Agricultural soil legacy influences multitrophic interactions between crops, their pathogens and pollinators.

Soil legacy influences plant interactions with antagonists and below-ground mutualists. Plant-antagonist interactions can jeopardize plant-pollinator interactions, while soil mutualists can enhance plant-pollinator interactions. This suggests that soil legacy, either directly or mediated through plant symbionts, affects pollinators. Despite the importance of pollinators to natural and managed ecosystems, information on how soil legacy affects plant-pollinator interactions is limited. We assessed effects of soil management legacy (organic versus conventional) on floral rewards and plant interactions with wild pollinators, herbivores, beneficial fungi and pathogens. We used an observational dataset and structural equation models to evaluate hypothesized relationships between soil and pollinators, then tested observed correlations in a manipulative experiment. Organic legacy increased mycorrhizal fungal colonization and improved resistance to powdery mildew, which promoted pollinator visitation. Further, soil legacy and powdery mildew independently and interactively impacted floral traits and floral reward nutrients, which are important to pollinators. Our results indicate that pollination could be an overlooked consequence of soil legacy and suggests opportunity to develop long-term soil management plans that benefit pollinators and pollination.

Functional and Numerical Responses of Trichogramma euproctidis (Hymenoptera: Trichogrammatidae) to Helicoverpa armigera (Lepidoptera: Noctuidae) Under Laboratory Conditions.

The tomato fruitworm Helicoverpa armigera (Hübner) is regarded as a serious pest that affects a great number of field crops globally. One of the environmentally safe alternatives to the utilization of insecticides is controlling H. armigera via the release of biological control agents by employing parasitoids, e.g., trichogrammatid species. One of the desired parasitoids indigenous to southwestern Iran is Trichogramma euproctidis (Girault). To anticipate the outcomes of augmentative releases of T. euproctidis in the field, the numerical and functional responses of female T. euproctidis that parasitizes the eggs of H. armigera were determined in the laboratory. The densities of host eggs per glass tube arena (length: 10 cm, diameter: 1 cm) were 2, 4, 8, 16, 32, 64, or 128 individuals. The functional response to the eggs of H. armigera indicated Holling's type II response. The estimated handling time and attack rate from the random parasitoid equation were 0.6898 h and 0.00823 h, respectively. This indicates that, at the maximum level, each T. euproctidis was capable of parasitizing 34.79 eggs a day. At the 128 host egg density, the number of eggs laid, that is, the numerical response, ascended as the density of host eggs increased up to a maximum of 89.90 eggs per female. According to the obtained results of the present investigation, T. euproctidis can serve as an appropriate candidate for augmentative biological control of H. armigera. Nevertheless, it is necessary to conduct complementary experiments in greenhouses and open fields.

Semiochemical Release and Ontogenetic Changes in a Primary Scent Gland of Podisus maculiventris.

The spined shoulder bug, Podisus maculiventris, is a generalist predator studied for its biocontrol potential. Despite our growing understanding of gland development, the conditions that elicit releases are largely unknown. To determine if male age or gland development affects the chemical composition and release behavior, we dissected adult male bugs and profiled the chemical composition of the male DAG 1, 7, and 14 d post-eclosion. To determine if gland development is related to sexual maturity, we counted the number of sperm present in the seminal vesicles at the same time points. Finally, we measured the diurnal release patterns of different aged males and in various male-female combinations. We observed that newly eclosed adults have under-developed glands and male seminal vesicles contained few sperm. One week post-eclosion the DAG contained previously reported semiochemical compounds and males contained many sperm. Mirroring the trend in reproductive maturation and gland development, the number of semiochemical releases increased with age and the majority of releases followed a scotophase pattern unaffected by sexual composition. These findings link male age to 1) dorsal abdominal gland development 2) release behavior and 3) sexual maturity, which will help our understanding of when these olfactory cues are present for other organisms, like prey, to perceive. Given the results, releasing adults that are at least 1 week post eclosion will maximize the non-consumptive effects of this biocontrol agent.

