Larval performance of the pyralid borer Eldana saccharina Walker and stalk damage in sugarcane: Influence of plant silicon, cultivar and feeding site

Abstract

Applied silicon (Si) can improve resistance of plants to insect attack. We investigated the interactions between soil applied Si, sugarcane cultivar, and three documented feeding/penetration sites (internode, leaf bud, and root primordia), each at three heights (top, middle, and base) on the stalk and their effects on stem borer, Eldana saccharina Walker (Lepidoptera: Pyralidae) performance and the stalk damage it inflicts. Four sugarcane cultivars, treated (Si+) and untreated (Si−) with calcium silicate, were artificially infested with E. saccharina and the larvae were examined 21 days later. Silicon treatment significantly increased stalk Si content in all sugarcane cultivars and, overall, significantly reduced borer growth rate and also reduced stalk damage, particularly at the internode. Borer survival and growth rate and stalk damage were lowest at the internode, particularly in Si+ resistant cultivars. Although the internode had the hardest rind, hardness at each site was not significantly increased by Si+.

Keywords:

• Antibiosis
• calcium silicate
• host plant resistance
• mechanical barrier
• Integrated Pest Management
• Saccharum

Acknowledgements

We thank Andrew Govender, Sipho Zuma and the Entomology survey teams at SASRI for their assistance in many aspects of the work. Professor Steven Piper is thanked for providing statistical consult, Chandani Sewpersad for the statistical analysis of the data and Rod Harding for the experimental design. Jan Meyer and Gayshree Naidoo are thanked for the Si analyses. Sagie Doorsamy is thanked for artwork. Auas Industrial Minerals (Fontaine bleau, Johannesburg, South Africa), through consultation with Tony Derrick and a local grower, Trevor Thompson, are gratefully acknowledged for the supply of wollastonite. The SASRI Insect Rearing Unit provided the egg batches. Research funding was provided by SASRI, the National Research Foundation (NRF) of South Africa, the University of the Witwatersrand, and the Centre de Coopération Internationale en Recherche Agronomique pour le Développement.