Late-Instar European Corn Borer (Lepidoptera: Crambidae) Tunneling and Survival in Transgenic Corn Hybrids

Abstract

Field studies were conducted in 1996 and 1997 to determine injury by and survival of late-instar European corn borer, Ostrinia nubilalis (Hu¨ bner), on genetically altered Bacillus thuringiensis Berliner corn, Zea mays L. Cry1Ab events 176, Bt11, MON810, and MON802; Cry1Ac event DBT418; and Cry9C event CBH351 were evaluated. Plants of each corn hybrid were manually infested with two third-, fourth-, or Þfth-instar O. nubilalis. Larvae were held in proximity to the internode of the plant above the ear with a mesh sleeve. Larvae were put on the plants during corn developmental stages V8, V16, R1, R3, R4, R5, and R6. This study shows that not all B. thuringiensis hybrids provide the same protection against O. nubilalis injury. Hybrids with B. thuringiensis events Bt11, MON810, MON802, and CHB351 effectively protected the corn against tunneling by late-instar O. nubilalis. Event 176 was effective in controlling late-instar O. nubilalis during V12 and V16 corn developmental stages; however, signiÞcant tunneling occurred by fourth instars during R3 and R5. Event DBT418 was not effective in controlling late-instar O. nubilalis during corn vegetative or reproductive stages of development. Whether the B. thuringiensis hybrids satisÞed high-and ultrahigh-dose requirements is discussed. KeywordsOstrinia nubilalis, Bacillus thuringiensis, resistance management, high-dose strategy

Larval survival and plant injury of Cry1Ab-susceptible, -resistant, and -heterozygous genotypes of the sugarcane borer on transgenic corn containing single or pyramided Bt genes

“…The larval survivorship (72-84% on leaf tissue after 6 d and 42.6-62.5% on intact plants after 21 d) observed in the current study was similar to that reported in other earlier studies (Walker et al, 2000;Wu et al, 2007;Ghimire et al, 2011). Larvae of all three genotypes of D. saccharalis on non-Bt corn plants also made a substantial number of entry/exit holes on the stalks and caused significant tunneling inside stalks.…”

Regulating insect resistance management: the case of non-Bt corn refuges in the US

“…These studies focused on ECB baseline susceptibility to Bt toxins (Marçon et al, 1999), the initial frequency of alleles conferring Bt resistance in ECB populations , new methods for detecting these alleles in natural populations (reviewed in Venette et al, 2002), modeling and simulating the evolution of Bt resistance (Onstad and Guse, 1999;Davis and Onstad, 2000;Ives and Andow, 2002), the selection of Bt-resistant strains (Bolin et al, 1999), the genetics of Bt resistance (Huang et al, 1999a) and tests on whether Bt corn produced sufficient toxin to kill ECB (Walker et al, 2000).…”

Functional dominance of different aged larvae of Bt-resistant Spodoptera frugiperda (Lepidoptera: Noctuidae) on transgenic maize expressing Vip3Aa20 protein

“…This behavior can expose the target pests to sublethal doses of Bt proteins through initial feeding in the Bt plant and subsequent feeding in the non-Bt plant (Andow, 2008). In addition, several studies showed that susceptibility of target pests to Bt proteins decreases throughout larval development (Ashfaq et al, 2001;Walker et al, 2000;Li et al, 2006;Armstrong et al, 2011). In this context, to optimize resistance management strategies, we evaluated the functional dominance of different aged larvae of Bt-resistant Spodoptera frugiperda in Bt maize expressing Vip3Aa20 protein.…”