Dioryctria Abietivorella Research Articles

Assessment and Models of Insect Damage to Cones and Seeds of Pinus strobiformis in the Sierra Madre Occidental, Mexico.

Insect damage to cones and seeds has a strong impact on the regeneration of conifer forest ecosystems, with broader implications for ecological and economic services. Lack of control of insect populations can lead to important economic and environmental losses. Pinus strobiformis is the most widespread of the white pines in Mexico and is widely distributed throughout the mountains of northern Mexico. Relatively few studies have examined insect damage to the cones and seeds of these pines, especially in Mexico. In this study, we therefore analyzed insect damage to cones and seeds of P. strobiformis in Mexico by using X-ray and stereomicroscopic analysis. The specific objectives of the study were (a) to characterize insect damage by measuring external and internal cone traits, (b) to assess the health of seeds and cones of P. strobiformis in the Sierra Madre Occidental, Mexico, and (c) to estimate the relative importance of the effects of different environmental variables on cone and seed damage caused by insects. We found that 80% of P. strobiformis seeds and 100% of the tree populations studied had damage caused by insects. Most seeds were affected by Leptoglossus occidentalis, Tetyra bipunctata, Megastigmus albifrons, and the Lepidoptera complex (which includes Apolychrosis synchysis, Cydia latisigna, Eucosma bobana, and Dioryctria abietivorella). The cones of all tree populations were affected by some type of insect damage, with Lepidoptera causing most of the damage (72%), followed by Conophthorus ponderosae (15%), the hemipteran L. occidentalis (7%), and the wasp M. albifrons (6%). The proportion of incomplete seeds in P. strobiformis at the tree level, cone damage by M. albifrons and seed damage in L. occidentalis were associated with various climate and soil variables and with crown dieback. Thus, cone and seed insect damage can be severe and potentially impact seed production in P. strobiformis and the reforestation potential of the species. The study findings will enable managers to better identify insects that cause damage to cone and seeds. In addition, identification of factors associated with damage may be useful for predicting the levels of insect predation on seeds and cones.

Pheromone identification ofDioryctria abietivorella(Lepidoptera: Pyralidae) from an eastern North American population: geographic variation in pheromone response

AbstractThe fir coneworm,Dioryctria abietivorella(Groté), is a transcontinental pest of coniferous seed cones. Recently, the attractive pheromone components and lure blend for the fir coneworm in western Canada were identified as a 200 µg : 2000 µg ratio of (9Z,11E)-tetradecadienyl acetate (9Z,11E-14:Ac) and a polyunsaturated hydrocarbon, (3Z,6Z,9Z,12Z,15Z)-pentacosapentaene (C25pentaene). A potential third component, (Z)-9-tetradecenyl acetate (9Z-14:Ac), which was detected in pheromone gland extracts, had no effect on males of the western population when added to the binary blend. In contrast, in eastern Canada (Quebec) we found that the 200 µg : 2000 µg binary blend was unattractive to male fir coneworms until 9Z-14:Ac was added. By means of several field experiments we established that a 67 µg : 200 µg : 2000 µg ratio of 9Z-14:Ac, 9Z,11E-14:Ac, and the C25pentaene was attractive to fir coneworms in Quebec. Gas chromatography - mass spectrometry analysis of pheromone gland extracts of fir coneworm from Quebec confirmed the presence of the three components in extracts in an approximately 1 µg : 4 µg : 10 µg ratio of 9Z-14:Ac, 9Z,11E-14:Ac, and the C25pentaene. Our results provide evidence that the eastern and western populations ofD. abietivorellaare distinct geographic pheromone races, with 9Z-14:Ac being required for attracting males of the eastern population but not males of the western population.

