The Ambrosia Beetle Sueus niisimai (Scolytinae: Hyorrhynchini) is Associated with the Canker Disease Fungus Diatrypella japonica (Xylariales)

Ambrosia beetles in the subtribe Hyorrhynchini are one example of an entire ambrosia beetle lineage whose fungi have never been studied. Here, we identify one dominant fungus associated with a widespread Asian hyorrhynchine beetle Sueus niisimai. This fungus was consistently isolated from beetle galleries from multiple collections. Phylogenetic analyses of combined ITS rDNA and β-tubulin sequences identified the primary fungal symbiont as Diatrypella japonica Higuchi, Nikaido & Hattori (Diatrypaceae, Xylariales, Sordariomycetes), which was recently described as a pathogen of sycamore (Platanus spp.) in Japan. To assess the invasion potential of this beetle-fungus interaction into the U.S., we have investigated the pathogenicity of two D. japonica strains on four species of healthy landscape trees native to the southeastern United States. Only Shumard oak (Quercus shumardii) responded with lesions significantly greater than the control inoculations, but there was no observable dieback or tree mortality. Although disease symptoms were not as prominent as in previous studies of the same fungus in Japan, routine reisolation from the inoculation point suggests that this species is capable of colonizing healthy sapwood of several tree species. Our study shows that the geographical area of its distribution is broader in Asia and potentially includes many hosts of its polyphagous vector. We conclude that the Sueus-Diatrypella symbiosis has high invasion potential but low damage potential, at least on young trees during the growing season.

Mapeo del arbolado urbano con lidar aéreo

Los recientes avances en las tecnologías de sensores remotos han hecho posible que algunas características físicas de la vegetación sean estimadas con mayor rapidez y permiten distinguir las especies del arbolado urbano y analizar su distribución en el espacio y tiempo, lo cual resulta en mejoras notables de precisión cartográfica. En el presente trabajo se utilizaron datos de LIDAR aéreo para estimar la altura y el diámetro de copa de árboles individuales en un área urbana al sur de Monterrey a fin de diseñar un método eficiente para cartografiar el arbolado de las ciudades. Se usaron dos técnicas de extracción: 1) diseño de filtros semiautomatizados para los puntos asociados a la vegetación y 2) uso de líneas de contorno sobre un modelo digital de superficie. Los resultados se verificaron con la información de campo que se obtuvo durante el mismo periodo mediante el empleo de métodos tradicionales de medición forestal, lo que se realizó en 57.80 ha y se contabilizaron 2 575 árboles. El mapeo de las copas fue eficaz para 74.7 % de los individuos y se registró 6.4 % de error de medición en el geoposicionamiento e inventario. Se observó una eficacia similar entre el muestreo en campo y la nube de puntos de LIDAR aéreo (xy=0.70m; z=0.10 m), de acuerdo con el análisis de regresión lineal de alturas (R2= 0.885) y del ancho de copa (R2= 0.902). Las mejores estimaciones fueron en Quercus shumardii (95 %) y Quercus vaseyana (94 %).

Landscape Establishment of Woody Ornamentals Grown in Alternative Wood-Based Container Substrates

Due to concerns over future pine bark (PB) availability for container plant production, recent research has focused on evaluating suitable alternatives. For alternatives to be considered suitable substrate replacements, they must not only have desirable characteristics as a container substrate (e.g., adequate drainage, inert, pathogen free, etc.), but must also cause no negative fertility effects (e.g., nitrogen immobilization) following planting in the landscape. The study objective was to evaluate the landscape performance of three woody ornamentals grown in PB and in two alternative wood-based substrates, namely WholeTree (WT) and Clean Chip Residual (CCR). Crapemyrtle (Lagerstroemia indica × faurei ‘Acoma’), magnolia (Magnolia grandiflora ‘D.D. Blanchard’), and shumard oak (Quercus shumardii) were container grown in PB, WT, or CCR for an entire growing season prior to being planted into the landscape. Plants were grown in the landscape for two growing seasons. Data suggest that all species exhibited similar landscape performance when grown in WT or CCR compared to the PB standard. Therefore, the use of WT and CCR as alternative wood-based substrates for crapemyrtle, magnolia, and oak production may be acceptable from a landscape establishment standpoint.

Efficacy of Basal Girdling to Control Oak Wilt Fungal Mat Production in Texas Red Oak (Quercus buckleyi) in Central Texas

Woodlands dominated by Ashe juniper (Juniperus ashei) and oaks, including Texas red oak (Quercus buckleyi; synonyms: Quercus texana, Quercus shumardii var. texana), serve as breeding habitat for the endangered golden-cheeked warbler (Dendroica chrysoparia) in central Texas. Oak wilt, caused by the fungus Ceratocystis fagacearum, is considered a threat to habitat quality for this warbler. Basal girdling was tested for controlling fungal mat production on Texas red oak and for reducing disease spread at the stand level. For 2 years, symptomatic trees were girdled by stripping bark from the lower trunks in late summer. Trees were inspected the following spring for mats. Basal girdling reduced the overall proportion of infected stems that produced one or more fungal mat from 9.7 to 2.5%. Among mat-producing stems, basal girdling reduced the mean number of mats per stem from 4.78 ± 0.73 (least squares mean ± 95% confidence interval) to 2.78 ± 1.34. Probability that a stem would produce one mat or more was positively correlated with dbh and was significantly reduced by the basal girdling treatment. Two years of treatment did not affect 3rd-year infection levels within treated stands. However, the study design we used could not exclude local tree-to-tree spread of the pathogen through common/grafted roots. We suggest that basal girdling, used as a stand-alone practice, may not be effective in controlling the local spread of C. fagacearum in central Texas woodlands.

