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.

Effects of Wolbachia elimination and B-vitamin supplementation on bed bug development and reproduction.

Obligate blood feeders, such as Cimex lectularius (common bed bug), have symbiotic associations with nutritional endosymbionts that produce B-vitamins. To quantify the symbiont's contribution to host fitness in these obligate mutualisms, the symbiont must be eliminated and its absence rigorously confirmed. We developed and validated procedures for complete elimination of Wolbachia (Wb) in bed bugs and quantified development and reproduction in bed bugs with and without Wb and with and without B-vitamins supplementation. Aposymbiotic bed bugs had slower nymphal development, reduced adult survivorship, smaller adult size, fewer eggs per female, and lower hatch rate than bed bugs that harbored Wb. In aposymbiotic bed bugs that were fed B-vitamins-supplemented blood, nymph development time, adult survivorship and hatch rate recovered to control levels, but adult size and egg number only partially recovered. These results underscore the nutritional dependence of bed bugs on their Wb symbiont and suggest that Wb may provide additional nutritional benefits beyond the B-vitamin mix that we investigated.

Mortality of Emerald Ash Borer Larvae in Small Regenerating Ash in New York Forests.

Despite a robust biocontrol program against emerald ash borer, Agrilus planipennis Fairmaire (Coleoptera: Buprestidae), parasitoid populations cannot build quickly enough to save mature ash trees. The future of ash as a viable component of North American forests depends on survival of immature ash that were too small to be attacked during the initial outbreak. This study was designed to quantify impacts of established introduced parasitoids and native woodpeckers on the population growth of emerald ash borer infesting regenerating ash saplings in white ash forests. Most emerald ash borer larvae were killed by Tetrastichus planipennisi Yang and woodpeckers in the fourth instar. Life-table analyses revealed that the estimated net reproductive rate of emerald ash borer was R0 = 4.2 in eastern New York and R0 = 0.0 in western New York. Without mortality from parasitoids and woodpeckers, R0 values would have been 16.4 and 7.9 in eastern and western New York, respectively. We monitored the health of mature and sapling ash trees from 2012 to 2017 and found that large trees were significantly more likely to be infested with emerald ash borer and to die than smaller trees. Fifty-four percent to 81% of ash saplings contained no living emerald ash borer, and the density of emerald ash borer at all sites was very low (< 4/m2). This study adds to the growing body of evidence that emerald ash borer biocontrol is contributing to population control and can help promote survival of young ash trees as forests recover from emerald ash borer outbreaks.

Development of rearing methodology for the invasive Spotted Lanternfly, Lycorma delicatula (Hemiptera: Fulgoridae).

Lycorma delicatula, White (Hemiptera: Fulgoridae), spotted lanternfly, is a univoltine, phloem-feeding, polyphagous and invasive insect in the USA. Although a primary host for this species is Ailanthus altissima, tree of heaven, L. delicatula also feeds on a wide range of hosts important to the USA including cultivated grapevines. Due to the need for classical or augmentative biological control programs to reduce impacts of L. delicatula across invaded areas, we developed a laboratory-based rearing protocol for this invasive species. Here, we evaluated the use of A. altissima apical meristems, epicormic shoots, and fresh foliage cut from A. altissima as a food source for rearing newly hatched L. delicatula. On these sources of plant material <20% of L. delicatula developed into adults and no oviposition occurred. However, when young, potted A. altissima trees were used as a food source, >50% of L. delicatula nymphs developed to the adult stage under natural daylengths and temperatures ranging from 20-25°C. The addition of wild grapevine, Vitis riparia, did not increase survivorship or reduce development time. To elicit mating and oviposition, adults were provided with A. altissima logs as an oviposition substrate and maintained under shortened daylengths and reduced nighttime temperatures (12L:12D and 24°C:13°C). This resulted in 2.12 egg masses deposited per female, which was 4× more than when adults were maintained in standard rearing conditions (16L:8D and 25°C). Based on these experiments, we present a protocol for reliably rearing L. delicatula under laboratory and/or greenhouse conditions.

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.

Life History and Rearing of Anastatus orientalis (Hymenoptera: Eupelmidae), an Egg Parasitoid of the Spotted Lanternfly (Hemiptera: Fulgoridae).