The effect of UVB-blocking plastics on the efficacy of Beauveria bassiana and a conventional product against Lygus lineolaris on low tunnel strawberry.

BACKGROUND: Effective, safe and practical biocontrol options are greatly needed for combating Lygus lineolaris on protected culture strawberry. This study demonstrated how ultaviolet (UV)-selective plastics can improve the efficacy of the fungal biocontrol agent Beauveria bassiana (Mycotrol) compared to the conventional insecticide acetamiprid (Assail) against L. lineolaris on low tunnel strawberry. RESULTS: We found that UVB-blocking treatments improved B. bassiana spore viability in both in vitro and in vivo laboratory experiments. In the field, survival of Mycotrol-treated sentinel L. lineolaris was lowest under UVB-blocking low tunnels, but this did not translate into significant differences among covering treatments in local L. lineolaris density or fruit damage. In contrast, applying the product Assail resulted in the lowest L. lineolaris density and highest quality yield compared to Mycotrol sprays. This was especially pronounced under low tunnels of any UV-limiting plastic. CONCLUSIONS: This study indicates that growing under low tunnels is a useful tool to improve the efficacy of conventional products and biopesticides containing microbial biocontrol agents. The efficacy of both products was improved under low tunnels, and specifically under UVB-blocking plastics for Mycotrol containing B. bassiana. However, there was little evidence that UVB plastics resulted in lower L. lineolaris densities and proportion of damaged fruit for either product in the field. Therefore we conclude that growing under any plastic covering is likely to benefit growers, but the economic value of growing under UVB tunnels is unclear. © 2022 Society of Chemical Industry.

Effect of Different Constant Temperatures on Life History and Life Table Parameters of Trichogramma euproctidis (Hymenoptera: Trichogrammatidae).

Temperature has a profound effect on performance and behavior of egg parasitoids. Egg parasitoids are a well-known alternative for the control of lepidopterous pests. Selected life history parameters of Trichogramma euproctidis (Girault) (Hymenoptera: Trichogrammatidae), an established egg parasitoid species in Khuzestan- Southwest Iran, were appraised at eight constant temperatures (22.5, 25, 27.5, 30, 32.5, 35, 37.5, and 40°C) using Ephestia kuehniella Zeller (Lepidoptera: Pyralidae) eggs as the host. We found significant effects of temperature on the number of parasitized eggs, development time, sex ratio, progeny's longevity, and fecundity. T. euproctidis developed on E. kuehniella eggs at all temperatures tested, but performed best at 32.5°C. At this temperature, they parasitized the most eggs, produced the most female progeny, and had high rates of survival. Our findings revealed that temperature significantly affected the longevity of female progeny and fecundity of T. euproctidis. A life table analysis confirmed that temperature resulted in optimal effects on T. euproctidis life history. Net reproductive rate (R0) of T. euproctidis was different among the temperatures tested. The intrinsic rate of increase (r) was positively correlated with temperature from 22.5 to 32.5°C and then decreased from 35 to 40°C. Generation time (T) and doubling time (DT) decreased as temperature increased from 22.5 to 37.5°C and then increased at 40°C. These data suggest that this strain of T. euproctidis is adapted to high temperatures and harsh environmental conditions and has the potential to be used in integrated management programs in Southwest Iran.

Predator Performance and Fitness Is Dictated by Herbivore Prey Type Plus Indirect Effects of their Host Plant.

Animals, including herbivores and predators, use diet-mixing to balance their macro- and micronutrient intake. Recent work demonstrated that lady beetles fed only pea aphids from fava beans had reduced fitness caused by a deficiency of dietary sterols. However, beetles redressed this deficit by eating fava bean leaves. In the current study we used Coccinella septempunctata as a model to test the hypotheses that pea aphids are a poor sterol resource independent of their host plant, and that fava beans produce low quality prey regardless of aphid species. Additionally, we tested the reproductive rescue capacity of alfalfa and barley foliage compared to fava, and profiled the sterols of phloem exudates, foliage, and aphids reared on these different hosts. Beetle fecundity and egg viability was significantly better when provided pea aphids reared on alfalfa (compared to fava beans) and green peach aphids reared on fava plants. Alfalfa and barley leaves were not consumed by beetles and did not support beetle reproduction. The sterol profile of aphids largely reflected their host plant phloem. However, green peach aphids from fava acquired 125-times more sterol than pea aphids from fava. Our findings show how the sterol content of different host-plants can affect the third trophic level. Our results suggest that 1) prey quality varies depending on prey species, even when they occur on the same plant, 2) plant species can mediate prey quality, 3) host plant-mediated effects on prey quality partially drive omnivory, and 4) diet-mixing benefits growth and reproduction by redressing micronutrient deficits.

