Wikipedia:Reference desk/Archives/Science/2024 May 10

= May 10 =

Insect repellent
Do all pyrethrin analogs have broad-spectrum insect repellent properties in less-than-lethal concentrations? 2601:646:8082:BA0:CD56:E11E:9CF:F450 (talk) 01:56, 10 May 2024 (UTC)
 * It says here that "Before the emergence of resistance, an early hut trial in The Gambia concluded that permethrin was the most repellent pyrethroid, followed by λ-cyhalothrin, deltamethrin, and lastly cypermethrin". This suggests that there must be some in the list of 29 examples in the pyrethroid article that are much worse repellents. I would guess that the stronger the odor, the better the repellent effect. Abductive  (reasoning) 08:38, 10 May 2024 (UTC)
 * Pyrethroids were designed to kill insects and are used, for example, to control malaria-carrying mosquitoes by treating bed-nets. In this and other agricultural applications, repellence is an unwanted property particularly if the non-lethal effect allows insect populations to build up resistance. There are, of course, compounds designed to act only as insect repellents, of which the best known are probably DEET and citronellal. Mike Turnbull (talk) 10:46, 10 May 2024 (UTC)
 * Thanks! So, not all of them, but many of the common ones -- which is great for me (they're painting my front door today, so I have to enforce a no-fly zone outside it :-  And yes, last time I've personally witnessed the repellent effect of 200 ppm deltamethrin against Papilio multicaudata (or maybe it was a large P. rutulus, but my money is on the former) and P. eurymedon, as well as multiple Apocrita species!  (The repellent effect, indeed, is what I'm looking for here -- I don't care if the bugs survive or die, I just don't want them to fly into the house or get anywhere near me!) 2601:646:8082:BA0:59E2:271:87C3:F3E (talk) 14:07, 10 May 2024 (UTC)
 * Also, one of the two cans I used today had a mixture of prallethrin and cyfluthrin which was specifically formulated as an insect repellent, so we can add these two to the list as well -- although, from personal observation, their repellent effect was actually less than that of deltamethrin! 2601:646:8082:BA0:448D:8CB2:2FBC:B6C7 (talk) 00:12, 11 May 2024 (UTC)