What is the major drawback of using insect growth regulators?

Insect growth regulators (IGRs) are designed to disrupt the normal development processes of insects, primarily targeting immature stages such as larvae or nymphs. The major drawback of IGRs is that they are not effective against adult insects. This is significant because many pest populations may consist of both adults and immature stages, and if the adult insects remain unaffected, they can continue to reproduce and infest the area. This limitation means that while IGRs can help control the growth of an insect population by preventing the development of larvae into adults, they won't reduce the number of adult pests currently present, allowing the cycle of infestation to continue.

Understanding this limitation is crucial for implementing an effective pest management strategy. The other choices focus on properties that do not accurately represent the primary issues related to IGRs. Rather than being extremely volatile or harmful to humans, IGRs tend to be relatively safe to non-target species, including humans, when used properly. Additionally, they do indeed work effectively against larvae, which is part of what makes them useful in integrated pest management.