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To The Next Level

Tuesday, January 1, 2008
filed under: Insects

There are positives and negatives associated with being a native species plant. Sunflower is, of course, native to North America, and the wild native sunflower is a treasure of resistant genes. But with a native species crop come a number of native insects that have used the native sunflower plant as a host for many centuries. Most of these insects have, as a result, easily adapted to commercial sunflower.

Using insecticides and date of planting are the primary methods to control insect damage to sunflower. However, plant resistance is now on the drawing board. The National Sunflower Association, USDA’s Agricultural Research Service and the university research community have been teaming up to determine sunflower resistance levels in interspecific crosses, accessions and breeding lines. This work has been going on for the last four years in North Dakota, South Dakota, Kansas and Colorado.

Among the challenges of this type of research is the need for consistent insect pressure each year. Fortunately, researchers in each state have identified areas where certain insects seem to show up annually.

One of those areas is Colby, Kan. Better yet, Colby is the site of the Kansas State University Northwest Research & Extension Center. The center has all of the requirements: personnel, adequate land, water and, of course, native insects.

For the past four years, Dr. Rob Aiken at the Colby center has teamed up with Dr. Larry Charlet of the USDA-ARS Sunflower Research Unit in Fargo, N.D., to test crosses, accessions and breeding lines for tolerance to the stem weevil (Cylindrocopturus adspersus), the long-horned beetle (Dectes texanus) and the sunflower moth (Homoeosoma electellum).

All three of these insects can have a significant impact on yield. Screening results from 2002 to 2006 revealed promising resistant germplasm for these insects. According to Charlet, the 2004 stem weevil trial had six resistant lines with an 80-90% reduction in the mean number of weevil larvae in the stalks, compared to the most susceptible lines. These resistant lines were retested in each subsequent year and were also crossed with other tolerant lines to produce new populations for testing.

Pursuing Resistance

To move this promising work forward as quickly as possible, the NSA Board of Directors recently agreed to fund a post-doctoral scientist to work with Charlet, the rest of the USDA-ARS Sunflower Research Unit team and KSU’s Aiken, with the goal of releasing resistant germplasm to the hybrid seed industry as soon as possible.

Aiken will expand the screening nursery at Colby. More accessions and crosses will be tested for the stem weevil, the longhorned beetle and the moth. The best lines will be randomly mated to begin development of the next cycle of F1 progeny lines. There will be test crosses with elite lines and molecular mapping using an assortment of marker technologies, Charlet reports. This will greatly aid the efficient transfer to commercial elite lines.

According to Aiken, the goal is to identify germplasm with resistance or tolerance to more than one insect pest, such as to the stem weevil and the long-horned beetle, both of which are stem insects. “We hope to hit two insects with a stacked set of resistant genes,” he remarks.

The NSA Board of Directors is committed to taking this work to the next level. Board vice president and South Dakota grower Tom Young says that getting public money to fund crop research at universities or at USDA is a real challenge these days. “We decided we need to step up to the plate and get this work done as soon as possible, so our company breeders can get improved hybrid resistance to farmers as soon as possible,” Young states. “The NSA made a three-year commitment to funding this post-doc position. It is a great example of using checkoff dollars for a very specific goal.” — Larry Kleingartner

The NSA Board of Directors also approved the funding of a post-doctoral entomologist at North Dakota State University to begin work on the sunflower maggot (Neotephritis finalis). Dr. Jan Knodel, NDSU entomologist, reports that field surveys have been picking up more damage from this insect in parts of North and South Dakota. Seed companies also have reported higher incidence in their nurseries. Historically, this insect has been generally benign; but damage was definitely identifiable in 2007.

Not a great deal is known about the sunflower maggot, so the new post-doc will work to determine the life history of the maggot, how each generation might damage the sunflower head, and the economic impact of this pest. Field studies will be conducted looking at planting date, plant resistance and chemical control. “At the present time, we do not have an economic threshold for the control of this pest. This will be one of the key research areas we need to accomplish,” Knodel says.

Munich, N.D., grower and NSA first vice president Don Schommer says the NSA will be sharing the cost of this post-doc with NDSU. “It is another example of farmer and industry checkoff dollars working together with an institution like NDSU to get some key work done,” Schommer points out. Like the USDA/KSU post-doc position, this is also a three-year commitment by NSA.
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