Effect of host egg viability on reproduction and development of Trichogramma cacoeciae and T. principium (Hymenoptera: Trichogrammatidae)

A combination of a sterile insect technique, resulting in infertile eggs, and of an egg parasitoid, should provide better control of codling moth than either alone. Non-choice laboratory experiments were conducted with infertile and fertile codling moth eggs to evaluate the potential parasitism and reproduction of Trichogramma cacoeciae Marchal and T. principium Sug. et Sor. The tendency of T. cacoeciae females to attack infertile eggs was similar to that for fertile eggs, whereas T. principium showed a greater preference for infertile eggs than fertile eggs. The fertility status of the host did not affect the number of eggs that were parasitized but fewer F₁ progeny emerged from infertile eggs when parasitized than from fertile eggs. When T. cacoeciae and T. principium parasitized infertile host eggs their mean developmental time was prolonged but the viability and quality of parasitoid progeny was not influenced by the fertility status of the host eggs. The study demonstrates the compatibility of use of T. cacoeciae and T. principium in an integrated program employing the sterile insect technique for codling moth management.     

Effects of changes in temperature and saturation deficit on the survival of eggs of Trichostrongylus colubriformis (Nematoda: Trichostrongylidae)

and 1972. Effects of changes in temperature and saturation deficit on the survival of eggs of Trichostrongylus colubriformis (Nematoda: Trichostrongylidae) International Journal for Parasitology, 2: 439–447. In conformity with a hypothesis relating to survival of the developing T. colubriformis egg exposed to desiccation, samples of eggs initially at the early blastomere stage of development showed decreased mortality during development with increasing temperature of incubation up to 25°C, for approximately constant rates of evaporation. At 30°C there was a higher percentage mortality for fixed evaporation rate than at 20° or 25°C. It is suggested that at 30°C there may be an abrupt increase in the initial rate of water loss from the developing embryo resulting from a change in the permeability to water of the lipid layer of the egg envelope.

Fully embryonated T. colubriformis eggs were obtained by incubation at 20°C in the presence of a moderate saturation deficit during development. When such eggs were transferred to 30° and 40°C there was no mortality at the higher temperature, providing that the saturation deficit was substantially increased. A hypothesis proposed for survival at high temperature is based on analogy with water loss through the arthropod cuticle and is attributed to a decrease in permeability of the protein-chitin layer of the egg envelope under conditions of high evaporation rate, even though permeability of the lipid layer might be increased by high temperature.     

Comparison of different European strains of Trichogramma aurosum (Hymenoptera: Trichogrammatidae) using fertility life tables

Life table parameters were assessed for seven strains of Trichogramma aurosum Sugonjaev and Sorokina (Hymenoptera: Trichogrammatidae) collected in different European countries, in order to compare their performance when reared on eggs of Ephestia kuehniella Zeller (Lepidoptera: Pyralidae) as a potential factitious host for mass-rearing. The average number of progeny per female, cumulative fertility and emergence rate did not differ significantly, whereas female longevity and sex ratio significantly differed between the seven parasitoid strains. The Danish strain survived the longest (6.05 days) and the Dutch strain survived the shortest (2.75 days). Progeny was always female-biased with varying proportions (57.7-96.7%). Survival rates started to decrease after 3 days for some of the strains studied. The mean cohort generation duration (T_c) was 11.40, 10.15, 10.62, 10.63, 9.28, 9.70 and 11.30 days for the Austrian, Luxemburgian, Belgian, French, Dutch, Danish and German strains, respectively. Population doubling time (D_t) was 4.50, 7.96, 3.56, 5.30, 5.23, 7.36 and 3.30 days, respectively. Daily intrinsic rate of increase (r_m) and finite rate of increase (exp. r_m) ranged between 0.087 and 0.210 and 1.091-1.233, respectively. The German strain might be a potential candidate for mass rearing and releases against the codling moth, Cydia pomonella (L.) (Lepidoptera: Tortricidae), due to its high net reproduction rate (R₀=10.65 female), a high intrinsic rate of natural increase (r_m=0.210), a high finite rate of increase (exp. r_m=1.23), and a short population doubling time (D_t=3.3 days). The relevance of intra- and interstrain variability as well as the usefulness of fertility life tables for pre-introductory research is discussed.     

