Top Whorl Research Articles

Picea species from humid continental and temperate marine climates perform better in monsoonal areas of middle latitudes of China

Picea spp. are a prominent component of the boreal, montane, and sub-alpine forests in the Northern Hemisphere, and have substantial economic importance due to their high quality fibre. However, performance and wood properties of the genus have not been systematically evaluated in China. This study aimed to examine genetic variations in growth traits, phenology, and wood properties of 17 Picea species, (three from North America, two from Europe, and 12 from China), in response to specific climate factors using a randomized complete block design in a monsoonal, middle latitude area of China. Results show that all growth traits and wood properties significantly varied among species (P < 0.00). Of the 17 species examined, P. abies and P. pungens were the tallest with heights of 2.5 and 1.9 m at 9 years old, respectively, 90% and 50% greater than the average heights. Branch length, number, and angles of both P. abies and P. pungens were greater than those of the other species. Heights of P. glauca and P. omorika were 20–33% greater than the average. Fast-growing species had high quantities of first lateral branches and large top whorl branch lengths. The taller species exhibited greater tracheid lengths and average tracheid lengths to radial central diameter ratios (TL/R_D2), but smaller cell wall thicknesses to tracheid radial lumen diameter ratios (WT/R_D1), which is favorable for pulp production. Correlation analysis revealed that height and ring width had significant positive correlations with latitude but strongly negative correlations with longitude. Height was positively correlated with average annual rainfalls, but negative correlations with average yearly sunshine. Due to the increased average annual sunshine at the China test site relative to the seed source, species such as P. abies, P. pungens, P. glauca, and P. omorika from wet, humid areas performed better than native species. Considering similar temperatures, precipitation may be the main factor affecting growth, which is beneficial for predicting the extent of spruce expansion. These results should encourage further testing and provide reference information for future exotic species studies in this part of China.

Evaluation of Biological and Biorational Control Tactics for Suppression of Nantucket Pine Tip Moth Damage in Virginia Pine Christmas Trees

A study was performed to evaluate the potential of the egg parasitoid Trichogramma exiguum Pinto and Platner (Hymenoptera: Trichogrammatidae), the newly registered insect growth regulator (IGR) tebufenozide (Confirm), and a modified spray technique (top whorl only pesticide application) for suppression of Nantucket pine tip moth, Rhyacionia frustrana (Comstock) (Lepidoptera: Tortricidae), damage in Virginia pine, Pinus virginiana Mill., Christmas trees. Augmentative releases of T. exiguum failed to increase parasitism levels in release plots compared with controls, and significant reduction in tip moth damage did not occur. High predation levels on released T. exiguum may have contributed to the failure of parasitoid augmentations. Whole-tree and top whorl tebufenozide treatments provided significantly greater damage control than corresponding applications of acephate (Orthene), a commonly used pesticide in Christmas trees. Damage to trees receiving whole-tree chemical applications did not differ significantly from trees receiving top whorl treatments for most measurements of damage. Top whorl chemical treatments resulted in a 67% reduction in time required for application and a 70% reduction in pesticide used.

Evaluation of Biological and Biorational Control Tactics for Suppression of Nantucket Pine Tip Moth Damage in Virginia Pine Christmas Trees

A study was performed to evaluate the potential of the egg parasitoid Trichogramma exiguum Pinto and Platner (Hymenoptera: Trichogrammatidae), the newly registered insect growth regulator (IGR) tebufenozide (Confirm), and a modified spray technique (top whorl only pesticide application) for suppression of Nantucket pine tip moth, Rhyacionia frustrana (Comstock) (Lepidoptera: Tortricidae), damage in Virginia pine, Pinus virginiana Mill., Christmas trees. Augmentative releases of T. exiguum failed to increase parasitism levels in release plots compared with controls, and significant reduction in tip moth damage did not occur. High predation levels on released T. exiguum may have contributed to the failure of parasitoid augmentations. Whole-tree and top whorl tebufenozide treatments provided significantly greater damage control than corresponding applications of acephate (Orthene), a commonly used pesticide in Christmas trees. Damage to trees receiving whole-tree chemical applications did not differ significantly from trees receiving top whorl treatments for most measurements of damage. Top whorl chemical treatments resulted in a 67% reduction in time required for application and a 70% reduction in pesticide used.