To support efforts to manage and contain spotted lanternfly (SLF), Lycorma delicatula White (Hemiptera: Fulgoridae), research is being conducted to develop classical biological control methods. To date, two potential biocontrol agents from China have been identified: an egg parasitoid, Anastatus orientalis, and a nymphal parasitoid, Dryinus sinicus Olmi (Hymenoptera: Dryinidae). The research detailed here focuses on investigating the biology and rearing of A. orientalis to assess its potential efficacy in a biocontrol program and optimize its rearing. Female wasps lived significantly longer than male wasps (68 and 23 d, respectively) and females produced an average of 94 total progeny that successfully emerged as adults, with most progeny produced between weeks one and four of the females' lives. The sex ratio of the progeny, with no re-mating, was initially highly female-biased but became progressively more male-biased, likely due to sperm depletion. There was no evidence of additional mortality to SLF eggs from wasp host feeding, but the data were highly variable and the sample size was small. There was high parasitoid emergence when oviposition conditions mimicked mid-September Beijing temperature and photoperiod; however, there was little emergence under 25°C and long-day conditions because most progeny entered a diapause. Storage of parasitized eggs in 5°C chill lowered parasitoid emergence rates. Lastly, there was no evidence that storing field-collected SLF egg masses in 5°C for 10 mo prior to parasitization affected parasitism rates. These findings inform our rearing protocol for A. orientalis and facilitate our testing of this species as a potential biological control agent for SLF.

Chronic impacts of invasive herbivores on a foundational forest species: a whole-tree perspective.

Forests make up a large portion of terrestrial plant biomass, and the long-lived woody plants that dominate them possess an array of traits that deter consumption by forest pests. Although often extremely effective against native consumers, invasive species that avoid or overcome these defenses can wreak havoc on trees and surrounding ecosystems. This is especially true when multiple invasive species co-occur, since interactions between invasive herbivores may yield non-additive effects on the host. While the threat posed by invasive forest pests is well known, long-term field experiments are necessary to explore these consumer-host interactions at appropriate spatial and temporal scales. Moreover, it is important to measure multiple variables to get a "whole-plant" picture of their combined impact. We report the results of a 4-yr field experiment addressing the individual and combined impacts of two invasive herbivores, the hemlock woolly adelgid (Adelges tsugae) and elongate hemlock scale (Fiorinia externa), on native eastern hemlock (Tsuga canadensis) in southern New England. In 2011, we planted 200 hemlock saplings into a temperate forest understory and experimentally manipulated the presence/absence of both herbivore species; in 2015, we harvested the 88 remaining saplings and assessed plant physiology, growth, and resource allocation. Adelgids strongly affected hemlock growth: infested saplings had lower above/belowground biomass ratios, more needle loss, and produced fewer new needles than control saplings. Hemlock scale did not alter plant biomass allocation or growth, and its co-occurrence did not alter the impact of adelgid. While both adelgid and scale impacted the concentrations of primary metabolites, adelgid effects were more pronounced. Adelgid feeding simultaneously increased free amino acids local to feeding sites and a ~30% reduction in starch. The cumulative impact of adelgid-induced needle loss, manipulation of nitrogen pools, and the loss of stored resources likely accelerates host decline through disruption of homeostatic source-sink dynamics occurring at the whole-plant level. Our research stresses the importance of considering long-term impacts to predict how plants will cope with contemporary pressures experienced in disturbed forests.

Effects of Light and Water Availability on the Performance of Hemlock Woolly Adelgid (Hemiptera: Adelgidae).

Eastern hemlock (Tsuga canadensis (L.) Carriere) is a dominant shade-tolerant tree in northeastern United States that has been declining since the arrival of the hemlock woolly adelgid (Adelges tsugae Annand). Determining where A. tsugae settles under different abiotic conditions is important in understanding the insect's expansion. Resource availability such as light and water can affect herbivore selectivity and damage. We examined how A. tsugae settlement and survival were affected by differences in light intensity and water availability, and how adelgid affected tree performance growing in these different abiotic treatments. In a greenhouse at the University of Rhode Island, we conducted an experiment in which the factors light (full-sun, shaded), water (water-stressed, watered), and adelgid (infested, insect-free) were fully crossed for a total of eight treatments (20 two-year-old hemlock saplings per treatment). We measured photosynthesis, transpiration, water potential, relative water content, adelgid density, and survival throughout the experiment. Adelgid settlement was higher on the old-growth foliage of shaded and water-stressed trees, but their survival was not altered by foliage age or either abiotic factor. The trees responded more to the light treatments than the water treatments. Light treatments caused a difference in relative water content, photosynthetic rate, transpiration, and water potential; however, water availability did not alter these variables. Adelgid did not enhance the impact of these abiotic treatments. Further studies are needed to get a better understanding of how these abiotic factors impact adelgid densities and tree health, and to determine why adelgid settlement was higher in the shaded treatments.