Abundance of Halyomorpha halys (Hemiptera: Pentatomidae) and Megacopta cribraria (Hemiptera: Plataspidae) in Soybean in Areas with Few Previous Sightings in Tennessee

Halyomorpha halys (Stål) and Megacopta cribraria (Fabricius) are two exotic invasive pests that have invaded the United States in recent years. Halyomorpha halys can damage various fruits, vegetables, and field crops, such as soybean and corn, while Megacopta cribraria only attacks soybean and kudzu, a weed species. They are currently found in southeastern states and threaten soybean and other crops grown in the region. This study evaluated the seasonal abundance of H. halys and M. cribraria in soybeans in 2016 and 2017 in two counties in the central region of Tennessee, where both species had either a few sightings or none that were recorded when this research was being planned. Lures and sweep sampling were used to monitor H. halys, and sweep sampling was used to monitor M. cribraria. Halyomorpha halys was first detected in samples in late July. Their numbers increased in early to mid-September, reached the economic threshold in late Sept, and then started to decline. Megacopta cribraria was first detected in mid to late July, increased their populations in September, but did not reach the economic threshold and declined mid-October. Our results showed the seasonal abundances of H. halys and M. cribraria and their establishment in the central region of Tennessee

Stability of Cacopsylla pyricola (Hemiptera: Psyllidae) Populations in Pacific Northwest Pear Orchards Managed with Long-Term Mating Disruption for Cydia pomonella (Lepidoptera: Tortricidae)

This study focused on conservation biological control of pear psylla, Cacopsylla pyricola, in the Pacific Northwest, USA. We hypothesized that insecticides applied against the primary insect pest, codling moth Cydia pomonella, negatively impact natural enemies of pear psylla, thus causing outbreaks of this secondary pest. Hence, the objective of this study was to understand how codling moth management influences the abundance of pear psylla and its natural enemy complex in pear orchards managed under long-term codling moth mating disruption programs. We conducted this study within a pear orchard that had previously been under seasonal mating disruption for codling moth for eight years. We replicated two treatments, “natural enemy disrupt” (application of two combination sprays of spinetoram plus chlorantraniliprole timed against first-generation codling moth) and “natural enemy non-disrupt” four times in the orchard. Field sampling of psylla and natural enemies (i.e., lacewings, coccinellids, spiders, Campylomma verbasci, syrphid flies, earwigs) revealed that pear psylla populations remained well below treatment thresholds all season despite the reduced abundance of key pear psylla natural enemies in the natural enemy disrupt plots compared with the non-disrupt treatment. We speculate that pear psylla are difficult to disrupt when pear orchards are under long-term codling moth disruption

Testing the selectivity of pesticide effects on natural enemies in laboratory bioassays

The toxic effects of older classes of pesticides on natural enemies are typically acute and exposure usually occurs through direct contact with foliar residues. However, older chemistries are being replaced by newer classes of pesticides that can cause sublethal effects in addition to direct mortality. We developed a set of life table response protocols to quantify the effects of multiple routes of exposure to pesticides on individual-level life history parameters of predators and parasitoids. We then integrated the data into population-level endpoint estimates of population growth rates using stage-structured population models. For this study, we evaluated the impacts of five insecticides (cyantraniliprole, chlorantraniliprole, spinetoram, novaluron and lambda-cyhalothrin) and two fungicides (sulfur and a mixture of copper hydroxide and mancozeb) on a generalist insect predator Chrysoperla carnea (Stephens) (Neuroptera: Chrysopidae) and an aphid parasitoid Trioxys pallidus (Haliday) (Hymenoptera: Braconidae). Green lacewings and T. pallidus are key members of the natural enemy community in western USA orchards. The results of these laboratory studies demonstrate that both C. carnea and T. pallidus were negatively affected by cyantraniliprole, spinetoram and lambda-cyhalothrin while only one species was affected by chlorantraniliprole and novaluron (C. carnea) or sulfur (T. pallidus). The benefits of integrating acute, chronic, and sublethal effects from laboratory bioassays to assess the selectivity of pesticides with respect to natural enemies are discussed

Developmental Time, Longevity, and Lifetime Fertility of Three Introduced Parasitoids of the Mealybug Paracoccus marginatus (Hemiptera: Pseudococcidae)

