Angsumarn Chandrapatya

Contact Toxicity, Feeding Reduction, and Repellency of Essential Oils From Three Plants From the Ginger Family (Zingiberaceae) and Their Major Components Against Sitophilus zeamais and Tribolium castaneum

ABSTRACT The essential oils from rhizomes of Alpinia conchigera Griff, Zingiber zerumbet Smitt, Curcuma zedoaria (Berg.) Roscoe; their major compounds (camphene, camphor, 1,8-cineole, &agr;-humulene, isoborneol, &agr;-pinene, &bgr;-pinene and terpinen-4-ol); and synthetic essential oils comprised of mixtures of major pure compounds in the same ratios as the extracted essential oils were tested for contact, feeding reduction, and repellency against Sitophilus zeamais Motschulsky and Tribolium castaneum (Herbst) adults. Via topical applications, the three extracted oils had similar toxicity against S. zeamais (LD50, fiducial limits: 18–24 µg oil/mg insect). T. castaneum had similar sensitivity to all three oils (35–58 µg/mg), and it was less sensitive than S. zeamais. The LD50 values of synthetic A. conchigera and synthetic Z. zerumbet oils were similar to those of their corresponding extracted essential oils. The synthetic C. zedoaria oils showed lower contact toxicity than the extracted C. zedoaria oils to both insects. Sitophilus zeamais and T. castaneum were sensitive to terpinen-4-ol and isoborneol in contact toxicity tests. In antifeedant tests, the three extracted oils were able to decrease the consumption of flour disks, especially Z. zerumbet oils, whereas both insect species could feed on the flour disks treated with three synthetic essential oils. Only terpinen-4-ol deterred feeding in both insects. In repellency tests, A. conchigera oils at highest concentration repelled S. zeamais and T. castaneum. None of the synthetic essential oils repelled S. zeamais (315 µl/cm2) and T. castaneum (31 µl/cm2). Only terpinen-4-ol showed repellent activity against both insects.

Studies on eriophyid mites (Acari: Eriophyoidea): VII

ABSTRACT A new genus and five new species of eriophyid mites (Acari: Eriophyoidea) are described from Thailand. Aceria sarmentosae Chandrapatya, n.sp. causing leaf galls on Azima sarmentosa (Salvadoraceae), Criotacus tetraspermae Chandrapatya n.sp. causing leaf edge rolling on Salix tetraspermae (Salicaceae), and Vasates leucopyri Chandrapatya n.sp. vagrant on Securinega leucopyrus (Euphorbiaceae) belong to Eriophyidae. The new genus Vimola is related to Vilaia, Asetadiptacus and Neodiptilomiopus. Vimola syzygii Boczek, n.sp. vagrant on Syzygium samarangense (Myrtaceae) and Diptilomiopus securinegus Boczek, n.sp. vagrant on Securinega leucopyrus (Euphorbiaceae) belong to Diptilomiopidae, Rhyncaphytoptinae.

Excito-repellency properties of essential oils from Melaleuca leucadendron L., Litsea cubeba (Lour.) Persoon, and Litsea salicifolia (Nees) on Aedes aegypti (L.) mosquitoes

Abstract We compared the behavioral responses of Aedes aegypti females to essential oils extracted from native plants Melaleuca leucadendron (ML), Litsea cubeba (LC), and Litsea salicifolia (LS) by using an excito-repellency test chamber. Mortality of Ae. aegypti females following 24 h holding period post-contact and non-contact trials were observed. No mortality was seen in escaped mosquitoes after direct contact with essential oils ML and LS, and low mortality (2.3–20.4%) with LC. Likewise, in all non-contact trials, no mortality was observed in escaped females from all three treatments, whereas low mortality was seen in non-escaped mosquitoes exposed to LC (0–14.3%) and LS (0–17.1%). Ae. aegypti showed significantly higher escape rates from contact chambers treated with ML and LC compared to LS, regardless of test concentrations (P<0.05). Non-contact repellent responses were significantly pronounced with LS, except at the highest (6.0%) concentration. We conclude that essential oils from all three botanicals exhibit significant irritant and repellent properties against Ae. aegypti and deserve further investigation for possible use as active ingredients in topical (skin) and indoor dispersed repellent systems.

