This study investigates pest management practices among lowland farmers on growing
leafy and fruit vegetables, particularly focusing on the pesticide usage in controlling pest. In
Malaysia, vegetable productions in lowland areas are to some extent really important as in the
highland areas due to the wide marketing channel, from local till traded across border. Yet, the
ignorance of vegetables safety regarding the appropriate of pesticide usage by farmers was
undeniable, as the market demands only products with good extrinsic quality. Thus a survey
was conducted among of 85 of lowland vegetable farmers to get information on their pest
management practices in farms. Result showed that the pesticide application by farmers on
vegetables crops still indicated a calendar spraying practices. In most cases, farmers tend to
harvest the vegetable products shortly after a few days of last pesticide spraying. In order to
enhance the food safety control starting from the primary production, extensive monitoring of
the current pesticide usage by farmers in vegetable productions is vital to provide an updated
data on the food safety risk regarding to the pesticide residues. Therefore, the thrust of this
paper was to get a better understanding on the level of safe pesticide usage among vegetables
farmers especially in areas of growing vegetables productions.
Resistance to the bacteria-derived insecticides spinosad (Conserve), abamectin (Vertimec), Bacillus thuringiensis var kurstaki (Btk) (Dipel), B thuringiensis var aizawai (Bta) (Xentari), B thuringiensis crystal endotoxins Cry1Ac and Cry1Ca, and to the synthetic insecticide fipronil was estimated in a freshly-collected field population (CH1 strain) of Plutella xylostella (L) from the Cameron Highlands, Malaysia. Laboratory bioassays at G1 indicated significant levels of resistance to spinosad, abamectin, Cry1Ac, Btk, Cry1Ca, fipronil and Bta when compared with a laboratory insecticide-susceptible population. Logit regression analysis of F1 reciprocal crosses indicated that resistance to spinosad in the CH1 population was inherited as a co-dominant trait. At the highest dose of spinosad tested, resistance was close to completely recessive, while at the lowest dose it was incompletely dominant. A direct test of monogenic inheritance based on a back-cross of F1 progeny with CH1 suggested that resistance to spinosad was controlled by a single locus.
The tobacco whitefly Bemisia tabaci (Gennadius) (Hemiptera: Aleyrodidae) is a cryptic species complex with members capable of inducing huge economic losses. Precise identification of members of this complex proves essential in managing existing populations and preventing new incursions. Despite records of serious outbreaks of this pest in Malaysia little is known about species status of B. tabaci in this region. To address this, a comprehensive sampling of B. tabaci from different host plants was conducted in 10 states of Malaysia from 2010 to 2012. Members of the complex were identified by sequencing partial mitochondrial cytochrome oxidase subunit I (mtCOI) gene and constructing a Bayesian phylogenetic tree. Seven putative species were identified including Asia I, Mediterranean (MED), China 1, China 2, Asia II 6, Asia II 7, and Asia II 10. The most important finding of the study is the identification of the invasive MED species from locations without previous records of this species. All putative species except Asia I and MED are recorded from Malaysia for the first time. This study provided the first introductory map of B. tabaci species composition in Malaysia and emphasizes the urgent need for further studies to assess the status of MED invasion in this country.
A study was carried out to determine the effects of paraquat, pretilachlor and 2, 4-D on growth and nitrogen fixing activity of Stenotrophomonas maltophilia (Sb16) and pH of Jensen's N-free medium. The growth of Sb16 and pH of medium were significantly reduced with full (X) and double (2X) doses of tested herbicides, but nitrogen fixing activity was decreased by 2X doses. The nitrogenase activity had the highest value in samples treated with 1/2X of 2, 4-D on fifth incubation day, but 2X of 2, 4-D had the most adverse effect. An inhibition in the growth and nitrogenase activity was recovered on the last days of incubation.
