Scott Horn

The Biology and Preliminary Host Range of Megacopta cribraria (Heteroptera: Plataspidae) and Its Impact on Kudzu Growth

ABSTRACT The bean plataspid, Megacopta cribraria (F.), recently was discovered in the United States feeding on kudzu, Pueraria montana Lour. (Merr.) variety lobata (Willd.), an economically important invasive vine. We studied its biology on kudzu and its impact on kudzu growth. We also tested its ability to use other common forest legumes for oviposition and development. Flight intercept traps operated from 17 May 2010 to 31 May 2011 in a kudzu field near Athens, GA showed three peaks of adult flight activity suggesting there are two generations per year on kudzu. Vine samples examined for eggs from April 2010 to April 2011 and June to October 2011 showed two periods of oviposition activity in 2010, which coincided with the peaks in adult activity. In 2011, the second period of oviposition began on or before 24 June and then egg abundance declined gradually thereafter until late August when we recovered <2 eggs/0.5 m of vine. Samples of the five nymphal instars and adults on vines did not show similar trends in abundance. Adults did not lay eggs on the various legume species tested in 2010 in a no-choice test possibly because the cages were too small. In the 2011 field host range experiments conducted in a kudzu field by using 12 legume species, M. cribraria preferentially oviposited on kudzu over soybean, Glycine max Merrill, but they still laid 320 eggs per plant on soybean. Lespedeza hirta (L.) Hornem. and Lespedeza cuneata (Dum. Cours.) G. Don had 122.2 and 108.4 eggs per plant, respectively. Kudzu and soybean were the only species M. cribraria completed development on. Plots protected from M. cribraria feeding by biweekly insecticide applications had 32.8% more kudzu biomass than unprotected plots. Our results show that M. cribraria has a significant impact on kudzu growth and could help suppress this pest weed.

Chinese Privet (Ligustrum sinense) Removal and its Effect on Native Plant Communities of Riparian Forests

Abstract Chinese privet is a major invasive shrub within riparian zones throughout the southeastern United States. We removed privet shrubs from four riparian forests in October 2005 with a Gyrotrac® mulching machine or by hand-felling with chainsaws and machetes to determine how well these treatments controlled privet and how they affected plant community recovery. One year after shrub removal a foliar application of 2% glyphosate was applied to privet remaining in the herbaceous layer. Three “desired-future-condition” plots were also measured to assess how well treatments shifted plant communities toward a desirable outcome. Both methods completely removed privet from the shrub layer without reducing nonprivet shrub cover and diversity below levels on the untreated control plots. Nonprivet plant cover on the mulched plots was > 60% by 2007, similar to the desired-future-condition plots and higher than the hand-felling plots. Both treatments resulted in higher nonprivet plant cover than the untreated controls. Ordination showed that after 2 yr privet removal plots were tightly grouped, suggesting that the two removal techniques resulted in the same plant communities, which were distinctly different from both the untreated controls and the desired-future-condition. Both treatments created open streamside forests usable for recreation and other human activities. However, much longer periods of time or active management of the understory plant communities, or both, will be required to change the forests to typical mature forest plant communities. Nomenclature: Glyphosate; Chinese privet, Ligustrum sinense Lour.

Removing an invasive shrub (Chinese privet) increases native bee diversity and abundance in riparian forests of the southeastern United States

Abstract.  1. Chinese privet (Ligustrum sinense Lour.) was removed from riparian forests in the Piedmont of Georgia in November 2005 by mulching with a track‐mounted mulching machine or by chainsaw felling. The remaining privet in the herbaceous layer was killed with herbicide in December 2006.