Optimization of pheromone lure and trap design for monitoring the fir coneworm, Dioryctria abietivorella

AbstractThe major components of the sex pheromone of Dioryctria abietivorella (Groté) (Lepidoptera: Pyralidae) were recently identified as (9Z,11E)‐tetradecadien‐1‐yl acetate (9Z,11E‐14:Ac) and a polyunsaturated, long‐chain hydrocarbon (3Z,6Z,9Z,12Z,15Z)‐pentacosapentaene (C25 pentaene). The optimal ratio of these components and the role of potential minor components were not fully determined in the initial short report on the pheromone's identification. We tested different ratios of the two major components loaded into grey halobutyl rubber septum dispensers, placed in sticky traps deployed in conifer breeding arboreta. The optimal ratio of the two components was 200 µg 9Z,11E‐14:Ac to 2000 µg C25 pentaene. (Z)‐9‐Tetradecen‐1‐yl acetate, which had been identified previously in female pheromone gland extracts, and five other potential minor pheromone components, were tested individually as additions to the optimized two‐component lure blend. None of the ternary blends were more attractive than the optimized two‐component blend, at the ratios tested. Two lure adjuvants, a UV stabilizer (Sumisorb 300) and the antioxidant butylated hydroxytoluene, added individually or together, did not affect the attractiveness of the optimized lure blend. The Pherotech diamond sticky trap baited with the optimized lure blend was the most effective trap design among eight types of sticky trap and a bucket style trap that were tested. Traps baited with synthetic lures were as attractive as traps baited with virgin female moths. The optimized two‐component lure blend in the Pherotech diamond trap is recommended for monitoring fir coneworm infestations. The availability of an effective synthetic pheromone opens the possibility for control tactics using mating disruption or attract‐and‐kill techniques.

DIAPAUSE INDUCTION AND OVERWINTERING STAGE IN THE FIR CONEWORM (LEPIDOPTERA: PYRALIDAE)

AbstractA laboratory experiment was conducted to identify the overwintering stage of the fir coneworm,Dioryctria abietivorella(Grote), in eastern Canada and determine the influence of photoperiod on diapause induction. In another experiment, different developmental stages were exposed to field conditions to evaluate their capacity to survive the overwintering period. Insects were either placed in the duff or exposed to ambient (above ground) conditions to assess the importance of overwintering site on winter survival. Exposure of the fir coneworm to constant short-days or a daily decreasing photoperiod during larval development induced almost all insects to initiate diapause at the fifth instar. Third-, fourth-, and fifth-instar larvae survived the overwintering period when placed in the duff. Because the fir coneworm must leave its host tree and drop to the ground to avoid rigorous winter conditions, we concluded that only fifth-instar larvae could resume development in spring using such a strategy.

Performance of the fir coneworm Dioryctria abietivorella (Grote) as affected by host species and presence or absence of seed cones

Abstract1 Larval performance of Dioryctria abietivorella (Grote) (Lepidoptera: Pyralidae) was compared when insects were reared in white spruce, black spruce and Jack pine seed orchards. For each species, half of the insects developed in the presence of cones, while the other half was maintained on branches without cones.2 Significantly faster development rates were observed on spruce species when compared to Jack pine. Significant differences in survival were also recorded between the different feeding treatments.3 The presence of seed cones on spruce species significantly increased insect mean weight compared with branches without cones, but no significant differences were noticed between the different tree species with cones.4 White spruce is the most suitable host tree for fir coneworm feeding and the availability of seed cones plays an important role in determining D. abietivorella larval performance.

Correction for differences in volatility among olfactory stimuli and effect on EAG responses of Dioryctria abietivorella to plant volatiles

