night, throughout the season, (c) neonate larvae cease feeding within hours of ingesting the plant tissue and therefore damage to crop is very minimal, (d) larval populations that might have developed resistance to chemical insecticides are also killed, (e) safe to biological control agents, non-target organisms, plants and environment, (f) no special efforts are required to grow transgenic crop as it can be grown like any other normal crop, and (g) it relieves the farmers of the tension of continuous monitoring of the target pests and provides a lot of free time so that they can concentrate on other crop management issues. Moreover, transgenic technology can be easily integrated with other control methods like biological, cultural, mechanical, pheromones and even chemical pesticides. It provides the much needed strength and stability to IPM. Thus, agricultural crop production throughout the world is poised to realize the benefits of transgenes for pests/disease management and quality improvement.

The goals in selecting classical biological control agents for weeds are to identify agents that will be both safe for release and effective in controlling their target plants. The release of ineffective agents should be avoided, as these add to the costs and risks of biological control without contributing to its benefits. While the principles of host-specificity testing and risk assessment for weed biological control agents have been extensively debated and refined, there has been less attention given to assessing the probable efficacy of agents prior to release. This reluctance to undertake pre-release efficacy assessment (PREA) is probably based on concerns that it will both add to the cost of screening biological control agents and introduce a risk of wrongly rejecting effective agents. We used a project simulation model to investigate the implications of using PREA as an additional filter in the agent selection process. The results suggest that, if it can be done at a lower cost than host-specificity testing, the use of PREA as the first filter can make agent selection more cost-effective than screening based on host-specificity alone. We discuss examples of PREA and potential approaches. The impact of biocontrol agents is a function of their range, abundance, and per-capita damage. While it will always be difficult to predict the post-release abundance of biological control agents from pre-release studies, some estimates of potential range can be obtained from studies of climatic adaptation. For agents that affect the vegetative growth or survival of their target weeds, experimental measurement of per-capita damage is feasible and can contribute to a reduction in the numbers of ineffective agents released. The Anna Karenina principle states that success in complex undertakings does not depend on a single factor but requires avoiding many separate causes of failure. We suggest that, in biological control of weeds, the use of agents that are not sufficiently damaging is one such cause that can be partially avoided by the use of pre-release efficacy assessment.

District Malakand lies on the northern side of Khyber Pakhtunkhwa province of Pakistan. The landscape represents both plain and hilly regions. Various kinds of crops are grown among which wheat is cultivated on large scale. In order to explore weed species diversity in the region, a phytosociological survey was conducted in the summer 2014. Such study was required as there has been no such record of weeds diversity of the region. Different fields were selected at various localities of the district. The total number of fields selected was 120 and in each field 10, 1x1m 2 quadrats were laid. A questionnaire was also circulated to investigate about the farming practices and most dangerous species of weeds having greater effect on production and post harvest losses of wheat. Plants were collected from various localities, voucher numbers were given to specimens and other relevant data pertaining to locality i.e., habitat, habit, family, scientific and local names of each species. Mounted copy of each voucher specimen was deposited to the Herbarium of Hazara University Mansehra. This study not only provided first inventory of weed plants but it also helped point out most dangerous species related to wheat yield losses. Results of this study revealed a total of 132 weeds plant species belonging to 110 genera and 42 families. Most of the species investigated were Angiosperms. Family Asteraceae was the richest family related to species diversity with 18 species and 17 genera. It is followed by Poaceae having 16 species and 16 genera. Next in succession are family Brasicaceae with 10 genera and 16 species and family Boraginaceae with 5 genera and 7 species. Other families like Caryophyllaceae, Papilionaceae, Fabaceae, Polygonaceae, Scrophulariaceae and Umbilliferae have 6,6,4,5,4 and 3 species and 6,3,4,3,3 and 3 genera respectively. Species like Silybum marianum (Asteraceae), Emex spinosa (Polygonaceae) and Circium arvense (Asteraceae) are considered to be the most threatening species during the time of harvesting the crop. Further study along this line is the basic part of the on-going project which will provide a base line for the development of agricultural crops in the region.

