The Impact of Drought and Vascular-Inhabiting Pathogen Invasion inPinus taedaHealth

The complex interaction of various biotic and abiotic factors may put the overall stand health ofPinusspp. at risk. A study was designed to determine the combined impact of drought and vascular-inhabiting fungi (Leptographium terebrantisandGrosmannia huntii) inPinus taeda. Seedlings from twoP. taedafamilies were planted and watering treatments, (i) normal watering, (ii) moderate drought, and (iii) severe drought, were applied. One month following the initiation of watering treatments, seedling stems were artificially inoculated withL. terebrantisandG. huntii. Drought and fungal interaction significantly affected lesion length/seedling height, occlusion length/seedling height, and seedling fine root biomass.Leptographium terebrantiswas more pathogenic under moderate and severe drought than normal watering condition, whereas the pathogenicity ofG. huntiiremains unaltered. The susceptibility of the families to vascular-inhabiting fungi remained the same under different watering treatments. Drought and specific vascular-inhabiting fungi may negatively impactP. taedastand health.

Mutual interactions between an invasive bark beetle and its associated fungi

Interactions between invasive insects and their fungal associates have important effects on the behavior, reproductive success, population dynamics and evolution of the organisms involved. The red turpentine beetle (RTB), Dendroctonus valens LeConte (Coleoptera: Scolytinae), an invasive forest pest in China, is closely associated with fungi. By carrying fungi on specialized structures in the exoskeleton, RTB inoculates fungi in the phloem of pines (when females dig galleries for egg laying and when males join them for mating). After eggs hatch, larvae gregariously feed on the phloem colonized by the fungi. We examined the effects of five isolates of RTB associated fungi (two from North America, Leptographium terebrantis and L. procerum, and three from China, Ophiostoma minus, L. sinoprocerum and L. procerum) on larval feeding activity, development and mortality. We also studied the effects of volatile chemicals produced in the beetle hindgut on fungal growth. Ophiostoma minus impaired feeding activity and reduced weight in RTB larvae. Leptographium sinoprocerum, L. terebrantis and L. procerum did not dramatically influence larval feeding and development compared to fungi-free controls. Larval mortality was not influenced by any of the tested fungi. Hindgut volatiles of RTB larvae, verbenol, myrtenol and myrtenal, inhibited growth rate of all the fungi. Our results not only show that D. valens associated fungus, O. minus, can be detrimental to its larvae; but, most importantly, they also show that these notorious beetles have an outstanding adaptive response evidenced by the ability to produce volatiles that inhibit growth of harmful fungus.

Fungi vectored by the introduced bark beetle Tomicus piniperda in Ontario, Canada, and comments on the taxonomy of Leptographium lundbergii, Leptographium terebrantis, Leptographium truncatum, and Leptographium wingfieldii

Fungi isolated from Tomicus piniperda (L.) galleries in infected trap logs, standing trees, and directly from insects were identified using morphological features and molecular data obtained from the mitochondrial and nuclear DNA region. Identified strains represented Leptographium wingfieldii Morelet, Leptographium procerum (Kendr.) Wingf., Leptographium lundbergii Lag. & Melin sensu Jacobs & Wingfield, Ophiostoma ips (Rumb.) Nannf., Ophiostoma minus (Hedg.) H. & P. Syd., and Sphaeropsis sapinea sensu lato. Leptographium wingfieldii is believed to be a potentially pathogenic introduced fungus, but sequence data suggest a possible connection between it and the teleomorph of Ophiostoma aureum (Robinson-Jeffrey & Davids.) T.C. Harrington (reported from British Columbia and the western United States). Our data also show that the ex-type culture of Leptographium terebrantis Barras & Perry, a species very similar morphologically to L. wingfieldii, also grouped with L. wingfieldii. We also identified strains of Leptographium truncatum (Wingf. & Marasas) Wingf.; this species has been synonymized with L. lundbergii, but our data indicate that these are distinct species, and therefore, the name L. truncatum should be reinstated. We also report the extended presence of L. procerum in Ontario. Previously viewed as a “southern” species frequently associated with pine-root decline diseases, it has been infrequently reported from New York state and but once each from Ontario and Quebec.

SURVIVAL AND DEVELOPMENT OF IPS PARACONFUSUS LANIER (COLEOPTERA: SCOLYTIDAE) REARED AXENICALLY AND WITH TREE-PATHOGENIC FUNGI VECTORED BY COHABITING DENDROCTONUS SPECIES

Survival and development of Ips paraconfusus Lanier larvae reared individually in intact Pinus ponderosa Laws. phloem without associated fungi and dietary supplements was demonstrated. Survival was reduced.in intact ponderosa pine phloem previously occupied by other larvae or by bluestaining fungi [i.e. Ophiostoma ips (Rumb.) vectored by I. paraconfusus, O. minus (Hedge.) H. & P. Syd. vectored by Dendroctonus brevicomis LeConte, O. clavigerum (Robins.-Jeff. & Davids.) vectored by D. ponderosae Hopkins, and Leptographium terebrantis Barras & Perry vectored by D. valens LeConte] compared with those reared without fungi or symbiotic yeasts. The highest proportion of larvae initiating tunnels and surviving to adult was observed for untreated eggs, and the lowest proportion occurred in the L. terebrantis treatment. Size was reduced and developmental rate was slower for larvae reared without fungi compared with larvae reared with associated fungi.Tunnels excavated by first- and second-instar larvae reared without associated fungi were longer than those excavated by larvae reared with associated fungi. The most frequent larval turnabouts occurred with larvae reared axenically and reared with Ips yeast and O. ips. The fewest occurred with larvae reared with Ips egg niche plugs and from untreated eggs. Females reared free of any fungi or with Penicillium or Aspergillus did not oviposit in surface-sterilized ponderosa pine logs. Naturally eclosed females from ponderosa pine logs in which they developed, laid eggs in these sterilized logs. Potential for a new association among bark beetles and fungi is discussed.