Bt‐maize as a potential trap crop for management of Eldana saccharina Walker (Lep., Pyralidae) in sugarcane

Abstract

Notwithstanding the introduction of several pest management tactics, the stalk borer Eldana saccharina Walker (Lep., Pyralidae) remains the most serious pest in South African sugarcane. A novel tactic for managing this pest in sugarcane would be the use of a dead-end trap crop that attracts moths for oviposition and curtails subsequent larval development, thereby reducing pest population size. Glasshouse bioassays, in which moths chose to oviposit on maize producing Bacillus thuringiensis Cry1Ab toxin (Bt-maize), non-Bt-maize or sugarcane of two cultivars (borerresistant and -susceptible), showed that E. saccharina laid significantly more eggs and egg batches per dry leaf and unit mass of dry leaf on maize (Bt or non-Bt) than on either of the cane cultivars. When moths had a choice of ovipositing on 2-, 3-, 4-or 5-month-old maize (Bt and non-Bt), dry leaf number and mass of dry leaf material was significantly correlated with number of eggs and egg batches, indicating that older plants, which carried larger amounts of dry leaf matter, were more attractive for oviposition. Finally, glasshouse assays in which hatching larvae fed on 2.5-, 3.5-and 4.5-month-old Bt and non-Bt-maize plants, showed that the Cry1Ab toxin was effective in killing E. saccharina larvae in all Bt-maize plant growth stages, confirming that Bt-maize fulfilled the third requirement (curtailing larval development) of a dead-end trap crop for this pest. We argue that Bt-maize warrants further testing in the field as a trap crop, both alone and as a component of a Ôpush-pullÕ or habitat management system for E. saccharina in sugarcane.

Short communication: The rate of release of Cry1Ab protein from Bt maize leaves into water

“…Although Lepidoptera are characteristically terrestrial, the Pyralidae family includes several species with truly aquatic larvae (Gerber and Gabriel, 2002). The Pyralidae family also includes several maize and sugarcane pests which are susceptible to Cry1Ab protein, for example, Eldana saccharina (Walker) (Keeping et al 2007) and Chilo partellus (Swinhoe) in South Africa (Van Rensburg, 1999).…”

“…Direct exposure to Cry proteins takes place when transgenic crop residues are consumed by organisms (Kratz et al, 2010), while indirect exposure may be through leaching of protein from crop plant tissue into the aquatic environment, with possible adverse effects on exposed organisms (Li et al, 2007;Venter and Bøhn, 2016). There are several routes through which Cry proteins enter the aquatic ecosystem in which aquatic organisms are exposed to these proteins through different exposure pathways (Carstens et al, 2012).…”

Advances in Transgenic Research for Insect Resistance in Sugarcane

“…A novel tactic that makes use of a Bt-maize expressing Cry1Ab as a dead-end trap crop for managing the sugarcane stalk borer E. saccharina was proposed on the basis of larval mortality rates in all crop stages and higher oviposition rates on maize than on either a resistant or a susceptible sugarcane line (Keeping et al 2007). The authors argue that Bt-maize warrants further testing in the field as a trap crop, both alone and as a component of a 'push-pull' or habitat management system for E. saccharina in sugarcane.…”

Sugarcane borers: species, distribution, damage and management options

“…When intercropped with sugarcane, M. minutiflora can reduce E. saccharina populations in sugarcane by up to 50% and diminish damage to sugarcane by up to 75% (Barker et al 2006). Additionally, Bt maize functions as a 'dead-end trap crop' due to the toxic effect of the cry1Ab protein on E. saccharina larvae, potentially mitigating borer damage on sugarcane (Keeping et al 2010). Recently, MON 95379 Bt maize as a new tool to manage sugarcane borer (D. saccharalis) in South America (Horikoshi et al 2022).…”