Phylogenetic and cophylogenetic relationships of entomopathogenic nematodes (Heterorhabditis: Rhabditida) and their symbiotic bacteria (Photorhabdus: Enterobacteriaceae)

Mutualistic association between entomopathogenic Photorhabdus bacteria and Heterorhabditis nematodes represents one of the emerging model systems in symbiosis studies, yet little is known about this partnership from a coevolutionary perspective. Herein, we investigated phylogenetic and cophylogenetic relationships of Heterorhabditis and Photorhabdus strains using molecular markers Internal Transcribed Spacer and gyrase B gene sequences, respectively. The phylogenies presented consistent, well supported, monophyletic groups in the parsimonious and likelihood analyses for both the nematode and bacterial strains and supported the placement of currently recognized taxa, from which a potentially new Heterorhabditis species represented by a Thailand strain MP68 was identified. While the nematode strains with distant geographic distributions showed no detectable phylogenetic divergence within H. bacteriophora or H. georgiana monophyletic groups, their respective symbiotic bacteria speciated into two Photorhabdus species: P. luminescens and P. temperata, indicating the occurrence of duplication. Although such evolutionary process reduces the phylogenetic congruence between Heterorhabditis nematodes and Photorhabdus bacteria, global cophylogenetic tests using ParaFit detected a highly significant correlation between the two phylogenies (ParaFitGlobal = 0.001). Further, the associations between H. zealandica, H. indica and H. megidis strains and their symbiotic bacteria exhibited significant contribution to the overall cophylogenetic structure. Overall, this study reveals evidence of coevolution between Photorhabdus bacteria and Heterorhabditis nematodes and provides a framework for further examination of the evolution of these associations.

Biology and efficacy of the predatory mite, Amblyseius longispinosus (Evans) (Acari, Phytoseiidae) as a biological control agent of Eotetranychus cendanai Rimando (Acari, Tetranychidae)

Egg, larval, protonymphal and deutonymphal stages of Amblyseius longispinosus (Evans) that fed on Eotetranychus cendanai, required 2.02 ± 0.13, 0.57 ± 0.17, 1.07 ± 0.31 and 1.16 ± 0.53 days, respectively. The total developmental time was 4.79 ± 0.61 days. Female longevity averaged 14.61 ± 2.88 days in which 19.54 ± 6.36 eggs/female or 1.33 ± 0.29 eggs/female per day were laid. The highest predation rate was detected at a prey density of 40–50. Amblyseius longispinosus could be employed as the biological control agent of E. cendanai both in laboratory and greenhouse conditions at the predator : prey ratio of 1 : 30 to 1 : 50.

Detection of the toxin Hirsutellin A from Hirsutella thompsonii.

A total of 162 strains of Hirsutella thompsonii, isolated from infected mites collected worldwide, were examined for the production of Hirsutellin A (HtA). More than half of the broth filtrates exhibited mortality rates superior to 50% when assayed against Galleria mellonella. The presence of the gene coding for HtA, a previously characterized H. thompsonii protein exotoxin, was determined by PCR amplification using gene-specific primers. Most isolates (100 out of 162) were shown to possess the HtA gene. However, the presence of the gene could not be associated with enhanced insecticidal activity. Both isolate groups (with or without an amplifiable HtA gene) produced filtrates that caused the same average mortality rate (65%) when assayed against G. mellonella. The production and secretion of the HtA toxin were estimated by probing broth filtrates with an anti-HtA monoclonal antibody. Again, the detection of the HtA protein was poorly correlated with subsequent mortality rates induced by the broth filtrates of the various H. thompsonii strains. This study suggests that HtA is requisite for neither survival nor pathogenicity, and that H. thompsonii strains are likely to secrete other toxins that have yet to be characterized. Sequencing of a limited number of HtA genes showed that, when present, the gene is highly conserved, and it displays an interesting intronic polymorphism.

Biology and life table of the cassava mite, Tetranychus truncatus Ehara (Acari: Tetranychidae)

Abstract The life history and life table of Tetranychus truncatus Ehara onmulberry leaflets were studied under laboratory conditions at 20, 24, 28, 31 and 35°C. Mites completed their development and produced offspring within this temperature range. The development time from egg to adult varied from 6.30 to 14.89 days. The highest immature mortality was 39.88%at 20°C followed by 30.70%at 35°C. The threshold temperatures of egg, larva, protonymph, deutonymph, and a generation were 11.38, 9.91, 10.67, 12.51 and 11.57°C whereas the day-degree requirement at each stage was 62.52, 15.38, 11.36, 11.76 and 142.83 Do, respectively. The highest number of eggs laid by fertilized females was 65.6 eggs at 24°C, followed by 64.78 eggs at 31°C. Fertilized females lived up to 28.41 days at 20°C and only 9.63 days at 35°C. Unfertilized females survived relatively longer at 24°C and produced slightly more eggs at 24 and 28°C. The net reproductive rate (Ro) was the highest (37.39) at 24°C, followed by 37.00 at 31°C. The innate capacity for increase (rm) and finite rate of increase (λ) reached maximal values (0.321 and 1.378) at 31°C, whereas minimal values (0.134 and 1.143) were at 20°C. The mean generation time was the shortest at 35°C and the shortest time for a population to double was 2.16 days at 31°C. The highest population trend index (49.49) was obtained at 24°C, followed by 48.58 at 31°C. The overall results suggested that T. truncatus could develop and reproduce within a wide range of temperatures. The range 24–31°C was the most suitable for the development, survival rate and reproduction of this mite.

