Efficacy of Herbivore-Induced Plant Volatile Methyl Salicylate in Evaluating the Seasonal Abundance of Herbivorous Thrips (Thysanoptera: Thripidae) in Sweet Pepper.

Herbivorous thrips that damage fruits, vegetables, field crops, and ornamentals are challenging to control using insecticides and need an integrated approach (IPM) for their management. Herbivore-induced plant volatiles (HIPVs) are semiochemical plants produced to attract natural enemies (NEs) of arthropod herbivores. Sex pheromones are animal-based semiochemicals that can attract males or females of conspecifics. The HIPV methyl salicylate (MS) is used in IPM to attract NEs. We conducted field experiments in 2018-2019 in Tennessee to study the efficacy of MS and the aggregation pheromone neryl (S)-2-methylbutanoate (NMB), which attracts Frankliniella occidentalis (FO), a dominant pest of many crops, in attracting thrips using sweet peppers. We found a significantly higher number of thrips in traps baited with MS than in the traps containing NMB when compared with a no-lure control. All treatments caught only one thrips species, Frankliniella tritici (FT), a significant pest of young cotton. It can also lower the abundance of FO in other crops. Our findings show that although FO was not found in the study location in Tennessee, traps baited with MS are suitable for managing FT and reducing FO in susceptible crops by increasing FT and attracting NEs to crop productions that use IPM-based management practices.

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.

Residual Effects of Insecticides on Deraeocoris brevis (Hemiptera: Miridae).

Deraeocoris brevis (Uhler) is a key predatory natural enemy of insects and mites in pear orchards in the United States. Insecticides used for crop protection in pear orchards and their residues can negatively affect populations of D. brevis. The focus of this study was to investigate the field-aged residual effects of lambda-cyhalothrin, spinetoram, and chlorantraniliprole insecticides on D. brevis through contact exposure. An airblast sprayer was used to apply the high label rate of insecticides on pear trees. Leaves were collected from the experimental trees at 1 d after treatment (DAT) and then at 7-d intervals up to 21 DAT. Adults and nymphs were exposed to leaves with insecticide residues or untreated control for 72 h in the laboratory. The nymphs that survived the treatments were reared until they emerged as adults. The surviving paired adults were reared until death. The treated nymphs were assessed for acute mortality, survival, developmental time, and the sex ratio if they emerged as adults. The treated adults were assessed for acute and chronic mortality, fecundity, fertility, and longevity. Both nymphs and adults exposed to leaf residues of lambda-cyhalothrin had significantly higher acute mortality compared with the insects exposed to the control. When compared with the control treatment, the toxicity of field-aged residues of lambda-cyhalothrin, chlorantraniliprole, and spinetoram can persist over a longer period of time. Similar patterns were observed in previous laboratory and field experiments on D. brevis. We discuss the residual effects of three insecticides through contact exposure of D. brevis.

Field-Aged Insecticide Residues on Chrysoperla johnsoni (Neuroptera: Chrysopidae).

We studied the direct (lethal) and indirect (sublethal) effects of field-aged insecticide residues of spinetoram, chlorantraniliprole and lambda-cyhalothrin on adults and larvae of the green lacewing, Chrysoperla johnsoni Henry, Wells and Pupedis an important generalist predator in western United States pear orchards. We applied formulated pesticides using their high label rates mixed with 935 liters/ha of water on pear trees utilizing an airblast sprayer. We collected leaves from the experiment trees at 1, 7, 14, 21 days after treatment (DAT) and exposed C. johnsoni adults and second instars to insecticide residues or untreated control for 72 h. We monitored larvae that survived the treatments until adult emergence (for larvae) or adults until death (for paired adults). We assessed the adults for acute and chronic mortality, longevity, fecundity, and fertility, and larvae for acute mortality, sex ratio, developmental time, and survival of adults emerged from treated second instars, to determine lethal and sublethal effects. The field-exposed insecticide residues of chlorantraniliprole exhibited higher lethal and sublethal toxicities on C. johnsoni during the 21-d leaf collection period when compared with the field-exposed residue toxicities of lambda-cyhalothrin and spinetoram. The field-exposed residue of lambda-cyhalothrin and spinetoram exhibited moderate toxicities on C. johnsoni during the 21-d leaf collection period. Results from this study show similar trends with previous studies using multiple routes of exposure laboratory assays and field experiments on Chrysoperla sp. The direct and indirect effects of field-aged residues of spinetoram, chlorantraniliprole, and lambda-cyhalothrin on C. johnsoni are discussed.

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.

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 & 0.05M doses after feeding for 7days. When sucrose and erythritol solutions were provided separately to flies for 7days, 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 72h. 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 48h. 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.

