The best way to preserve the benefits and insect protection of Bacillus thuringiensis (B.t.) technology is to develop and implement an Insect Resistance Management (IRM) plan. A corn refuge is a key component of an IRM plan. Refuge requirements vary by the type of corn product being planted and the location of planting. Growers planting a product requiring a structured refuge must plan accordingly.

Why Plant a Refuge?

A refuge is a block or strips of the same crop that does not contain a B.t. technology for controlling targeted insect pests, or the refuge can be included in a seed blend product approved by the Canadian Food Inspection Agency (CFIA). The primary purpose of a refuge is to maintain a population of insect pests that are not exposed to B.t. proteins. This lack of exposure allows susceptible insects emerging from the refuge to mate with any rare resistant insects that may emerge from the B.t. crop. Susceptibility to B.t. technology would then be passed on to their offspring, helping to preserve the long-term effectiveness of B.t. technologies. To help reduce the risk of insects developing resistance, the refuge should be planted with a similar corn product, as close as possible to, and at the same time as, the corn crop containing B.t. technologies. With an effective IRM plan in place, growers will continue to benefit from the effective and consistent insect protection and top-yield potential found in crops containing these technologies.

The CFIA mandates resistance management strategies for B.t. technology. Insect resistance management is a requirement for purchasing and growing insect-protected corn products. The continued availability of B.t. technologies depends on grower compliance with CFIA standards. On-farm IRM compliance assessments are conducted during the growing season in Ontario, Quebec, and Manitoba. While only some farms are selected to ensure refuge compliance, it is important for all growers to have accurate records of where B.t. and refuge corn is planted. Failure of a grower to follow IRM guidelines and properly plant a refuge may result in that grower’s loss of access to B.t. technologies.

Common Refuge (for Rootworm and Corn Borer) for Stacked Traits Corn Products: A common refuge is a single field that serves as a refuge for both above-ground pests and below ground pests at the same time.

Corn IRM 1

The refuge configuration depeicted is offered merely as an example and is not necessarily to scale. Refuge requirements vary by the type of corn product being planted and the location of the planting. Please contact your seed dealer with any questions and/or call Monsanto's CustomerCare® line at 1-800-667-4944.

Corn Refuge Requirements

Refuges can be planted in a variety of patterns, from strips within the field or in an adjacent field as a block (Figure 2). Refuge requirements vary depending on the B.t. crop being planted (Table 1). Please consult Monsanto’s Technology Use Guide for specific refuge requirements. Growers can also use the Canadian Corn Refuge Hybrid Selector found at to help ensure compliance. This user friendly tool can be used to help calculate the correct refuge size and help select refuge configurations for planting various B.t. corn products.

Table 1. Refuge requirements vary by the type of corn product being planted
Corn IRM 2
1 Corn seed blend of 95% Bt seed and 5% non-Bt seed (This type of corn product satisfies the refuge requirements, requiring no seperate structured refuge.
Corn IRM 3
Figure 2. Various types of refuges and configurations. Planting the refuge in the same field or in a field adjacent to the B.t. corn product can simplify refuge planting options. If perimeter or strips are used for the refuge, they must be at least 4 consecutive rows wide for YieldGard VT Triple® products.

Contact your DEKALB® Brand seed representative for questions regarding specific corn products and refuge requirements.