Richard L. Ridgway

Effect of plants on the searching efficiency of a generalist predator: the importance of predator‐prey spatial association

In most studies of tritrophic interactions, the effect of plants on predators is confounded with changes in prey and predator behaviors after an encounter event. Here, we estimate how the effect of plants on prey distribution (in the absence of the predator) and on predator foraging behavior (in the absence of prey) may influence predation rate of Orius insidiosus (Say) (Heteroptera: Anthocoridae) in 11 plant by prey species combinations. The within‐leaf distributions of O. insidiosus and its prey overlapped most on bean plants. The predators foraging behavior (e.g., walking speed, turning rate) also differed among plant species. Simulations, using the prey distribution data and predators foraging patterns on leaf surfaces of each plant species, show that, overall, the searching efficiency of O. insidiosus was higher on leaves of bean and corn than of tomato. However, the predators searching efficiency was not consistent within plant species. Thus, the combined effect of plants directly on the predator and indirectly through the prey influenced the predators searching efficiency.

Isolation of high-molecular-weight DNA from insects.

A simple and rapid method for the isolation of high-molecular-weight DNA from insects is described. The method does not require CsCl ultracentrifugation or extensive dialysis. High-molecular-weight DNA was obtained within 24 h. Since the entire insect was used for DNA isolation, an initial nuclei-enriched fraction was required. Genomic DNA was extracted from lysed nuclei by organic phase separation (liquid/liquid extraction). This method has been successfully applied to the isolation and purification of DNA from eight different adult insects (Heliothis zea, Musca autumnalis, M. domestica, Blatta orientalis, Tenebrio molitor, Lymantria dispar, Ostrinia nubilalis, and Manduca sexta). The recovered DNA can be cleaved with restriction endonucleases, ligated efficiently using standard cloning vectors, and hybridized to synthetic oligonucleotides.

Host Plant Effects on the Activity of Selected Nuclear Polyhedrosis Viruses Against the Corn Earworm and Beet Armyworm (Lepidoptera: Noctuidae)

Abstract The activity of the nuclear polyhedrosis virus (NPV) of the celery looper, Anagrapha falcifera (Kirby) (AfMNPV), against the beet armyworm, Spodoptera exigua (Hübner), was greatest when the virus was fed to larvae on foliage of tomato, Lycopersicon esculentum Mill., least on cotton, Gossypium hirsutum (L.), and intermediate on collard, Brassica oleracea L. Activity of AfMNPV against the corn earworm, Helicoverpa zea (Boddie), was greatest on corn, Zea mays L., least on cotton, and intermediate on bean, Phaseolus vulgaris L. Survival time (days between the start of the test and death) of larvae that were killed by virus was usually lower on treatments on which rates of mortality were higher, but these differences were usually small (≤1 d). Effects of host plants on viral activity were not related closely to their effects on larval feeding rates. Effects of host plants on viral activity were also not specific to AfMNPV; cotton and collard affected AfMNPV and the homologous NPV of the beet armyworm to similar degrees. Similar results were found for AfMNPV and the homologous NPV of the corn earworm on cotton and bean. Levels of control provided by these viruses may thus be higher on tomato or corn than on cotton, and intermediate on collard or bean.

Enhancement of Activity of Bacillus thuringiensis Berliner Against Four Lepidopterous Insect Pests by Nutrient-Based Phagostimulants1

To help improve control of insect pests with microbial insecticides, we investigated the interactions of four commercial, nutrient-based phagostimulants (Pheast [AgriSense], Coax [CCT Corp.], Gusto [Atochem North America, Inc.], and Entice [Custom Chemicides] with Bacillus thuringiensis Berliner and four lepidopterous insect pests (gypsy moth, Lymantria dispar [L.] [Lymantriidae]; corn earworm, Helicoverpa zea [Boddie] [Noctuidae]; European corn borer, Ostrinia nubilalis [Hubner] [Pyralidae]; and diamondback moth, Plutella xylostella [L.] [Plutellidae]). Comparisons were made of treated foliage in Petri dishes in the laboratory and of sprayed whole plants in a greenhouse. In general, phagostimulants increased mortality of all species tested, but no consistent differences among phagostimulants were found for any species. Food consumption was generally lower on the treatments that contained phagostimulants causing the highest rates of mortality, possibly as a result of more rapid ingestion of a lethal dose ...

