Yong-Lak Park

Temperature-Dependent Emergence of Osmia cornifrons (Hymenoptera: Megachilidae) Adults

ABSTRACT Japanese hornfaced bees Osmia cornifrons (Radoszkowski) (Hymenoptera: Megachilidae) are used for pollination of spring blooming fruit crops such as apple, pear, and blueberry. Because O. cornifrons has a short adult life span, synchronization of bee emergence with bloom is critical to maximize crop pollination. This study was conducted to determine lower temperature thresholds (LTDs), optimum temperatures, and required degree-day accumulation for emergence of O. cornifrons adults. Patterns of temperature-dependent emergence of O. cornifrons adults at seven temperatures (3.9, 12.0, 18.6, 26.6, 30.3, 35.6, and 42.5°C) were modeled and simulated with linear and nonlinear regression analyses. Results of this study showed that required degree-days (DD) for emergence of male and female O. cornifrons adults were 125.2 DD, with LTD of 8.9°C and 179.8 DD, with LTD of 8.6°C, respectively. The optimum temperatures for emergence were 36.5, 30.2, and 35.7°C for male, female, and both sexes combined, respectively. This study indicated that emergence of O. cornifrons adults could be manipulated to synchronize with pollination periods of target fruit crops.

Theory, Technology, and Practice of Site-Specific Insect Pest Management

Abstract Insects are usually unevenly distributed throughout an area in nature. Despite this knowledge, analytical methods and technology have limited insect pest management to uniform management decisions in the field. Recently, the methods and technology to map and analyze insect spatial distribution have been developed to a level where the uneven nature of insect populations can be considered for application of pest management tactics. This new approach to insect management is termed site-specific pest management. Site-specific pest management utilizes spatial information about pest distribution to apply control tactics only where pest density is economically high within a field. This review will detail the current status of site-specific insect pest management in agriculture, technological requirements, its limitations, and future potential.

Attraction of the invasive Halyomorpha halys in its native Asian range to traps baited with semiochemical stimuli

The brown marmorated stink bug, Halyomorpha halys, is considered a serious invasive species capable of causing significant agricultural and nuisance problems. Researchers in the USA recently identified the two-component H. halys aggregation pheromone from populations in North America and found that when it is combined with the pheromone synergist methyl decatrienoate (MDT), it resulted in reliable, season-long captures of H. halys throughout the USA. However, no study has assessed whether H. halys populations in the native range are attracted to and can also be reliably captured by the combination of these stimuli. In this study, our goal was to evaluate the response of H. halys adults, nymphs, and non-target organisms to traps baited with the aggregation pheromone, MDT alone, or in combination at three locations in the native range. Traps baited with combined stimuli reliably captured the greatest numbers of H. halys adults and nymphs, and traps baited with either lure treatment caught a unique community of non-target organisms. In addition, Plautia stali was cross-attracted to the H. halys aggregation pheromone. Overall, we demonstrate that the pheromone-based tools developed in the USA may be used for worldwide detection and surveillance programs for H. halys and P. stali.

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.

Nesting Activity and Behavior of Osmia cornifrons (Hymenoptera: Megachilidae) Elucidated Using Videography

Osmia cornifrons Radoszkowski (Hymenoptera: Megachilidae) is utilized as an alternate pollinator to Apis mellifera L. (Hymenoptera: Apidae) in early-season fruit crops. This study was conducted to investigate nesting activities and associated behaviors of O. cornifrons. Osmia cornifrons nesting activity was recorded by using a digital video recorder with infrared cameras. Nesting behavior of ten female O. cornifrons was observed, and the number of nesting trips per hour was recorded. Trends in daily activity were determined with regression analysis, and chi square analysis was used to determine if O. cornifrons spent a greater amount of time performing certain activities. The percentage of time required to gather nesting resources and complete nest construction activities was recorded from the video footage. Results of this study showed that pollen gathering was the most time-consuming gathering activity, requiring  min per cell and cell provisioning was the most time-consuming intranest activity, requiring 28.9 min ± 3.97 min. We also found that O. cornifrons activity was correlated with time of day, temperature, and precipitation. Various nesting behaviors, including cell provisioning and partitioning, oviposition, grooming, resting and sleeping, nest-searching, and repairing behaviors, are described in this paper.

Intraplant Sampling of Grapevines for Pierce's Disease Diagnosis

The bacterium Xylella fastidiosa Wells et al. induces Pierces disease (PD) of grapevine. This study was initiated to improve sampling protocols to identify X. fastidiosa-infected grapevines (Vitis vinifera L.) in California vineyards. Several potential PD symptoms, including leaf necrosis and chlorosis, internodal distance, petiole length and weight, and extent of cane branching, were not reliable indicators of X. fastidiosa infection. The matchstick symptom (i.e., abscised leaf blades leaving behind a dried, burnt-appearing petiole tip) was the only consistent indicator of infection in X. fastidiosa-positive grapevines. Further study revealed that leaves selected from the most basal nodes of positive canes had the highest probability of X. fastidiosa detection, with enzyme-linked immunosorbent assay. A symptom reliability index (SRI) was created to assess visual PD diagnosis by node location. The SRI values were the highest at basal node locations, but symptoms at any single node were not consistently reliable for PD diagnosis. Our results showed that PD diagnosis based on foliar symptoms was unreliable. However, taking samples from the basal portion of a cane increased the probability of X. fastidiosa detection.

