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Berries, Late Blight

Posted by | March 11, 2009

“Debugging” Berries

Berries are big in Washington state. Washington farmers grow the majority of the nation’s red raspberries, producing up to 70 million pounds yearly on more than 10,000 acres. The state’s growers also produce nearly 13 million pounds of strawberries and 14.5 million pounds of blueberries every year. Altogether, the state’s small fruit growers represent a more than $100 million industry.

As news reports continue to tout research proving the health and antioxidant benefits of berries, consumer demand continues to grow.

To meet the demand with attractive high-quality fruit, growers need science-based tools to effectively control the weevils, mites, aphids and other pests that feed on the roots, plants and fruit, especially as some traditional pesticides are phased out.

At WSU’s Northwestern Washington Research and Extension Center in Mount Vernon, entomologist Lynell Tanigoshi and his team are working on new approaches using integrated pest management and a new generation of highly targeted insecticides with low use rates. His small fruit arthropod programs, begun in 1995, focus on developing management tactics that integrate IPM and timed pesticide applications for optimal control and cost effectiveness while minimizing the development of pesticide resistance.

“There are some exciting developments in terms of our research in using beneficial predatory insects and mites to control pests, and in terms of targeted new pesticide chemistries that are proving effective and safer to beneficial arthropods,” Tanigoshi said.

Recent and pending registrations of new targeted and selective pesticides for blueberry, strawberry and caneberries are resulting in improved tactics that combine timed chemical control with the conservation of natural enemies to control root weevils, western raspberry fruitworm, leafrollers, aphids and spider mites.

Washington’s small fruit growers represent a more than $100 million industry.

WSU entomologist Lynell Tanigoshi

For more information on small fruit horticulture at WSU, please visit:

Early Warning System for Late Blight

An early warning system developed about 15 years ago at Washington State University is helping protect the state’s $685 million potato industry from late blight, a disease caused by a fungus-like organism involved in the 1845 Irish potato famine.

The disease, which causes potatoes to rot, is spread by spores from infected tubers left in the ground from the previous harvest, cull piles, infected seed potatoes or volunteers. The spores can be dispersed by wind and rain when springtime weather conditions are favorable.

“The reason why late blight is so important to forecast is that it can spread very rapidly over a large geographic region,” said Dennis Johnson, a WSU plant pathologist. “It only takes one or two infected potatoes to start an epidemic.”

The good news is that the disease can be controlled with timely applications of fungicides. That’s where the late blight hotline, field observations and a computer model developed in the early 1990s by Johnson and Richard Alldredge, a statistician at WSU, come into play.

The model calculates late blight predictions based on two variables: inoculum potential and number of rainy days in the early spring.

Field persons, who scout potato fields during the growing season, alert Johnson when they see signs of late blight. “If they are not sure what it is, they will send me a sample to confirm a diagnosis, or I’ll go and take a look at it,” he said.

The warnings are made available via a 1-800, toll-free telephone number. The message may be changed daily when circumstances warrant. The number may receive 1,100 and 1,800 calls during the growing season.

When conditions change dramatically and growers must take immediate action, warnings are distributed to growers by the Potato Commission via e-mail. Information is also posted on a website.

Late blight is not a pretty sight. Potatoes infected with late blight are shrunken on the outside, corky and rotted inside.

For more information on potato pathoogy at WSU, please visit: