by Elizabeth A. Tomlin
Are genetically engineered crops and pest management a silver bullet in plant breeding or just another tool in the toolbox?
“As a plant breeder, this is probably the single biggest topics that people want to hear about,” explained Dr. Margaret Smith, Professor of Plant Breeding, Cornell University, School of Integrative Plant Science, Plant Breeding and Genetics Section.
Smith was speaking to a large group of attendees at CNY CCE’s 2017 Corn Day at the Otsego Resort Hotel in Cooperstown, NY.
Joining Smith at the annual event was Dr. Elson J. Shields, Department of Entomology, Cornell University; Joe Lawrence, Dairy Forage Systems Specialist; event organizer CNY CCE Fields Crop Specialist Kevin Ganoe; and (by webinar) Dr. William Curran, Professor of Weed Science, Penn State University, Department of Plant Science.
“We all like silver bullets, they seem to solve all of our problems,” said Smith.
However, Smith pointed out that genetic engineering (GE) is more of a “tool in the toolbox” than a silver bullet.
Smith gave a brief history of GE and said GE is a “logical extension of what plant breeders have always done.”
Smith said the problem is that most folks outside of agriculture have little understanding of what plant breeders do and benefits to the consumer is unclear to them.
“New technology always raises concerns.”
GE crops include Bt crops (including corn, sweet corn and cotton), herbicide resistant crops (including soybean, corn, alfalfa, cotton, sugar beets and canola), and virus resistant crops (including papaya and squash).
Smith listed recently approved GE varieties including varieties of alfalfa, corn, cotton, soy beans, potatoes and apples, and spoke to attendees about effective crop maintenance through preparation (knowing beneficial and pests) and prevention (keeping pests out and crops healthy).
“Scout routinely and know your threshold!”
Use strategies wisely. Do the benefits justify the costs? Choose your tactics, environmental and economical wisely and integrate diverse tactics.
Smith reported the few varieties of major GE crops sold are sold for pest management; Bt crops for pest resistance, herbicide tolerant crops to manage weeds, and virus resistant crops. Because these crops are convenient and effective, it may have led to overuse resulting in new resistant weeds emerging and resistant insect populations. Weed resistance to Glyphosate has become a noted problem.
“Stacked” varieties, containing more than one combination of genes in a single plant line, are available with all GE traits or no GE traits. Recent additions include 2, 4-D resistance and Dicamba resistance.
“There is resistance in the Bt corn to Corn Rootworm,” stressed Dr. Elson J. Shields during his presentation of ‘The failing of our BT-corn events against Corn Rootworm and Western Bean Cutworm.’
“Let’s talk about what we have in our arsenal. It’s not very big.”
Shields said there are only three — or even less — toxins that are currently used, and advised attendees on the status of resistance as we know it, with a list of failures.
“For corn rootworm control with plant incorporated BT, we have only three groups of BT proteins in our toolbox. The first protein Cry 3Bb1 was first incorporated into corn by Monsanto and was the first BT-CRW protein marketed. The second protein is Cry 34/35, a two protein/toxin mixture, incorporated into corn by Dow and the third group is the Syngenta proteins mCry3A and eCry3.1Ab. Some corn varieties have two groups of CRW proteins incorporated called a pyramids. For example, a common pyramid is Cry 3Bb1 and Cry 34/35.”
Recent studies show plants containing CRW-BT Cry 3Bb1 protein did not kill the larvae that fed on the roots.
There were major field failures of Cry1F documented in 2016.
Cayuga County, New York, was only one county that documented widespread Bt failure for CRW.
Shields listed a number of states from New York across the corn-belt to Nebraska that have reported resistance and losses in crop yields and revenue.
“In Illinois and Indiana and half-way across Ohio, there’s a population of Corn Rootworm that doesn’t lay in corn anymore, they lay in soybeans.”
Although previously Corn Rootworm (CRW) were generally discouraged by crop rotation, and rotation continues to be a most valuable tool, farmers who have been rotating crops annually found that high populations CRW have adapted their behavior and are now laying in soybeans, then found in the corn the following year.
“Severe rootworm injury is usually easy to spot during the growing season by the goose-necked corn plants. The key diagnostic characteristic for rootworm damage in the fall is the curved stem.”
Keeping tabs on Bt traits can be problematic and change. Shields recommends searching online for the Handy BT Trait Table, published by Dr. Chris Difonzo/ Michigan State University.
He warns farmers need to take this issue of resistance seriously, as this genetic trait will be modified in the next generations and adapted as necessary for survival of this extremely adaptable species.
Effective strategies benefiting reduction of future losses, while helping to preserve technology against insect resistance, include rotation of affected fields, use of a soil insecticide (for conventional corn), and use of corn varieties with a different BT-CRW toxin.
“Rotate, rotate, rotate!” Shields stressed. “Rotate corn with non-host crops such as alfalfa, soybeans, or small grains.”
Shields cautions against layering soil insecticides over failing CRW-BT events.
A NYS Western Bean Cutworm (WBC) update was also presented by Shields.
WBC causes damage to field corn, sweet corn and dry beans.
In 2014/15 WBC were suspected of causing damage to red kidney beans in Livingston and Steuben counties in New York. Moth counts/ catches continue to increase, reaching thresholds. A threshold of concern is 100 moths. WBC egg masses, larvae and damage are easily detected on corn plants.
One Franklin County trap, planted May 25, 2016, caught 756. A second site planted May 11, 2016, caught 313.
A Lewis County trap, planted May 21, 2016, caught 190. In Jefferson County, a trap planted May 17, 2016, caught 553. Indication is that the moths overwintered.
“Major” field failures of Cry1F against WBC were documented in 2016. Growers are cautioned to choose their varieties wisely.
Shields and Smith both stressed the importance of using refuge plots.
These reports included studies evaluating the effectiveness of Bt corn for control of WBC in NNY, by Mike Hunter and Kitty O’Neil, Regional Field Crops specialists with CCE NNY, demonstrated that although suppression was noted, true control was not reported. Their studies also concluded that WBC moths prefer to lay their eggs on untasseled corn, so early planting may offer benefits in populated areas.
“The annual corn day continues to be a place where growers can pick up new information about corn production so they can improve their profitability,” said program coordinator, Kevin Ganoe, CNY CCE Field Crop Specialist.
Dr. James Baker, NYS Beef Specialist at Cornell, commented on corn production in the U.S.
“Newly released USDA agricultural projections through 2016 suggest that demand for U.S. corn will grow steadily over the next decade,” said Baker. “Rising yields will boost production and support the growing demand. With the exception of a drop in 2017, corn production is expected to increase through the forecast period. Lower corn prices and increasing corn production suggest that more corn will be used for feed and residual use.”
For more information contact Ganoe at email@example.com or go to www.fieldcrops.org.