Insect Pest Complex of Wheat Crop

Wheat Triticum aestivum L. is grown on broad range of climatic conditions because of edible grains, cereal crop and stable food of about 2 Billion peoples worldwide. Additionally, it is the rich source of carbohydrates (55–60%), vegetable proteins and contributed 50–60% daily dietary requirement in Pakistan. Globally, wheat crops is grown over 90% area of total cultivated area; facing devastating biotic and abiotic factors. The estimated economic losses in wheat quantity and quality are about 4 thousands per tonne per year including physical crop losses and handling. Economic losses of about 80–90 million USD in Pakistan are recorded due to inadequate production and handling losses. Wheat agro-ecosystem of the world colonizes many herbivore insects which are abundant and causing significant losses. The feeding style of the insects made them dispersive from one habitat to another imposing significant crop loss. Areas of maximum wheat production are encountered with either insect which chew the vegetative as well as reproductive part or stem and root feeders. This chapter provides the pest’s taxonomic rank, distribution across the globe, biology and damage of chewing and sucking insect pest of wheat. It is very important to study biology of the pest in accordance with crop cycle to forecast which insect stage is economically important, what the proper time to manage pest is and what type of control is necessary to manage crop pest. The chapter will provide management strategies well suited to pest stage and environment

Prospective, multicentre study of screening, investigation and management of hyponatraemia after subarachnoid haemorrhage in the UK and Ireland

Background: Hyponatraemia often occurs after subarachnoid haemorrhage (SAH). However, its clinical significance and optimal management are uncertain. We audited the screening, investigation and management of hyponatraemia after SAH. Methods: We prospectively identified consecutive patients with spontaneous SAH admitted to neurosurgical units in the United Kingdom or Ireland. We reviewed medical records daily from admission to discharge, 21 days or death and extracted all measurements of serum sodium to identify hyponatraemia (<135 mmol/L). Main outcomes were death/dependency at discharge or 21 days and admission duration >10 days. Associations of hyponatraemia with outcome were assessed using logistic regression with adjustment for predictors of outcome after SAH and admission duration. We assessed hyponatraemia-free survival using multivariable Cox regression. Results: 175/407 (43%) patients admitted to 24 neurosurgical units developed hyponatraemia. 5976 serum sodium measurements were made. Serum osmolality, urine osmolality and urine sodium were measured in 30/166 (18%) hyponatraemic patients with complete data. The most frequently target daily fluid intake was >3 L and this did not differ during hyponatraemic or non-hyponatraemic episodes. 26% (n/N=42/164) patients with hyponatraemia received sodium supplementation. 133 (35%) patients were dead or dependent within the study period and 240 (68%) patients had hospital admission for over 10 days. In the multivariable analyses, hyponatraemia was associated with less dependency (adjusted OR (aOR)=0.35 (95% CI 0.17 to 0.69)) but longer admissions (aOR=3.2 (1.8 to 5.7)). World Federation of Neurosurgical Societies grade I–III, modified Fisher 2–4 and posterior circulation aneurysms were associated with greater hazards of hyponatraemia. Conclusions: In this comprehensive multicentre prospective-adjusted analysis of patients with SAH, hyponatraemia was investigated inconsistently and, for most patients, was not associated with changes in management or clinical outcome. This work establishes a basis for the development of evidence-based SAH-specific guidance for targeted screening, investigation and management of high-risk patients to minimise the impact of hyponatraemia on admission duration and to improve consistency of patient care

