Eficiência de nematoides entomopatogênicos e inseticidas químicos contra Sphenophorus levis e Leucothyreus sp. em cana-de-a？úcar

the sugarcane billbug, sphenophorus levis (coleoptera: dryophthoridae), is an important pest of sugarcane crops in the s？o paulo state, brazil. their larvae damage plants rhizome, causing losses of up to 30 t ha-1 year-1 of sugarcane. in order to evaluate the effectiveness of entomopathogenic nematodes and chemical insecticides against the sugarcane billbug and the scarab beetle leucothyreus sp., three field trials were carried out in brazil. for the first one, 10 treatments were considered: 1) thiametoxan (actara 250wg) 500 g ha-1 of commercial product (c.p.); 2) thiametoxan 1.0 kg ha-1 c.p.; 3) thiametoxan 1.5 kg ha-1 c.p.; 4) steinernema brazilense 108 infective juveniles (ij) ha-1 + thiametoxan 250 g ha-1 c.p.; 5) s. brazilense (108 ij ha-1) + thiametoxan 500 g ha-1 c.p.; 6) heterorhabditis indica (108 ij ha-1) + thiametoxan 250 g ha-1 c.p; 7) h. indica (108 ij ha-1) + thiametoxan 500 g ha-1 c.p.; 8) s. brazilense (108 ij ha-1); 9) h. indica (108 ij ha-1); and 10) control. the second one consisted of five treatments: 1) thiametoxan (actara 250wg) 800 g ha-1 c.p.; 2) fipronil (regente 800wg) 250 g ha-1 c.p.; 3) s. brazilense (108 ij ha-1); 4) s. brazilense (108 ij ha-1) + thiametoxan 200 g ha-1 c.p.; and 5) control. in the third one, all treatments already mentioned for the second trial plus the mixture s. brazilense (108 ij ha-1) + fipronil (regente 800wg) 62.5 g ha-1 c.p. were considered. all treatments with the insecticides and nematodes provided higher sugarcane yield, when compared to their respective controls, which were most damaged by s. levis, but without statistical significance. s. brazilense was more efficient on controlling this pest, if compared to h. indica, but without statistical significance. s. brazilense provided a 50% control of leucothyreus sp. larvae, meanwhile the best treatments against this scarab were the mixtures of this nematode with fipronil (78%) and thiametoxan (83%).