Adelges Piceae Research Articles

Balsam Woolly Adelgid Control, 1981

Abstract Two concentrations of Dursban (0.5% and 0.125%) and 2 of Pounce (0.25% and 0.125%) were evaluated for control of the Balsam Woolly Adelgid (BWA). Tests were conducted on a Fraser fir Christmas tree plantation in Jackson County, NC. Five plots with approximately 50 trees per plot were each sprayed with 1 of the concentrations of Pounce or Dursban using a hydraulic sprayer. The remaining plot was left as a control. Ten bark samples using a No. 9 cork borer, were taken from the Dursban plots while 20 and 5 samples were taken from the Pounce and control plots respectively. Samples were taken from the base of each tree stem before and 2 wk after spraying and during the next generation of aphids. The bark samples were kept refrigerated until microscopically analyzed for the four life stages of BWA. Living and dead BWA were counted and recorded.

DEVELOPMENT OF WOUND TISSUE IN THE BARK OF FRASER FIR AND ITS RELATION TO INJURY BY THE BALSAM WOOLLY ADELGID1

A total of 89 Fraser fir, Abies fraseri Pursh. (Poir.), from seven locations in the southern Appalachians were tested for non-suberized impervious tissue (NIT) at artificial wound sites. All trees except one formed NIT in a time period that was considered normal (3 weeks), with no delays due to tree age, location or presence of balsam woolly adelgid, Adelges piceae (Ratz.). Although most Fraser fir react to adelgid attack by forming “rotholz” (red wood), a number of infested trees showed no visual signs of rotholz formation.

Seasonal History of the Balsam Woolly Adelgid (Homoptera: Adelgidae) in Natural Stands and Plantations of Fraser Fir

Comparisons of the seasonal history of balsam woolly adelgid, Adelges piceae (Ratzeburg), populations were made at five elevations in the southern Appalachians. Populations in three natural stands of Fraser fir, Abies fraseri (Pursh) Poir, above 1,760 m produced two generations in 1983. The adelgids infesting a small plantation of mature fir at 1,219 m emerged from winter diapause a month sooner than those in natural stands, but most of the population completed two generations. A third generation was found in the adelgid population infesting a cultivate Fraser fir Christmas tree plantation at 853 m.

Subspecies of the Balsam Woolly Aphid, Adelges piceae (Homoptera: Adelgidae), in North America

Based on multivariate morphometric analysis of variation among populations in North America, three subspecies of balsam woolly aphid, Adelges piceae (Ratzeburg), are described and illustrated: A. piceae piceae (Ratzeburg), A. piceae canadensis (Merker and Eichhorn), and A. piceae occidentalis, subsp. nov. Diagnostic characters of the 1st instar and the adult and a key to the North American subspecies are provided.

Morphometric variation between populations of the balsam woolly aphid, Adelges piceae (Ratzeburg) (Homoptera: Adelgidae), in North America.

Morphological variation in characters of the first-instar and the adult stage of the balsam woolly aphid, Adelges piceae (Ratzeburg) (Homoptera: Adelgidae), were studied. Multiple discriminant analysis and UPGMA cluster analysis of the Mahalanobis generalized distances were used to classify 18 population samples collected on five Abies species throughout the known area of distribution. The populations were separated into three distinct groups: a "Maritime" group, a "British Columbia" group, and an "intermediate" group which consisted of samples from North Carolina, Oregon, and Washington. Variables taken from the adult morph gave a more consistent and, hence, a more reliable classification than the first-instar variables. Allocation of individual specimens into the three groups, as determined by identification functions, showed that the morphological characters measured in the adult stage correctly identified 85% of the specimens.It is suggested that the observed morphological divergence between eastern and western populations of A. piceae reflects the aphid's colonization history in North America. The importance of these findings for control is noted.

