Pesticide avoidance behavior in Anopheles albimanus, a malaria vector in the Americas.

The behavioral responses of 4 populations of Anopheles albimanus females to DDT, permethrin, and deltamethrin were characterized in excito-repellency tests. One test population (ST) from El Salvador has been maintained as a colony for 20 years. A second population (ES) from Guatemala was colonized in 1992. Third and fourth populations consisted of field-caught specimens from Toledo District (TO) of southern Belize in 1994 and Corozal District (CO) of northern Belize, respectively. Females of ES, TO, and CO populations rapidly escaped from direct contact with treated surfaces for each of the 3 insecticides. Similarities in escape responses of insecticide-resistant (ES) versus insecticide-susceptible populations (TO, CO) suggest that there is no relationship between physiological and behavioral responses of An. albimanus populations to DDT, permethrin, and deltamethrin. Females from all but the ST colony escaped in greater numbers from chambers without direct contact with treated surfaces than from control chambers (P < 0.05). Few females from the ST colony escaped from test chambers, regardless of which insecticide was used or whether contact was allowed, indicating that the ST colony has lost its capability to respond to insecticides. Repellent responses were significant; but they were not pronounced in 30-min exposures, and they were very pronounced in 4-h exposures. We conclude that irritant and repellent responses of malaria vectors to insecticides are important components of malaria control operations.

Field evaluation of two formulations of cyfluthrin for control of Ixodes dammini and Amblyomma americanum (Acari: Ixodidae).

Liquid or granular cyfluthrin was applied in the spring and fall to different test plots at a rate of 0.41 (AI) kg/ha to control Ixodes dammini Spielman, Clifford, Piesman & Corwin and Amblyomma americanum (L.). Spring application of liquid cyfluthrin showed the most significant decreases of both species. I. dammini nymphs were reduced 97% at 10 d, 100% at 2 mo, and 100% at 1 yr; and A. americanum adults and nymphs were reduced 91-93% at 10 d and 100% at 2 mo posttreatment. Granular cyfluthrin applied in the spring gave 97 and 87% control of nymphal I. dammini 10 d and 2 mo posttreatment, respectively.

New state record for Culiseta impatiens in Maryland.

Culiseta impatiens is reported for the first time from Maryland. Collections from the southwestern border of Fort George G. Meade extend the range of this species over 400 km farther south than previous records. Multiple collections from 4 separate traps during 2 years indicate a population of Cs. impatiens is probably established in the collection area.

Micrometeorologic factors affecting field host-seeking activity of adult Dermacentor variabilis (Acari: Ixodidae).

Fifteen micrometeorologic or microenvironmental parameters, including temperature, moisture, wind, and solar radiation, were repeatedly measured at 1 m and 2.5 cm aboveground, in the litter layer, and in the soil concurrently with drag samples of questing American dog tick, Dermacentor variabilis (Say), in five plots (1 by 10 m) in Delaware County, Ohio. Multivariate statistical analyses of the resultant data showed that ambient temperature was the best general predictor of adult tick host seeking under the observed ranges of the observed parameters. Multivariate procedures included forward stepwise multiple regressions and principal components analyses. Solar radiation was covariant with ambient temperature but was much less predictive. A suppression of questing activity with increased ambient temperature was evident at the highest observed temperatures, implying an upper temperature limit for this activity.

Reduction of the Amblyomma americanum (Acari: Ixodidae) population at Fort A.P. Hill, Virginia, by aerial application of diazinon granules: correlation of percentage control with received dose.

Habitat (280 ha) of lone star tick, Amblyomma americanum (L.), was aerially treated with 14% diazinon granules. Concentration of acaricide reaching the forest floor ranged from 0.02 to 1.25 kg (AI)/ha. Greater than 85% control was achieved at study plots receiving the highest dose. A positive correlation was shown between dose received at the forest floor and percentage of control of adults (r = 0.91) and nymphs (r = 0.86).

Insect repellent jacket tests against biting midges (diptera: Culicoides) in Panama.

Light-weight net jackets treated with N,N-diethyl-m-toluamide (deet) were field-tested in Panama against five species of biting midges, principally Culicoides furens (Poey) and C. barbosai Wirth and Blanton. The deet-treated jacket provided 87-93% protection. Time of day as well as season appeared to influence the proportionate numbers of species collected. The mean coefficient of protection was slightly lower during morning tests when C. barbosai was most abundant and higher during evening tests when C. furens was most abundant.