Emerging Challenges and Opportunities for Education and Research in Weed Science

In modern agriculture, with more emphasis on high input systems, weed problems are likely to increase and become more complex. With heightened awareness of adverse effects of herbicide residues on human health and environment and the evolution of herbicide-resistant weed biotypes, a significant focus within weed science has now shifted to the development of eco-friendly technologies with reduced reliance on herbicides. Further, with the large-scale adoption of herbicide-resistant crops, and uncertain climatic optima under climate change, the problems for weed science have become multi-faceted. To handle these complex weed problems, a holistic line of action with multi-disciplinary approaches is required, including adjustments to technology, management practices, and legislation. Improved knowledge of weed ecology, biology, genetics, and molecular biology is essential for developing sustainable weed control practices. Additionally, judicious use of advanced technologies, such as site-specific weed management systems and decision support modeling, will play a significant role in reducing costs associated with weed control. Further, effective linkages between farmers and weed researchers will be necessary to facilitate the adoption of technological developments. To meet these challenges, priorities in research need to be determined and the education system for weed science needs to be reoriented. In respect of the latter imperative, closer collaboration between weed scientists and other disciplines can help in defining and solving the complex weed management challenges of the 21st century. This consensus will provide more versatile and diverse approaches to innovative teaching and training practices, which will be needed to prepare future weed science graduates who are capable of handling the anticipated challenges of weed science facing in contemporary agriculture. To build this capacity, mobilizing additional funding for both weed research and weed management education is essential

BIO-ECONOMIC AND QUALITATIVE IMPACT OF REDUCED HERBICIDE USE IN DIRECT SEEDED FINE RICE THROUGH MULTIPURPOSE TREE WATER EXTRACTS

Weed control program should be environmentally benign and cost-effective so that reduced herbicide use can help meet these goals. Field trials were conducted to assess the bio-economic and qualitative impact of reduced doses (25 and 50% of label dose) of a postemergence pyrimidinyloxybenzoic acid herbicide (bispyribac-sodium) applied alone or in combination with multipurpose tree (eucalyptus [ Eucalyptus camaldulensis Dehnh.], mango [ Mangifera indica L.], and mulberry [ Morus alba L.]) water extracts in direct seeded rice ( Oryza sativa L.) fields. The label dose of bispyribac-sodium and penoxsulam along with weed control were included for comparison. Tank mixing of multipurpose tree water extracts with reduced herbicide doses accounted for > 55% suppression in weed density and > 75% in dry weight; they were quite higher than those recorded for the same herbicide doses used alone. A combination of these extracts with 50% reduced dose of bispyribac-sodium improved rice yield and quality attributes similar to the label dose of this herbicide. Despite the higher net benefits associated with label herbicide dose, the maximum marginal rate of return was achieved with a tank mix of 25% label herbicide dose with multipurpose tree water extracts

Weeds of Direct-Seeded Rice in Asia: Problems and Opportunities

Rice production symbolizes the single largest land use for food production on the Earth. The significance of this cereal as a source of energy and income seems overwhelming for millions of people in Asia, representing 90% of global rice production and consumption. Estimates indicate that the burgeoning population will need 25% more rice by 2025 than today's consumption. As the demand for rice is increasing, its production in Asia is threatened by a dwindling natural resource base, socioeconomic limitations, and uncertainty of climatic optima. Transplanting in puddled soil with continuous flooding is a common method of rice crop establishment in Asia. There is a dire need to look for rice production technologies that not only cope with existing limitations of transplanted rice but also are viable, economical, and secure for future food demand.Direct seeding of rice has evolved as a potential alternative to the current detrimental practice of puddling and nursery transplanting. The associated benefits include higher water productivity, less labor and energy inputs, less methane emissions, elimination of time and edaphic conflicts in the rice-wheat cropping system, and early crop maturity. Realization of the yield potential and sustainability of this resource-conserving rice production technique lies primarily in sustainable weed management, since weeds have been recognized as the single largest biological constraint in direct-seeded rice (DSR). Weed competition can reduce DSR yield by 30-80% and even complete crop failure can occur under specific conditions. Understanding the dynamics and outcomes of weed-crop competition in DSR requires sound knowledge of weed ecology, besides production factors that influence both rice and weeds, as well as their association. Successful adoption of direct seeding at the farmers' level in Asia will largely depend on whether farmers can control weeds and prevent shifts in weed populations from intractable weeds to more difficult-to-control weeds as a consequence of direct seeding. Sustainable weed management in DSR comprises all the factors that give DSR a competitive edge over weeds regarding acquisition and use of growth resources. This warrants the need to integrate various cultural practices with weed control measures in order to broaden the spectrum of activity against weed flora. A weed control program focusing entirely on herbicides is no longer ecologically sound, economically feasible, and effective against diverse weed flora and may result in the evolution of herbicide-resistant weed biotypes. Rotation of herbicides with contrasting modes of action in conjunction with cultural measures such as the use of weed-competitive rice cultivars, sowing time, stale seedbed technique, seeding rate, crop row spacing, fertilizer and water inputs and their application method/timing, and manual and mechanical hoeing can prove more effective and need to be optimized keeping in view the type and intensity of weed infestation. This chapter tries to unravel the dynamics of weed-crop competition in DSR. Technological issues, limitations associated with DSR, and opportunities to combat the weed menace are also discussed as a pragmatic approach for sustainable DSR production. A realistic approach to secure yield targets against weed competition will combine the abovementioned strategies and tactics in a coordinated manner. This chapter further suggests the need of multifaceted and interdisciplinary research into ecologically based weed management, as DSR seems inevitable in the near future

