In phytophagous insects, adult attraction and oviposition preference for a host plant are often positively correlated with their immature fitness; however, little is known how this ...preference–performance relationship changes within insect populations utilizing different host plants. Here, we investigated differences in the preference and performance of two populations of a native North American frugivorous insect pest, the plum curculio (Conotrachelus nenuphar)—one that utilizes peaches and another that utilizes blueberries as hosts—in the Mid‐Atlantic United States. We collected C. nenuphar adult populations from peach and blueberry farms and found that they exhibited a clear preference for the odors of, as well as an ovipositional preference for, the hosts they were collected from, laying 67%–83% of their eggs in their respective collected hosts. To measure C. nenuphar larval performance, a fitness index was calculated using data on larval weights, development, and survival rate from egg to 4th instars when reared on the parent's collected and novel hosts. Larvae of C. nenuphar adults collected from peach had high fitness on peach but low fitness when reared on blueberry. In contrast, larvae from C. nenuphar adults collected in blueberry had high fitness regardless of the host on which they were reared. In this study, we show that utilizing a novel host such as blueberry incurs a fitness cost for C. nenuphar from peaches, but this cost was not observed for C. nenuphar from blueberries, indicating that the preference–performance relationship is present in the case of insects reared on peach, but insects reared on blueberry were more flexible and able to utilize either host, despite preferring blueberry.
In this study, we use a series of experiments to test whether Conotrachelus nenuphar's behavior conforms to the preference–performance hypothesis (PPH). Using insects from two hosts, peach and blueberry, we tested olfactory host preference, oviposition choice, and larval fitness between both hosts. We found that C. nenuphar that use peach are not able to successfully use blueberry, but C. nenuphar that use blueberry are able to use peach, and that choice and attraction are consistent with PPH assumptions.
Egg and nymphal development were studied under constant temperatures for the newly introduced pest species, Halyomorpha halys (Staal) (Hemiptera: Pentatomidae). Development was assessed at seven ...constant temperatures (15-35C). Development to adult was completed at temperatures between 17 and 33C, with egg hatch also occurring at 15C. The relationship between temperature and developmental rate was evaluated using three developmental models. Of the models evaluated, the Briere-1 model was the best fit for the empirical data of egg and total development and for providing accurate values for the temperature threshold. Application of the linear degree-day model estimated 537.63 DD are needed for total development (egg to imaginal ecdysis). An additional 147.65 DD are needed for the preoviposition period of the female. Reproductive parameters were evaluated at 25C and indicate a median number of 28 eggs per egg mass. Oviposition occurred at 4.32-d intervals, and a female can continue to oviposit throughout its lifespan. H. halys is univoltine in New Jersey and Pennsylvania, but if it spreads to warmer climates in the United States, it could have multiple generations per year.
Halyomorpha halys is an introduced stink bug species from Asia that is spreading throughout the Mid-Atlantic United States. It is native to South Korea, Japan, and eastern China, where it is an ...occasional pest of tree fruit, including apple and pear. Cage experiments with adults placed on apple and peach during critical plant growth stages demonstrate that it can cause damage to developing fruit during mid- and late season growth periods and that feeding occurs on all regions of the fruit. Feeding that occurred during pit hardening/mid-season and final swell periods were apparent as damage at harvest, whereas feeding at shuck split/petal fall in peaches and apples caused fruit abscission. Tree fruit at two commercial farms were sampled weekly in 2006–2007 to determine H. halys seasonality. Low densities of nymphs in apple suggest that it is an unsuitable developmental host. Both nymphs and adults were found on pear fruits with peak populations occurring in early July and mid-August, the time when pit hardening/mid-season and swell period damage occurs. At both farms, stink bug damage was greater than 25% damaged fruit per tree. We attribute this to H. halys because population densities were significantly higher than native pentatomids at both locations in both beat samples and blacklight trap captures. The data presented here documents the potential for H. halys to cause damage in orchards throughout the Mid-Atlantic United States and shows the need for development of appropriate control strategies.