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.     

Changes in Biological Characteristics of Trichogramma pretiosum (Hym.: Trichogrammatidae) Reared on Eggs of Anagasta kuehniella (Lep.: Pyralidae) for 23 Generations

Possible changes in biological characteristics of Trichogramma pretiosum (Riley) (Hymenoptera: Trichogrammatidae) were monitored during 23 generations reared on eggs of Anagasta kuehniella (Zeller) (Lepidoptera: Pyralidae), to determine quality control parameters in rearing procedures of this parasitoid. Parasitism rates (percent of eggs parasitized) of T. pretiosum varied from 10 to 76%, with lower values for the first four generations. From the 17th generation, the variability in the parasitism rate was lower. Viability (percent adult emergence rate) of T. pretiosum in eggs of A. kuehniella varied from 22 to 100%, again with lower values in earlier generations. Adult longevity of T. pretiosum varied from 5.3 to 15.9 days, and showed a reduced longevity with increasing number of generations. Sex ratio of the offspring of this parasitoid was not affected by the timing of parasitism on eggs of A. kuehniella.     

中国东北地区芽孢盘菌属的研究

本文报导了中国东北地区芽孢盘菌属(Tympanis)5个种1变种, 其中1个新种(T.tiliae Xiang et Soing)4个国内新记录种(T.confusa Nyl., T.abietina Groves, T.piceina Groves, T.alnea(Pers.)Fr.)1个国内新记录变种(T.alnea var.hysterioides Rehm)以上各种都进行了形态和培养特性的研究, 还用Koch's证病法则证明了T.confusa是引起红松流脂溃疡病的病原菌, 并在松脂上伴生Sarea resinae(Fr.ex Fr.)Kuntze.     

Pollen as a source of food for egg parasitoids of the genus Trichogramma (Hymenoptera: Trichogrammatidae)

The value of corn pollen as a food source for Trichogramma brassicae Bezdenko (Hymenoptera: Trichogrammatidae) was assessed in the laboratory by testing the effect of different pollen diets on the longevity, capacity of parasitism and other life-table parameters. T. brassicae females that fed on corn pollen and water (wet filter paper dusted with pollen) lived significantly longer (4.97 days) than females that fed on water alone (2.67 days), but significantly shorter than those feeding on honey alone (8.37 days) or corn pollen and honey (8.23 days), respectively, in the absence of host eggs. The presence of European corn borer eggs (Ostrinia nubilalis Huebner, Lepidoptera: Pyralidae) significantly increased longevity. With host eggs available, female T. brassicae that fed on corn pollen and water lived significantly longer (4.9 days) than on water alone (2.60 days), but significantly shorter than on honey alone (12.33 days) or corn pollen and honey (12.17 days), respectively. The cumulative lifetime fecundity was 82.53 offspring pupae when fed on pollen and water, which was significantly higher than 61.70 for water alone but lower than feeding on honey alone (95.70) or corn pollen and honey (99.97), respectively. Compared to water alone, corn pollen and water increased the net reproduction rate (R₀), intrinsic rate of increase (r_m), and finite rate of increase (λ), and reduced the doubling time (T₂), but had no effects on the emergence rate, sex ratio, and mean generation time (T_c). In another set of experiments, 13 out of 30 females reduced the number of pollen grains offered to them. The average number of pollen grains utilized per female in this 48-h test 2.46±0.40 (mean±SE). Hence, T. brassicae used corn pollen as food that significantly increased longevity and fecundity of the tested females. Pollen and honey supplied a complete diet for T. brassicae, compared to pollen and water or water alone.     