ALLELOPATHIC ACTIVITY OF CROP RESIDUE INCORPORATION ALONE OR MIXED AGAINST RICE AND ITS ASSOCIATED GRASS WEED JUNGLE RICE ( Echinochloa colona [L.] Link)

Weed suppression is one of the several benefits achieved by soil incorporation of crop residues and such suppression is believed to be allelopathic in nature. The allelopathic potential of different crop residues: viz. sorghum ( Sorghum bicolor [L.] Moench), sunflower ( Helianthus annuus L.), brassica ( Brassica campestris L.) was evaluated in rice ( Oryza sativa L.) and jungle rice ( Echinochloa colona [L.] Link). Chopped crop residues were soil-incorporated alone and mixed at 6 g kg-1 soil (12 t ha-1) and compared with a control without residues. Soil incorporation of residues substantially delayed germination of jungle rice. The time to start germination, time to 50% emergence, mean emergence time, emergence index, and final germination percentage were all depressed by residue incorporation. Final germination of rice and jungle rice dropped by 11 to 15% and 11 to 27% with residue application alone and by 18 to 22% and 8 to 34% with a combination of crop residues, respectively. Residues were more suppressive to germination dynamics of jungle rice than rice. Crop residues exerted a pronounced negative influence on the shoot (25 to 100% and 14 to 44%) and root lengths (22 to 100% and 10 to 43%) of rice and jungle rice, respectively. Shoot and root dry weight of both rice and jungle rice also decreased significantly. An appreciable quantity of phenolics was recorded in soil amended with sorghum+sunflower+brassica residues. Since soil incorporation of allelopathic crop residues was detrimental to both rice germination and seedling growth, it is suggested that the time of residue application for jungle rice suppression and rice seeding time need to be adjusted so as to minimize rice crop damage

Response of glyphosate-resistant and susceptible biotypes of Echinochloa colona to low doses of glyphosate in different soil moisture conditions

To evaluate the hormetic effect of glyphosate on Echinochloa colona, two pot studies were done in the screenhouse at the Gatton Campus, the University of Queensland, Australia. Glyphosate was sprayed at the 3-4 leaf stage using different doses [(0, 5, 10, 20, 40, 80 and 800 g a.e. ha-1) and (0, 2.5, 5, 10, 20 and 800 g a.e. ha-1)] in the first and second study, respectively. In the second study, two soil moistures (adequately-watered and water-stressed), and two E. colona biotypes, glyphosate-resistant and glyphosate-susceptible, were included. In both studies, plants that were treated with glyphosate at 2.5-40 g ha-1 grew taller and produced more leaves, tillers, inflorescences and seeds than the control treatment. In the first study, 5 g ha-1 glyphosate resulted in the maximum aboveground biomass (increase of 34% to 118%) compared with the control treatment. In the second study, the adequately-watered and glyphosate low dose treatments caused an increase in all the measured growth parameters for both biotypes. For example, total dry biomass was increased by 64% and 54% at 5 g ha-1 in the adequately-watered treatments for the resistant and susceptible biotypes, respectively, compared with the control treatment. All measured traits tended to decrease with increasing water stress and the stimulative growth of low doses of glyphosate could not compensate for the water stress effect. The results of both studies showed a hormetic effect of low doses of glyphosate on E. colona biotypes and such growth stimulation was significant in the range of 5 to 10 g ha-1 glyphosate. Water availability was found to be effective in modulating the stimulatory outcomes of glyphosate-induced hormesis. No significant difference was observed between the resistant and susceptible biotypes for hormesis phenomenon. The study showed the importance of precise herbicide application for suppressing weed growth and herbicide resistance evolution

