Richard A. Casagrande

Monarch Butterfly Oviposition on Swallow-Worts (Vincetoxicum spp.)

Abstract As black swallow-wort, Vincetoxicum nigrum L. Moench, and pale swallow-wort, V. rossicum (Kleopow) Barbar., spread throughout the northeastern United States and southern Canada, there is concern about the impact of these invasive plants on populations of the native North American monarch butterfly Danaus plexippus L. Recent laboratory studies in New York and Ontario, Canada, have found little or no oviposition by monarch butterflies on the two Vincetoxicum species. In Rhode Island, we found 10.5–21.7% oviposition on Vincetoxicum species relative to common milkweed Asclepias syriaca L. in choice tests and 11.9–20.3% in no-choice tests in 2 yr of laboratory testing. These results were supported by field cage trials where monarchs given a choice between V. nigrum and A. syriaca laid 24.5% of their eggs on V. nigrum. In surveys of three pasture fields in Rhode Island where relative coverage of A. syriaca exceeded that of V. nigrum by a 0.77:0.23 ratio, 15.4% of monarch eggs were found on V. nigrum plants. In V. nigrum stands with very little A. syriaca (6.25 stems/ha), monarch egg density on V. nigrum was found to be over five times greater than in the three mixed pasture fields. In none of our laboratory or field evaluations was there any survival of monarch larvae on Vincetoxicum species. It seems that in Rhode Island, Vincetoxicum species serve as an oviposition sink for monarch butterflies. These findings suggest that East Coast butterflies may differ in host selection from those in central New York and southern Ontario, Canada.

Effect of trap size, placement, and age on captures of blueberry maggot flies (Diptera: Tephritidae).

Abstract Ammonium acetate and protein hydrolysate baited and unbaited green spheres (3.6, 9.0, and 15.6 cm diameter) were evaluated for effectiveness in capturing blueberry maggot flies, Rhagoletis mendax Curran. Early in the season, baited spheres (9.0 cm diameter) captured significantly more R. mendax flies than spheres of 3.6 and 15.6 cm diameter. As the season progressed, the differences in trap captures became less pronounced among the 3.6-, 9.0-, and 15.6-cm-diameter spheres. In other experiments, the effects of trap positions and age on captures of blueberry maggot flies were assessed. Traps were positioned 15 cm above the bush canopy, 15 cm inside the canopy (from top of the bush), and 45 cm from the ground. Traps placed within the canopy captured 2.5 and 1.5 times as many flies compared with traps placed above the canopy and 45 cm from the ground, respectively. When sticky yellow Pherocon AM boards and green sphere traps were allowed to age in field cages, freshly baited (0 d) yellow sticky boards captured significantly more blueberry maggot flies than boards aged for 11, 28, and 40 d, respectively. No significant differences were observed among boards aged for 11, 28, and 40 d. However, when baited 9-cm sticky spheres were aged in field cages, there were no significant differences between freshly baited spheres and spheres aged for 11 and 28 d, respectively. Spheres aged for 40 d differed significantly from freshly baited ones. The study demonstrated that the baited 9-cm-diameter sphere was more effective in capturing blueberry maggot flies than spheres of 3.6 and 15.6 cm diameter. When this trap is deployed in the center of the bush canopy ≈15 cm from the top of the bush, it is attractive and accessible to R. mendax flies. The data also indicated that a baited 9-cm sphere has a longer effective life span than Pherocon AM boards when deployed under the same field conditions.

Susceptibility of Native and Non-Native Common Reed to the Non-Native Mealy Plum Aphid (Homoptera: Aphididae) in North America

Abstract An aggressive, non-native haplotype (distinct genetic lineage within a species) of Phragmites australis is invading brackish and freshwater systems in the eastern United States, potentially displacing native haplotypes. We studied the differential susceptibility of native and non-native populations collected from sites throughout North America to the non-native aphid, Hyalopterus pruni. In a greenhouse study, we found significantly higher aphid populations on native haplotypes than on the non-native haplotype 2 mo after infestation. Aphid feeding caused chlorosis and death of native stems, and in some cases, killed whole native genets. The non-native plants remained relatively undamaged. In a field study, non-native plants had significantly lower aphid densities than native plants or remained aphid free. There was an interactive effect in which aphid populations increased on the native plants over the 1-mo study period but remained low on non-native plants over the same period. The susceptibility of native North American populations of P. australis to non-native aphid infestation may indirectly affect the ability of these native plants to compete with non-native plant populations, ultimately contributing to the decline of native haplotypes.