Herbivory improves the fitness of predatory beetles.

While many predatory arthropods consume non-prey foods from lower trophic levels, little is known about what drives the shift from predator to omnivore. Predatory lady beetles often consume non-prey foods like plant foliage and pollen. One species, Coccinella septempunctata, eats foliage to redress sterol deficits caused by eating sterol-deficient prey. Here we explore how omnivory benefits lady beetle fitness. We reared seven species of lady beetles-from five genera distributed across the tribe Coccinellini-on pea aphids in the presence or absence of fava bean foliage; pea aphids have very low sterol content. Foliage supplements lengthened the development times of four species and decreased survival to adulthood of two species; it had no effect on adult mass. We mated beetles in a 2 × 2 factorial design (males with or without foliage paired with females with or without foliage). For each species, we observed a profound paternal effect of foliage supplements on fitness. Females mated to foliage-supplemented males laid more eggs and more viable eggs compared to females mated to non-supplemented males. Foliage-supplemented males produced 2.9-4.6 times more sperm compared to non-supplemented males for the three species we examined. We analysed the sterol profile of four beetle species reared on pea aphids-with or without foliage-and compared their sterol profile to field-collected adults. For two laboratory-reared species, sterols were not detected in adult male beetles, and overall levels were generally low (total ng of sterol/beetle range: 3-33 ng); the exception being Propylea quatuordecimpunctata females (total ng of sterol/beetle range: 50-157 ng). Laboratory-reared lady beetle sterol content was not significantly affected by the presence of foliage. Field-collected beetles had higher levels of sterols compared to laboratory-reared beetles (2,452-145,348 ng per beetle); cholesterol and sitosterol were the dominant sterols in both field-collected and laboratory-reared beetles. Our findings indicate that herbivory benefits lady beetle fitness across the Coccinellini, and that this was entirely a paternal effect. Our data provide a rare example of a nutritional constraint impacting fitness in a sex-specific manner. It also shows, more broadly, how a nutritional constraint can drive predators towards omnivory.

Prey nutrient content creates omnivores out of predators.

The proximate forces that create omnivores out of herbivores and predators have long fascinated ecologists, but the causal reasons for a shift to omnivory are poorly understood. Determining what factors influence changes in trophic position are essential as omnivory plays a central role in theoretical and applied ecology. We used sevenspotted lady beetles (Coccinella septempunctata) to test how prey nutrient content affects beetles' propensity to engage in herbivory. We show that beetles consuming an all-prey diet demonstrate normal growth and development, but suffer a complete loss of fitness (spermatogenic failure) that is restored via herbivory and supplementation with phytosterols and cholesterol. Furthermore, we show that lady beetles possess a state-dependent sterol-specific appetite and redressed their sterol deficit by feeding on foliage. These results demonstrate that predators balance their nutrient intake via herbivory when prey quality is low, and reveal a selective force (sterol nutrition) that drives predatory taxa to omnivory.

An Assessment of the Physiological Costs of Autogenous Defenses in Native and Introduced Lady Beetles.