Efficacy of Wing Versus Delta Traps for Predicting Infestation Levels of Four Generations of the Nantucket Pine Tip Moth (Lepidoptera: Tortricidae) in the Southern United States

Abstract The use of pheromone trap catches to reliably predict damage by the Nantucket pine tip moth, Rhyacionia frustrana (Comstock), in loblolly pine (Pinus taeda L.) plantations would provide forest managers with a valuable integrated pest management tool. At 17 sites throughout four states in the southern United States, in areas where R. frustrana has four annual generations, adult moths were monitored throughout the year (2002) using two types of pheromone traps, and subsequent infestation levels were determined for each tip moth generation. Cumulative wing trap catch tallies up to published spray dates for three of four adult emergence periods were highly predictive of top whorl damage during the subsequent generation using linear regression models. Multiple linear regression that included initial average tree height as a covariate did not significantly improve model efficacy. Cumulative delta trap catch tallies up to the spray date were not predictive of subsequent damage levels for any tip moth ge...

EVALUATION OF INUNDATIVE RELEASES OF TRICHOGRAMMA EXIGUUM (HYMENOPTERA: TRICHOGRAMMATIDAE) FOR SUPPRESSION OF NANTUCKET PINE TIP MOTH (LEPIDOPTERA: TORTRICIDAE) IN PINE (PINACEAE) PLANTATIONS

AbstractInundative releases of Trichogramma exiguum Pinto and Platner were evaluated for suppression of the Nantucket pine tip moth, Rhyacionia frustrana (Comstock), in first-year loblolly pine, Pinus taeda L., plantations. Three releases, spaced 7 d apart, were made in three 0.4-ha plots during second-generation R. frustrana egg deposition. Each release included three cohorts of T. exiguum developmentally separated by 25 degree-days. Mean ± SD field release rate for each cohort was 328 238 ± 88 379 females/ha. Mean T. exiguum emergence under laboratory conditions for released cohorts was 96 ± 2%, with 74 ± 3% females, of which 1 ± 1% of females displayed brachyptery; female longevity was 18 ± 3 d. Field emergence averaged 96 ± 4%. Parasitism of R. frustrana eggs was significantly increased, ranging from 40 ± 19 to 73 ± 22% in T. exiguum-treated plots and 17 ± 17 to 67 ± 21% in control plots. Data from all treated plots combined showed R. frustrana egg survival (hatching) was significantly reduced by 46%, and larval populations were significantly reduced by 60%. There was no significant difference in the percentage of terminals damaged between T. exiguum-treated (31 ± 16%) and control plots (45 ± 10%); however, length of terminal damage was significantly lower in treated plots. The percentage of damage to top whorl shoots was significantly lower in T. exiguum-treated plots compared with control plots, but there was no significant difference in length of tunneling damage. Damage to remaining shoots was not significantly different between T. exiguum-treated and control plots. Microhabitat significantly influenced both mean maximum and minimum temperature and the number of consecutive hours per day that were at or above 35 °C (critical temperature for T. exiguum survival). Soil surface with no cover had the greatest number of hours at or above 35 °C, followed by soil surface with herbaceous cover, and canopies of small trees (0.4 m tall). Canopy habitats in larger trees (0.9–1.8 m tall) had the most moderate temperature conditions. Parasitoid emergence was significantly reduced in response to increasing number of consecutive hours at or above 35 °C. Predation of parasitoids prior to emergence was significantly affected by microhabitat and by the length of time capsules were in the field before T. exiguum emergence (i.e., cohort number).

A Comparison of Three Common Indices Used for Estimating Nantucket Pine Tip Moth Damage in the Field

A quick and efficient means to estimate Nantucket pine tip moth, Rhyacionia frustrana (Comstock), damage levels that is also a reliable indicator of upper level and whole-tree damage is highly desirable because of the large sample sizes used in growth impact studies. Correlation and regression analyses were performed on the percentage of loblolly pine, Pinus taeda L., shoots damaged in three tree strata by R. frustrana. A large data set revealed highly significant correlations between terminal, top whorl, and whole-tree damage estimates. However, terminal and whole-tree estimates were weakly correlated. Top whorl damage was strongly correlated with both terminal and whole-tree damage indices. We conclude that top whorl damage indices are an efficient estimate and a sensitive indicator of both terminal and whole-tree damage levels.

Parasitism by Trichogramma spp. (Hymenoptera: Trichogrammatidae) in Relation to Nantucket Pine Tip Moth (Lepidoptera: Tortricidae) Egg Density and Location

