Which of the following are larvicides used in mosquito control?

• A. Permethrin and malathion
• B. ULV fogging for adults
• C. Bacillus thuringiensis israelensis and mosquitocidal oils
• D. Bacillus thuringiensis israelensis and methoprene

Answer: (D)

In mosquito control, targeting the larval stage in standing water is a key strategy, since it prevents many mosquitoes from reaching the biting adult stage. Bacillus thuringiensis israelensis (Bti) is a bacterial product that acts as a larvicide: it must be ingested by mosquito larvae and then releases toxins that kill them, providing a specific and effective kill for larvae in treated waters. Methoprene, on the other hand, is an insect growth regulator. It isn’t about killing larvae quickly; instead it mimics juvenile hormone and prevents larvae from properly developing into adults, reducing the number of mosquitoes that emerge over time.

Using these two together covers both immediate larval kill and disruption of development, giving broader and longer-lasting suppression of the mosquito population. The other options aren’t as aligned with larval control: permethrin and malathion are typically used against adults or as broad-contact insecticides; ULV fogging targets flying adults rather than larvae; and while mosquitocidal oils can be used in some larval-control contexts, the common, tested pairing emphasized here is Bti with methoprene because they operate by different larval-control mechanisms.