Establishment of Cry9C Susceptibility Baselines for European Corn Borer and Southwestern Corn Borer (Lepidoptera: Crambidae)

Abstract

In 1997 and 1998, Cry9C susceptibility baselines were established for field-collected populations of European corn borer, Osrinia nubilalis (Hubner), and southwestern corn borer, Diatraea grandiosella Dyar. Bioassay of neonate European corn borer larvae of 16 colonies collected from the midwestern United States indicated LC50 values ranging from 13.2 to 65.1 ng of Cry9C protein per square centimeter. Neonate European corn borer LC50 values ranged from 46.5 to 214 ng/cm2. Neonate larvae of three colonies of southwestern corn borer collected from the southern and southwestern United States exhibited LC50 values from 16.9 to 39.9 ng of Cry9C protein per square centimeter. Southwestern corn borer neonate LC90 confidence limit values ranged from 40.3 to 157 ng of Cry9C protein per centimeter. The most sensitive southwestern corn borer colony was collected from the Mississippi delta exhibiting an LC50 value of 22.6 ng of Cry9C per cm2 and also displayed the widest LC0 confidence limits of 40.3-94.8 ng of Cry9C per cm2. Geographic baseline susceptibility data establishes the natural genetic variation and provides the foundation for future testing of insect populations exposed to increased use of Bacillus thuringiensis-based crops. Insect resistance management and stewardship of Cry9C will rely upon baseline data for the validation of discriminating dose assays for European corn borer and southwestern corn borer.

Use of Bacillus thuringiensis Toxins for Control of the Cotton Pest Earias insulana (Boisd.) (Lepidoptera: Noctuidae)

“…From a resistance management standpoint, the most active proteins are good candidates for use in the control of this pest in addition to, or combination with, Cry1Ac, except for Cry1Ab, which shares binding sites with Cry1Ac. Cry9Ca is of particular interest since besides being the most active protein, it has a wide spectrum of toxicity that includes other important cotton pests, such as H. armigera, H. virescens, and Spodoptera littoralis (26,37,46).…”

Monitoring of Sesamia nonagrioides resistance to MON 810 maize in the European Union: lessons from a long‐term harmonized plan

“…A main element in IRM plans is the monitoring for target pests' susceptibility to the Bt proteins in areas with high adoption rates, to detect, in a timely manner, any resistance that evolves . For MON 810 in the EU, the European Food Safety Authority (EFSA) defined a sampling zone of high Bt maize adoption as a zone where MON 810 occupies >50% of the total maize cultivation area for at least three consecutive years.…”

Resistance monitoring of field populations of the corn borers Sesamia nonagrioides and Ostrinia nubilalis after 5 years of Bt maize cultivation in Spain

“…The first procedure involves establishment of the natural susceptibility of different geographical populations to Bt toxins and systematic field monitoring in Bt crops to recognize resistance when it appears. Baseline susceptibility to Bt toxins has been established for ECB populations from the USA (Siegfried et al., 1995; Huang et al., 1997; Marçon et al., 1999; Reed & Halliday, 2001), and northern Italy (Marçon et al., 1999). Accordingly, we determined the baseline susceptibility to Cry1Ab toxin for four Spanish populations of MCB (Madrid, Andalucía, Galicia, and Ebro) and two populations of ECB (Ebro and Madrid) in 1998 (González‐Núñez et al., 2000).…”