M. R. Che Salmah

Indoor-breeding of Aedes albopictus in Northern Peninsular Malaysia and its potential epidemiological implications.

Background The mosquito Ae. albopictus is usually adapted to the peri-domestic environment and typically breeds outdoors. However, we observed its larvae in most containers within homes in northern peninsular Malaysia. To anticipate the epidemiological implications of this indoor-breeding, we assessed some fitness traits affecting vectorial capacity during colonization process. Specifically, we examined whether Ae. albopictus exhibits increased survival, gonotrophic activity and fecundity due to the potential increase in blood feeding opportunities. Methodology/Principal Findings In a series of experiments involving outdoors and indoors breeding populations, we found that Ae. albopictus lives longer in the indoor environment. We also observed increased nighttime biting activity and lifetime fecundity in indoor/domestic adapted females, although they were similar to recently colonized females in body size. Conclusion/Significance Taken together these data suggest that accommodation of Ae. albopictus to indoor/domestic environment may increase its lifespan, blood feeding success, nuisance and thus vectorial capacity (both in terms of increased vector-host contacts and vector population density). These changes in the breeding behavior of Ae. albopictus, a potential vector of several human pathogens including dengue viruses, require special attention.

The effects of simulated rainfall on immature population dynamics of Aedes albopictus and female oviposition

Larvae of Aedes albopictus Skuse typically inhabit natural and artificial containers. Since these larval habitats are replenished by rainfall, Ae. albopictus may experience increased loss of immature stages in areas with high levels of rainfall. In this study, we investigated the effects of rainfall and container water level on population density, and oviposition activity of Ae. albopictus. In field and laboratory experiments, we found that rainfall resulted in the flushing of breeding habitats. Excess rain negatively impacted larval and pupal retention, especially in small habitats. When filled with water to overflowing, container habitats were significantly repellent to ovipositing females. Taken together, these data suggest that rainfall triggers population loss of Ae. albopictus and related species through a direct detrimental effect (flushing out) and an indirect effect (ovipositional repellency).

Species Composition and Population Dynamics of Thrips (Thysanoptera) in Mango Orchards of Northern Peninsular Malaysia

ABSTRACT Thrips are key pests of mango, Mangifera indica (L.), in Malaysia, including the Northern Peninsular. As Penang has year-round equatorial climate and high of rainfall, the populations of thrips may be subject to variations in composition and size. With a goal of developing an appropriate control strategy, a survey was conducted in Penang to determine species composition and abundance in relation to some environmental factors. Sprayed and unsprayed orchards were sampled on weekly basis through two flowering seasons of 2009 using CO2 collection technique. Larval population falling into the ground to pupate and adults emerging from the soil were investigated in both orchards. Thrips hawaiiensis (Morgan) and Scirtothrips dorsalis (Hood) were the most prevalent species in the sprayed and the unsprayed orchards, respectively. The abundance of thrips was high during the flowering period of the dry season and decreased during the flowering period of the rainy season. This latter period coincided with decreased temperature and increased relative humidity. Percentage of adult emergence from the soil was lower in the rainy season than recorded in the dry season in both orchards. Taken together, these observations suggest that T. hawaiiensis and S. dorsalis are the main thrips species pests of mango panicles in Penang. Direct control with insecticides focusing on these two species may help to reduce cosmetic injuries and other damages on mango fruits.

Pollination Services of Mango Flower Pollinators.

Measuring wild pollinator services in agricultural production is very important in the context of sustainable management. In this study, we estimated the contribution of native pollinators to mango fruit set production of two mango cultivars Mangifera indica (L). cv. ‘Sala’ and ‘Chok Anan’. Visitation rates of pollinators on mango flowers and number of pollen grains adhering to their bodies determined pollinator efficiency for reproductive success of the crop. Chok Anan failed to produce any fruit set in the absence of pollinators. In natural condition, we found that Sala produced 4.8% fruit set per hermaphrodite flower while Chok Anan produced 3.1% per flower. Hand pollination tremendously increased fruit set of naturally pollinated flower for Sala (>100%), but only 33% for Chok Anan. Pollinator contribution to mango fruit set was estimated at 53% of total fruit set production. Our results highlighted the importance of insect pollinations in mango production. Large size flies Eristalinus spp. and Chrysomya spp. were found to be effective pollen carriers and visited more mango flowers compared with other flower visitors.

Influence of physical and chemical factors on the larval abundance of Neurothemis tullia (Drury) (Odonata:Libellulidae) in a rain fed rice field

The influence of physical and chemical factors such as pH, temperature, conductivity, dissolved oxygen, nitrate, phosphate and chlorophyll a on larval populations of Neurothemis tullia (Drury) (Odonata:Libellulidae) were studied in a rain-fed rice field by collecting larvae and water samples weekly over two seasons of rice planting. Water availability was the main factor determining the presence or absence of larvae in the rice field. The larvae were most abundant during extended periods of continuously plentiful water supply except during flooding. Rapid larval population build-ups were observed soon after chemical applications or spells of dry periods reflecting continual oviposition and hatching of eggs. Pesticides and fertilizer applications resulted in low population densities due to direct or indirect mortality. A stepwise multiple regression showed that within its range, none of the physical and chemical factors measured in this study affected the abundance of N. tullia.

