Biological control using pathogenic microsporidia could be an alternative to chemical control of the diamondback moth (DBM) Plutella xylostella (Lepidoptera: Plutellidae). The microsporidium Nosema bombycis (NB) is one of the numerous pathogens that can be used in the Integrated Pest Management (IPM) of DBM. However, its pathogenicity or effectiveness can be influenced by various factors, particularly temperature. This study was therefore conducted to investigate the effect of temperature on NB infection of DBM larvae. Second-instar larvae at different doses (spore concentration: 0, 1×10²,1×10³,1×10⁴, and 1×10⁵) at 15°, 20°, 25°, 30° and 35°C and a relative humidity(RH) of 65% and light dark cycle (L:D) of 12∶12. Larval mortality was recorded at 24 h intervals until the larvae had either died or pupated. The results showed that the spore concentration had a significant negative effect on larval survival at all temperatures, although this effect was more pronounced (92%) at 35°C compared with that at 20 and 30°C (≃50%) and 25°C (26%). Histological observations showed that Nosema preferentially infected the adipose tissue and epithelial cells of the midgut, resulting in marked vacuolization of the cytoplasm. These findings suggest that Nosema damaged the midgut epithelial cells. Our results suggest that Nosema had a direct adverse effect on DBM, and could be utilized as an important biopesticide alternative to chemical insecticides in IPM.
This study was carried out in an oil palm plantation in Bandar Baharu, Kedah using monkey carcasses and focuses in documenting the decomposition and dipteran colonization sequences in 50 days. This is the first study of Diptera associated with the exploitation of carcasses conducted in the north of peninsular Malaysia during the dry and wet seasons thereat. During the process of decomposition in both seasons, five phases of decay were recognized namely fresh, bloated, active decay, advance decay and dry remain. In this decomposition study, biomass loss of carcass occurred rapidly during the fresh to active decay stage due to the colonization and feeding activity of the Diptera larvae. The duration of the fresh and bloated stages of decay were the same in wet and dry seasons but later stages of decay were markedly shorter during the wet season. Twenty one species of adult Diptera were identified colonizing carcasses in the study period. Among the flies from the family Calliphoridae, Chrysomya megacephala Fabricius and Chrysomya nigripes Aubertin were recognized as the earliest arrivals on the first day of exposure. Adult Ch. nigripes was abundant for approximately two weeks after placement of the carcasses. By comparing the percentages of adults collected during the study period, the calliphorids abundance in percentages in wet season was 50.83%, but in dry season, the abundance was only about 35.2%. In contrast, the percentage of Sphaeroceridae in wet season was only 3.33%, but in the dry season, the abundance was 20.8%. Dipteran in family Phoridae, Piophilidae, Sepsidae, Drosophilidae and Dolichopodidae colonized the carcasses for a long period of time and were categorized as long term colonizers.
Sexually anomalous individuals, typically intersexes or gynandromorphs, bear a mixture of male and female traits. Twelve sexually anomalous individuals of the black fly Simulium (Gomphostilbia) trangense Jitklang, Kuvangkadilok, Baimai, Takaoka & Adler were discovered among 49 adults reared from pupae. All 12 sexually anomalous adults were parasitized by mermithid nematodes, although five additional parasitized adults had no overt external anomalies. Sequence analysis of the 18S rRNA gene revealed that the mermithids, possibly representing a new species, are related to Mesomermis spp., with genetic distances of 5.09-6.87%. All 12 anomalous individuals had female phenotypical traits on the head, thorax, forelegs, midlegs, and claws, but male features on the left and right hind basitarsi. One individual had mixed male and female genitalia. The findings are in accord with the trend that mermithid infections are associated with sexually anomalous adult black flies.
