Formulation and Evaluation of Controlled-Release Diuron as Pre-Emergence Herbicide

Controlled-release formulations of diuron were prepared in the laboratory using the concept of physical matrix utilizing sodium alginate and kaolin. The release rates of diuron from the formulations were determined by chemical assay and bioassay. In the chemical assay, using high performance chromatography with UV detector, significant differences in release rates between formulations were observed from 3 to 7 days after the granules were placed into distilled water. The formulation having a 1:1 ratio of alginate to kaolin with 1 mm granule size showed the fastest release of diuron while release from the 2 mm granules was slower. The release of diuron from the formulations reached a maximum level of 27% at 30 days after placement in water this same rate of release was maintained up to 60 days after the treatment. Increasing the proportion of kaolin to sodium alginate in the controlled-release formulation reduced the release rate of active agent. Bioassays were conducted in the glasshouse to study the release rates of diuron using Brassica rapa seedlings as bioindicator. The controlled-release formulations showed slower release than the conventional formulation at the beginning of the treatments. At 3 weeks after treatment, there was no significant difference in the mortality of the seedlings between the conventional formulation and controlled-release formulations. However, the controlled-release formulations gave significantly higher seedling mortality compared to the conventional formulation at 16 weeks after the treatments. The same results were observed up to 24 weeks after the treatment when the controlled-release formulations caused between 40 to 70% mortality, while the conventional formulation treatment caused only 6% mortality. Among the controlledrelease formulations, the A K-2 formulation (1:1, alginate to kaolin) was found to give the best control with the highest percentage mortality of the seedlings

Bioefficacy of controlled release formulations of diuron on Brassica rapa

Controlled-release formulations (CRF) of diuron were prepared in laboratory using the concept of physical matrix utilizing sodium alginate and kaolin. The release rates of diuron from the formulations were determined by chemical assay its efficacy on plant was tested on Brassica rapa. In the chemical assay using high performance chromatography with UV detector, significant differences in the release rate between formulations were observed from 3 to 7 days after the granules had been placed in distilled water. The formulation having a 1:1 ratio of alginate to kaolin with 1mm granule size showed the fastest release of diuron, while release from the 2mm granules was slower. Increasing the proportion of kaolin to sodium alginate in the CRF reduced the release rate of active agent. The bioefficacy using Brassica rapa as a bioindicator showed that CRF released slower than the conventional formulation at the beginning of the treatments. In the 3rd week after the treatment (WAT), there was no significant difference in the mortality as compared to the conventional formulation at 16 WAT. The same results were also observed up to 24 WAT, the CRF caused between 40-70% mortality, while the conventional formulation treatment caused only 6% mortality. Among the CRF, the AK-2 with 1:1 ration of alginate:kaolin was found to have given the best result with the highest percentage mortality of the seedlings

Insecticide Use Impacts on Pest Resistance: An Evidence from Diamondback Moth

Diamondback moth (DBM) has been important pest of crucifers since years ago worldwide. The first DBM resistance was reported on dichlorodiphenyltrichloroethane (DDT), from then it has developed resistance to other insecticides. Its ability to build resistance to almost every insecticide introduced is a great concern to the agriculture world, owing mainly to its short life cycle, continuous host availability and its genetic elasticity. Numerous resistance mechanisms displayed by DBM to counterattack effect of insecticides, either behaviorally, physiology or by biochemical. This paper is focused on diamondback moth (DBM) resistance to insecticides, its biochemical mechanism and the potential to become cross resistance to other insecticides. We highlighted the biochemical reactions in DBM resistance and emphasized on enzymes responsible to the resistance. The information on the mechanism could provide valuable information to other researchers in designing a rapid and sensitive biochemical assay in detecting DBM resistance to many insecticides that has yet to be discovered. The potential of DBM to develop cross resistance to other insecticides is also stressed since the issue is always co-related with biochemical resistance mechanisms

Ultra high performance liquid chromatography technique to determine imidacloprid residue in rice using QuEChERS method

