The invention relates to an
insect-resistant agent and a prevention and control method for
plant pests, and relates to the technical field of
plant insect-resistant agents. Wherein the
insect-resistant agent comprises a
semen cuscutae extract; the preparation method of the
semen cuscutae extract comprises the following steps: carrying out first extraction treatment on dried
semen cuscutae
powder by adopting a first
solvent, and removing an extracting solution to obtain
powder subjected to the first extraction treatment; the first
solvent is an aliphatic
alkane solvent; carrying out second extraction treatment on the
powder subjected to the first extraction treatment by adopting a second solvent, and removing an extracting solution to obtain powder subjected to the second extraction treatment; the second solvent is an ester
organic solvent; performing third extraction treatment on the powder subjected to the second extraction treatment by adopting a third solvent, and collecting a third solvent extracting solution; the third solvent is one or more of
ethanol,
methanol and water; and performing solvent removal treatment on the third solvent extracting solution to obtain the semen cuscutae extract. The invention mainly develops an insect-resistant agent which is green, efficient, low in
toxicity and not easy to generate
drug resistance.