Distribution of native and exotic Phragmites australis in Rhode Island.

Abstract Exotic populations of Phragmites australis (common reed) are now present in southern New England wetland habitats where native populations were once abundant. We surveyed Rhode Island to determine the distribution of native and exotic P. australis, and used this information to build a publicly accessible Geographic Information System (GIS) database. All P. australis populations sampled on the mainland were exotic. We only found native populations growing throughout a network of tidal marshes and ponds on Block Island, and several of these populations are being overrun by expanding exotic populations. The GIS database from this survey can be expanded to other regions, and can be used for the conservation of the native subspecies and for ensuring that control efforts target only exotic populations.

Distribution and new host records of a race of Chrysomelobia labidomerae Eickwort (Acari: Tarsonemina; podapolipidae) attacking the Colorado potato beetle in Mexico

ABSTRACT Distribution and host data are given for a race of Chrysomelobia labidomerae Eickwort, an ectoparasite of the Colorado potato beetle, Leptinotarsa decemlineata (Say), and some closely related species.

Host Specificity of Hypena opulenta: A Potential Biological Control Agent of Vincetoxicum in North America

ABSTRACT A biological control program has been initiated against the European swallow-worts Vincetoxicum nigrum (L.) Moench and V. rossicum (Kleopow) Barbar. (Family Apocynaceae) that have become invasive in North America. The leaf-feeding moth, Hypena opulenta Christoph (Lepidoptera: Erebidae), originating from eastern Europe, has been under measurement as a potential biological control agent of swallow-worts since 2006. In this study we measured the host range of H. opulenta by screening 82 potential host plant species for larval development under no-choice conditions. In addition, we also monitored female fecundity, longevity, and oviposition preference among suitable larval hosts. Successful larval development occurs only on Vincetoxicum spp. Partial larval development by one larva was observed on Boehmeria cyclindrica (L.) Sw. (Urticaceae) to the final instar, but this individual failed to pupate. Exploratory feeding occurred on Gonolobus stephanotrichus Griseb. (Apocynaceae) and Urtica dioica L. (Urticaceae), but all larvae failed to develop past the first and second instar, respectively. Additional testing with mature larvae on a subset of the plant species demonstrates that no species outside the genus Vincetoxicum are suitable for complete larval development of H. opulenta. The longevity and fecundity of females raised on each target weed are similar and gravid females do not display an oviposition preference among Vincetoxicum spp. Hypena opulenta does not present a risk to any native plant species or species of economic importance in North America. Petitions have been submitted for experimental open-field releases of H. opulenta in the United States and Canada.

Performance of potential European biological control agents of Vincetoxicum spp. with notes on their distribution.

Exploratory surveys were conducted in Europe to locate potential biological control agents of Vincetoxicum nigrum and Vincetoxicum rossicum and to collect known specialist herbivores of Vincetoxicum hirundinaria (Abrostola asclepiadis, Chrysolina a. asclepiadis, Eumolpus asclepiadeus and Euphranta connexa). Development of the most abundant herbivores found attacking leaves, roots, and developing seeds was evaluated in the laboratory on three Vincetoxicum spp. Field surveys revealed that the highest diversity of herbivores was associated with the abundant and widespread V. hirundinaria. No new herbivores were reported from V. hirundinaria or V. nigrum, but the leaf‐feeding noctuid Hypena opulenta was recorded for the first time attacking V. rossicum and V. scandens in Ukraine. Based upon larval survival and development and adult fecundity, the leaf feeders A. asclepiadis, C. a. asclepiadis, and H. opulenta, perform better on V. nigrum and V. rossicum than on V. hirundinaria. Larval performance of the root feeder E. asclepiadeus followed a similar pattern, but adult fecundity of this insect did not vary among host plant species. Immature development time of the pre‐dispersal seed feeder E. connexa is similar among hosts, but larvae grow larger on V. nigrum and V. hirundinaria than on V. rossicum. All herbivores are promising biological control agents of Vincetoxicum in North America and we have prioritized host range testing with H. opulenta and E. asclepiadeus.

