Feasting on the ordinary or starving for the exceptional in a warming climate: Phenological synchrony between spongy moth (Lymantria dispar) and budburst of six European tree species.

Global warming is affecting the phenological cycles of plants and animals, altering the complex synchronization that has co-evolved over thousands of years between interacting species and trophic levels. Here, we examined how warmer winter conditions affect the timing of budburst in six common European trees and the hatching of a generalist leaf-feeding insect, the spongy moth Lymantria dispar, whose fitness depends on the synchrony between egg hatch and leaf emergence of the host tree. We applied four different temperature treatments to L. dispar eggs and twig cuttings, that mimicked warmer winters and reduced chilling temperatures that are necessary for insect diapause and bud dormancy release, using heated open-top chambers (ambient or +3.5°C), and heated greenhouses (maintained at >6°C or >10°C). In addition, we conducted preference and performance tests to determine which tree species the larvae prefer and benefit from the most. Budburst success and twig survival were highest for all tree species at ambient temperature conditions, whereas it declined under elevated winter temperature for Tilia cordata and Acer pseudoplatanus, likely due to a lack of chilling. While L. dispar egg hatch coincided with budburst in most tree species within 10 days under ambient conditions, it coincided with budburst only in Quercus robur, Carpinus betulus, and, to a lesser extent, Ulmus glabra under warmer conditions. With further warming, we, therefore, expect an increasing mismatch in trees with high chilling requirements, such as Fagus sylvatica and A. pseudoplatanus, but still good synchronization with trees having low chilling requirements, such as Q. robur and C. betulus. Surprisingly, first instar larvae preferred and gained weight faster when fed with leaves of F. sylvatica, while Q. robur ranked second. Our results suggest that spongy moth outbreaks are likely to persist in oak and hornbeam forests in western and central Europe.

Effects of adult-diet modifications on sexual maturation rate, body weight, and quantity of sperm transfer by male Mexican fruit fly (Diptera: Tephritidae).

Mass-reared sterile Mexican fruit flies (Anastrepha ludens [Loew]) are released along the US-Mexico border to control fruit fly damage and spread. It is more cost effective for the mass rearing program if males mature at a younger age because they can be held for a shorter time at the facility before release. In this study, adult male Mexican fruit fly diets were tested to determine if the current diet used at the mass rearing facility promotes younger mating and optimal sperm transfer compared to other diet formulations. Hydrolyzed yeast presentation methods were examined: an agar-free dry mixture of yeast and sugar (Y+S), yeast embedded in the diet during the agar boiling process (current method used) and sifted dry on the ager gel surface. Methoprene, a juvenile hormone analog was also tested as a supplement to agar gel diets with and without yeast. A greater proportion of males fed Y+S mated 1 day earlier than males fed other diets. Male mating age and diet did not significantly affect the quantity of sperm transferred; however, a non-significantly higher percentage of males fed diets with embedded yeast transferred enough sperm to fill all 3 spermathecae. The results suggest that the current diet used is optimal for mass-rearing the flies and that yeast presentation method has a significant effect on A. ludens male mating age but not on the quantity of sperm transferred to females.

Electrophysiologically Determined Spectral Responses in Lobesia botrana (Lepidoptera: Tortricidae).

Electrophysiological methods were used to test the visual sensitivity of European grapevine moth, Lobesia botrana (Lepidoptera: Tortricidae) to wavelengths ranging from 300 to 700 nm. For male and females tested, a main, peak response occurred in the 460-540 nm range (blue-green wavelengths) with females having a generally lower response to wavelengths in that range. A second smaller peak was observed for both sexes at the 340-420 nm range. A general linear model indicated that males, virgin females, and mated females did not react differently to changes in wavelength. No moths showed any obvious sensitivity to wavelengths between 580 and 700 nm. Based on our retinal recording data we suggest that UV light traps (≤480 nm) could be utilized alongside pheromone traps when monitoring L. botrana in high risk areas.

Optimization of a Diet for the Greater Wax Moth (Lepidoptera: Pyralidae) Using Full Factorial and Mixture Design.