Effect of Trap Type, Trap Position, Time of Year, and Beetle Density on Captures of the Redbay Ambrosia Beetle (Coleoptera: Curculionidae: Scolytinae)

ABSTRACT The exotic redbay ambrosia beetle, Xyleborus glabratus Eichhoff (Coleoptera: Curculionidae: Scolytinae), and its fungal symbiont Raffaellea lauricola Harrington, Fraedrich, and Aghayeva are responsible for widespread redbay, Persea borbonia (L.) Spreng., mortality in the southern United States. Effective traps and lures are needed to monitor spread of the beetle and for early detection at ports-of-entry, so we conducted a series of experiments to find the best trap design, color, lure, and trap position for detection of X. glabratus. The best trap and lure combination was then tested at seven sites varying in beetle abundance and at one site throughout the year to see how season and beetle population affected performance. Manuka oil proved to be the most effective lure tested, particularly when considering cost and availability. Traps baited with manuka oil lures releasing 5 mg/d caught as many beetles as those baited with lures releasing 200 mg/d. Distributing manuka oil lures from the top to the bottom of eight-unit funnel traps resulted in similar numbers of X. glabratus as a single lure in the middle. Trap color had little effect on captures in sticky traps or cross-vane traps. Funnel traps caught twice as many beetles as cross-vane traps and three times as many as sticky traps but mean catch per trap was not significantly different. When comparing height, traps 1.5 m above the ground captured 85% of the beetles collected but a few were caught at each height up to 15 m. Funnel trap captures exhibited a strong linear relationship (r2 = 0.79) with X. glabratus attack density and they performed well throughout the year. Catching beetles at low densities is important to port of entry monitoring programs where early detection of infestations is essential. Our trials show that multiple funnel traps baited with a single manuka oil lure were effective for capturing X. glabratus even when no infested trees were visible in the area.

Suitability of California bay laurel and other species as hosts for the non-native redbay ambrosia beetle and granulate ambrosia beetle.

The redbay ambrosia beetle Xyleborus glabratus Eichhoff is a non‐native vector of the pathogen that causes laurel wilt, a deadly disease of trees in the family Lauraceae in the southeastern U.S.A. Concern exists that X. glabratus and its fungal symbiont could be transported to the western U.S.A. and cause damage to California bay laurel Umbellularia californica (Hook. & Arn.) Nutt. in California and Washington. The present study evaluated in‐flight attraction, attack density and emergence of X. glabratus and another invasive ambrosia beetle Xylosandrus crassiusculus (Motschulsky) on cut bolts of California bay laurel and eight related tree species in an infested forest in South Carolina. Xylosandrus crassiusculus is not a vector of the laurel wilt pathogen but is a pest of nursery and ornamental trees. Mean catch of X. glabratus on California bay laurel bolts was not significantly different from catches on bolts of known X. glabratus hosts sassafras Sassafras albidum (Nutt.) Nees and swampbay Persea palustris (Raf.) Sarg. Mean attack density and adult emergence of both beetle species from California bay laurel was equal to or greater than all other tree species tested. Both beetle species readily produced brood in California bay laurel bolts. The results obtained in the present study suggest that California bay laurel may be negatively impacted by both of these invasive ambrosia beetles if they become established in the trees native range.

Impacts of prescribed fire on saproxylic beetles in loblolly pine logs

Abstract.  1. Studies addressing the immediate impacts of fire on forest arthropod communities and their implications for conservation are few, particularly for species within dead wood. To investigate the effects of fire on saproxylic beetles (Coleoptera), we randomly assigned large‐diameter loblolly pine (Pinus taeda L.) logs to a forest scheduled for a prescribed burn (i.e. a low‐intensity surface fire) or to an adjacent unburned forest in Georgia, USA.

The response of ground beetles (Coleoptera: Carabidae) to selection cutting in a South Carolina bottomland hardwood forest

We compared the response of ground beetles (Coleoptera: Carabidae) to the creation of canopy gaps of different size (0.13, 0.26, and 0.50 ha) and age (1 and 7 years) in a bottomland hardwood forest (South Carolina, USA). Samples were collected four times in 2001 by malaise and pitfall traps placed at the center and edge of each gap, and 50 m into the surrounding forest. Species richness was higher at the center of young gaps than in old gaps or in the forest, but there was no statistical difference in species richness between old gaps and the forests surrounding them. Carabid abundance followed the same trend, but only with the exclusion of Semiardistomis viridis (Say), a very abundant species that differed in its response to gap age compared to most other species. The carabid assemblage at the gap edge was very similar to that of the forest, and there appeared to be no distinct edge community. Species known to occur in open or disturbed habitats were more abundant at the center of young gaps than at any other location. Generalist species were relatively unaffected by the disturbance, but one species (Dicaelus dilatatus Say) was significantly less abundant at the centers of young gaps. Forest inhabiting species were less abundant at the centers of old gaps than in the forest, but not in the centers of young gaps. Comparison of community similarity at various trapping locations showed that communities at the centers of old and young gaps had the lowest similarity (46.5%). The community similarity between young gap centers and nearby forest (49.1%) and old gap centers and nearby forest (50.0%) was similarly low. These results show that while the abundance and richness of carabids in old gaps was similar to that of the surrounding forest, the species composition between the two sites differed greatly.

