Cutting red clover for silage may keep pest at bay

Mitch Lies/For the Capital Press Oregon State University Extension agent Nicole Anderson speaks on crimson clover research at last year's Hyslop Field Day. She reported recently that she doesn't believe the red clover casebearer moth is a pest of concern in Willamette Valley clover seed production.

An agronomic practice of cutting for silage red clover grown for seed may do more than simply providing an additional source of revenue for producers.

It may be disrupting the life cycle of a pest.

Speaking at the Clover Growers Annual Meeting in Wilsonville Feb. 3, Oregon State University Extension agent Nicole Anderson said she has consistently found red clover casebearer moths in Oregon clover seed fields since she and a colleague first discovered the pest in 2012, but she has yet to see any significant crop damage.

“Although we know the pest is here and we know sometimes we have it in numbers that are concerning, we haven’t been able to find significant crop damage,” she said.

The red clover casebearer moth, native to Europe, was first found in North America in the 1960s, when it was found in New York state and Eastern Canada. In 2001, it was reported in Western Canada, where it continues to be a pest of concern.

“It is a big enough problem in the Canadian red clover seed production regions of Saskatchewan and Alberta that their growers have had to stop second-year production,” she said.

In 2012, a Canadian researcher asked Anderson and her colleague to put out pheromone traps to see if the pest was present in Oregon. To her surprise, Anderson said they found the pest in every trap.

Larvae of the pest damage plants by chewing within seed heads and moving from floret to floret. Anderson trapped for the pest in red, white and crimson clover seed fields in 2013, but scaled back to red clover fields in subsequent years after noticing little to no activity in white and crimson clovers.

Trap counts peaked in 2014 before falling back in 2015, possibly due to last summer’s hot and dry conditions.

In all cases, however, whether trap counts were high or low, she was unable to find crop damage of economic significance.

“In general, I think we need to keep an eye out for this and if we see evidence of unusual yield losses, we need to consider this as a source,” she said. “But at this point, we are done looking at it. I don’t believe it currently is a pest of concern in the Willamette Valley.”

After discussing the situation with a leading Canadian entomologist Anderson came to the conclusion that cutting red clover for silage may be disrupting casebearer moth populations just prior to feeding.

In Canada, where the moth is a major economic pest, producers are unable to take off a silage crop in red clover grown for seed due to a lack of heat units.

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