Yellowheaded Spruce Sawfly Research Articles

Effect of White Spruce Release on Subsequent Defoliation by the Yellowheaded Spruce Sawfly, Pikonema Alaskensis (Hymenoptera: Tenthredinidae)

Effect of White Spruce Release on Subsequent Defoliation by the Yellowheaded Spruce Sawfly, Pikonema Alaskensis (Hymenoptera: Tenthredinidae)

Predicting the seasonal development of the yellowheaded spruce sawfly (Hymenoptera: Tenthredinidae) in eastern Canada

AbstractDegree-day phenology models for the yellowheaded spruce sawfly,Pikonema alaskensis(Rohwer), were developed from data sets collected in infested plantations of black spruce,Picea mariana(Mill.), and white spruce,P. glauca(Moench) Voss, in New Brunswick and Quebec, Canada, between 1995 and 1999. The models describe the relationships between degree-day accumulation (above −1 °C, from 1 April) and cumulative adult emergence, capture in pheromone traps, the dates of appearance of first adult, egg, and larva, and the relative frequency of successive larval stages. The models predict adult emergence with a precision of ±2 days and male catch in pheromone traps with a precision of ±1.6 days. The first adult, first egg, and first larva occurred after 527 ± 42, 660 ± 52, and 725 ± 18 degree-days above –1 °C, respectively, and the dates of these events are predicted within ±1.8 days. The dates of 50% occurrence of the successive instars are predicted within 4.5 days of observed dates, and the date of peak 2nd instar is predicted within ±3.6 days.

Genetically based resistance of black spruce ( Picea mariana) to the yellowheaded spruce sawfly ( Pikonema alaskensis)

We evaluated the effect of plant genotype on resistance of black spruce ( Picea mariana (Mill.) BSP) to the yellowheaded spruce sawfly ( Pikonema alaskensis (Roh.)) in three half-sib family test sites and in a clonal seed orchard in New Brunswick, Canada. Heritability estimates were positively correlated to the percentage of trees defoliated by the sawfly in the half-sib family tests. At the site where the most damage occurred, the estimated individual heritability of resistance was 0.84, while that based on family means was 0.57. In the clonal seed orchard, the variability among clones explained 39.3% of the variation in defoliation, and individual clone heritability and clone mean heritability estimates were 0.40 and 0.82, respectively. Positive phenotypic and genetic correlations between tree height and damage suggest that selection for resistance may result in slightly slower tree height growth in some cases. These results suggest that there is good potential to select trees resistant to the sawfly that display other commercially desirable traits.

Interaction of Prechill and Chill Durations on Diapausing Prepupal Larvae of the Yellowheaded Spruce Sawfly (Hymenoptera: Tenthredinidae) and Associated Parasitoids

Prechill duration and chill duration have significant effects individually and interactively on diapause of the yellowheaded spruce sawfly, Pikonema alaskensis (Rohwer). Average time of emergence (weeks postchill) decreased with increased prechill (time between cocoon formation and chilling) and chill durations. Some treatments gave very low percentage of emergence. At 15°C, diapause development in the sawfly requires 23-24 wk. With short prechill durations (e.g., 3-6 wk) and chill durations of less than 12 wk, diapause development proceeded much slower at 0°C than at 15°C. However, with chill durations of 12 or more wk, diapause development was completed in much less than 23-24 wk (between 4 and 11 wk), at least for part of the population. Most of the rest of the population had their diapause developmental “clocks” reset to zero and spent an additional 23-24 wk in diapause development. A small percentage (about 1%) remained as prepupal larvae for over 70 wk. Percentage of emergence for three ichneumonid species increased with increased chill duration. The percentage of emergence of two ichneumonid species was affected by prechill duration, chill duration, and the prechill-chill interaction. The percentage of emergence of a tachinid parasitoid was unaffected by any treatment. Although times of emergence were unaffected by either prechill or chill duration for four species of ichneumonids, those for one ichneumonid and the tachinid decreased with increased prechill and chill durations.

