Influence of plant silicon and sugarcane cultivar on mandibular wear in the stalk borer Eldana saccharina

Abstract

1 Silicon can increase the resistance of plants to attack by herbivorous insects. The present study aimed to determine the effect of silicon and cultivar on mandibular wear in larvae of the sugarcane stalk borer Eldana saccharina Walker (Lepidoptera: Pyralidae). 2 Four sugarcane cultivars, resistant (N21, N33) and susceptible (N11, N26) to E. saccharina were grown in a pot trial in silicon deficient river sand, with (Si + ) and without (Si -) calcium silicate. Individual third-instar larvae were confined on the sugarcane stalk at three known feeding sites (leaf bud, root band and internode) and left to feed for 21 days. 3 Eldana saccharina larval heads were mounted on stubs, with the mandibles oriented horizontally and photographed under a scanning electron microscope. Mandibular wear was measured from the digital images using a quantitative method. 4 Although there was a trend for increased wear in larvae that developed on Si + cane, no significant effect of silicon, cultivar or site on mandibular wear of E. saccharina was shown. 5 This is the first study to accurately and quantitatively measure the mandibular wear of an insect fed on Si + plants.

Silicon and Insect Pest Resistance

“…A correlation analysis showed that pupal weight, fecundity, net reproductive rate and intrinsic rate of increase were all negatively correlated with Si content in the corn diet, while the duration of larval and pupal stages, longevity of adults and mean generation times were not signifi cantly affected (Horng and Chu 1990 ). Later, several studies also showed that Si fertilization altered survival, reproduction and host plant preferences of chewing (Goussain et al 2002 ;Massey et al 2006 ;Kvedaras et al 2009 ) and sucking insects (Basagli et al 2003 ;Correa et al 2005 ;Korndörfer et al 2011 ). Costa and Moraes ( 2006 ) showed that the application of Si signifi cantly reduced the number of nymphs, the population growth rate, the post-reproductive period and the longevity of the greenbug.…”

“…It has been widely reported that the hardness of plant parts affected mandibular wear in leaf beetle ( P. versicolora ) (Raupp 1985 ;King et al 1998 ), bee ( M. rotundata ) Schaber et al 1993 ), noctuid lepidopteran larvae ( S. exigua ) (Korth et al 2006 ), weevil ( P. callosus ) (Barnes and Giliomee 1992 ), stalk borer (Kvedaras et al 2009 ) and even in the stylet of a true bug ( D. hesperus ) (Roitberg et al 2005 ). Mandibular wear is often attributed to Si deposited within plant tissues (Kvedaras et al 2009 ).…”

“…It has been well documented that Si has a clear prophylactic effect against a wide range of insect-feeding guilds, including lepidopteran borers, folivores, phloem-feeding insects, xylem-feeding insects and other plant feeders (Table 10.1 ; also see Reynolds et al 2009 ). Ukwungwu and Odebiyi ( 1985 ) Asiatic rice borer ( Chilo suppressalis ) Rice Sasamoto (1958), Nakano et al ( 1961 ), Djamin and Pathak ( 1967 ), Dravé and Laugé ( 1978 ), and Hou and Han ( 2010 ) Horng and Chu ( 1990 ) Fall armyworm ( Spodoptera frugiperda ) Maize Goussain et al ( 2002 ) Central shoot fl y ( Atherigona indica infuscate ) Sorghum Ponnaiya ( 1951 ) Stalk borer ( Eldana saccharina ) Sugarcane Rao ( 1967 ), Meyer and Keeping ( 2005 ), Keeping and Meyer ( 2002 ), Keeping and Meyer ( 2006 ), Keeping and Kvedaras ( 2008 ), and Kvedaras et al ( 2007Kvedaras et al ( , 2009 ) Stem borer ( Diatraea saccharina ) Sugarcane Pan et al 1979, Elawad et al ( 1985, and Anderson and Sosa ( 2001 ) Singh et al ( 1993 ) Interestingly, almost all case studies have shown a positive relationship between pest damage control and accumulation of Si in plant organs (Table 10.1 ), with the notable exception of greenbugs on wheat ( Triticum aestivum ) and barley ( Hordeum vulgare ) (Lanning 1966a , b ). However, the mechanisms underpinning the role of Si against insects still remain poorly understood.…”

“…Mandibular wear is often attributed to Si deposited within plant tissues (Kvedaras et al 2009 ). Insects feeding on high-Si plants suffered higher mandibular wear, as has been reported for stem borer C. suppressalis (Sasamoto 1958 ;Djamin and Pathak 1967 ) and rice leaf roller larvae C. medinalis (Hanifa et al 1974 ;Ramachandran and Khan 1991 ) feeding on rice and for fall armyworm ( S. frugiperda ) feeding on corn plants (Goussain et al 2002 ).…”

History and Introduction of Silicon Research

“…Since then, many fi eld trials on application of silicate materials to highly weathered entisols, ultisols and oxisols low in soluble Si have resulted in signifi cant responses in both cane and sugar yields in several African countries including Mauritius and South Africa (Bishop 1967 ;Cheong and Halais 1970 ;Du Preez 1970 ;Meyer and Keeping 2001 ). The more recent research on Si in Africa has been mainly focused on the infl uence of Si on the resistance of sugarcane to the stalk borer Eldana saccharina (Keeping and Meyer 2006 ;Smith et al 2007 ;Kvedaras et al 2007Kvedaras et al , 2009see Chap. 10 ).…”