Many lady beetles expel an autogenously produced alkaloid-rich 'reflex blood' as an antipredator defense. We conducted an experiment to determine whether there was a measurable fitness cost associated with the daily induction of this defensive behavior, and whether costs differed between native (Coccinella novemnotata Herbst (Coleoptera: Coccinellidae)) and invasive species (Coccinella septempunctata L. (Coleoptera: Coccinellidae) and Harmonia axyridis (Pallas) (Coleoptera: Coccinellidae)). Newly mated females were provided a restricted or unrestricted amount of aphids and were bled for 10 d. We measured the mass of reflex blood produced and the total number and viability of eggs laid per day. The amount of reflex blood released per day increased for C. septempunctata at the restricted level and did not change for any other species-diet level combination. We did not detect a significant cost of reflex bleeding on the quantity or viability of eggs laid by any species, even at the restricted aphid level. Remarkably, bled individuals at the ad libitum level laid significantly more viable eggs compared to controls. All species laid significantly fewer total eggs (49-69% fewer) at the low versus high aphid level. These results demonstrate that while resource scarcity has a negative impact on fecundity, repeated use of the reflex bleeding defense system does not. These results support the findings of other reports and strongly suggest that adult lady beetles incur no measurable physiological costs related to the induction of the reflex-bleeding defense.

Interactions of Coccinella novemnotata (Coleoptera: Coccinellidae) and Coccinella septempunctata (Coleoptera: Coccinellidae) While Foraging for Aphids.

The importation and establishment of Coccinella septempunctata L. (Coleoptera: Coccinellidae) in North America purportedly caused the displacement and local extirpation of the native ninespotted lady beetle, Coccinella novemnotata Herbst (Coleoptera: Coccinellidae), across most of its former range, and several reports have shown that C. septempunctata maintains competitive advantages over C. novemnotata. We investigated the role of aphid density on the retention time of these two species on fava bean plants, and the effect of con- versus heterospecific pairings of adult beetles on the foraging behavior of C. novemnotata. We found that aphid density did not affect C. novemnotata's retention time, but did affect the retention time of C. septempunctata, which left plants without aphids significantly faster than C. novemnotata. Additionally, C. septempunctata females left plants significantly faster than their male counterparts, whereas we observed no difference between the two sexes for C. novemnotata. Our test of pairs of beetles showed that C. novemnotata were together on plants more frequently than conspecific pairs of C. septempunctata and heterospecific pairs of beetles, and that all beetles were more likely to be found together on the aphid-infested plant versus the non-infested plant regardless of the pairs' composition. These results show that C. novemnotata spend more time foraging for aphids when aphids are scarce compared with C. septempunctata, and that C. novemnotata is less tolerant of occupying plants inhabited by C. septempunctata versus a conspecific beetle, adding additional mechanisms whereby C. septempunctata could outcompete C. novemnotata in the field.

Interactions of the Asian Lady Beetle, Harmonia axyridis (Coleoptera: Coccinellidae), and the North American Native Lady Beetle, Coccinella novemnotata (Coleoptera: Coccinellidae): Prospects for Recovery Post-Decline.

The decline of the North American native lady beetle, Coccinella novemnotata Herbst, is strongly correlated with the introduction of Coccinella septempunctata L., and C. novemnotata are locally extirpated across much of the United States. Since C. novemnotata's decline, the invasive Harmonia axyridis Pallas has become dominant in North America. This study investigated whether H. axyridis has the potential to impede the recovery of C. novemnotata populations. To determine how H. axyridis interacts with C. novemnotata via intraguild predation and competition for prey, we paired first-instar C. novemnotata with first-instar H. axyridis at low and high densities of pea aphid. Coccinella novemnotata survival when paired interspecifically was significantly lower than H. axyridis survival at both aphid densities. Both species had similar weights at eclosion across aphid densities; however, H. axyridis developed faster than C. novemnotata. To examine the effect of larval size on intraguild interactions, we conducted a second experiment where we varied the C. novemnotata and H. axyridis instar in our pairings. Coccinella novemnotata survival and final weight increased when paired with younger H. axyridis larvae. The percentage survival of C. novemnotata in interspecific treatments, at the low aphid density, was lower than for same-aged C. novemnotata reared conspecifically, except for pairs initiated with C. novemnotata larvae that were two instars more advanced than H. axyridis larvae. These results suggest that intraguild predation and competition for prey by H. axyridis have the potential to affect the recovery of C. novemnotata populations negatively.

