Juli R. Gould

Field-cage methodology for evaluating climatic suitability for introduced wood-borer parasitoids: Preliminary results from the emerald ash borer system

Abstract Field-cage methods were developed to evaluate the abilities of Tetrastichus planipennisi Yang (Hymenoptera: Eulophidae) and Spathius agrili Yang (Hymenoptera: Braconidae), biocontrol agents of Agrilus planipennis Fairmaire (Coleoptera: Buprestidae), to parasitize, develop and overwinter following three late-season releases at both a northern (Michigan) and a southern (Maryland) location within the current North American range of A. planipennis. In August, September and October of 2009, five young green ash trees were selected at each location. Tetrastichus planipennisi and S. agrili were each randomly assigned to one of two cages attached to each tree, surrounding separate sections of trunk in which late-instar A. planipennis had been inserted. The following April, the caged trunk sections were dissected to determine the fate of each A. planipennis larva and the developmental stages of all recovered parasitoid progeny. At both locations, T. planipennisi and S. agrili were able to parasitize hosts and successfully overwinter (i.e., reach adulthood the following spring). For T. planipennisi, successful parasitism (i.e., parasitoid progeny reached adulthood) occurred for all caged releases in Maryland, but only for the August and September releases in Michigan. At both locations, percent parasitism by T. planipennisi was higher in August and September than in October. For S. agrili, successful parasitism occurred for all caged releases in Maryland, but only for the August release in Michigan. In Maryland, percent parasitism by S. agrili in August and September was higher than in October. The caging method described here should be useful in determining the climatic suitability of other regions before proceeding with large-scale releases of either species and may have utility in other wood-borer parasitoid systems as well.

Parasitoid Mark-Release-Recapture Techniques-- II. Development and Application of a Protein Marking Technique for Eretmocerus spp., Parasitoids of Bemisia argentifolii

In this study, we validate and apply techniques for marking and capturing small parasitoids of the silverleaf whitefly, Bemisia argentifolii Bellows & Perring [ = B. tabaci (Gennadius), strain B] for mark-release-recapture (MRR) studies. The marker is the purified protein, rabbit immunoglobulin G (IgG), which was applied externally by topical spray or internally by feeding. Marked parasitoids were then assayed using a sandwich enzyme-linked immunosorbent assay (ELISA) for the presence of the protein marker using an antibody specific to rabbit IgG. Virtually all of the externally marked Eretmocerus sp. (Ethiopia, M96076) (98.0%) contained enough rabbit IgG to be easily distinguished from unmarked parasitoids, regardless of the amount of protein applied or the post-marking interval. A field MRR study was then conducted to examine the dispersal characteristics of E. emiratus Zolnerowich & Rose. Parasitoids marked externally and internally with protein were released on three separate trial dates into the center of a cotton field bordered by cantaloupe and okra. Overall, a total of 1388, 637, and 397 marked and unmarked wasps were captured in suction traps during each trial, respectively with the majority of parasitoids captured between 0600 and 0800 h. Furthermore, even though we released an equal proportion of males to females, our traps consistently contained more males. Our results suggest that there are gender-specific differences in the dispersal behavior of E. emiratus . Almost 40% of the captured parasitoids collected during the three release trials were positively identified for the presence of the protein marker. The distribution of the marked parasitoids revealed two distinct patterns. First, almost all of the marked parasitoids recaptured in the cotton plot were in suction traps at or adjacent to the

Natural enemies implicated in the regulation of an invasive pest: a life table analysis of the population dynamics of the emerald ash borer

The emerald ash borer Agrilus planipennis Fairmaire is a serious invasive forest pest of ash (Fraxinus) trees in North America. Life tables were constructed for both experimentally established cohorts and wild populations of A. planipennis on healthy host trees from 2008 to 2011 in six forests in central Michigan. Life table analysis showed that the net population growth rates (R0) for the experimental cohorts (16.0 ± 2.9) and associated wild A. planipennis (19.4 ± 1.9) were the highest for the first study period (2008–2009) at three Ingham Co. sites but decreased to 4.7 ± 0.9 and 4.6 ± 0.4, respectively, for the second (2009–2010) study period at the same sites. By contrast, R0 values of both experimental cohorts (5.7 ± 2.2) and associated wild A. planipennis populations (11.3 ± 2.5) were intermediate in the third (2010–2011) study period at different sites in the Gratiot and Shiawassee Cos. The sudden decrease in R0 of both experimental and wild A. planipennis cohorts in the Ingham Co. sites corresponded with increases in parasitism by hymenopteran parasitoids Atanycolus spp. (native) and Tetrastichus planipennisi Yang (introduced), as well as an increase in woodpecker predation, indicating the role of these natural enemies in regulation of the pests population dynamics.