Patterns of parasitism by Trichogramma spp. relative to density and location of Nantucket pine tip moth, Rhyacionia frustrana (Comstock), eggs were examined during 1994 in a 13-ha, 2-yr-old Pinus taeda L. plantation in northeastern Georgia. Egg densities were adjusted by temporarily enclosing trees in fine mesh screen cages and introducing different numbers of tip moths. After exposing eggs to naturally occurring parasitoids, all shoots were removed, and eggs were counted and evaluated for parasitism. Tip moth egg densities ranged from 203 to 2,579 per tree for the spring generation, and from 1 to 89 per tree for the summer generation. Tip moths deposited significantly greater numbers of eggs on needles than shoots on high-versus low-egg-density trees. Overall parasitism rates were 37.2 and 43.3% for spring- and summer-generation eggs, respectively. Parasitism was density independent at the whole-tree level in both generations, but spring-generation parasitism was strongly inversely density dependent in the top whorl. Numbers of eggs per needle fascicle ranged from 1 to 15 for spring-generation trees. Actual numbers of parasitized eggs per discovered fascicle (one on which parasitism occurred) increased with egg density, but the percentage of parasitized eggs decreased. Egg density had no effect on fascicle discovery. These factors produced an inversely density-dependent relationship between egg parasitism and density at the fascicle level. Eggs located on shoots suffered significantly greater parasitism rates than those on needles. Implications of these results are discussed.

Within‐plant distribution of a galling adelgid (Homoptera: Adelgidae): the consequences of conflicting survivorship, growth, and reproduction

Abstract. 1. Adelges cooleyi (Gil.) was rarely found in the top‐most whorl of shoots in its host plant Engelmann spruce.2. The survivorship of the few Adelges fundatrices which did colonize the top whorl was at or near zero for the 3 years in which survivorship was assessed, while survivorship in the bottom whorls was at least 60%.3. In contrast, when an Adelges fundatrix did survive in the top whorl, her growth and reproductive output, and the growth of her progeny, the gallicolae, were at least double that of bottom whorl fundatrices.4. The distribution of fundatrices within spruce trees was strongly correlated (R2=0.934) with fundatrix fitness (=survivorship × fecundity × growth).5. We hypothesize that the vigorous growth of top whorl shoots promotes Adelges growth and fecundity, but the earlier growth of these shoots results in low temperature mortality of fundatrices.

Nutrição mineral de seringueira XII. Quantidade de Al no substrato afetando a concentração e o acúmulo de Ca, Mg e S em seringueira (Hevea spp)

Com o propósito de comparar os efeitos de doses crescentes de alumínio sobre a concentração e acúmulo de Ca, Mg e S sobre a planta conduziu-se o experimento usando-se separadamente a solução nutritiva de BOLLE JONES (1957) e soluções de alumínio nas concentrações de 0, 5, 10, 15, 20 e 25 ppm em que as plantas passaram 24 horas e outras 24 horas em solução sem alumínio. Noventa dias após as plantas foram coletadas e separadas em raiz, caule, folhas dos verticilos inferiores e folhas do último verticilo. Determinou-se as concentrações e os acúmulos de Ca, Mg, e S. Os autores concluíram que níveis superiores a 15ppm de alumínio na solução provocam distúrbios nutricionais destes elementos em Hevea.

Nutrição mineral de seringueira: IX. alumínio no substrato afetando o desenvolvimento, a sintomatologia de toxicidade e a concentração em seringueira (Hevea spp)

Com o propósito de comparar os efeitos de doses crescentes de alumínio sobre o desenvolvimento de plantas de seringueira e distinguir o grau de tolerância do grau de toxicidade desse elemento sobre a planta, conduziu-se um experimento usando-se separadamente solução nutritiva de BOLLE-JONES (1957) e soluções de doses de alumínio que se constituíram de 0, 5, 10, 15, 20 e 25ppm de alumínio, em que as plantas passaram vinte e quatro horas na solução nutritiva (sem alumínio) e vinte e quatro horas nas soluções de alumínio correspondentes aos tratamentos acima. As plantas foram coletadas e separadas em raíz, caule, folhas dos verticilos inferiores e folhas do último verticilo. Determinaram-se os acúmulos de alumínio e as concentrações em função das doses de alumínio em cada parte da planta. Os sintomas visuais de toxicidade de alumínio foram identificados e descritos. Concluiu-se que: - o desenvolvimento de plantas de seringueira é afetado a partir de 15ppm de alumínio na solução; - Sinais de excesso de alumínio aparecem primeiro no sistema radicular. Na parte aérea, é difícil identificar efeito tóxico de alumínio dado a sua semelhança com sintomas visuais de deficiência de fósforo; - A seringueira é planta acumuladora e tolerante a presença de concentrações de alumínio no substrato inferior a 15ppm. Níveis superiores de alumínio provocam distúrbios nutricionais na planta.