We describe a method using paraffin oil solutions and gas chromatography to measure and correct for differences in volatility among test compounds applied to filter paper and to address the problem of minimizing solvent contributions to EAG responses. To examine the effect of the volatility bias, we evaluated the EAG responses of female fir coneworm, Dioryctria abietivorella, to five volatile plant compounds, using a new method to normalize EAG responses to account for the loss of antennal sensitivity that occurs over time. Stimuli were generated either from equimolar (uncorrected) solutions or from corrected solutions that were adjusted to yield equimolar airborne concentrations in the air puffed over antennae. When uncorrected solutions were tested, the two most volatile compounds, (E)-2-hexenal and (E)-3-hexenyl acetate, elicited significantly larger EAG responses than three terpenes. When corrected concentrations were tested, the ranking of these responses changed: (E)-2-hexenal elicited significantly smaller EAGs than (−)-α-pinene, (−)-limonene, and (E)-3-hexenyl acetate. On the other hand, there was no effect on the ranking of EAG responses to the two monoterpenes and a sesquiterpene, (−)-trans-caryophyllene, relative to each other. Normalization of EAG data did not affect the overall results (i.e., stimulus rankings) but did reduce their variance within preparations. The results show that when compounds with widely different volatilities are compared in olfactory bioassays, the concentrations of test solutions should be adjusted to produce emissions with equimolar airborne concentrations.

VULNERABILITY OF THE FIR CONEWORM, DIORYCTRIAABIETIVORELLA (GROTE) (LEPIDOPTERA: PYRALIDAE), IN DIFFERENT LARVAL STAGES TO THE HD-1 STRAIN OF BACILLUS THURINGIENSIS

The fir coneworm, Dioryctria abietivorella (Grote), is a major insect pest in seed orchards across Canada and the adjoining eastern and western United States. Larvae feed principally on cones, but they can also feed on needles and occasionally on the bark of young tree trunks (Hedlin et al. 1980; Ruth 1980; Martineau 1985). The potential for a population of D. abietivorella to build up in seed orchards may be greater than in natural stands (Hedlin et al. 1980; Ruth et al. 1982). The use of entomopathogen in the management of fir coneworm could be an adequate measure to reduce the impact of this insect. Moreover, Bacillus thuringiensis ssp. kurstaki has a specific effect on Lepidoptera (Aronson et al. 1986; Gill et al. 1992). The purpose of our study was to determine the activity of the HD-1 strain of B. thuringiensis ssp. kurstaki (serotype H-3a:3b) to larvae D. abietivorella. Bioassays were conducted with first-, third-, and fifth-instar larvae of fir coneworm to determine whether or not the insect's vulnerability to B. thuringiensis varies with larval age.

Oviposition and Electroantennogram Responses of Dioryctria abietivorella (Lepidoptera: Pyralidae) Elicited by Monoterpenes and Enantiomers from Eastern White Pine

Volatile emissions from twigs of eastern white pine, Pinus strobus L., stimulated oviposition by Dioryctria abietivorella (Grote) in laboratory bioassays. Chemical identification and percentage composition of monoterpenes emitted by twigs were determined by capillary GC and GC/MS analysis of headspace and of volatiles entrained on Porapak Q. Enantiomeric excess of optically active monoterpenes was determined by capillary GC analysis with a β-cyclodextrin chiral column. Four of the six most abundant monoterpenes identified in twig volatiles elicited a significant oviposition response. Myrcene and car-3-ene [predominantly the (+)-enantiomer] were the most active compounds in both electroantennogram (EAG) and oviposition bioassays. In contrast, (−)-limonene elicited a significant oviposition response but was the least stimulating monoterpene in EAG tests. Female EAG responses to monoterpenes generally increased with age and mating and were larger than those from males of the same age.

FIR CONEWORM, DIORYCTRIA ABIETIVORELLA (GROTÉ) (LEPIDOPTERA: PYRALIDAE), PREFER CONES PREVIOUSLY EXPLOITED BY THE SPRUCE CONE MAGGOTS STROBILOMYIA NEANTHRACINA MICHELSEN AND STROBILOMYIA APPALACHENSIS MICHELSEN (DIPTERA: ANTHOMYIIDAE)

AbstractWe tested the prediction that larvae of the fir coneworm, Dioryctria abietivorella (Groté), preferentially exploit cones previously damaged by cone maggots, Strobilomyia spp. In most years sampled, fir coneworm attacked a significantly greater proportion of maggot-damaged than healthy cones of both white spruce and black spruce. The ecological implications for pest management are briefly discussed.