Imidacloprid residue analysis in paddy samples was conducted using the simplified and validated QuEChERS preparation method. Samples were extracted with acetonitrile (ACN) and salts anhydrous magnesium sulphate (MgSO4) and sodium chloride (NaCI) while cleaning was by treating with primary secondary amine (PSA). Imidacloprid residue was quantified with Ultra High Performance Liquid Chromatography (UHPLC) using short and narrow C18 column to reduce analysis duration and solvent consumption. The pumps were programmed to mix acetonitrile and water at a ratio of 2:8 to form the mobile phase, with a flow rate of 0.1 mL/min and10 μl injection volumes. Imidacloprid was detected at 270 nm using UV detector. The method was validated in term of linearity, range, limit of detection (LOD), limit of quantification (LOQ), precision (repeatability and intermediate precision), and accuracy (recovery). The LOD was 0.001 mg/L whereas LOQ was 0.003 mg/L. The validated method provides good analytical results wherein the linearity r2 was 0.9996, recoveries 80−120% and RSDs <20%. This method can be implemented in routine laboratories as it yields a higher sample throughput and reduced solvent consumption compared to the traditional Luke method approach

Assessing leaf scale measurement for nitrogen content of oil palm: performance of discriminant analysis and support vector machine classifiers

Nitrogen (N) is a crucial element in sustaining oil palm production. However, assessing N status of tall perennial crops such as oil palm is complex and not as straightforward as assessing annual crops, due to complex N partitioning, age, and larger amounts of respiratory loads. Hence, the objectives of this study were to evaluate the potential of spectral measurements obtained from leaf scale and machine learning approaches as a rapid tool for quantifying oil palm N status. This study involved assessing the performance of discriminant analysis (DA) and Support Vector Machine (SVM) classifiers for discriminating spectral bands sensitive to N sufficiency levels and comparing the predictive accuracy of DA and SVM for classifying N status of immature and mature oil palms. The experiment was conducted on immature Tenera seedlings (13 months old) and mature Tenera palm stands (9 and 12 years old) that were arranged in Randomized Complete Block Design with treatments varied from 0 to 2 kg N. Generally, the discriminant function of both classifiers was age-dependent. A clear trade-off between the classifiers’ number of spectral bands and their accuracies was observed; the DA with a larger number of optimal spectral bands could discriminate N sufficiency levels of all maturity classes with higher accuracies compared to the SVM, yet the latter could produce reasonable accuracies with a lesser number of spectral bands. N status of all maturity classes could be classified satisfactorily with SVM (71–88%) via the satellite-simulated blue and green bands, signifying the possibility to develop spectral index or an N-sensitive sensor for oil palm

Morphological and molecular characterization of fungal pathogen, Magnaphorthe oryzae

Rice is arguably the most crucial food crops supplying quarter of calories intake. Fungal pathogen, Magnaphorthe oryzae promotes blast disease unconditionally to gramineous host including rice species. This disease spurred an outbreaks and constant threat to cereal production. Global rice yield declining almost 10-30% including Malaysia. As Magnaphorthe oryzae and its host is model in disease plant study, the rice blast pathosystem has been the subject of intense interest to overcome the importance of the disease to world agriculture. Therefore, in this study, our prime objective was to isolate samples of Magnaphorthe oryzae from diseased leaf obtained from MARDI Seberang Perai, Penang, Malaysia. Molecular identification was performed by sequences analysis from internal transcribed spacer (ITS) region of nuclear ribosomal RNA genes. Phylogenetic affiliation of the isolated samples were analyzed by comparing the ITS sequences with those deposited in the GenBank database. The sequence of the isolate demonstrated at least 99% nucleotide identity with the corresponding sequence in GenBank for Magnaphorthe oryzae. Morphological observed under microscope demonstrated that the structure of conidia followed similar characteristic as M. oryzae. Finding in this study provide useful information for breeding programs, epidemiology studies and improved disease management

Assessment of Variability and Genetic Diversity Study in an Advanced Segregating Population in Rice with Blast Resistance Genes Introgression

Blast disease caused by a pathogenic fungus, Magnaphorthe oryzae, is the most destructive disease and has resulted in more than 50% of crop losses worldwide, including in Malaysia. The present study was conducted to investigate genetic variability among 36 advanced lines of MR264 × PS2 rice with blast resistance genes introduced at the Faculty of Applied Sciences, Universiti Teknologi MARA, Malaysia. Traits such as days of maturity, plant height, grain width, and seed setting rate exhibited negative skewness in this study, indicating a doubling of gene effects. Seed setting rate and 1000 grain weight showed positive kurtosis, indicating gene interactions. The phenotypic coefficient of variation (PCV) was slightly higher than the genotypic coefficient of variation (GCV) for all traits, indicating that environmental influences affect the expression of these traits. High heritability associated with high genetic advance as a percentage of the mean was observed for filled grains per panicle. In addition, the second-highest value for high heritability and the high genetic advance was observed for the number of tillers. Cluster and principal component analysis revealed that 36 advanced lines were grouped into four clusters based on ten agromorphological traits. Clusters A and C had higher mean values for most of the traits studied than clusters B and D. Desirable recombinants for higher yields with a broad genetic base can be generated by using cross lines from different clusters