The Influence of Host Species on Some Biological and Behavioural Aspects of Dibrachys boarmiae (Hymenoptera: Pteromalidae), Parasitoid of Kermania pistaciella (Lepidoptera: Tineidae)

Dibrachys boarmiae was recently found as a parasitoid of the pistachio twig borer moth, Kermania pistaciella, an important pistachio pest in Iran. Several biological and behavioural aspects of the wasp were studied under controlled conditions using three different lepidopterous host species, K. pistaciella, Sitotroga cerealella and Galleria mellonella. Development time from egg to adult decreases from 54 days at 15°C to 12.6 days at 32.5°C. The thermal constant was estimated 270°D, and the lower development threshold was at 9.9°C. Longevity of females that had the opportunity to oviposit and access to food (honey) was on average 23 days, and 134 offspring were produced during 13 days of oviposition. Ninety percent of ovipositions occur during the first 10 days of the parasitoid's life, although no pre-oviposition period was found. If females were deprived of food, longevity as well as fecundity, were drastically reduced to 8 days and only 79 offspring respectively. Females were able to mate immediately after emergence and the sex ratio of the progeny was strongly female biased on all examined hosts, especially on the largest host G. mellonella (0.08 male). When females were kept with a male throughout their life, the total number of progeny decreased to 92 wasps on average but the sex ratio was unaffected. The parasitoid significantly preferred to attack the pre-pupal stage, and this influenced the size of clutches allocated to different host stages. The parasitoid laid larger clutches on bigger hosts.     

A biological assessment of Apophua simplicipes (Hymenoptera: Ichneumonidae) as a parasitoid of the oblique banded leafroller, Choristoneura rosaceana (Lepidoptera: Tortricidae)

Apophua simplicipes (Cresson) (Hymenoptera: Ichneumonidae) is a common parasitoid of the oblique banded leafroller, Choristoneura rosaceana (Harris) (Lepidoptera: Tortricidae) in organically managed apple orchards in the southern interior of British Columbia, Canada. The biological characteristics of a laboratory colony of A. simplicipes were studied. When held at 15 and 25°C and provided with honey water, individual females survived an average of 60.6±6.1 and 29.8±4.7 days, oviposited 196.7±50.7 and 326.6±51.3 eggs and parasitized a total of 163.4±40.4 and 229.4±35.8 hosts, respectively. Females oviposited into first through fourth instar oblique banded leafrollers, with significantly more parasitism occurring in the first two instars compared to the third and fourth instars. No parasitoid larvae survived past the first larval stage in parasitized fourth instar hosts. Apophua simplicipes did not parasitize larvae of three-lined leafroller, Pandemis limitata (Robinson) (Lepidoptera: Tortricidae) which is sympatric with oblique banded leafrollers in orchards in the southern interior of British Columbia. Female predation and host feeding from wounds on early instars of both leafroller species was observed under laboratory conditions. In addition, early instar hosts exited diet feeding sites in response to the probing activity of the ovipositing wasps. A similar escape reaction in the orchard may cause a leafroller larva to move away from its feeding site, making it more vulnerable to predation or movement off the tree. Apophua simplicipes larvae emerged from fifth and sixth instar hosts. Parasitized oblique banded leafroller hosts consumed significantly less meridic diet than unparasitized female larvae from fifth instar through to parasitoid emergence or leafroller pupation. Our laboratory results suggest that A. simplicipes may reduce field populations of oblique banded leafroller and decrease pest feeding damage.     

Long-term benefits to the growth of ponderosa pines from controlling southwestern pine tip moth (Lepidoptera: Tortricidae) and weeds

The southwestern pine tip moth, Rhyacionia neomexicana (Dyar) (Lepidoptera: Tortricidae), is a native forest pest that attacks seedlings and saplings of ponderosa pine, Pinus ponderosa Dougl. ex Laws, in the southwestern United States. Repeated attacks can cause severe deformation of host trees and significant long-term growth loss. Alternatively, effective control of R. neomexicana, vegetative competition, or both in young pine plantations may increase survival and growth of trees for many years after treatments are applied. We test the null hypothesis that 4 yr of R. neomexicana and weed control with insecticide, weeding, and insecticide plus weeding would not have any residual effect on survival and growth of trees in ponderosa pine plantation in northern Arizona 14 yr post-treatment, when the trees were 18 yr old. Both insecticide and weeding treatment increased tree growth and reduced the incidence of southwestern pine tip moth damage compared with the control. However, weeding alone also significantly increased tree survival, whereas insecticide alone did not. The insecticide plus weeding treatment had the greatest tree growth and survival, and the lowest rate of tip moth damage. Based on these results, we rejected our null hypothesis and concluded that there were detectable increases in the survival and growth of ponderosa pines 14 yr after treatments applied to control R. neomexicana and weeds.     