Intraguild Interactions of Native and Introduced Coccinellids: The Decline of a Flagship Species.

The decline of Coccinella novemnotata Herbst, the ninespotted lady beetle, across North America has been attributed to the introduction of Coccinella septempunctata L. It has been suggested that C. septempunctata negatively impacted C. novemnotata through a combination of mechanisms. We investigated the effects of scramble competition and intraguild predation between groups of C. septempunctata and C. novemnotata. A novel aspect of these experiments for this species combination was that we provided beetles the option to cannibalize conspecifics or predate on heterospecifics (i.e. intraguild predation); thus, we were able to compare interspecific versus intraspecific competition. Increasing prey density resulted in significantly lower rates of intraguild predation on C. novemnotata by C. septempunctata. Percentage survival of C. novemnotata grouped with C. septempunctata at low and high aphid densities was 6 and 61%, respectively. For our second study, we increased the spatial complexity and volume of the assay system, and provided prey ad libitum. C. novemnotata survival from first-instar to adult was significantly lower than C. septempunctata survival when grouped heterospecifically (43 vs 61% survival, respectively). Finally, we conducted a study to determine if hungry larvae discriminate conspecific versus heterospecific larvae by testing whether they predated selectively on the basis of species, which they did not appear to do. We conclude that C. novemnotata larvae suffer greater rates of intraguild predation from C. septempunctata compared with cannibalism, that this difference appears to be due to size asymmetry between the two species, and that local conditions impact the severity of intraguild predation by C. septempunctata.

Egg Predation by the Introduced Lady Beetle, Coccinella septempunctata (Coleoptera: Coccinellidae), Lowers Mortality but Raises Relative Risk for the Native Lady Beetle, Coccinella novemnotata.

Populations of the native ninespotted lady beetle, Coccinella novemnotata Herbst, have undergone precipitous declines in North America following the establishment of the exotic sevenspotted lady beetle, Coccinella septempunctata L. Recent volunteer efforts have made it possible to establish colonies of the now-rare C. novemnotata and test mechanisms contributing to its decline. We evaluated the relative frequencies of intraguild predation and cannibalism of eggs between these two species. A single C. novemnotata or C. septempunctata adult was exposed to conspecific and heterospecific eggs in either the presence or absence of pea aphids. The study revealed two expected results: 1) eggs of C. novemnotata were consumed more frequently than eggs of C. septempunctata by both species, and 2) egg consumption was higher when aphids were absent, independent of predator and egg species. There were also two unexpected results from the study: 1) the asymmetry between egg predation rates was higher when aphids were present, and 2) higher predation rates on C. novemnotata eggs in the absence of alternate prey was due to a relatively higher rate of intraspecific cannibalism. This implies that C. novemnotata would have suffered higher egg mortality rates before the invasion of C. septempunctata, but even though the aggregate rate of egg predation on C. novemnotata eggs is lower post-invasion, it is still significantly higher than the aggregate rate of predation of C. septempunctata eggs. This differential pattern of asymmetric predation could contribute to habitat compression and the overall decline of C. novemnotata.

Community composition and population genetics of insect pathogenic fungi in the genus Metarhizium from soils of a long-term agricultural research system.

Fungi in the genus Metarhizium are insect pathogens able to function in other niches, including soil and plant rhizosphere habitats. In agroecosystems, cropping and tillage practices influence soil fungal communities with unknown effects on the distribution of Metarhizium, whose presence can reduce populations of crop pests. We report results from a selective media survey of Metarhizium in soils sampled from a long-term experimental farming project in the mid-Atlantic region. Field plots under soybean cultivation produced higher numbers of Metarhizium colony-forming units (cfu) than corn or alfalfa. Plots managed organically and via chisel-till harboured higher numbers of Metarhizium cfu than no-till plots. Sequence typing of Metarhizium isolates revealed four species, with M. robertsii and M. brunneum predominating. The M. brunneum population was essentially fixed for a single clone as determined by multilocus microsatellite genotyping. In contrast, M. robertsii was found to contain significant diversity, with the majority of isolates distributed between two principal clades. Evidence for recombination was observed only in the most abundant clade. These findings illuminate multiple levels of Metarhizium diversity that can be used to inform strategies by which soil Metarhizium populations may be manipulated to exert downward pressure on pest insects and promote plant health.

