Clifford S. Sadof

Effects of Plant Architecture on the Attack Rate of Leptomastix dactylopii (Hymenoptera: Encyrtidae), a Parasitoid of the Citrus Mealybug (Homoptera: Pseudococcidae)

Abstract Attack rates of the parasitoid Leptomastix dactylopii (Howard) were examined in petri dishes and on caged plants that varied in architectural characteristics. Individual female parasitoids were placed into petri dishes containing a range of densities of the citrus mealybug, Planococcus citri (Risso). Green and yellow-variegated coleus, Solenostemon scutellarioides (L.) Codd, were used to determine the effects of plant architecture on the rate at which L. dactylopii parasitized citrus mealybugs. Coleus plants were categorized into size classes based on height, number of leaves, leaf surface area, and number of branches. A single mated female L. dactylopii was placed into each plastic observation cage containing a plant with 1, 8, or 16 third- to early fourth-instar mealybugs and allowed to forage for 24 h. After this time, citrus mealybugs were removed from coleus plants and placed into petri dishes that were checked after 10 d for mummified citrus mealybugs, the measure of a successful attack. L. dactylopii were unable to find a host after 24 h when only one citrus mealybug was present in the searching environment. Higher attack rates occurred as the number of mealybugs increased in the petri dishes. L. dactylopii attacked an average of 15.6 ± 2.3 mealybugs within a 24-h period. Higher attack rates were evident as the number of citrus mealybugs increased on caged plants. Plant color had no effect on the attack rate of L. dactylopii. All architectural characterizations of plant size, height, leaf number, leaf surface area, and branch number were negatively correlated with parasitoid attack rate. These findings suggest that biological control practitioners may use any convenient measure of plant size (e.g., height) to modify the release rate of L. dactylopii in a citrus mealybug management program.

Reducing Insecticide Volume and Nontarget Effects of Ambrosia Beetle Management in Nurseries

ABSTRACT Ambrosia beetles (Coleoptera: Curculionidae: Scolytinae) are increasingly important pests of nursery-grown trees because of the arrival of several invasive species. Ambrosia beetles bore into young trees and inoculate them with ambrosia fungus, which interferes with vascular transport resulting in limb or tree death. In spring, when beetles are active, growers make frequent applications of pyrethroid insecticides to susceptible tree species to deter beetles from boring into trees. Applications often are made with airblast sprayers that forcefully release insecticide mist that billows through nursery beds. Our objective was to compare the environmental, nontarget, and economic effects of airblast sprayer applications to applications made with a new dual-nozzle spray wand that makes targeted applications only to tree trunks where beetles attack. Through replicated experiments at commercial nurseries, we found that 5 times more insecticide was released by airblast sprayers than the manual spray wand. The extra insecticide from airblast applications landed on tree canopies, between rows, and left the nursery beds as drift. As a consequence of not spraying tree canopies, 50% more natural enemies and 50% fewer spider mites were captured in nursery beds treated with the manual spray wand than beds treated with the airblast sprayer. Manual applications require 12 times more labor than airblast applications. However, increased need for expensive miticide applications may make manual applications an economically feasible strategy for integrated pest management (IPM) of ambrosia beetles in nurseries.

Polyphagy, flightlessness, and reproductive output of females: a case study with bagworms (Lepidoptera: Psychidae)

Abstract 1. We evaluated the relation between plant‐mediated larval traits and the fitness of female bagworms, Thyridopteryx ephemeraeformis Haworth (Lepidoptera: Psychidae) by sampling 29 populations of bagworms on five plant genera (Thuja, Pinus, Picea, Juniperus, and Gleditsia).

Potential of Suction Traps As a Monitoring Tool for Aphis glycines (Hemiptera: Aphididae) in Soybean Fields

ABSTRACT The current study evaluated the potential of using counts of winged adults captured in suction traps to forecast the local abundance of soybean aphid, Aphis glycines Matsumura (Hemiptera: Aphididae), in soybean, Glycine max (L.) Merr., fields. The abundance of aphids was evaluated weekly by sampling plants in four to 11 soybean fields and recording the number of aphids in suction traps between 2006 and 2008 in four counties in Indiana and Illinois. Fields in each county were located within 10 km of their respective suction trap, which allowed us to evaluate the relation between aphid abundance on soybean plants and in suction traps at the county level. Migrant soybean aphids caught in suction traps exhibited distinct seasonal trends each year: in 2006, trapped migrants consisted predominantly of individuals dispersing from soybean to buckthorn (Rhamnus sp.); in 2007, in contrast, the majority of trapped migrants were apparently individuals dispersing among soybean fields. The cumulative number of aphids captured in suction traps was positively related to aphid densities on soybean plants. However, the utility of suction traps as a monitoring tool may be limited by the variation in temporal patterns observed in suction traps and on soybean plants each year, and the spatial variation in aphid abundance among soybean fields within a county.