Seasonal abundance, reproduction and development of four key copepod species on the Faroe shelf

The copepod community on the Faroe shelf is dominated by Calanus finmarchicus, Temora longicornis, Acartia longiremis and Pseudocalanus spp. The species composition, abundance and development of the copepod community varied considerably during the season 2004. These variations reflected to a large extent the different life strategies of the copepods. Both nauplii and copepodites of C. finmarchicus were most abundant during spring and early summer. The two neritic copepods T. longicornis and A. longiremis were present in low numbers during spring but dominated the copepod community later during the productive period. Pseudocalanus spp., on the other hand, occurred throughout the year, but showed no clear numerical response in abundance to the spring bloom. The egg production measurements of C. finmarchicus and T. longicornis showed some pre-bloom egg production, but as the spring bloom started the egg production rate increased significantly, especially for C. finmarchicus. There seemed to be a substantial loss of nauplii and copepods from the shelf ecosystem during the productive season. It was, however, not possible to determine whether this was mainly due to mortality or advective loss.     

Prey-Dependent Life Attributes of an Aphidophagous Ladybird Beetle, Propylea dissecta (Coleoptera: Coccinellidae)

Predation potential, development, immature survival and reproduction of an aphidophagous ladybeetle, Propylea dissecta (Mulsant) was studied when fed on seven aphid prey, viz. Aphis gossypii, Aphis craccivora, Lipaphis erysimi, Uroleucon compositae, Brevicoryne brassicae, Rhopalosiphum maidis and Myzus persicae. A. gossypii was most suitable and consumed by the larvae and adults of P. dissecta, while M. persicae, the least. Pre-imaginal development of P. dissecta was fastest (0.080 day^-1) when A. gossypii was used as prey, whilst slowest (0.061 day^-1) on M. persicae. The immature survival, adult emergence, adult male and female longevity of P. dissecta was maximal (i.e., 77.10±0.04 and 93.21±0.79%, 57.10±1.62 and 62.40±1.93 days, respectively) on A. gossypii and minimal (i.e., 63.01±1.87 and 81.73±1.79%, 42.50±1.21 and 49.40±2.32 days, respectively) when M. persicae was provided as prey. Oviposition period, fecundity, percent egg viability and mean reproductive rate was maximum (i.e., 50.30±2.03 days, 856.00±30.00 eggs, 96.40±0.31% and 17.02 eggs per day) on A. gossypii, and minimum (i.e., 18.00±1.40 days, 212.00±18.21 eggs, 72.46±2.81% and 11.78 eggs per day) on M. persicae. Adult weight and developmental rate of P. dissecta have a positive correlation, which suggests that if immature stages of ladybeetle developed faster, they should grow into heavier adults. Female longevity and fecundity also have a positive correlation. The findings also reveal that all seven aphid species tested are essential food. Rank order of prey species was consistent in all experimental parameters.     

Variation in the suitability of Pinus contorta (lodgepole pine) to feeding by three pine defoliators, Panolis flammea, Neodiprion sertifer and Zeiraphera diniana

A series of experiments were carried out on Pinus contorta Dougl. in Scotland to establish if there were any inter-provenance differences in suitability to three major forest pests: the pine beauty moth, Panolis flammea (D and S) (Lep., Noctuidae), the European pine sawfly, Neodiprion sertifer (Geoff.) (Hym., Diprionidae), and the larch bud moth Zeiraphera diniana Guennée (Lep., Tortricidae). There were significant differences in the survival, weight, and development time of P. flammea on different provenances of seedling logepole pine. Southern interior lodgepole pine (ILP) proved to be the most resistant provenance. Larvae performed significantly better on Alaskan lodgepole pine (ALP) and Skeena River lodgepole pine (ELP). Panolis flammea larvae showed significant feeding preference for certain provenances of mature lodgepole pine, with ILP being preferred to ALP, north coastal lodgepole pine, and Scots pine. There were significant differences in the mean relative growth rate of N. sertifer on different provenances of seedling and mature trees. ALP was the most resistant provenance among seedling trees, but the least resistant among mature trees. There were also significant differences in survival on foliage from mature provenances. There were no significant differences in survival of second instar Z. diniana on different provenances of mature lodgepole pine.     

