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.
Brown marmorated stink bug, Halyomorpha halys (Stal), (Hemiptera: Pentatomidae) is an invasive polyphagous agricultural and urban nuisance pest of Asian origin that is becoming widespread in North ...America and Europe. Despite the economic importance of pentatomid pests worldwide, their feeding behavior is poorly understood. Electronically monitored insect feeding (EMIF) technology is a useful tool in studies of feeding behavior of Hemiptera. Here we examined H. halys feeding behavior using an EMIF system designed for high throughput studies in environmental chambers. Our objectives were to quantify feeding activity by monitoring proboscis contacts with green beans, including labial dabbing and stylet penetration of the beans, which we collectively define as 'probes'. We examined frequency and duration of 'probes' in field-collected H. halys over 48 hours and we determined how environmental conditions could affect diel and seasonal periodicity of 'probing' activity. We found differences in 'probing' activity between months when the assays were conducted. These differences in activity may have reflected different environmental conditions, and they also coincide with what is known about the phenology of H. halys. While a substantial number of 'probes' occurred during scotophase, including some of the longest mean 'probe' durations, activity was either lower or similar to 'probing' activity levels during photophase on average. We found that temperature had a significant impact on H. halys 'probing' behavior and may influence periodicity of activity. Our data suggest that the minimal temperature at which 'probing' of H. halys occurs is between 3.5 and 6.1 degree C (95% CI), and that 'probing' does not occur at temperatures above 26.5 to 29.6 degree C (95% CI). We estimated that the optimal temperature for 'probing' is between 16 and 17 degree C.
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.
Temperature-dependent fecundity and survival data was integrated into a matrix population model to describe relative Drosophila suzukii Matsumura (Diptera: Drosophilidae) population increase and age ...structure based on environmental conditions. This novel modification of the classic Leslie matrix population model is presented as a way to examine how insect populations interact with the environment, and has application as a predictor of population density. For D. suzukii, we examined model implications for pest pressure on crops. As case studies, we examined model predictions in three small fruit production regions in the United States (US) and one in Italy. These production regions have distinctly different climates. In general, patterns of adult D. suzukii trap activity broadly mimicked seasonal population levels predicted by the model using only temperature data. Age structure of estimated populations suggest that trap and fruit infestation data are of limited value and are insufficient for model validation. Thus, we suggest alternative experiments for validation. The model is advantageous in that it provides stage-specific population estimation, which can potentially guide management strategies and provide unique opportunities to simulate stage-specific management effects such as insecticide applications or the effect of biological control on a specific life-stage. The two factors that drive initiation of the model are suitable temperatures (biofix) and availability of a suitable host medium (fruit). Although there are many factors affecting population dynamics of D. suzukii in the field, temperature-dependent survival and reproduction are believed to be the main drivers for D. suzukii populations.
The tachinid flies Nemorilla pyste (Walker) and Nilea erecta (Coquillett) (Diptera) are important parasitoids of leafroller pests (Lepidoptera: Tortricidae) in central Washington tree fruits. ...Commercial orchard sites in central Washington were sampled from 2006-2010 for leafroller larvae, which were reared to collect parasitoids. The flies were widely distributed, and N. pyste was more frequently collected than N. erecta. The lifestage of host larvae and the time of collection determined that host size preferences and phenology were similar. The flies were reared in the laboratory and dissected in order to determine their reproductive biology. Nemorilla pyste was found to be a highly synovigenic oviparous species, while N. erecta was found to be moderately synovigenic and ovolarviparous. Longevity and fertility of the parasitoids and mortality of the leafroller Choristoneura rosaceana Harris were examined in a life table study with variable host density. Nemorilla pyste had higher fertility because females were able to adjust oviposition to the number of hosts available, while N. erecta lacked this ability, and had poor control over self-superparasitism. Despite lower reproductive rates, N. erecta may have greater effect on leafroller populations because superparasitism eliminated hosts. Egg allocation of N. pyste attacking C. rosaceana was also examined in a demographic context. While large clutches may at times be necessary to ensure production of offspring when hosts are rare, they were associated with higher fitness costs such as reduced offspring survival, increased developmental time, and decreased male body size. Life history of the immature stages of these endoparasitoids was studied to examine potential mechanisms for competitive interactions including development rates, respiration-mediated competition, selective starvation, tolerance, and physical interference. Intra- and interspecific competition in the host was also experimentally manipulated to examine outcomes. The two parasitoids had distinct respiration strategies but similar development rates. Strong evidence of intraguild predation by N. erecta was found and the species tended to dominate N. pyste in interspecific interactions. Finally, compatibility of adult flies with residues of the insecticides pyriproxyfen and methoxyfenozide was investigated. Pyriproxyfen had strong effects on survival of the flies that was shown to have detrimental effects on projected fertility rates.
A recent identification of the two-component aggregation pheromone of the invasive stink bug species, Halyomorpha halys (Stål), in association with a synergist, has greatly improved the ability to ...accurately monitor the seasonal abundance and distribution of this destructive pest. We evaluated the attraction of H. halys to black pyramid traps baited with lures containing the pheromone alone, the synergist methyl (2E,4E,6Z)-decatrienoate (MDT) alone, and the two lures in combination. Traps were deployed around areas of agricultural production including fruit orchards, vegetables, ornamentals, or row crops in Delaware, Maryland, North Carolina, New Jersey, New York, Ohio, Oregon, Pennsylvania, Virginia, and West Virginia from mid-April to mid-October, 2012 and 2013. We confirmed that H. halys adults and nymphs are attracted to the aggregation pheromone season long, but that attraction is significantly increased with the addition of the synergist MDT. H. halys adults were detected in April with peak captures of overwintering adults in mid- to late May. The largest adult captures were late in the summer, typically in early September. Nymphal captures began in late May and continued season long. Total captures declined rapidly in autumn and ceased by mid-October. Captures were greatest at locations in the Eastern Inland region, followed by those in the Eastern Coastal Plain and Pacific Northwest. Importantly, regardless of location in the United States, all mobile life stages of H. halys consistently responded to the combination of H. halys aggregation pheromone and the synergist throughout the entire season, suggesting that these stimuli will be useful tools to monitor for H. halys in managed systems.
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