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Standing up to aphids

2007 proved to be a good year for testing aphid-resistant soybeans.

February 16, 2008  By C&W

Soybean growers are getting closer to having access to a promising new tool in the fight against aphids. 2007 marked the first year of in-field testing of aphid-resistant soybeans in Ontario. Results show that soybeans will soon have the upper hand over these unpredictable pests.

Ontario soybean growers will see aphid-resistant soybeans in 2008 demonstration plots, Don McClure tells visitors.

“This year we had a good chance to test this material in a field situation for the first time and the resistance held up,” says Don McClure, soybean breeder with NK Brand, Syngenta Seeds. He notes aphid resistance is a native trait found in an old soybean variety which has now been incorporated by conventional breeding methodology into earlier maturity, adapted varieties for Canadian conditions.
A high level of aphid activity was exactly what was needed for trials. The yield-robbing pests have kept the soybean industry on its toes since they were first spotted in the province more than five years ago. In 2007, aphid presence continued to be sporadic across the province. The difference is that they came in earlier than ever before.

“The worst spot in Ontario was in the Listowel, London and Grand Valley triangle,” says Horst Bohner, soybean specialist, Ontario Ministry of Agriculture, Food and Rural Affairs. Aphids are known to overwinter in Ontario, but this infestation was probably the result of a population that migrated from the US. “Wind patterns bring them up. This hot spot is likely where they were first dropped in by some initial storms,” says Bohner.


While the aphids created real problems for soybean growers, the infestation gave McClure and his team an excellent opportunity to assess the new varieties at the Arva research station, which is located in the hot spot.

NK Brand is currently fine-tuning the testing and selection of the aphid-resistant material. “We’re making sure that we have the correct maturities for Ontario and Quebec. And we’re ensuring these lines are agronomically good as well,” says McClure who is breeding conventional varieties: his US counterparts are responsible for Roundup Ready efforts. “We’ve been doing as much testing as we can in a very short time period.”

Preparing for 2009 launch
Trials conducted during the 2007 growing season demonstrated promising results. “These results support the fact that the genetic markers we’ve been using for selection are working well and are identifying the resistant material. And secondly, the resistant material has been holding up to aphid infestation in the field,” says McClure.

Growers will have the chance to see demonstration plots of NK aphid-resistant soybeans in 2008. Commercial availability is expected in 2009. In the meantime, growers should continue to treat their seed and use insecticide sprays when populations reach the threshold of 250 aphids per plant or more. “In some cases this year, because the aphids came in early, the insecticide seed treatment Cruiser suppressed the aphid numbers during the early part of the season,” says Bohner.

Aphid-resistant soybeans performed well under severe infestation at the Arva research station, says Don McClure, soybean breeder for NK Brand, Syngenta Seeds.

Natural predators such as minute pirate bugs, lady beetles, damsel bugs and syrphid fly larvae will also do their part to keep the aphids in check. “When an insect first invades into a new territory, the predators aren’t there in large numbers and the aphids have an opportunity to explode in population. Over the years, predators start to build up and other ones move in and then you have a new dynamic that starts to occur,” says Bohner, citing that a lot of parasitic wasps were feeding on aphids in the Stratford area for the first time in 2007. “That helped to keep numbers low in some fields.”

Future holds more anti-aphid tools
Predators did not have a chance to keep up with the aphids in the hot spot of 2007. “We had situations where it was necessary to spray three times and a few growers even sprayed four times,” says Bohner. “I think it just goes to show how pervasive and virulent this pest can be. The products we have now work well if they have contact with the insect, but hopefully in the future we will have some longer day residual chemistries that are more systemic. Some of the companies are working on that and it will give us another tool in the toolbox.”

Bohner is also anticipating the aphid-resistant varieties. He was impressed with his first-hand look at their in-field performance. “There is definitely something to be said about aphid-resistant beans: especially when the populations come in early,” says Bohner. “It’s not that the resistant varieties have no aphids, they have a greatly reduced population which should translate into yield.”

McClure is looking forward to being able to share this yield advantage with soybean growers. And he is already working on what is next in the fight against aphids – additional resistance sources for more durable protection. According to McClure, researchers at Michigan State University have discovered other aphid-resistant material. “We’ll soon be able to stack genes for resistance,” says McClure. “This means we’ll be able to provide growers with a resistance package that will be extremely difficult for aphids to overcome.” -end-


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