Journal of Agricultural Science; Vol. 6, No. 7; 2014 ISSN 1916-9752 E-ISSN 1916-9760 Published by Canadian Center of Science and Education 194 Insecticide Activity of Weeds to Pests of Stored Product and Crops Juno F. Silva Diniz 1 , Paulo R. da Silva 1 , Marcelo R. dos Reis 1 , Ricardo T. Endo 1 , Rodrigo S. Ramos 2 , Flávio L. Fernandes 1 & Ítalo W. da Silva 1 1 Manejo Integrado de Pragas e de Plantas Daninhas, Universidade Federal de Viçosa - Campus de Rio Paranaíba, Minas Gerais, Brazil 2 Entomologia, Universidade Federal de Viçosa, Viçosa, Minas Gerais, Brazil Correspondence: Flávio Lemes Fernandes, Universidade Federal de Viçosa, Campus de Rio Paranaíba, MG 230, KM 09, 38810-000, Rio Paranaíba, Minas Gerais, Brazil. Tel: 55-34-3855-9364. E-mail: flaviofernandes@ufv.br Received: March 25, 2014 Accepted: May 14, 2014 Online Published: June 15, 2014 doi:10.5539/jas.v6n7p194 URL: http://dx.doi.org/10.5539/jas.v6n7p194 Abstract Farmers from family farming faces serious problems of pest attack, both in their production on the field and in storage. The weed species with insecticidal action were identified through toxicity tests to insects. The species of plants tested were Ageratumm conyzoides, Euphorbia heterophylla, Sida rhombifolia and Sida spinosa and the insects were Leucoptera coffeella, Macrosiphum rosae, Atta sexdens rubropilosa, Solenopsis invicta and Sitophilus zeamais. The aim of this study was to identify weeds with insecticide activity against agricultural pests, extract the active compounds of weeds and perform bioassays with hexane and ethanol extracts of weeds on agricultural pests and stored grain. The plant material was subjected to extraction with ethanol and hexane. The mortality bioassays were conducted in a completely randomized design with four replications in triple factorial design (4 x 5 x 2). The data of mortality were subjected to analysis of variance and the differences among means were compared by Tukey's test (p < 0.05). We detected significant differences between the mortality rates for the different species of plants, insect species and between the types of solvents and also in the interactions between insect species x types of solvents, plant species x types of solvents, plant species x insect species and between plant species x species of insects and types of solvents. In general, the hexane extracts of the plant species A. conyzoides and S. rhombifolia were the most toxic. The most susceptible insects species were L. coffeella, S. invicta and M. rosae. Keywords: bioassays, extracts, insects, solvent 1. Introduction Family farming is responsible for about 40% of Brazilian agricultural production and has a large capacity to generate foreign exchange earnings, employment and income, contributing to maintaining the quality of life of rural populations. Family farming uses a system of ecologically-based production which gathers techniques that aim to reduce dependence on foreign energy and environmental impact, obtaining better quality products, valuing the producer, their social bases, their work, their culture and their territory. One of the main problems faced by farmers of family farming is the attack of pests, both in their production on the field and in storage. Thus, the producers use control practices, being the application of the most widely used organosynthetic insecticides. This method of control raises the cost of production due to the high value of these inputs and can result in ecotoxicological problems such as environmental pollution, poisoning of farmers and food contamination produced. A viable alternative to this situation is the use of botanical insecticides. These compounds have a low cost (and may even be produced by the farmers themselves), low environmental impact and are of low toxicity to humans and non-target organisms (Macías, Castellano, & Molinillo, 2000). The plants have a large diversity of compounds with insecticidal action, acaricidal, fungicidal and bactericidal, which have been used by botanical extracts as commercial products or as a source of molecules for the synthesis of pesticide by industries. Particularly the biodiversity of native plants is high in the Cerrado (Savannah) biome of Brazil, hence, the flora of this area has high potential of substances with insecticidal effects (Barbosa & Fearnside, 2004). Natural products from plants can be used the pattern for the synthesis of synthetic pesticides with desirable features such as greater efficiency, biodegradability and lower toxicity to non-target organisms. Among these