Marine-derived fungi: a promising source of halo tolerant biological control agents against plant pathogenic fungi

In this study, twenty marine-derived fungi were evaluated for their antagonistic activities against 10 economically important plant pathogenic fungi and investigated for their halo tolerance on potato dextrose agar (PDA) amended with 1%-25% NaCl. The results of dual culture tests showed that the marine Trichoderma species, T. asperellum and T. harzianum exhibited higher antagonistic effects against all plant pathogens than the other tested fungi, causing percentages of mycelial growth inhibition ranging from 59.31-100%. The results of dilution plate assays revealed that crude extracts of marine-derived fungi in the genera Emericella, Myrothecium, Neocosmospora, Penicillium and Talaromyces displayed great antifungal activity against plant pathogenic fungi at a low concentration of 1 g/L. However, the crude extract of Myrothecium verrucaria showed the best antifungal activity: more than 52% inhibition of five of the tested species of plant pathogenic fungi and complete mycelial growth inhibition of Bipolaris oryzae and Lasiodiplodia theobromae at 1 g/L. All of the tested marine-derived fungi were tolerant to NaCl at concentrations up to 7%. These results revealed marine-derived fungi possess exploitable antagonistic activities against plant pathogenic fungi through antibiosis, competition for nutrients and space and halo tolerance. Moreover, the results from this study showed their potential as novel BCAs for supporting crop production under climatic changes in the future

A comparative study of vegetative and reproductive growth of local weedy and Clearfield® rice varieties in Malaysia

The movement from transplanting to direct seeding has brought weedy rice problems in Malaysia’s rice granary areas. Weedy rice (Oryza spp.) is very difficult to control compared to other weeds due its close genetic relationship to the cultivated rice (Oryza sativa L.), therefore it cannot be controlled with conventional rice herbicides. Recently, a new technology for controlling weedy rice in rice fields which is known as Clearfield® Production System has been introduced by discovering the combination of herbicide imidazolinone and resistant trait containing variety. Two cultivars have been released by Malaysia known as MR 220CL1 and MR 220CL2 which were derived from crosses between CL1770 from Louisiana State University with a Malaysian local rice variety, MR 220. The objective of the study is to understand the growth patterns (vegetative and reproductive) of four different weedy rice morphotypes and two variants of Clearfield® rice in Malaysia. Weedy morphotypes were observed being significantly taller in all growth stages compared to Clearfield®. Tillering abilities of weedy morphotypes were not different from Clearfield® variants except for WR4 at 60 days after seeding (DAS). Flowering and maturity periods observed in weedy morphotypes were ranged widely where all weedy morphotypes flowered 10 to 20 days later than the Clearfield® rice varieties. Understanding all these morphological and physiological characteristics of weedy rice is useful to improve the weedy rice management and good agricultural practices for better control of escaped weedy rice in the Clearfield® planting areas

Status of persistent organic pesticide residue in water and food and their effects on environment and farmers: a comprehensive review in Nigeria

Pesticide helps to enhance agricultural production, however, it significantly affect both socio and environmental entities of a country. In Nigeria, pesticide is widely used, thus its traces have been detected in water, soil and air. Several studies have already indicated that most of the environmental ecology (air, water, and soil) in Nigeria has been contaminated by persistent organic pesticides like organochlorine and organophosphate. Other reasons of high pesticide residues present in Nigeria environment is due to inappropriate dosage applied of pesticides that leaves behind excess. However, its residues are found above safety levels in the air, water, and soil across the nation. Based on previous analysis, it is indicated that 125,000-130,000 metric ton pesticides are being applied annually in Nigeria. Despite banned of some pesticides such as dichlorodiphenyltrichloroethane- and -Hexachlorocyclohexane, they are still being used by farmers in their agricultural production. Many of the Class 1 (high extremely toxic) pesticides are still being used in developing countries like Nigeria. Hence, there is need to sensitize and educate the general public especially the end-users (farmers) particularly on management practices of pesticides. Considering these entire hazardous situations, in this article the history of pesticide used in Nigeria has been reviewed in detail. The article also discussed the effects of pesticide use in Nigerian waters, soil and on crops. The risk of residual pesticide on agricultural workers, pesticide residue risk preventive measures by the Federal Government of Nigeria, banned and restricted pesticides in Nigeria, Nigerian Government and its efforts to eliminate persistent organic pesticides in use are also reviewed in details