Manjunath, T. M., 1992. Biological control of insect pests and weeds in India: Notable successes, pp. 11-21. In (Ed. Yoshimi Hirose) “Biological Control in South and East Asia,” Kyushu University Press, IOBC/SEARS, Inst. of Biological Control, Kyushu Univ., Fukuoka 812, Japan, 68 pp. -
The work on biological control in India made significant progress over the last few decades, utilizing indigenous or exotic natural enemies of insect pests and weeds. The notable successes achieved through releases of indigenous natural enemies include the control of insect pests like sugarcane borers, sugarcane pyrilla, scale insects, cotton bollworms, coconut black-headed caterpillar, mealybugs, etc. while those with exotic  natural enemies  include the control of soft scales and mealybugs, apple woolly aphid,  apple codling moth, su-babul psyllid, etc. Similarly, some degree of success was also obtained in controlling weeds like prickly pear, water hyacinth, Salvinia, Parthenium, etc. through introduction of natural enemies from other countries. The natural enemies involved and the role played by them are highlighted.

The use of molecular techniques is rapidly growing as the tools have become more diverse and powerful, more widely available, and easier to implement. Molecular analyses are able to elucidate information about target weeds that is critical to improving control success, such as taxonomic clarification, evidence of hybridization and cryptic species, better development of test plant lists, population structure and origin of invasions. Similarly, molecular approaches can improve our knowledge of biological control agents, providing taxonomic clarity, identification of immature arthropods and fungal pathogens, and description of genetic variability in agents. Molecular tools also allow easier identification of host associations and provide a tool for post-release evaluation and tracking of agents. This review provides an overview of how to use molecular approaches in biological control of weeds, with the aim of assisting the adoption and facilitating fruitful collaboration between scientists studying the biology and ecology of agents and their targets and those with skills using molecular approaches. We describe the current molecular techniques relevant to classical biological control of weeds, instruct how to collect field materials for molecular analyses, and give recent examples of the use of molecular methods in biological control of weeds, with comments on the most appropriate methods for analysis of molecular data.

Nodding thistle receptacle weevil Rhinocyllus conicus and gallfly Urophora solstitialis attack the capitula of nodding thistle Carduus nutans L. Between 31 October and 15 December 2003, the phenology of both R. conicus and U. solstitialis was studied at a dryland site in Canterbury. Adult R. conicus were more numerous than U. solstitialis on capitula throughout the experiment. Larvae of R. conicus were fi rst found on 11 November (15% of capitula infested) and peaked on 2 December with 53% of capitula infested. Only 3% of capitula were infested by U. solstitialis. Adult R. conicus or U. solstitialis emerged from 79% of the selected primary and secondary capitula. The majority of infested capitula (81%) contained only R. conicus, 2% contained only U. solstitialis while 17% contained both insect species. Parasitism of R. conicus by the braconid parasitoid Microctonus aethiopoides was low and occurred when most weevil eggs had been laid.

The discovery and quantification of significant non-target ecological effects of Rhinocyllus conicus on native species in the northcentral USA provides the opportunity to experimentally evaluate factors that might help predict non-target host plant use, magni- tude of direct impact with transference, and indirect effects mediated by trophic interac- tions. The relevance for biocontrol risk assessment of at least four important

Biological control of weeds by using plant pathogens has gained acceptance as a practical, safe, environmentally beneficial, weed management method applicable to agroecosystems. The interest in this weed control approach from public and private groups, and support for research and developmental effort, are on the upswing. This increasing interest is stimulated largely due to major economic, social, and environmental forces that are directing our choices in crop production practices. Some of these changes are market-driven while others are social and ecological in nature. These changes are in turn influencing the choices in weed control methods. In this regard, biocontrol with plant pathogens has been proven a feasible, albeit minor, component of modern integrated weed-management systems. This environmentally beneficial method should be promoted and exploited further to meet the current and future challenges in weed management in agro-ecosystems.