Weeds in a Changing Climate: Vulnerabilities, Consequences, and Implications for Future Weed Management

Whilst it is agreed that climate change will impact on the long-term interactions between crops and weeds, the results of this impact are far from clear. We suggest that a thorough understanding of weed dominance and weed interactions, depending on crop and weed ecosystems and crop sequences in the ecosystem, will be the key determining factor for successful weed management. Indeed, we claim that recent changes observed throughout the world within the weed spectrum in different cropping systems which were ostensibly related to climate change, warrant a deeper examination of weed vulnerabilities before a full understanding is reached. For example, the uncontrolled establishment of weeds in crops leads to a mixed population, in terms of C3 and C4 pathways, and this poses a considerable level of complexity for weed management. There is a need to include all possible combinations of crops and weeds while studying the impact of climate change on crop-weed competitive interactions, since, from a weed management perspective, C4 weeds would flourish in the increased temperature scenario and pose serious yield penalties. This is particularly alarming as a majority of the most competitive weeds are C4 plants. Although CO2 is considered as a main contributing factor for climate change, a few Australian studies have also predicted differing responses of weed species due to shifts in rainfall patterns. Reduced water availability, due to recurrent and unforeseen droughts, would alter the competitive balance between crops and some weed species, intensifying the crop-weed competition pressure. Although it is recognized that the weed pressure associated with climate change is a significant threat to crop production, either through increased temperatures, rainfall shift, and elevated CO2 levels, the current knowledge of this effect is very sparse. A few models that have attempted to predict these interactions are discussed in this paper, since these models could play an integral role in developing future management programs for future weed threats. This review has presented a comprehensive discussion of the recent research in this area, and has identified key deficiencies which need further research in crop-weed eco-systems to formulate suitable control measures before the real impacts of climate change set in. © 2017 Ramesh, Matloob, Aslam, Florentine and Chauhan

Evaluation and management of acetyl-CoA carboxylase inhibitor resistant littleseed canarygrass (Phalaris minor) in Pakistan

A field survey was conducted for the sampling of Acetyl-CoA carboxylase (ACCase) inhibitor resistance littleseed canarygrass, a major weed of wheat, from Punjab, Pakistan in 2014 for confirmation of resistance. The surveyed regions encompassed four different cropping systems including rice–wheat, maize–wheat, cotton–wheat and mixed cropping. Dose–response assay was conducted for confirmation of resistance. Efficacy of herbicide mixtures including clodinafop–propargyl, metribuzin, pinoxaden and sulfosulfuron at a range of doses was investigated to manage littleseed canarygrass. Results revealed that all populations were resistant to fenoxaprop except PM-BWL-2. The higher level resistance (6.5) was found in populations collected from rice–wheat cropping system. The tested herbicide mixtures at 75% and 100% of the recommended dose of each mixture component provided the effective control of resistant littleseed canarygrass. Mixtures at 50% provided more than 80% control and reduced growth and seed production potential of surviving plants. The confirmation of ACCase inhibitor resistance as the first case of herbicide resistance in Pakistan, leads us to discourage use of ACCase inhibitor herbicides alone. However, herbicide mixtures at 75% and 100% of the recommended dose are suggested to manage this weed for sustainable wheat production in the surveyed cropping systems