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► Nemorilla pyste is a tachinid parasitoid that oviposits onto hosts. ► Nilea erecta is a tachinid parasitoid that ovolarviposits onto substrate around hosts. ► The influence of host ...density on parasitoid fertility and host mortality was examined. ► Species had similar fertilities, but N. erecta caused higher host mortality. ► Increased host mortality from N. erecta was attributed to superparasitism.
This study examined fertility of the tachinid (Diptera) parasitoids Nemorilla pyste (Walker) and Nilea erecta (Coquillett), and mortality of the host, Choristoneura rosaceana (Harris) (Lepidoptera: Tortricidae). These are common parasitoids of mature C. rosaceana larvae in apple and sweet cherry orchards in central Washington where C. rosaceana is an important pest. The parasitoids have similar phenology and use the same stages of the host, but their modes of attack and development in the host differ. N. pyste oviposits on the host and develops gregariously, while N. erecta ovolarviposits on foliage near the host and develops solitarily. Life tables were used to compare adult longevity and fertility of these flies at three different host densities in laboratory cage experiments. Results suggested that although population growth rates of these species were similar under the experimental conditions, N. erecta had a greater effect on mortality of the host population. This additional mortality was attributed to superparasitism because it occurred in host larvae at a higher rate than expected from natural causes, and it occurred more frequently when fewer hosts were available to N. erecta females. A supplemental experiment demonstrated that host larvae that were manually infected with N. erecta maggots to simulate superparasitism expressed high rates of larval mortality. Thus, even though N. erecta had a greater effect on the host population, reproductive opportunity was lost to superparasitism. These findings may demonstrate certain situational disadvantages of ovolarviposition as a reproductive strategy, and illustrate how parasitism effects may be underestimated in field sampling.
Abstract
Halyomorpha halys (Stål), the brown marmorated stink bug, is a globally invasive stink bug species. Its first major outbreak was in the United States, where it has caused millions of dollars ...in damage, threatened livelihoods of specialty crop growers and impacted row crop growers, and become an extreme nuisance pest in and around dwellings. The BMSB IPM Working Group, funded by the Northeastern IPM Center, was central to providing a mechanism to form a multidisciplinary team and develop initial and subsequent research, Extension, regulatory and consumer priorities. Ultimately, a project team consisting of over 50 scientists from 11 institutions in 10 states obtained the largest ever USDA-NIFA Specialty Crop Research Initiative CAP grant, totaling over $10.7 million, to tackle this crisis over a 5-yr period (2011–2016). Researchers and Extension educators integrated stakeholder feedback throughout the course of the project, and priorities evolved according to needs of affected growers and public stakeholders. Initially, the team focused on identification of H. halys, its damage symptoms and crop-specific risks, and short-term mitigation strategies for crop protection. Subsequently, work focused on its biology, ecology, and behavior leading to the development of potential longer-term IPM tactics and landscape level management solutions, including biological control. This work continues under a second SCRI CAP grant (2016–2021). The information from the initial team reached an estimated 22,000 specialty crop stakeholder contacts via Extension efforts, and over 600 million people via mainstream media. We highlight the main lessons learned from coordinating a national response to the threat posed by H. halys to agriculture in the United States.
Reproductive biology, including mode of attack and egg maturation, has not been described for the leafroller (Lepidoptera: Tortricidae) parasitoids Nemorilla pyste (Coquillett) and Nilea erecta ...(Walker) (Diptera: Tachinidae). Mode of host attack is an important character for understanding evolutionary relationships in Tachinidae, and is an important consideration for biological control. In parasitic Hymenoptera, egg maturation strategy is predictive of many life-history variables, but these predictions have not been tested in other parasitoid groups. In this article, observations on the mode of attack of N. erecta and N. pyste that were acquired through the rearing of these species in the laboratory are described. The study also used dissections to examine internal reproductive physiology and obtain fecundity data for flies of different ages. Fecundity data from the dissections and from cage experiments were used to estimate the ovigeny index of the two species. N. pyste was found to be a highly synovigenic oviparous species, whereas N. erecta was found to be moderately synovigenic and ovolarviparous. Life-history associations of hymenopteran parasitoids with egg maturation strategy appeared not to apply to these tachinids.
