Insecticidal activity of Tagetes sp. on Sitophilus zeamais Mots

The world population growth has led to increased food production demand (Menezes, 2005; Corrêa and Salgado, 2011), resulting in a green revolution, dating from the 1960s, which led to agriculture to be characterized as extensive monocultures and great use of synthetic fertilizers and agrotoxics, the latter being mainly composed of synthetic herbicides and insecticides (Menezes, 2005). 

In relation to pesticides, several properties must be associated with the activity, such as effectiveness at low concentrations, no toxicity front of mammals and higher animals, easily obtainable, handling and application, economic feasibility and not be accumulated in human adipose tissue and also selective (Addor, 1994; Viegas Júnior, 2003). Within the insecticides classification are also included substances that repel and attract insects (Viegas Júnior, 2003). 

Insecticides are in the second position in the trading market of agrotoxics in Brazil, with 25%, behind herbicides with 48% (Agrow, 2007; Ibama, 2009; Tavella et al., 2011). Insects are the major cause of losses in crops, especially grains and seeds, as they reduce their nutritional and commercial values, these attacks can occur before, during and after crop (Almeida et al., 2005). To date Brazil has its economy based on primary sector production, occupying a prominent position on the world supply of cereals, fruits and other products of plant origin (Viegas Júnior, 2003).

 The maize weevil Sitophilus zeamais Mots., 1855 (Coleoptera: Curculionidae), is a cosmopolitan insect, of cross-infestation, means that the insect attack seeds in the field and also in warehouses (Almeida et al., 1999; Lorini et al., 2010; Antunes et al., 2011), have high reproductive potential, is considered an internal primary pest (Lorini et al., 2010; Antunes et al., 2011), causing serious economic losses (Restello et al., 2009, Antunes et al., 2011), because it has many hosts, such as wheat, corn, rice, barley and oats. Corn is one of the most important products of the agricultural sector in Brazil (Embrapa, 2010), is also considered the culture more attacked by S. zeamais, which in turn is reported as the most widespread and destructive species of cereals held in the world (Capps et al., 2010; Almeida et al., 2012).

 Today we know that the frequent and indiscriminate use of chemicals, which are not always effective often cause the presence of high levels of toxic residues in food, of biological unbalance, environmental contamination, Intoxication humans and animals (Almeida et al. 1999; Lima et al., 2008; Marcomini et al, 2009; Queiroga et al, 2012), resurgence of pests and Page | 31 International Journal of Environmental & Agriculture Research (IJOEAR) ISSN:[2454-1850] [Vol-2, Issue-4, April- 2016] strains of resistant insects (Dequech et al, 2008; Almeida et al, 2012), among other direct and indirect effects (Lima et al, 2008). It is also known that the use of plant extracts, as an alternative insecticide, is a way to provide a control without triggering the problems caused by chemical synthetic insecticides (Almeida et al., 1999).

 An alternative to attenuate these problems is to use allelochemicals extracted from plant (Dequech et al., 2008). These factors justify the studies to identify management practices that reduce the use of synthetic products such as cultural practices based on allelopathy (Balbinot-Junior, 2004). The genus Tagetes, family Asteraceae , is used as an alternative for the control of pests and diseases (Salinas-Sánchez et al., 2012), and due to the chemical composition of their secondary metabolites, their biology activity have provided the development of new drugs and insecticides, among others (Verdi et al., 2005; Duque, 2006); is native to Mexico and Central America (Marotti et al., 2004; Peres, 2007; Santos, 2013), has therapeutic properties that have been recognized since the time of the Aztecs, being used to combat various diseases (Rondón et al., 2006; Jain et al, 2012; Tonuci et al, 2012). Among secondary metabolites found in the species Tagetes are: alilanisol, anetol, limonene, methyl eugenol, and β-karyophyllene that are have toxic to insects, mites, nematodes, bacteria, fungi, and viruses. Such compounds have been reported to be present in Tagetes essential oil, and they belong to certain groups of hydrocarbons, alcohols, ethers, aldehydes, ketones, esters, carotenoids (Rondón et al., 2006; Jain et al., 2012; Salinas-Sánchez et al., 2012; Santos, 2013), flavonoids, terpenes (Santos, 2013) and thiophenes (Duque, 2006; Dasgupta et al., 2012). The species Tagetes erecta L. e Tagetes patula L have antioxidant properties, larvicidal, fungicidal (Lopes et al, 2009; Martinez et al, 2009; Restello et al., 2009; Tonuci et al, 2012;) antimicrobial, nematicide, insecticide (Restello et al., 2009; Barboza et al., 2010). 

Considering these perspectives, the aim of the study was evaluating the effects of hydroethanolic and ethanol extracts of Tagetes erecta L. and Tagetes patula L. (Asteraceae), on Sitophilus zeamais.