Screening of Chinese medicinal herbs for bioactivity against Sitophilus zeamais Motschulsky and Tribolium castaneum (Herbst)

Abstract

Extracts of 40 species of Chinese medicinal herb from 32 different botanical families were screened for contact, fumigant and feeding-deterrent activities against the two stored-grain insects Sitophilus zeamais and Tribolium castaneum. Thirty Chinese medicinal herbs exhibited insecticidal or feeding-deterrent activities against the two species of insects. Extracts of Artemisia argyi, Dictamnus dasycarpus, Evodia rutaecarpa, Litsea cubeba, Narcissus tazetta var. chinensis, Polygonum aviculare, Rhododendron molle, Sophora flavescens, Stemona sessilifolia, Tripterygium wilfordii, and Torreya grandis were most active.

Introduction

There is a long history of the use of Chinese medicinal herbs against pests in China. Since time immemorial, people have known how to use plants against insects (Yang and Tang, 1988). Even today, in the rural areas of China, farmers are still using the leaves of Chinaberry (Melia toosendan Siebold et Zuccarini), dried flowers of yellow azalea (Rhododendron molle G. Don) and the grass Euphorbia helioscopia L. to control the larvae of flies in manure pits. These practices are labor intensive, but often economically and ecologically sound. They do not require sophisticated technology. A good botanical insecticide, toosendanin, was derived from the bark of Chinaberry and is used against a broad spectrum of fruit and vegetable pests in China (Zhang et al., 1992). Yang and Tang (1988) reviewed and listed plant species with insecticidal properties used in China. Out of 267 plant species listed, more than 100 are Chinese medicinal plants. However, very few systematic studies have been conducted to evaluate Chinese medicinal herbs against insects (Chiu, 1985, Chiu, 1989). In addition to plants collected from the wild, traditional medicinal plants provide another good source for screening. The advantage of using traditional medicinal herbs is that they are readily available in herb shops and they have been used extensively for medicinal purposes, implying their low/non-toxicity to humans. For example, Park et al. (1997) screened the methanol extracts from 77 oriental medicinal plant species in 42 families for their larvicidal and antifeedant activities against gipsy moth larvae (Lymantria dispar L.), the black-tipped sawfly (Acantholyda posticalis Matsumura), the fall webworm (Hyphantria cunea Drury), and the pine caterpillar (Dendrolimus spectabilis Butler). Sener et al. (1998) also screened some Turkish medicinal plants for their insecticidal activities against milkweed bugs (Oncopeltus fasciatus Dallas) and mosquitoes (Aedes aegypti L.), while Mackeen et al. (2000) screened 40 Malaysian medicinal plants belonging to 25 families for their brine shrimp toxicity.

The present study was initiated to screen some Chinese medicinal herbs for bioactivity against two stored-grain insects, the maize weevil Sitophilus zeamais Motschulsky and the rust-red flour beetle Tribolium castaneum (Herbst).