These black spots can merge and create papery, brown-to-black patches on the head. Upon harvest, farmers must peel and discard the leaves to remove the patches, resulting in smaller heads that command less money.
Iceberg lettuce is a type of lettuce eaten in America. Nearly all of the lettuce consumed in the US is produced domestically. Two states, California and Arizona, produce over 90% of the country’s commercial lettuce.
Occurring on leaf and head lettuce varieties, BLS thrives in wet, cool conditions. It is most serious in early spring and late fall, when it is most likely to rain in California.
BLS is difficult to prevent because the disease is highly dependent on weather conditions. Farmers can spray their lettuce crops with pesticides, but the chemicals have to be applied before symptoms develop, which is impractical. Because BLS is sporadic and unpredictable, these preemptive sprayings would be unnecessary in most seasons and lead to increased production costs. Therefore, according to ARS geneticist Ryan Hayes, creating disease-resistant breeding lines is the most efficient and cost-effective tool to manage BLS in lettuce.
Hayes, along with geneticist Edward Ryder (now retired) and plant pathologist Carolee Bull, developed the seven new breeding lines. Similar in appearance to Salinas’ variety created by Ryder, these lines are the first western shipping-type icebergs with commercially useful levels of resistance to BLS. ARS provides these lines to seed companies, which in turn use them to develop new iceberg varieties for commercial use.
Limited samples of seed from these breeding lines are available from the ARS unit in Salinas to researchers and seed companies.
