Arboriculture and Urban Forestry

Resultados del primer inventario de arbolado urbano de la ciudad de Mérida, los resultados hablan principalmente sobre la estructura y distribución de las especies, los servicios ambientales y lo que esto representa en términos monetarios para la ciudad de Mérida.

Se evaluó fitosanitariamente seis especies arbóreas: ficus (Ficus benjamina), ponciana (Delonix regia), molle serrano (Schinus molle), molle costeño (Schinus terebenthifolius), pacae (Inga edulis) y tulipán africano (Spathodea campanulata), en la Av. Monte de los Olivos del distrito de Santiago de Surco. Continuos inventarios forestales han informado sobre la presencia de enfermedades y/o agentes de destrucción que deterioran la salud de las seis especies de árboles. Se realizó el cultivo de los microorganismos patógenos, así como el montaje e identificación de los agentes perjudiciales del arbolado urbano. Los principales resultados indican que los hongos causantes de enfermedades son: Lasiodiplodia theobromae, Ganoderma applanatum, Fusarium sp. y Nigrospora sp., mientras que los insectos causantes de daños son: “trips” (Gynaikothrips ficorum), la quereza “conchuela hemisférica” (Saissetia coffeae), “pulgones” (Aphis nerii, Aphis craccivora), “mosca blanca” (Aleurothrixus sp.) y Calophya schini.

Bark beetles carry a number of associated organisms that are transferred to the host tree upon attack that are thought to play a role in tree decline. To assess the pathogenicity to western white pine (WWP; Pinus monticola) of fungi carried by the mountain pine beetle (MPB; Dendroctonus ponderosae), and to evaluate the potential for systemic prophylactic treatments for reducing fungal impacts, experiments were conducted with WWP seedlings to meet three objectives: 1) evaluate pathogenicity of two MPB-associated blue-stain fungi; 2) evaluate phytotoxicity of tree injection products; 3) evaluate the anti-fungal activity of tree injection products, in vitro and in vivo, toward the associated blue-staining fungi. To evaluate pathogenicity, seedlings were inoculated with Grosmannia clavigera or Leptographium longiclavatum, common fungal associates of MPB. Seedling mortality at four months after inoculation was 50% with L. longiclavatum and 90% with G. clavigera, both significantly higher than controls and thereby demonstrating pathogenicity. Phytotoxic effects of TREE-äge®, Alamo®, and Arbotect® were evaluated by stem injection; no phytotoxic effects were observed. Anti-fungal properties of the same three products were evaluated in vitro against G. clavigera, where Alamo was most active. Co-inoculation of G. clavigera and L. longiclavatum into seedlings after a stem injection of Alamo showed significantly less mortality and lesion formation than either species alone. Results support the hypothesis that MPB blue-stain associates, particularly G. clavigera, promote death of WWP when attacked by MPB. These findings suggest that the administration of a fungicide with insecticide for tree protection against bark beetles may be advantageous.

Municipal forestry programs in the United States have been the subject of dozens of surveys over the past 40 years that offer valuable insight into what is occurring now and act as a point of reference in the future. Researchers surveyed home-rule municipalities (pop. 5,000 or greater) in Texas, U.S. to assess the commonality of the components of a municipal forestry program, municipal spending on urban forestry, and amount of assistance received from the Texas A&M Forest Service. Spending on urban forestry in Texas cities averaged USD $4.88 per capita overall. Basic tree ordinances, tree boards, non-profit tree advocacy groups, and proactive maintenance cycles were all fairly common. Urban forest management plans and tree inventories were very uncommon. About 70% of municipal forestry programs are housed in their cities' Parks and Recreation Department, with the majority of the remainder occurring in their Public Works Department. The level of assistance received by municipalities from the Texas A&M Forest Service is consistent with the budget priorities and mission statement of that organization, which focuses on delivering technical and educational assistance over financial assistance. A lack of recent national trends to compare against greatly hampers understanding the efforts of Texas municipalities relative to other states. However, identifying current trends in Texas offers value to the Texas A&M Forest Service to understand the effect of their service delivery strategy. Urban foresters and city managers can also use these results to compare themselves against their peers, a common practice in setting municipal budgets and policy.