Delay of mating was examined as a possible mechanism for population decreases associated with mating disruption for codling moth, Cydia pomonella L., and obliquebanded leafroller, Choristoneura ...rosaceana (Harris) (Lepidoptera: Tortricidae). We examined the effect of delaying female mating 0, 2, 4, or 6 d while holding male age constant on life table parameters of both species. We found that increasing delays in mating were accompanied by two responses: (1) an increase in the percentage of sterile pairs and (2) a reduction in net reproductive rate and population growth unrelated to sterility. On a percentage basis, obliquebanded leafroller population growth was more strongly affected than codling moth. However, the net fertility rate of obliquebanded leafroller was nearly eight-fold higher than that of codling moth, so that obliquebanded leafroller females that experienced a 4-d delay in mating had nearly the same reproductive rate as codling moth females that experienced no delay. Leslie matrix simulations using life tables with field-based adult longevity estimates showed that codling moth females experiencing >2-d delay in mating resulted in decreases in population density or extinction within two generations. In contrast, obliquebanded leafroller females delayed <6 d showed rapid population growth that decreased as female age at mating increased; only the 6-d delay treatment resulted in decreased population levels. Our results indicate that obliquebanded leafroller females must on average experience a much longer delay in mating to significantly reduce population growth compared with codling moth females, suggesting that delay of mating likely plays a greater role in codling moth mating disruption than for obliquebanded leafroller.
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•Populations of two parasitoids of Drosophila suzukii were tested under laboratory conditions.•Only the Italian population of Leptopilina heterotoma parasitized D. suzukii.•Italian ...and North American populations of Pachycrepoideus vindemiae parasitized D. suzukii.•Host pupal preference and lifetime fecundity of P. vindemiae were determined.•A third parasitoid species, Trichopria drosophilae, showed the ability to parasitize D. suzukii.
Drosophila suzukii (Matsumura) (Diptera: Drosophilidae) causes severe damage to certain fruit crops in both North America and Europe. This may be due, in part, to the absence of specialized natural enemies that suppress population outbreaks. We performed a series of experiments under controlled laboratory conditions in tandem with a field study to evaluate the presence and efficacy of natural enemies associated with this pest in Italian and western United States fruit production regions. Our study involved one larval parasitoid, Leptopilina heterotoma (Thomson) (Hymenoptera: Figitidae), and two pupal parasitoids, Pachycrepoideus vindemiae (Rondani) (Hymenoptera: Pteromalidae) and Trichopria drosophilae (Perkins) (Hymenoptera: Diapriidae). Three indices were used to describe host-parasitoid interactions: degree of infestation (DI), success rate of parasitism (SP) and total encapsulation rate (TER). Results confirmed that each of these parasitoid species can develop on certain populations of the pest. In addition, host stage preferences of the tested parasitoid populations, developmental parameters and lifetime fecundity of North American P. vindemiae are provided. Results are discussed with respect to differences in potential utilization of D. suzukii among the tested parasitoid species and regional populations.
In this study, the passage of spermatophores was examined between 1-day-old males mated in no-choice situations with females 0, 2, 4, or 6 days old and the converse for both the codling moth, Cydia ...pomonella (L.) (Lepidoptera: Tortricidae), and the obliquebanded leafroller, Choristoneura rosaceana (Harris). For C. pomonella, female age had no effect on the passage of spermatophores from males, and only 6-day-old female C. rosaceana had reduced spermatophore number. The ages of moths at the time of mating had a greater effect on males, with C. pomonella males older than 2 days showing significant reductions in the ability to successfully pass a spermatophore to 1-day-old females. For C. rosaceana, 2- and 6-day-old males were significantly less likely to pass a spermatophore, but reduced transfer from 4-day-old males did not reach statistical significance. Wind-tunnel assays were used to evaluate the ability of 1- or 4-day-old males to fly upwind and successfully contact a young calling female. Four-day-old males were more likely to initiate flight upwind, but were less efficient at finding and contacting the females than younger males. This study suggests that evaluation of multiple components of the mating process are required to understand the effect of age at the time of mating on population dynamics of these moths.
