The influence of environmental conditions on the contact toxicity of some insecticide deposits to adult mosquitos, Anopheles stephensi List

Abstract

Investigations have been made on the influence of environmental conditions on the contact toxicity to adult mosquitos (Anopheles stephensi List.) of two kinds of insecticidal deposits of importance in sprayed houses, superficial deposits from wettable powders and insecticides sorbed on dried soils.Increasing the relative humidity from 43 to 80 per cent, during the contact period had no effect on the toxicity of wettable-powder deposits on plywood of dieldrin, Sevin and O-methyl O-(2,4,5-trichlorophenyl) ethylphosphoramidothioate. On the other hand, the availability of DDT, dieldrin and 3-isopropylphenyl N-methylearbamate sorbed on dried soils increased considerably as atmospheric humidity increased. The logarithm of the median lethal exposure time was linearly related to atmospheric humidity, and decreased by a factor of 2·8, 2·2 and 2·1 for the carbamate, dieldrin and DDT, respectively, for each 10 per cent, increase in relative humidity. There was also a linear relationship between the logarithm of the water uptake of a given soil and humidity.Temperature affected the action of insecticides during both the contact period and the post-treatment period. Median lethal doses of dieldrin, Sevin and the phosphoramidothioate decreased, and that of DDT increased, as the post-treatment temperature increased from 20 to 30°C. These effects of the post-treatment temperature were also found when treatment was by exposure to residues. When these effects were eliminated it was found that the contact toxicity of superficial deposits on plywood and of insecticides sorbed on dried soils increased as the temperature during the exposure period increased. A simple relationship between median lethal time and exposure temperature was indicated.

The interaction of surface and dust particle size on the pick‐up and grooming behaviour of the German cockroach Blattella germanica

“…Similar results were obtained in studies of the pick up of insecticide by Sitophilus granarius (Gowers & Le Patourel, 1984); and with Anopheles stephensi (Hadaway et al, 1970). Hadaway & Barlow (1963) found that the optimal particle size for transfer of dust particles to mosquitoes from a plywood surface was 20--40/~m. Our results indicate that sizes of 0.5-63/~m on ceramic and plastic surfaces, and of 0.5-7.5 #m on plywood are picked up most efficiently by the German cockroach.…”

“…The particle size of a dust may influence its insecticidal properties in several ways according to the nature of its action on the insect (David & Gardiner, 1950). Small particles may be better able to work their way into interstices between articulated members (intersegmental joints, or between legs and body) (Busvine, 1971) or to penetrate the cuticle (Armstrong et al, 1951;Hadaway & Barlow, 1963). The entry of dust into spiracles is also dependent on dust size, thus Hamilton (1937) found that particles up to 53/~m could enter all the spiracles of a locust and even particles as large as 104 #m could enter large spiracles.…”

Efficacy of ACTELLIC 300 CS, Pirimiphos Methyl, for Indoor Residual Spraying in Areas of High Vector Resistance to Pyrethroids and Carbamates in Zambia

“…In different epidemiological settings, this insecticide provided effective control for longer than 6 mo (Nasir et al 1982, WHO 2007, NЈGuessan et al 2009, NЈGuessan and Rowland 2012. Organophosphates and carbamates rapidily lose effectiveness on porous surfaces such as mud but provide persistent control on less porous substrates (Hadaway and Barlow 1963). ACTELLIC 300 CS showed a longer residual efÞcacy on cement walls compared with mud surfaces against a susceptible Kisumu strain of An.…”

Chemicals, Climate, and Control: Increasing the Effectiveness of Malaria Vector Control Tools by Considering Relevant Temperatures

“…This indicates that malaria mosquitoes may not follow the general temperature-toxicity rules. The second study [19] saw a negative TC for DDT and a positive TC for the organophosphate diazinon when An. stephensi was exposed to insecticide residues between 20 and 30°C.…”