Kerosakan lif penumpang yang sering berlaku di rumah pangsa kos rendah merupakan salah satu isu utama di JKKP Wilayah Persekutuan. Statistik menunjukkan bilangan rumah pangsa paling tinggi terletak di Wilayah Persekutuan. Ini bermakna bilangan lif di rumah pangsa kos rendah adalah tertinggi di Wilayah Persekutuan berbanding negeri – negeri lain. Satu kajian ‘Field Labarotary’ telah dijalankan diperingkat JKKP Wilayah Persekutuan bagi mencari punca permasalahan ini dan seterusnya mencadangkan penambahbaikan berdasarkan kepada permasalahan yang telah dikenalpasti. Kajian ini merangkumi beberapa tindakan seperti mengadakan dialog dengan wakil penghuni rumah pangsa kos rendah di sekitar Wilayah Persekutuan bagi mengenalpasti masalah-masalah yang dihadapi oleh penghuni runmah pangsa kos rendah, penyediaan senarai semak pemeriksaan lif bagi mengenalpasti masalah – masalah teknikal, mengadakan perjumpaan dengan wakil syarikat – syarikat lif bagi mendapatkan data – data yang diperlukan daripada firma – firma kompetan lif dan pengurusan lif di rumah pangsa kos rendah dan menjalankan operasi khas pemeriksaan lif di 409 unit lif yang beroperasi di rumah pangsa kos rendah bagi mengenalpasti kelemahan – kelemahan pada lif yang sedang beroperasi. Kajian telah mengenalpasti beberapa faktor penyumbang kepada isu keselamatan lif di rumah pangsa kos rendah di antaranya bilangan orang kompetan yang diiktiraf oleh Jabatan Keselamatan dan Kesihatan Pekerjaan di dapati tidak mencukupi untuk menjalankan pemeriksaan yang diperlukan ke atas kesemua lif secara komprehensif, kegagalan syarikat lif menunaikan tanggungjawab menjalankan pemeriksaan yang diwajibkan ke atas lif yang berkait rapat dengan isu bilangan orang kompetan yang ada pada setiap firma kompetan, kegagalan pemilik atau badan pengurusan bersama memastikan lif di periksa pada jangkamasa yang ditetapkan serta memastikan lif sentiasa mempunyai sijil kelayakan yang sah, kegagalan JKKP sendiri mengambil tindakan yang diperuntukan oleh Akta dan Peraturan ke atas perlanggaran peruntukan oleh firma kompetan atau pemilik bangunan, ketiadaan kerjasama di antara agensi – agensi kerajaan yang terlibat di dalam rekabentuk dan penyenggaraan lif di rumah pangsa kos rendah dan paling utama ialah isu vandalime yang berkaitan dengan sikap penduduk dan pengguna lif di rumah pangsa kos rendah yang tidak bertanggungjawab merosakan lif.
A comparison of dissipation of chlorothalonil, chlorpyrifos, and profenofos in a Malaysian agricultural soil between the field experiment and simulation by the PERSIST model was studied. A plot of sweet pea (Pisum sativum) from a farm in the Cameron Highlands was selected for the field experiment. The plot was treated with chlorothalonil, chlorpyrifos, and profenofos. Core soil collection was conducted according to the sampling schedule. Residues of the three pesticides were analyzed in the laboratory. Simulations of the three pesticides' persistency were also conducted using a computer-run software PERSIST. Generally, predicted data obtained using PERSIST were found to be high for the three pesticides except for one field measurement of chlorpyrifos. The predicted data for profenofos, which is the most mobile of the three pesticides tested, was not well matched with the observed data compared to chlorothalonil and chlorpyrifos.