Insecticide Efficacy on the Pine Needle Midge, 1984

Abstract Eleven Vi acre test plots were installed in a Christmas tree stand in section 8 of Inverness township in Cheboygan County, MI. Each plot contained approximately 100 Scots pine trees ranging from 4 to 8 feet tall. Midge damage from the previous growing season was prevalent in all test plots and distributed evenly across the field. Experimental treatments were applied with a Solo 423 back pack mistblower calibrated in 15 gal/a. Sprays were applied once at the time of initial adult emergence as indicated by emergence trap catch (21 Jun). Winds were slight at the time of spray (&amp;lt;5mph) and the ambient air temperature was approximately 22°C. Meta-Systox R, the current industry standard, was applied by the cooperating grower twice with the first treatment applied 2 days after all other experimental treatments. The second treatment of Meta-Systox R was applied 1 wk after the first at recommended label rates. At that time all stages of larvae were present and damage was just beginning to show up in the area. Approximately 2 wk later the spray block was surveyed for infested fasicles. On 75 randomly selected Scots pine trees the number of infested fasicles were estimated on the top whorl and leader (Test 1). Total midge impact was measured at the end of the growing season using a rating system devised to rank trees ordinally according to the severity of damage. The system is as follows: 0, no discernable midge damage; 1, slight damage contributing to degrade slightly; 2, damage moderate causing noticible degrade and 3, damage severe, tree may be unmarketable for 1-3 years. During late October, just prior to harvest, fifty systematically selected trees were rated from each treatment plot (Test 2). Damage ratings were analysed using a Kruskal-Wallis analysis of variance. Individual treatment comparisons were made with a Wilcoxon Rank Sum test. This non parametric approach is analogous to a standard ANOVA and t tests although more appropriate for ordinal ratings that do not usually meet the assumptions of an ANOVA. Individual comparisons were made between the standard, Meta-systox R and each treatment. Comparisons marked with a “s –” performed significantly worse than the standard. Treatments marked with a “s + ” performed significantly better. Those treatments marked with a “ns” do not show a significantly different damage rating than the industry standard, Meta-systox R.

Branch development on leaders of Piceasitchensis

The top whorl of branches on each year's leader on mature P. sitchensis (Bong.) Carr. had more needles and longer needle internodes than branches lower down on the leader. All branches developed as buds for similar periods of time from April to October, but top branch buds developed larger apical meristems which generated needle primordia more rapidly than lower branch buds. In mid-August, top branch buds produced at least 13 primordia per day compared with only 5 per day in basal buds. In the next year, when these preformed buds extended, top branches produced about one and a half times as many cells per needle internode as basal branches, as judged by observing the pith. In both years, cell division was the important growth process affected by 'dominance' mechanisms between branch buds.

Über den Einfluß der Lufttrocknung auf den Nährelementgehalt der Fichtennadel ): The Influence of Air Drying on the Nutrient Level of Spruce Needles

In an 18-year-old spruce ( Picea abies ) stand the lateral shoots of the top whorl were cut off monthly. From the harvested material two analogous samples were prepared in each case. One of the samples was dried at 70 °C in a drying cabinet (oven-dried sample), the second sample was dried at a room temperature of 18 °C (air-dried sample). The needles that fell from the shoots as a result of drying were subsequently dried at 105 °C to their absolute dry weight and analysed. During all seasons of the year air-drying lowers the 1000-needle-weight, whereas it raises the calcium and manganese level respectively. From July (or August) to May in the following year, when air-drying was applied, the potassium (and phosphorus) level in the spruce needles increased likewise. N and C content in the spruce needles differently respond to air-drying in the course of the year. Needles harvested in summer and autumn reduce their N and C content, when air-dried, while in early spring: N and C content increase in the spruce needles, when air-drying is applied.

Observations on the Distribution of the Spruce Bud Midge (Rhabdophagaswainei Felt) in Black and White Spruce Crowns and Its Effect on Height Growth

Populations of the spruce bud midge (Rhabdophagaswainei Felt) were sampled on 1 to 6 ft tall black and white spruces (Piceamariana (Mill.) BSP. and P. glauca (Moench) Voss) in central Alberta. The incidence of attacked buds is described in relation to tree height and crown aspect, and in relation to terminal buds of the leader and top whorl branches. Some characteristics of the infested bud are given to assist in its recognition in the field.After leader terminal buds of young white spruce were removed to simulate midge damage, height loss during the same year averaged 25.3%. Normal height growth was resumed in the following year from an apical-dominant lateral branch. The study suggested that, for general surveys, a count of the number of attacked terminal leader buds in young spruce could provide a useful index of midge abundance and provide the basis for estimating its impact on tree height growth.

Responses of Nantucket Pine Tip Moth Parasites to Tree Level, Orientation, and Hosts per Pine Tip1

Responses of Rhyacionia frustrana (Comstock) parasites to height level, orientation, and population density the host were studied in the Piedmont Region of South Carolina. The variation in degree of parasitism and the influencing factors in this study were attributed to variation among plantations and between the height levels of the pine trees. The degree of parasitism of R. frustrana in the top whorl of the pine trees as compared with the lower level was significant at the 1% level. There was no significant difference in parasitism as a result of orientation, number of R. frustrana per pine tip, or the interactions produced by these factors.