Daniel J. Robison

Productivity, drought tolerance and pest status of hybrid Populus: tree improvement and silvicultural implications

Abstract Sixteen hybrid poplars, Populus spp., were evaluated during the first 3 years and in year 6 of plantation growth. Significant clonal differences were found in survival, growth, and susceptibility to pests. Drought tolerance varied among clones. Branch and secondary stem biomass, and biomass density were important factors in tree weight. Impacts of the fungal pathogen, Septoria musiva , and herbivory by the cottonwood leaf beetle, Chrysomela scripta , and the meadow mouse, Microtus pennsylvanicus , varied greatly among clones. Five clones, NM6, DTAC2, NC5377, NC11396 and NC11004, exhibited high rates of survival, productivity, and canker disease resistance. Clones NM6 and DTAC2 were highly and moderately resistant, respectively, to meadow mouse herbivory. Clone NC11396 was moderately resistant to the cottonwood leaf beetle. All other clones were susceptible to these pests. These results are discussed in regard to tree evaluation and improvement strategies, and multiple pest complexes.

Multivariate approach for integrated evaluation of clonal biomass production potential

Abstract Evaluating the performance of clones to be used in short rotation intensive culture (SRIC) plantations for biomass production is critical for identifying superior clones and matching them with sites on which they will perform best. This will lead to increased production and a strengthening of the commercial prospects of these plantations. The primary objective of this study was to use a multivariate approach to evaluate the relative clonal performance of 38 willow and hybrid poplar clones, deployed in a genetic selection trial based on a coppice rotation system established in central New York State (NY) in 1997. Cluster analysis was conducted using survival, several individual plant growth attributes, and insect defoliation, all measured during or at the end of 1998. Two linear functions developed using discriminant analysis, comprising primarily of attributes related to tree vigor and site adaptability; tree volume index and length of growing period, explained most of the variation (98.5%) among the clusters. Eight of the 38 clones evaluated are expected to be high biomass producers, and are recommended for more extensive clone-site trials and commercial scale plantations across central NY and the northeastern United States (US). The results of this study indicate a possible approach to more effective juvenile selection in tree improvement programs, and insights for a refinement of the current SRIC tree ideotype.

Biological constraints on the growth of hardwood regeneration in upland Piedmont forests

The effects of aboveground fungi, insects, browsing mammals and weeds on the growth (height, diameter and volume index) and density of hardwood stems were studied on three upland sites in the Piedmont of North Carolina, USA during the first two growing seasons following clearcutting. Competition from weeds was the most detrimental to hardwood growth. Pesticide treatments alone (broad-spectrum insecticide, fungicide and mammal repellent) did not significantly increase growth. Compared to the control (no weeding or pesticides), stems receiving the pesticide+weeded treatment increased in height 1.6–4.5 times, diameter 1.7–5.3 times and volume index 3.4–5.1 times by the end of second growing season, across all sites. Stem density did not exhibit clear treatment effects, although individual tree mortality and recruitment in the plots were not recorded. Exclosures, with weeding, to eliminate the browsing impact of white-tailed deer (Odocoileus virginianus Zimmermann), installed only during the second year of study, yielded a 1.9, 1.6 and 3.2 times increase in mean stem height, diameter and stem volume index, respectively, as compared to weeded only plots. Results indicate that very young hardwood regeneration can respond quickly to release from biological constraints and the rate of stand establishment and development may be enhanced with stand manipulations in the first two growing seasons.

Evaluating hybrid poplar clonal growth potential in a three-year-old genetic selection field trial

Abstract Survival, growth, and insect and disease damage of 54 hybrid poplar clones were compared in a three-year-old genetic selection field trial located in the St Lawrence River Valley, near Massena, New York, USA. Clones were grouped into growth potential classes using cluster analysis and indices of total growth and canker severity. Statistical significance of growth potential classes was tested using discriminant analysis. Seven of the 54 clones examined (DN16, NM6, NE17, D51, DN38, DN55 and NE21) were recommended for additional evaluations in larger scale clone-site trials. The technique presented in this report facilitates hardwood clone performance evaluation for a wide variety of desired products.

