Volume 46: Issue 3

Hemipteran pests feed directly on cotton fruiting structures (bolls) causing damage to fiber and yield. Herbivore-induced volatile emissions have been well studied with regard to leaf-chewing insects, but no research has examined the release of volatiles from developing cotton bolls in response to damage from piercing-sucking insects. We compared volatile emissions from bolls in response to feeding damage by brown stink bug, Euschistus servus (Say), southern green stink bug, Nezara viridula, (L.), and the leaf footed bug, Leptoglossus phyllopus (L.) under laboratory conditions. Volatile emissions from bolls in response to N. viridula and mechanical damage were investigated under field conditions. Volatiles were collected using dynamic head-space sampling and analyzed by gas chromatography/mass spectrometry. Under laboratory conditions, feeding by hemipterans resulted in a significant increase in volatile emissions from bolls compared with undamaged bolls. Damaged bolls released significantly greater amounts of acyclic terpenes and methyl ketones compared with undamaged bolls. Feeding by different hemipteran species elicited a similar quantitative increase in emissions, but significant differences were detected in the emissions of some individual compounds. Under field conditions, feeding damage by N. viridula resulted in significantly greater volatile emissions compared with undamaged and mechanically-damaged bolls indicating that physical damage alone did not account for the complete blend of volatiles released in response to biotic injury. During feeding, hemipterans inject a complex blend of salivary and digestive enzymes, and some of these compounds may activate volatile induction from bolls. The implication for piercing-sucking damage on biochemical pathways mediating volatile synthesis is discussed.

The onion thrips, Thrips tabaci (Lindeman), is the only known vector of Iris yellow spot virus (IYSV). IYSV was detected in Georgia for the first time in 2003. Phylogenetic analysis using nucleotide sequences of the IYSV capsid gene indicated that it may have been accidentally introduced from repackaging of imported Peruvian onions in the Vidalia onion-growing region. The tobacco thrips, Frankliniella fusca (Hinds), has been the dominant thrips species on onions in Georgia. However, in recent years the incidence of T. tabaci on onions has been consistently increasing. Laboratory competition studies indicated that T. tabaci outcompeted F. fusca on onion foliage. This led to speculation that a new biotype of T. tabaci may have been introduced along with IYSV through importation of Peruvian onions. This hypothesis was tested by analyzing variations in the mitochondrial cytochrome oxidase I gene and internal transcribed spacer region 2 of T. tabaci populations from Georgia and Peru. DNA was extracted from T. tabaci samples from Georgia and Peru and subjected to PCR using specific primers. The resulting amplicons were sequenced. Parsimony and Bayesian analysis of the COI sequences indicated that all the Peruvian taxa fell into a single clade along with one Georgia taxon. All the other Georgia taxa were in a separate clade. ITS2 sequence comparisons indicated that Georgia and Peru taxa were found in numerous clades. High variation among taxa from each region indicated that ITS2 may not be suitable to assess intraspecific variation among T. tabaci populations.

Coupled gas chromatography and electroantennogram detection (GC-EAD) analyses of headspace volatiles from apple host tissues revealed a total of 16 compounds to which female dogwood borer, Synanthedon scitula (Harris), antennae responded. There were no differences in the amplitude of the response of antennae from virgin and mated females, and no consistent responses to host odors were generated from male antennae. Four compounds, including octanal, nonanal, decanal, and methyl salicylate, were identified from all headspace collections taken from apple trees. Use of the solid-phase microextraction (SPME) technique revealed that a single volatile compound, α-bergamotene, emanating from larval dogwood borer frass elicited a strong female antennal response. This compound was also present in headspace collections from ‘Red Chief Delicious’ apple trees with burr knot tissue infested with dogwood borer larvae and from 1-d-old cut bark on ‘Granny Smith’ trees, suggesting that it is produced by apple trees in response to injury. An additional compound, methyl-2,4-decadienoate, present only in headspace collections from burr knots infested with dogwood borer larvae on ‘Granny Smith’ trees elicited a strong female antennal response.

American chestnut [Castanea dentata (Marshall) Borkhausen, Fagales: Fagaceae] was a dominant forest tree in the eastern forests of the U.S. until it was eliminated as a canopy tree species by 2 exotic pathogens. Ink disease, a root rot caused by Phytophthora cinnamomi Rands (Pythiales: Pythiaceae), began to destroy chestnut populations on bottomland and poorly-drained sites in the mid-1800s, and the chestnut blight fungus [Cryphonectria parasitica (Murrill) Barr, Diaporthales: Cryphonectriaceae] reduced the species to short-lived sprouts on upland sites in the first half of the 20^th Century (cf. Campbell and Schlarbaum

Relationship Between Frankliniella occidentalis (Thysanoptera: Thripidae) Population Density and Three of Its Natural Enemies in Commercial Lemon Orchards in Mexico¹

Saúl Pardo-Melgarejo,

Filemón Morales-Hernández,

Jaime González-Cabrera,

Mario A. Miranda-Salcedo,

Juan Carlos Álvarez-Hernández,

J. Concepción Rodríguez-Maciel,

Alejandra Mondragón-Flores,

Bismarck Aguilar-Garzón, and

Karen Vianey Díaz Arias

Volatile Emissions from Developing Cotton Bolls in Response to Hemipteran Feeding Damage

Assessment of Variation Among Thrips tabaci Populations from Georgia and Peru Based on Polymorphisms in Mitochondrial Cytochrome Oxidase I and Ribosomal ITS2 Sequences

Electrophysiological Response of Female Dogwood Borer (Lepidoptera: Sesiidae) to Volatile Compounds from Apple Trees

Influence of Four Ground Cover Vegetation Types Used in North Carolina Fraser Fir Christmas Tree Plantations on Abundance and Species Composition of Phytoseiid Mites (Acari: Phytoseiidae)

Capture of Two Moth Species in Traps Placed at Different Heights in Sex Pheromone Treated Apple Orchards

Growth Inhibition of Dalmatian Toadflax, Linaria dalmatica (L.) Miller, in Response to Herbivory by the Biological Control Agent Mecinus janthinus Germar

Mosquito Species (Diptera: Culicidae) Reported from Shandong Province, China

Mortality of the Cycad Aulacaspis Scale (Hemiptera: Diaspididae) by the Entomopathogenic Fungus Isaria fumosorosea Wize under Laboratory Conditions

Incidence of Craesus castaneae (Hymenoptera: Tenthredinidae) on Chestnut Seedlings Planted in the Daniel Boone National Forest, Kentucky

Relationship Between Frankliniella occidentalis (Thysanoptera: Thripidae) Population Density and Three of Its Natural Enemies in Commercial Lemon Orchards in Mexico¹

A Review of the Host Plant Records of Phthorimaea absoluta (=Tuta absoluta) (Lepidoptera: Gelechiidae)¹

Carabidae (Coleoptera: Harpalinae: Harpalini: Harpalina) from an Upper Cretaceous Rock Deposit at Orapa Diamond Mine in Botswana¹

Chemical Mechanism of Exogenous Jasmonic Acid-Induced Resistance in Rose Against Spodoptera exigua (Lepidoptera: Noctuidae)¹

Interference with Fatty Acyl-CoA Reductase Reduces Wax Secretion and Influences the Development of Male Ericerus pela (Hemiptera: Coccoidae) Nymphs¹