Botanical Insecticides for Controlling Agricultural Pests:Piperamides and the Colorado Potato Beetle Leptinotarsa decemlineata Say (Coleoptera:Chrysomelidae)

摘要

The efficacy of extracts from jtwo Piperaceae species,Piper nigrum L.and P.tuberculatum Jacq.were evaluated using larvae and adults of the Colorado Potato BGeetle Leptinotarsa decemlineata (Say).Young larvae and neonates were the most susceptible;a 24-h LD_50 of 0.064% extract of P.tuberculatum was determined for 4-day-old larvae,while 0.05% extract of P.nigrum reduced larval survival up to 70% within one week aftger treatment of potato Solanum tuberosum L.(Solanaceae) plants.When an insecticide resistant strain of L.decemlineata larvae was tested with the P.tuber5culatum extract,there wad less than a 2-fold tolerance ratio compared to the 22-fold tolerance ratio to cypermethrin,a pyrethroid.Older larvae,prepupal stge and adults,were less sensitive to the P.nigrum extracts;the 24-h LD_50 was 0.5% (95% C.I.=0.36,0.65).However,the same concentraton was equally effective under field conditions.In the greenhouse,P.nigrum at 0.5% was as effective at reducing adult L.decemlineata feeding as combinations with 2 separate botanical mixtures,garlic and lemon grass oil.Under field conditions,the residual activity of the P.nigrum extracts was less than 3 h.When adult L.decemlineata were placed on treated plants exposed to full sunlight for 0,1.5,and 3 h,heaf damage progressively ncreased as the main active compound,pipertine,was found to degrade by 80% after 3 h.An in vitro polysubstrate monoxygenase (PSMO) enzyme assay,using the substrate methoxyresorufin O-demethylation (MROD),determined that the principal P.nigrum active compound,piperine,is responsible for inhibition of that specific enzyme.The results suggest that Piper extracts could be used effectively as contact botanical insect control agents to protect potato plats from dveloping L.decemlineata larvae at concentrations less than 0.1%.There is also opotential for piper extracts to control insecticide resistant populations in conjunction with other integrated pest management (IPM) strategies used in conventional and organic agriculture.