SAMPLING POPULATIONS OF ADELGES PICEAE (HOMOPTERA: PHYLLOXERIDAE) ON BALSAM FIR, ABIES BALSAMEA

AbstractThe balsam woolly aphid, Adelges piceae, has a complex distribution in the crown of trees; The sample universe and sample units are defined, and methods of detecting, monitoring, and measuring population levels at stated levels of confidence, accuracy, and assurance are described. Suggestions are given for sampling aphids on the stems of trees.

Effect of Balsam Woolly Aphid on Cone and Seed Production by Balsam Fir

The size of cones and the quantity and quality of seed produced by balsam fir, Abies balsamea (L.) Mill, in five balsam woolly aphid Adelges piceae (Ratz.), damage classes were compared. No cone or seed abnormalities that could be attributed to aphid infestation or the amount of aphid damage to the trees were detected. Also, the severity of aphid damage had no influence on the incidence of damage to cones and seed caused by cone insects. No balsam woolly aphids were found on cones.

Anatomical changes in the secondary phloem of grand fir (Abies grandis) induced by the balsam woolly aphid (Adelges piceae)

This study examines the microscopic anatomy and seasonal changes of the secondary phloem, cambium, and a portion of the xylem of grand fir trees (Abies grandis [Dougl.] Lindl.) infested with the balsam woolly aphid (Adelges piceae Ratz.) as compared with tissues of non-infested trees.The reactivation of the vascular cambium and production of astrosclereids and resin cells are about the same in infested and non-infested trees.The infested trees exhibit sieve cells that are shorter in length, having a tangential dimension about the same as normal cells, and produce more tangential bands of phloem parenchyma cells, more fiber sclereids, biseriate rays, and lipoidal-filled ray cells, abnormally shaped ray parenchyma cell nuclei, giant cortical parenchyma cells, and traumatic resin ducts in the xylem.

A new tissue essential to necrophylactic periderm formation in the bark of four conifers

Impermeability to OSO4 of periderm-free zones around the feeding sites of balsam woolly aphid (BWA), Adelges piceae, in the bark of Abies, was caused by a non-suberized impervious tissue (NIT). NIT developed at mechanical injuries in living bark of Abies grandis, Abies amabilis, Tsuga heterophylla, and Thuja plicata in 3 to 4 weeks during summer. It was found at healed injuries regardless of the cause, biotic or abiotic, at abscission scars, and at old resin blisters and rhytidome. It is concluded that NIT precedes formation of necrophylactic periderms (NP), may provide environment necessary for NP formation in tissues internally abutting NIT, and is a marker for distinguishing NP from exophylactic periderms. The imperviousness of NIT to water resulted neither from suberin (seven tests) nor from callose (three tests), and was detected by an F–F test, which is based on penetration of 2% FeCl3 followed by 4% K3Fe(CN)6 through the bark for 3 days each. The formation of NIT in the absence, e.g. rhytidome, as well as in the presence of injuries, BWA, and disease agents, suggests that NIT production is not only a non-specific inherent process but may be the physiological basis of host response to diseases in bark. Pathogen-free, "non-induced" NIT formation at rhytidome as a control process for isolating the host component of host–pathogen interactions is discussed.

Cone production of balsam fir damaged by balsam woolly aphid

The effect of balsam woolly aphid, Adelges piceae (Ratz.), damage on cone production by balsam fir, Abies balsamea (L.) Mill., was studied on 49 trees classified into six aphid damage classes. Results showed that there was no appreciable effect until damage exceeded the moderate level. Cone production on trees damaged beyond this level was seriously reduced but, since advanced damage is not reached by all trees simultaneously, it was concluded that adequate seed should be available for stand replacement.

DISTRIBUTION OF FIRST INSTAR NYMPHS OF ADELGES PICEAE (HOMOPTERA: PHYLLOXERIDAE) ON BRANCHES OF BALSAM FIR, ABIES BALSAMEA, AFTER COLONIZATION

AbstractBalsam woolly aphid nymphs, Adelges piceae (Ratz.), settle primarily in the apical 3-year growth of a branch. This portion of a branch is a natural population unit that can be designated a sample universe for detailed studies of aphid survival and mortality.

