PRELIMINARY RESULTS CONCERNING TESTING OF THE NEW ACTIVE INGREDIENTS USED LIKE MAIZE SEED TREATMENT FOR CONTROLLING OF THE TANYMECUS DILATICOLLIS GYLL IN LABORATORY CONDITIONS, AT NARDI FUNDULEA
Maize leaf weevil (Tanymecus dilaticollis Gyll) is an economically important pest of the maize crop in south and south-east of the Romania (Cristea et al., 2004). Recent data from literature suggest that higher attack of this pest occur in south-west of the country too and some counties from Moldova region (Popov et al., 2003, 2005, 2007). Same author mention that every year, 1.000.000 ha with maize from the favorable areas are affected by the insect attack. T. dilaticollis is dangerous when maize plants are in first vegetation stages, between plant emergence and four leaf stage (Paulian, 1972). In some cases,maize plants can be destroyed because of the insect attack before plants arrive at soil surface (Barbulescu et al., 2001). At a density between 25 and 30 insects/m2, average yield losses were 34 % (Paulian, 1979). In last decades, several studies from Romania and other countries from South-East of Europe make in evidence that seed treatment is one of the most effective method for protect maize young plants against pests attack, such as T. dilaticollis (Voinescu, 1985; Barbulescu et al., 2001; Krusteva et al., 2006; Keszthelyiet al., 2008; Popov et Barbulescu, 2007; Čamprag, 2011, Trotus et al., 2011). From middle of the years '90 it has tested insecticides from neonicotinoid class for maize seeds treatment against main pests of this crop, especially when plants are in first vegetation stages (Popov et Barbulescu, 2007). Higher effectiveness of these active ingredients was mentioned in different communications (Barbulescu et al., 2001; Popov, 2002; Vasilescu et al., 2005). As result of EU directive 485/2015, from 1 December the use of neonicotinoidinsecticides for seed treatment of the spring crops, including maize, was restricted for two years (Official Journal of the European Union, 2013). After this directive no insecticides remain available for maize seed treatment against T. dilaticollis in Romania. Although it has obtained temporary authorizations for use of the neonicotinoid insecticides like seed treatment at maze crop in spring period, both, in 2014 and 2015, it is necessary to testing new insecticides for evaluate there effectiveness for controlling of the maize leaf weevil. These types of assessments were organized in field conditions, in spring period (Paulian 1972; Voinescu 1985; Barbulescu, 2001; Vasilescu, 2005). However climatic conditions from spring were variable from one year to another. In years with reduced rainfall level in the spring, the attack of T. dilaticollis on maize untreated plants was maximum or almost maximum, while in years with higher rainfall level the attack of this pest on maize untreated plants was lower (Popov et al., 2006). At NARDI Fundulea, Paulian (1972) develop a laboratory method for evaluate effectiveness of seed treatments, where maize emerged plants are placed in conditions of high attack pressure. Barbulescu A. et al. (2001) tested the efficacy of the maize and sunflower seeds treatment with neonicotinoid insecticides in laboratory conditions, using a pest density from four to seven adult insects per plant. In Hungary, Keszthelyi et al. (2008) study effectiveness of both, seed and soil treatments, on three soils type, using isolators, previously sown with corn. In Bulgaria, Draganova S. (2012) testing effectiveness of some Beauveria bassiana isolates for biological control of T. dilaticollis adults in laboratory conditions. The aim of the authors collective is testing different insecticides used like seed treatments, both in laboratory and field conditions, for find alternative at the neonicotinoids treatment in eventuality of permanent ban of these substances in EU. In this paper are presented preliminary results of testing seven active ingredients from three different insecticide classes (pyrethroids, neonicotinoids and ryanoids), in laboratory conditions, using pest high pressure.