Age-Dependent Movement Patterns of Japanese Beetle and European Chafer (Coleoptera: Scarabeidae) Grubs in Soil-Turfgrass Microcosms

Movement patterns of japanese beetle, Popillia japonica Newman, and European chafer, Rhizotrogus (Amphimallon) majalis (Razoumowsky), grubs as influenced by gravity, host plant position, and external disturbances were studied in laboratory soil-turfgrass microcosms. Second through third instars just before pupation were monitored using radiographic techniques. Neonates were monitored using destructive sampling. Results demonstrate significantly different movement patterns between species and among age groups. The development stage of the grub had a large effect on Japanese beetle grub behavior and a measurable, but lesser effect, on European chafers. All larval stages of European chafers and all larval stages of Japanese beetle, except neonates and postoverwintering third instars, displayed a downward movement in response to disturbance. Neonate Japanese beetles showed little movement while postoverwintering. Japanese beetles moved upward when disturbed. European chafer grubs of all age classes displayed random vertical movement with some arrestment in or near sod. Preoverwintering and postoverwintering third-instar chafers showed less dramatic arrestment behavior than other instars tested. Second-instar Japanese beetles behaved similarly to European chafers; however, third instars behaved very differently. All third instars except those tested in late winter and early spring showed some innate downward movement in the soil microcosms. Japanese beetles tested in late winter displayed random movement with some arrestment in sod, whereas those tested in early spring exhibited upward movement and arrestment in so

Oviposition Model for Timing Insecticide Sprays Against Plum Curculio (Coleoptera: Curculionidae) in New York State

Plum curculio, Conotrachelus nenuphar (Herbst), feeding and oviposition on apples during spring was measured for 3 yr in a heavily infested orchard in New York State. A logistic model was formulated to relate cumulative fruit injury to cumulative heat units (degree-days base 10°C [DD10]) following petal fall. Cumulative plum curculio injury was well described by the model in the trees from which data for the model were collected. However, injury progressed faster and ended earlier in smaller trees at the same site and at a different site, probably because of differences in tree architecture. Field trials showed that protection of the fruit via insecticide residue was no longer necessary after the model predicted that 40% of the cumulative plum curculio oviposition and feeding cycle had been completed (171 DD10 after petal fall). Based on historical weather records, use of the model to schedule insecticide treatments would save 1 insecticide application nearly half the time compared with a standard of 3 insecticide applications. A delay between initial plum curculio feeding and oviposition, which coincides with the petal fall, phenophase, and steadily increasing damage, which is influenced by temperatures after petal fall was observed. The effectiveness of delaying insecticide treatments until the rate of plum curculio damage was rapidly increasing was compared with treatments applied at petal fall. Delaying the 1st insecticide application resulted in higher levels of damage compared with making the 1st treatment immediately after petal fal

Control Decision Rule for European Chafer (Coleoptera: Scarabaeidae) Larvae Infesting Turfgrass

A control decision rule for European chafer, Rhizotrogus (Amphimallon) majalis (Razoumowsky), larvae infesting turfgrass was developed using data from 317 residential sites. Larvae were often abundant enough to cause damage to turf in portions (patches) of properties when average density over an entire site was much less than a damage threshold of 5-10 grubs per 950 cm2. To account for this, an empirical relationship between the size of the largest patch of European chafer larvae at a site and site-wide density was used in the development of the decision rule. Properties with a patch of grubs in excess of ≍30 m2 were deemed to require insecticide treatment. Site characteristics (lawn age, shade, and percentage of Kentucky bluegrass) were related to site-wide density and this relationship was used to formulate a risk assessment system. This system is used to determine whether a site should be sampled or not. Properties that are not sampled are not to be treated. Other treatment decisions are based on the outcome of sampling. The relationship between site-wide density and patch size did not allow clear identification of a density that could be used as a threshold in a sampling program. Therefore, several sampling plans were constructed that classified density according to different threshold values. Operating characteristic functions were used in combination with the aforementioned relationship between density and patch size to calculate two types of errors for each sampling plan: the probability of not treating when treatment was necessary and the probability of treating when treatment was not required. Based on these error functions, a threshold of 0.25 grubs per ll-cm diameter turf plug was advocated. Use of the proposed control decision rule should result in few treatment errors but could lead to considerable reductions in pesticide us

