Efficacy of Metarhizium anisopliae in controlling the two‐spotted spider mite Tetranychus urticae on common bean in screenhouse and field experiments

The efficacy of aqueous and emulsifiable formulations of the fungus Metarhizium anisopliae isolate ICIPE78 was evaluated on the population density of Tetranychus urticae infesting common bean plants under screenhouse and field conditions. Synthetic acaricide abamectin was included as a check. Bean plants were artificially infested with T. urticae and allowed to multiply. Three treatments were applied in the screenhouse and 1 treatment in field trials. Mite density was recorded 2 d before spraying and weekly postspraying. The number of pods per plant, number of seeds per pod, and the dry weight of seeds per plant were recorded only in the screenhouse trials. In both screenhouse and field trials, fungal formulations applied at the concentration of 10⁸ conidia/mL and the acaricide reduced the population density of mites as compared to the controls. There were significant differences in T. urticae population densities between the treatments at the various post‐spraying sampling dates. In the screenhouse, the mite densities were near zero from 3‐week postspraying in the treated leaves. At 4‐week postspraying, there were no more leaves in the untreated control (T1) and in the control water + Silwet‐L77 (T2). Fungal formulations were as effective as abamectin in reducing mite densities in both screenhouse and field experiments. There were significant differences in the production parameters during the 2 screenhouse trials, with fungal and abamectin treatments generally having the highest yield. Results of this study underline the potential of the M. anisopliae isolate ICIPE78 as an alternative to acaricides for T. urticae management.     

Enzymatic Activities of Allergen Extracts from Three Species of Dust Mites and Cockroaches Commonly Found in Korean Home

Allergen extracts from dust mites and cockroaches commonly found in Korean homes were used to evaluate their enzymatic activity as they are believed to influence allergenicity. Allergen extracts were prepared from 3 dust mite species (Dermatophagoides farinae, D. pteronyssinus, and Tyrophagus putrescentiae) and 3 cockroach species (Blattella germanica, Periplaneta americana, and P. fuliginosa) maintained in the Korea National Arthropods of Medical Importance Resource Bank. Proteins were extracted in PBS after homogenization using liquid nitrogen. The activities of various enzymes were investigated using the API Zym system. No significant difference in phosphatase, lipase, or glycosidase activity was observed among the 6 allergen extracts, but much difference was observed in protease activity. Protease activity was assessed in more detail by gelatin zymography and the EnzChek assay. Extract from T. putrescentiae showed the highest protease activity, followed by those of the cockroach extracts. Extracts from D. farinae and D. pteronyssinus showed only weak protease activity. Gelatinolytic activity was detected mainly in a 30-kDa protein in D. farinae, a 28-kDa protein in D. pteronyssinus, a > 26-kDa protein in T. putrescentiae, a > 20-kDa protein in B. germanica, and a > 23-kDa protein in P. americana and P. fuliginosa. The information on various enzymatic activities obtained in this study may be useful for future studies. In particular, the strong protease activity found in cockroach extracts could contribute to sensitization to cockroach allergens, which is known to be associated with the development of asthma.     

<Emphasis Type="Italic">Wolbachia</Emphasis>-induced cytoplasmic incompatibility in Japanese populations of <Emphasis Type="Italic">Tetranychus urticae</Emphasis> (Acari: Tetranychidae)