Bacterial blight (
Xanthomonas arboricola
pv
. corylina
(
Xac
)) of hazelnut (
Corylus avellana
L.) was described first in Oregon in 1915 and is now recognized as a damaging disease of young hazelnut ...trees worldwide. Thousands of hectares of new hazelnut cultivars that are resistant to eastern filbert blight (
Anisogramma anomala
) are being planted in the Willamette Valley of Oregon, where 99% of the US hazelnut crop is grown. Reports of bacterial blight on young hazelnut trees have increased but information about the causal pathogen is limited. Isolates were recovered from tissues with bacterial blight symptoms that were then characterized for their ability to grow on semi-selective media, their nutrient utilization profiles using Biolog GN2, quinate metabolism, copper tolerance, hypersensitive response on tobacco, and pathogenicity on hazelnut. Additionally, isolates were identified with a duplex PCR assay (
ftsX
and
qumA
), 16S rRNA sequence, and multi-locus sequence analysis (MLSA) using
rpoD
and
gyrB
. Pathogenic isolates were identified as
Xac
using morphological, biochemical, molecular, and host assays. Using MLSA,
Xac
isolates from Oregon separated into two clades, one clade with the type strain and a second clade previously described using isolates from Europe. The phylogenetic diversity of
Xac
observed in other countries also is present in Oregon.
Abstract
Brown marmorated stink bug,
H
alyomorpha haly
s (
S
tål) (
H
emiptera:
P
entatomidae), has become a major pest for agricultural growers since it arrived in the
USA
and Europe. To better ...understand the energetic requirements of overwintering, dispersal, and reproduction of this invasive pest, we monitored the weight, egg load, lipid, glycogen, and sugar levels of adult
H
. halys
populations in western Oregon,
USA
, over 2 years. In the first study, overwintering
H
. halys
collected monthly from inside shelters exhibited a consistent decline in weight, glycogen, and sugar levels from October to June. In the second study, post‐overwintering adults that exited shelters in late spring had lower lipid, glycogen, and sugar levels than those that exited in early spring. Also, adults that just exited shelters had lower weight, glycogen, sugar, and sometimes lipids than adults that remained in diapause. Sugar levels declined the most during winter, followed by lipid and glycogen. These findings suggest that nutritional depletion may cause
H
. halys
to emerge from diapause. In the third study, overwintered and first‐generation adults (G
1
) were simultaneously collected from holly in July and August. Overwintered adults often had lower nutrient levels than G
1
adults, which may reflect overwintered adults having expended energy for dispersal and reproduction. In the fourth study, we evaluated whether the Nutrient Index weight (mg)/prothorax width (mm)
3
, a convenient index of physiological status, correlated with nutrient reserves. The Nutrient Index correlated with the adults’ lipid, glycogen, or sugar levels in 57% of cases, ranging from weakly negative to moderately positive correlations.
The longevity of adult codling moth (Cydia pomonella (L.) Lepidoptera: Tortricidae) and obliquebanded leafroller (Choristoneura rosaceana (Harris) Lepidoptera: Tortricidae) held in shaded vials in ...the tree canopy was measured during the normal flight periods during 2004 and 2005. In both years all codling moths were dead by 130 degree-days (DD) (21 d) in the spring and 121 DD (8 d) in the summer. On a degree-day basis, data were similar across sex, generation, and year, and a common curve adequately predicted the survival distribution. For the obliquebanded leafroller, there were longevity differences between the sexes, but not between generations or years. Use of empirical quantile-quantile plots showed that the female obliquebanded leafroller lived an average of 32% longer than males. Maximum longevity observed in these studies for obliquebanded leafrollers was 117 DD (11 d) across both generations. The implications of these data for population biology studies and quarantine requirements are discussed.
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