Induced defenses of loblolly pine, Pinus taeda: potential impact on Dendroctonus frontalis within-tree mortality

Loblolly pine (Pinus taeda L.) produces an induced defensive hypersensitive response in inner bark colonized by the southern pine beetle, Dendroctonus frontalis Zimm. (Coleoptera: Scolytidae), and its associated fungi. Adult beetles forced to colonize the induced response tissue in a laboratory study constructed galleries that were the same length as adults boring in normal phloem. However, each female laid fewer eggs in the induced tissue. Larval and pupal mortality were also higher in this tissue when compared to surrounding phloem. Beetles colonizing trees in response to pheromone baits constructed less gallery and laid fewer eggs in induced tissue than in surrounding normal phloem. These results suggest that the lesions produced by the induced defense system in conifers may not only contain the growth of fungi inoculated into trees during the attack phase of beetle colonization, but may also affect survival of bark beetle progeny.

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Résumé Une réaction hypersensible de défense a été induite dans les couches profondes de l'écorce de P. taeda colonisée par D. frontalis et le champignon qui lui est associé. Au laboratoire, des adultes, contraints de coloniser les tissus où une réaction hypersensible e été induite, ont foré des galeries de même longueur que celles creusées dans du phloème sain. Cependant les femelles ont pondu moins d'oeufs dans les tissus induits; les mortalités larvaires et nymphales étaient aussi plus fortes dans ce tissu que dans le phloème voisin. Les scolytes, ayant colonisé les arbres après attraction par des pièges à phéromones, forent moins de galeries et pondent moins d'oeufs dans le tissu induit que dans le phloème sain voisin. Ces résultats suggèrent que les lésions, provoquées par le système de défense induit des conifères, peuvent non seulement limiter la croissance du champignon inoculé dans l'arbre au cours de la colonisation des scolytes, mais aussi affecter la survie des descendants dans l'écorce.

     

斑痣盘菌科一新种——松生小鞋孢盘菌

本文报道在云南省昆明市华山松(Pinus armandi Franch.)上发现的斑痣盘菌科一新种,即松生小鞋孢盘菌(Soleella pinicola Y.R.Lin et W.Ren)。对该种作了拉丁文、汉文描述和图解。主模式标本保藏于安徽农学院林学系森林保护教研室。     

Effect of the Nematode Contortylenchus brevicomi on Gallery Construction and Fecundity of the Southern Pine Beetle

Field-collected Dendroctonus frontalis were reared in a controlled environment. Male-female beetle pairs retrieved from galleries 1, 2, or 5 wk after introduction into pine bolts were examined for nematode parasites. Data were obtained for each pair on gallery length, egg niche construction, egg viability, and progeny survival. In a separate study, beetle pairs were reared under laboratory conditions for 10 wk. The number of emerged adult progeny of each pair was recorded. Contortylenchus brevicomi, a nematode parasite, was found in 25% of all beetles that established galleries. After 2 and 3 wk, female beetles infected with the nematode had produced fewer eggs and shorter galleries than did uninfected females. Uninfected females mated with nematode-infected males showed similar trends, although the differences in the 2- and 3-wk tests were not significant. Progeny survival or egg viability was not affected by nematode parasitism of either parent beetle. Unikaryon minutum, a microsporidian parasite found in 65% of all colonizing beetles, had no effect on measured variables. The lower fecundity of beetles parasitized by C. brevicomi continued throughout the insect''s reproductive cycle. After 10 wk, nematode-infected beetle pairs produced fewer emerged adult progeny than did uninfected pairs.     

