Screening of entomopathogenic fungi against the European spruce bark beetle,Dendroctonus micans (Coleoptera: Scolytidae)

The European spruce bark beetle, Dendroctonus micans Kugelann (Coleoptera: Scolytidae), is one of the most serious destructive pests of oriental spruce (Picea orientalis L.). In order to find an effective biocontrol agent against this pest, we determined the effectiveness of entomopathogenic fungi against D. micans. Virulence of nine highly pathogenic strains including Beauveria bassiana (2), Beauveria cf. bassiana (2), Metarhizium anisopliae (2), Metarhizium sp. (1), Isaria fumosorosea (1) and Evlachovaea sp. (1) was evaluated on D. micans larvae and adults under laboratory conditions. Mortality values for both larvae and adults ranged from 83 to 100% and from 23 to 100%, respectively. Larvae were more susceptible to fungi than adults (P<0.05). Based on screening tests, B. cf. bassiana isolate KTU-53 was found the most effective isolate. LC₅₀ values were calculated as 1.77×10⁴ and 2.65×10⁴ conidia mL^?1 for isolate KTU-53 against larvae and adults, respectively. Consequently, B. cf. bassiana isolate KTU-53 appears to be the most promising microbial control agent for biocontrol of D. micans.     

Molecular characterization,virulence and horizontal transmission of Beauveria pseudobassiana from Dendroctonus micans (Kug.) (Coleoptera: Curculionidae)

The great spruce bark beetle, Dendroctonus micans (Kugelann) (Coleoptera: Curculionidae), has been a potential threat for Turkey and the entire Eurasian spruce forests for many years. Control strategies which have been applied so far are still insufficient to prevent its damage. A previous study has shown that a Beauveria isolate (ARSEF 9271) proved to be an efficient microbial control agent against the great spruce bark beetle. In this study, this isolate was identified as B. pseudobassiana based on the partial sequence of EF1‐α and ITS sequence. A conidial suspension (1 × 10⁸/ml) of this fungus caused 100% mortality on both larvae and adults of D. micans within 5 and 6 days, respectively. Also, it caused 100% mycosis value on both larvae and adults. Mortality values of horizontal transmission experiments between larvae and adults which were contaminated with 1 × 10⁶/ml spore suspension at 25%, 50%, 75% and 100% rates were determined as 100% after 15 days at 20°C under the laboratory conditions. We also determined the decrease of the damage in spruce wood block (15 × 25 cm) when the contamination rate of the larvae was increased. Our results indicate that B. pseudobassiana ARSEF 9271 seems to be a very promising biocontrol agent against D. micans.     

Isolation and virulence of entomopathogenic fungi against the great spruce bark beetle,Dendroctonus micans (Kugelann) (Coleoptera: Scolytidae)

Twelve fungal strains including Lecanicillium muscarium (Petch.) Zare and Gams, Isaria farinosa (Holmsk.) Fr., Fusarium sp., Beauveria bassiana Sensu Lato and Beauveria sp. were isolated from larvae and adults of D. micans. In addition, virulence of these isolates against this pest was determined. Conidia suspensions of 1×10⁶ conidia mL^–1 were applied to larvae and adults. The highest mortality and mycosis for larvae were obtained from isolate ARSEF 9271 (Beauveria bassiana) with 90% mortality and mycosis within 10 days. ARSEF 9271 also produced 93% mortality and mycosis in adults. On the other hand, the highest mortality and mycosis for adults were obtained with isolate ARSEF 9272 (Beauveria sp.), with 100% mortality and 80% mycosis within 10 days. These results indicate that isolates ARSEF 9271 and ARSEF 9272 seem to be the most promising potential fungal biocontrol agents against D. micans.     

