Cystospora in dabinette

Three Montana orchards located in Darby, Corvallis and Stevensville, were surveyed for cold injury following freezing temperatures in October 2020.  Assessments were made in spring 2021 when trees had started to break bud and damage was clear.  Damage was rated based on % damage to wood ages 1-7 years depending on tree planting date.  Cold injury included die back of tissue at tips to extreme circumstances where the whole tree died to the graft union, other observed damage included cytospora growth and cankers particularly at fruit buds, crotches and on main stem (pictured above). 

In general, while certain cultivars definitively were not cold hardy enough at all locations such as Dabinette and Chisel Jersey, other cultivars like Golden Russett and Ashmaed’s Kernel seemed to do fine if they were older trees (five plus years) as opposed to young (under five years).  Additionally, the slightly warmer temperatures experienced at the orchard in Stevensville seemed to lend protection to cultivars at that location as opposed to colder orchards located in Corvallis and Darby.

A more detailed summary will be provided as more information becomes available, however, below is an intial summary of cold injury in select cultivars at each orchard as well as the minimum temperatures experienced in each location when injury is suspected to have occurred.  Tree age in years is provided in parenthesis following each cultivar listed.

Orchard Location

Minimum Temperature

Cultivars with minimal damage (less than 10%).  Bolded cultivars were undamaged. These trees will be fine.

Cultivars with moderate damage recorded (between 10-50%).  Tree can be saved.

Cultivars with extreme damage recorded (greater than 50%). Tree may need to be replaced.

Cultivars killed to graft union.  Tree will need to be replaced.

Stevensville

10/24/20:12F

10/25/20:12F*

10/26/20: -3F

*Weather station reported using previous days min. temp.

Binet Rouge (5), Hewes Virginia Crab (7+), Major (3 ), Muscadette de Dieppe (7), Wickson (7),Ashmaeds Kernel (6), Bedan (4), Bulmers Norman (6), Harrison (5), Harry Masters (4), Hudsons Golden Gem (7+), Golden Russet (7)

Kingston Black (3)
Chisel Jersey (6)
Frequin Rouge (5)

Corvallis

10/24/20: 6F

10/25/20: -5F

10/26/20: -5F

Binet Rouge (3), Hewes Virginia Crab (5), Muscadette de Dieppe (3)
Harrison Emla 106 (3), Marie Menard (3)
Bulmers Norman (4), Major (3), Harrison G935 (3)
Chisel Jersey (3), Dabinette (3), Golden Russet (3), Roxburry Russet (2), Ashmaeds Kernel (2),

Darby

10/24/20: -1F

10/25/20: -6F

10/26/20: 6F

Hewes Virginia Crab (9), Tom Putt (7), Muscadette de Dieppe (5), Nehou (7), Wickson (7)
Golden Russet (11), Harrison (3), Major (6-8)
 
 

 

This sudden shift in temperature (see graph below) was experienced in many locations across Montana where specialty crops like apples and grapes are grown.  Particularly in the case of cider cultivars which tend to ripen late, many trees still had their leaves on them when temperatures dropped in late October.

 

Temperature changes MT Fall 2020

Graph courtesy of Amy Darling, WARC Vineyard Program Manager.  Corvallis=Blue and Red line, Flathead=Orange, Miles City=Green.