IMPACT OF THE BALSAM WOOLLY APHID (HOMOPTERA: PHYLLOXERIDAE) ON CONES AND SEED PRODUCED BY INFESTED FRASER FIR

AbstractSeed produced by Fraser fir, Abies fraseri (Pursh) Poir., infested by the balsam woolly aphid, Adelges piceae (Ratzeburg), was compared with that originating from uninfested trees during a cyclic year of heavy seedfall (1969) in western North Carolina. Cones were significantly shorter and seed uniformly lighter and smaller from trees infested by the aphid. X-ray examination indicated the number of full seed from uninfested trees averaged nearly 70% and 42% higher than in comparable seed samples from infested trees. Germination tests indicated viability of seed from infested trees exceeded 32% and that from uninfested trees exceeded 75%. An important factor affecting survival of seed from the two sources appeared to be the relative susceptibility of seed to attack by Megastigmus specularis Walley. Almost 28% more seed were destroyed by these seed chalcids for aphid-infested trees than for uninfested trees.

BALSAM WOOLLY APHID, ADELGES PICEAE (HOMOPTERA: PHYLLOXERIDAE), SEASONAL AND SPATIAL DEVELOPMENT IN CROWNS OF BALSAM FIR, ABIES BALSAMEA

AbstractThe balsam woolly aphid, Adelges piceae (Ratz.), in Newfoundland is dimorphic and has three generations a year in the crowns of balsam fir trees. Two generations of the sistens, or diapausing form, predominate. Progredientes are more common than elsewhere in North America and occur on nearly all parts of a branch. They do not mature on current needles. The ratio of progredientes to sistentes is about 1:40 in balsam fir flowering years and 1:80 in non-flowering years. Aphid development in the spring is earliest at flowered internodes, 11 to 14 days later at 2-year-old nodes, a further 4 to 8 days later at older nodes, and latest at the shoot tips. Intra-crown and inter-tree differences in aphid development are small but measurable. Stratification of the tree crown is required for sampling during the first aphid generation.

A Parasitic Fungus Disease of Adelges piceae (Homoptera: Phylloxeridae) in North Carolina

Since the balsam woolly aphid, Adelges piceae (Ratzeburg), was first discovered in the mid-1950's on Mt. Mitchell, North Carolina, this minute bark feeder has become a major pest of fir forests at the higher elevations in the surrounding area. Damage in this area has been particularly severe because Fraser fir, Abies fraseri (Pursh) Poir., on which it feeds, is highly susceptible to the aphid and dies after 2–5 years of attack. The aphid is notably free of natural enemies, and only arthropod predators have been regarded as holding any real hope of checking the formidable increases of this exotic sucking insect. No parasites are known, and only the most fragmentary evidence of disease associations has been reported in the past.

Phenomena of Adelges piceae Populations (Homoptera: Phylloxeridae) in North Carolina1

Populations of the balsam woolly aphid, Adelges piceae (Ratzeburg), on Fraser fir and factors affecting them were observed for a 2-year period. The host tree was the most important factor affecting the aphid after peak population was reached. The number of aphids settling on each tree greatly exceeded the carrying capacity of the tree; survival of aphids was correlated with condition of the tree. Early infestation of a tree is probably related to aphid density—the aphid modifies the bark and the result is increased fertility and survival of aphids per unit area of bark. Predators had little effect on the aphid population; primarily they ate eggs and showed a numerical response to egg density. However, egg losses attributed to predators were small when compared to total egg mortality and to egg survival. Survival of eggs was either not related to expected predation or increased as predation increased. Weather factors were considered primarily responsible for large losses of eggs, but were of little consequence in the dynamics of the aphid. Crawlers, neosistentes, and adults of the aphid are well adapted to survive weather conditions occurring when aphids in these stages are most prevalent.