Effects of laterite cover soil with different characteristics on survival of buried eggs, third instar larvae, and pupae of Musca domestica (L.) were studied experimentally. Soil treatments were loose dry soil, loose wet soil, compacted dry soil, and compacted wet soil (CWS). Eggs, third instar larvae, and pupae were buried under 30 cm of the different soil treatments and placed under field conditions until adults emerged. Rearing medium was provided for eggs and larvae, and control treatments of all stages were unburied immatures placed on soil surface. Egg and pupal survival to adult were significantly affected by the cover soil treatments, but third instars were more resilient. Wet soil treatments (loose wet soil and CWS) resulted in significantly reduced pupal survival, but increased survival of eggs. However, CWS significantly reduced adult emergence from buried eggs. Though emergence of house flies buried as eggs was significantly reduced, some were able to hatch and emerging first instar larvae developed to pupation. Although cover soil does not completely prevent fly emergence, it did limit development and emergence of buried house flies.
Salmacis sphaeroides (Linnaeus, 1758) is one of the regular echinoids, occuring in the warm Indo-West Pacific, including Johor Straits, between Malaysia and Singapore. In order to investigate the developmental basis of morphological changes in embryos and larvae, we documented the ontogeny of S. sphaeroides in laboratory condition. Gametes were obtained from adult individuals by 0.5 M KCl injection into the coelomic cavity. Fertilization rate at limited sperm concentration (10(-5) dilution) was 96.6 ± 1.4% and the resulting embryos were reared at 24°C. First cleavage (2-cell), 4-cell, 8-cell, 16-cell, 32-cell, and multicell (Morulla) stages were achieved 01.12, 02.03, 02.28, 02.51, 03.12, and 03.32 h postfertilization. Ciliated blastulae with a mean length of 174.72 ± 4.43 μm hatched 08.45 h after sperm entry. The gastrulae formed 16.15 h postfertilization and the archenteron elongated constantly while ectodermal red-pigmented cells migrated synchronously to the apical plate. Pluteus larva started to feed unicellular algae in 2 d, grew continuously, and finally attained metamorphic competence in 35 d after fertilization. Metamorphosis took approximately 1 h 30 min from attachment to the complete resorption of larval tissues and the development of complete juvenile structure with adult spines, extended tubefeet and well-developed pedicellaria, the whole event of which usually took place within 1 d postsettlement. This study represents the first successful investigation on embryonic, larval, and early juvenile development of S. sphaeroides. The findings would greatly be helpful towards the understanding of ontogeny and life-history strategies, which will facilitate us to develop the breeding, seed production, and culture techniques of sea urchins in captive condition.
The composition of fish larvae and their diversity in different habitats are very important for fisheries management. Larval fishes were investigated in a mangrove estuary of Marudu Bay, Sabah, Malaysia from October 2012 to September 2013 at five different sites. Monthly samples of fish larvae were collected at five sampling sites by a plankton net with a mouth opening of 40.5 cm in diameter. In total, 3879 larval fish were caught in the investigated area. The mean density of ichthyoplankton at this area was 118 larvae/100 m(3). The fish larval assemblage comprised of 20 families whereas 13 families occurred at St1, 16 at St2, 16 at St3, 12 at St4 and 16 at St5. The top major families were Sillaginidae, Engraulidae, Mugilidae and Sparidae with Sillaginidae consisted 44% of total larval composition. St3 with 143 larvae/100 m(3) had the highest density amongst the stations which was due to higher abundance of Sillaginidae. Shannon-Wiener diversity index represented significant variation during monsoon and inter-monsoon seasons, peaking in the months December-January and May-June. However, Shannon-Wiener index, evenness and family richness showed significant differences among stations and months (p < 0.05).
