Blueberry plants raised in "grow tubes" may look more robust, but appearances are deceiving. In fact, growing blueberries in the cylindrical structures is an exercise in futility for most Willamette Valley farmers, according to Oregon State University horticulture professor Bernadine Strik. "Grow tubes offered no advantage, and they cost money," said Strik while presenting her final research report on the subject to the Oregon Blueberry Commission on Dec. 4.

Being constrained in the long, narrow tubes did actually force blueberries to grow taller, but the plants had significantly smaller root masses and did not generate better yields, she said. "More shoots to less roots," summarized Strik, adding that the shoots themselves were flimsier. "I just like the sturdy cane growth rather than all that raggy-taggy little stuff." Considering that grow tubes cost about $0.50 to $0.80 apiece, and that about 1,450 blueberries are planted per acre, the added expense simply isn't justified west of the Cascades, she said.

However, Strik's results are specific to the Willamette Valley. In eastern Washington, on the other hand, the grow tube system may in fact shield plants from being whipped around by the wind, she said. "It could very well be that growers are right there," said Strik, noting that the plastic covers can also protect blueberry plants against herbicide drift. When Strik began studying grow tubes at a farm owned by Pan-American Berry Growers in Salem, blueberries grown in the cylinders looked very healthy upon visual inspection.

When they were dug up, though, the plants were found to be 71 percent lighter in dry crown weight and 44 lighter in dry root weight. "The growers themselves were shocked," said Strik. The tube system's weak performance can be attributed to insufficient photosynthesis. When the plant must grow in such a narrow space, upper leaves block sunlight from lower ones, Strik said. Both plastic and wire mesh tubes contributed to this effect, she said. "More shadows, less goodies for the roots," said Strik.

The grow tube report was one of many presented to the Oregon Blueberry Commission at the recent research progress report event in Corvallis, Ore. A summary of some other presentations:

Blueberry farmers spend money on renting honey bees, but native bumblebees provide the most pollinating muscle for free.

Thanks to their burlier structure, bumblebees are able to "buzz-pollinate," which means they rapidly shake flowers and collect pollen on their hind legs, according to Sujaya Rao, an OSU associate professor specializing in plant-insect interactions.

Honey bees, on the other hand, use the less efficient method of rubbing against the flowers' pollen-producing anthers. Effective pollination is important to blueberry growers because it corresponds with a greater number of seeds, and thus, larger fruit.

During her presentation, Rao described her preliminary research on native bumblebees, in which she collected samples of native pollinators at several sites in the Willamette Valley and found nine different species of bumblebees working in the fields.

In 2008, Rao plans to conduct tests comparing the pollinating abilities of bumblebees, honey bees, and leaf-cutting bees. A previous, similar experiment was suspended because the cages that were used to contain the pollinators failed to keep them trapped.

A fungal virus is believed to be at least partially responsible for a disease that causes blueberry plants to drop fruit several weeks before reaching ripeness, according to Bob Martin, USDA research plant pathologist.

However, it remains unclear how the virus spreads. It's possible that it is transmitted through a vector, such as an aphid, said Martin. In all likelihood, fruit drop symptoms are caused not by a new virus, but rather a complex of viruses, he explained.

Strik and Wei Yang, OSU extension berry specialist, gave updates about ongoing research on organic blueberry production at Oregon State University's North Willamette Research and Extension Center.

Among other results, plants treated with feather meal fertilizer performed very poorly and were found to have low levels of leaf nitrogen.

To prevent further stress, they were treated with liquid fish fertilizer, which demonstrated better effects in other plants at the site. The distressed plants all recovered from the period of slow growth and leaf discoloration.

Nutrients from the feather meal were probably unavailable to the plant roots, so in the future, the fertilizer may need to be applied earlier in the year.

"We didn't see a fertilizer effect," said Yang. "Maybe the fertilizer we applied takes a long time to mineralize."

Aside from organic fertilizer efficacy, researchers at the site are studying organic weed management, developing an economic analysis of organic blueberry production, and determining the effect of raised versus flat beds on plant growth and other factors.

Yang also discussed a new clamshell container design that reduces moisture loss - and thus extends shelf life - in fresh market berries. The containers are not available to growers because they have not yet been adopted by a manufacturer, he said.