What biological substances are larvicides typically derived from?

Larvicides are typically derived from specific biological substances that target the larvae of mosquitoes to prevent them from maturing into adults. Bacillus thuringiensis israelensis (Bti) is a naturally occurring soil bacterium that produces toxins harmful to certain insect larvae, including those of mosquitoes. This makes it an effective and eco-friendly option for controlling mosquito populations. Spinosad, which is derived from the fermentation of naturally occurring soil bacteria, also acts on the nervous system of insects, providing another biological method for larval control.

The other substances listed do not effectively target mosquito larvae in the same manner. Chlorine and sodium hydroxide are chemical compounds that are more commonly associated with water treatment and sanitation rather than biological pest control. Petroleum-based oils and solvents can serve as pesticides but are not derived from biological sources and may have environmental concerns associated with their use. Organic compost and fertilizers do improve soil quality but do not have any specific larvicidal properties. Thus, the combination of Bti and spinosad represents the correct choice for biological larvicides due to their specific effectiveness against mosquito larvae.