Aim
To investigate whether the long‐acting insulin analogue insulin degludec compared with insulin glargine U100 reduces the risk of nocturnal symptomatic hypoglycaemia in patients with type 1 ...diabetes (T1D).
Methods
Adults with T1D and at least one episode of nocturnal severe hypoglycaemia during the last 2 years were included in a 2‐year prospective, randomized, open, multicentre, crossover trial. A total of 149 patients were randomized 1:1 to basal‐bolus therapy with insulin degludec and insulin aspart or insulin glargine U100 and insulin aspart. Each treatment period lasted 1 year and consisted of 3 months of run‐in or crossover followed by 9 months of maintenance. The primary endpoint was the number of blindly adjudicated nocturnal symptomatic hypoglycaemic episodes. Secondary endpoints included the occurrence of severe hypoglycaemia. We analysed all endpoints by intention‐to‐treat.
Results
Treatment with insulin degludec resulted in a 28% (95% CI: 9%‐43%; P = .02) relative rate reduction (RRR) of nocturnal symptomatic hypoglycaemia at level 1 (≤3.9 mmol/L), a 37% (95% CI: 16%‐53%; P = .002) RRR at level 2 (≤3.0 mmol/L), and a 35% (95% CI: 1%‐58%; P = .04) RRR in all‐day severe hypoglycaemia compared with insulin glargine U100.
Conclusions
Patients with T1D prone to nocturnal severe hypoglycaemia have lower rates of nocturnal symptomatic hypoglycaemia and all‐day severe hypoglycaemia with insulin degludec compared with insulin glargine U100.
Recent methodological advances permit surveys for terrestrial insects from the direct collection of environmental DNA (eDNA) deposited on vegetation or other surfaces. However, in contrast to ...well‐studied aquatic applications, little is known about how detection rates for such terrestrial eDNA‐based surveys compare with conventional survey methods. Lycorma delicatula, the spotted lanternfly, is an emerging invasive insect in eastern North America, and a significant ecological and economic pest of forested and agricultural systems, especially grapes. During fall 2019, we conducted two rounds of paired eDNA and visual surveys for spotted lanternflies within 48 plots at 12 vineyards in New Jersey, USA. We compared detection probabilities within a multimethod occupancy modeling framework and used the results to extrapolate and inform survey design. The probability of detecting spotted lanternflies given presence in a plot was over two times higher for eDNA (84%) versus visual surveys (36%). In mid‐September, lanternfly eDNA was detected at five plots in three vineyards, while visual surveys revealed only a single individual in one plot. In early October, after dispersal of lanternflies into vineyards, lanternfly eDNA was detected in 12 plots within six vineyards compared with visual detections in six plots in two vineyards. Extrapolations based on detection and local‐scale occupancy rates indicate that only five and 12 plots would have been needed to positively detect lanternfly presence with 95% confidence using eDNA in contrast to 14 and 29 plots with visual surveys alone, respective to survey rounds. Log‐linear models revealed that visual counts of lanternflies were positively related to eDNA concentrations (R2 = 71%). We provide some of the first quantitative evidence to support the enhanced sensitivity of terrestrial eDNA approaches compared with conventional methods. Such methods can augment efforts to combat invasive species through improved ability to delimit invasion fronts, identify satellite populations, and confirm local eradications.
We field‐tested a recently‐developed protocol for detecting insect eDNA on vegetation surfaces. Lycorma delicatula, the spotted lanternfly, is an emerging invasive insect in the USA that is highly destructive to wine grapes among other crops. Paired surveys in vineyard plots and multimethod occupancy modeling revealed nearly three times higher detection probability for eDNA‐based methods compared with standard visual surveys.
