Patrick C. Tobin

Dispersal and Spatiotemporal Dynamics of Asian Longhorned Beetle (Coleoptera: Cerambycidae) in China

Abstract We studied dispersal and spatiotemporal dynamics of the Asian longhorned beetle, Anoplophora glabripennis Motschulsky, in Gansu Province of north central China. We used mass mark–recapture methods and observed that 98% of beetles were recaptured within 920 m from a release point, whereas the median dispersal rate for all recaptured adults was 30 m/d. Dispersal potential within the course of a season for males and gravid females was 2,394 and 2,644 m, respectively; however, more work is needed to evaluate the potential of long-distance dispersal events to initiate new colonies outside current U.S. quarantine boundary guidelines. We observed that tree size and number of existing emergence holes on a tree were significant positive predictors of new emergence holes, but we did not measure a significant effect of tree size, number of existing emergence holes, and number of new emergence holes on adult beetle abundance. Implications of these findings within the context of host quality are discussed, but more research is needed to identify key factors in the multiyear host colonization process. Peak population abundance of unmarked beetles (i.e., background populations) in both 1999 and 2000 occurred between 800 and 900 degree-days (base threshold = 10°C) from 1 January. Background populations exhibited local spatial autocorrelation during peak abundance, with ranges of spatial dependence of 229–543 m. The implications of this study are discussed in reference to the role that A. glabripennis population biology plays in the current eradication effort.

Modeling Development in Grape Berry Moth (Lepidoptera: Tortricidae)

Abstract We modeled development in grape berry moth, Endopiza viteana (Clemens), which exploits wild and cultivated Vitis. Laboratory experiments were used to derive the temperature-dependent developmental curve for eggs, larvae, and pupae. We used linear interpolation to estimate stage-specific base temperature thresholds and degree-day requirements under laboratory conditions. We also estimated parameters of the Logan and Lactin nonlinear developmental models. Lastly, we conducted field experiments to evaluate the conventional degree-day model, which has a base threshold of 10°C; an improved degree-day model that was based on our laboratory observations; and nonlinear developmental models in predicting seasonal grape berry moth development. We concluded that the Logan nonlinear model provided the best estimates of grape berry moth field development, and an improved degree-day model should use 8.41°C as a minimum base temperature threshold and 423.9 as the egg-to-adult degree-day requirement. Also, after comparing degree-day accumulation estimates using the maximum-minimum method and trapezoidal integration to hourly temperature measurements, we concluded that the two approaches provided similar estimates during June–September.

Phenology of Grape Berry Moth (Lepidoptera: Tortricidae) in Cultivated Grape at Selected Geographic Locations

Abstract The grape berry moth, Endopiza viteana (Clemens) feeds on wild and cultivated Vitis spp., causing economic damage in the latter. We studied incidence of pheromone trap catch data, and combined this with previous work on development and diapause to construct a comprehensive model of the temporal dynamics of E. viteana. We explored the behavior of this model in six eastern United States locations along Lakes Erie and Michigan, the Finger Lakes in New York, and in Missouri and Virginia. Voltinism of E. viteana is influenced by the accumulated growing degree-days before the postsummer solstice photoperiod at which eggs develop exclusively into diapausing pupae. Our model generally predicted two full and a partial third generation in Geneva, NY, whereas partial fourth generations existed in vineyards along Lakes Erie and Michigan. In more southern latitudes, such as Missouri and Virginia, the absence of a partial fourth generation would be rare. Also, our model suggested the presence of clinal latitudinal variation in diapause induction, with southern populations of E. viteana responding to shorter daylengths than northern populations. These predictions, based on average 10-yr surface temperatures (1991–2000), are supported by past observations and explain the variability in voltinism from year to year that has been reported in the northeastern United States and Niagara Peninsula of Canada.