Exotic ladybirds for biological control of herbivorous insects – a review

Since the late 19th century, exotic ladybirds (Coleoptera: Coccinellidae) have been used extensively for suppressing herbivorous insects of economic importance. In recent decades, the introduction of non‐native biological control (BC) agents has been greatly limited due to the awareness of the potential non‐target effects of introductions. Nonetheless, recent episodes of biological invasions of economically important pests have raised the need to carefully consider whether the expected benefits of pest control go beyond the possible environmental risks of introduction. To better understand the factors that contributed to successful BC programs, here we review the literature behind classical and augmentative BC using exotic ladybirds. Additionally, by means of case studies, we discuss the BC efficacy of selected exotic species, e.g., Coccinella septempunctata L., Harmonia axyridis (Pallas), and Hippodamia variegata (Goeze), and their position within the communities of predators in the introduced areas of USA, Canada, and Chile. In Europe, much of the research on exotic ladybirds has been conducted on the undesired impact of H. axyridis. Therefore, we summarize the risk assessment data for this species and review the field research investigating the ecological impact on European aphidophagous predators. According to the BIOCAT database of classical BC programs, 212 ladybird species belonging to 68 genera have been released in about 130 years of BC activity, with 14.6% of introductions having resulted in partial, substantial, or complete control of the target pest. However, because post‐release evaluation of establishment and BC success has not always been conducted, this rate could underestimate the successful cases. Among other factors, ladybird establishment and pest suppression mostly depend on (1) intrinsic factors, i.e., high voracity, synchronized predator‐prey life cycle, and high dispersal ability, and (2) extrinsic factors, i.e., adaptability to the new environment and landscape composition. This review contributes to improved understanding of ladybirds as exotic BC agents.     

AM真菌在植物病虫害生物防治中的作用机制

丛枝菌根(Arbuscular Mycorrhizae,AM)真菌是一类广泛分布于土壤生态系统中的有益微生物,能与大约80%的陆生高等植物形成共生体。由土传病原物侵染引起的土传病害被植物病理学界认定为最难防治的病害之一。研究表明,AM真菌能够拮抗由真菌、线虫、细菌等病原体引起的土传性植物病害,诱导宿主植物增强对病虫害的耐/抗病性。当前,利用AM真菌开展病虫害的生物防治已经引起生态学家和植物病理学家的广泛关注。基于此,围绕AM真菌在植物病虫害生物防治中的最新研究进展,从AM真菌改变植物根系形态结构、调节次生代谢产物的合成、改善植物根际微环境、与病原微生物直接竞争入侵位点和营养分配、诱导植株体内抗病防御体系的形成等角度,探究AM真菌在植物病虫害防治中的作用机理,以期为利用AM真菌开展植物病虫害的生物防治提供理论依据,并对本领域未来的发展方向和应用前景进行展望。     

Reproductive isolation and environmental adaptation shape the phylogeography of mountain pine beetle (Dendroctonus ponderosae)

Chromosomal rearrangement can be an important mechanism driving population differentiation and incipient speciation. In the mountain pine beetle (MPB, Dendroctonus ponderosae), deletions on the Y chromosome that are polymorphic among populations are associated with reproductive incompatibility. Here, we used RAD sequencing across the entire MPB range in western North America to reveal the extent of the phylogeographic differences between Y haplotypes compared to autosomal and X‐linked loci. Clustering and geneflow analyses revealed three distinct Y haplogroups geographically positioned within and on either side of the Great Basin Desert. Despite close geographic proximity between populations on the boundaries of each Y haplogroup, there was extremely low Y haplogroup mixing among populations, and gene flow on the autosomes was reduced across Y haplogroup boundaries. These results are consistent with a previous study suggesting that independent degradation of a recently evolved neo‐Y chromosome in previously isolated populations causes male sterility or inviability among Y haplotype lineages. Phylogeographic results supported historic contraction of MPB into three separate Pleistocene glacial refugia followed by postglacial range expansion and secondary contact. Distinct sets of SNPs were statistically associated with environmental data among the most genetically distinct sets of geographic populations. This finding suggests that the process of adaptation to local climatic conditions is influenced by population genetic structure, with evidence for largely independent evolution in the most genetically isolated Y haplogroup.     

