Katherine Parys

Baseline Susceptibility of Lygus lineolaris (Hemiptera: Miridae) to Novaluron

Abstract Tarnished plant bug, Lygus lineolaris (Palisot de Beauvois), populations were collected from field locations in the Mississippi River Delta of Arkansas, Louisiana, and Mississippi. Third-instar F1 nymphs from each field location, in addition to a laboratory colony, were screened for susceptibility to novaluron. Both a glass vial bioassay and a diet-incorporated bioassay used dose-response regression lines to calculate LC50 and LC90 values for novaluron. Mean LC50s for glass vial bioassays ranged from 44.70 ± 3.58 to 66.54 ± 4.19 µg/vial, while mean LC50s for diet-incorporated bioassays ranged from 12.10 ± 0.77 to 17.63 ± 2.42 µg/200 ml of artificial diet. A comparison of LC50 values from the same field population screened using both bioassay methods failed to show a relationship. LC50 values from field locations were compared with a historically susceptible population from Crossett, AR. Results indicated that considerable variability in susceptibility to novaluron exists within field populations of tarnished plant bugs across the Delta, including some locations with lower LC50 values than a historically susceptible population.

Evidence of Establishment of Bagous hydrillae (Coleoptera: Curculionidae), a Biological Control Agent of Hydrilla verticillata (Hydrocharitales: Hydrocharitaceae) in North America?

ABSTRACT The semi-aquatic weevil Bagous hydrillae was released during 1991–1996 at 19 sites in 4 states in attempts to control the aquatic weed hydrilla, Hydrilla verticillata. Fourteen of the sites were in Florida, 2 each in Texas and Georgia and one site in Alabama. Over 320,000 adult weevils were included in these releases. Despite the fact that a few adults were recovered as late as 4.5 yr post-release, presence of permanent, self-perpetuating populations was never confirmed. Then, during 2009 adult B. hydrillae were collected in southern Louisiana, at least 580 km from the nearest release site and 13 yr after attempts to establish this insect had terminated. This suggests that earlier recoveries were indicative of successful establishment and that this weevil species has persisted and dispersed widely in the southeastern USA. Nonetheless, there is no evidence that B. hydrillae has had a suppressive effect on hydrilla.

Longitudinal Measurements of Tarnished Plant Bug (Hemiptera: Miridae) Susceptibility to Insecticides in Arkansas, Louisiana, and Mississippi: Associations with Insecticide Use and Insect Control Recommendations

Concentration-response assays were conducted from 2008 through 2015 to measure the susceptibility of field populations of Lygus lineolaris (Palisot de Beauvois) from the Delta regions of Arkansas, Louisiana, and Mississippi to acephate, imidacloprid, thiamethoxam, permethrin, and sulfoxaflor. A total of 229 field populations were examined for susceptibility to acephate, 145 for susceptibility to imidacloprid, and 208 for susceptibility to thiamethoxam. Permethrin assays were conducted in 2014 and 2015 to measure levels of pyrethroid resistance in 44 field populations, and sulfoxaflor assays were conducted against 24 field populations in 2015. Resistance to acephate and permethrin is as high or higher than that previously reported, although some populations, especially those exposed to permethrin, appear to be susceptible. Variable assay responses were measured for populations exposed to imidacloprid and thiamethoxam. Average response metrics suggest that populations are generally susceptible to the neonicotinoids, but a few populations from cotton fields experiencing control problems exhibited elevated LC50s. Efforts to associate variability in LC50s with recorded use of insecticides and estimated cotton insect losses and control costs suggest that intensive use of insecticides over several decades may have elevated general detoxifying enzymes in L. lineolaris and some field populations may be exhibiting resistance to multiple classes of insecticide. These results suggest that efforts should be made to manage these pests more efficiently with a reduced use of insecticides and alternative controls.

The Giant Resin Bee, Megachile sculpturalis Smith: New Distributional Records for the Mid- and Gulf-south USA

Abstract Background Megachile (Callomegachile) sculpturalis Smith, the giant resin bee, is an adventive species in the United States. First established in the United States during the early 1990s, records currently exist from most states east of the Mississippi River along with Iowa and Kansas. New information New distributional records are presented for Megachile (Callomegachile) sculpturalis Smith, an introduced bee. Additional records presented here expand the known distribution southwest through Arkansas, Louisiana, Mississippi, Missouri, and Texas. An updated host plant list containing new records is also presented, expanding the number of known floral associations.

Biological Control of Common Salvinia (Salvinia minima) in Louisiana using Cyrtobagous salviniae (Coleoptera: Curculionidae)

ABSTRACT Common salvinia, Salvinia minima Baker, is an aquatic invasive fern that obstructs waterways and impacts water quality throughout the southeastern United States. In an effort to establish populations for classical biological control of this weed, the weevil, Cyrtobagous salviniae Calder and Sands, was released at multiple sites across Louisiana. Many of the release sites were lost due to a variety of ecological and anthropological disturbances. In 2008, C. salviniae was found to have successfully overwintered on S. minima in Gramercy, Louisiana. Attack by Cyrtobagous salviniae significantly increased the number of damaged terminal buds and decreased the fresh weight biomass of S. minima.

