ABSTRACT
Mahanarva fimbriolata (Stål) (Hemiptera: Cercopidae), the sugarcane spittlebug, is one of the most important pests of this crop in Brazil. The magnitude of its damage depends on the pest population, the plants size when they are infested and the cultivar tolerance. The knowledge about those parameters allows the elaboration of the spittlebug management matrix, in which small plants and less tolerant varieties fields are prioritized for sampling and controlling in relation to developed plants and tolerant varieties fields. Therefore, this study aimed to evaluate the response of sugarcane genotypes to M. fimbriolata, so that they can be correctly allocated in the management matrix. Two experiments were carried out under laboratory conditions using a randomized block design with treatments in a factorial arrangement of 2×11 (experiment 1) and 2×21 (experiment 2), with six (experiment 1) or five replicates (experiment 2). The first factor included two levels of infestation (infested and noninfested plants with spittlebugs), while the second consisted of the cultivars. Cultivars IACSP01-5503, CTC 9004 and RB925211 were considered tolerant to spittlebug, they did not show significant reductions in aboveground biomass, despite showing symptoms of pest attack, as leaves yellowing, while CV6654 and IACSP01-3127 were the least tolerant cultivars, showing the highest reduction in aboveground biomass due to M. fimbriolata infestation. Thus, CV6654 and IACSP01-3127 should be prioritized for sampling and control over the others. On average, spittlebug infestations caused 30.9 % of reduction of aboveground biomass.
A cigarrinha das raízes, Mahanarva fimbriolata (Stål) (Hemiptera: Cercopidae), é uma das mais importantes pragas da cana-de-açúcar no Brasil. A grandeza de seus danos depende da população, do tamanho da planta ao sofrer o ataque e da tolerância da cultivar. O conhecimento sobre esses parâmetros permite a elaboração da matriz de manejo de cigarrinha das raízes, na qual canaviais de plantas pouco desenvolvidas e cultivares não tolerantes são priorizados para amostragem e controle em relação a canaviais de plantas mais desenvolvidas e variedades tolerantes. Portanto, o objetivo do presente trabalho foi avaliar a reação de cultivares de cana-de-açúcar à M. fimbriolata, para que elas possam ser adequadamente locadas na matriz de manejo. Dois experimentos foram conduzidos em condições de laboratório, usando o delineamento de blocos casualizados com seis (experimento 1) ou cinco (experimento 2) repetições e tratamentos em arranjo fatorial 2×11 (experimento 1) e 2×21 (experimento 2). O primeiro fator foi representado pelos dois níveis de infestação de cigarrinha (infestado e não infestado), enquanto o segundo, pelas cultivares em estudo. As cultivares IACSP01-5503, CTC 9004 e RB925211 foram consideradas tolerantes a M. fimbriolata, visto que a praga não causou redução significativa da massa verde da parte aérea, apesar de ter provocado alguns sintomas de ataque, como amarelecimento de folhas, enquanto CV6654 e IACSP01-3127 foram as cultivares menos tolerantes, pois mostraram as mais altas reduções na massa verde da parte aérea das plantas. Assim, CV6654 e IACSP01-3127 deveriam ser priorizadas na amostragem e controle em relação às demais. Na média, a cigarrinha das raízes provocou 30,9 % de redução na massa verde da parte aérea das plantas.
Subject(s)
Pest Control/methods , Saccharum/parasitology , Plant Defense Against Herbivory , Hemiptera/pathogenicityABSTRACT
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.
Subject(s)
Pest Control , Hemiptera , Agricultural Pests , Saccharum/parasitologyABSTRACT
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.(AU)