Effect of cutting storage conditions during planting operations on the survival and biomass production of four willow (Salix L.) clones.

Planting vigorous cuttings that quickly develop shoots and roots is essential to the biological and economic success of willow biomass crops. Current recommendations are that cuttings should be planted within 2–4 days of being removed from long-term cold storage at −4 °C. However, maintaining this short time period is not always feasible. Results from greenhouse and field experiments indicated that leaving cuttings out of −4 °C long-term cold storage for up to 12 days before planting did not have a significant impact on survival or biomass production. For cuttings removed from long-term cold storage 23 days before planting, survival and per tree biomass production were lower for three of the four clones tested in a field trial. Returning cuttings to a −20 °C freezer 5–9 days after removal from −4 °C long-term cold storage, reduced the proportion of cuttings that developed roots or shoots, and shoot biomass of all clones. However, returning cuttings to either a +2 °C cooler or a −4 °C freezer had no effect on shoot biomass after 3 weeks of growth. Returning cuttings to supplemental cold storage at +2 to −4 °C may extend the time that cutting viability can be maintained after being removed from long-term cold storage and thawed. Returning cuttings to a −20 °C freezer for supplemental storage is not recommended.

Spruce budworm (Lepidoptera: Tortricidae) field fecundity : new insights into its estimation and use

Abstract Relationships between female spruce budworm, Choristoneura fumiferana (Clem.), pupal width and live weight, with realized field fecundity were determined in cages on branches of black spruce, Picea mariana (Mill.) B.S.P., in northern Maine. These are the first such determinations made on individual spruce budworms under field conditions. Fecundity varied from maximum levels similar to previously published findings in laboratory studies, to zero, independent of pupal size. Results suggest that previous laboratory studies of the pupal size–fecundity relationship have overestimated actual egg laying under field conditions, and therefore reduced the accuracy of some population studies.

Sexual behavior of Matsucoccus josephi (Homoptera: Margarodidae). Asynchronous adult male emergence and release of female sex pheromone.

The daily emergence patterns ofMatsucoccus josephi adults and third-instar male larvae raised on artificially infested saplings ofPinus halepensis were determined. A single peak of emergence was found for adult males between 0300 and 0500 hr. Adult females emerged throughout the day, with maximum emergence between 0500 and 0700 hr. Two daily emergence periods were observed in third-instar male larvae, one between 0300 and 0900 hr and the other between 1700 and 2100 hr. Airborne pheromone emitted by adult virgin females was collected using a flow system. No significant differences were recorded in the attraction of the male to crude pheromone collected at different times of day. A single female, virgin or half an hour after mating, was sufficient to attract the males in an olfactometer system. From minor differences in pheromone release throughout the day, and from the lesser degree of attraction by females half an hour after mating, it is assumed that there is no mechanism controlling the daily release of the female sex pheromone. Reduction of pheromone emission after mating is suggested.

Diseases and insect pests of Gmelina arborea: real threats and real opportunities