Intracellular bacteria of the genus Wolbachia (alpha Proteobacteria) induce cytoplasmic incompatibility (CI) in many arthropod species, including spider mites, but not all Wolbachia cause CI. In spider mites CI becomes apparent by a reduced egg hatchability and a lower daughter:son ratio: CI in haplodiploid organisms in general was expected to produce all-male offspring or a male-biased sex ratio without any death of eggs. In a previous study of Japanese populations of Tetranychus urticae, two out of three green-form populations tested were infected with non-CI Wolbachia strains, whereas none of six red-form populations harbored Wolbachia. As the survey of Wolbachia infection in T. urticae is still fragmentary in Japan, we checked Wolbachia infection in thirty green-form populations and 29 red-form populations collected from a wide range of Japanese islands. For Wolbachia-infected populations, we tested the effects of Wolbachia on the reproductive traits and determined the phylogenetic relationships of the different strains of Wolbachia. All but one green-form populations were infected with Wolbachia and all strains belonged to the subgroup Ori when the wsp gene was used to determine the phylogenetic relationships of different strains of Wolbachia. Six out of 29 red-form populations harbored Wolbachia and the infected strains belonged to the subgroups Ori and Bugs. Twenty-four of 29 infected green-form populations and five of six infected red-form populations induced CI among the hosts. Thus, CI-Wolbachia strains are widespread in Japan, and no geographical trend was observed in the CI-Wolbachia. Although three red-form populations harbored other intracellular bacteria Cardinium, they did not affect host reproduction.     

Antagonistic effects of the endophytic fungus Meira geulakonigii on the citrus rust mite Phyllocoptruta oleivora

AIMS: The fungus Meira geulakonigii has been shown to reduce populations of citrus rust mite (CRM; Phyllocoptruta oleivora) on citrus leaves and fruits, in both the field and laboratory. However, attempts to isolate the fungus from leaves and fruits have been unsuccessful. The aims of this study were therefore to determine whether M. geulakonigii is a citrus endophyte, and to assess possible mechanisms involved in its mite-antagonist activity. METHODS AND RESULTS: A quantitative real-time PCR and regular PCR approaches were developed to detect M. geulakonigii in both the field and laboratory. The fungus was detected throughout. Different methods revealed that M. geulakonigii is an endophyte, which colonizes both the peel of grapefruits. Applications of conidia protected the grapefruits against CRM, and fungal secretions extracted from growth media caused 100% CRM mortality. CONCLUSIONS: Meira geulakonigii is a beneficial endophyte of grapefruits that colonizes the fruit's peel, and protects it from CRM. SIGNIFICANCE AND IMPACT OF THE STUDY: Findings from this study demonstrate the endophytic nature of M. geulakonigii in its interaction with grapefruits. In addition, a molecular approach was developed to specifically detect the fungus inside the grapefruit peel. This approach can be used to assess the natural occurrence of M. geulakonigii in grapefruit.     

Molecular detection of various rickettsiae in mites (acari: trombiculidae) in southern Jeolla Province, Korea

This study revealed the presence of various rickettsial agents in mites from wild rodents collected in Southern Jeolla Province, Korea, by nested polymerase chain reaction (PCR) and sequence analysis of a partial citrate synthase and rickettsia outer membrane protein B genes. Rickettsial agents closely related to the Rickettsia species TwKM02, R. australis, and the Rickettsia species Cf15 were successfully identified in this study, for the first time in Korea, and R. japonica, R. akari, R. conorii, R. felis, and R. typhi were also detected, as previously described. The data presented in this paper extend knowledge on the geographic distribution of SFG rickettsiae in eastern Asia and it may necessary to consider the role of mites in rickettsial transmission.     

Assaying three new fungi against citrus mites in the laboratory,and a field trial

The Basidiomycotine fungi Meira geulakonigii, Meira argovae and Acaromyces ingoldii were assayed in the laboratory against five species of herbivorous mites: Phyllocoptruta oleivora (Eriophyidae), Panonychus citri, Eutetranychus orientalis, Tetranychus urticae and Tetranychus cinnabarinus (all four Tetranychidae). All fungi caused significantly high mortality rates (as compared to controls) after 14 days, some after 1 week. Phyllocoptruta oleivora was the most susceptible, showing >80% mortality even after 1 week. In a field trial, grapefruits sprayed either once a month or once a season with M. geulakonigii had significantly fewer P. oleivora and less damage than unsprayed fruit. These results suggest that M. geulakonigii may protect grapefruits against the injurious P. oleivora.     

