SCREENING THE ABILITY TO CONTROL MESOMORPHUS VILLIGER (BLACK BEAN BEETLE) OF SIX METARHIZIUM ANISOPLIAE STRAINS ISOLATED IN BINH DUONG, VIET NAM

Three types of bio-preparations of six different Metarhizium anisopliae strains (Ma-SD, Ma-SAT, Ma-ST, Ma-RS, Ma-RN, and Ma-RM) isolated from soil in Binh Dương province, Viet Nam, including conidia, LIMs and MIXs, were evaluated the acaricidal effects on Mesomorphus villager (Black bean beetle). The results of conidia studies showed the high efficacies of Ma-SAT and Ma-ST at 98.64 ± 1.25 percent and 95.23 ± 3.15 percent, in turn. The times to kill half of the studied beetles were observed from the 9th day to the 12th day of the 15-day study process seemed indifferent and late, also without signs of mycosis at the end of the studies. LIMs had low efficacies in the studies, though the LIM of Ma-SAT continued to perform the efficacy at 57.14 ± 3.45 percent among the studied groups after the 15-day study process, moreover, its LIM was the only one killing half of the beetles on day 13th of the study process. The efficacies of MIXs were all higher than 91 percent, among them, Ma-ST, Ma-SAT, and Ma-RS showed their outstanding performance at 96.94 ± 2.49, 98.08 ± 1.21, 98.18 ± 1.38, respectively. Interestingly, all strains were observed to kill half of the studied beetles on day 5th of study time, the soonest one was recorded from the Ma-SAT experiment on day 3rd.

How the seed coat affects the mother’s oviposition preference and larval performance in the bean beetle (Acanthoscelides obtectus, Coleoptera: Chrysomelidae, Bruchinae) in leguminous species

Background The host specificity and host range of the dry bean beetle, Acanthoscelides obtectus (Coleoptera: Chrysomelidae, Bruchinae), a seed predator of beans, is poorly known. In addition, the female oviposition preference and larval performance relationship is complicated by the respective importance of seed coat and cotyledon, because, paradoxically, females lay eggs on the basis of stimuli of the seed coat alone, without directly being able to assess the quality of the cotyledon’s suitability for larval development. Conversely, the thickness of seed coat may prevent first instar larvae from entering the seeds, even if cotyledons are suitable for development. Methods The seeds of 62 leguminous species and 75 cultivars and accessions occurring in Hungary were evaluated for preference-performance relations. The preference of female bean beetles for seeds was measured in no-choice egg-laying tests. The ability of first instar larvae to overcome the seed coat as a physical barrier was tested with intact seed coat, while pre-drilled seed coats allowed the larvae to assess the suitability of cotyledon for development. The number of emerging adults was recorded. The thickness of seed coats and the weight of seeds were measured. Nonparametric tests and logistic regression were used for the statistical analyses of data and effect sizes were also calculated. Results Seeds of 18 leguminous species (35% of them Lathyrus) supported larval development to adults if the seed coat was pre-drilled; however, only nine leguminous species supported development to adults if the seed coat was intact. Seed coat thickness beyond a critical threshold of 0.1 mm strongly influenced survival of first instar larvae. There was no overall positive correlation between oviposition preference and larval performance, except for 16 so-called acceptable non-hosts (Kendall’s τ = 0.3088). A. obtectus females also showed an ovipositional hierarchy of legume species even in no-choice tests. Conclusions The results suggest that whereas the use of some acceptable non-host species by the A. obtectus is possible in seed stores, the same is unlikely under outdoor conditions, where the recognition of a diverse set of seed pod-related compounds would be necessary to induce egg-laying.

Symbiont genomic features and localization in the bean beetle, Callosobruchus maculatus

A pervasive pest of stored leguminous products, the bean beetle (Coleoptera: Chrysomelidae: Callosobruchus maculatus) associates with a simple bacterial community during adulthood. Despite its economic importance, little is known about the compositional stability, heritability, localization, and metabolic potential of the bacterial symbionts of C. maculatus. In this study, we applied community profiling using 16S rRNA gene sequencing to reveal a highly conserved bacterial assembly shared between larvae and adults. Dominated by Firmicutes and Proteobacteria, this community is localized extracellularly along the epithelial lining of the bean beetle’s digestive tract. Our analysis revealed only one species, Staphylococcus gallinarum (phylum Firmicutes), is shared across all developmental stages. Isolation and whole genome sequencing of S. gallinarum from the beetle gut yielded a circular chromosome (2.8 Mb) and one plasmid (45 kb). The strain encoded complete biosynthetic pathways for the production of B vitamins and amino acids, including tyrosine, which is increasingly recognized as an important symbiont-supplemented precursor for cuticle biosynthesis in beetles. A CAZyme search revealed the genome codes for a number of carbohydrate active enzymes, reflecting the nutritional ecology of their herbivorous host. The ontogenic conservation of the gut microbiota in the bean beetle - featuring a ‘core’ community composed of S. gallinarum - may be indicative of an adaptive role for the host. In clarifying symbiont localization and metabolic potential, we further our understanding and study of a costly pest of stored products. IMPORTANCE From supplementing essential nutrients to detoxifying plant secondary metabolites and insecticides, bacterial symbionts are a key source of adaptations for herbivorous insect pests. Despite the pervasiveness and geographical range of the bean beetle Callosobruchus maculatus, the role of microbial symbioses in its natural history remains understudied. Here, we demonstrate that the bean beetle harbors a simple gut bacterial community that is stable throughout development. This community localizes along the insect’s digestive tract and is largely dominated by Staphylococcus gallinarum. In elucidating symbiont metabolic potential, we highlight its possible adaptive significance for a widespread agricultural pest.

Comparative Efficacy of Common Active Ingredients in Organic Insecticides Against Difficult to Control Insect Pests

There exists a lack of control efficacy information to enable decision-making about which organic insecticide product works best for a given insect pest. Here, we summarize results of 153 field trials on the control efficacy of common active ingredients in organic insecticides against 12 groups of the most difficult to control insect pests. These trials evaluated primarily the organic products Entrust (spinosad), Azera (pyrethrin and azadirachtin), PyGanic (pyrethrin) and Neemix (azadirachtin), which reduced pest infestations by an overall 73.9%, 61.7%, 48.6% and 46.1% respectively, averaged across all trials. Entrust was the most effective control option for many insect pests, particularly providing >75% control of flea beetles, Colorado potato beetle, cabbageworms and alfalfa weevil, but was relatively ineffective against true bugs and aphids. Azera provided >75% control of green peach aphid, flea beetles, Japanese beetle, Mexican bean beetle, potato leafhopper and cabbageworms. PyGanic was less effective than Entrust and Azera but still provided >75% control of green peach aphid, flea beetles and potato leafhopper. The growth inhibition effects of azadirachtin in Neemix were particularly effective against larvae of Mexican bean beetle and Colorado potato beetle but was generally less effective in trials with insect infestations consisting mainly of adult stages. Those insect pests that were particularly difficult to control included thrips, stinkbugs, cucumber beetles and fruitworms. Several caveats pertaining to the application of the results are discussed.