To determine resistance level and characterize malathion and permethrin resistance in Culex quinquefasciatus, two methods were used namely: WHO procedures of larval bioassay to determine the susceptibility of lethal concentration (LC) and adult bioassay to determine the lethal time (LT) which are resistant to malathion and permethrin. These mosquito strains were bred in the Insectarium, Division of Medical Entomology, IMR. Thousands of late fourth instar larvae which survived the selection pressure to yield 50% mortality of malathion and permethrin were reared and colonies were established from adults that emerged. Larvae from these colonies were then subjected to the subsequent 10 generations in the test undertaken for malathion resistant strain (F61 - F70) and permethrin resistant strain (F54 - F63). Selection pressure at 50% - 70% mortality level was applied to the larvae of each successive generation. The rate of resistance development and resistance ratio (RR) were calculated by LC5 0 for larval bioassay and LT50 value for adult bioassay. The lab bred Cx. quinquefasciatus was used as a susceptible strain for comparison purpose. The adult bioassay test was carried out by using diagnostic dosages of malathion 5.0%, permethrin 0.75% and with propoxur 0.1%. All bioassay results were subjected to probit analysis. The results showed that LC5 0 for both malathion (F61 - F70) and permethrin (F54 - F63) resistant Cx. quinquefasciatus increased steadily to the subsequent 10 generations indicating a marked development of resistance. The adult female malathion resistant strain have developed high resistance level to malathion diagnostic dosage with resistance ratio 9.3 to 9.6 folds of resistance. Permethrin resistance ratio remained as 1.0 folds of resistance at every generation. It was obvious that malathion resistance developing at a higher rate in adult females compared to permethrin. Female adults exposed to 2 hours of exposure period for propoxur 0.1% showed presence of cross-resistance among the both strains of mosquitoes towards propoxur and it was indicated by 70%-100% mortality at 24 hours post-recovery period.
The aim of this study is to determine the Spodoptera exigua larva population in the field and factor affecting their density. Population study of S. exigua larva and its affecting factors was carried out in Sekinchan, Selangor during 2003-2004. The larval density was found fluctuating during the study, where the highest number of larvae was an averaged of 18.17 per m2, while the lowest number was an averaged of 1.5 per m2. The mean number of larvae per plant also varies from 1.83 to 5.42. It was found that the larval density was influenced by the age and availability of the host plant. A total of 1881 larvae were collected, where 18.29 and 20.31% were successfully becoming female and male moths, respectively; 20.63% was being parasitized, where 7.07, 11.43, 0.11 and 2.02% were being parasitized by Microplitis manilae, Chelonus sp., Temelucha sp. and Peribaea orbata, respectively. Besides that, other biotic factors such as fungal or bacterial infection also cause death to the S. exigua larva, where a total of 1.91 and 10.89% were infected by them, respectively. Whilst 16.64% of the collected larvae were dead due to pesticide and 7.44% were not known cause of the death. Besides that, 3.89% of the S. exigua died during pupal stage or emergence. Further, climatic factor was found not influencing the larva populations. There were no correlation between the number of larva collected with the means of temperature, relative humidity and rainfall.
Morphological mentum deformities which represent sublethal effect of exposure to different types of pollutants were evaluated in Chironomus spp. larvae inhabiting three polluted rivers of Juru River Basin in northwestern peninsular Malaysia. Using mentum deformity incidences, the modified toxic score index (MTSI) was developed based on Lenat's toxic score index (TSI). The suggested MTSI was compared with TSI in terms of its effectiveness to identify different pollutants including heavy metals. The MTSI showed stronger relationship to total deformity incidence expressed as percentage. Additionally, the multivariate RDA model showed higher capability of MTSI to explain the variations in heavy metal contents of the river sediments. The MTSI was recommended in bioassessment of water and sediment quality using the mentum deformities of Chironomus spp. larvae from aquatic ecosystems receiving anthropogenic, agricultural, or industrial discharges.
The red palm weevil (RPW), Rhynchophorus ferrugineus Olivier (Coleoptera: Dryophthoridae) is one of the most dangerous pests of major cultivated palms including coconut, oil palm, and sago. The larval stage of the weevil causes the most destruction of the palms as it completely destroys the palm cabbage. In this study, the larvae were given three different diets-coconut cabbage, oil palm cabbage, and sago stem, under laboratory conditions for food consumption and developmental time experiment. The protein profiles of the digestive systems of the larvae fed on these three diets were also determined. Although the coconut diet was the most consumed by RPW larvae compared to oil palm and sago diets, the growth rate of RPW larvae on oil palm diet was however significantly shorter than those on the coconut and sago diets: the RPW only need 1 mo and 9 d to complete the larval duration. Proteins profiling of eight 2-DE gel protein spots that range 50-20 kDa were identified by mass spectrometry sequence analysis. Based on the Matrix Science Software, the most dominant protein was cationic trypsin. However, based on the NCBI BLAST tool, aminopeptidase N was the most dominant enzyme. This finding can lead to the development of pest control strategies based on the antinutritional protease inhibitors as potential biocontrol agents. Urgent action to find effective control methods should be taken seriously as this weevil is presumed to be one of the serious pests of oil palm industry in Malaysia.
