Seth J. Johnson

The Large Decapitating Fly Pseudacteon litoralis (Diptera: Phoridae): Successfully Established on Fire Ant Populations in Alabama

ABSTRACT The large fire ant decapitating fly, Pseudacteon litoralis Borgmeier, from northeastern Argentina was successfully released as a self-sustaining biocontrol agent of imported fire ants in south central Alabama in 2005. Five years later, this fly is firmly established at the original release site and has expanded outward at least 18 km. Nevertheless, populations remain very low considering P. litoralis is one of the most abundant fire ant decapitating flies in large areas of its range in South America. The reasons for low densities and why we were only able to establish this fly at 1 of 9 release sites in 4 states (2003–2006) are unknown, but problems with host-matching, release procedures, weather conditions, and competition with previously released decapitating flies are discussed as possible factors.

Status of the Fire Ant Decapitating Fly Pseudacteon tricuspis (Diptera: Phoridae) in Louisiana

Abstract Eight releases of the South American fire ant decapitating fly, Pseudacteon tricuspis Borgmeier, were conducted in Louisiana from 1999 to 2006. Although P. tricuspis was initially recaptured at 88% of the release sites, four of the releases ultimately failed, so long-term establishment was only 43%. Fly populations from two releases have expanded out 50-80 km from their release sites (Fall 2006).

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

ABSTRACT n 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.

Efficacy of Bacillus thuringiensis and Cabbage Cultivar Resistance to Diamondback Moth (Lepidoptera: Yponomeutidae)

Population density estimates were used to determine the effectiveness of a commercial formulation of Bacillus thuringiensis Berliner subspp. kurstaki and aizawai (Agree 50 WP®) and host plant resistance in three cabbage cultivars against the diamondback moth, Plutella xylostella (L.). Cabbage plots treated with Agree 50 WP® had significantly fewer larvae per plant compared with untreated ones. The ranking from most to least susceptible of the three main cabbage cultivars grown in Jamaica was ‘KY Cross’ > ‘Early Jersey’ > ‘Tropicana’. These findings provide evidence that a new cabbage hybrid, ‘Tropicana’, and products containing effective strains of B. thuringiensis may be successfully used for P. xylostella management in Jamaica.

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

ABSTRACT n 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.

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.

GRAVIMETRIC METHOD FOR THE MEASUREMENT OF SUGAR CONSUMPTION BY ADULT VELVETBEAN CATERPILLAR (LEPIDOPTERA: NOCTUIDAE)

Determination of food consumption by adult Lepidoptera, especially noctuid species, has not been well studied, possibly because of a lack of appropriate methodology. In order to measure sugar consumption by velvetbean caterpillar, Anticarsia gemmatalis Hubner, a gravimetric method was developed and is presented here together with results obtained using this method. After 24-h exposure to a moth, liquid consumption by the moth was determined by weighing the remaining solution on an electronic balance. The amount of solution consumed was calculated by converting the difference between the weight of the remaining solution and that of the unfed control to a volumetric value. Velvetbean caterpillar moths consumed a significantly greater volume of solution at lower sugar concentrations than at higher concentrations. Female moths from larvae reared on soybean foliage in field cages consumed three times that of moths from larvae reared on artificial diet in the laboratory. This method was simple, accurate, and required minimum handling of test insects. It was suitable for the measurement of food consumption of velvetbean caterpillar moths and could also be suitable for other lepidopteran species.

The Reproductive Morphology and Physiological Age Grading of the Female Salvinia Weevil, Cyrtobagous salviniae Calder and Sands:

The morphology of the female Cyrtobagous salviniae Calder and Sands reproductive system is similar to other weevil species being meroistic and telotrophic. The reproductive system is composed of 2 ovaries each containing 2 ovarioles where the follicles mature. A physiological age grading system was developed where the continuum of ovarium development was divided into 2 nulliparous and 3 parous classes. This was based on the differentiation of the ovarioles, presence, and appearance of follicular relics, cuticle hardness/coloration, and fat body quantity/appearance. High correlation occurred between the parous classes and number of eggs produced where the P3 class had over 9-fold higher number of eggs in comparison with the P1 class. Mean number of eggs produced for each parous class was significantly different, however, overlap occurred. Such a system enables a determination of the past, present, and future reproductive status of field populations and mass-rearing colonies.

Adults of the Waterfern Weevil, Stenopelmus rufinasus Gyllenhal (Coleoptera: Curculionidae), Feed on a Non-Host Plant, Salvinia minima Baker, in Louisiana

The waterfern weevil, Stenopelmus refinasus Gyllenhal, has previously been reported as host-specific, only feeding on plants in the genus Azolla. We report the first observations of S. rufinasus feeding on a non-host plant, Salvinia minima Baker, within the United States.