Skeletal extension of Acropora formosa at a fringing reef in the Andaman Sea

A growth study of Acropora formosa (Dana) was conducted in situ at a fringing reef in front of Phuket Marine Biological Center, the Andaman Sea, southern Thailand. Monthly extensions of branches tagged with wire were measured in addition to sunshine, rainfall, settlement of sediment, turbidity, salinity, and temperature. The average extension of coral branches was 8 cm in 344 days. Growth was found to be approximately two times faster during the dry northeast monsoon compared with the wet southwest monsoon. Factors which can cause the observed pattern of growth are discussed.Miscellaneous Contributions from PMBC, Thailand, No. 17     

Farm‐scale dispersal of Bactericera cockerelli in potato crops measured using Bt mark‐capture techniques

Natural populations of Bactericera cockerelli (Sulc) (Hemiptera: Triozidae), also known as tomato/potato psyllid, were marked in potato [Solanum tuberosum L. (Solanaceae)] crops using Bacillus thuringiensis Berliner (Bt) to investigate the impact of dispersal on crop infestation and management of potential insecticide resistance in New Zealand. The technique was adapted from previous studies that used conventional spray applications of Bt to mark Phthorimaea operculella (Zeller) (Lepidoptera: Gelechiidae), and identified marked individuals with selective microbiological assays and identification of characteristic crystal inclusions. Initially, marking rates of B. cockerelli were improved by using ultra‐low volume applications of undiluted Bt, but this result was not consistent. Several other pests and natural enemies were also marked. In mark‐capture studies, marked B. cockerelli were captured over 3 days on yellow sticky traps in small trap plots of potatoes at 60, 120, 180, 250, and 350 m from the sprayed crop. Bactericera cockerelli flight activity occurred throughout daylight hours with evidence of bimodal diurnal peaks. Significantly greater numbers of B. cockerelli were captured in downwind traps. The combined dispersal curve derived from two mark‐capture experiments estimated a mean dispersal distance for B. cockerelli of 100 m in 3 days and indicated that 10% of the population dispersed further than ca. 250 m. Over the period of a growing season, this level of dispersal suggests that B. cockerelli can disperse throughout a vegetable‐growing region, with implications for crop infestation and management of potential insecticide resistance.     

Mechanical properties of chitosan/bamboo charcoal composite films made with normal and surface oxidized charcoal

Chitosan/bamboo charcoal composite films were prepared by blending chitosan with either virgin bamboo charcoal or bamboo charcoal modified by nitric acid oxidation to provide more hydrophilic regions on the bamboo charcoal surface. Investigation of the physical properties of these composite films revealed that the tensile strength and Young’s modulus of the chitosan films were enhanced in a dose-dependent manner by the inclusion of modified bamboo charcoal at up to 1% (w/w), whilst the elongation at break was increased by inclusion of modified bamboo charcoal at up to 0.5% (w/w). In contrast, chitosan composites with virgin bamboo charcoal at up to 0.5% or 1.0% (w/w) showed no enhancement of the tensile strength or Young’s modulus, respectively, and both parameters were reduced with higher levels of virgin bamboo charcoal. Oil, and especially water, absorption of the composite films displayed a marked and dose-dependent increase compared to those of the pure chitosan film.