This preliminary study was carried out in a palm oil plantation in Tanjung Sepat, Selangor in 17 May 2007 by using pig (Sus scrofa) as a carcass model in forensic entomological research. A 3 month old pig (8.5 kg) that died of pneumonio was placed in the field to observe the decomposition stages and the fauna succession of forensically important flies. Observation was made for two weeks; two visits per day and all climatological data were recorded. The first visitor to the pig carcass was a muscid fly, seen within a minute, and followed by ants and spiders. Within half an hour, calliphorid flies came over. On the second day (fresh), few calliphorid and sarcophagid flies were found on the carcass. Two different species of moths were trapped in the hanging net. The first larva mass occurred on the third day (bloated) around the mouthpart, with some L1 and L2 found in the eyes. Reduvid bugs and Staphylinidae beetles were recovered on the fourth day (active decay), and new maggot masses occurred in the eyes and anus. L3 larvae could be found beneath the pig carcass on the fourth day. On the fifth day (active decay), new maggot masses were found on neck, thorax, and hind legs. Advance decay occurred on the sixth day with abundant maggots covering all over the body. The main adult fly population was Chrysomya megacephala (day 2 to day 6), but the larvae population was mainly those of Chrysomya rufifacies (day 4 to day 14). The dry stage began on the eighth day. Hermetia illucens adult was caught on day-13, and a larvae mass of Chrysomya rufifacies was seen burrowing under the soil. This forensic entomological research using pig carcass model was the first record in this country.
This entomological study was conducted in a man-made freshwater pond in a palm oil plantation in Tanjung Sepat, Selangor from 23 July 2007 by using pig (Sus scrofa) as a carcass model. A 1.5 month old piglet (5 kg), which died of asphyxia after being accidentally crushed by its mother, was thrown into a pond. Observation was made for ten days; one visit per day and climatological data were recorded. On the first two days, the piglet carcass sunk to the bottom of the pond. The carcass floated to the surface on the third day but no fly activities were seen. The blow fly, Chrysomya megacephala and Chrysomya rufifacies started to oviposit on the fourth day. Other than adult flies, a spider (Arachnida) was also observed on the carcass. Bubbles accumulated at the mouthpart, and the abdomen was greenish black. A lot of blow fly eggs were seen on the body surface on the fifth day (floating decay), along with first and second instars C. megacephala crawling under the piglet's skin. On the sixth day, adult blow fly, C. megacephala,and C. rufifacies,and muscid flies, Ophyra spinigera and Musca domestica were observed on to the carcass. High numbers of first and second instars of flies were observed wandering around the body surface with C. megacephala larvae being the predominant species. Two prominent maggot masses occurred on seventh and eighth days. Bloated deterioration stage began on day eighth exposing rib bones, humerus bones and intestines. Carcass was partially sinking and the maggot masses were at the water level. On day ninth, the carcass was partially sinking and three maggot masses were observed on the exposed surface. There were very few adult flies, including a scarab beetle was sighted on the carcass at this stage. The carcass along with the maggots sunk on day tenth, leaving an oily layer on the water surface.
Life tables were constructed for twelve cohorts of immature stages of the dengue vector Ae. albopictus in a wooded area of Penang, Malaysia. The development time of Ae. albopictus ranged from 6 to 10 days depending on the mean environmental temperature (r = - 0.639, p < 0.05). Total cohort mortality was correlated with total development time (r = 0.713, p < 0.05) but not temperature (r = -0.477, p > 0.05). Rainfall was correlated with neither development time (r = 0.554, p > 0.05) nor mortality (r = 0.322, p > 0.05). There was a significant difference among the total mortality that occurred in the twelve cohorts (H = 119.783, df = 11, p < 0.05). There was also a significant difference in mortality among the different stages (H = 274.00, df = 4, p < 0.05).