Effects of rearing conditions on reproduction of Spathius agrili (Hymenoptera: Braconidae), a parasitoid of the emerald ash borer (Coleoptera: Buprestidae).

ABSTRACT Spathius agrili Yang (Hymenoptera: Braconidae) can be successfully reared on emerald ash borer, Agrilus planipennis Fairmaire (Coleoptera: Buprestidae), larvae feeding in chambers drilled in small ash twigs that are wrapped with floral tape. Females maintained in groups with males for one week can receive enough sperm for production of female progeny throughout their lives. Volatiles released by emerald ash borer adults feeding on ash foliage increased parasitoid fecundity over ash foliage alone or no stimulus. The temperature at which the parasitoids were reared ranged from 20 to 25°C in a daily cycle; however, raising the daily maximum temperature to 28°C did not affect parasitoid longevity or fecundity. Adult females lived between 12 and 127 d, with an average of 60.8 ± 4.5 d. Males lived slightly longer, with an average of 66 ± 4.5 d. The first clutch of eggs was laid when the female was between 2 and 42 d old, with the average preoviposition period lasting 11.4 ± 1.4 or 19.5 ± 2.0 d in 2007 and 2009 trials, respectively. A higher proportion of the emerald ash borer larvae were feeding and thus attractive to parasitoids in the 2009 trial, and female S. agrili laid an average of 9.5 ± 1.0 clutches containing 5.4 ± 0.2 eggs, for an average of 51.2 eggs per female. Approximately three quarters of the progeny were female. The number of eggs per clutch was significantly greater when deposited on larger emerald ash borer larvae, further highlighting the need for quality larvae in rearing. Chilling S. agrili pupae at 10°C to stockpile them for summer release was not successful; chilling resulted in lower survival and lower fecundity of emerging progeny. Female S. agrili proved capable of attacking emerald ash borer larvae through even the thickest bark of an ash tree that was 30-cm diameter at breast height. Even emerald ash borer larvae that were creating overwintering chambers in the outer sapwood of the tree were successfully attacked, suggesting that S. agrili could be reared on field collected logs infested with emerald ash borer.

Effect of Temperature on Development and Population Parameters of Copitarsia decolora (Lepidoptera: Noctuidae)

Abstract The objective of this study was to evaluate the effect of temperature on survival, development, and reproduction of Copitarsia decolora. Both linear and nonlinear models were used to model temperature-dependent development and population growth for C. decolora reared on asparagus and artificial diet. We used @Risk Software to bootstrap model parameters so that variability in observations could be incorporated into model predictions. C. decolora eggs required ≈69 DD to complete development with a base temperature of 7.8°C. C. decolora developed through four to six instars depending on temperature and food source. Development of larvae from neonate through prepupa required 341.4 DD above a base of 7.3°C on asparagus, whereas 254.5 DD were needed on artificial diet, where the base temperature was 7.7°C. Pupae required ≈236 DD (base temperature 8.2–8.4°C) to develop when reared on asparagus or artificial diet. Female moths laid significantly more eggs at 14.6 and 20.1°C than at higher or lower temperatures. Survival of individuals to the adult stage increased from 71% at 9.7°C to 93% at 24.9°C. Survival fell off rapidly to 25% at 29.5°C. The generation time was the shortest at 29.5°C; however, only 25% of females survived to the adult stage, fecundity was low, and only 53% of the eggs hatched. The capacity for increase, rc, was low at 9.7°C, peaked at 25.7°C, and declined as temperature increased. We estimated that populations on asparagus would not develop at temperatures >31.3°C or <6.9°C. We show the importance of estimating a range of values for base temperature and degree-days by conducting a preliminary pathway analysis that incorporates the effect of temperature on egg hatch.