A Method of Hazard-Rating White Spruce Plantations For Yellowheaded Spruce Sawfly Defoliation

Abstract A hazard-rating model for defoliation by the yellowheaded spruce sawfly was developed and validated using 25 white spruce plantations in north central Minnesota. The dependent variable was degree of defoliation, and the independent variables, as measured from small-format aerial photographs, were steepness and slope aspect. The site characteristics and defoliation were correlated using a maximum likelihood logistic regression. The final model determined that steep, south-facing slopes had the highest probability of sawfly-caused defoliation. Identification of high-hazard sites should be a major component of a management plan for this pest. North. J. Appl. For. 3:104-105, Sept. 1986.

Monitoring Damage by Yellowheaded Spruce Sawflies 1 with Sawfly and Parasitoid 2 Pheromones

Sex pheromone traps for the yellowheaded spruce sawfly, Pikonema alaskensis (Rohwer), and its ichneumonid parasitoid, Syndipnus rubiginosus Walley, were placed in white spruce, Picea glauca (Moench) Voss, plantations in north central Minnesota. The objective was to study the relationship between catches of the sawfly and its parasitoid and subsequent sawfly-caused defoliation. A significant linear relation was obtained when catches of both the sawfly and parasitoid were included in the model. The best-fit model was log( I ) = 1.36 − 0.17 log( S ) − 0.25 log( P ) + 0.13 log( S·P ) − 0.3 log( Ht ), where I is a trend index calculated using I = N (t)/ N (t-1), N is amount of defoliation during year t, S is sawfly catch, P is parasitoid catch, S·P is the interaction between the two, and Ht is tree height. Pheromone trap surveys of a host and parasitoid may provide information of the extent on natural control of the pest.

Cuticular hydrocarbons of the yellowheaded spruce sawfly, Pikonema alaskensis

Cuticular hydrocarbons of adult yellowheaded spruce sawflies, Pikonema alaskensis (Rohwer) (Hymenoptera: Tenthredinidae) were analyzed. Saturated hydrocarbons in males and females included n- alkanes and 2-methyl-, 3-methyl- and internally branched methylalkanes. The most abundant hydrocarbons were unsaturated: (Z)-9-pentacosene in males and (Z)-9-heptacosene in females. Additional (Z)-9-alkenes, traces of 6-, 7-, 8- and 10-alkenes, (Z,Z)-6,9-alkadienes and traces of alkatrienes were also found in both sexes. Pheromonally active (Z,Z)-9,19-alkadienes amounted to approx. 10% of the hydrocarbons in females but only to a maximum of approx. 0.1% in males. The amount of these dienes per female increased from 10.2 μg at 0–0.5 days old to 25.0 μg at 5–5.5 days old. These dienes were located on wings, legs, heads, thoraces and abdomens. They were also identified in field-collected mated females. The amount of (Z,Z)-9,19-dienes as a percentage of total hydrocarbons remained relatively constant with respect to age, location on body or occurrence of mating.

(Z)-10-nonadecenal: A pheromonally active air oxidation product of (Z,Z)-9,19 dienes in yellowheaded spruce sawfly

Each of 10 (Z,Z)-9,19 hydrocarbon dienes (28-37 carbons) found in female yellowheaded spruce sawflies,Pikonema alaskensis (Rohwer), was synthesized and found to be attractive to males by field bioassay. These dienes oxidize slowly in air, major products being aldehydes. One product common to all the dienes, (Z)-10-nonadecenal (Z10-19∶Al), and one from the 29-carbon diene only, (Z)-10-eicosenal, initiated flight and caused upwind anemotaxis in males in a greenhouse bioassay.Z10-19∶Al was incorporated into Hercon® controlled release formulations and was active in the field. The aldehyde could be useful for monitoring sawfly populations.

Evidence for a multicomponent sex pheromone in the yellowheaded spruce sawfly

The existence of a female-produced sex pheromone in the yellowheaded spruce sawfly,Pikonema alaskensis (Rohwer) (Hymenoptera: Tenthredinidae) was demonstrated by field and greenhouse bioassays. Virgin females, their empty cocoons (with which they were confined during handling procedures), and the hexane extract of these cocoons were attractive in the field. The only Florisil fraction of this extract consistently attractive by itself was that eluted with hexane, but three, more polar fractions (eluted with 5%, 25%, and 50% ether in hexane) each synergized the hexane fraction, increasing bioassay responses 10-30 times. Fractions derived directly from virgin females yielded comparable results. The greenhouse data corroborated the field data, except that the 5% ether-hexane fraction, while very synergistic in the field, was consistently inactive in the greenhouse.