Diapause Maintenance and Termination in Grape Berry Moth (Lepidoptera: Tortricidae)

Abstract We studied pupal diapause maintenance and termination in Endopiza viteana, a pest of commercially grown grapes. We observed considerable variation in diapause intensity, which ranged from 5.5 to 10 mo under natural temperatures and photoperiods. Adult males tended to emerge from diapause slightly earlier than females, suggesting that E. viteana may be protandrous. In the field, low temperatures maintained diapause in overwintering pupae, and adult emergence began at ≈148 degree-days accumulated from 1 January. Photoperiod did not influence diapause termination in E. viteana. Overall, most adults emerged in spring at roughly the same time, regardless of the date at which pupae entered diapause; however, emergence was extended over a 6-wk period. Moreover, eggs oviposited by late-emerging females may experience photoperiods that would lead to diapause in pupae. Under natural conditions, extended adult emergence may result in overlapping generations; accordingly, coordinating the timing of control tactics with peak oviposition is very difficult for this insect pest.

Diapause induction in the grape berry moth (Lepidoptera : Tortricidae)

Abstract Photoperiod influences diapause induction in the grape berry moth, Endopiza viteana (=Polychrosis viteana), and eggs and neonates (<12 h) were the most sensitive to decreasing photoperiod. When held at photoperiods of 7–14 h, eggs produced mostly diapausing pupae, whereas at 15 h, development proceeded without diapause. Neonate larvae also showed sensitivity to short photoperiods, but responsiveness of larvae decreased rapidly with age, so that instars greater than 12 h old exposed to a short photoperiod of 8 h developed into adults without diapause. Eggs held at a high temperature (30°C) and 8-h photoperiod also produced diapausing pupae, suggesting that diapause induction in E. viteana is independent of temperature. Field studies showed considerable population variation in diapause induction, and an exponential saturation model predicted that 50 and 90% of individuals entered diapause at photoperiods of 14 h, 45.5 min and 14 h, 21.1 min, respectively.

What Does “Local” Firewood Buy You? Managing the Risk of Invasive Species Introduction

ABSTRACT Firewood can serve as a vector in the transport of non-native species, including wood-boring insects that feed within the wood and thus can be transported accidentally. Governments have enacted limitations on the movement of firewood in an effort to limit the anthropogenic movement of non-native species through, for example, recreational camping. Although the movement of invasive species through firewood is a documented invasion pathway, it is not trivial for governments to determine a “safe” allowable distance for moving firewood. We were motivated by this challenge and developed a theoretical simulation to determine the campgrounds that could be potentially exposed to infested firewood based upon the hypothetical distribution of an invasive species and the allowable distance for moving firewood. We extend this concept to the known distributions of emerald ash borer, Agrilus planipennis Fairmaire (Coleoptera: Buprestidae) and Asian longhorned beetle, Anoplophora glabripennis (Motschulsky) Coleoptera: Cerambycidae). We illustrate, based upon theoretical and empirical observations, that as the distribution of an invasive species increases, more rigid constraints on the movement of firewood would be required relative to those species that are distributed over a smaller scale. Also, on the level of management within a state, smaller states have far less margin for error than larger ones, as even extremely rigid restrictions on the movement of firewood could have little management effect unless the infested area is spatially limited. These results collectively suggest the potential for a dynamic management strategy that adjusts allowable distances for firewood movement based upon the distribution of the non-native species.

Assessment of potential fumigants to control Chaetodactylus krombeini (Acari: Chaetodactylidae) associated with Osmia cornifrons (Hymenoptera: Megachilidae).

ABSTRACT With the recent decline of honey bees, Apis mellifera (L.) (Hymenoptera: Apidae), there is a need for alternative or supplemental crop pollinators, such as Osmia cornifrons (Radoszkowski) (Hymenoptera: Megachilidae). However, O. cornifrons propagation could be impeded by a cleptoparasitic mite, Chaetodactylus krombeini Baker. We investigated the effects of formic acid and wintergreen oil on mortality of C. krombeini hypopi and O. cornifrons adults by determining the lethal concentration of each compound on each species. On average, >4.8 and >1.8 h were required to cause mortality in O. cornifrons adults when <2,473.5 ppm of formic acid and wintergreen oil was applied as a fumigant, respectively. When the two chemicals were directly applied to the exoskeleton of O. cornifrons adults, 353.4 ppm of wintergreen oil caused bee mortality within 10 min; however, no mortality was found with any formic acid application attempted. Mortality of C. krombeini hypopi occurred 5 and 10 min after application of >176.7 ppm of formic acid and wintergreen oil, respectively. Estimates of LC50 for C. krombeini hypopi treated with formic acid and wintergreen oil were 54.3 and 271.3 ppm, respectively. This study showed that C. krombeini could be controlled effectively without inducing O. cornifrons adult mortality based on concentration and duration of fumigation.

