Dzolkhifli Omar

Green nanoemulsion-laden glyphosate isopropylamine formulation in suppressing creeping foxglove (A. gangetica), slender button weed (D. ocimifolia) and buffalo grass (P. conjugatum).

BACKGROUND 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. RESULTS The nanoemulsion formulations displayed a significantly lower spray deposition on creeping foxglove (2.9-3.5 ng cm(-2) ), slender button weed (2.6-2.9 ng cm(-2) ) and buffalo grass (1.8-2.4 ng cm(-2) ) than Roundup(®) (3.7-5.1 ng cm(-2) ). The visible injury rates of weeds treated with the nanoemulsion formulations were statistically equivalent to those relating to Roundup(®) at 14 days after treatment, with a control range of 86.67-96.67%. CONCLUSION It was hypothesised that the significant difference in spray deposition with equal injury rates can be attributed to enhanced bioactivity of the nanoemulsion formulations. This initial discovery could be the platform for developing better penetration of agrochemical formulations in the future.

Biotype and insecticide resistance status of Bemisia tabaci populations from Peninsular Malaysia

Bemisia tabaci, a resistance‐prone insect pest, is a cryptic species complex with important invasive biotypes such as B and Q. The biotype and resistance statuses of this pest in Malaysia remain unclear. This study assessed the biotype and resistance status of a number of contemporary populations of B. tabaci based on the mtCO1 marker and the dose‐response method, respectively. The Pahang (PHG) population was labelled as the Q biotype, while the remainder of the populations belonged to the Asia 1 biotype. A very low level of resistance for profenofos, cypermethrin, and imidacloprid was detected for all populations [resistance factor (RF) < 10]. Resistance to diafenthiuron ranged from very low to very high (RF > 100). All populations showed a very low level of resistance against pymetrozine except Q‐type PHG population, which exhibited a very high level of resistance. For most insecticides, the highest level of resistance was detected in the PHG population. The implications of these findings for better management of this noxious pest are discussed.

Exploring Cancer Development in Adulthood: Cholinesterase Depression and Genotoxic Effect From Chronic Exposure to Organophosphate Pesticides Among Rural Farm Children

ABSTRACT 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 childrens 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.

FIRST REPORT OF BEMISIA TABACI (HEMIPTERA: ALEYRODIDAE) BIOTYPE Q IN MALAYSIA

This article was originally published on May 28, 2013, and has been corrected (June 13, 2013). View this article in BioOne

A comparison of biomarker responses in juvenile diploid and triploid African catfish, Clarias gariepinus, exposed to the pesticide butachlor

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.

Characterization of Risk Factors for DNA Damage Among Paddy Farm Worker Exposed to Mixtures of Organophosphates

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.

Fate of napropamide herbicide in selected Malaysian soils.

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.

Bioactivity Effect of Piper nigrum L. and Jatropha curcas L. Extracts Against Corcyra cephalonica (Stainton)

Petroleum ether extract of black pepper (Piper nigrum) and physic nut (Jatropha curcas) were shown to have insecticidal efficacies against rice moth (Corcyra cephalonic) (Stainton). The C. cephalonica larvae (16 day old) were shown to have similarities susceptibility to petroleum ether extract of P. nigrum and J. curcas with LC50 values of 12.52 and 13.22 μL/mL, respectively. In a bioassay using no-choice tests, the parameters used to evaluate antifeedant activity were Relative Growth Rate (RGR); Relative Consumption Rate (RCR), efficiency on conversion of ingested food (ECI) and Feeding Deterrence Indices (FDI). Both extracts showed high bioactivity at all doses against C. cephalonica larvae and antifeedant action was increased with increasing plant extract concentrations. The petroleum ether extract of P. nigrum and J. curcas showed strong inhibition on egg hatchability and adult emergence of C. cephalonica at the lowest concentration. Based on the results of this study petroleum ether extracts of P. nigrum and J. curcas could be used in IPM program for rice moth.

Allelopathic effect of methanol extracts from Tinospora tuberculata on selected crops and rice weeds

Herbicidal potential of aerial parts of Tinospora tuberculata on germination and seedling growth of seven test plant species, namely rice (Oryza sativa L.); two rice weeds, barnyardgrass (Echinochloa crus-galli L.) and weedy rice (O. sativa f. spontanea); and four vegetable crops, lettuce (Lactuca sativa L.), tomato (Solanum lycopersicum L.), carrot (Daucus carota L.), and cucumber (Cucumis sativus L.) were evaluated. Six concentrations of methanol extract (3.12, 6.25, 12.5, 25, 50, and 100 g L−1) were compared with the control (distilled water). The rate of seed germination and the radicle and hypocotyl length of 7-day-old test plant seedlings were reduced as the concentration of extracts increased compared to the control. Generally, the degree of toxicity of extracts derived from the leaves was more than the extracts derived from the stem. Cluster analysis and the concentrations required for 50% inhibition (defined as EC50) of all parameters showed that radicle growth was more suppressed than germination and hypocotyl growth. Lettuce and carrot were observed as the most sensitive plants while rice showed the highest tolerance to both extracts. Moreover, the dicot target plants were affected more severely than the monocots when treated with leaf extract. The chemical composition of the T. tuberculata methanolic extracts was analyzed by a GC–MS system. A total of 92 and 22 constituents (not previously identified) were found in the leaves and stem, respectively. The results showed that 17 of the 92 components in the leaves, as compared to 4 of 22 compounds in the stem, are known as toxic compounds. These results suggest that T. tuberculata contains a significant source of plant growth inhibitors with potential for the development of future natural herbicide.

Sorption and Desorption of Napropamide in Sandy Soil Amended with Chicken Dung and Palm Oil Mill Effluent

Beach Ridges Interspersed with Swales (BRIS) is a sandy soil and in Malaysia it is found exclusively in the east coast of Peninsular Malaysia. It is a marginal soil because of its low nutrient and water-holding capacity. However, with proper management and organic matter amendments some areas with BRIS soil are cultivated. Napropamide is a selective herbicide widely used to control weeds in BRIS soil. No previous studies have been reported on the effects of organic matter amendments on napropamide sorption in BRIS soil. This study was conducted to determine sorption and desorption of napropamide in BRIS soil amended with chicken dung (CD) and palm oil mill effluent (POME) at 0, 20, 40, and 80 Mg ha−1. Potential interaction of dissolved organic carbon (DOC) with napropamide and their competition for sorption sites were also determined. Sorption isotherm data were fitted to the log-transformed Freundlichs equation. Sorption of napropamide was higher in soils amended with CD and POME as compared to non-amended soil. At the same rates of application, sorption was higher in soil amended with CD than POME. The Freundlichs coefficient (Kf) values were 0.22, 3.96, and 41.6 for nonamended soil, soil amended with 80 Mg ha−1 POME, and soil amended with 80 Mg ha−1 CD, respectively. Desorption of napropamide showed positive hysteresis and the hysteresis were greater with higher rates of CD and POME. There was no association between napropamide and DOC extracted from BRIS soil amended with either CD or POME and also there were no competitions between napropamide and DOC extracted from either CD or POME for sorption sites of the soil samples.