The effect of time postexposure and sex on the horizontal transmission of Metarhizium brunneum conidia between Asian longhorned beetle (Coleoptera: Cerambycidae) mates.

A study using Metarhizium brunneum Petch fungal bands designed to improve delivery of conidia to adult Asian longhorned beetles, Anoplophora glabripennis (Motschulsky), was conducted to determine how a time delay between exposure to infective conidia and pairing of male and female beetles would affect the ability to successfully transfer lethal doses of conidia to a mate. We measured conidial load at the time of mate pairing (0, 4, 24, 48 h postexposure) and assessed its effect on beetle mortality. Conidial load per beetle decreased across the four sampling times, and there was no effect of beetle sex on conidial load. At all time periods postexposure, beetles that climbed across fungal bands carried enough conidia that at least some of their indirectly exposed mates died of mycosis. For indirectly exposed beetles, mortality decreased significantly as the time delay increased from 0 to 48 h, and this was independent of beetle sex. Median survival time was only 11.5 d for females indirectly exposed immediately after their mate had been exposed, but >3 wk when there was a 48-h delay before pairing. Generally, beetles exposed directly to fungal bands died faster than their indirectly exposed mates. In contrast to the pattern seen for indirectly exposed beetles, beetles exposed directly to fungal bands showed no change in survival times with a delay between exposure and pairing. Median survival times of exposed females and males were generally similar, at 10.5-12.5 d.

Development times and age-specific life table parameters of the native lady beetle species Coccinella novemnotata (Coleoptera: Coccinellidae) and its invasive congener Coccinella septempunctata (Coleoptera: Coccinellidae).

To determine if differences in life history parameters contribute to native species exclusion, immature development times, larval survivorship, reproductive life history parameters, and age-specific life tables were determined for two populations (eastern United States and western United States) of ninespotted lady beetles (Coccinella novemnotata Herbst) and one population of sevenspotted lady beetles (Coccinella septempunctata L.). Developing larvae were provided an ad libitum diet of pea aphids (Acyrthosiphon pisum Harris) at a constant temperature of 25°C. The first and fourth larval stadia of C. novemnotata were significantly longer than that of C. septempunctata, as was their total development time from egg to newly eclosed adult. Stage-specific developmental mortality was low for both species and did not exceed 7% for the entire development period. The preoviposition period of the two C. novemnotata populations was significantly shorter (15-20%) than that of C. septempunctata. C. novemnotata from both locations laid significantly fewer total eggs than C. septempunctata (34-40% fewer) over the 31-d test period, and also fewer eggs per day (37-43% fewer). The net reproductive rate of the C. novemnotata populations was 42-50% lower than that of C. septempunctata as was C. novemnotata's intrinsic rate of natural increase (rm: 0.1716 and 0.1840 vs. 0.1959 for western and eastern C. novemnotata and C. septempunctata, respectively).

Effect of prey limitation on competitive interactions between a native lady beetle, Coccinella novemnotata, and an invasive lady beetle, Coccinella septempunctata (Coleoptera: Coccinellidae).

