Which of the following are used to control scale pests?

The choice of "All of the above" is correct because all listed options are effective methods for controlling scale pests.

Insecticidal soaps work by disrupting the cell membranes of soft-bodied pests, including scales, leading to their dehydration and eventual death. They are especially effective against pests that are covered with a waxy coating that can be penetrated by the soap.

Horticultural oils are another important tool in managing scale infestations. These oils suffocate pests by blocking their breathing pores, which is particularly effective on scale insects that tend to be immobile and cling to plant surfaces.

Biological control agents, which can include natural predators or parasitoids, provide a more environmentally sustainable option for managing scale pests. These agents can effectively reduce scale populations by preying on or parasitizing them, thus helping to maintain pest control without the use of synthetic chemicals.

Selecting "All of the above" encompasses the comprehensive approach needed for effective pest management, highlighting the versatility and effectiveness of each method in controlling scale pests.