ABSTRACT The spittlebug Mahanarva fimbriolata (Stål) (Hemiptera: Cercopidae) is one of the most important pests of sugarcane in Brazil. Measures for population control are currently restricted to the use of chemical insecticides and fungus Metarhizium anisopliae, in part because very little information exists regarding resistance of sugarcane cultivars. Therefore, the aim of this study was to evaluate resistance mechanisms of 12 different sugarcane cultivars to M. fimbriolata to provide information for growers for pest management. Isolated buds of each cultivar were planted in pots and kept in a greenhouse for approximately three months. The pots were then moved to climate test chambers (26 ± 1 ºC; 70 ± 10 % relative humidity; 12 h photoperiod) to carry out laboratory tests to evaluate adult feeding and female oviposition preferences (using both free-choice and no-choice tests) as well as the effects of cultivars on nymph development and cultivars tolerance to pest attack. The least attractive cultivars for adult feeding were IACSP96-2042 and IAC91-1099. Cultivars IACSP96-2042, IACSP96-3060 and IACSP94-2101 received the fewest eggs in the free-choice and no-choice oviposition tests and exhibited some level of antixenosis resistance. Cultivar IAC91-1099 showed the highest level of antibiosis resistance with a nymph survival rate in the roots of only 20 %. Finally, cultivar IACSP94-2094 appears to be tolerant to M. fimbriolata, as it did not show significant reductions in aboveground biomass weight, despite showing reduced leaf chlorophyll levels following pest attack.

RESUMO O objetivo do presente trabalho foi avaliar a reação de dez cultivares de cana-de-açúcar à Diatraea saccharalis Fabr., em experimento desenvolvido em delineamento em blocos casualizados com seis repetições e tratamentos em esquema fatorial 2x10. O primeiro fator foi constituído por dois níveis de infestação de broca (infestado e não infestado), e o segundo fator, pelas dez cultivares de cana-de-açúcar em estudo (IAC87-3396, IAC91-1099, IACSP93-3046, IACSP94-2101, IACSP94-2094, IACSP94-4004, IACSP95-5000, IACSP96-3060, IACSP96-2042 e SP91-1115). O ensaio foi avaliado em dois ciclos da cultura, cana-planta e primeira soca. Todas as cultivares foram muito atacadas pela broca, sendo IACSP94-4004, IACSP96-2042 e SP91-1115 as mais infestadas e danificadas pelo inseto. Para cana-planta, parcelas infestadas pela broca tiveram maior teor de fibra que parcelas não infestadas. Para soqueira, parcelas infestadas produziram 10% menos, com menores teores de pureza e maiores teores de açúcares redutores totais que as não infestadas.

ABSTRACT The objective of this study was to evaluate the reaction of ten sugarcane cultivars to Diatraea saccharalis under field conditions, using a randomized block design with treatments in factorial 2x10 with six replications. The first factor was represented by two levels of infestation (infested and not infested) by borer and the second one, by the ten sugarcane varieties (IAC87-3396, IAC91-1099, IACSP93-3046, IACSP94-2101, IACSP94-2094, IACSP94-4004, IACSP95-5000, IACSP96-3060, IACSP96-2042 and SP91-1115). The experiment was evaluated in two crop cycles: plant crop and first ratoon. All cultivars were attacked by the borer, being IACSP94-4004, IACSP96-2042 and SP91-1115 the most damaged cultivars with the highest infestation index. During the plant crop, plots infested by the borer presented higher fiber content than the ones not infested. During the first ratoon, non infested plants produced 10% less and presented lower purity and higher content of reducing sugars than the non-infested plants.

A broca Diatraea saccharalis é uma das pragas mais importantes da cana-de-açúcar no Brasil, razão pela qual é relevante quantificar a interferência de seu ataque nos parâmetros tecnológicos dos colmos, utilizados como matéria-prima na indústria de açúcar e etanol. Assim, o objetivo do presente trabalho foi avaliar os efeitos da intensidade de infestação sobre os parâmetros tecnológicos, entre os quais fibra na cana e pol na cana, das cultivares IAC91-1099, IACSP93-3046 e IACSP95-5000. Para tanto, os colmos coletados em campo foram agrupados de maneira a compor amostras com 0, 3, 6, 9, 12 e 15% de entrenós brocados, que foram então analisadas. Maiores ataques de broca resultaram em aumento nos teores de fibra e de açúcares redutores, e redução nos teores de pol na cana e na pureza. Na média, a curva que representa a relação entre pol na cana (y) e intensidade de infestação (x, % de entrenós brocados) é dada por y=16,591-0,0672x, cujo coeficiente de determinação (r²) foi 0,92.

Sugarcane borer Diatraea saccharalis is one of the most important pests of sugarcane in Brazil, being its influence on technological parameters of the new cultivars stalks used as raw material for sugar and ethanol industry unknown. The objective of this study was to evaluate the effect of infestation levels on technological parameters of the stalks of three sugarcane varieties IAC91-1099, IACSP93-3046 and IACSP95-5000. Stalks harvested in field were grouped in order to compose samples with 0, 3, 6, 9, 12 and 15% of bored internodes. High levels of bored internodes resulted in high values of fiber and reducing sugars and in lower values of sugarcane pol and purity. On average, the curve that represent the relationship between sugarcane pol (y) and infestation level (x) was y=16.591-0.0672x, with the coefficient of determination (r²) of 0.92.