Effects of Temperature on Diapausing Cocoons of the Yellowheaded Spruce Sawfly, Pikonema alaskensis12

This study sought optimal laboratory temperature conditions for obtaining adult yellowheaded spruce sawflies, Pikonema alaskensis (Rohwer) (Hymenoptera: Tenthredinidae), from cocoons of field-collected larvae. One month prechill at 23°C, 4 to 8 months chill at 0°C, and 15°C postchill temperature resulted in greater than 70% emergence within 8 weeks of warming. Extending the prechill period or using 8°C for the initial and final months of chill did not yield earlier or significantly higher emergence. Adult emergence was greatly reduced after 1 month prechill at 23°C and 1.5 to 3 or 9+ months chill at 0°C. When the prechill and chill periods totaled less than 3 months, emergence was extended, spanning 12 to 20 weeks, but when these periods totaled 7 months or more, emergence was very uniform, spanning 3 to 4 weeks in most cases. When the prechill and chill periods totaled 3 to 6 months, the effects of prechill duration and chill temperature on emergence pattern were complex. The relationship between emergence pattern and diapause is discussed. Diapause occurred under all the temperature regimes, and its duration at 15°C would prevent fall emergence in the field. Lower temperatures did not generally accelerate diapause development. Zero-degree cold prevented postdiapause development, which required ca. 4 to 5 weeks at 15°C.

Distribution of Cocoons of the Yellowheaded Spruce Sawfly 123

Cocoon distribution of Pikonema alaskensis (Rohwer) was studied in 10- to 12-yr-old white spruce plantations in Minnesota. Adjacent soil cores were taken radially from the trunk, extending 88 cm beyond the crown. Adult emergence traps were placed under, at the edge, and outside of the crowns. There were twice as many sawflies outside of the crown area with males predominating. The north and west sides had more sawflies. Fully developed larvae released in flats with one half of the area shaded did not show a cocooning preference for either the sunny or shaded side. Observations relate cocooning preferences to grass and moisture. Therefore, we feel that the preference for cocooning outside of the crown-covered ground is a grass and moisture related, rather than a sun-related, preference.

Morphology of the Adult Reproductive Systems of the Yellowheaded Spruce Sawfly, Pikonema alaskensis1

The internal and external reproductive systems of both sexes of field collected adults of the yellowheaded spruce sawfly, Pikonema alaskensis (Rohwer), are illustrated and described in detail.

Fecundity and Parthenogenesis of the Yellowheaded Spruce Sawfly, Pikonema alaskensis1

Fecundity of the yellowheaded spruce sawfly, Pikonema alaskensis (Rohwer) was studied in the greenhouse and the field using a bag cage tied over branches of white spruce trees, Picea glauca (Moench) Voss. Dissections of 279, 3–5-day-old females revealed a mean potential fecundity of 83.3 mature eggs. Females caged in the field laid 91.9% of their eggs, but females in the greenhouse laid only 61.7%. Longevity of females was 4–7 days, with 1 ♀ living 18 days. Parthenogenetic eggs developed into males. Peak oviposition in the field occurred when 80% of the new shoots were just barely retaining the bud cap. Female cocoons are significantly wider and longer than ♂ cocoons.

Use of Regression on Egg and First Instar Samples of the Yellowheaded Spruce Sawfly, Pikonema alaskensis, on White Spruce 1

Regression equations were used to determine an estimate of the number of eggs and 1st-stage larvae of Pikonema alaskensis (Rohwer) on young plantation white spruce trees, Picea glauca (Moench) Voss, for use in life table studies of the defoliator. A linear regression using a square root transformation was developed to predict the total numbers of eggs and 1st-stage larvae on a branch from counts of insects on the distal 15 new shoots at the branch tips. Also a cubic regression equation was developed to predict the number of branches per level by using total tree height. Both regressions were then used together to obtain an estimate of number of insects per tree.

Stadium and Sex Determination of Yellowheaded Spruce Sawfly Larvae, Pikonema alaskensis1

Head-capsule widths of feeding and prepupal larvae of the yellowheaded spruce sawfly, Pikonema alaskensis (Rohwer), were measured to determine the number of stadia. It was found that males have 5 stadia, and females have either 5 or 6. Parasitism has no effect on headcapsule width. The sex of prepupal larvae was determined.