The adverse effects of the weed flora on the agricultural yield are well documented. In an agroecosystem, weed species distribution pattern depends on both surrounding environment and farming
practices. This first ever study was designed to compare and determine the weed species richness,
distribution pattern and their ecologically meaningful groups in wheat and maize field of Gujrat, Pakistan.
In this study, seasonal variation variable and satellite derived measurements like normalized difference
vegetation index (NDVI), normalized difference moisture index (NDMI) and topographic wetness index
(TWI) were calculated for each vegetation sample and their contribution towards explaining variations in
the weed species data was tested by using direct unimodal ordination method. Phytosociological data was
collected from 50 crop fields (25 each from wheat and maize fields during winter and monsoon season
respectively) comprising of 250 sub-samples/plots (size 1 × 1 m) during 2016. The results of Monte Carlo
testing and cluster analysis showed that there were four statistically significant weeds groups (i.e. 1.
Anagallis-Medicago-Phalaris or AMP-Wheat weed group; 2. Chenopodium-Convolvulus-Vicia or CCVWheat weed group; 3. Cyperus Malva-Amaranthus or CMA-Maize weed group; 4. Cannabis-CynodonDigera or CCD-Maize weed group). A total of 60 weed species were recorded and the majority of them
belongs to Poaceae and Amaranthaceae families. The majority of weed species flowered during monsoon
season whereas therophytic life form and microphyllous leaf size categories were the most dominant. The
highest mean weed diversity, NDVI and NDMI values were recorded for the weed communities of maize
fields whereas the higher mean TWI value was recorded for the weed groups of wheat fields, suggesting
strong linkage with the local climatic conditions. Canonical correspondence analysis (net effects)
suggested that sum of local climatic conditions (seasonality variable) was found to be the most important
in controlling the variations in the weed species data followed by longitude and altitude variables and
least by the NDVI, NDMI and TWI. It is concluded that effective weed management activities are
required to enhance the yield of these two important crops in the area. Thus, further studies related to
determination of weed types and their distribution pattern by using factors like fertilization (type, timing,
quantity), wheat and maize cultivar, land preparation (types, timing and intensities), soil management,
pesticides (usage, type, quantity, quality), irrigation (type like rain-fed, tube-well, canals; timing,
quantity), socio-economic and anthropogenic activities, and their relationship with the yield variable on
temporal and spatial scales are recommended for this agro-ecosystem of the study area.

The allelopathic properties of plants can be exploited successfully as a tool for pathogen and weed reduction. Over a decade, preliminary surveys of some hundred allelopathic plants in the Southeast Asia and Japan ecosystems were made, and more than 30 species including crops which exhibited the greatest allelopathic potential were selected and examined for their impacts on emergence of pathogens and weeds. Observations showed that application of these plant materials at 1-2 tonne ha À1 can reduce weed biomass by about 70%, and increase rice yield by about 20%. Some species showed strong inhibition on major plant pathogens and they might become effective tools in reducing plant pathogens and weeds. However, application of 1-2 tonne ha À1 of plant material to the field makes heavy fieldwork. Numerous growth inhibitors identified from these allelopathic plants are responsible for their allelopathic properties and may be a useful source for the future development of bio-herbicides and pesticides. r

The eriophyid mite Leipothrix dipsacivagus Petanovic et Rector provokes severe malformations to its host plant, cut-leaf teasel (Dipsacus laciniatus L.), in the field. These injuries were examined at the morpho-anatomical level in infested plants collected in the field and experimentally infested plants kept under controlled laboratory conditions. A number of symptoms were observed including reduced growth, internode shortening, leaf rolling and wrinkling, and shrunken inflorescences. After severe attack, the leaves of bolted plants became chlorotic with necrotic spots and started to wilt. Young rosettes died. Morphometric analysis revealed significant differences between infested and healthy field-collected bolting plants. Infested plants were significantly shorter than healthy plants, with smaller leaves and flower heads. Striking injuries were also observed on young leaves of experimentally infested plants. It is expected that further investigations will elucidate the full extent of the damage to aboveground parts of D. laciniatus due to infestation by L. dipsacivagus.

