Toxicity of four kind plant extracts (Ageratum conyzoides L., Barringtonia asiatica (L.) Kurz., Melia azedarach L., Tephrosia vogelii Hook F.) against brown planthopper (Nilaparvata lugens STAL.) - Febritami, Giannisa (Departemen Hama dan Penyakit Tumbuhan Fakultas Pertanian Universitas Padjadjaran, 2018)