Cone and Seed Insect Phrenology in a Douglas-Fir Seed Orchard During Three Years in Western Oregon

Seasonal patterns of cone and seed insect activity and seed loss relative to cone production and weather patterns were examined over a 3-yr period in a Douglas-fir, Pseudotsuga menziesii (Mirbel) Franco, seed orchard in western Oregon. Six insect species showed distinct patterns of occurrence and cone or seed damage during this period. A weevil, Lepesoma lecontei (Casey); the Douglas-fir cone gall midge, Contarinia oregonensis Foote; and two lepidopterans, Barbara colfaxiana Kearfott and Dioryctria abietivorella (Grote), damaged cones or seed exposed during late April each year. The Douglas-fir seed chalcid, Megastigmus spermotrophus Wachtl, damaged seed in cones exposed during May and June; western conifer seed bug, Leptoglossus occidentalis Heidemann, was most damaging in cones exposed July-August.

EFFICACY OF ESFENVALERATE FOR CONTROL OF INSECTS HARMFUL TO SEED PRODUCTION IN DISEASE-RESISTANT WESTERN WHITE PINES

AbstractWe tested the pyrethroid insecticide esfenvalerate in single, double, and triple applications for control of insects affecting seed production of blister rust-resistant western white pine, Pinus monticola Douglas. All treatments increased the proportion of normal seed produced and reduced the proportion of seed damaged by the western conifer seed bug, Leptoglossus occidentalis Heidemann. Only the triple application reduced the proportion of cones killed by the pine cone beetle, Conophthorus ponderosae Hopkins. Other seed-damaging insect species [seed chalcids, Megastigmus sp.; the fir coneworm, Dioryctria abietivorella (Grote); and seedworms, Cydia sp.] were present but in numbers too low to test for insecticide efficacy.

The effects of fir coneworm, Dioryctria abietivorella (Grote) (Lepidoptera: Pyralidae), on seed production in small, isolated populations of red pine, Pinus resinosa Ait.

Red pine ( Pinus resinosa Ait.) is a rare endemic species in Newfoundland, where it occurs in small, isolated stands at the northeastern extreme of its geographic range. During 1989 and 1990, the fir coneworm, Dioryctria abietivorella (Grote), infested the entire cone crop in two of six natural red pine stands in eastern Newfoundland while the average incidence of coneworm in the remaining four stands was 89% in 1989 and 83% in 1990. Incidence of fir coneworm averaged 25% (1989) and 22% (1990) of the cone crop in five natural stands from a population in western Newfoundland. Following a bumper cone crop in all conifers in 1988, high numbers of fir coneworm became concentrated in red pine which has produced consistently good cone crops for 3 consecutive years, while cone production has been sporadic in other conifers. The coneworm infestation reduced the number of full seeds per cone by 93%, and cone size by 17% in severely infested trees of the eastern Newfoundland red pine population. High seed losses documented in 1989 and 1990 demonstrate the effects of stochastic events on reproductive success in rare populations, and the potential adaptive value of sporadic cone crops in limiting seed losses. The number of full seeds per cone was reduced by only 11%, with no significant reduction in cone size, in the lightly infested trees in western Newfoundland. However, trees from the eastern population compensated for low numbers of full seeds per cone by producing significantly larger seeds, thereby compensating for losses in seed number by increasing the average fitness or quality of the remaining full seeds. If coneworm infestations continue at current high levels for an extended time, reproductive success in the small, fragmented red pine population of eastern Newfoundland may be adversely affected.