Drawbacks associated with the use of chemical fungicides to control plant pathogenic fungi such as Botrytis cinerea stimulate the need for alternatives. Therefore, the present study was carried out to determine the antifungal potentials of Moringa oleifera extracts against B. cinerea. Phytochemical analysis using qualitative chemical tests revealed the presence of huge amount of crucial phytochemicals compounds like phenolic compounds, alkaloids and saponins in the M. oleifera leaf extract. Antifungal bioassay of the crude extracts indicated better mycelial growth inhibition by methanol leaf extract (99%). The minimum inhibitory concentration (MIC) was 5 mg/ml with 100% spore germination inhibition and minimum fungicidal concentration (MFC) was 10 mg/ml with 98.10% mycelial growth inhibition using broth micro dilution and poisoned food techniques. Gas chromatography-mass spectrometry (GC-MS) analysis led to the identification of 67 volatile chemical compounds in the leaf extract with 6-decenoic acid (Z)- (19.87%) was the predominant compound. Further chemical elucidation of the crude extracts performed by liquid chromatography with tandem mass spectrometry (LC-MS/MS) showed the presence of non-volatile chemical compounds, mostly flavones, flavonoids and phenolic acids (i.e. quercetin and kaempferol). Scanning electron microscopy and transmission electron microscopy analysis showed positive effect of M. oleifera leaf extract on the treated conidia and mycelium of B. cinerea. Findings revealed that irreversible surface and ultra-structural changes with severe detrimental effects on conidia and mycelium morphology compared to control treatment. Overall findings suggested that M. oleifera leaf extract is a promising candidate for biological control of fungal pathogens, thus limiting overdependence on chemical fungicides.
Water hyacinth (Eichhornia crassipes) is a free-floating aquatic plant and is also widely cultivated as an aquatic ornamental plant in Malaysia. In June 2018, a severe foliar disease with typical leaf blight symptoms were observed on leaves of water hyacinth plants (approximately 50%) in waterways adjacent to two rice fields located at Tanjung Karang and Sungai Besar, Selangor province, Malaysia. Symptoms appeared irregular necrotic lesions with concentric rings, later lesions expanded to entire leaves and became blighted. Twenty symptomatic leaves were collected from two sampling locations. Symptomatic leaf tissue was cut into small pieces (5 × 5 mm), surface sterilized with 0.5% sodium hypochlorite (NaOCl) for 2 min, rinsed three times with sterile distilled water, plated on potato dextrose agar (PDA), and incubated at 25 °C with a 12-h light/dark cycle for 7 days. Twenty single-spore isolates were recovered from sampled leaves, all isolates exhibited Paramyrothecium-like morphology and two representative isolates, PR1 and PR2 were used for further studies. Fungal colonies were initially white aerial mycelia with sporodochia bearing olivaceous green conidial masses formed on PDA after 5 days of incubation. Conidiogenous cells were phialidic, hyaline, smooth, straight to slightly curved, 13 to 20 × 1.0 to 1.8 μm and setae were absent. Conidia were aseptate, hyaline to pale green, smooth, cylindrical to ellipsoidal with rounded ends, and measured 5.8 to 8.0 μm × 1.8 to 2.2 μm (n=50). These morphological characteristics were consistent with the description of Paramyrothecium roridum (Tode) L. Lombard & Crous (Lombard et al. 2016). Total genomic DNA of the isolates was extracted from fresh mycelium using DNeasy Plant Mini kit (Qiagen, USA). The internal transcribed spacer (ITS) and calmodulin (cmdA) gene regions were amplified using the ITS5/ITS4 (White et al.1990) and CAL-228F/CAL2Rd primer sets (Carbone and Kohn 1999; Groenewald et al., 2013), respectively. BLASTn analysis showed that the ITS and cmdA sequences of the isolates were 100% identity with Paramyrothecium roridum