Temperature-dependent Development of Four Egg Parasitoid Trichogramma Species (Hymenoptera: Trichogrammatidae)

Trichogramma species have been successfully utilized for biocontrol of several lepidopteran pests worldwide. The development, survival and progeny production of two Kenyan species' Trichogramma bournieri Pintureau & Babault and Trichogramma sp. nr. mwanzai Schulten & Feijen (collected from Kenya), Trichogramma evanescens Westwood (Germany) and Trichogramma chilonis Ishii (India) was studied at four constant temperatures (13, 18, 25 and 34°C) with the 011 aim of assessing the relative biotic potential of the two native species for 011 biocontrol of Helicoverpa armigera and Plutella xylostella in Kenya. The study was conducted at the Institute 011 for Biological Control (BBA), Darmstadt, Germany. The Trichogramma species tested showed variations 011 in fertility, developmental time, percent emergence, progeny production and sex ratio 011 at the four temperature regimes. Fertility decreased as temperature increased from 25 to 34°C. 011 T. chilonis and T. evanescens completed development at all temperatures tested, but T. 011 bournieri and T. sp. nr. mwanzai failed to complete development at 13°C. The developmental 011 period for all the species decreased as the temperature increased. The duration of development from 011 oviposition to adult emergence varied from 8 days to 12 weeks shorter at 34°C than at 011 13°C for T. chilonis and T. evanescens . For the various temperatures tested, a linear model was 011 satisfactory for egg to adult development at P = 0.05 for T. chilonis and T. evanescens . The 011 lower temperature thresholds for development and duration in degree-days were 8.83°C and 188 for 011 T. chilonis and 9.23°C and 192 for T. evanescens , respectively. For all temperatures tested, 011 T. sp. nr. mwanzai had the highest preimaginal survivorship. Adult emergence was lower at 13°C and 34°C than at 011 18 and 25°C. The highest fertility (mean ±SE) (50.37 ±2.32 adult 011 female -1 ) and progeny production (44.03 ±2.02 adult female -1 ) was recorded at 25°C for 011 T. evanescens . Sex ratio was biased towards female at all temperatures in T. bournieri and T. chilonis . 011 At all temperatures tested, T . sp. nr. mwanzai produced more males than females. For all species tested, 011 favourable parasitism was between 18 and 25°C. The results from this study will be useful for mass rearing purposes as well as for future field release programmes.     

Levels of damage of Scots pine and Norway spruce caused by needle miners along a SO2 gradient

Needle damages caused by mining insects on Scots pine and Norway spruce were studied in the vicinity or a pulp mill. The abundance of needles mined by the pine bud moth Exoteleia dodecella (Lepidoptera: Gelechiidae) on Scots pine Pinus sylvestris , and the spruce needle miner Epinotia tedella (Lepidoptera: Tortricidae) on Norway spruce Picea abies had a significantly peaked response curve on logarithmic distance scale. For pine bud moth, the maximum expected population density was estimated to be at the distance of 1.35 km from the factory. The maximum expected population density for the spruce needle miner was at the distance of 1.53 km from the factory. However, for both species the curves were significantly different among transects. Both species had a peaked and significant response to sulphur level in needles as well. The maximum expected density in pine was at 1270 ppm, and in spruce at 1070 ppm sulphur concentration in pine needles. The results are consistent with earlier reports demonstrating that these mining insects frequently attack trees suffering from air pollution. The nonlinear response of both species to distance from the pulp mill suggests that E. dodecella on pine and E. tedella on spruce are rather indicators of the zone of intermediate air pollution than of strongly polluted or nearly unpolluted sites. This also agrees with the plant stress-insect performance hypothesis indicating that insect response varies with the magnitude of stress, and at very high stress levels a tree no longer provides the insects with relevant food.     