Weeds are enemies to the crop plants and have harmful effects on agricultural crops due to several factors such as competition for space, light and nutrients. Allelopathic effects of weed extracts were studied on grain yield and yield components of rice. The experiment was carried out in the Rice Research Institute of Chaparsar, in 2006-2007, in Tonekabon, Iran (latitude 36°54' N, longitude 50° 40'E, level-20 m altitude), split plot on basis of randomized completely block design (RCBD) with 4 replications. Results showed highly significant differences suggesting substantial to moderate phenotypic variability in most parameters evaluated except number of empty grain and 1000-grain weight. Also, most yield of single plant obtained from umbrella sedge extract (28.5 g). It seems that umbrella sedge had least minerals in water; it could be affected positively on important factors such as yield of single plant compared to other treatments. Correlation coefficient analysis revealed significant and negative correlation between number of empty grain and yield of single plant (r=-0.42 ***). It's implies that grain yield magnitude of Nemat cultivar exhibiting the least number of empty grain. Although yield of single plant was not affected neither by plant height nor number of tiller. In addition, irrigation water due to existence of high mineral and chemical pesticides in upstream of station farms severely was reduced yield. Also, results of this research showed that weed extracts haven't very allelopathic effect on rice and in end of growing season, that's better, plant leftover return and remain in field.

The present study describes micro-morphological and histological changes to rosette leaves of the native Eurasian plant species Dipsacus laciniatus (Dipsacaceae) provoked by infestation of the eriophyid mite Leipothrix dipsacivagus Petanovic et Rector. Conspicuous injuries to the leaf tissue were induced by mites feeding on leaves of D. laciniatus rosettes that were propagated from seed under laboratory conditions. Anatomical injuries extended into epidermal cells on the upper and lower leaf surface as well as to the mesophyll layer of infested D. laciniatus leaves. Statistical analysis (by ANOVA and MANOVA) showed significant differences between control and infested plants, particularly in total leaf thickness. The most striking change observed was the decrease in thickness of infested leaves, beginning from the 8th week, associated with the progressive replacement of epidermal cells with an acellular layer. Measures of mite density on test leaves indicated that mites vacated leaves as russeting symptoms intensified. They also appeared to vacate all leaves, whether symptomatic or not, after populations peaked 10–12 weeks after infestation. Comparisons were made between these studies and those on naturally infested, field-collected D. laciniatus plants, as well as with similar studies of other mite-plant interactions.

Transdisciplinary weed research (TWR) is a promising path to more effective management of challenging weed problems. We define TWR as an integrated process of inquiry and action that addresses complex weed problems in the context of broader efforts to improve economic, environmental and social aspects of ecosystem sustainability. TWR seeks to integrate scholarly and practical knowledge across many stakeholder groups (e.g. scientists, private sector, farmers and extension officers) and levels (e.g. local, regional and landscape). Furthermore, TWR features democratic and iterative processes of decision-making and collective action that aims to align the interests, viewpoints and agendas of a wide range of stakeholders. The fundamental rationale for TWR is that many challenging weed problems (e.g. herbicide resistance or extensive plant invasions in natural areas) are better addressed systemically, as a part of broad-based efforts to advance ecosystem sustainability, rather than as isolated problems. Addressing challenging weed problems systemically can offer important new leverage on such problems, by creating new opportunities to manage their root causes and by improving complementarity between weed management and other activities. While promising, this approach is complicated by the multi-dimensional, multilevel, diversely defined and unpredictable nature of ecosystem sustainability. In practice, TWR can be undertaken as a cyclic process of (i) initial problem formulation, (ii) 'broadening' of the problem formulation and recruitment of stakeholder participants, (iii) deliberation, negotiation and design of an action agenda for systemic change, (iv) implementation action, (v) monitoring and assessment of outcomes and (vi) reformulation of the problem situation and renegotiation of further actions. Notably, 'purposive' disciplines (design, humanities and arts) have central, critical and recurrent roles in this process, as do integrative analyses of relevant multidi-mensional and multilevel factors, via multiple natural and social science disciplines. We exemplify this process in prospect and retrospect. Importantly TWR is not a replacement for current weed research; rather, the intent is to powerfully leverage current efforts.