Diet optimization is an important process to increase the efficiency of rearing insects and can be used to develop high-quality insects with specific fitness and life-history traits. Galleria mellonella (L.), the greater wax moth, is widely used in research, microbiology assays, as pet food, and host for biological control agents. Although artificial diets for G. mellonella have been researched and optimized for decades, preliminary tests indicated that the predominantly utilized G. mellonella diet could be improved to yield larger larvae with a short development time. We used a design of experiments (DOE) approach that incorporated multiple full factorial designs and a final mixture design to test the qualitative and quantitative effects of ingredients and their interactions on larval mass and survival. Analysis of 17 ingredient variations in 35 diet formulations yielded an optimized diet that supported high survival and 2.4-fold greater larval body mass than the standard rearing diet. This study demonstrates the importance and efficiency of statistical DOE in guiding the optimization of insect diets to improve traits that represent the quality and fitness of the reared insects.

Identification of Tree Genera Used in the Construction of Solid Wood-Packaging Materials That Arrived at U.S. Ports Infested With Live Wood-Boring Insects.

Although international regulations have been successfully implemented to reduce the introduction and spread of plant pests through wood packaging material (WPM), wood-boring insects continue to be intercepted in WPM at U.S. ports of entry. Both hardwoods and softwoods are used in the construction of WPM for international trade; however, it is not clear if some types of wood pose higher risks than others for harboring wood borers. This study documented the taxonomic diversity of infested wood genera intercepted as a result of targeted WPM inspection at U.S. ports, and identified many of the wood-boring insects transported within them. The results of this study reveal associations among packaging woods, commodities, and shipment origins. The wood genera most frequently infested were Pinus Linnaeus (Pinales: Pinaceae), Picea Miller (Pinales: Pinaceae), and Populus Linnaeus (Malpighiales: Salicaceae), which were heavily represented as packaging for commodities such as stone, metal, vehicles, and machinery. In addition to these results, we summarized preferences by the wood borers to develop in living, stressed, dying, or dead hosts, the pest status of intercepted wood borers in their native and non-native ranges, and potential host range of intercepted wood borers to gauge potential for these taxa to become pests in North America. New possible host associations are reported for eight wood borer taxa. Taxonomy of host wood is presented as a new factor for consideration in pathway-level risk analysis of WPM, and the findings further reinforce the need for enhanced compliance with ISPM 15 to reduce entry of non-native wood-boring insects.

Towards an Automated Acoustic Detection Algorithm for Wood-Boring Beetle Larvae (Coleoptera: Cerambycidae and Buprestidae).

The development of acoustic systems for detection of wood-boring larvae requires knowledge of the features of signals produced both by insects and background noise. This paper presents analysis of acoustic/vibrational signals recorded in tests using tree bolts infested with Anoplophora glabripennis (Motschulsky) (Coleoptera: Cerambycidae) (Asian longhorn beetle) and Agrilus planipennis Fairmaire (Coleoptera: Buprestidae) (emerald ash borer) larvae. Based on features found, an algorithm for automated insect signal detection was developed. The algorithm automatically detects pulses with parameters typical for the larva-induced signals and rejects noninsect signals caused by ambient noise. The decision that a wood sample is infested is made when the mean rate of detected insect pulses per minute exceeds a predefined threshold. The proposed automatic detection algorithm demonstrated the following performance: 12 out of 15 intact samples were correctly classified as intact, 23 out of 25 infested samples were correctly classified as infested, and five samples out of the total 40 were classified as 'unknown.' This means that a successful wood-sample classification of 87.5% was achieved, with the remaining 12.5% classified as 'unknown,' requiring a repeat of the test in a less noisy environment, or manual inspection.

Postharvest Irradiation Treatment for Quarantine Control of the Invasive Lobesia botrana (Lepidoptera: Tortricidae).