Examination of sex attractants for monitoring weed biological control agents in Hawaii

The identification of sex attractants was undertaken for potential use in the study of two biological control agents against Rubus spp. in Hawaii. Attractants for Croesia zimmermani (Lepidoptera: Tortricidae) and Schreckensteinia festaliella (Lepidoptera: Heliodinidae) were developed by field screening a variety of putative lures in sticky traps, based on attractants for congeneric species. Croesia zimmermani was most attracted to E11-tetradecen-1-ol and E11-tetradecenal, while S. festaliella was attracted to (10,12)-(E,E)-hexadecadienal alone. Development of monitoring systems based on sex attractants can enable better evaluation of biocontrol programmes, and provide cost-effective information on presence/absence, density, phenology, synchrony with the host, dispersal rate and other useful parameters.     

Egg mortality in the cedar processionary moth,Thaumetopoea bonjeani (Lepidoptera: Notodontidae), in an outbreak area of Algeria

The cedar processionary moth, Thaumetopoea bonjeani (Lepidoptera: Notodontidae), is one of the most serious pests of Cedrus atlantica in north-western Africa (Algeria and Morocco). We report on T. bonjeani egg mortality and the diversity and abundance of parasitoids associated with its eggs in the area of Djurdjura Mountain (Tala-Guilef, Algeria). For this goal, 223 egg batches were collected from C. atlantica over two cohorts (2012 and 2013). The average number of eggs per egg batch increased from 143 in 2012 to 171 in 2013, while the egg mortality decreased from 47.4% and 23.9%, respectively, possibly because of a dilution effect. The most important factors of egg mortality were parasitoids and predators, with hymenopteran egg parasitoids killing from 12.1% to 34.9%, and predators from 5.2% to 7.4% of the eggs. The pattern of egg parasitism was driven largely by Ooencyrtus pityocampae, accounting for about 94% of the total parasitoids, followed by Baryscapus servadeii and Trichogramma embryophagum. An hyperparasitoid Chartocerus sp. was collected for the first time from eggs of Thaumetopoea species. As the two major egg parasitoids are shared with the pine processionary moth Thaumetopoea pityocampa in the same area, it is likely that parasitoid abundance may depend on the occurrence of both hosts.     

Loss of Symbiodinium from bleached soft corals Sarcophyton ehrenbergi, Sinularia sp. and Xenia sp.

The deleterious effects of temperature-induced coral bleaching, a process by which corals lose their endosymbiotic algae (zooxanthellae; genus Symbiodinium) primarily at temperatures above mean yearly maximums, has not been well described for alcyonacean soft corals (Coelenterata, Octocorallia). The study of Symbiodinium cells lost from Sarcophyton ehrenbergi, Sinularia sp., and Xenia sp., which have not been compared in bleaching studies, indicate that the soft coral S. ehrenbergi released the greatest number of symbiont cells, however, it was less susceptible to heat stress surviving temperatures of 34 °C for >39 h. Sinularia sp. showed intermediate levels of bleaching tolerance to elevated temperatures, surviving prolonged exposures at 32 °C, but dying within 24 h at 34 °C. Xenia sp., however, was the most vulnerable to high heat stress maximally releasing Symbiodinium at temperatures ≤30 °C. This evidence indicates that Xenia sp. is even more susceptible to elevated temperatures than Acropora spp., previously reported to be the most vulnerable coral species to elevated temperature-induced bleaching.

Molecular analysis showed that the more resistant soft coral species (S. ehrenbergi) had the same type of Symbiodinium (clade C) as less resistant soft corals (Xenia sp.). In comparison to scleractinian corals collected from the same region that show similar bleaching resistance to high temperatures (e.g. Porities solida—more robust; Favites complanata—moderate resistance; Acropora hyacinthus—less robust), all scleractinian corals were symbiotic with Symbiodinium from clade C. A. hyacinthus, however, was found to possess multiple symbionts (clades B and C), and this represents a first report of Clade B in any Acropora species.     