Life history comparison of two green lacewing species Chrysoperla johnsoni and Chrysoperla carnea (Neuroptera: Chrysopidae).

We investigated the life histories of two green lacewing species, Chrysoperla johnsoni Henry, Wells, and Pupedis from western North America, and Chrysoperla carnea (Stephens) (Neuroptera: Chrysopidae) from western Europe in the laboratory. There were both similarities and differences in their life history characteristics. C. johnsoni exhibited a significantly longer developmental time for egg, first instar, and pupal stage than C. carnea. C. carnea exhibited a significantly shorter egg to adult developmental time than C. johnsoni. Except for the pupal stage, the survival of all other life history stages was not species-specific. All C. carnea pupae were able to develop into adults, whereas only 92% of adult eclosion was observed from C. johnsoni pupae. There was no difference in egg to adult survival between the two species. Adult longevity was not species- or gender-specific. Sex ratio of emerged adults was ≈50% in both species. C. johnsoni had a longer preoviposition period than C. carnea, while the oviposition period was similar for both species. C. carnea had higher lifetime fecundity and fertility than C. johnsoni, as measured by total number of eggs laid and production of fertile eggs, respectively. Egg viability did not differ between the two species. Intrinsic rates of increase (rm) for C. carnea and C. johnsoni were 0.161 and 0.132, respectively. All lacewings used in this experiment were laboratory reared under environmental conditions similar to field as possible. This is the first available information on the life history parameters of C. johnsoni.

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 approximately 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.

Effect of temperature on the life history of the mealybug Paracoccus marginatus (Hemiptera: Pseudococcidae).

Effect of temperature on the life history of the mealybug Paracoccus marginatus Williams & Granara de Willink (Hemiptera: Pseudococcidae) was investigated in the laboratory. P. marginatus was able to develop and complete its life cycle at 18, 20, 25, and 30 +/- 1 degrees C. At 15, 34, and 35 degrees C, the eggs hatched after 27.5, 5.9, and 5.5 d of incubation, respectively, but further development of the first-instar nymphs was arrested. No eggs hatched at 37 degrees C. The developmental time for egg to adult was the longest at 18 degrees C for both males and females. Approximately 80-90% of the eggs survived between 20 and 30 degrees C. The highest fecundity was at 25 degrees C with each female producing an average of 300 eggs. Adult longevity, and preoviposition and oviposition periods increased with decreasing temperature up to 25 degrees C. The proportion of females was approximately 42% at 25 degrees C and was between 70 and 80% at 18, 20, and 30 degrees C. Adult males and females required 303.0 and 294.1 degree-days (DD), respectively, to complete their development. The estimated minimum temperature thresholds for the adult males and females were 14.5 and 13.9 degrees C, respectively. For adult males, the estimated optimum and maximum temperature thresholds were 28.7 and 31.9 degrees C; and for adult females, they were 28.4 and 32.1 degrees C, respectively. The ability of P. marginatus to develop, survive, and reproduce successfully between 18 and 30 degrees C suggests that it has the capability to develop and establish in areas within this temperature range.

Effect of temperature on efficacy of insecticides to differential grasshopper (Orthoptera: Acrididae).

The effect of temperature on activity of insecticides for controlling grasshoppers in leafy green vegetables was evaluated. Insecticides evaluated had differing modes of action and included diflubenzuron, azadirachtin, Beauveria bassiana, spinosad, endosulfan, esfenvalerate, and naled. We evaluated these insecticides for efficacy to third instars of differential grasshopper, Melanoplus differentialis (Thomas), at temperatures ranging from 10 to 35 degrees C. In the laboratory, treatment with esfenvalerate resulted in 100% mortality at temperatures of 10 to 35 degrees C, and efficacy was not temperature dependent. Treatment with spinosad resulted in similar mortality as with esfenvalerate at all temperatures except 10 degrees C. The activity of B. bassiana was greatest at 25 degrees C and was adversely affected by high and low temperatures. Treatment with diflubenzuron resulted in increased mortality at high temperatures, and at 35 degrees C its activity was similar to that of esfenvalerate and spinosad. The activity of azadirachtin ranged from 19 to 31% and was not influenced by temperature. In field studies, spinosad, diflubenzuron, and esfenvalerate provided differing levels of mortality both at application and when nymphs were exposed to 1-h-old residues. However, only spinosad and diflubenzuron provided similar levels of mortality when nymphs were exposed to 24-h-old residues. The residual activity of endosulfan, naled, esfenvalerate, and spinosad decreased with increasing time (0-24 h) after exposure to sunlight and high summer temperatures. Compared with other insecticides, naled had a short residual activity period and activity was dependent upon immediate contact with the nymphs or their substrate. B. bassiana was inactive under high temperatures and intense sunlight as occurs in summer.