ex-epitype strain CBS 357.89 (GenBank accession nos. KU846300 and KU846270), respectively. The resulting sequences were deposited in GenBank (ITS: Accession nos. MW850370, MW850371; cmdA Accession nos. MW854363, MW854364). Pathogenicity tests of the two isolates were performed by spray inoculation on healthy leaves of each five potted water hyacinth plants using a 3-ml conidial suspension (1 × 106 conidia/ml) produced on 7-day-old PDA cultures incubated at 25 °C with a 12-h light/dark cycle. Five potted water hyacinth plants inoculated with sterile water served as controls. Inoculated plants were covered with plastic bags for 48 h to maintain high humidity and kept in a growth chamber for 2 weeks at 25 ± 1°C, 95% relative humidity and a 12-h light/dark period. The experiment was repeated twice. Eight days post-inoculation, symptoms on inoculated leaves developed necrotic brown lesions similar to those observed in the field, while control leaves remained asymptomatic. After 2 weeks of inoculation, lesions enlarged into severe blighting until all leaves died. Paramyrothecium roridum was re-isolated from randomly selected symptomatic tissues and verified by morphology and sequencing of ITS (MZ675387, MZ706462) and cmdA (MZ686706, MZ712041) loci, confirming Koch's postulates. The fungus was not re-isolated from non-inoculated control plants. Pa. roridum is distributed on a wide range of plants (Farr and Rossman 2021) and has been reported to cause leaf spot of water hyacinth in Nigeria (Okunowo et al. 2013) and Sri Lanka (Adikaram and Yakandawala 2020). To our knowledge, this is the first report of Pa. roridum causing leaf blight of water hyacinth in Malaysia. This disease is an emerging threat to water hyacinth and it reduces the leaf quality, therefore, appropriate management should be developed to control this disease.
Bacterial leaf blight (BLB) and sheath brown rot (SBR), caused by Xanthomonas oryzae pv. oryzae (Xoo) and Pseudomonas fuscovaginae, respectively, are bacterial diseases that lead to substantial yield losses in rice. Natural plant-based products represent a sustainable alternative to combat bacterial diseases due to their biodegradability and overall safety. However efficient ways of delivering them are crucial to their success. In an attempt to maximize the antibacterial properties of botanical bactericides for the control of these pathogens, this study evaluated the efficiency of different emulsion formulations of Piper sarmentosum extracts. The emulsion formulations were demonstrated to be effective in controlling BLB and SBR of rice in in vitro plate assays and in planta under glasshouse conditions. The observed in vitro inhibition of the bacterial pathogens and significant disease suppression in planta indicate that these plant extract formulations represent promising alternatives to be adopted in management strategies for controlling rice diseases.
Development of mycoinsecticides with Cordyceps fumosorosea as an active ingredient is established as an alternate way to control the Metisa plana population while reducing chemical insecticide dependence. Three mycoinsecticide formulations (SS6, SS7, and SS8) with dispersing and wetting agents were developed as wettable powder formulations in this trial. SS8 demonstrated the best wettability, suspensibility, and dispersibility with viability at 107 (CFU)/mL even after three months of storage. However, SS7 developed with C. fumosorosea as an active ingredient was found to effectively reduce the bagworm population by more than 95%. The application of all mycoinsecticide formulations in the infested oil palm area was able to reduce the M. plana population by more than 95%, 30 DAT. The formulations also show no significant increase in mortality of the oil palm pollinator, Elaeidobius kamerunicus. This finding indicates that the C. fumosorosea tested has potential for managing bagworms without harming pollinators on oil palm plantations.