AbstractGmelina arborea Roxb. (gmelina) is a rapidly growing tree, which due to its drought tolerance and excellent wood properties, is emerging as an important plantation species. Perhaps the greatest threat to plantations of this tree is damage due to pests and diseases. Numerous insect pests and pathogens have been recorded in stands of gmelina in areas where the trees are native. Some fungal pathogens have been introduced into areas where the trees have been established as exotics. Among these, leaf spot caused by Pseudocercospora ranjita is most widespread although it has not caused any substantial damage. A serious vascular wilt disease caused by Ceratocystis fimbriata in Brazil has caused the most significant failure of G. arborea in plantations. In plantations within the natural range of the tree, insects have caused substantial damage. Among these, the defoliator Calopepla leayana (Chrysomelidae) appears to be most important. No serious insect pest problems have been recorded where G. arborea is grown as an exotic. All indications are that pathogens and insect pests will become much more serious impediments to the propagation of gmelina in the future. However, excellent opportunities exist to resolve such problems through biological control of insects and integrated disease and pest management. In addition, gmelina can be vegetatively propagated and thus, breeding and selection for insect and pathogen tolerance will facilitate the propagation of healthy trees. Palabras clave: Control biológico, Cuarentena, Especies exóticas, Implementación operacional de clones Resumen. La Gmelina arborea Roxb. (gmelina) es un árbol de rápido crecimiento, el cual debido a su tolerancia a las sequías y a sus excelentes propiedades de la madera se está convirtiendo en una especie de importancia para las plantaciones forestales. Tal vez, la amenaza más grande para las plantaciones de estos árboles es el daño causado por las plagas y las enfermedades. En las áreas en donde la especie es nativa, se han reportado gran cantidad de plagas de insectos y de patógenos. Algunos hongos patógenos se han introducido dentro de las áreas en donde los árboles han sido establecidos como especies exóticas. Entre estos, las manchas de las hojas ocasionadas por el hongo Pseudocercospora ranjita, es el más extendido aunque no ha causado ningún daño sustancial. Una seria enfermedad de marchitamiento vascular causada por el Ceratocystis fimbriata en el Brasil, ha causado la pérdida más seria en las plantaciones de G. arborea. En las plantaciones dentro del rango natural del árbol, los insectos han causado un daño considerable. Entre estos insectos, el defoliador más importante parece ser el Calopepla leayana (Chrysomelidae). En las áreas en donde la gmelina crece como una especie exótica no se han reportado problemas con las plagas de insectos. Todo parece indicar que en un futuro, los agentes patógenos y las plagas de insectos se convertirán en un impedimento más serio para la progagación de la gmelina. Sin embargo, a través del control biológico de insectos y del manejo integrado de las enfermedades y plagas, existen excelentes oportunidades para resolver este tipo de problemas. Además, la gmelina puede ser propagada vegetativamente y por lo tanto su mejoramiento y selección facilitará la propagación de árboles saludables por su resistenciacia contra los insectos y los patógenos.

Deploying Pest Resistance in Genetically-limited Forest Plantations: Developing Ecologically-based Strategies for Managing Risk

Deployment of genetically-based insect pest resistance in large-scale and intensively managed forest plantations requires ecological understanding to achieve sustainability. The problems of pest depravation and biotype evolution, and the emergence of new pests can be managed through the use of a well-designed variety of resistance and susceptibility factors. These must be selected based upon their ecological and genetic interaction with the pests of concern, and not merely through the use of a probability assessment of intolerable pest damage. The deployment of pest resistance mechanisms that do not foster uni-directional genetic selection is especially important. There must be greater coordination of pest-tree studies with tree genetic improvement programs, and the development of operational resistance screening methods, for insect resistance to be widely used in forest management activities.

Effects of artificial defoliation on growth and biomass accumulation in short-rotation sweetgum (Liquidambar styraciflua) in North Carolina.

Abstract Sweetgum, Liquidambar styraciflua L. (Hamamelidales: Hamamelidaceae), is a species of interest for short-rotation plantation forestry in the southeastern United States. Despite its high levels of resistance to many native insects and pathogens, the species is susceptible to generalist defoliators during outbreak epidemics. The objective of this field study was to evaluate the potential impact of defoliation on sweetgum growth and productivity within the context of an operational plantation. Over three growing seasons, trees were subjected to artificial defoliation treatments of various intensity (control = 0% defoliation; low intensity = 33% defoliation; moderate intensity = 67% defoliation; high intensity = 99% defoliation) and frequency (not defoliated; defoliated once in April of the first growing season; defoliated twice, once in April of the first growing season and again in April of the second growing season). The responses of stem height, stem diameter, stem volume, crown volume, total biomass accumulation, and branch growth were measured in November of each growing season. At the end of the first growing season, when trees had received single defoliations, significant reductions in all growth traits followed the most severe (99%) defoliation treatment only. After the second and third growing seasons, when trees had received one or two defoliations of varying intensity, stem diameter and volume and total tree biomass were reduced significantly by 67 and 99% defoliation, while reductions in stem height and crown volume followed the 99% treatment only. All growth traits other than crown volume were reduced significantly by two defoliations but not one defoliation. Results indicate that sweetgum is highly resilient to single defoliations of low, moderate, and high intensity. However, during the three-year period of the study, repeated high-intensity defoliation caused significant reductions in growth and productivity that could have lasting impacts on yield throughout a harvest rotation.