Response of Two Oak Species to Reduction Pruning Cuts

Reduction pruning cuts were used to prune Quercus virginiana (live oak) and Quercus Shumardii (shumard oak). One-half of the pruning wounds were harvested and dissected 3 years later to observe extent of discoloration in response to the pruning cut. Shumard oak did not limit discoloration as effectively as live oak. Discolored area in the wood increased with size of the pruning cut surface in shumard oak and less so in live oak. Dissections showed that the shape of the discolored area attenuated with depth. The branch connection morphology and response (branch–trunk aspect ratio, branch angle, release growth after pruning) appeared to influence discoloration pattern in reduction pruning. The angle of the reduction cut relative to the American National Standards Institute-recommended angle bisect method was not found to influence discoloration. Discoloration in the less efficient compartmentalizing species (Shumard oak) was related to cut surface area, but not to cut angle. There was no relationship between aspect ratio and discoloration in the 3 years after pruning. The data suggest that reduction cuts can be made back to lateral branches as small as one-third the diameter of the removed stem.

(142) Hydraulic Resistance: A Determinant of Short-term Stomatal Conductance Signaling in Disparate Xylem Anatomy of Red Maple (Acer rubrum L.) and Shumard Oak (Quercus shumardii Buckl.)

Recent work has shown that stomatal conductance (gs) and net photosynthesis (Anet) are responsive to the hydraulic conductance of the soil to leaf pathway (Xp). Two tree species with differing xylem structures were used to study the effect of systematic manipulations in Xp that elevated xylem hydraulic resistance. Simultaneous measures of gs, Anet, bulk leaf abscisic acid concentration (ABAL), leaf water potential (L), and whole plant transpiration (Ew) were taken under controlled environment conditions. Quercus shumardii Buckl. (shumard oak), a ring porous species and Acer rubrum L. `Summer Red' (red maple), a diffuse porous species, were studied to investigate the short-term hydraulic and chemical messenger response to drought. Both species decreased Anet, gs, L, and Ew in response to an immediate substrate moisture alteration. Relative to initial well-watered values, red maple Anet, gs, and Ew declined more than shumard oak. However, gs and Anet vs. whole-plant leaf specific hydraulic resistance was greater in shumard oak. In addition, the larger hydraulic resistance in shumard oak was attributed to higher shoot, as opposed to root, system resistance. The results indicate hydraulic resistance differences that may be attributed to the disparate xylem anatomy between the two species. This study also provides evidence to support the short-term hydraulic signal negative feedback link hypothesis between gs and the cavitation threshold, as opposed to chemical signaling via rapid accumulation from root-synthesized ABA.

(37) Irrigation and Fertilizer Placement Affects Plant and Weed Growth In Container Tree Production

On 24 Apr. 2003, 3-gallon (11.4-liter) Quercus shumardii were potted into 13.2-gallon (50-liter) containers using a standard nursery mix. Treatment design was a 3 × 2 × 2 factorial with two fertilizer placements, three irrigation methods, and two herbicide rates. Controlled-release fertilizer 17N–2.9P–9.8K was dibbled (placed 10.2 cm below the surface of the container media at potting) or top-dressed at a rate of 280 grams per container. Irrigation was applied using one of three methods: 1) a spray stake attached to a 3-gallon- (11.4-L-) per-hour pressure compensating drip emitter; 2) a surface-applied pressure-compensating drip ring delivering water at a rate of 2.3 gallons (8.9-L) per hour; and 3) the same drip ring placed 4 inches (10.2 cm) below the container substrate surface. A granular preemergent herbicide (oxyfluorfen + oryzalin) was applied at 2.0 + 1.0 lb/acre (2.24 + 1.12 kg·ha-1). At 75 days after treatment (DAT), containers with no herbicide and top-dressed fertilizer had a percent weed coverage of 46% compared to 18% for dibbled containers with no herbicide. At 180 DAT weed top dry weight was greater for top-dressed containers compared to dibbled. None of the treatments in the study had any effect on height increase. At 240 DAT, trees irrigated with drip rings at the surface had a 28% greater caliper increase among the dibbled fertilizer-treated containers. Trees irrigated with the drip ring placed below the surface and fertilizer top-dressed had the smallest caliper increase. Irrigation method had no effect on weed control in this study; however, a repeat fall application showed a significantly greater weed control with the drip ring below surface compared to the spray stake.