Operational considerations for augmentation of Trichogramma exiguum (Hymenoptera: Trichogrammatidae) for suppression of Rhyacionia frustrana (Lepidoptera: Tortricidae) in Pinus taeda plantations

Studies were performed to assess the operational feasibility of Trichogramma exiguum Pinto & Platner (Hymenoptera: Trichogrammatidae) augmentation for suppression of the Nantucket pine tip moth, Rhyacionia frustrana (Comstock) (Lepidoptera: Tortricidae), in commercial loblolly pine, Pinus taeda L., plantations. Single inundative releases containing two cohorts of encapsulated T. exiguum at a potential rate of 224,200 +/- 27,600 females per ha per cohort were made into two 4-ha plots during the second R. frustrana generation in 2000. Augmentation failed to increase parasitism rates above those occurring naturally; yet, 10% fewer shoots were attacked by R. frustrana, but not below acceptable levels. Quality control data suggest that low emergence levels and intense predation by ants upon developing T. exiguum lowered actual release rates to 13,000 +/- 900 females per ha per cohort. The effect of capsule distribution and microclimate on the discovery of capsules by predators (indicated by some E. kuehniella egg removal), parasitoid predation (percentage of eggs removed or destroyed), and subsequent parasitoid emergence was investigated. Uniformly distributed capsules experienced significantly higher predation levels than clustered capsules, and capsules exposed to field conditions for 5 d experienced higher predation than those exposed for 3 d, independently of distribution. Discovery of capsules by predators was unaffected by distribution or exposure period. Microhabitat significantly impacted average maximum daily temperature, the number of consecutive hours per day at or above 35 degrees C, and parasitoid emergence percentages. Parasitoid emergence declined significantly in response to increasing number of consecutive hours per day above 35 degrees C. Microclimate did not impact capsule discovery by predators or predation levels. Augmentation of T. exiguum for suppression of R. frustrana damage may not be practical within P. taeda plantations.     

Host status of fresh prunes by potential quarantine pests in laboratory tests and evaluation of packinghouse culls.

The status of fresh prunes, Prunus domestica L., as a host for codling moth, Cydia pomonella (L.) (Lepidoptera: Tortricidae); peach twig borer, Anarsia lineatella Zeller (Lepidoptera: Gelechiidae); omnivorous leafroller, Platynota stultana Walshingham (Lepidoptera: Tortricidae); oriental fruit moth, Grapholita molesta (Busck) (Lepidoptera: Tortricidae); navel orangeworm, Amyelois transitella (Walker) (Lepidoptera: Pyralidae); and walnut husk fly, Rhagoletis completa Cresson (Diptera: Tephritidae), was investigated in laboratory tests and by examination of packinghouse culls. In laboratory no-choice tests, the mean number of adults reared per fruit was 0.01 for codling moth, 0.08 for omnivorous leafroller, 0 for oriental fruit moth, and 1.6 for navel orangeworm. In choice tests the mean number of adults reared per apple or fresh prune was for codling moth, 0.78 and 0.02 (significantly different); for omnivorous leafroller, 0.05 and 0.02; and for oriental fruit moth, 2.07 and 0 (significantly different), respectively. Walnut husk fly oviposited in fresh prunes in no-choice tests but pupae did not develop from the fruit. In choice tests, walnut husk fly did not oviposit in fresh prunes when caged with its normal host, green walnuts, in which large numbers of pupae developed. Inspection of packinghouse culls for immature insects showed that fresh prunes with possible larval feeding sites in the form of frass or fruit gum extrusions were lighter in weight, significantly less firm, similar in color, and had significantly higher soluble solids than noninfested fruit. Based on packinghouse cull samples, 1 fresh prune per 133 harvested fruit would be expected to show possible insect damage. Eleven peach twig borer larvae were found in fresh prune cull samples (213.9 kg) removed from a 16,744.5-kg harvest. The calculated level of infestation was 1 infested fruit per 8,501.8 fruit harvested or per 21.7 cartons of medium-sized packed fruit. Based on our results, the risk of infestation of fresh prunes by the insects in this study would be minimal in fruit exported from the San Joaquin Valley of California.