Irradiation is a postharvest treatment option for exported berries and berry-like fruits to prevent movement of the quarantine pest European grape vine moth, Lobesia botrana (Denis & Schiffermüller) (Lepidoptera: Tortricidae). The effects of irradiation on egg, larval, and pupal development in L. botrana were examined. Eggs, neonates, third and fifth instars, and early- and late-stage pupae were irradiated at target doses of 50, 100, 150, or 200 Gy or left untreated as controls in replicated factorial experiments, and survival to the adult stage was recorded. Tolerance to radiation generally increased with increasing age and developmental stage. A dose of 150 Gy prevented adult emergence in eggs and larvae. Pupae were more radiotolerant than larvae, and late-stage pupae were more tolerant than early-stage pupae. In large-scale validation tests, 150 Gy applied to fifth instars in diet prevented adult emergence, but some survival occurred in fifth instars irradiated in table grapes; however, 250 Gy prevented fifth instar survival in grapes. For most commodities, the fifth instar is the most radiotolerant life stage likely to occur with the commodity; a minimum radiation dose of 250 Gy will prevent adult emergence from this stage. For traded commodities such as table grapes that may contain L. botrana pupae, 325 Gy applied to mature female pupae sterilized emerging adults and may provide quarantine security. Radiotolerance in L. botrana is comparable to other tortricids, and the data reported here support a generic dose of 250 Gy for eggs and larvae of this group.

Effects of Temperature on Development of Lymantria dispar asiatica and Lymantria dispar japonica (Lepidoptera: Erebidae).

Periodic introductions of the Asian subspecies of gypsy moth, Lymantria dispar asiatica Vnukovskij and Lymantria dispar japonica Motschulsky, in North America are threatening forests and interrupting foreign trade. Although Asian gypsy moth has similar morphology to that of European and North American gypsy moth, it has several traits that make it a greater threat, the most important being the flight capability of females. Asian gypsy moth is not yet established in North America; however, infestations have been detected multiple times in Canada and the United States. To facilitate detection and eradication efforts, we evaluated the effect of a range of temperatures on development time, survivorship, and fertility of eight populations of Asian gypsy moth. There were significant impacts of temperature and population on these life history characteristics. The larval developmental rate increased with temperature until it reached an optimum at 29 °C. Larvae experienced significant molting problems at the highest and lowest temperatures tested (10 °C and 30 °C). At 30 °C, female fitness was markedly compromised, as evidenced by reduced fecundity and fertility. This suggests that development and survival of Asian gypsy moth may be limited by summer temperature extremes in the Southern United States. We also determined the degree-day requirements for two critical life stages and two populations of Asian gypsy moth, which represent the extremes in latitude, to predict the timing for biopesticide application and adult trap deployment. Our data will benefit pest managers in developing management strategies, pest risk assessments, and timing for implementation of management tactics.

Landscape-Level Patterns of Elevated FS1 Asian Allele Frequencies in Populations of Gypsy Moth (Lepidoptera: Erebidae) at a Northern U.S. Boundary.

From a regulatory perspective, Asian gypsy moth is a species complex consisting of three species of Lymantria and two subspecies of Lymantria dispar (L.), differing from the European subspecies, L. dispar dispar (L.), by having consistently flight-capable females. As such, the invasion potential in North America is thought to exceed that of European gypsy moth. USDA-APHIS therefore has a monitoring program to detect Asian gypsy moth at high-risk introduction pathways. Molecular markers are used to improve the diagnosis of Asian gypsy moth. One such marker, which targets the FS1 locus, detects an allele, FS1-A, prevalent in Asian populations but occurring at low frequencies (3-6%) throughout the European gypsy moth's range in North America. However, some locales, such as Minnesota, exhibit elevated FS1-A frequencies. We studied the distribution of the FS1-A allele in northern Minnesota, 2013-2014, assessing spatial patterns in the distribution of the FS1-A allele using Moran's I and using spatial regression techniques to examine if the FS1-A allele was associated with putative movement pathways. We also used time series analysis to discern if temporal patterns in FS1-A or possible introduction events occurred. Our results indicated that FS1-A occurred randomly in space and time. We found no evidence that elevated FS1-A frequencies were associated with movement pathways or possible immigration events into this region over the two years. Elevated frequencies of the FS1-A allele within this region could be due to genetic drift and allelic surfing along the expanding population front, or to selection of physiological or behavioral traits.

Identification of wood-boring beetles (Cerambycidae and Buprestidae) intercepted in trade-associated solid wood packaging material using DNA barcoding and morphology.

