Effects of White Mulberry (Morus alba) Heartwood Extract Against Reticulitermes flavipes (Blattodea: Rhinotermitidae).

Heartwood extract from white mulberry (Morus alba L.) (Rosales: Moraceae) were investigated for antitermitic activity against Reticulitermes flavipes (Kollar) (Blattodea: Rhinotermitidae) in laboratory experiments. An ethanol:toluene (2:1) solvent system was used to remove extract from heartwood shavings. A concentration-dependent feeding response and mortality were observed for termites exposed to a concentration series range of 1.25 to 10 mg/ml of extract based on their dry weight. Results showed that maximum termite mortality occurred at 10 mg/ml. Based on the concentration series data, LC50 was calculated at 1.71 mg/ml. In filter paper feeding and repellency assays, extract significantly decreased the total number of gut protozoa compared with untreated and solvent controls. After feeding on filter paper treated at 10 mg/ml for 2 wk, protozoan populations were reduced by >55%. In choice and no-choice tests with mulberry heartwood, greater wood loss from termite feeding was found on solvent extracted blocks compared with nonextracted. Complete (100%) mortality was observed after feeding on nonextracted blocks compared with extracted blocks. Heartwood extract from white mulberry imparted resistance to vacuum pressure treated, nondurable southern pine and cottonwood. At every concentration tested, 100% mortality was observed after feeding on extract-treated southern pine or cottonwood. GC-MS analysis of extract showed high levels of the phenol compound, resorcinol. Results indicated that heartwood extract from white mulberry have antitermitic properties and might be potentially valuable in the development of environmentally benign termiticides.

Ultrasound pretreatment of elemental iron: kinetic studies of dehalogenation reaction enhancement and surface effects.

This work presents data showing the kinetic improvement afforded by ultrasound pretreatment and illustrates the physical and chemical changes that take place at the iron surface. First-order rate constants improved as much as 78% with 2h of ultrasound pretreatment. Scanning electron microscopy (SEM) and surface area analysis were used for confirmation of the physical changes that take place after ultrasound was used on iron surfaces exposed to a variety of conditions. X-ray photoelectron spectroscopy was used to determine chemical surface characteristics before and after ultrasound use. SEM and surface area analysis showed that ultrasound use clears the iron surface of debris increasing the surface area up to 169%. In addition, exposure to ultrasound alters ratios of surface species, such as adventitious carbon to carbonyl carbon and iron to oxygen, and removed hydroxides thus making the iron more reactive to reductive dehalogenation.

Induction of polygalacturonase and the formation of oxalic acid by pectin in brown-rot fungi.

Extracellular polygalacturonase (PG) production was estimated in vitro, using liquid cultures of three species of brown-rot decay fungi (Postia placenta, Gloeophyllum trabeum and Serpula incrassata), by cup-plate assay, assay of reducing sugars, and decrease in viscosity. Although all three experimental assays demonstrated that PG was induced by pectin in all three fungi, decrease in viscosity gave the best correlation with decay capacity in soil block tests. PG activity, determined as an increase in reducing sugar activity, was greatest in G. trabeum and weakest in S. incrassata. The optimum pH for PG activity was between pH 2.5 and 4.5. Oxalic acid production was also enhanced by pectin and functioned synergistically with PG activity. We conclude that these fungi produce PG that is best induced by pectin and that PG activity exceeds production of xylanase and endoglucanase activity in vitro. Polygalacturonase is likely to act synergistically with oxalic acid to solubilize and hydrolyse the pectin in pit membranes and middle lamellae. Thus, production of PG and oxalic acid should facilitate early spread of hyphae and enhance the lateral flow of wood-decay enzymes and agents into adjacent tracheids and the wood cell wall, thus initiating the diffuse decay caused by brown-rot fungi.

Dyed particle capture immunoassay for detection of incipient brown-rot decay.

An immunological method for detecting incipient fungal decay in wood is described. Monoclonal antibody to extracellular beta-1,4-xylanase of the brown-rot fungus Postia placenta was immobilized in a defined capture zone to a strip of hydrophobic polyester cloth. Polyclonal-labeled latex particles were applied near one end of the polyester assay substrate. The resulting test strip was dipped into extracts from wood blocks inoculated with various wood decay fungi. Extracts flowed laterally through the antibody-labeled latex particles and the capture zone. When antigen was present in the extract, the antigen was complexed by the monoclonal and labeled-polyclonal antibodies to form an observable particle complex in the zone of capture. Wood samples were tested at various stages of decay and correlated with wood weight loss. Incipient brown-rot decay was detected with the particle capture immunoassay at less than 2 percent wood weight loss.

Adaptation of the Nelson-Somogyi reducing-sugar assay to a microassay using microtiter plates.

The Nelson-Somogyi assay for reducing sugars was adapted to microtiter plates. The primary advantages of this modified assay are (i) smaller sample and reagent volumes, (ii) elimination of boiling and filtration steps, (iii) automated measurement with a dual-wavelength scanning TLC densitometer, (iv) increased range and reproducibility, and (v) automated colorimetric readings by reflectance rather than absorbance.