Herbicide resistance is a worldwide problem in weed control. This prompts researchers to look for new modes of action to slow down the evolution of herbicide-resistant weeds. This research aims to determine the herbicidal action of thiazolo[3,2-a]pyrimidines derivatives, which are well known as antihypertensive drugs. The phytotoxic effects of ten compounds were investigated using leaf disc discoloration test and seed germination bioassay. At concentrations of 125 to 250 mg/L, the 5-(3-Fluoro-phenyl)-7-methyl-5H-thiazolo[3,2-a]pyrimidine-6-carboxylic acid ethyl ester (c) was highly active against Oldenlandia verticillata and Eleusine indica. At application rates of 1.25 to 2.5 kg ai/ha, formulated c demonstrated selective post-emergence and pre-emergence herbicidal activity against O. verticillata, E. indica and Cyperus iria. In the crop tolerance test, formulated c outperformed the commercial herbicide diuron, with aerobic Oryza sativa being the most tolerant, followed by Zea mays, and Brassica rapa. The addition of calcium chloride partially nullified compound c's inhibitory effects on weed shoot growth, indicating that it has potential as a calcium channel blocker. Compound c acted by triggering electrolyte leakage without affecting photosystem II. These findings imply that c could be explored further as a template for developing new herbicides with novel modes of action.
This is a cross-sectional study conducted among paddy farmers to characterize potential risk factors that influence levels of DNA damage from exposure to mixtures of organophosphates. Comet assay was used to determine the level of DNA damage by measuring the comet tail length from the exfoliated buccal mucosa. The result suggests that farmers who chronically exposure to a mixture of organophosphates has at least 2-fold significant increase of DNA damage as compared with control group. Factor analysis and linear regression both suggest that DNA damage reported by farmers may influence individual, occupational, and residential factors and are reported as significant predictor factors, whereas this effect is mainly caused by individual factors among the control group. The findings of the present study suggest that either farmer or control group bear certain extent of genotoxic burden contributed by different risk factors.
Children are the vulnerable group in the agricultural community due to their early exposure to pesticides through the dynamic interplay between genetic predisposition, environment, and host-related factors. This study aims to identify the possible association between the depression in blood cholinesterase level and genotoxic effect among farm children. The results of micronuclei assay and comet assay showed that the reduced blood cholinesterase level from organophosphate pesticide exposure is significantly associated with an increase in chromosome breakage and DNA strand breaks. These genotoxicity end points suggest that farm children's cells experience early DNA damage that may lead to uncontrolled cell proliferation during their adulthood. Thus, farm children who grow up near pesticide-treated farmland have a higher probability of developing cancer than children with minimal or zero exposure to pesticides.
This study was carried out to determine the sorption-desorption, degradation and leaching of napropamide in selected Malaysian soils. The sorption capacities of the selected Malaysian soils for napropamide were the following in descending order: Linau > Teringkap > Gunung Berinchang > Jambu > Rudua > Baging soil. The results indicate that napropamide degradation decreased with increasing soil sorption capacity. Napropamide was leached out earlier in the Baging soil than the other soils. Overall, the application of napropamide in the selected Malaysian soils would not pose a threat to the environment except in soil with low organic matter and clay content and high hydraulic conductivity, such as the Baging soil.
The downward movement of carbofuran in two Malaysian soil types was studied using soil columns. The columns were filled with disturbed and undisturbed soils of either the Bagan Datoh soil (clay) or the Labu soil (sandy clay). The average total percentage of carbofuran in the leachate of the undisturbed Labu soil after 14 days of watering (80.8%) was approximately similar to that of the total amount from the disturbed soil (81.4%). However, carbofuran leaching was observed in the disturbed soil after the fourth day of watering whereas for the undisturbed soil, leaching occurred after the first watering. A similar trend was observed in the Bagan Datoh soil where the residue of carbofuran was detected after the first day of watering in the undisturbed soil column but only at the eighth day of watering in the disturbed soil column. The total percentage carbofuran in the leachate of disturbed and undisturbed soil columns from Bagan Datoh after 14 days of watering was 3.6% and 41.7%, respectively. The study showed that less leaching occurred in soil columns with high organic content such as the Bagan Datoh soil and especially so in disturbed soils where the organic matter was homogeneously mixed in all layers.
