Robert F. W. Schroder

Evaluation of a Water-Soluble Bait for Corn Rootworm (Coleoptera: Chrysomelidae) Control

Laboratory and field-cage experiments evaluated the efficacy of a water-soluble bait for control of adult diabroticites. The bait was composed of a water-soluble feeding stimulant derived from a bi...

Stabilization of cucurbitacin E-glycoside, a feeding stimulant for diabroticite beetles, extracted from bitter Hawkesbury watermelon

Cucurbitacins are feeding stimulants for diabroticite beetles, including corn rootworms and cucumber beetles, which can be added to a bait containing an insecticide thereby reducing the levels of other insecticide treatments needed to control these pests. One of them, cucurbitacin E-glycoside, is water soluble and easily processed from mutant bitter Hawkesbury watermelons (BHW) that express elevated levels of cucurbitacin. Storage of BHW extract at room temperature resulted in a 92% reduction of cucurbitacin E-glycoside over two months, while refrigeration or freezing resulted in a 60% loss of the active ingredient during this time. The loss of the active ingredient was correlated with an increase in BHW extract pH from 5 to greater than 9. The increase in pH of the BHW extracts at room temperature appeared to be due to the growth of certain bacteria, especially Bacillus spp. In refrigerated extracts, the pH remained relatively constant, and bacterial growth was dominated by bacteria such as Lactobacilli. An alternative to refrigeration is concentration of BHW extract. One means of concentration is spray drying, but the high sugar content of the BHW extract (20mg/ml glucose, 40mg/ml fructose) makes this technique impractical. Fermentation of the BHW extract by the yeast, Saccharomyces boulardii, eliminated the sugars and did not raise the pH nor alter the cucurbitacin E-glycoside content of the extract. Elimination of the sugars by fermentation produced an extract that could be successfully spray dried. BHW extract fermented by S. boulardii produced a higher level of feeding stimulation for spotted cucumber beetles in laboratory choice tests. When applied to cucumbers, there was no difference in control of spotted and striped cucumber beetles between baits of fresh or fermented juices combined with the same insecticide.

Temperature effects on the susceptibility of the Colorado potato beetle (Coleoptera: Chrysomelidae) to Beauveria bassiana (Balsamo) Vuillemin in Poland, the Czech Republic and the United States.

Beauveria bassiana (Balsamo) Vuillemin is a fungus with broad spectrum insecticidal activity. As a biological control agent used against Colorado potato beetles (Leptinotarsa decemlineata (Say)), this fungus has performed erratically in various field studies. This inconsistent performance has been attributed to formulation problems, UV sensitivity, and humidity. In a multi-site test, B. bassiana controlled Colorado potato beetle larvae in both Poland and the Czech Republic, but not in Maryland. Control was measured by reduction in populations of beetle larvae. One of the major differences among these sites was temperature. In Poland, the mean temperature ranged from 5°C to 23°C; in the Czech Republic the average temperature ranged from 6.7°C to 18.7°C; and in Maryland, temperatures at time of application exceeded 45°C at canopy level. This led us to examine B. bassiana growth in vitro.While B. bassiana grew in the laboratory from 16 to 30°C, the B. bassiana from a formulated product (Mycotrol™, Mycotech, ...

Spectral Characterization of Cucurbitacins in a Bitter Mutant of Hawkesbury Watermelon (Citrullus vulgaris Schrad) that Elicit a Feeding Response to Diabroticite Beetles (Coleoptera: Chrysomelidae)2

Fractions obtained by open-column flash chromatography of a crude methanolic extract of the rind of a bitter mutant of Hawkesbury watermelon, Citrullus vulgaris Schrad, were further purified by preparative high-performance liquid chromatography (HPLC) to isolate chemical component(s) that elicit a visitation/feeding stimulancy response to the southern corn rootworm, Diabrotica undecimpunctata howardi Barber. Activity of chromatographic fractions were followed with a laboratory bioassay involving total insect-response counts. The chemical structure of the most active component in C. vulgaris was confirmed by chemical ionization mass spectrometry and proton nuclear magnetic resonance spectroscopy to be cucurbitacin-E glycoside. Two other cucurbitacin-like compounds were isolated and structures for them postulated. A procedure to prepare a crude, biologically active, extract of C. vulgaris is reported. Dose-response data for the crude extract in laboratory tests against two diabroticite beetles D. undecimpun...

THE INTEGRATION OF A BACTERIUM AND PARASITES TO CONTROL THE COLORADO POTATO BEETLE AND THE MEXICAN BEAN BEETLE

Sprays of Bacillus thuringiensis subsp. thuringiensis (B.t.t.), which contained the beta-exotoxin, were applied to small-scale field plots of tomatoes infested with the Colorado potato beetle [Lept...

Distribution and biological control significance of Colorado potato beetle spiroplasmas in North America.

Abstract The Colorado potato beetle spiroplasma, a helical wall-less bacterium, attaches to the midgut of larval and adult Leptinotarsa decemlineata (Say). Despite its lack of pathogenicity to the beetle, its host specificity and ease of transmission may prove useful in biological control if insecticidal genes (e.g. the Bacillus thuringiensis subsp. tenebrionis δ-endotoxin gene) can be incorporated into its genome. Toward this goal, Colorado potato beetles were collected from various sites in North America and examined for spiroplasmas. Spiroplasmas were observed in the gut contents of L. decemlineata adults collected in Canada (Alberta and Quebec) and the United States (Arizona, Maine, Maryland, Massachusetts, Michigan, Minnesota, New Jersey, New Mexico, New York, North Carolina, Utah, and Washington) and from L. texana Schaeffer adults collected in Texas. None were naturally associated with adults of the related species, Doryphora quadrasignata Germar, collected in Brazil. Seven isolates adapted to insect cell-free media are now available for molecular studies.

Recovery of D&C Red No. 28 from Potato Leaves

D&C Red No. 28 is a photoactive red dye that is insecticidal for a number of insect species. Unlike contact insecticides, D&C Red No. 28 must be consumed to be effective. Therefore, the red dye must adhere to leaves on which the insect feeds. During a field test of insecticidal activity of the red dye against the Colorado potato beetle (Leptinotarsa decimlineata L.), we measured the recovery of the red dye from potato leaves treated at rates of 70, 210, and 350 g per ha. When the dye was applied alone, we were able to recover over 91% of the red dye at 6 h post treatment and over 30% at one day. At 2 days post treatment, the limit of detection was reached (5 ng D&C Red No. 28/cm2 leaf). In field studies, PEG 200 which improves dispersal, also improved adherence of red dye to leaves. In the laboratory, adjuvants such as PEG 200, Tween 80, and Gelva® also improved red dye adherence to leaves.

The Effect of Simulated Solar Radiation on Western Corn Rootworm (Coleoptera: Chrysomelidae) Adults Fed D & C Red # 28, a Photoactive Xanthene Dye

Western corn rootworm, Diabrotica virgifera virgifera LeConte, adults were fed a bitter Hawkesbury watermelon juice bait containing varying concentrations (0.00075–0.1%) of D & C Red # 28, a photoactive xanthene dye. Using a tabletop sunlight exposure system, the insects were irradiated at light intensities of 250–500 W/m2. At 500 W/m2 and 30 min exposure, a median lethal concentration (LC50) was obtained at a dye concentration of 0.00364%. At a dye concentration of 0.75%, the median lethal time (LT50) ranged from 24 min at 250 W/m2, to 15 min at 500 W/m2.