A. BÂRBULESCU, I. VOINESCU, D. SADAGORSCHI, A. PENESCU, C. POPOV, S. VASILESCU
Research Institute for Cereals and Industrial Crops, 8264 Fundulea, Nicolae Titulescu str., no. 1, District Calarasi, Romania, e-mail: fundulea@,ns.ricic.ro

Maize leaf weevil Tanymecus dilaticollis is the most dangerous soil pest of maize and sunflower, the first ranged spring field crops in Romania. This pest is able to induce high yield losses and even compromise crops. The seed dressing with carbofuran products provide satisfactory protection of these crops against the pest. This method replaced the use of organochlorine insecticides applied, for many years, as dusts, which contributed to environmental pollution and the destruction of useful fauna. However, the very high toxicity of carbofuran to man and animals, as well as a tendency for T. dilaticollis to develop tolerance to this compound, necessitated the development of seed treatments using less toxic products, such as Cruiser 350 FS.
The experiments were done in the laboratory, under artificial infestation, and in the field, in plots cropped successively over the last three years with maize, thus favouring pest reproduction. The efficacy of the Cruiser 350 FS, a thiamethoxam - based product, was compared with a carbofuran - based product, as a standard. Evalution of chemicals was done in relation to values of attack intensity, and the percentage of plants escaping pest attack for field trials only. The behaviour of maize and sunflower hybrids to Cruiser 350 FS was examined in several localities under field conditions. The percentage of emerged plants was assessed in treated and untreated plots.
Trials performed revealed very good results obtained by the use of Cruiser 350 FS, providing satisfactory protection of maize and sunflower crops against T. dilaticollis. As differences between the rates are not high, that means from economic standpoint the doses of 315 g a.i./100 kg seed for maize, and 350 g a.i./100 kg seed for sunflower are most interesting. Being a product with much lower toxicity than older alternatives it is possible for unauthorized persons to apply this seed treatment, which is not permitted when using carbofuran. All maize and sunflower hybrids trialled showed good tolerance to the Cruiser 350 FS, at the experimental rates used.