The present study revealed the optimization of nanoemulsion containing palm oil derivatives and Parthenium hysterophorus L. crude extract (PHCE) as pre-emergence herbicide formulation against Diodia ocimifolia. The nanoemulsion formulation was prepared by high energy emulsification method, and it was optimized by mixture experimental design (MED). From the optimization process, analysis of variance (ANOVA) showed a fit quadratic polynomial model with an optimal formulation composition containing 30.91% of palm kernel oil ester (PKOE), 28.48% of mixed surfactants (Tensiofix and Tween 80, 8:2), 28.32% of water and 12.29% of PHCE. The reading of both experimental and predicted particle size in the verification experiment were acceptable with a residual standard error (RSE) was less than 2%. Under the optimal condition, the smallest particle size obtained was 140.10 nm, and the particle was shown by morphology analysis to be spherical and demonstrated good stability (no phase separation) under centrifugation and different storage conditions (25 ± 5°C and 45°C). Nanoemulsion stored for 60 days exhibits monodisperse emulsion with a slight increase of particle size. The increase in particle size over time might have contributed by Ostwald ripening phenomenon which is shown by a linear graph from Ostwald ripening rate analysis. In the in vitro germination test, P. hysterophorus nanoemulsion (PHNE) was shown to cause total inhibition of D. ocimifolia seed at lower concentration (5 g L-1) as compared to PHCE (10 g L-1). The finding of the research could potentially serve as a platform for the development of palm oil based formulation containing plant crude extract for green weed management.
Metarhizium anisopliae (Metchnikoff) Sorokin, a pathogenic fungus to insects, infects the subterranean termite, Coptotermes curvignathus Holmgren, a devastating pest of plantation trees in the tropics. Electron microscopy and proteomics were used to investigate the infection and developmental process of M. anisopliae in C. curvignathus. Fungal infection was initiated by germ tube penetration through the host's cuticle as observed at 6 h post-inoculation (PI), after which it elongated into the host's integumental tissue. The colonization process continued as seen from dissemination of blastospores in the hemocoel at 96 h PI. At this time point, the emergent mycelia had mummified the host and forty-eight hours later, new conidia were dispersed on the termites' body surface. Meanwhile, hyphal bodies were observed in abundance in the intercellular space in the host's body. The proteomes of the pathogen and host were isolated separately using inoculated termite samples withdrawn at each PI-time point and analyzed in two-dimensional electrophoresis (2-DE) gels. Proteins expressed in termites showed evidence of being related to cell regulation and the immune response, while those expressed in M. anisopliae, to transportation and fungal virulence. This study provides new information on the interaction between termites and its entomopathogen, with potential utilization for developing future biopesticide to control the termite population.
Pesticides are developed with carriers to improve their physicochemical properties and, accordingly, the bioefficacy of the applied formulation. For foliar-applied herbicide, generally less than 0.1% of the active ingredient reaching the target site could reduce pesticide performance. Recently, a carrier of nanoemulsion consisting of oil, surfactant and water, with a particle size of less than 200 nm, has been shown to enhance drug permeability for skin penetration in pharmaceutical delivery systems. In the present work, the aim was to formulate a water-soluble herbicide, glyphosate isopropylamine (IPA), using a green nanoemulsion system for a biological activity study against the weeds creeping foxglove, slender button weed and buffalo grass.
Influence of waterborne butachlor (BUC), a commonly used pesticide, on morphometric, biochemical, and molecular biomarkers was evaluated in juvenile, full sibling, diploid and triploid African catfish (Clarias gariepinus). Fish were exposed for 21 days to one of three concentrations of BUC [mean measured µg/L: 22, 44 or 60]. Unexposed (control) triploids were heavier and longer and had higher visceral-somatic index (VSI) than diploids. Also, they had lighter liver weight (HSI) and showed lower transcript levels of brain gonadotropin-releasing hormone (GnRH), aromatase (cyp191b) and fushi tarazu-factor (ftz-f1), and plasma testosterone levels than diploids. Butachlor treatments had no effects, in either diploid or triploid fish, on VSI, HSI, weight or length changes, condition factor (CF), levels of plasma testosterone, 17-β estradiol (E2), cortisol, cholesterol, or mRNA levels of brain tryptophan hydroxylase (tph2), forkhead box L2 (foxl2), and 11 β-hydroxysteroid dehydrogenase type 2 (11β-hsd2). Expressions of cyp191b and ftz-f1 in triploids were upregulated by the two highest concentrations of BUC. In diploid fish, however, exposures to all BUC concentrations decreased GnRH transcription and the medium BUC concentration decreased ftz-f1 transcription. Substantial differences between ploidies in basal biomarker responses are consistent with the reported impaired reproductive axis in triploid C. gariepinus. Furthermore, the present study showed the low impact of short term exposure to BUC on reproductive axis in C. gariepinus.