Malaria, the most widespread mosquito-borne disease, affects 350-500 million people each year. Eco-friendly control tools against malaria vectors are urgently needed. This research proposed a novel method of plant-mediated synthesis of silver nanoparticles (AgNP) using a cheap seaweed extract of Ulva lactuca, acting as a reducing and capping agent. AgNP were characterized by UV-vis spectrophotometry, Fourier transform infrared (FTIR) spectroscopy, energy-dispersive X-ray spectroscopy (EDX), scanning electron microscopy (SEM), and X-ray diffraction (XRD). The U. lactuca extract and the green-synthesized AgNP were tested against larvae and pupae of the malaria vector Anopheles stephensi. In mosquitocidal assays, LC50 values of U. lactuca extract against A. stephensi larvae and pupae were 18.365 ppm (I instar), 23.948 ppm (II), 29.701 ppm (III), 37.517 ppm (IV), and 43.012 ppm (pupae). LC50 values of AgNP against A. stephensi were 2.111 ppm (I), 3.090 ppm (II), 4.629 ppm (III), 5.261 ppm (IV), and 6.860 ppm (pupae). Smoke toxicity experiments conducted against mosquito adults showed that U. lactuca coils evoked mortality rates comparable to the permethrin-based positive control (66, 51, and 41%, respectively). Furthermore, the antiplasmodial activity of U. lactuca extract and U. lactuca-synthesized AgNP was evaluated against CQ-resistant (CQ-r) and CQ-sensitive (CQ-s) strains of Plasmodium falciparum. Fifty percent inhibitory concentration (IC50) values of U. lactuca were 57.26 μg/ml (CQ-s) and 66.36 μg/ml (CQ-r); U. lactuca-synthesized AgNP IC50 values were 76.33 μg/ml (CQ-s) and 79.13 μg/ml (CQ-r). Overall, our results highlighted out that U. lactuca-synthesized AgNP may be employed to develop newer and safer agents for malaria control.
The larval growth of Liosarcophaga dux Thompson (Diptera: Sarcophagidae) was studied under varying indoor room temperatures in Malaysia. Five replicates were established. The immature growth of this species from first instar until adult emergence was 307.0+/-3.0 hours. The mean larval length measured for second instar, third instar, post-feeding stage and puparia were 6.5+/-0.5 mm (n=10), 11.8+/-3.7 mm (n=31), 12.7+/-0.8 mm (n=16), and 9.5+/-0.5 mm (n=15), respectively.
A burned human remain was found outdoor (5º 27' N, 100º 16' E) in Penang Island. The deceased was last seen alive on 23 April 2010 at 2230 h and was found burned on 24 April 2010 at 1920 h. Larval aggregation of second instar Chrysomya megacephala was observed on the chest of the deceased.
Larvae of the Synthesiomyia nudiseta (Wulp) were collected from a decomposed human corpse at the Department of Forensic Medicine, Penang Hospital. A colony of this species was established and the eggs were collected for rearing. The developmental times, rearing temperatures, and relative humidity were recorded twice daily from the time the eggs collected until adult emergence. An average of 5 larvae were randomly collected from the rearings twice daily, warm-water killed and preserved in Kahle's solution. The larval instar stages were determined by observing the number of posterior spiracular slits and the length of the preserved larvae were measured. When the larval life cycle was completed, the accumulated developmental times were calculated. A total of 8 replicates were carried out. The temperature of the rearing room was 28.5+/-1.5 degrees Celcius while the relative humidity was within 67-85%. The total developmental time for S. nudiseta was 322+/-19 hours (13.4+/-0.8 days).
