Screening of Some Crude Plant Extracts for Their Acaricidal and Insecticidal Efficacies

Methanol extracts from 28 samples of 22 plant species in 17 different plant families were tested at 10, 000 ppm for evaluating their insecticidal and acaricidal activities against Tetranychus urticae Koch, Aphis gossypii Glover, Myzus persicae Sulzer, Trialeurodes vaporariorum (Westwood), and Panonychus citri (McGregor). In a test with T. urticae, extracts from Albizzia coreana twig and Pyracantha angustifolia leaf possessed potent acaricidal activities. Reproduction of T. urticae for three days significantly decreased in the extract treatments of Gardenia jasminoides, Ficus carica, and Albizzia coreana twigs. Though slight repellent activities against T. urticae were obtained from extracts of Camellia japonica seed, G. jasminoides peel and fruits, Ligustrum japonicum leaves, A. coreana twig, and Machilus thunbergii leaves in 24 h after treatment, but tended to decrease in 72 h. Extracts of F. carica leaves and G. jasminoides fruits had potent insecticidal activities against M persicae and A. gossypii. Methanol extracts of F. carica leaves possessed insecticidal activity against T. vaporariorum. In a field test with P. citri, extracts from C. japonica seeds, A. coreana leaves, Ranunculus japonicus leaves and roots, an Houttuynia cordata leaves exhibited acaricidal activities.     

Grape downy mildew spread and mite seasonal abundance in vineyards: effects on Tydeus caudatus and its predators

Tydeus caudatus (Acari: Tydeidae) can prey upon grape eriophyoid mites but little is known about its alternative foods. Observations carried out during 1999–2003 in a commercial vineyard located in northeastern Italy showed that densities of T. caudatus were often correlated to downy mildew spread on the vegetation. Densities of T. caudatus increased in late summer when downy mildew symptoms occurred on a high number of leaves. The predatory mite Paraseiulus talbii (Acari: Phytoseiidae) increased in late season following the increase of tydeids. On several sampling dates, T. caudatus populations were significantly higher on leaves with downy mildew symptoms than on leaves without symptoms. Tydeid densities were often positively correlated to the extent of leaf surface showing symptoms. These relationships were sometimes found regarding P. talbii. In two experimental vineyards colonised by T. caudatus, untreated plots or plots treated with different fungicides to control downy mildew were monitored during 2002. Downy mildew infections rapidly spread in the control plots while they were effectively controlled on fungicide-treated plots. In both vineyards, T. caudatus densities reached significantly higher densities in the control than on fungicide-treated plots. A field study showed that most of these fungicides did not reduce tydeid populations when downy mildew was virtually absent. Isoelectric-focusing electrophoresis (IEF) was used to detect downy mildew in mites. Glucose phosphate isomerase (GPI) was selected from among different enzymes. A high proportion of T. caudatus females, collected from infected leaves, and analysed under IEF showed a GPI isozyme allele corresponding to the downy mildew isozyme in addition to the tydeid intrinsic alleles. This phenomenon was also observed for P. talbii but with a lower incidence. All T. caudatus females confined on symptomatic leaves became positive by IEF after few hours but the same did not occur with P. talbii. A high proportion of P. talbii females became positive after preying on tydeids collected from symptomatic leaves or reared on pollen and then confined on symptomatic leaves.     

Genetic structure of Korean populations of bumblebees Bombus ignitus (Hymenoptera: Apidae) as revealed by microsatellite markers

Bumblebee Bombus ignitus, which is indigenous to Korea, Japan, and China, has been recognized as a valuable pollinator for both crops and wild plants. Bombus ignitus has now become commercially important as a pollinator because of its use in the agricultural industry, particularly for greenhouse pollination. For long‐term management and effective conservation of B. ignitus, an understanding of the genetic structure of its naturally occurring populations is practically important. In this study, the genetic structure among the five populations of B. ignitus in South Korea was assessed using nine microsatellite loci. These markers showed high levels of genetic variability, with the number of alleles ranging from 6 to 22 (mean = 13.4) and the frequency of the most common allele ranging from 0.11 to 0.66. Only the Sabuk (SB) population showed a genetic signature of a recent bottleneck, which was further supported by the lowest level of allelic richness (AR) (mean AR = 3.944). Genetic differentiation was highly significant among all pairs of populations (P < 0.001) across the nine microsatellite markers, suggesting a lack of gene flow among those populations. Interestingly, F_ST (and R_ST and D_est) values were always greater for the Taebaek population than for the four remaining populations. The phylogenetic analysis showed evidence supporting our hypothesis that the Taebaek population is genetically more divergent than the other populations. Overall, our results suggest that the Korean populations of B. ignitus might have undergone geographic isolation and have become highly separated spatially from one another, thereby having a limited range of migration among their local habitats.     