Checklist of insects associated with Salvinia minima Baker in Louisiana, USA

This study presents a list of adult insects (excluding Diptera and Lepidoptera) collected from an infestation of an invasive aquatic weed, common salvinia ( Salvinia minima Baker), in southern Louisiana, USA. Insects were sampled from May – November of 2009 and 2010 using floating pitfall traps. A total of 7,933 specimens were collected, representing seven orders, 70 families, and 235 species. Species of note include three currently undescribed species of Coleoptera, one previously undescribed braconid wasp, two new state records of Curculionidae, a new state generic record for the family Limnichidae, and a new record for the United States.

First Record of Pyramica epinotalis (Hymenoptera: Formicidae) for the United States

Pyramica epinotalis is an arboreal dacetine ant previously known only from Brazil, Costa Rica, Ecuador, and southern Mexico. Here we report the first records of P. epinotalis for the United States. Collections were made in three parishes across southern Louisiana in cypress-tupelo swamps using floating pitfall traps placed in floating vegetation and arboreal pitfall traps placed on trunks and limbs of three wetland tree species. One additional specimen of this species was collected in Highlands County, Florida. Based on collections of specimens in Louisiana, including multiple dealate females at different localities, P. epinotalis appears to be well established in this state. We discuss the design and implementation of modified arboreal pitfall traps that were instrumental in this discovery.

Impact of the Red Imported Fire Ant, Solenopsis invicta (Hymenoptera: Formicidae), on Biological Control of Salvinia minima (Hydropteridales: Salviniaceae) by Cyrtobagous salviniae (Coleoptera: Curculionidae)

ABSTRACT A 2-yr study of the impacts of the red imported fire ant, Solenopsis invicta Buren, on the success of Cyrtobagous salviniae Calder & Sands as a biological control agent of common salvinia, Salvinia minima Baker, was undertaken in southern Louisiana. Floating moats were constructed around 8 release sites where C. salviniae was introduced as a biological control agent. These moats were used to restrict access to the release site by red imported fire ants in half the quadrats. Moating was successful in limiting the number of red imported fire ants in the release sites over the course of the study (P < 0.0001). In 2010, locations where access by red imported fire ants was limited by the presence of a moat had lower biomass (P = 0.04) and higher populations of C. salviniae (P < 0.0001). Our study suggests that the presence of red imported fire ants negatively impacts the success of C. salviniae as a biological control agent.

Patterns of Tarnished Plant Bug (Hemiptera: Miridae) Resistance to Pyrethroid Insecticides in the Lower Mississippi Delta for 2008–2015: Linkage to Pyrethroid Use and Cotton Insect Management

Abstract Populations of tarnished plant bug, Lygus lineolaris (Palisot de Beauvois) (Hemiptera: Miridae), from the Lower Mississippi Delta regions of Arkansas, Louisiana, and Mississippi were evaluated from 2008 through 2015 for susceptibility to pyrethroid insecticides using a diagnostic-dose assay with permethrin. Resulting data add to the compilation of pyrethroid susceptibility data carefully tracked in this pest since 1994 and provide continuing evidence of high frequencies of pyrethroid resistance in field populations of the tarnished plant bug. Resistance levels are variable, and some populations remain susceptible suggesting practical value in the continued use of the diagnostic-dose assays prior to pyrethroid treatments. Recent studies with dose–response models suggest that levels of pyrethroid resistance in some populations may still be evolving, with some populations requiring higher doses to reach levels of control comparable to those observed 10 yr ago. Concerns for frequent use of multiple classes of insecticides and possible selection for tarnished plant bugs with metabolic resistance mechanisms capable of detoxifying available insecticide chemistries warrant continued efforts to manage resistance in this important crop pest. Associations among measured pyrethroid resistance levels, published data on annual use of pyrethroid insecticides, and annual estimates of cotton insect losses and control costs were explored and summarized for the 8 yr of this investigation. Mortality of tarnished plant bugs at the diagnostic-dose of permethrin was negatively correlated with kilograms of pyrethroids applied per acre of harvested cropland.

Comparison of Three Bioassay Methods to Estimate Levels of Tarnished Plant Bug (Hemiptera: Miridae) Susceptibility to Acephate, Imidacloprid, Permethrin, Sulfoxaflor, and Thiamethoxam

A laboratory colony of tarnished plant bugs reared solely on a meridic diet was exposed to acephate, imidacloprid, permethrin, sulfoxaflor, and thiamethoxam in dose-response experiments using floral-foam, glass-vial, and dipped-leaf assays. Results indicated that different assay methods produced different relative results across the different insecticides. Dose- and time-response regression models also indicated that length of exposure of tarnished plant bugs to insecticide-treated plant tissue is important. Time of exposure required to reach an LC90 at estimated recommended field rates suggested that the recommended lower field rate of acephate (0.56 kg ai/ha) would reach an LC90 of exposed tarnished plant bugs between 48 and 96 h post initial exposure. An LC90 of tarnished plant bugs exposed to permethrin (0.11 kg ai/ha) was not predicted from the regression modes over the 168-h observation; lower recommended application rates of imidacloprid (0.053 kg ai/ha), sulfoxaflor (0.053 kg ai/ha), and thiamethoxam (0.042 kg ai/ha) reached projected LC90s between 96 and 168 h of exposure. Collectively, the results of this study corroborate current existing procedures for tracking tarnished plant bug resistance to insecticides, but also illustrate the importance of additional field studies that empirically associate assay results to projected field control.