PHYTOPHAGOUS INSECT COMPLEX ASSOCIATED WITH CONES OF WHITE FIR, ABIES CONCOLOR (GORD. AND GLEND.) LINDL., AND ITS IMPACT ON SEED PRODUCTION

AbstractWhite fir cones were sampled for insect damage from wild stands in California and Nevada during 1984–1986. Insects were recovered from cones and seed damage was partitioned by insect species. The important phytophagous insects were separated into guilds: the cone- and seed-mining guild, Dioryctria abietivorella Groté, Eucosma prob. siskiyouana (Kearfoot), Cydia prob. bracteatana (Fernald), Barbara sp.; the seed-feeding guild, Megastigmus pinus Parfitt, M. rafni Hoffmeyer, Earomyia abietum McAlpine; and the scale- and bract-feeding guild, Asynapta hopkinsi Felt, Dasineura prob. abiesemia Foote, Resseliella conicola (Foote), Strobilomyia abietis (Huckett). Total damage by insects varied by year and site, reaching a maximum of 47% in 1986 on one site and a minimum of 12.5% in 1984 on another. Abortion and incomplete development also were major factors in the production of sound seed. Populations of white fir cone and seed insects varied with cone crop but also were affected by the occurrence of cone crops on alternate hosts. During most years, the seed-mining guild insects were the major cause of seed damage.

Interactions among phytophagous insect species colonizing cones of white fir (Abies concolor).

The insect complex colonizing white fir (Abies concolor [Gord. and Glend.] Lindl.) cones is composed of eleven species that can be separated into three feeding guilds: the seed-mining guild, Megastigmus pinus Parfitt, M. rafni Hoffmeyer, Earomyia abietum McAlpine; the cone-and seed-mining guild, Dioryctria abietivorella Grote, Eucosma prob. siskiyouana (Kearfoot), Cydia prob. bracteatana (Fernald), Barbara sp.; the scale-and bract-feeding guild, Asynapta hokinsi (Felt), Dasineura prob. abiesemia Foote, Ressiliella conicola (Foote), Lasiomma abietis Huckett). In three of four study sites the cone crop decreased from one year to the next. As cone crop size decreased there was a concomitant increase in the percent of cones with more than one species. In addition, there was a shift toward an increased co-occurrence of members of different guilds within a single cone. Both positive and negative interactions were detected between selected species-pairs. Present-day competition was only inferred between species-pairs belonging to the cone and seed-mining guild. Decreasing resources over time, combined with increasing insect populations and the absence of acceptable alternate hosts appeared to be important factors for setting conditions conducive to interspecific competition. It is hypothesized, that the aperiodicity of white fir cone crops was important in keeping insect populations below levels which would result in interspecific competition. The possible elimination of aperiodicity in cone crops of white fir, such as might occur in managed seed orchards, may lead to decreased species diversity via competitive exclusion and thereby simplify development of IPM programs.

Trunk-Implanted Acephate to Protect Douglas-Fir Seed Crops on Individual Trees in Northern California

To reduce seed and cone insect damage, 0.875 g per capsule of acephate (technical grade) was implanted into individual Douglas-fir, Pseudotsuga menziesii (Mirb.) Franko, trees on 15 April or 6 May 1985. A spacing of one capsule per 10 cm of trunk circumference was used. Neither implant treatment affected actual infestation levels of a Douglas-fir cone gall midge, Contarinia oregonensis Foote, or a Douglas-fir seed chalcid, Megastigmus spermotrophus Wachtl. Both implant treatments, however, significantly reduced the damage of a fir coneworm, Dioryctria abietivorella (Grote), and the Douglas-fir cone moth, Barhara colfaxiana (Kearfott), by at least 62%. The latter implant significantly increased the number of filled seeds per cone by 154% compared with control trees, but the difference between implant treatment dates was not significant. Interspecific interaction between reduction of damage by Lepidoptera and the increase in C. oregonensis-damaged seeds and filled seeds suggests a negative association with reduced predation.