Oviposition Preference and Nutritional Indices of Papilio polytes L. (Papilionidae) Larvae on Four Rutaceous (Sapindales: Rutaceae) Host Plants

ABSTRACT. Oviposition preference and larval developmental performance of the butterfly, Papilio polytes L. on four rutaceous host plants, Citrus aurantifolia (Chrism.) Swing, Citrus reticulata Blanco, Citrus hystrix DC, and Murraya koenigii (L.) Sprengle, were investigated in outdoor cages. Maxima of eggs were laid on C. reticulata, followed by C. aurantifolia, but the numbers laid on the two host plants were not significantly different from each other; however, these numbers differed significantly (F = 155.70; P < 0.01) from those laid on C. hysrix and M. koenigii; the last host plant was the least preferred for egg laying. Leaves were significantly the preferred site (and in turn the underside of leaves) over stems for deposition of eggs in all host plants; negligible number of eggs was also laid on plant pots. The duration of 5th instar larval development was the shortest on C. reticulata and significantly different (P < 0.01) from that on M. koenigii, but did not differ significantly between the three Citrus species. The nitrogen content in leaves of all four host plants differed significantly (P < 0.01), with C. reticulata containing 4.52%, followed by C. aurantifolia (4.37%), C. hystrix (4.29%), and M. koenigii (3.73%), while the water content of leaves was significantly the lowest in M. koenigii (71.72%), compared to the three Citrus species (76.38–79.12%) among which the water content did not significantly differ. Relative consumption rate (RCR) and fecal dry weight of 5th instar larvae feeding on M. koenigii were the highest and significantly different (P < 0.01) from the other three host plants. Pupal dry weight, relative growth rate (RGR), efficiency conversion of digested food (ECD), efficiency conversion of ingested food (ECI) of M. koenigii were significantly lowest compared to the three Citrus species. The values of RGR, ECD, and ECI of the 5th instar larvae were similar for the three Citrus species; the approximate digestibility (AD) values were similar for all four host plants. This study shows that C. reticulata was the best host plant among the three Citrus spp. and M. koenigii was the least preferred.

Multitrophic system: Effect of different concentration of nutrient and pre-infested brinjal (Solanum melongena) on whitefly (Bemisia tabaci) population

The effect of nutrient concentrations and pre-infestation of brinjal (Solanum melongena) plant with pest species on population of whitefly (Aleyrodidae; Hemiptera) was investigated over a cropping period. Three dosages of nutrients (fertilizer) were applied on brinjal seedlings; N1–50ppm, N2–150ppm and N3–300ppm respectively. The brinjal seedlings were pre-infested with two pests, whitefly and aphid. The control plants were non-infested with any pest. Populations of whitefly were higher following increasing levels of nutrients in non-infested plants. No significant variation on mean population densities were observed among the sampling times. In the pre-infested brinjal plants, the level of nutrients did not influence the abundance of whitefly population infesting brinjal plants. Lower whitefly populations were observed on whitefly pre-infested brinjal plants compared to aphid infested and non-infested plants. Pre-infested plants were suspected to induce productions of secondary metabolites as a chemical defence system thus lowering the number of whiteflies on them. Whitefly populations were found higher during early growth of brinjal plants due to high number of leaves and good plant growth. Considering other management technique in controlling whiteflies on brinjal such as appropriate nutrient supplement and good pest care during seedling stage was proposed.

Oviposition preference of swallowtail butterfly, Papilio polytes （Lepidoptera Papilionidae） on four Rutaceae （Sapindales） host plant species

Abstract  Oviposition preference and egg deposition site selection by the butterfly, Papilio polytes L. (Lepidoptera: Papilionidae) on four rutaceous host plants, Citrus aurantofolia (Christm.) Swing., Citrus hystrix DC., Citrus reticulata Blanco, and Murraya koenigii (L.) Sprengel, were assessed in field cages measuring 2 × 2 × 2 m. Simultaneous two‐choice and four‐choice oviposition tests of whole host plants were conducted. The mean total number of eggs laid per plant on C. reticulata in the two‐choice test was significantly higher (P < 0.01) than those on C. aurantifolia, C. hystrix, and M. koenigii. Among the three other host plants, C. aurantifolia was preferred over C. hystrix, and M. koenigii (P < 0.01) and C. hystrix was preferred over M. koenigii (P < 0.01). In the four‐choice test, C. reticulata was highly preferred and significantly different from C. hystrix and M. koenigii. However, no oviposition preference was detected with C. aurantifolia. Among the various plant parts in the two‐ and four‐choice tests, eggs on leaves of each plant were the highest, followed by numbers on stems, and negligible numbers on pots. These numbers on leaves of C. reticulata and C. aurantifolia were not significantly different (P > 0.05), but differed significantly (P < 0.01) from those on leaves of C. hystrix and M. koenigii. The quantitative trend of egg‐laying on stems was very similar to that observed for the leaves. Papilio polytes showed strong preference to lay eggs on the underside of leaves of all host plants than on the upper side or on the petiole. More eggs were laid on the upper side of each host plant than on its petiole. The four host plants in descending order of preference were C. reticulata≥C. aurantifolia > C. hystrix > M. koenigii. Although M. koenigii was the least preferred, it has the potential to serve as an alternative host plant for P. polytes which can be manipulated when necessary, to alleviate the infestation of this pest to the citrus industry.