Evaluation of Beauveria bassiana (Hyphomycetes) isolates as potential agents for control of Dendroctonus valens

Abstract The red turpentine beetle (RTB), Dendroctonus valens LeConte, as a destructive invasive pest, has become one of the most economically important forest pest in China. Effective control measures are desperately needed. Entomopathogenic fungi, such as Beauveria bassiana, have shown great potential for the management of some bark beetle species. In this study, 12 isolates of B. bassiana from bark beetle were examined for biological characteristics and virulence, to assess their potential as biocontrol agents for RTB. There were significant differences (at P= 0.05) in colony growth rate, conidial yield, conidial germination, tolerance to UV light and extracellular proteases activity among the tested B. bassiana isolates. Isolates, including Bb1801, Bb1906, Bb789 and Bb773, exhibited the best characteristics, because they have faster hyphal growth rate, higher spore production and faster spore germination, higher UV tolerance and protease (Pr1) production. The results of a pathogenicity test of B. bassiana on RTB larvae showed that most isolates of B. bassiana have demonstrated high efficacy and the highest virulent isolate was Bb1801, which killed 100% of the treated insects and had a median lethal time (LT₅₀) of 4.60 days at a concentration of 1×10⁷ conidia/mL. Therefore, isolate Bb1801 has a great potential for sustainable control of RTB in the forest. The correlation between biological characteristics and virulence of the fungal isolates is discussed and the possibility of combination of entomopathogenic fungi with semiochemicals, as one of the promising strategy for RTB control, is considered.     

Susceptibility of the tobacco whitefly,Bemisia tabaci (Hemiptera: Aleyrodidae) biotype Q to entomopathogenic fungi

Recently, the Q biotype of tobacco whitefly has been recognized as the most hazardous strain of Bemisia tabaci worldwide because of increased resistance to some insecticide groups requiring alternative strategies for its control. We studied the susceptibility of this biotype of B. tabaci to 21 isolates of Beauveria bassiana, three isolates of Isaria fumosorosea, one isolate of I. cateni, three isolates of Lecanicillium lecanii, one isolate of L. attenuatum, and one isolate of Aschersonia aleyrodis. These isolates were evaluated on pruned eggplant seedlings, at a concentration of 10⁸ conidia/mL (deposited at 6000±586 conidia mm^?2). The mortality based on mycosis varied from 18 to 97% after 6 days. Isaria fumosorosea isolate Pf04, B. bassiana isolates Bb06, Bb12, and L. lecanii L14 were found the most effective. Furthermore, five isolates were chosen for concentration–mortality response assays and compared to B. bassiana GHA as a standard. The numbers of nymphs infected by fungi were correlated with the spore concentration. L. lecanii L14 and I. fumosorosea Pf04 had the shortest LT₅₀ at 3.5 and 3.3 days at 6000±586 conidia mm^?2. Mortality declined and LT₅₀ values were longer as the concentration of conidia was reduced. The LD₅₀ values were calculated as 87, 147, 191, 263, and 269 conidia mm^?2 for isolates L14, GHA, AS1260, Bb13, and Pf04, respectively. These results indicated that the Q biotype of sweetpotato whitefly was susceptible to the five isolates of entomopathogenic fungi and these isolates have potential to be developed as microbial pesticides for whitefly control.     

Potential biological control of Erwinia tracheiphila by internal alimentary canal interactions in Acalymma vittatum with Pseudomonas fluorescens

Aims

We aim to determine if Pseudomonas fluorescens is a viable biological control for Erwinia tracheiphila within the insect vector, Acalymma vittatum.

Methods and Results

Pseudomonas fluorescens secreted fluorescein and inhibited growth of E. tracheiphila in disc diffusion assays. To determine if this antagonism was conserved within the insect vector, we performed in vivo assays by orally injecting beetles with bacterial treatments and fluorescent in situ hybridization to determine bacterial presence within the alimentary canal.