Protection of Disease-Resistant Western White Pine Seed from Insect Damage

Abstract Seed produced in blister rust-resistant western white pine (Pinus monticola Douglas) seed orchards is in high demand. The fir coneworm, Dioryctria abietivorella (Groté), and the lodgepole pine coneworm, Eucosma recissoriana (Heinrich), cause considerable damage to seed crops in the Moscow Arboretum seed orchard. Single (May or June) and repeated (May and June) applications of 0.025% fenvalerate, and repeated applications (May and June) of 0.0125% fenvalerate, a synthetic botanical insecticide, were evaluated in 1986 for protection of cone crops. Results in 1986 confirm results in 1984 (Haverty et al. 1986): an application of 0.025% fenvalerate in May and June significantly reduces insect damage, regardless of the relative abundance of cones or insects. The decision to use a single or repeated application depends on demand for seed, projected seed crop and insect populations, and socioeconomic costs of the treatment. West. J. Appl. For. 3(1):18-20, January 1988.

Single and Multiple Applications of Fenvalerate to Protect Western White Pine Cones from Dioryctria abietivorella (Lepidoptera: Pyralidae)1

Cones of blister rust-resistant western white pine were treated with highvolume ground applications of 0.025% fenvalerate during spring and summer 1984. Four treatments were compared: an untreated check, a single application (9 May), a double application (9 May and 13 June), and a triple application (9 May, 13 June, and 18 July). Dioryctria abietivorella (Grote) infested 46.6% of cones in the untreated check, significantly more than the 13.6% in the single application. The double application increased seed yield significantly compared to the untreated check from 31.3 to 56.0 seeds per cone. We are 95% confident that this treatment increased seed production by at least 30% and possibly as much as 128%. The third application in July was apparently unnecessary.

CONE AND SEED INSECTS IN DOUGLAS-FIR,PSEUDOTSUGA MENZIESII(MIRB.) FRANCO, SEED ORCHARDS IN THE WESTERN UNITED STATES: DISTRIBUTION AND RELATIVE IMPACT

AbstractDouglas-fir cones were collected from 17 seed orchards in California, Oregon, and Washington in the fall of 1983. Cones were completely dissected and seed losses ascribed to the Douglas-fir cone gall midge (Contarinia oregonensis(Foote)), the Douglas-fir seed chalcid (Megastigmus spermotrophus(Wachtl)), the Douglas-fir cone moth (Barbara colfaxiana(Kearfott)), and the fir coneworm (Dioryctria abietivorella(Groté)). There appear to be great differences between orchards, but overallC. oregonensisandM. spermotrophuscollectively destroyed approximately 70% of the filled seed. Physiographic province significantly (P<0.05) explained variation in damage by all insect species between seed orchards. In general, damage by all species increased from northern provinces to southern mountainous provinces. Damage byC. oregonensisandB. colfaxianaappeared to be related to land use or management factors, as well.

INSECTS AND MITES ASSOCIATED WITH WESTERN WHITE PINE BLISTER RUST CANKERS IN IDAHO

AbstractInsects present in western white pine blister rust cankers in northern Idaho were: two weevils, Cylindrocopturus n. sp. and Pissodes sp. near swartzi Hopk.; two bark beetles, Pityophthorus sp. near nitidulus (Mann.), and Procryphalus ? sp.; a drosophilid fly, Paracacoxenus guttatus Hardy and Wheeler; and a phycitid moth, Dioryctria abietivorella (Grote). Mites associated with insect infestation were: Lasioseius ? n. sp., Ameroseius longitrichus Hirschmann, and Histiogaster arborsignis Woodring.

Tests of Guthion for the Control of the Douglas-Fir Cone Midge1

Guthion® (O,O-dimethyl S-(4-oxo-1,2,3-benzotriazin-3-(4H)- ylmethyl) phosphorodithioate), used experimentally reduced the number of Douglas-fir cone midges (Contarinia oregonensis Foote) and cone moths (Dioryctria abietivorella Grote and Henricus fuscodorsana Kearfott) in the cones of Douglas fir. The effectiveness of this chemical increased with the amount of active ingredient applied per cone. At the highest rate of application, one well-timed spraying reduced the number of cone midges per cut face from 166 to 3 and the number of cone moths per one-half cone from 4 to none. Conelet abortion was reduced significantly over untreated controls. No adverse effect of the insecticide was recorded on Torymu8 sp., the principal parasite of the Douglas-fir cone midge.