Nuclear Polyhedrosis Virus of the Gypsy Moth (Lepidoptera: Lymantriidae): Potency and Effects of Selected Adjuvants on Insect Feeding Behavior

The potency of two formulations of the nuclear polyhedrosis virus of the gypsy moth (LdMNPV) was evaluated in the laboratory. Both formulations were prepared with the same batch of LdMNPV produced in live insects by the USDA Forest Service. A Forest Service-recommended tank-mix preparation (LdMNPV, molasses, ultraviolet light screen, and sticker in water) was found to be about 20 times more potent than an experimental wettable powder preparation. The wettable powder also deterred feeding; the 20-fold difference in potency, though, is based on actual doses consumed. The addition of a stilbenedisulfonic acid derivative, Blankophor BBH, to the tank-mix and wettable powder preparations at a concentration of 1% (wt./vol.) reduced the LD50s by 42- and 214-fold, respectively. Blankophor BBH was also a moderate feeding deterrent to gypsy moth, Lymantria dispar (L.), larvae which could limit its efficacy as an enhancer of the virus. However, the addition of molasses to Blankophor BBH at least partially overcame th...

Control of Third and Fourth Instar Gypsy Moth (Lepidoptera: Lymantriidae) with Gypchek Combined with a Stilbene Disulfonic Acid Additive on Individual Shade Trees1

The efficacy of the gypsy moth (Lymantria dispar (L.)) nuclear polyhedrosis virus (LdMNPV), Gypchek, in combination with a stilbene disulfonic acid additive, Blankophor BBH, was evaluated against third and fourth-instar gypsy moth in 1992. Treatments were applied with hydraulic ground equipment to plots of one to three oak trees each in a gypsy moth-infested woodlot on the eastern shore of Maryland. An analysis of larvae collected from the plots revealed that the plots treated with LdMNPV and Blankophor BBH had significantly (P < 0.05) more larval mortality and significantly lower LT50 values than did plots treated with LdMNPV alone. Additionally, Blankophor BBH applied alone appeared to interact with native virus present in the field plots and significantly (P < 0.05) increased larval mortality when compared with untreated plots. The implications of these results for the potential use of LdMNPV in combination with a stilbene disulfonic acid additive are discussed.

Laboratory evaluation of selected spray adjuvants as ultraviolet light protectants for the nuclear polyhedrosis virus of the celery looper (Lepidoptera: Noctuidae).

Four spray adjuvants were tested in the laboratory as ultraviolet light (UV) protectants for the nuclear polyhedrosis virus of the celery looper, Anagraphs falcifera (Kirby) (AfMNPV), against the b...

A Strain of Serratia marcescens (Enterobacteriaceae) with High Virulence Per Os to Larvae of a Laboratory Colony of the Corn Earworm (Lepidoptera: Noctuidae)

An unpigmented strain of the bacterium Serratia marcescens Bizio that is highly virulent when fed to larvae from a laboratory colony of the corn earworm, Helicoverpa zea (Boddie), was found as a co...

A computerized data management and decision support system for gypsy moth management in suburban parks

Abstract The GYpsy Moth Management Decision support SYStem (GYMSYS) was developed to address specific data management and decision support needs for gypsy moth management in urban parks and other wooded public lands. These needs include a map-based user interface, simple and reliable data entry, a means to customize the system to a variety of separate and heterogeneous management units and programs, and the use of readily available and inexpensive hardware and software systems. These needs were addressed by incorporating a map image, selected by the user, into the background of the user interface, making it possible for the user to configure the system separately for each individual management unit, and utilizing Apple Macintosh computers and Hypercard software. A knowledge base for making treatment decisions based on egg mass density and size, host tree susceptibility, and defoliation history was encoded into a production rule base.

Activity and Persistence of the Nuclear Polyhedrosis Virus of the Celery Looper (Lepidoptera: Noctuidae) with A Feeding Stimulant and a Stilbene-Derived Enhancer

A nutrient-based feeding stimulant and a diaminostilbene disulfonic acid-derived enhancer (fluorescent brightener, Blankophor BBH®; Burlington Chemical, Burlington, NC) were evaluated as adjuvants ...