A New Species of Sclerodermus (Hymenoptera: Bethylidae) Parasitizing Agrilus planipennis (Coleoptera: Buprestidae) from China, with a Key to Chinese Species in the Genus

ABSTRACT A new parasitoid reared from Agrilus planipennis Fairmaire (Coleoptera: Buprestidae), Sclerodermas pupariae n. sp. (Hymenoptera: Bethylidae), is described from China. S. pupariae was reared from A. planipennis in China attacking velvet ash (Fraxinus velutina Torr. ), a tree native to North America. Life-history studies of S. pupariae in the field and laboratory indicated it is a gregarious idiobiont ectoparasitoid of pupa and larva of A. phnipennis and has up to five generations per year. Parasitism rate in the field was 13%. Adult wasps reared from single host pupa or mature larva ranged from 24 to 56 individuals. Based on laboratory rearing, the emerging adult female to male ratio was 22:1. The new parasitoid species has a high potential as a biocontrol agent for emerald ash borer. Diagnosis of the new species with comparisons to Sclerodermas harmandi (Buysson) and a key to Sclerodermas known in China are provided.

A pest risk assessment for Copitarsia spp., Insects associated with importation of commodities into the United States

SummaryEggs and larvae of Copitarsia spp. (Lepidoptera: Noctuidae) are frequently intercepted on fresh commodities arriving in the United States from Mexico, Central America, and South America. Copitarsia spp. are not known to occur in the US and, thus, are considered actionable pests by the US Department of Agriculture, Animal and Plant Health Inspection Service (USDA, APHIS). Whenever the genus is detected in imported goods, shipments must be disinfested, destroyed, or returned to the country of origin. Inspections and interdictions might be unnecessary if Copitarsia spp. were unlikely to establish in the US or if consequences of Copitarsia establishment were trivial. Consequently, we prepared a qualitative pest risk assessment to characterize the degree of risk posed by the genus to US agricultural and natural ecosystems. Published literature was consulted to describe the biology and ecology of the genus. Trade statistics and interception records were summarized to identify pathways of introduction. With this information, experts assigned risk ratings to each of eleven elements identified by USDA, APHIS that pertained to the likelihood or consequence of exotic-pest establishment. The likelihood of Copitarsia spp. becoming established in the US was considered high, but confidence in this assessment was low. Similarly, consequences of Copitarsia establishment were rated high, but confidence in this assessment was moderate. Overall, the assessment revealed that Copitarsia pose a high degree of risk to the US and phytosanitary measures to exclude the pest seem warranted. However, additional research is needed to address critical data gaps and refine assessments of risk for individual species within the genus.

Effects of Host Plant and Larval Density on Intraspecific Competition in Larvae of the Emerald Ash Borer (Coleoptera: Buprestidae)

ABSTRACT Competition for food, mates, and space among different individuals of the same insect species can affect density-dependent regulation of insect abundance or population dynamics. The emerald ash borer, Agrilus planipennis Fairmaire (Coleoptera: Buprestidae), is a serious invasive pest of North American ash (Fraxinus spp.) trees, with its larvae feeding in serpentine galleries between the interface of sapwood and phloem tissues of ash trees. Using artificial infestation of freshly cut logs of green ash (Fraxinus pennsylvanica Marshall) and tropical ash (Fraxinus uhdei [Wenzig] Lingelsh) with a series of egg densities, we evaluated the mechanism and outcome of intraspecific competition in larvae of A. planipennis in relation to larval density and host plant species. Results from our study showed that as the egg densities on each log (1.5–6.5cmin diameter and 22–25cmin length) increased from 200 to 1,600 eggs per square meter of surface area, larval survivorship declined from ≈68 to 10% for the green ash logs, and 86 to 55% for tropical ash logs. Accordingly, larval mortality resulting from cannibalism, starvation, or both, significantly increased as egg density increased, and the biomass of surviving larvae significantly decreased on both ash species. When larval density was adjusted to the same level, however, larval mortality from intraspecific competition was significantly higher and mean biomasses of surviving larvae was significantly lower in green ash than in tropical ash. The role of intraspecific competition of A. planipennis larvae in density-dependent regulation of its natural population dynamics is discussed.

Cost–Benefit Analysis for Biological Control Programs That Targeted Insect Pests of Eucalypts in Urban Landscapes of California

ABSTRACT As well as being planted for wind breaks, landscape trees, and fuel wood, eucalypts are also widely used as urban street trees in California. They now are besieged by exotic insect herbivores of four different feeding guilds. The objective of the current analysis was to determine the return on investment from biological control programs that have targeted these pests. Independent estimates of the total number of eucalypt street trees in California ranged from a high of 476,527 trees (based on tree inventories from 135 California cities) to a low of 190,666 trees (based on 49 tree inventories). Based on a survey of 3,512 trees, the estimated mean value of an individual eucalypt was US

Mass-Rearing Bemisia Parasitoids for Support of Classical and Augmentative Biological Control Programs

5,978. Thus, the total value of eucalypt street trees in California ranged from more than US