Developmental time, longevity, and lifetime fertility of three previously introduced parasitoids (Acerophagus papayae Noyes and Schauff, Anagyrus loecki Noyes and Menezes, and Pseudleptomastix mexicana Noyes and Schauff) (Hymenoptera: Encyrtidae) of the mealybug Paracoccus marginatus Williams and Granara de Willink (Hemiptera: Pseudococcidae) were studied in the laboratory to understand the outcome of their recovery in field studies conducted in the United States. The developmental time of both male and female A. papayae and A. loecki was shorter than the developmental time of male and female P. mexicana. Male parasitoids of all three species had a shorter developmental time than their females. All parasitoids had a shorter developmental time in adult-female mealybugs than in second instars. Mating status (unmated and mated) had no effect on the male longevity. Unmated and mated females that were not allowed to oviposit had similar longevity and lived longer than those that were allowed to oviposit. Virgin females produced male only progeny with higher number of males from A. loecki or P. mexicana than from A. papayae. The number of females and the cumulative progeny was smaller for A. papayae than for A. loecki or P. mexicana. The progeny sex ratio (proportion of females) was not different among the parasitoids. A. papayae had the shortest reproductive period followed by A. loecki and P. mexicana, respectively. This information is important in evaluating the efficiency, recovery and establishment of A. papayae, A. loecki, and P. mexicana

Host Instar Susceptibility and Selection and Interspecific Competition of Three Introduced Parasitoids of the Mealybug Paracoccus marginatus (Hemiptera: Pseudococcidae)

Three previously introduced parasitoids (Acerophagus papayae Noyes and Schauff, Anagyrus loecki Noyes and Menezes, and Pseudleptomastix mexicana Noyes and Schauff [Hymenoptera: Encyrtidae]) of the mealybug Paracoccus marginatus Williams and Granara de Willink (Hemiptera: Pseudococcidae) were studied for their host instar susceptibility and sex ratio, host instar selection, and interspecific competition in the laboratory. All three parasitoids were able to develop in the second instars, third-instar females, and adult females of P. marginatus. No progeny emerged from first-instar mealybugs. The proportion of female emergence was increased with increasing host size. Parasitoids selected their host instars for oviposition when they had a choice. Between second- and third-instar hosts, A. papayae and P. mexicana had significantly higher parasitism in second-instar mealybugs, whereas A. loecki had higher parasitism in the third-instar mealybugs. When competed with either one or two parasitoid species, A. papayae was significantly more successful in second-instar hosts and A. loecki was significantly more successful in third-instar mealybugs. P. mexicana was significantly less competitive when with A. papayae in both second and third instars, with A. loecki in third instars and with both A. papayae and A. loecki in second and third instars. Overall, A. papayae provided a better control of the host, when present singly or with the other two parasitoids. This information is important in evaluating the efficiency of A. papayae, A. loecki, and P. mexicana and understanding the outcome of their recovery and establishment in field studies conducted in Florida

Life History of Paracoccus marginatus (Hemiptera: Pseudococcidae) on Four Host Plant Species Under Laboratory Conditions

Life history of the mealybug, Paracoccus marginatus Williams and Granara de Willink, on three ornamental plants [Hibiscus rosa-sinensis L., Acalypha wilkesiana (Muell.-Arg.), and Plumeria rubra L.] and one weed species (Parthenium hysterophorus L.) was studied under laboratory conditions. Mealybugs were able to develop, survive, and reproduce on all four hosts; however, there were differences in the life history parameters. Adult females that developed on acalypha and parthenium emerged ≈1 d earlier than those that developed on hibiscus and plumeria. Adult males had a longer developmental time on plumeria than on the other hosts. Survival of first- and second-instar nymphs and cumulative adult survival were lowest on plumeria. Longevity was not affected by hosts for males and females and averaged 2.3 ± 0.1 and 21.2 ± 0.1 d, respectively. On plumeria, 58.9 ± 1.7% of the adults were females, which was a higher female percentage than on the other hosts. No egg production occurred in virgin females. Prereproductive and reproductive periods of the females were not affected by hosts and averaged 6.3 ± 0.1 and 11.2 ± 0.1 d, respectively. Mean fecundity of 186.3 ± 1.8 eggs on plumeria was lower than on the other three plant species. Life history parameters of P. marginatus on hibiscus, acalypha, plumeria, and parthenium show its ability to develop, survive, and reproduce on a wide variety of plant species

Developmental Time, Longevity, and Lifetime Fertility of Three Introduced Parasitoids of the Mealybug Paracoccus marginatus (Hemiptera: Pseudococcidae)

Developmental time, longevity, and lifetime fertility of three previously introduced parasitoids (Acerophagus papayae Noyes and Schauff, Anagyrus loecki Noyes and Menezes, and Pseudleptomastix mexicana Noyes and Schauff) (Hymenoptera: Encyrtidae) of the mealybug Paracoccus marginatus Williams and Granara de Willink (Hemiptera: Pseudococcidae) were studied in the laboratory to understand the outcome of their recovery in field studies conducted in the United States. The developmental time of both male and female A. papayae and A. loecki was shorter than the developmental time of male and female P. mexicana. Male parasitoids of all three species had a shorter developmental time than their females. All parasitoids had a shorter developmental time in adult-female mealybugs than in second instars. Mating status (unmated and mated) had no effect on the male longevity. Unmated and mated females that were not allowed to oviposit had similar longevity and lived longer than those that were allowed to oviposit. Virgin females produced male only progeny with higher number of males from A. loecki or P. mexicana than from A. papayae. The number of females and the cumulative progeny was smaller for A. papayae than for A. loecki or P. mexicana. The progeny sex ratio (proportion of females) was not different among the parasitoids. A. papayae had the shortest reproductive period followed by A. loecki and P. mexicana, respectively. This information is important in evaluating the efficiency, recovery and establishment of A. papayae, A. loecki, and P. mexicana.Keywords: biological control, mealybug, parasitoids, parasitis