Field trials were conducted in 2007 and 2008 early and late wet seasons, respectively at the Federal University of
Agriculture Abeokuta (070 20`N, 30 23`E) in the forest-savanna transition agroecological zone of South-western
Nigeria. Five weed control treatments viz pre-emergence application of commercial formulation of metolachlor
plus prometryne (Codal GoldR, 412 EC) at 1.6kg a.i/ha alone, 1.6kg a.i/ha followed by supplementary hoe weeding
at 6 weeks after planting (WAP), 2.4kg a.i/ha, two hoe weedings at 3 and 6 WAP and a weedy check were assigned
to the main plots while intercropping methods which included four combinations of groundnuts between rows of
maize spaced at 50cm and 75cm, as well as sole crops of maize and groundnut constituted the sub-plot treatments. Intercropped groundnut significantly suppressed weed infestation compared with the sole crops of maize and groundnut. Weed infestation was consistently lower in maize planted at intrarow spacing of 75cm in mixture with three groundnut stands in the inter-row between two maize stands and maize planted at 50cm in similar mixture with two groundnut stands compared with the other cropping methods. In both years of study, maximum cob and grain yields were obtained with sole maize spaced at 50cm within rows. Intercropped maize at 75cm produced grain yield comparable to the corresponding sole crop in both years. Intercropped groundnut in maize spaced at 50cm significantly reduced grain yield of maize in 2007 and non-significantly in 2008 compared to the corresponding sole crop. All the weed control methods evaluated resulted in significantly lower weed cover score than the weedy check.

We conducted a previous systematic and meta-analysis review that showed differences in results from studies that evaluated the effectiveness of cover crops for weed suppression in cropping systems; these differences were largely due to management approaches used in growing the cover crop and main crop. The current meta-analysis provides a quantitative review on how cover crop and main crop management practices influence the impact of cover crops on weed
suppression. The meta-analysis used observations from 53 studies published from 1990 to 2018. Cover crop biomass was inversely related
to the amount of weed biomass (r2 = 0.67) and weed density (r2 = 0.64). In general, the meta-analysis shows that cover crops provided a range
of weed suppression depending on management decisions such as choice of cover crop species, cover crop sowing season (fall or spring), sowing dates within seasons, seeding rate, termination date, delay in main crop planting date after cover crop termination, tillage system under which the cover crop was produced, and integrating the cover crop with other weed control inputs. For example, grass cover crop species provided greater weed suppression than broadleaf species. Fall-sown cover crops provided greater weed suppression (weighted mean of response ratio [R*] = 0.19) than spring-sown cover crops (R* = 0.48) by the summer. Weed suppression increased by increasing seeding rate of cover crops from 1´ (R* = 0.50) to 2´ (R* = 0.27) or 3´ (R* = 0.10). In addition, cover crops provided greater weed suppression in reduced tillage systems (R* = 0.19) than no tillage (R* = 0.29). The differential weed suppression provided by these management approaches suggests that a cover crop management approach should be rightly selected for weed suppression benefits.

The allelopathic properties of plants can be exploited successfully as a tool for pathogen and weed reduction. Over a decade, preliminary surveys of some hundred allelopathic plants in the Southeast Asia and Japan ecosystems were made, and more than 30 species including crops which exhibited the greatest allelopathic potential were selected and examined for their impacts on emergence of pathogens and weeds. Observations showed that application of these plant materials at 1-2 tonne ha À1 can reduce weed biomass by about 70%, and increase rice yield by about 20%. Some species showed strong inhibition on major plant pathogens and they might become effective tools in reducing plant pathogens and weeds. However, application of 1-2 tonne ha À1 of plant material to the field makes heavy fieldwork. Numerous growth inhibitors identified from these allelopathic plants are responsible for their allelopathic properties and may be a useful source for the future development of bio-herbicides and pesticides. r