Ground Beetle (Coleoptera: Carabidae) Phenology, Diversity, and Response to Weed Cover in a Turfgrass Ecosystem

ABSTRACT Despite being fragmented and highly disturbed habitats, urban turfgrass ecosystems harbor a surprising diversity of arthropods. The suitability of turf as arthropod habitat, however, likely depends on the extent and types of pesticides and fertilizers used. For example, moderate levels of weed cover in low-input lawns may provide alternative food resources. We conducted a 2-yr field study to: 1) characterize the ground beetle (Carabidae) species assemblage in turfgrass, and 2) assess the direct and indirect effects of lawn management on carabid communities. Weed cover and beetle activity were compared among four lawn management programs: 1) consumer/garden center, 2) integrated pest management (IPM), 3) natural organic, and 4) no-input control. Nearly 5,000 carabid beetles across 17 species were collected with the predator Cyclotrachelus sodalis LeConte numerically dominating the trap catch (87% and 45% of individuals in 2005 and 2006, respectively). Populations of C. sodalis underwent a distinct peak in activity during the third week of June, whereas omnivorous and granivorous species tended to occur at far lower levels and were less variable over the season. We found no evidence for direct effects of lawn management on carabid species diversity; however, we detected an indirect effect mediated by variation in weed cover. Seed-feeding species were positively correlated with turf weeds early in 2006, whereas strictly predaceous species were not. Thus, turf management programs that lead to changes in plant species composition (i.e., herbicide regimes) may indirectly shape epigeal arthropod communities more strongly than the direct effects of insecticide use.

Control of bagworms (Lepidoptera: Psychidae) using contact and soil-applied systemic insecticides.

ABSTRACT The current study evaluated the effect of different classes of insecticides against bagworms (Lepidoptera: Psychidae) on arborvitae by using a laboratory bioassay that allowed us to simultaneously evaluate the feeding rate, growth, and mortality of larvae. Soil application of the systemic insecticides dinotefuran and (to a lesser extent) chlothianidin increased larval mortality and reduced the feeding rate and growth of larvae, up to 50 d posttreatment. The effectiveness of systemic insecticides against bagworms makes them well suited to control bagworms on tall trees heavily infested in the upper canopy. Chlorantranilipole and indoxacarb were as effective in controlling bagworms as other contact insecticides commercially available (spinosad and bifenthrin). Chlorantraniliprole had a residual effect 10 d posttreatment and may therefore provide an effective tool to protect the foliage of arborvitae against bagworms over a sustained period.

Effect of Variegation on Stem Exudates of Coleus and Life History Characteristics of Citrus Mealybug (Hemiptera: Pseudococcidae)

Abstract Both defensive and nutritional hypotheses have been used to explain the improved performance of sucking insects on variegated plants. With portions of leaves unable to photosynthesize, variegated plants are likely to have less carbon assimilate to allocate to the production of defensive compounds than green plants. Alternatively, like plants grown in the shade, improved response of sucking insects on variegated plants may be caused by greater mobility of amino acid nitrogen and carbohydrates in the phloem to fuel compensatory production of leaves. We examined amino acid and sucrose content of stem exudate collected from red-variegated, yellow-variegated, and green-leafed coleus plants, Solenostemon scutellarioides (L.) Codd, and their relation to life history characteristics of citrus mealybug, Planococcus citri (Risso), to test these defensive and nutritional hypotheses. Although higher concentrations of both total amino acids and sucrose were found in green- and red-leaved plants, these quantitative measures were uncorrelated with life history parameters of mealybugs. In contrast, our analysis of qualitative measures of amino acid composition supported both defensive and nutritional hypotheses. Green-leafed plants had the greatest levels of shikimic acid precursors and lowest levels of other nonessential amino acids. Life history characteristics of citrus mealybugs were correlated negatively with increasing proportions of shikimic acid precursors and positively with increasing proportions of other nonessential amino acids. Thus, our studies of life history and stem chemistry indicate that improved suitability of variegated plants is consistent with both carbon- and nutrient-based theories of plant defense.