Global trade facilitates the inadvertent movement of insect pests and subsequent establishment of populations outside their native ranges. Despite phytosanitary measures, nonnative insects arrive at United States (U.S.) ports of entry as larvae in solid wood packaging material (SWPM). Identification of wood-boring larval insects is important for pest risk analysis and management, but is difficult beyond family level due to highly conserved morphology. Therefore, we integrated DNA barcoding and rearing of larvae to identify wood-boring insects in SWPM. From 2012 to 2015, we obtained larvae of 338 longhorned beetles (Cerambycidae) and 38 metallic wood boring beetles (Buprestidae) intercepted in SWPM associated with imported products at six U.S. ports. We identified 265 specimens to species or genus using DNA barcodes. Ninety-three larvae were reared to adults and identified morphologically. No conflict was found between the two approaches, which together identified 275 cerambycids (23 genera) and 16 buprestids (4 genera). Our integrated approach confirmed novel DNA barcodes for seven species (10 specimens) of woodborers not in public databases. This study demonstrates the utility of DNA barcoding as a tool for regulatory agencies. We provide important documentation of potential beetle pests that may cross country borders through the SWPM pathway.

Overwintering survival of olive fruit fly (Diptera: Tephritidae) and two introduced parasitoids in California.

The overwintering survival and development of olive fruit fly, Bactrocera oleae (Rossi), and the endoparasitoids, Psyttalia humilis Silvestri and P. lounsburyi (Silvestri), were investigated at sites in California's interior valley and coastal region. In the interior valley, adult flies survived up to 4-6 mo during the winter when food was provided. Adult female flies could oviposit in late fall and early winter on nonharvested fruit and, although egg survival was low (0.23-8.50%), a portion of the overwintered cohort developed into adults the following spring; percentage of survival was negatively correlated to daily minimum temperature. P. humilis and P. lounsburyi successfully oviposited into host larvae in late fall, and their progeny developed into adults the following spring, although with a low percentage (0-11.9%) survivorship. Overwintering survival of puparia of the olive fruit fly and immature larvae of P. humilis and P. lounsburyi (inside host puparia), buried in the soil, were tested at an interior valley and coastal site. Survival of olive fruit fly ranged from 0 to 60% and was affected by the trial date and soil moisture. Overwintering survival of both the fruit fly and tested parasitoids was lower at the colder interior valley than the coastal site; P. humilis immature stages had the highest mortality levels while B. oleae pupae had the lowest mortality levels. The spring emergence pattern of the tested insects was well predicted by a degree-day model. We discuss factors potentially impeding establishment of introduced olive fruit fly parasitoids in California and elsewhere.

High summer temperatures affect the survival and reproduction of olive fruit fly (Diptera: Tephritidae).

The olive fruit fly, Bactrocera oleae (Rossi) (Diptera: Tephritidae), is an invasive pest in California. Identifying environmental constraints that affect the geographic distribution and abundance of any invasive insect pest is fundamental to its effective management. California's Central Valley, where most commercial olives are grown, is extremely hot during the summer, with maximum daily temperatures consistently >35.0 degrees C. This study examined the effects of two diurnal temperature regimens (low 18.3 degrees C, high 35.0 or 37.8 degrees C) reflecting summer conditions in the valley, and one control temperature regimen (low 18.3 degrees C, high 23.9 degrees C) on the fly's survival and reproductive success in the laboratory. The temperature regimen of 18.3-35.0 degrees C resulted in delayed egg maturation and reduced production of mature eggs compared with the control temperature regimen. Egg maturation was possible at the higher temperature regimen when females were provided with water and food, and egg-laying occurred during the cold phase of the temperature cycle. Access to olive fruit and oviposition itself further promoted egg maturation. Under exposure to the 18.3-35.0 degrees C temperature regimen, approximately 50% of eggs died, and the remainder that hatched died as first instars. No egg hatch occurred at the temperature treatment of 18.3-37.8 degrees C. We confirmed these laboratory results through field cage studies with adult B. oleae, conducted in the summer of 2007 and 2008. Under ambient summer temperatures, adult B. oleae survived for 1-2 wk, and females readily laid eggs when provided water and food. No offspring developed in midsummer of 2007, and <2% of the offspring developed to adults in summer 2008 trials. These results suggest that high summer temperatures limit the fly's abundance in California's Central Valley.