Remember that post I wrote a few weeks ago about why we were planting pink soybean seeds? Here’s some of the “blue” corn we planted. The blue color simply comes from the seed treatment we use on our corn seed, which protects the seed from diseases for a short time, giving the seed enough time to germinate and get a good start.
If you look closely, you’ll notice that there’s two colors of blue seed in the photo. One is more of a greenish-blue and the other is more of a purplish-blue (if you’re colorblind, I guess you’ll just have to trust me on this 😉 ). There’s a lot more of the greenish-blue seed- about 95% of the bag, to be exact. The other 5% is what farmers and seed companies call “refuge” seed. The two colors simply differentiate between the refuge seed and regular seed in the bag.
Before I explain what a refuge is and the purpose and importance of planting a refuge, let’s talk a little more about the corn in the picture. This specific corn variety has something we call Bt resistance. Bt stands for Bacillus thuringiensis and is a naturally-occurring bacterium that was discovered in the soil. Long story short, Bt corn is bred to protect itself from certain insects, specifically certain caterpillars. The corn can fend itself against these insect pests without the use of insecticides. Because Bt came from somewhere other than corn, Bt corn is considered a genetically modified organism, or GMO.
Bt corn is grown on our farm to protect the corn crop from corn rootworms. Different Bt varieties can protect corn against the European corn borer, corn rootworm, and/or corn earworm. It’s possible to “stack” the Bt traits when breeding a variety, which gives the corn multiple resistance traits, such as resistance to more than one of the insects I listed above. Using Bt corn on our farm means that we use fewer insecticides (if any) on the corn during the growing season and don’t lose any yield. Other crops that may have Bt traits include sweet corn and cotton.
So back to refuge. Because insects are live creatures, they evolve. This is where resistance comes from. Weeds and diseases also can evolve to adapt to their growing conditions, which also leads to herbicide and fungicide resistance, respectively. Resistance will eventually happen, but there are steps farmers can take to try to slow the process. One of the steps for Bt traits specifically is to plant what we call a refuge crop. A refuge in this case would be a non-Bt variety of corn planted in the same field as the Bt corn. Basically, this allows some of the targeted insects (like corn rootworm) to survive and produce offspring that are still susceptible to Bt corn (they’ll die when they try to feed on these plants). Some of these targeted insects will inevitably produce offspring that are resistant to Bt corn (an example of evolution at work), but the Bt-resistant offspring will mate with Bt-susceptible insects and produce Bt-susceptible offspring (remember those Punnett squares from 9th grade biology?). If farmers didn’t plant a refuge, over time there would be a lot more Bt-resistant targeted insects out in their fields, making the Bt corn they plant less effective at controlling the targeted insect population.
To avoid losing the Bt technology, the majority of farmers comply with the refuge guidelines. In fact, the EPA mandates that farmers who grow Bt corn plant a refuge. Planting a refuge has gotten a lot easier for farmers in the last few years. Before, refuge guidelines required farmers in our region who chose to grow Bt varieties to plant 20% of their field in refuge. There were several ways to do this, such as putting the refuge around the border or in rows between the Bt corn or even in the next-door field, as long as farmers followed the 20% rule. Back then, the farmers on our farm loaded their 12-row planter with 9 rows of Bt and 3 rows of refuge for each pass across the field because that’s what worked best for them. In fact, they were a little over-compliant with a 25% refuge, but that was okay. Now we have refuge-in-a-bag, which means that the refuge seeds are mixed in with the Bt seeds. This works, too, and also guarantees 100% compliance with the refuge rules. In fact, the percent required refuge has been lowered in the last few years. Today, if planting refuge-in-a-bag seeds, only 5% of the field has to be refuge and the non-Bt plants are mixed in with the Bt plants all over the field. This still fends off resistance while helping farmers preserve a little more yield from the targeted insects.
Like I said, planting a refuge is just one thing farmers do to prevent resistance. Resistance is not something farmers want on their farm, since it means they lose valuable technologies, such as Bt varieties, and would have to use alternative measures, such as insecticides, to control these insects in their fields. New technologies don’t come out very often. It’s a very expensive process to bring this technology from scientific discovery to farms costing millions of dollars and usually taking at least 10-15 years. More often than not, these technologies don’t even make it to the farm, even after researchers have spent several years and lots of money on them. That’s why it’s so important for farmers to preserve and protect this technology, and the majority of farmers do a very good job doing so.