Nonindigenous invasive plants pose a major threat to natural communities worldwide. Biological control of weeds via selected introduction of their natural enemies can affect control over large spatial areas but also risk nontarget effects. To maximize effectiveness while minimizing risk, weed biocontrol programs should introduce the minimum number of host-specific natural enemies necessary to control an invasive nonindigenous plant. We used elasticity analysis of a matrix model to help inform biocontrol agent selection for garlic mustard (Alliaria petiolata (M. Bieb.) Cavara and Grande). The Eurasian biennial A. petiolata is considered one of the most problematic invaders of temperate forests in North America. Four weevil species in the genus Ceutorhynchus (Coleoptera: Curculionidae) are currently considered potential biocontrol agents. These species attack rosettes (C. scrobicollis), stems (C. roberti, C. alliariae), and seeds (C. constrictus) of A. petiolata. Elasticity analyses using A. petiolata demographic parameters from North America indicated that changes in the rosette-to-flowering-plant transition and changes in fecundity consistently had the greatest impact on population growth rate. These results suggest that attack by the rosette-feeder C. scrobicollis, which reduces overwintering survival, and seed or stem feeders that reduce seed output should be particularly effective. Model outcomes differed greatly as A. petiolata demographic parameters were varied within ranges observed in North America, indicating that successful control of A. petiolata populations may occur under some, but not all, conditions. Using these a priori analyses we predict: (1) rosette mortality and reduction of seed output will be the most important factors determining A. petiolata demography; (2) the root-crown feeder C. scrobicollis will have the most significant impact on A. petiolata demography; (3) releases of single control agents are unlikely to control A. petiolata across its full range of demographic variability; (4) combinations of agents that simultaneously reduce rosette survival and seed production will be required to suppress the most vigorous A. petiolata populations. These predictions can be tested using established long-term monitoring sites coupled with a designed release program. If demographic models can successfully predict biocontrol agent impact on invasive plant populations, a continued dialogue and collaboration between empirical and theoretical approaches may be the key to the development of successful biocontrol tactics for plant invaders in the future.

Tibouchina herbacea (DC.) Cog. is an ornamental plant introduced purposefully in the Hawaiian archipelago and due to the absence of natural enemies and adequate soil and climate conditions, it has spread in many native forests and humid regions of the main Hawaiian Islands. As the plant is originally from Brazil, it has been made several exploratory trips in order to search for specific natural enemies to control this plant. Among the selected agents with impact and potential for specificity to T. herbacea, the most effective is Sypharea uberabensis (Bechyne, 1955 (Coleoptera: Chrysomelidae). This
work presents studies about the biology, the ecology and the specificity of this insect and also an evaluation of the possible impacts caused by this natural enemy in the population of the plant.

A new species of the genus Dinotrema Foerster is reported from the Samsun region on the central Black Sea coast of Turkey. The genus generally parasitizes flies and ranks among the most species-rich taxa of the Braconidae. Morphological details of the new species Dinotrema samsunense Fischer & Sullivan are described, figured, and compared taxonomically with the most closely related species.

Manjunath, T. M., 2017. Genetic Options for Insect Pest Management. Presented at the Biotech Session 5 on “Future Technologies in Agriculture/Gene Editing for Better Crops” on 17th November 2017 at the Bangalore Tech Summit 2017, organized by Karnataka Biotechnology and Information Technology Services (KBITS), Govt. of Karnataka, Palace Ground, Bengaluru, 16th -18th November 2017:
Genetic Engineering, Genome Editing and Genetic Disruption are a few among the genetic techniques that can be exploited in various ways for insect pest management so as to enable our farmers to obtain better harvests and improve their social and economic status. As no technology can last for ever and no single technology can solve all the problems, there is a continuous need to develop new technologies or improved products, and also integrate various technologies depending upon their suitability so as to manage the pest complex. These are discussed along with regulatory, social and political dimensions associated with their implementation.

-- See also these papers about Artemisia phytoextracts.
PLATYZOA ► https://www.researchgate.net/publication/263714074
NEMATODA ► https://www.researchgate.net/publication/235331332
DIPTERA ► https://www.researchgate.net/publication/235675253
MOLLUSCA ► https://www.researchgate.net/publication/235791811
ALLELOPATHY ► https://www.researchgate.net/publication/235675272
VIRUS & PROCARIOTA ► http://www.researchgate.net/publication/259822587
PROTISTA ► http://www.researchgate.net/publication/264344623