Acquisition of Tomato yellow leaf curl virus enhances attraction of Bemisia tabaci to green light emitting diodes

The light sensitivity of insects varies in response to different wavelengths of light. The change of light responses of vector insects plays an important role in the method of transmission and propagation of plant viruses. Here, we investigated whether the light attraction behaviors of whiteflies are altered by virus acquisition. Firstly, the light attraction rates of whiteflies were determined using LED light bulbs exhibiting different wavelengths in the visible and UV spectra. Whiteflies, Bemisia tabaci and Trialeurodes vaporariorum, were mostly attracted to green LEDs (526 nm). The attraction rate to green LED light was higher in B. tabaci than in T. vaporariorum, whereas it did not significantly differ between the B- and Q-biotypes of B. tabaci. Secondly, we investigated whether or not the green light attraction behavior of B. tabaci is influenced by the acquisition of Tomato yellow leaf curl virus (TYLCV). The attraction rate to green LED light was 2.5–3 times higher in TYLCV-infected whiteflies than in TYLCV-free whiteflies. However, this difference disappeared when the distance from the light source was greater than 0.5 m. Our results show that B. tabaci favors green light and its attraction is highly enhanced by the acquisition of the plant virus, TYLCV.     

A new genus and species of Urodidae (Lepidoptera: Urodoidea) from Sri Lanka

A new genus of Urodidae, Geoesthia gen. nov., is described with the type species, Geoesthia ceylonica sp. nov. from Sri Lanka. This is the second urodid genus from the Oriental Region. The new species is the only urodid recorded from Sri Lanka. The new genus is distinguished from all the known genera within Urodidae by a combination of four characteristics: the lack of scale tufts on the labial palpi; the absence of raised scales of two subbasal spots on the forewings; the presence of M-stem on the hindwings; and the female corpus bursae bearing five signa. Key to the genera and species of Urodidae from the Oriental Region is provided.     

Molecular identification of glucose-regulated protein 78 (grp78) gene from the Indian meal moth,Plodia interpunctella,and its regulation by nutrient uptake

Glucose-regulated protein 78 (GRP78) is a member of the HSP70 family of proteins and is localized in the endoplasmic reticulum (ER) within cells. GRP78 and its gene has been identified in only a few species of insects, and its role is not clear. Here, we identified full-length grp78 cDNA from the Indian meal moth, Plodia interpunctella, and demonstrated the role of grp78 in developmental and physiological processes of the insect. The deduced amino acid sequence of GRP78 contained highly conserved functional motifs of the HSP70 family and the C-terminal motif of KDEL, which is characteristic of ER-localized HSP70. It also showed high identity (93–94%) with GRP78 and related HSP70 proteins of lepidopteran species. Gene expression analysis showed that grp78 mRNA levels were high in the egg, feeding larval, and adult stages, but low in the molting, wandering larval, and pupal stages of development. In a tissue comparison of fifth instar P. interpunctella, grp78 level was higher in the gut than in the integument or fat bodies. Grp78 level decreased greatly when fifth-instar larvae were starved for 48 h, but recovered within 3–6 h after re-feeding. Our data suggest that grp78 is highly associated with dietary energy conditions during development and may play an important role in the nutritional physiology of insects.     

Sampling of Bemisia tabaci adults using a pre-programmed autonomous pest control robot

An autonomous robot (Cabbot) was built to control insect pests in a plastic greenhouse and utilized to sample adult whiteflies (Bemisia tabaci) on paprika plants (Capsicum annum var. angulosum). To accomplish this, a sampling device consisting of an air compressor for pest agitation, a sticky trap (100 mm × 150 mm) and an image processing system for pest identification were installed on the Cabbot. The sampling precision of the Cabbot (D = 0.16) was higher than that of the sticky trap (D = 0.19) when sampling of adult white flies was conducted in caged pots. The Cabbot could also collect a substantial number of individuals within a short duration (3 minutes). The collection efficiency (i.e., percent of samples collected at least n (1 in this case) individuals to the total sample number) of insects by the Cabbot was markedly high at low population size, showing approximately 30% when the population size was ≤ 16 individuals per plant. The sampling precision and collection efficiency suggested that the Cabbot is effective in local, short-term sampling and could be used for early warning of pest occurrences.     

Advances in fundamental and applied studies in China of fungal biocontrol agents for use against arthropod pests

Entomopathogenic fungi, such as Beauveria bassiana and Metarhizium anisopliae, are environmentally friendly biocontrol agents (BCAs) against various arthropod pests. We provide an overview to the past-decade advances in fungal BCA research and application in China. Since 1960s, fungal BCAs have been mass-produced for application and at present, thousands of tons of their formulations are annually applied to control forest, agricultural, greenhouse and grassland insect pests throughout the country. Apart from technical advances in mass production, formulation and application of fungal BCAs, basic studies on the genomics, molecular biology, genetic engineering and population genetics of fungal entomopathogens have rapidly progressed in the past few years in China. The completed genomic studies of M. anisopliae, Metarhizium acridum, B. bassiana and Cordyceps militaris provide profound insights into crucial gene functions, fungal pathogenesis, host–pathogen interactions and mechanisms involved in fungal sexuality. New knowledge gained from the basic studies has been applied to improve fungal virulence and stress tolerance for developing more efficacious and field-persistent mycoinsecticides by means of microbial biotechnology, such as genetic engineering. To alleviate environmental safety concerns, more efforts are needed to generate new data not only on the effects of engineered BCAs on target and non-target arthropods but also on their potential effects on gene flow and genetic recombination before field release.