Conclusions

Pseudomonas fluorescens inhibited the growth of E. tracheiphila on a nutrient‐limiting medium. In situ experiments demonstrated that P. fluorescens is maintained within the alimentary canal of the beetle for at least 4 days, and co‐occurred with E. tracheiphila. When beetles were first presented with Pseudomonas and then challenged with E. tracheiphila, E. tracheiphila was not recovered via FISH after 4 days. These data suggest that P. fluorescens has potential as a biological control agent to limit E. tracheiphila within the insect vector.

Significance and Impact of the Study

This is a novel approach for controlling E. tracheiphila that has the potential to decrease reliance on insecticides, providing a safer environment for pollinators and growers.     

Properties of capsaicinoids for the control of fungi and oomycetes pathogenic to pepper

Capsaicinoids are pungent compounds found in pepper (Capsicum spp.) fruits. Capsaicin showed antimicrobial activity in plate assays against seven isolates of five species of fungi and nine isolates of two species of oomycetes. The general trend was that oomycetes were more inhibited than fungi. Assays of capsaicin biosynthetic precursors suggest that the lateral chain of capsaicinoids has more inhibitory activity than the phenolic part. In planta tests of capsaicinoids (capsaicin and N‐vanillylnonanamide) applied to the roots demonstrated that these compounds conferred protection against the pathogenic fungus Verticillium dahliae and induced both chitinase activity and expression of several defence‐related genes, such as CASC1, CACHI2 and CABGLU. N‐Vanillylnonanamide infiltrated into cotyledons confers systemic protection to the upper leaves of pepper against the fungal pathogen Botrytis cinerea. In wild‐type tomato plants such cotyledon infiltration has no protective effect, but is effective in the Never‐ripe tomato mutant impaired in ethylene response. A similar effect was observed in tomato after salicylic acid infiltration.     

Interaction of acid exudates in chickpea with biological activity of Bacillus thuringiensis towards Helicoverpa armigera

The gram pod borer, Helicoverpa armigera, is one of the most important constraints to chickpea production. High acidity of chickpea exudates is associated with resistance to pod borer, H. armigera; however, acidic exudates in chickpea might influence the biological activity of the bacterium, Bacillus thuringiensis (Bt), applied as a foliar spray or deployed in transgenic plants for controlling H. armigera. Therefore, studies were undertaken to evaluate the biological activity of Bt towards H. armigera on chickpea genotypes with different amounts of organic acids. Significantly lower leaf feeding, larval survival and larval weights were observed on ICC 506EB, followed by C 235, and ICCV 10 across Bt concentrations. Leaf feeding by the larvae and larval survival and weights decreased with an increase in Bt concentration. However, rate of decrease in leaf feeding and larval survival and weights with an increase in Bt concentration was greater on L 550 and ICCV 10 than on the resistant check, ICC 506EB, suggesting that factors in the resistant genotypes, particularly the acid exudates, resulted in lower levels of biological activity of Bt possibly because of antifeedant effects of the acid exudates. Antifeedant effects of acid exudates reduced food consumption and hence might reduce the efficacy of Bt sprays on insect‐resistant chickpea genotypes or Bt‐transgenic chickpeas, although the combined effect of plant resistance based on organic acids, and Bt had a greater effect on survival and development of H. armigera than Bt alone.     

Susceptibility of Chrysochus auratus,a natural enemy of spreading dogbane,to insecticides used in wild blueberry production

Insect pest management in wild blueberry (Vaccinium angustifolium Aiton) usually involves insecticidal sprays, which may have detrimental effects on non‐target beneficial insects. Dogbane beetle (Chrysochus auratus Fabricius) (Coleoptera: Chrysomelidae) feeds almost exclusively on spreading dogbane (Apocynum androsaemifolium L.), an increasing weed problem in wild blueberry production. Because C. auratus is an important natural enemy of spreading dogbane, we assessed its susceptibility to several insecticides it may be exposed to during insect pest management. In laboratory bioassays, we found adult dogbane beetles were highly susceptible to field rates of phosmet (Imidan) and acetamiprid (Assail) by direct topical contact and ingestion of treated foliage, whereas no mortality was seen with spirotetramat (Movento) and chlorantraniliprole (Altacor). Topical applications of spinetoram (Delegate) did not cause significant mortality of beetles, but high mortality to beetles was found when they ingested spinetoram‐treated foliage. The results suggest that while some insecticides used in blueberry management will be hazardous to C. auratus, options are available that will cause little harm to this natural enemy.     

