Huixin Fei

Evaluation of Vetiver Oil and Seven Insect-Active Essential Oils Against the Formosan Subterranean Termite

Repellency and toxicity of 8 essential oils (vetiver grass, cassia leaf, clove bud, cedarwood, Eucalyptus globules,Eucalyptus citrodora, lemongrass and geranium) were evaluated against the Formosan subterranean termite, Coptotermes formosanus Shiraki. Vetiver oil proved the most effective repellent because of its long-lasting activity. Clove bud was the most toxic, killing 100% of termites in 2 days at 50 μg/cm2. The tunneling response of termites to vetiver oil also was examined. Vetiver oil decreased termite tunneling activity at concentrations as low as 5 μg/g sand. Tunneling and paper consumption were not observed when vetiver oil concentrations were higher than 25 μg/g sand. Bioactivity of the 8 oils against termites and chemical volatility were inversely associated. Listed in decreasing order of volatility, the major constituents of the 8 oils were: eucalyptol, citronellal, citral, citronellol, cinnamaldehyde, eugenol, thujopsene, and both α- and β- vetivone. Vetiver oil is a promising novel termiticide with reduced environmental impact for use against subterranean termites.

Formosan Subterranean Termite (Isoptera: Rhinotermitidae) Wood Consumption and Worker Survival as Affected by Temperature and Soldier Proportion

Abstract The effect of temperature and soldier proportion on worker survival, soldier production, and wood consumption of the Formosan subterranean termite, Coptotermes formosanus Shiraki, was evaluated in the laboratory with termites from a single colony. Soldier production was influenced by temperature and the initial proportion of soldiers. On average, termites had a significantly higher survival rate when the initial soldier proportion was <20%. Soldier caste development was at its highest at 30°C, and when treatment started with no soldiers in the colony. Termite survival was significantly higher at 30°C than at 25 and 33°C after 12 d of testing. There was a significant interaction of temperature and soldier proportion on termite survival after 36 d. C. formosanus could support higher proportions of soldiers with an increase in temperature. There was no significant decrease in survival rates with increasing numbers of soldiers at 25 and 33°C. At 60 d, survival at 20 and 25°C declined significantly when soldier proportions exceeded 20%. At 30 and 33°C, termite survival did not decline significantly when soldier proportions increased from 20 to 30% (30°C) or 40% (33°C). Consumption rates increased significantly with rising temperature up to 30°C. Consumption rates tended to increase as soldier proportion increased. There was no significant interaction between temperature and soldier proportion on wood consumption rate.

Effects of Temperature, Directional Aspects, Light Conditions, and Termite Species on Subterranean Termite Activity (Isoptera: Rhinotermitidae)

Abstract Subterranean termite activity was investigated using field monitoring stations placed around 16 public schools in the triparish New Orleans metropolitan area of Louisiana. With the exception of one school, monitoring stations revealed the presence of Formosan subterranean termites. Native subterranean termites were found in six of the schools. The number of attacked monitoring stations varied significantly with light conditions at different directional aspects and termite species. For example, >50% of first-time attacked monitors by subterranean termites were at east with shade, north with shade, and south with shade placements. Formosan subterranean termites attacked a higher percentage of monitoring stations that were located in east with direct sun, east with shade, and north with direct sun. Native subterranean termites attacked a higher percentage of monitoring stations placed on south with direct sun, south with shade, and north with shade locations. Directional aspects at attacked monitoring stations by termites and corresponding average temperature at a depth of 10.2 cm from the foundation were not significantly correlated. Soil temperature readings 10.2 cm from the foundation did significantly affect seasonal foraging activity of subterranean termites.

Increased Search Tunnel Formation by Coptotermes formosanus Shiraki (Isoptera: Rhinotermitidae) in 2-Phenoxyethanol Treated Sand

Termites follow chemical and physical gradients in their search for food. In laboratory bioassays, search tunnel formation of Coptotermes formosanus Shiraki was examined in response to different 2-phenoxyethanol concentrations in sand. 2-phenoxyethanol significantly increased the total tunnel network length by termites. At a concentration of 0.082%, but not 0.164%, it also significantly increased daily search activity by C. formosanus. After aging the treated sand for 2 wks, C. formosanus continued to show a significant increase in the search tunnel length in 0.082% 2-phenoxyethanol treatments. Application of 2-phenoxyethanol, a nonpheromone attractant, to termite infested soil nearby, may increase the search and thus the likelihood for contact with baits and nonrepellent termiticides in the field.

Terpene-lnduced Morphological Changes to Exoskeleton of Formosan Subterranean Termites (Isoptera: Rhinotermitidae): Toxic Effects of cis-nerol

The terpenoid, cis-nerol was found to be highly toxic to the Formosan subterranean termite, Coptotermes formosanus Shiraki. Morphological abnormalities were observed in the exoskeleton including th...