Conserving pollinators in North American forests: A review

ABSTRACT: Bees and butterflies generally favor open forest habitats regardless of forest type, geographic region, or methods used to create these habitats. Dense shrub layers of native or nonnative species beneath forest canopies negatively impact herbaceous plant cover and diversity, and pollinators. The presence of nonnative flowers as a source of nectar, pollen, or larval food can have positive or negative effects on pollinators depending on the situation, but in cases where the nonnatives exclude native plants, the results are almost always negative. Roads and roadside corridors offer an opportunity to increase open, pollinator-friendly habitat even in dense forests by thinning the adjacent forest, mowing at appropriate times, and converting to native herbaceous plant communities where nonnative species have been planted or have invaded. Efforts to improve forest conditions for pollinators should consider the needs of specialist species and vulnerable species with small scattered populations. Conservation of bees and butterflies, as well as other pollinating species, in forested areas is important for most forest plant species, and forests may serve as reservoirs of pollinators for recolonization of surrounding habitats.

Influence of Trap Color on Collection of the Recently-Introduced Bean Plataspid, Megacopta cribraria (Hemiptera: Plataspidae)

Large numbers of the exotic bean plataspid, Megacopta cribraria (F.) (Hemiptera: Plataspidae). were first collected from several northeast Georgia counties beginning in October 2009 (Suiter and Ames 2009, Statewide Pest Alert). How this insect arrived in the United States and where it came from is still not known. The native range of M. cribraria is reported to be throughout Asia and the Indian Subcontinent (Hosokawa et at 2007 t Proc. R. Soc. B. 274: 1979 -1984; Srinivasaperumal et aI. 1992, Proc.lndian Natn. Sci. Acad. 6: 333 - 340; Hua 2000, List of Chinese Insects. Vol. 1, Zhong-shan Univ. Press. Guangzhou. 251 pp.). It is similar to other Plataspidae in having a somewhat unusual symbiotic relationship with its gut bacteria. Before laying eggs, females deposit particles containing the symbiont which are then eaten by newly-hatched nymphs under natural conditions. Nymphs experimentally deprived of access to the symbiont exhibited slower growth, smaller body sizes, and higher mortality. Thus, presence of the obligate symbiont was predictive of the insects status as a pest (Hosokawa at al. 2007). Preliminary testing of M. cribraria in Georgia showed that all individuals evaluated contained the symbiont (Jenkins et a1. 2010, J. Entomol. Sci. 45: 62 - 63).

Herbivorous insect response to group selection cutting in a southeastern bottomland hardwood forest

Abstract Malaise and pitfall traps were used to sample herbivorous insects in canopy gaps created by group-selection cutting in a bottomland hardwood forest in South Carolina. The traps were placed at the centers, edges, and in the forest adjacent to gaps of different sizes (0.13, 0.26, and 0.50 ha) and ages (1 and 7 yr old) during four sampling periods in 2001. Overall, the abundance and species richness of insect herbivores were greater at the centers of young gaps than at the edge of young gaps or in the forest surrounding young gaps. There were no differences in abundance or species richness among old gap locations (i.e., centers, edges, and forest), and we collected significantly more insects in young gaps than old gaps. The insect communities in old gaps were more similar to the forests surrounding them than young gap communities were to their respective forest locations, but the insect communities in the two forests locations (surrounding young and old gaps) had the highest percent similarity of all. Although both abundance and richness increased in the centers of young gaps with increasing gap size, these differences were not significant. We attribute the increased numbers of herbivorous insects to the greater abundance of herbaceous plants available in young gaps.