Field Evaluation of Effect of Temperature on Release of Disparlure from a Pheromone-Baited Trapping System used to Monitor Gypsy Moth (Lepidoptera: Lymantriidae)

ABSTRACT Traps baited with disparlure, the synthetic form of the gypsy moth, Lymantria dispar (L.) (Lepidoptera: Lymantriidae), sex pheromone are used to detect newly founded populations and estimate population density across the United States. The lures used in trapping devices are exposed to field conditions with varying climates, which can affect the rate of disparlure release. We evaluated the release rate of disparlure from delta traps baited with disparlure string dispenser from 1 to 3 yr across a broad geographic gradient, from northern Minnesota to southern North Carolina. Traps were deployed over ≈12 wk that coincided with the period of male moth flight and the deployment schedule of traps under gypsy moth management programs. We measured a uniform rate of release across all locations when considered over the accumulation of degree-days; however, due to differences in degree-day accumulation across locations, there were significant differences in release rates over time among locations. The initial lure load seemed to be sufficient regardless of climate, although rapid release of the pheromone in warmer climates could affect trap efficacy in late season. Daily rates of release in colder climates, such as Minnesota and northern Wisconsin, may not be optimal in detection efforts. This work highlights the importance of local temperatures when deploying pheromone-baited traps for monitoring a species across a large and climatically diverse landscape.

Geostatistical Analysis and the Impact of Moisture on the Spatial and Temporal Distribution of Larval Musca domestica (Diptera: Muscidae)

Abstract We studied the spatial and temporal distribution of third-instar Musca domestica L. in three high-rise poultry facilities in central Pennsylvania, and investigated its relation to manure moisture. Autocorrelograms, a geostatistical index, revealed pronounced spatial autocorrelation in M. domestica, with ranges of spatial structure from 13 to 117 m. Under normal field conditions, we observed a nonlinear functional relationship between manure moisture and larval abundance, and empirically derived an optimal manure moisture range of 74–78%. The abundance of third instars was significantly positively correlated with manure moisture at the same location in space and time for approximately half of the sampling intervals. However, moisture measurements were generally spatially random at scales ≥4 m, and thus do little to explain the spatial structure of M. domestica. Also, we rarely observed significant correlation between moisture and larval abundance over discrete temporal lags ≥7 d. However, atypical field conditions, resulting in moisture measurements that were abnormally high or low, were observed to dictate larval population dynamics over time by rendering manure habitats unfavorable for natural enemy establishment or to fly propagation, respectively.

Persistence of the Gypsy Moth Pheromone, Disparlure, in the Environment in Various Climates

Mating disruption techniques are used in pest control for many species of insects, yet little is known regarding the environmental persistence of these pheromones following their application and if persistence is affected by climatic conditions. We first studied the persistent effect of ground applications of Luretape® GM in Lymantria dispar (L) mating disruption in VA, USA in 2006. The removal of Luretape® GM indicated that the strong persistent effect of disparlure in the environment reported by previous studies is produced by residual pheromone in the dispensers as opposed to environmental contamination. In 2010 and 2011, we evaluated the efficacy of two formulations, Disrupt® II and SPLAT GMTM, in VA and WI, USA, which presented different climatic conditions. In plots treated in WI and VA, male moth catches in pheromone-baited traps were reduced in the year of treatment and one year after the pheromone applications relative to untreated controls. However, similar first- and second-year effects of pheromone treatments in VA and WI suggest that the release rate over one and two years was the same across markedly different climates. Future applications that use liquid or biodegradable formulations of synthetic pheromones could reduce the amount of persistence in the environment.