Aedes-borne virus disease control relies on insecticides to interrupt transmission. Temephos remains a key chemical for control of immature stage Aedes in Thailand and much of Southeast Asia. However, repeated use of insecticides may result in selection for resistance in vector populations, thus compromising operational intervention. Herein, the phenotypic response to temephos by Aedes aegypti (L.) and Aedes albopictus (Skuse) collected in Thailand and surrounding countries is presented. Data from 345 collection sites are included: 283 from literature review (244 sites with Ae. aegypti, 21 with Ae. albopictus, and 18 having both species sampled), plus 62 locations with Ae. aegypti in Thailand conducted between 2014 and 2018. Susceptibility assays followed WHO guidelines using the recommended discriminating dose of temephos (0.012 mg/liter) against late third to early fourth instar Ae. aegypti. Findings revealed 34 locations with susceptible Ae. aegypti, 13 with suspected resistance, and 15 indicating resistance. Published data between 1999 and 2019 in Thailand found Ae. aegypti resistant in 73 of 206 collection sites, whereas 3 locations from 11 sampled with low-level resistant in Ae. albopictus. From surrounding countries conducting temephos assays (Cambodia, Lao PDR, Myanmar, Malaysia, and Singapore), resistance is present in Ae. aegypti and Ae. albopictus from 27 of 56 and 19 of 28 locations, respectively. Routine insecticide susceptibility monitoring should be an operational requirement in vector control programs. Given the wide distribution and apparent increase in temephos-resistance, alternative larvicidal compounds must be considered if chemical control is to remain a viable vector control strategy.
The genus Mansonia is divided into two subgenera, Mansonia and Mansonioides. The subgenus Mansonioides includes the important vectors of lymphatic filariasis caused by Brugia malayi in South and Southeast Asia. Six species of this subgenus are vectors of two types of brugian filariasis, periodic and subperiodic. All six species, viz Mansonia bonneae, Ma. dives, Ma. uniformis, Ma. annulifera, Ma. annulata and Ma. indiana are present in this country. The ecological factors governing the larval and adult biology and their control measures are discussed.
The compatibility of the commercial aqueous Bacillus thuringiensis serovar israelensis (B.t.i.) formulation, Vectobac 12AS, with the chemical insecticides Actellic 50EC, Aqua Resigen, Resigen, and Fendona SC, for the simultaneous control of Aedes larvae and adults was studied by dispersing nine different formulations using a portable mist blower, in single story half-brick houses. The effectiveness of the treatment was evaluated by measuring the larval mortality, adult mortality, and droplet analysis at varying distances from the sprayer. Persistence of the larvicidal activity of the chemical insecticides and B.t.i was also determined by measuring the larval mortality in the test samples 7 days posttreatment. The sprayed particles in all the trials were 50-60 microns in size, indicating that the particles were those of mist spray. Test samples placed within 3 m from the sprayer gave the maximum larval and adult mortality. Chemical insecticides exhibited maximum larval mortality in the 1 h posttreatment test samples and it was comparable to the larvicidal activity of B.t.i. The larvicidal toxins of B.t.i were more stable and were able to affect sufficient larval mortality for 7 days posttreatment. The larvicidal activity of the mixtures, i.e., chemical insecticides with B.t.i, in the 1 h posttreatment test samples was not significantly different from the larvicidal activity of the chemical insecticides and it was comparable to the larvicidal activity of B.t.i alone. However, the larvicidal activity of the mixtures was significantly more than the chemical insecticides alone in the 7 days posttreatment test samples except for the Actellic 50EC and Vectobac 12AS mixture. In all the trials, with or without B.t.i, there was no significant difference in adult mortality, indicating that this B.t.i formulation, Vectobac 12AS, was not antagonistic to the adulticidal activity of the chemical insecticides. From this study, it can be concluded that chemical insecticides can be used effectively for both adult and larval control, but the chemical insecticides do not exhibit residual larvicidal activity. Hence, for an effective control of both Aedes larvae and adults, it is advisable to add B.t.i. to the chemical insecticides, as B.t.i is specifically larvicidal and is also able to effect extended residual larvicidal activity.