The size and geographic distribution of Coccinella novemnotata Herbst populations have been decreasing rapidly across North America closely following the establishment, spread, and population growth of the invasive seven-spotted lady beetle, Coccinella septempunctata L. To determine whether intraguild predation and competition for prey may be partially responsible for the decline, we paired first-instar larvae of two populations of C. novemnotata (eastern and western) with first-instar C. septempunctata at low or high aphid densities. Survival of both C. novemnotata populations was significantly lower when larvae were paired with C. septempunctata, and western C. novemnotata exhibited significantly lower survival compared with the eastern population. This relationship depended on aphid density with the greatest survival of both C. novemnotata populations occurring at the high aphid density. Both male and female C. novemnotata weighed less on the day of eclosion when paired with C. septempunctata as compared with pairings with conspecifics. In a second test, C. septempunctata and C. novemnotata instars were varied at the start of the trial and C. novemnotata survival to adulthood in the presence of C. septempunctata was dependent of the instar of C. novemnotata used to initiate the experiment. C. novemnotata exhibited higher rates of survival and weighed significantly more on the day of eclosion when C. novemnotata was older than its C. septempunctata partner. These results suggest that interspecific competition including intraguild predation by C. septempunctata may contribute to C. novemnotata population declines, but that the intensity of this impact may vary across C. novemnotata populations.

The within-season and between-tree distribution of imidacloprid trunk-injected into Acer platanoides (Sapindales: Sapindaceae).

Norway maple trees, Acer platanoides L. (Sapindales: Sapindaceae), that were trunk-injected with imidacloprid as part of an Asian longhorned beetle eradication program, were used to study the temporal and between-tree distribution of imidacloprid in twigs from June through September. The effect of injection time during spring on imidacloprid residues across the summer season and the distribution of imidacloprid in twig bark versus twig xylem were also investigated. Overall, we observed a significant decline in imidacloprid concentrations within each plant part sampled across the study period, although the 19 trees used in the study varied greatly in the pattern of imidacloprid residues over time. The concentration of imidacloprid in twig bark per dry mass was approximately two times higher than that of the twig xylem (means +/- SD of 1.21 +/- 2.16 ppm vs. 0.63 +/- 1.08 ppm imidacloprid, respectively). The majority (> 50%) of whole twig, twig bark and twig xylem samples from injected trees contained < 1 ppm imidacloprid and 37% of twig samples contained 0 ppm. Maximum values were 9 ppm for whole twigs from trunk-injected trees, 12 ppm imidacloprid for twig bark, and 5 ppm for twig xylem. Leaves, sampled only in September, had much higher imidacloprid residues than twigs collected at the same time; the majority (53%) of leaf samples contained > 5 ppm imidacloprid, with a maximum of 49 ppm. The concentrations ofimidacloprid in whole twigs, twig bark, and twig xylem were highly correlated, and levels in leaves were correlated with imidacloprid levels in whole twigs.

Conidial acquisition and survivorship of adult Asian longhorned beetles exposed to flat versus shaggy agar fungal bands.

Fungal bands can deliver lethal conidial doses to adult Asian longhorned beetles. Because higher doses result in shorter survival times, developing a method to deliver more conidia to beetles walking across the fungal bands is desirable. We compared fungal bands made using standard flat material to bands made using a shaggy, textured material. The median survival time of adult beetles exposed to shaggy bands was reduced to 10 d versus 18 d for beetles exposed to flat bands. Beetles climbing across shaggy bands acquired 1.83×10(6) conidia per beetle, which was 14.6 times greater than beetles exposed to flat bands.

Comparing fungal band formulations for Asian longhorned beetle biological control.

Experiments were conducted with the fungal entomopathogen Metarhizium brunneum to determine the feasibility of using agar-based fungal bands versus two new types of oil-formulated fungal bands for Asian longhorned beetle management. We investigated conidial retention and survival on three types of bands attached to trees in New York and Pennsylvania: standard polyester fiber agar-based bands containing fungal cultures, and two types of bands made by soaking either polyester fiber or jute burlap with oil-conidia suspensions. Fungal band formulation did not affect the number or viability of conidia on bands over the 2-month test period, although percentage conidial viability decreased significantly with time for all band types. In a laboratory experiment testing the effect of the three band formulations on conidial acquisition and beetle survival, traditional agar-based fungal bands delivered the most conidia to adult beetles and killed higher percentages of beetles significantly faster (median survival time of 27d) than the two oil-formulated materials (36-37d). We also tested the effect of band formulation on conidial acquisition by adult beetles kept individually in cages with a single band for 24h, and significantly more conidia (3-7times) were acquired by beetles from agar-based bands compared to the two oil formulations.