The invasive brown marmorated stink bug,
Halyomorpha halys
(Stål) (Hemiptera: Pentatomidae), is a highly polyphagous and mobile pest causing crop damage aggregated at the perimeters of crop fields. ...Understanding the dispersal biology of
H. halys
is critical for the development of reliable monitoring and management strategies. In this study, dispersal ecology of
H. halys
nymphs was studied under laboratory and field conditions. In the laboratory, horizontal and vertical walking capacity was quantified for mobile nymphal stages (i.e., 2nd through 5th instars) and compared with adults. There was a significant difference in the horizontal distance moved by
H. halys
among the life stages tested. Third instars exhibited significantly greater walking distances compared with adults; horizontal walking distances by other nymphal stages were not significantly different from adults. A similar pattern was observed from vertical climbing tests of
H. halys
. Third and 4th instars climbed significantly greater distances compared with 2nd instars and adults, while distances climbed by 5th instars were intermediate. In the field, the walking distance of 3rd and 5th instar nymphs on mowed grass was quantified based on direct observation of individuals for 30 min. Under these conditions, 5th instars moved nearly two-fold greater distances compared with 3rd instars, but surface temperature affected both nymphal stages similarly. Shorter bouts of movement were common at surface temperatures below 25 °C, whereas individuals showed longer walking distances above 25 °C. In mark-release-recapture studies, 4th and 5th instars were released and recaptured in traps baited with attractive pheromonal-based stimuli to estimate dispersal rates under field conditions. When insects were released 5 m from traps, both instars were first recaptured within 2 h after release, with the recapture rates of 54 and 69 % for 4th and 5th instars over 24 h, respectively. When insects were released 20 m from traps, 4th and 5th instars were first recaptured in less than 5 h, with the recapture rates of 27 and 51 %, respectively. The results of this study indicate that
H. halys
nymphs have strong dispersal capacity with which populations can easily move among host plants and other attractive stimuli at farmscape levels.
Human mediated transportation into novel habitats is a prerequisite for the establishment of non-native species that become invasive, so knowledge of common sources may allow prevention. The brown ...marmorated stink bug (BMSB, Halyomorpha halys) is an East Asian species now established across North America and Europe, that in the Eastern United States of America (US) and Italy is causing significant economic losses to agriculture. After US populations were shown to originate from Northern China, others have tried to source BMSB populations now in Canada, Switzerland, Italy, France, Greece, and Hungary. Due to selection of different molecular markers, however, integrating all the datasets to obtain a broader picture of BMSB's expansion has been difficult. To address this limitation we focused on a single locus, the barcode region in the cytochrome oxidase I mitochondrial gene, and analyzed representative BMSB samples from across its current global range using an Approximate Bayesian Computation approach. We found that China is the likely source of most non-native populations, with at least four separate introductions in North America and three in Europe. Additionally, we found evidence of one bridgehead event: a likely Eastern US source for the central Italy populations that interestingly share enhanced pest status.
Understanding cues for diapause termination in insects can be valuable in predicting phenological events in their lifecycles. Once identified, such cues can be utilized as a biofix, the point at ...which the majority of individuals within a population begin to accumulate degree days. We investigated the impact of photoperiod on completion of reproductive diapause in the invasive eastern North American population of the brown marmorated stink bug, Halyomorpha halys (Stål) (Hemiptera: Pentatomidae), by exposing diapausing females to varying light regimes in otherwise identical environments. The critical photoperiod estimated to initiate reproductive development in at least 50% of the potential reproductive population was 13.0–13.5 h, with increasing photoperiods coinciding with increased probability of females reproducing, earlier time to first oviposition, and higher rates of fecundity. These data on the species' response to photoperiod are in agreement with previous modeling that predicted the twin constraints of photoperiod and temperature on H. halys reproduction prevents populations that undergo diapause from producing more than two generations annually anywhere within the continental U.S. However, the facultative nature of diapause in H. halys leaves open the possibility that sub-populations may not enter diapause in some conditions, potentially allowing for additional annual generations.
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