By Bruce Barker
VT Double PRO® RIB Complete® Complete delivers insect control in a bag.
Monsanto Canada’s VT Double PRO® RIB Complete® Complete has become an option for corn growers now that several corn hybrids with early maturity are available in Western Canada. The stacked traits provide dual modes of action for above-ground protection from European corn borer, corn earworm, and fall armyworm. With refuge-in-the-bag convenience, the trait provides simplicity and insurance against above-ground insect threats.
“We hear quite a bit about European corn borer from field agronomists in Manitoba. Corn borer seems to be spotty, but where it is present, it can impact yield,” says Chase Phillips, technology development representative with Monsanto Canada.
In 2016, John Gavloski, entomologist with Manitoba Agriculture, said European corn borer populations were noted to be high in the central region of Manitoba, which includes the Red River Valley. He says the insect tends to go through cycles in Manitoba.
“For several years they were not much of an issue, but populations seemed to have increased in the last couple of years. It’s hard to know how long increases in population will continue before regulating factors reduce levels again,” says Gavloski.
Gavloski says the corn earworm does not overwinter in Manitoba, but in some years does arrive later in the season. It can be a big concern in sweet corn but is less of a concern in field corn. Fall armyworm also does not overwinter in Manitoba. It can occur here, but is not very common.
The European corn borer can cause stalk breakage and ear drop where the cob falls to the ground, both of which can result in significant yield loss. The adult moths lay eggs on the underside of corn leaves near the mid-rib during warm summer evenings. The eggs hatch, and the larvae go through five instar stages. The third instar larvae bores into the corn stalk and later instars feed inside the stalk and ear shanks. Once mature, the mature larvae overwinter in corn stalks, cobs, and plant debris on the soil surface.
While insecticide application is an option, once the larvae have tunneled into the stalk, it is ineffective. Insecticides should only be applied when economic thresholds have been surpassed. Manitoba Agriculture has an Economic Threshold chart that takes the number of European corn borer larvae, insecticide control costs, and crop value into consideration. For example, if insecticide control costs $18 per acre, and the corn is worth $450 per acre, the economic threshold would be one larvae per plant.
The VT Double PRO® RIB Complete® Complete includes dual modes of action (expresses proteins from Bacillus thuringiensis) for improved insect control, but to also help manage Bt resistance. Similar to tank mixing different herbicide modes of action to help manage weed resistance, having dual modes of action can also help provide maximum trait durability.
Additionally, a refuge of non-Bt hybrids is required to reduce the odds of European corn borer developing resistance to Bt corn. With Monsanto’s RIB Complete brand, the refuge hybrid is mixed in to provide a refuge-in-a-bag, providing the convenience of automatic refuge compliance with the lowest refuge available.
Trait as insurance
Phillips says that Monsanto ran some research trials in Western Canada from 2013 through 2015 comparing a VT Double PRO® RIB Complete® Complete corn hybrid to a corn hybrid with the same genetics but only with the Genuity® Roundup Ready 2 Yield® trait. The trials were conducted across Western Canada.
“In areas where the European corn borer is established, like the Red River Valley, we saw less stalk lodging and higher yield. As we moved out of the traditional corn area towards Brandon and into Saskatchewan, there wasn’t as much of a difference,” says Phillips.
Gavloski says that whether a corn grower should invest in the extra cost for the Bt trait would vary with the grower and their region. “Corn growers in areas that have had some higher corn borer pressure recently have better odds of this being an economical investment for them. If European corn borer has not been a big concern in a region recently, then paying the extra price for corn borer protection would have less odds of being a good investment.”
That is the approach that Phillips is recommending, as well. He says that in areas where the European corn borer is established and has caused damage, investing in a VT Double PRO® RIB Complete® Complete corn hybrid could make sense as an insurance against insect losses. Moving outside of the Red River Valley, he says the decision would be based on past history of losses from the insect.
“Our trials found a benefit to using the VT Double PRO® RIB Complete® Complete traits where European corn borer has been a problem. In Eastern Canada, for example, where populations can be quite high, we’ve seen double-digit-bushel yield increases with the traits,” says Phillips. “You may not see that in Western Canada, but our research does show that in areas where the European corn borer has been a problem, there will be a yield advantage.”