Spatial Distribution of Pierce’s Disease Related to Incidence, Vineyard Characteristics, and Surrounding Land Uses

A four-year (2001 to 2004) census was conducted in 220 vineyard blocks in the San Joaquin Valley (Kern County, CA) to characterize the spatial distribution patterns of Pierce’s disease (PD) of grapevine caused by Xylella fastidiosa. Geostatistics and spatial analysis with distance indices were used to investigate relationships of PD incidence (i.e., percentage of vines with PD) and occurrence (i.e., presence or absence of PD) with vineyard characteristics and the surrounding environment using a geographic information system. The census confirmed 52 vineyard blocks with at least one X. fastidiosa-infected grapevine and PD incidence in those vineyard blocks ranged from 0.001 to 29.8%. A total of 36 of the 52 blocks had fewer than five infected vines, so spatial analysis was not valid for these blocks. For the remaining 16 blocks, the distribution of X. fastidiosa-infected vines could be categorized as no structure, random, spatial trend, and aggregation as the incidence increased. Eleven blocks showed PD distributions that were consistent with primary X. fastidiosa spread, while two blocks showed aggregations that suggested secondary or vine-to-vine spread. The distribution in one block indicated a mixture of primary and secondary spread. Two blocks had recurring aggregations of X. fastidiosa-infected vines within rows that could be the result of vector feeding on adjacent plants within rows or bacterial spread on pruning implements. Significantly higher PD occurrence was found in Flame Seedless vineyard blocks, and other vineyard characteristics such as vineyard age, pruning method, and planting density were not related to PD occurrence. Although PD occurrence was not spatially related with surrounding environment, PD incidence was spatially related to citrus. This study provides spatial information concerning the epidemiology and sampling of PD in vineyards.

Spatial Distributions of Corn Rootworm (Coleoptera: Chrysomelidae) Eggs and Larvae: Implications for Sampling

Abstract Experiments were conducted to determine distance between sample points to obtain independent samples of corn rootworm eggs and larvae. Spatial patterns and spatial dependence of egg and larval distributions were investigated using geostatistics at two different spatial scales: field scale with sampling distance of 20–25 m and plot scale with 0.2-m sampling distance. Field-scale egg distribution showed no spatial dependence, indicating a random distribution. In the plot-scale study, egg distributions of two plots were random but one plot exhibited spatial dependence that explained 89% of the spatial variability. Larval distribution showed spatial dependence at both field and plot scales and 49.7–99.7% of spatial variability was explained by spatial dependence. This study reported that the distance to obtain independent samples of egg densities would be >25 m for field-scale egg sampling and >0.4 m for plot-scale egg sampling. Independent larval estimates would be produced by spacing samples >46 m apart for field-scale larval sampling, and >1.0 m apart for plot-scale larval sampling.

Effect of Bunch Sanitation on Spatial Distributions of Abscised Fruit and Phycitine Moths (Lepidoptera: Pyralidae) in California Date Gardens

Abstract Phycitine moths are an economic impediment to California date, Phoenix dactylifera L., production. Summer populations build to damaging levels on abscised dates that get trapped in fruit bunches. This study was conducted to determine the relationship between abscised fruit and moth infestation, and to evaluate changes in the spatial distribution of abscised fruit and moth-infested fruit after a bunch-sanitation treatment. Over the 9 wk of this study, there was a 69.9% reduction in the number of moth-infested fruit after a single sanitation treatment. Linear regression analysis showed a significant relationship between abscised fruit and phycitine moth-infested fruit; 42 and 76.6% of the variation in the number of infested fruit was explained by the number of abscised fruit in noncleaned and cleaned plots, respectively. The pattern of reinfestation by moths over the 9 wk posttreatment period was analyzed with spatial analysis with distance indices. Significant spatial associations were found between abscised fruit and moth-infested fruit, supporting the regression analysis. The sanitation treatments caused significant gaps in both abscised fruit and moth-infested fruit. Over time, gap sizes became smaller, indicating a nonrandom pattern of reinfestation that likely was caused by the movement of moths from nontreated areas into treated areas. This study, the first spatial analysis conducted in dates, suggests that in-season bunch sanitation could be effective at reducing summer moth densities if applied on a large regional scale.

Effects of Temperature on Development and Voltinism of Chaetodactylus krombeini (Acari: Chaetodactylidae): Implications for Climate Change Impacts

Temperature plays an important role in the growth and development of arthropods, and thus the current trend of climate change will alter their biology and species distribution. We used Chaetodactylus krombeini (Acari: Chaetodactylidae), a cleptoparasitic mite associated with Osmia bees (Hymenoptera: Megachilidae), as a model organism to investigate how temperature affects the development and voltinism of C. krombeini in the eastern United States. The effects of temperature on the stage-specific development of C. krombeini were determined at seven constant temperatures (16.1, 20.2, 24.1, 27.5, 30.0, 32.4 and 37.8°C). Parameters for stage-specific development, such as threshold temperatures and thermal constant, were determined by using empirical models. Results of this study showed that C. krombeini eggs developed successfully to adult at all temperatures tested except 37.8°C. The nonlinear and linear empirical models were applied to describe quantitatively the relationship between temperature and development of each C. krombeini stage. The nonlinear Lactin model estimated optimal temperatures as 31.4, 32.9, 32.6 and 32.5°C for egg, larva, nymph, and egg to adult, respectively. In the linear model, the lower threshold temperatures were estimated to be 9.9, 14.7, 13.0 and 12.4°C for egg, larva, nymph, and egg to adult, respectively. The thermal constant for each stage completion were 61.5, 28.1, 64.8 and 171.1 degree days for egg, larva, nymph, and egg to adult, respectively. Under the future climate scenarios, the number of generations (i.e., voltinism) would increase more likely by 1.5 to 2.0 times by the year of 2100 according to simulation. The findings herein firstly provided comprehensive data on thermal development of C. krombeini and implications for the management of C. krombeini populations under global warming were discussed. *Scientific Article No. 3278 of the West Virginia Agricultural and Forestry Experiment Station, Morgantown, West Virginia