Assays with Commercially Produced Trichogramma (Hymenoptera: Trichogrammatidae) To Determine Suitability for Obliquebanded Leafroller (Lepidoptera: Tortricidae) Control

Laboratory assays were used to compare the ability of commercially produced Trichogramma spp. to parasitize eggs of the obliquebanded leafroller, Choristoneura rosaceana (Harris), in the laboratory and field. Trichogramma platneri Nagarkatti parasitized more obliquebanded leafroller eggs per egg mass than did Trichogramma pretiosum Riley or Trichogramma minutum Riley produced by either of 2 insectaries. T. minutum produced at 1 insectary caused significantly more host mortality by host feeding and repiercing than by parasitism. Variation in parasitoid performance from different insectaries and among shipments from the same insectary was common. Young egg masses were more heavily parasitized than old egg masses. Parasitism increased as the number of conspecific female Trichogramma spp. placed on the same host increased, but the number of eggs parasitized per female decreased. Exposure of host egg masses to female Trichogramma spp. prevented additional oviposition in the same egg mass by conspecific, ovipositionally experienced females but had no effect on parasitism by conspecific, ovipositionally naive females. The method used to attach sentinel egg masses to foliage influenced parasitism rates. Moistening the leaf with water and adhering the egg mass to the moistened leaf had the least impact. Inundative releases of Trichogramma spp. into an apple orchard paralleled laboratory assays by showing greater parasitism of obliquebanded leafroller egg masses by T. platneri than with T. minutum. However, extreme differences observed in field performance between the 2 species was not predicted from the assay

Development and Evaluation of a Control Decision Rule for First-Generation Spotted Tentiform Leafminer (Lepidoptera: Gracillariidae) in New York Apple Orchards

A pest control decision rule consisting of an action threshold and a sampling protocol was developed and evaluated for first-generation spotted tentiform leafminer, Phyllonorycter blancardella (F.). An action threshold of two eggs per leaf was chosen based on the criterion of preventing more than one first-generation mine per leaf. Two sequential classification sampling plans for first-generation eggs were developed, one based on variable intensity sampling and the other on the use of confidence intervals for stop limits. Both plans made use of the nested variance structure of leafminer egg counts and variance-mean models fit to estimated variance components. Performance of the two sequential procedures was studied using simulation and judged to be very similar. Use of either sampling plan required approximately 10-20 min. Over a 4-yr period, 87% of sampled orchards in western New York had leafminer populations that were below the threshold of two eggs per leaf. During this period, use of sample information to schedule insecticide treatments resulted in only one instance when a treatment may have been required and was not called for (n = 79). Widespread use of the decision rule would result in significant reductions in pesticide use with no attendant increase in risk to grower

Behavioral Interactions Between Japanese Beetle (Coleoptera: Scarabaeidae) Grubs and an Entomopathogenic Nematode (Nematoda: Heterorhabditidae) within Turf Microcosms

Distribution of Japanese beetle, Popillia japonica Newman, grubs and dispersal of an entomopathogenic nematode, Heterorhabditis bacteriophora Poinar ‘Oswego' strain (an isolate from New York state), were examined for 5 wk within soil-filled flats containing grass. Japanese beetle grubs uniformly dispersed to all sections of the flats not infested with H. bacteriophora ‘Oswego' strain. In flats infested with H. bacteriophora ‘Oswego' strain, however, greater proportions of Japanese beetle grubs were recovered in sections near the nematode release site or center sections of the flats. H. bacteriophora ‘Oswego' strain dispersed to all sections of the flats but dispersed more rapidly within the flats infested with Japanese beetle grubs than in flats not infested with Japanese beetle grub

Moisture, a Vital but Neglected Factor in the Seasonal Ecology of Insects: Hypotheses and Tests of Mechanisms