Sub‐lethal effects of monoterpenes on reproduction by mountain pine beetles

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cDNA cloning,expression, and enzymatic activity of a novel endogenous cellulase from the beetle Batocera horsfieldi

In this study, we report a novel cellulase [β-1,4-endoglucanase (EGase), EC 3.2.1.4] cDNA (Bh-EGase II) belonging to the glycoside hydrolase family (GHF) 45 from the beetle Batocera horsfieldi. The Bh-EGase II gene spans 720 bp and consists of a single exon coding for 239 amino acid residues. Bh-EGase II showed 93.72% protein sequence identity to Ag-EGase II from the beetle Apriona germari. The GHF 45 catalytic site is conserved in Bh-EGase II. Bh-EGase II has three putative N-glycosylation sites at 56–58 (N–K–S), 99–101 (N–S–T), and 237–239 (N–Y–S), respectively. The cDNA encoding Bh-EGase II was expressed in baculovirus-infected insect BmN cells and Bombyx mori larvae. Recombinant Bh-EGase II from BmN cells and larval hemolymph had an enzymatic activity of approximately 928 U/mg. The enzymatic catalysis of recombinant Bh-EGase II showed the highest activity at 50 °C and pH 6.0.     

Morphological variation associated with dispersal capacity in a tree‐killing bark beetle Dendroctonus ponderosae Hopkins

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Mutual mate choice by mountain pine beetles: size‐dependence but not size‐assortative mating

1. Mutual mate choice may be rare, occurring when both sexes invest heavily in reproduction, mating opportunities are abundant, and individuals differ in quality. 2. Mountain pine beetles, Dendroctonus ponderosae (Curculionidae: Scolytinae) appear to meet the conditions for mutual mate choice. We introduced males to females in breeding sites and observed the occurrence and speed of a male entering a female's gallery. We tested for consequences of mutual mate choice, namely condition‐dependent choosiness and assortative mating. 3. Males were more likely to enter a female's gallery when the gallery was in a smaller tree with less resin production and when the gallery was larger. Female body size and condition did not influence the probability of entry. Larger males were less likely to enter a gallery than were smaller males, probably because of size‐dependent choosiness rather than physical limitations. 4. Small males took longer to enter galleries of large females than of small females, whereas large males entered as quickly into galleries of large females as small females. This suggests size‐dependent choosiness by females. 5. No assortative mating by body size was detected, probably because males appeared to choose on the basis of female‐associated resources rather than on female traits.     

Measuring trap efficiency for bark beetles (Col., Scolytidae)

Abstract:  The relative efficiency of cylindrical, linear and cross-barrier traps for trapping bark beetles was investigated based on a theoretical model. Using this model, the effective trap interception area of each trap type was calculated and trap efficiency was defined as the ratio of the effective interception area to the trap surface area. The relative efficiencies of the three trap types were calculated as the ratios of their respective effective interception areas. Based on this approach, assuming random directional movement of dispersing beetles, the order of efficiency of the three trap types, from highest to lowest, was linear, cross-barrier and cylindrical. The expected ratios of trap catches based on the relative efficiencies of the three trap types were fitted to data from trapping experiments with the mountain pine beetle ( Dendroctonus ponderosae Hopkins). In general, there was large variation in trap catches among traps of the same type but the ratios of mean catches per trap conformed to the expected ratios. The results indicate that the model of trap efficiency could be used for designing efficient traps. The methods presented are amenable for assessing the efficiency of other trap designs.     

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.     

Multilocus species identification and fungal DNA barcoding: insights from blue stain fungal symbionts of the mountain pine beetle

There is strong community-wide interest in applying molecular techniques to fungal species delimitation and identification, but selection of a standardized region or regions of the genome has not been finalized. A single marker, the ribosomal DNA internal transcribed spacer region, has frequently been suggested as the standard for fungi. We used a group of closely related blue stain fungi associated with the mountain pine beetle (Dendroctonus ponderosae Hopkins) to examine the success of such single-locus species identification, comparing the internal transcribed spacer with four other nuclear markers. We demonstrate that single loci varied in their utility for identifying the six fungal species examined, while use of multiple loci was consistently successful. In a literature survey of 21 similar studies, individual loci were also highly variable in their ability to provide consistent species identifications and were less successful than multilocus diagnostics. Accurate species identification is the essence of any molecular diagnostic system, and this consideration should be central to locus selection. Moreover, our study and the literature survey demonstrate the value of using closely related species as the proving ground for developing a molecular identification system. We advocate use of a multilocus barcode approach that is similar to the practice employed by the plant barcode community, rather than reliance on a single locus.