The resistance profiles of 22 field-collected populations of the German cockroach, Blattella germanica (L.) (Dictyoptera: Blattellidae), from various localities in Singapore were determined by topical bioassay against novel and conventional insecticides from six classes: (1) pyrethroid (beta-cyfluthrin, deltamethrin), (2) carbamate (propoxur), (3) organophosphate (chlorpyrifos), (4) phenyl pyrazole (fipronil), (5) neonicotinoid (imidacloprid), and (6) oxadiazine (indoxacarb). Compared with a laboratory susceptible strain, resistance levels ranged from 3.0 to 468.0x for the pyrethroids, from 3.9 to 21.5x for the carbamate, from 1.5 to 22.8X for the organophosphate, from 1.0 to 10.0X for phenyl pyrazole, and were absent or low for the neonicotinoid (0.8-3.8x) and the oxadiazine (1.4-5.3x). One strain demonstrated broad-spectrum resistance to most of the insecticides. Synergism studies using piperonyl butoxide (PBO) and S,S,S-tributylphosphorotrithioate (DEF) in combination with a discriminating dose (LD99) of selected insecticides were conducted to test for possible resistance mechanisms. Resistance to pyrethroid was reduced with PBO and DEF, suggesting the involvement of P450 monooxygenase and esterases in conferring resistance. Propoxur resistance also was suppressed with PBO and DEF, and coadministration of both synergists resulted in complete negation of the resistance, indicating the involvement of both P450 monooxygenase and esterase. In six B. germanica field strains evaluated, esterases were found to play a role in chlorpyrifos resistance, whereas the P450 monoxygenase involvement was registered in three strains. Additional resistance mechanisms such as kdr-type and Rdl mutation contributing toward pyrethroid and fipronil resistance, respectively, also may be involved in some strains in which the resistance levels were not affected by the synergists. We conclude that insecticide resistance is prevalent in field German cockroach populations in Singapore.
Aedes albopictus larvae obtained from different types of agricultural and non-agricultural localities in Peninsular Malaysia were subjected to several larvicides at World Health Organization (WHO) recommended dosages. Upon 24 h of WHO larval bioassay using two organochlorines and six organophosphates, high resistance against dichlorodiphenyltrichloroethane (DDT), temephos, chlorpyrifos and bromophos were demonstrated among all larval populations. Aedes albopictus larvae from both paddy growing areas (92.33% mortality) and rubber estates (97.00% mortality) were moderately resistant to dieldrin while only Ae. albopictus larvae from dengue prone residential areas (89.00% mortality) showed high resistance against dieldrin. All Ae. albopictus larval populations also developed either incipient or high resistance to both malathion (33.67%-95.33% mortality) and fenitrothion (73.00%-92.67% mortality). Only Ae. albopictus larvae from fogging-free residential areas that were tolerant to fenthion (97.33% mortality), whereas Ae. albopictus larvae from dengue prone residential areas were highly resistant to the same organophosphate (88.33% mortality). Cross resistance between intraclass and interclass larvicides of organochlorines and organophosphates were also exhibited in this study. The present study provided baseline data on various susceptibility levels of Ae. albopictus larval populations from different types of agricultural and non-agricultural localities against organochlorines and organophosphates at WHO recommended dosages. Nevertheless, further susceptibility investigations are suggested using revised doses of larvicides established from the local reference strain of Ae. albopictus to prevent the underestimation or overestimation of insecticide resistance level among Ae. albopictus field strains of larvae.
Extensive usage and heavy reliance on insecticides have led to the development of insecticide resistance in the German cockroach, Blattella germanica (L.). Six field-collected strains of B. germanica from Singapore were used to investigate resistance to fipronil and dieldrin. The three strains (Boat Quay, Cavenagh Road, and Ghimmoh Road) with greatest resistance to fipronil were subjected to selection with fipronil bait up to the F5 generation. Synergism assay and molecular detection of a target site mutation were used to elucidate the mechanism of fipronil resistance in these strains. With the exception of the Cavenagh Road strain, all parental strains were susceptible to dieldrin. This strain exhibited resistance to dieldrin and fipronil with resistance ratios of 4.1 and 3.0, respectively. Piperonyl butoxide and S,S,S-tributylphosphorotrithioate were antagonistic toward fipronil toxicity in all strains. Bait selection significantly increased fipronil and dieldrin resistance in the three chosen strains, either in topical bioassay or bait evaluations. There was a significant positive relationship [y = (6,852.69 +/- 1,988.37) x - (708.93 +/- 1,226.28), where x = fipronil toxicity and y = dieldrin toxicity] between dieldrin and fipronil resistance levels, indicating significant cross-resistance between the insecticides. High frequencies of individuals possessing the Rdl gene mutation were found in the F5 generation of the three strains selected with fipronil bait. The synergism assays indicated that monooxygenase and esterase were not involved in fipronil resistance in the strains studied herein. The A302S Rdl mutation was the major mechanism contributing to fipronil and dieldrin resistance in these strains.