Of the major physical factors that influence insect seasonal ecology, moisture is least understood and least appreciated. It is our premise that experimental probing of insects from diverse zones and various habitats would reveal general patterns of insect responses to moisture that are as striking as those for photoperiod and temperature. Using the paradigms of photoperiod and temperature as ecophysiological determinants of insect seasonality, we hypothesize that moisture influences insect life cycles via one or more of three mechanisms—as a token stimulus for diapause, modulator of developmental or reproductive rates, or behavioral cue for vital seasonal events. For heuristic purposes, we offer each of these hypotheses in close association with approaches for testing their validity in insects that undergo dry-season dormancy. The approaches appear appropriate for examining the role of moisture in the life histories of terrestrial invertebrates other than insects, as well as plants and microbes that have a seasonal resting stage. Elucidating moisture's role in insect seasonal cycles is critical to the development of comprehensive phenological models, improved insect management systems, and identification of novel evolutionary mechanisms for adaptation to wet-dry seasons, especially in tropical, subtropical, and Mediterranean region

Neonicotinoid Insecticide Imidacloprid Causes Outbreaks of Spider Mites on Elm Trees in Urban Landscapes

BACKGROUND: Attempts to eradicate alien arthropods often require pesticide applications. An effort to remove an alien beetle from Central Park in New York City, USA, resulted in widespread treatments of trees with the neonicotinoid insecticide imidacloprid. Imidacloprid's systemic activity and mode of entry via roots or trunk injections reduce risk of environmental contamination and limit exposure of non-target organisms to pesticide residues. However, unexpected outbreaks of a formerly innocuous herbivore, Tetranychus schoenei (Acari: Tetranychidae), followed imidacloprid applications to elms in Central Park. This undesirable outcome necessitated an assessment of imidacloprid's impact on communities of arthropods, its effects on predators, and enhancement of the performance of T. schoenei. METHODOLOGY/PRINCIPAL FINDINGS: By sampling arthropods in elm canopies over three years in two locations, we document changes in the structure of communities following applications of imidacloprid. Differences in community structure were mostly attributable to increases in the abundance of T. schoenei on elms treated with imidacloprid. In laboratory experiments, predators of T. schoenei were poisoned through ingestion of prey exposed to imidacloprid. Imidacloprid's proclivity to elevate fecundity of T. schoenei also contributed to their elevated densities on treated elms. CONCLUSIONS/SIGNIFICANCE: This is the first study to report the effects of pesticide applications on the arthropod communities in urban landscapes and demonstrate that imidacloprid increases spider mite fecundity through a plant-mediated mechanism. Laboratory experiments provide evidence that imidacloprid debilitates insect predators of spider mites suggesting that relaxation of top-down regulation combined with enhanced reproduction promoted a non-target herbivore to pest status. With global commerce accelerating the incidence of arthropod invasions, prophylactic applications of pesticides play a major role in eradication attempts. Widespread use of neonicotinoid insecticides, however, can disrupt ecosystems tipping the ecological balance in favor of herbivores and creating pest outbreaks

Interference with the Mate-Finding Communication System of the Obliquebanded Leafroller (Lepidoptera: Tortricidae) Using Synthetic Sex Pheromones

Effect of atmospheric permeation with synthetic sex pheromone on the behavior and control of obliquebanded leafroller, Choristoneura rosaceana (Harris), was studied in small and large plots in commercial apple orchards. Synthetic sex pheromone significantly reduced the ability of male moths to locate pheromone-baited traps and tethered females; however, no differences were found among 3 pheromone rates. Location of pheromone dispensers within the tree canopy did not alter the number of males locating pheromone-baited traps and mating tethered females. Obliquebanded leafroller activity was greatest in the upper positions of the tree canopy and no edge effect was observed around perimeters of large disrupted blocks. The presence of gravid feral females, mated tethered females, high larval densities, and fruit damage within large pheromone disrupted blocks indicate obliqubanded leafrollers mate in orchards treated with synthetic sex pheromone. However, fruit damage caused by obliquebanded leafroller larvae was similar in pheromone, pheromone plus insecticide, and insecticide treatment