Multiple host shifts by the emerging honeybee parasite,Varroa jacobsoni

Host shifts are a key mechanism of parasite evolution and responsible for the emergence of many economically important pathogens. Varroa destructor has been a major factor in global honeybee (Apis mellifera) declines since shifting hosts from the Asian honeybee (Apis cerana) > 50 years ago. Until recently, only two haplotypes of V. destructor (Korea and Japan) had successfully host shifted to A. mellifera. In 2008, the sister species V. jacobsoni was found for the first time parasitizing A. mellifera in Papua New Guinea (PNG). This recent host shift presents a serious threat to world apiculture but also provides the opportunity to examine host shifting in this system. We used 12 microsatellites to compare genetic variation of V. jacobsoni on A. mellifera in PNG with mites on A. cerana in both PNG and surrounding regions. We identified two distinct lineages of V. jacobsoni reproducing on A. mellifera in PNG. Our analysis indicated independent host shift events have occurred through small numbers of mites shifting from local A. cerana populations. Additional lineages were found in the neighbouring Papua and Solomon Islands that had partially host shifted to A. mellifera, that is producing immature offspring on drone brood only. These mites were likely in transition to full colonization of A. mellifera. Significant population structure between mites on the different hosts suggested host shifted V. jacobsoni populations may not still reproduce on A. cerana, although limited gene flow may exist. Our studies provide further insight into parasite host shift evolution and help characterize this new Varroa mite threat to A. mellifera worldwide.     

胡瓜钝绥螨对日光大棚茄子上烟粉虱的控制作用

为了评价胡瓜钝绥螨在我国日光大棚中对茄子上烟粉虱虱的控制作用。笔者研究了在24～34℃下胡瓜钝绥螨以烟粉为猎物时的发育历期,并在我国山东省寿光市的蔬菜基地上开展了利用胡瓜钝绥螨控制日光大棚茄子上烟粉虱的研究与应用。结果表明:胡瓜钝绥螨能够取食烟粉虱的卵、成虫、若虫及伪蛹;利用胡瓜钝绥螨能有效地控制烟粉虱成虫、卵、若虫种群数量的增长。根据胡瓜钝绥螨和烟粉虱的生物学特性,结合大棚茄子栽培过程中的环境条件,笔者提出了在日光大棚中应用胡瓜钝绥螨控制茄子上烟粉虱的策略:(1)在茄子的整个生长季节(250d)中需释放胡瓜钝绥螨4～6次,苗期每次每株释放5～10头,结果期每次每株释放20～40头;(2)释放胡瓜钝绥螨的生防区比常规化防区减少农药使用18次;(3)安装防虫网、适时释放胡瓜钝绥螨是生防成功之关键,生防区配合使用黄板效果更好。     

Climate change effects on walnut pests in California

Increasing temperatures are likely to impact ectothermic pests of fruits and nuts. This paper aims to assess changes to pest pressure in California's US$0.7 billion walnut industry due to recent historic and projected future temperature changes. For two past (1950 and 2000) and 18 future climate scenarios (2041–2060 and 2080–2099; each for three General Circulation Models and three greenhouse gas emissions scenarios), 100 years of hourly temperature were generated for 205 locations. Degree‐day models were used to project mean generation numbers for codling moth (Cydia pomonella L.), navel orangeworm (Amyelois transitella Walker), two‐spotted spider mite (Tetranychus urticae Koch), and European red mite (Panonychus ulmi Koch). In the Central Valley, the number of codling moth generations predicted for degree days accumulated between April 1 and October 1 rose from 2–4 in 1950 to 3–5 among all future scenarios. Generation numbers increased from 10–18 to 14–24 for two‐spotted spider mite, from 9–14 to 14–20 for European red mite, and from 2–4 to up to 5 for navel orangeworm. Overall pest pressure can thus be expected to increase substantially. Our study did not include the possibility of higher winter survival rates, leading to higher initial pest counts in spring, or of extended pest development times in the summer, factors that are likely to exacerbate future pest pressure. On the other hand, initiation of diapause may prevent an extension of the season length for arthropods, and higher incidence of heat death in summer may constrain pest population sizes. More information on the impact of climate change on complex agroecological food webs and on the response of pests to high temperatures is needed for improving the reliability of projections.