Occurrence of invertebrate-pathogenic fungi in a Cerrado ecosystem in Central Brazil

Occurrence of invertebrate-pathogenic fungi in a protected area of the Cerrado region of Brazil is reported. Fungi were baited with triatomines, ticks, aquatic snails or mosquito larvae from substrates or collected from infected insects. The findings underscore the importance to preserve these fungi and to investigate their potential for vector control.     

Selection of fungi for the control of Musca domestica in aviaries

Musca domestica is a major problem in poultry production where management has relied mostly on pesticides, which eventually have led to the development of widespread resistance in insect populations and environmental contamination. In this study, we explored the use of entomopathogenic fungi for the control of houseflies in Brazil. A total of 10 isolates of different fungal pathogens were tested on the larval stages of M. domestica, which were originally derived from a commercial aviary. Among the test fungi, Metarhizium anisopliae (sensu stricto) CG46 and CG30 were the most virulent isolates, causing up to 60% mortality at day 10, but only CG46 was selected for a field trial as it attained higher sporulation on larval cadavers. A commercial product based on the M. anisopliae isolate ESALQ-1037 (Metarril®) was also field-tested using standard treatment procedures. After spraying both fungi in the aviary manure, there was a significant reduction (twofold lower) in adult density of M. domestica captured per trap compared to the control shed. Therefore, our results indicate that M. anisopliae is a promising biological control agent for M. domestica larvae, but new strategies for fungal application and appropriate formulation need to be developed to improve its effectiveness in poultry environments.     

Isolation and characterization of microsatellite loci from the entomopathogenic fungus Beauveria bassiana (Ascomycota: Hypocreales)

Beauveria bassiana, an entomogenous fungus used for the biological control of pest insects, comprises a globally‐distributed species complex of regionally endemic lineages. In order to study the population genetics of B. bassiana, detail species boundaries, conduct ecological studies of natural populations and track fates of experimentally‐released strains, sensitive genetic markers are required. We describe the isolation and characterization of eight microsatellite loci that amplify successfully from strains representative of the phylogenetic diversity in the B. bassiana complex.     

Intercropping oilseed rape as a potential relay crop for enhancing the biological control of green peach aphids and aphid‐transmitted virus diseases

Tobacco viruses transmitted by green peach aphids, Myzus persicae (Sulzer) (Hemiptera: Aphididae), cause severe disease in flue‐cured tobacco, Nicotiana tabacum L. (Solanaceae), in China and throughout the world. Field experiments were conducted in 2016 and 2017 in Longyan City, Fujian Province, China, to determine whether M. persicae and aphid‐transmitted virus diseases are affected by intercropping of oilseed rape, Brassica napus L. (Brassicaceae), in tobacco fields. The results showed that, compared with those in monocultured fields, the densities of M. persicae and winged aphids in intercropped fields significantly decreased in both 2016 and 2017. In particular, the appearance of winged aphids was delayed by ca. 7 days. Moreover, the densities of Aphidius gifuensis Ashmead (Hymenoptera: Aphidiidae), a parasitoid of the aphid, significantly increased in 2016 and 2017. Accordingly, the incidence rates of aphid‐transmitted virus diseases (those caused by the cucumber mosaic virus, potato virus Y, and tobacco etch virus) significantly decreased in the intercropped fields in 2016 and 2017. Tobacco yields and monetary value significantly increased in 2016 (by 10–25 and 14–29%, respectively) and 2017 (by 17–22 and 22–34%, respectively). Consequently, our results suggest that intercropping oilseed rape in tobacco fields is a good approach to regulating and controlling aphids and tobacco mosaic viruses, for example potyvirus, and this intercropping can help control aphid‐transmitted virus diseases in tobacco.