Weeds are enemies to the crop plants and have harmful effects on agricultural crops due to several factors such as competition for space, light and nutrients. Allelopathic effects of weed extracts were studied on grain yield and yield components of rice. The experiment was carried out in the Rice Research Institute of Chaparsar, in 2006-2007, in Tonekabon, Iran (latitude 36°54' N, longitude 50° 40'E, level-20 m altitude), split plot on basis of randomized completely block design (RCBD) with 4 replications. Results showed highly significant differences suggesting substantial to moderate phenotypic variability in most parameters evaluated except number of empty grain and 1000-grain weight. Also, most yield of single plant obtained from umbrella sedge extract (28.5 g). It seems that umbrella sedge had least minerals in water; it could be affected positively on important factors such as yield of single plant compared to other treatments. Correlation coefficient analysis revealed significant and negative correlation between number of empty grain and yield of single plant (r=-0.42 ***). It's implies that grain yield magnitude of Nemat cultivar exhibiting the least number of empty grain. Although yield of single plant was not affected neither by plant height nor number of tiller. In addition, irrigation water due to existence of high mineral and chemical pesticides in upstream of station farms severely was reduced yield. Also, results of this research showed that weed extracts haven't very allelopathic effect on rice and in end of growing season, that's better, plant leftover return and remain in field.

Interspecific interactions play an important role in ecosystem functioning. Several biocontrol agents are being introduced for the control of invasive species like the aquatic macrophyte, waterhyacinth, Eichhornia crassipes, in the hope of improving the eco-friendly natural control mechanism. Due to their overlapping niches, interspecific interactions among the biocontrol agents is high and there is a paucity of information on possible positive or negative impact they may have on each other hence affecting the biocontrol. Therefore studies on their interaction become even more important. In order to understand such possibilities, three potential fungi, Fusarium oxysporum (FO), F. roseum (FR), Paradendryphiella salina (PS) and two hostspecific arthropods Orthogalumna terebrantis (OT) and Neochetina bruchi (NB) were applied on water hyacinth plants singly and in various combinations (OT, NB, FO, FO + OT, FO + NB, FR, FR + OT, FR + NB, PS, PS + OT, PS + NB). Observations were made on percentage damage caused by these agents to water hyacinth. Biocontrol agents applied in combination had cumulative impact on the target weed. FO + NB and FO + OT treated plants showed enhanced damage percentage of about 90%, after 120 h. But FR + NB and PS + NB treated plants were far less damaged compared to when these agents were applied separately. PS also had a repelling effect on NB. Results of such interactions are often variable and less predictable, especially under field conditions. These results demonstrate the need for studies on biotic interactions among biocontrol agents, prior to release of the biocontrol agents of weeds.

Environmental weeds typically invade open, disturbed areas or vegetation edges, and can have devastating ecological and economic consequences. The National Weeds List in Australia informs the public and land managers on weeds prioritized for management, but shade-tolerant weeds that can invade forest ecosystems are inadequately listed. Such weeds are now globally recognized for their ability to impact native vegetation. The Cherry Guava (Psidium cattleianum) from Brazil, a shrub of the Myrtle family (Myrtaceae), is an exceptional example.
1. Cherry Guava was probably introduced to Australia for its edible fruits. The earliest record (1940s) was in Koah, Far North Queensland. Currently, Cherry Guava infestations are found in three World Heritage Areas in Australia: the Wet Tropics in Queensland; Gondwanan Rainforests of Queensland/New South Wales, and Lord Howe Island. It is listed as a noxious weed only in NSW. There are no Australian regulations restricting import or sale.
2. The Global Invasive Species Database lists Cherry Guava among the World’s 100 Worst Weeds – it tolerates shade; grows and matures rapidly; produces a heavy fruit set and seedling bank; is spread by native and feral animals; coppices extensively; and forms multi-stemmed thickets. It can displace native vegetation. Infestations in Australia appear free of natural enemies and resistant to Myrtle Rust which affects co-occurring native members of the Myrtaceae. In Hawaii, Seychelles and Mascarene Islands, natural forested ecosystems are severely impacted after introductions in the early- to mid-1800s.
3. Cherry Guava spread is ongoing, but given the recent Australian history and localized infestations, eradication may be possible with incisive intervention. Government listings and restricting import and sale are first steps. Options to eliminate infestations could combine ecotourism, volunteers and biological control agents.