INTRASPECIFIC VARIATION IN TSUGA CANADENSIS FOLIAR CHEMISTRY

Abstract Three groups of Tsuga canadensis (Eastern Hemlock) trees were analyzed to compare their chemical composition and the potential for naturally occurring resistance to Adelges tsugae (Hemlock Woolly Adelgid [HWA]). Potentially resistant “parent” trees located in southern Connecticut were compared with rooted propagules from those same trees and control trees located in northern Vermont, outside of the current HWA range. For trees in each group, we quantified Ca, P, K, C, and N and developed terpenoid profiles using solid-phase microextraction (SPME) and gas chromatography-mass spectrometry (GC/MS). There was no significant variation in terpenoid profiles between the three groups of hemlock trees. Propagules retained elevated levels of Ca and N from fertilization during propagation, suggesting that their chemical composition does not mirror the parent trees. The potentially resistant “parent” trees had higher levels of K compared to control trees. This may impart some level of tolerance/resistance to HWA and explain their persistence in hemlock forests that have otherwise been decimated by HWA. Comparison to regional foliar chemistry databases suggest that while rare, such elevated K levels do exist in natural hemlock populations. Such individuals may persist as HWA continues to spread across the region.

Host specificity tests of Chrysomelobia labidomerae, a mite parasitic on the Colorado potato beetle

Abstract The parasitic mite, Chrysomelobia labidomerae Eickwort, appears to be limited to coleopterous hosts in the tribe Zygogrammini of the subfamily Chrysomelinae. The mite was originally described as a parasite of adult Labidomera clivicollis (Kirby) in New York. We found it in Mexico parasitizing 4 additional species in the tribe Zygogrammini: Leptinotarsa decemlineata (Say), Leptinotarsa undecemlineata Stahl., Leptinotarsa signaticollis Stahl., and Leptinotarsa cacica Stahl. Experimentally, we found many species to be unsuitable hosts for a Mexican race of the mite including the honey bee, Apis mellifera (L.); coccinellids: Hippodamia convergens Guerin-Meneville, Coleomegilla maculata (DeGeer), Coccinella septempunctata L., and the Mexican bean beetle, Epilachna varivestis Mulsant; carabids: Harpalus pennsylvanicus DeGeer, and Clivinia impressifrons LeConte; the cerambycid, Tetraopes tetrophthalmus (Forster); and the chrysomelid, Lema trilineata L. Larvae of L. decemlineata were also found to be uns...

Distribution of Cotesia rubecula (Hymenoptera: Braconidae) and Its Displacement of Cotesia glomerata in Eastern North America

ABSTRACT A survey was conducted from May to Oct of 2011 of the parasitoid community of the imported cabbageworm, Pieris rapae (Lepidoptera: Pieridae), in cole crops in part of the eastern United States and southeastern Canada. The findings of our survey indicate that Cotesia rubecula (Hymenoptera: Braconidae) now occurs as far west as North Dakota and has become the dominant parasitoid of P. rapae in the northeastern and north central United States and adjacent parts of southeastern Canada, where it has displaced the previously common parasitoid Cotesia glomerata (Hymenoptera: Braconidae). Cotesia glomerata remains the dominant parasitoid in the mid-Atlantic states, from Virginia to North Carolina and westward to southern Illinois, below latitude N 38° 48′. This pattern suggests that the released populations of C. rubecula presently have a lower latitudinal limit south of which they are not adapted.