Growth of Larval Agrilus planipennis (Coleoptera: Buprestidae) and Fitness of Tetrastichus planipennisi (Hymenoptera: Eulophidae) in Blue Ash (Fraxinus quadrangulata) and Green Ash (F. pennsylvanica).

ABSTRACT Emerald ash borer (Agrilus planipennis Fairmaire) is an invasive primary pest of North American ash (Fraxinus spp.) trees. Blue ash (F. quadrangulata) is less susceptible to emerald ash borer infestations in the forest than other species of North American ash. Whereas other studies have examined adult host preferences, we compared the capacity of emerald ash borer larvae reared from emerald ash borer eggs in the field and in the laboratory to survive and grow in blue ash and the more susceptible green ash (F. pennsylvanica). Emerald ash borer larval survivorship was the same on both ash species. Mortality due to wound periderm formation was only observed in living field grown trees, but was low (<4%) in both green and blue ash. No difference in larval mortality in the absence of natural enemies suggests that both green and blue ash can support the development of emerald ash borer. Larvae reared from eggs on blue ash were smaller than on green ash growing in the field and also in bolts that were infested under laboratory conditions. In a laboratory study, parasitism rates of confined Tetrastichus planipennisi were similar on emerald ash borer larvae reared in blue and green ash bolts, as were fitness measures of the parasitoid including brood size, sex ratio, and adult female size. Thus, we postulate that emerald ash borer larvae infesting blue ash could support populations of T. planipennisi and serve as a potential reservoir for this introduced natural enemy after most of the other native ash trees have been killed.

Distribution and Dynamics of Japanese Beetles Along the Indianapolis Airport Perimeter and the Influence of Land Use on Trap Catch

Abstract As part of a program to minimize the accidental transportation of Japanese beetles (Popillia japonica) through cargo aircraft to areas where they are not established, a 4-yr trapping project was initiated to study the relative distribution and dynamics of the beetles along a trap line around the Indianapolis International Airport. Land use influence on beetle abundance (trap catch) was assessed using a geographic information system. Trap catch was consistently high in some locations and low in others. In general, high trap catches occurred near agronomic land planted with corn or soybeans, which are both preferred hosts of adult beetles. Low trap catches generally occurred in areas lacking preferred host plants. The amount of agronomic land within 500 m of the traps was always positively correlated with trap catch. Average trap catches were highly correlated by location from year to year, indicating stability of the relative distribution of the beetles along the trap line. Because high trap catches consistently occurred in the same locations, it can be inferred that trapping can be an effective method to monitor Japanese beetle populations. Taking airport-owned agronomic land out of corn and soybean production near the cargo terminals may reduce beetle activity in these areas.

Ground Beetle (Coleoptera: Carabidae) Assemblages in Mulched and Non-Mulched Garden Plots

Abstract Ground beetles (Coleoptera: Carabidae) are important generalist predators in a variety of habitats, where they prey on many kinds of pest insects. We used pitfall traps for weekly collections by Master Gardener volunteer researchers for 13 weeks in 1998 and 12 weeks in 1999 to assess species composition and temporal patterns of ground beetles in plots of potatoes in home gardens in Illinois and Indiana. Potato plots were either mulched with straw or were left unmulched, having bare soil between plant rows. A total of 82 individuals of 9 species was found in 1998 in mulched plots, versus 79 individuals of 10 species found in unmulched plots. In 1999, 639 individuals of 23 species were collected in mulched plots, versus 380 individuals of 31 species in unmulched plots. Significantly more Cyclotrachelus sodalis (LeConte) were found in mulched plots than in unmulched plots in 1999, whereas there were no significant differences between mulched and unmulched plots in numbers of Cyclotrachelus convivus (LeConte), Harpalus pensylvanicus DeGeer, Pterostichus permundus (Say) or Scarites subterraneus F. Species diversity, as measured by the Shannon Diversity Index, was significantly greater in unmulched plots than in mulched plots in 1999. Fourteen species collected in unmulched plots in 1999 were not found in mulched plots, whereas 6 species found in mulched plots were not found in unmulched plots. Although ground beetle assemblages differed as a function of habitat manipulation, exact diets of carabids need to be understood to know the potential to impact pest management in home gardens.