Context: The synthetic insecticides used to control Diptera are harmful to the environment and humans. Extracts and compounds from plants are a more sustainable source for the development of bio-insecticides. Aims: To evaluate the efficacy of a hydroalcoholic extract of Persea americana Mill seeds as an alternative control of the species Musca domestica. Methods: The extracts were obtained by two methods, the Shaker (S) and the Soxhlet extraction (SE) method, using 94% ethanol as the solvent. Also, the qualitative chemical composition was determined by phytochemical screening. The effect of the two extracts on the post-embryonic development of the fly as well as the adulticidal effect was evaluated. Results: Phytochemical analysis revealed the presence of metabolites such as alkaloids, coumarins, tannins, flavonoids, sugars and amino acids. The influence on the post-embryonic development of M. domestica was demonstrated, especially on the viability of larvae and neolarvae to adults; however, the effect on the weight and duration of each period was low. The adulticidal effects of the extracts were determined by the lethal concentration 50(LC50) of 2.91o mg/100 mL and 3.944 mg/100 mL for the S and SE extracts, respectively. Conclusions: Both extracts showed their insecticidal effects against Musca domestica, but the extract elaborated by S method showed greater influence diminishing viability and better adulticidal effect.

Incorporating population genetics into research on candidate biological control agents can help improve the safety and success rates of biological control of weeds. As a case in point, the population structure of Ceutorhynchus scrobicollis, a candidate agent for garlic mustard (Alliaria petiolata) in North America, was evaluated using mitochondrial sequence data and amplified fragment length polymorphisms (AFLPs). The region surrounding Berlin, Germany, from which individuals have been collected for host-specificity tests, was examined to determine whether individuals from this area constitute one or more populations, to estimate numbers of individuals required to capture 90-99% of the diversity in AFLPs within the region, and to evaluate dispersal capabilities. Significant differentiation of C. scrobicollis between sites was observed, however most (94%) of the genetic diversity was found within sites. The area around Berlin appears to be a network of connected subpopulations. Estimates for the number of individuals needed from the focal area to capture 90% and 99% of the diversity present in AFLP loci were 10 and 27. Assignment tests indicated that while few individuals disperse, some move up to 65 km. Inclusion of more distant samples from Romania and Georgia revealed substantial genetic differentiation between them and German samples. These areas might therefore be useful to explore further should populations with different ecological characteristics be sought. These findings increase confidence in host-specificity tests, which incorporated more than 4000 individual weevils from the Berlin area, provide guidance for eventual release strategies, and illustrate how basic population genetic data can be incorporated into biological control programs to increase safety and efficacy.

The weevils Neochetina eichhorniae and N. bruchi were released in the USA for waterhyacinth control during the early 1970s and have since been used in many other countries. Although successful control has been reported, questions regarding the efficacy of these insects remain unresolved. This lack of consensus may be attributed to the subtle impacts of these agents on plant health and vitality or to unrealistic expectations on the part of evaluators. Previous studies that anticipated impacts to preexisting mats were designed to document declines of established plant populations. This approach overlooks important consequences that occur during plant colonization, because suppression of growth can be as important as reduction of existing populations. We investigated the effects of Neochetina spp. on the expansion of waterhyacinth mats and the subsequent colonization of the surrounding water surface under conditions designed to simulate incipient infestations. Varying numbers of weevils (0 to 4000, in increments of 1000 weevils) were released in early April onto 10-m 2 mats at two sites, one in north Florida and one in south Florida, during 1992 and 1993, respectively. Results were more striking at the northern site. Maximum leaf area was 122 cm 2 in the control vs 65 cm 2 in the 4000-weevil plot. Maximum leaf length was 70 cm vs 51 cm. Plant coverage at the southern site increased only half as fast in the 4000-weevil plot as in controls, and this disparity was even greater at the northern site. Weevil infestations at both sites produced smaller, less intertwined mats and impeded growth of the plants. Weevil dispersal out of the plots at both sites caused weevil numbers to equalize among treatments by midsummer. However, suppression of plant growth in plots receiving the most weevils persisted several months beyond the term during which differences in weevil populations were evident, especially at the northern site. Release of weevils earlier in the year or multiple releases throughout the year might suppress growth even further.