Synergistic Repellent and Irritant Effect of Combined Essential Oils on Aedes aegypti (L.) Mosquitoes

ABSTRACT: This study was designed to compare the behavioral responses of Aedes aegypti to a single essential oil and to a mixture of two or three essential oils using an excito-repellency test chamber. Mixtures were prepared from essential oils extracted from Litsea cubeba (LC), Litsea salicifolia (LS), and Melaleuca leucadendron (ML). In general, the mixture of essential oils produced a much stronger escape response by Ae. aegypti, regardless of the test conditions. No significant difference in escape responses was seen when the mixture of oils was compared with a standard commercial product containing DEET. Greater contact irritancy was seen from mixed oils of LC and LS than with other mixed oils. Mixtures of LC and LS at 0.075% showed the highest synergistic action (65.5% escaped) compared to that with unmixed oil alone at the same concentration (LC=20% and LS=32.2%). In addition, mixtures of LC and LS at 0.075% demonstrated the highest non-contact repellency (62.7%) and showed a greater effect than the use of LC (20%) or LS (20.3%) alone. We conclude that mixtures of two essential oils show potential as active ingredients for mosquito repellents.

Sensilla on the mouthparts and antennae of the elephant louse, Haematomyzus elephantis piaget (Phthiraptera : haematomyzidae)

The labial palpus of the elephant louse Haematomyzus elephantis has six sensilla that represent three different types: trichoid, basiconic, and styloconic. Two rows of basiconic sensilla are situated on the dorsal and ventral surfaces of the rostrum, and each row consists of three sensilla. Male and female antennae have 15–17 trichoid sensilla situated on the scape, pedicel, and three antennal annuli. Both sexes have two sensilla basiconica on the dorsal surface of the pedicel near the junction of the scape and pedicel. Two coeloconic (tuft) sensilla are situated on the antennae of both sexes, one sensillum on each of the last two annuli. There are three plate organs, two on the last annulus and one on the penultimate annulus of the male and female antennae. Sexual dimorphism is exhibited in the male and female antennae, in that the male has about twice as many sensilla basiconica on the apex of the last annulus as does the female. The total number of sensilla basiconica on the apex of the male antennae is at least two times the number that is known to be present in any other species of lice.

Fast Population Growth in Physogastry Reproduction of Luciaphorus perniciosus (Acari: Pygmephoridae) at Different Temperatures

Abstract Luciaphorus perniciosus Rack is one of the most serious pests of several cultivated mushroom species including Ganoderma lucidum (Fr.), Flammulina velutipes Karst., Auricularia polytricha (Mont.) Saac., Lentinus polychrous Lev., and Lentinus squarrosulus (Mont.) Singer in Thailand. Adult female Lu. perniciosus produce offspring inside their physogastric hysterosomas, with all embryos developing through to the adult stage while remaining in the abdomen. Once the abdomen ruptures, the female parent dies and the offspring consisting of mostly fertilized female adults along with a few male adults continue to emerge from the cadaver of the mother for a period of several days. This peculiar type of reproduction after the death of the mother is a special case for life table analysis and has not been discussed previously in demographic analyses. In this study, the life table data of this mite fed on Le. squarrosulus were collected at 25, 30, and 35 °C and analyzed by using the age-stage, two-sex life table. The standard errors of population parameters were estimated by using the bootstrap technique (200,000 bootstraps). At 25, 30, and 35 °C, females started reproduction at ages 9, 5, and 3 d, respectively; the net reproductive rates (R 0) were 192.27, 253.81, and 234.11 offspring. Due to their rapid development and high fecundity, the r values were as high as 0.4189, 0.8653, and 1.0892 d–1 at 25, 30, and 35 °C, respectively. Computer projection indicated that the mushroom mites Lu. perniciosus is capable of a threefold daily increase at 35 °C.