Because the intensity of infestation is not suficient to compare sugarcane cultivar in relatiori to the damage caused by borer-rot complex, a r.ew index to evaluate these damage is pra posed. This index, named intensity of damage, is obtained bv the product between the intensity of infestatiori and the volu metric damage caused by the borer-rot cornplex, wich is determined throuqh the relaticnship between volume of the damage re gion and total volume of the internode. RESUMOConsiderando-se que a intensidade de infestação é insuficiente para comparar cultivares de cana-de-açúcar em relação aos danos provocados pelo complexo broca-podrid8es, propõe-se, no presente trabalho, um novo índice para avaliar estes danos. Este índice, denominado intensidade de dano, é obtido pelo produto entre a intensidade de infestação e o índice volumétrico de dano provocado pelo complexo broca-podridões, Recebido em 3/5/90 1 Complexo formado pela broca Diu(roea sacc/?ora/is (Fabr. , 1794) e pelos fungos Col/etotrichum fo/cotum Went e Fusoriurn rnoni/iforrne Sheldon.2 Pesquisa realizada com apoio linanceiro da FINEP. Parte da tese apressa tada pelo primeiro autor, como um dos requisitos ao Concurso de Livre-Doc&ncia pela ESALQ-USP.

Evaluation of the dimensions of the plant damage by the borer-rot complex on six sugarcane cultivara This research was conducted to determine the dimensions of damage by the sugarcane borer D-itr'a iavuL is (Fabr. 1794) and the associated stalk rots induced by funcji on six sugarcane cultivara. For this determination, staiks were opened longitudinally to evaluate the lengtii, volume of the dama ge region and volumetric damage index (volume of the iawaqcd region in relation to the total volume of the internode). The highest proportion of damage was due to fungai rota. For six cultivars, the average damage duo to fungi was 70% with respect to length and 95% for both volume and volumetric damage index. The dimensions of the daniagcd region varied depending on cultivara. In general the least amount of damago was obser ved in cultivar CB 47-355 for ali variables meaaurod.The greatest amount of damage was observed in cuitivars NA 56-79 and IAC 48-65. Recebido em 06/07/88 Complexo formado pela broca Diatraea sacchoralis (Fabricius, 1794) e pe los fungos Colletotrichua falcatum Went e Fusariwn monilifsrmo Sheldon. 2 Pesquisa realizada com o apoio financeiro da FINEP. Parte da tese apresentada, pelo primeiro autor, como um dos requisitos ao Concurso de Livre-Dodncia pela ESALQ/USP.