Researchers target fungus that attacks tree fruit, nuts
upper roots and tree crown is kept fairly moist through the entire growing season. “Most infected orchards have been found in the North Coast with fewer in the Sacramento Delta,” the guide- lines added. “Most affected orchards are on sandy loam to loam soils along streams or rivers originally lined with native oaks.” The disease can show itself as a grad- ual decline of trees in a circle extending out from the center or may result in the sudden collapse and death of trees that appeared for years to be healthy. The native oak root fungus pathogen is
already inmuch of California’s soil, even before susceptible tree fruit or nut crops are planted. “If an orchard is planted on a site where oak, black walnut or willow trees once grew, chances are very high that the inoculum already exists in the soil on old decaying roots,” according to the UC guidelines. Once an orchard is infested with ar- millaria, farmers can limit the spread by machinery or slow the damage through irrigationmanagement, but there is no re- liableway to rid ground of the pathogens.
ByBob Johnson Pear growers may be one step closer to having an answer for a widespread fungus that grows and survives for de- cades in wooded soils while waiting to attack tree fruit and nut crops with dev- astating impact. Armillaria, commonly known as oak root fungus, is a native pathogen that survives invisibly on deadwood and root material deep beneath the ground until new trees are planted, and then it can spread, causing wilt and decline. A recent University of California, Davis, study has developed protocols that will let researchers and plant breeders more quickly detect whether a pear rootstock is resistant to themost lethal strain of ar- millaria, at least in the lab. “There is no pear rootstock known to be resi stant to armi l lar ia,” said Carolina Tweedy, the UC Davis grad- uate student who adapted an in vitro technique for screening armillaria re- sistance in pear rootstocks. “This limits options for replanting trees in infected orchards. Due to the broad host range of armillaria, other tree crops face a similar challenge. In order to identify sources of resistance to be utilized in rootstock breeding programs, a rapid and reliable screening technique for pears is necessary.” Many pear varieties were considered resistant or at least tolerant of armillaria, but changes in irrigation practices may be creating conditions that encourage the disease. The switch from flood or furrow ir- rigation to sprinklers that keep the top of the soil and upper roots moist more often may be the reason armillaria has become more of an issue in pears in re- cent years.
“Armillaria root and crown rot most often occurs when the soil is cool and moist,” according to UC pear pest man- agement guidelines. “Recent infections of armillaria root rot in pear orchards may have been caused by a switch in irrigation practices from flood or fur- row irrigation to permanent under-tree sprinklers where water is applied more frequently and the soil layer close to the
See PEARS, Page 13
This revolutionary fungicide delivers unprecedented performance against difficult‑to‑control, yield‑draining diseases, including Botrytis and powdery mildew. And it’s fully charged with power, spectrum, and stamina. That means a healthier crop with a higher yield potential. Talk to your local Syngenta representative about how Miravis ® Prime can give more power to your grapes. Performance with more power.
www.californiabountiful.com
A Farm Bureau Production
KVPT/18
Fresno
Sun. 11:30 a.m.
KSBW-ABC/8.2
Monterey/Salinas Sun.
6:30 p.m. 6:00 p.m. 6:30 p.m. 5:00 a.m. 9:00 a.m.
KOVR/13
Sacramento San Francisco
Sat. Sat.
KGO/7 KSBY/6
San Luis Obispo Sun.
RFD-TV: Dish Ch. 231, DirectTV Ch. 345 Sun.
8:00 a.m.*
*Times listed are Pacific Time
©2020 Syngenta. Important: Always read and follow label instructions. Some products may not be registered for sale or use in all states or counties. Please check with your state or local extension service to ensure registration status. Miravis ® , the Alliance Frame, the Purpose Icon and the Syngenta logo are trademarks of a Syngenta Group Company. All other trademarks used herein are the property of their respective company. MW 0BEG02256-GRAPES-AG178 05/20
Now trending
@cabountiful
August 11, 2021 Ag Alert 9
Powered by FlippingBook