Metisa plana (Walker) is a leaf defoliating pest that is able to cause staggering economical losses to oil palm cultivation. Considering the economic devastation that the pest could bring, an early warning system to predict its outbreak is crucial. The state of art of satellite technologies are now able to derive environmental factors such as relative humidity (RH) that may influence pest population's fluctuations in rapid, harmless, and cost-effective manners. This study examined the relationship between the presence of Metisa plana at different time lags and remote sensing (RS) derived RH by using statistical and machine learning approaches. Metisa plana census data of cumulated larvae instar 1, 2, 3, and 4 were collected biweekly in 2014 and 2015 in an oil palm plantation in Muadzam Shah, Pahang, Malaysia. Relative humidity values derived from Moderate Resolution Imaging Spectroradiometer (MODIS) satellite images were apportioned to 6 time lags; 1 week (T1), 2 weeks (T2), 3 week (T3), 4 weeks (T4), 5 week (T5) and 6 weeks (T6) and paired with the respective census data. Pearson's correlation was carried out to analyse the relationship between Metisa plana and RH at different time lags. Regression analyses and artificial neural network (ANN) were also conducted to develop the best prediction model of Metisa plana's outbreak. The results showed relatively high correlations, positively or negatively, between the presences of Metisa plana with RH ranging from 0.46 to 0.99. ANN was found to be superior to regression models with the adjusted coefficient of determination (R2) between the actual and predicted Metisa plana values ranging from 0.06 to 0.57 versus 0.00 to 0.05. The analysis on the best time lags illustrated that the multiple time lags were more influential on the Metisa plana population than the individual time lags. The best Metisa plana prediction model was derived from T1, T2 and T3 multiple time lags modelled using the ANN algorithm with R2 value of 0.57, errors below 1.14 and accuracies above 93%. Based on the result of this study, the elucidation of Metisa plana's landscape ecology was possible with the utilization of RH as the predictor variable in consideration of the time lag effects of RH on the pest's population.
This study evaluates the efficacy of palm oil-based nanoemulsion insecticides in thermal fogging applications against adult Ae. aegypti. The nanoemulsion formulations contained a palm oil methyl ester solvent, water, a non-ionic surfactant, and active ingredient deltamethrin, with nanoemulsion droplet diameters ranging from 362 to 382 nm. Knockdown and mortality rates of caged mosquitoes were measured at various distances up to 18 m from the spray nozzle. After 15 min of insecticide exposure, nanoemulsion insecticides achieved a knockdown rate of >97% at a spraying distance of 4 m, and the knockdown effect increased substantially with exposure time. At an 18 m spraying distance, the best nanoemulsion formulation, NanoEW8, achieved a high mosquito mortality rate of more than 80%, whereas the non-nanoemulsion and the commercial product reached only 14 and 8 m distances, respectively, for comparable mortality. The artificial neural network (ANN) was used to predict the mosquito knockdown distribution over the spraying distances and time intervals. The models predicted that NanoEW8 can still cause knockdown at a maximum distance of 61.5 m from the discharge point 60 min after spraying. The results established that Ae. aegypti was susceptible to the newly developed palm oil-based nanoemulsion insecticide, indicating a high potential for mosquito control.