THE STYLETS OF THE BALSAM WOOLLY APHID, ADELGES PICEAE (HOMOPTERA: ADELGIDAE)

AbstractThe morphology and fine structure of the stylets, labial clamp, and crumena of the balsam woolly aphid, Adelges piceae (Ratz.), are described from sections studied in the electron microscope.

FUNGUS DISEASES AFFECTING ADELGES PICEAE IN THE FIR FOREST OF THE GASPÉ PENINSULA, QUEBEC

AbstractIn 1966–67, the following fungi were isolated on Adelges piceae (Ratz.), a serious pest on fir trees in the Gaspé Peninsula: Fusarium larvarum, Cephalosporium coccorum, Entomophthora sp., Aspergillus fumigatus, Aspergillus nigra, Penicillium thomii, Penicillium sp., Cladosporium sp., Isaria farinosa, and Beauveria sp. F. larvarum showed more evidence of pathogenicity for Adelges, while C. coccorum was considered a facultative pathogen. There were not enough cases of infection by Isaria, Beauveria, and Entomophthora to determine their activity. Remaining species were saprophytic. Pathogenicity tests were conducted in the field with F. larvarum and C. coccorum. The fungi were introduced in the population by spraying or dusting, or by mites. However, a variety of external factors made it impossible to determine accurately the degree of virulence of these fungi for Adelges.

CHEMICAL CONTROL OF ADELGES PICEAE (HOMOPTERA: ADELGIDAE) IN NEWFOUNDLAND, 1967

AbstractFive insecticides (Baygon, diazinon, Dursban, Furadan, and menazon), previously shown to have some effect on control of the balsam woolly aphid, Adelges piceae (Ratz.), on branches of Abies balsamea (L.) Mill., have been tested more intensively. Individual trees were sprayed from the ground with 1.0, 0.5, or 0.25 litre of solution containing 5% active ingredient (an approximate per acre dosage rate of 12 to 25 lb). Dursban, Baygon, and diazinon caused 85, 75, and 72% mortality respectively. Furadan and menazon were less effective, causing 56 and 34% mortality.

Laboratory Studies on the Developmental Period and Feeding Behavior of Aphidecta obliterata (L.) (Coleoptera: Coccinellidae), an Introduced Predator of the Balsam Woolly Aphid1

Aphidecta obliterata completed its developmental period (egg through pupal stage) in 53 days at 15°C and 75% RH. Feeding studies showed that a straight-line relationship existed between length of larvae and the number of balsam woolly aphid, Adelges piceae (Ratzeburg), eggs consumed per capita per day. The average number of aphid eggs consumed per capita during larval development was 1853, with a range from 1579 to 2456. In the 4th stage, larvae consumed more eggs per capita than they did in the 1st 3 stages combined. The consumption of prey was reduced when predator density increased.

Effects of Temperature and Humidity on Development and Hatching of Eggs of Adelges piceae12

Effects of (1) a range of constant temperatures and humidities, (2) immersion in water, (3) desiccation, and (4) freezing temperatures on development and hatching of eggs and survival of crawlers were determined for the balsam woolly aphid, Adelges piceae (Ratzeburg). The developmental-hatching threshold was established at between 5 and 7°C and the upper limit for development at about 30°C. Hatching success was best and crawler life was longest at intermediate temperatures. Humidity had a pronounced effect on the incubation period, on hatching success, and on survival of crawlers. Immersion of eggs in water had no effect on subsequent hatching, but desiccation caused a reduction in hatch. Freezing had little effect on subsequent hatching of eggs unless the temperature was below —8°C. A rectilinear relationship existed between developmental rates and intermediate temperatures (excluding extreme high and low temperatures). The slope of the developmental-rate curve was modified by the effect of humidity. These findings are discussed in relation to observations of temperature and humidity in the field.