Comparative analysis of pesticide effects on natural enemies in western orchards: A synthesis of laboratory bioassay data

Pesticides are commonly used for pest management in apple, pear and walnut orchards in the western U.S. and may disrupt biological control of secondary pests in these crops. A comparative analysis was made of results obtained from a series of laboratory bioassays of acute mortality and life table response experiments to estimate lethal and sublethal effects of eight pesticides on seven natural enemy species through use of stage-structured population models. Even though a number of the pesticides tested were reduced-risk products, all of them with the exception of copper plus mancozeb and chlorantraniliprole, caused more than 80% acute mortality of at least one life stage of at least one of the natural enemy species at a full field-rate concentration and could thus be considered moderately harmful according to the International Organization for Biological Control classification for laboratory bioassays. Important sublethal effects included reductions in daily fecundity and egg fertility. From integration of the lethal and sublethal effects in matrix models, the mean of the estimated intrinsic rates of increase for natural enemy species was negative for exposure to cyantraniliprole, lambda-cyhalothrin and spinetoram, but positive and not significantly different from the control for exposure to chlorantraniliprole, copper plus mancozeb, novaluron, and sulfur. For comparisons among pesticides, there appears to be considerable variation in response among natural enemy species that can only be represented effectively from a full life table response experiment and a population-level endpoint, whereas among natural enemy species, their population-level response to the range of pesticides tested could frequently be represented by acute adult mortality alone

Effect of non-nutritive sugars to decrease the survivorship of spotted wing drosophila, Drosophila suzukii

In this study, we investigated the effects of non-nutritive sugars and sugar alcohols on the survivorship of spotted wing drosophila, Drosophila suzukii, and found erythritol and erythrose as potentially insecticidal to the fly. In a dose-dependent study, erythritol and erythrose significantly reduced fly longevity, with 100% mortality with 1, 0.5, 0.1 & 0.05 M doses after feeding for 7 days. When sucrose and erythritol solutions were provided separately to flies for 7 days, there was no effect on survivorship regardless of erythritol concentrations. However, with a serial combination of sucrose and erythritol solutions, fly survivorship was significantly decreased for the same period. Also, the higher dose of erythritol regardless of the sucrose dose combined showed greater mortality. In a no-choice assay, D. suzukii ingested more erythritol than sucrose or water, indicating the fly continuously fed on erythritol for 72 h. Also under no-choice conditions, erythritol and sucrose-fed flies gained more weight than water-fed flies. However, in two-choice assays, the amount of erythritol ingested was less than sucrose or water. Total sugar and glycogen levels among erythritol and erythrose-fed flies were significantly less than mannitol, sorbitol, xylitol, and sucrose-fed flies after 48 h. This indicates that these two non-nutritive sugars can’t be used a substrate for enzymes involved in sugar metabolism. Although the metabolism of erythritol and erythrose is unknown in insects, the mortality of D. suzukii flies ingesting these sugars might be caused by two potential physiological changes. The fly is starved by feeding of non-metabolizable erythritol and erythrose, or experiences abnormally high osmotic pressure in the hemolymph with erythritol molecules diffused from the midgut. Non-nutritive sugars might be used as an insecticide alone or combined with conventional or biological insecticides to enhance efficacy. If other sugar sources are present, a palatable sugar might be mixed with erythritol to elicit feeding

Large-plot field studies to assess impacts of newer insecticides on non-target arthropods in Western U.S. orchards

The non-target impacts of two reduced risk insecticides, chlorantraniliprole and spinetoram, were evaluated for two years in Oregon pear and California walnut orchards. Experiments were conducted in large replicated plots (approximately 0.25–0.4ha) to assess the impact of these two insecticides on natural enemies of secondary pests when applied against codling moth, Cydia pomonella. Cumulative insect days (CID) of secondary pests and natural enemies were calculated from leaf samples, plant volatile traps, beat trays or cardboard trunk bands. Ratios of natural enemies and prey were also calculated. Results from these field studies demonstrate that applications of chlorantraniliprole can reduce abundance of predatory Neuroptera and that spinetoram negatively impacts parasitic Hymenoptera. However, these trends did not always occur each year. As a percentage among all trials within a crop, there were more treatment differences for natural enemy/prey ratios (50 and 33% for pears and walnut plots, respectively) than for natural enemy CIDs (25 and 13% for pears and walnut plots, respectively). It is likely that unseasonably cool weather during the two years of this study impacted both pest and natural enemy abundance. The intrinsic value of large-plot field studies is discussed