Sublethal Effects of Cry 1F Bt Corn and Clothianidin on Black Cutworm (Lepidoptera: Noctuidae) Larval Development

Abstract

Black cutworm, Agrotis ipsilon (Hufnagel) (Lepidoptera: Noctuidae), is an occasional pest of maize (corn), Zea mays L., that may cause severe stand losses and injury to corn seedlings. The efficacy of the neonicotinoid seed treatment clothianidin at two commercially available rates and their interaction with a transgenic corn hybrid (Bt corn), trait expressing the Bacillus thuringiensis variety aizawai insecticidal toxin Cry 1Fa2, against black cutworm larvae was investigated. Clothianidin at a rate of 25 mg kernel(-1) on Bt corn increased larval mortality and reduced larval weight gains additively. In contrast, weights of larvae fed non-Bt corn seedlings treated with clothianidin at a rate of 25 mg kernel(-1) increased significantly, suggesting either compensatory overconsumption, hormesis, or hormoligosis. Both Bt corn alone and clothianidin at a rate of 125 mg kernel(-1) applied to non-Bt corn seedlings caused increased mortality and reduced larval weight gains. In two field trials, plots planted with Bt corn hybrids consistently had the highest plant populations and yields, regardless of whether they were treated with clothianidin at the lower commercial rate of 25 mg kernel(-1) The use of Bt corn alone or in combination with the low rate of clothianidin (25 mg kernel(-1)) seems suitable as a means of suppressing black cutworm in no-tillage cornfields, although rescue treatments may still be necessary under severe infestations. Clothianidin alone at the low rate of 25 mg kernel(-1) is not recommended for black cutworm control until further studies of its effects on larval physiology and field performance have been completed.

Tobacco Hornworm (Manduca sexta) caterpillars as a novel host model for the study of fungal virulence and drug efficacy

“…This pattern resembles the concept of hormesis often deployed by toxicologists to describe the response to toxins, where exposure to a low dose is beneficial while a higher dose results toxicity due to overcompensation in response to disruption of homeostasis 53 . While tissue-specific hormetic responses have been described in flies, where a virus-acquired cytokine relays ageing 54 , and examples of abiotic factors or signalling molecules affecting peas and aphid infestation 55 , immunity in plants 56,57 , life-span in malaria-transmitting Anopheles 58 , and larval development in Black Cutworm 59 , this example here could be the first involving a eukaryotic host-pathogen relationship. The underlying factor remains to be elucidated but C. neoformans ’ highly immunogenic capsule seems to be an excellent candidate 48 .…”

Insecticidal Activity of 11 Bt toxins and 3 Transgenic Maize Events Expressing Vip3Aa19 to Black Cutworm, Agrotis ipsilon (Hufnagel)

“…and H. zea) alone [29][30][31]. Corns expressing Cry1Ab (event Bt11 and MON810) or Cry1Fa2 (Event TC1507) demonstrate high efficacy against O. nubilalis [14,20,32], but they are unlikely to have a significant impact on BCW [1,33]. However, either the Cry1Ab × Vip3Aa20 pyramid of Bt11×MIR162 corn or Cry1Fa2 × Cry1Ab × Vip3Aa20 pyramid of TC150 × MON810 × MIR162 corn could provide a much broader-spectrum high dose against H. zea and S. frugiperda [34][35][36][37] as well as BCW [16].…”

Weather and regional crop composition variation drive spatial synchrony of lepidopteran agricultural pests

“…We also found declines in true armyworm and black cutworm, notable because these are significant pests of corn and other commodities. These declines began well before the introduction of Bt corn hybrids, but Bt toxins can limit populations of both species (Schaafsma et al ., ; Kullik et al ., ; United States Environmental Protection Agency ). Declines in these species are more likely driven by significant improvements in controlling weeds that attract ovipositing moths, a trend towards earlier destruction of winter cover crops, and the widespread and increasing use of neonicotinoid‐treated corn seed (Douglas and Tooker ).…”