PPDL Picture of the Week
March 19, 2018
Winter injury in
fruit crops
Bruce Bordelon, Professor,
Department of Horticulture and Landscape Architecture, Purdue University
This winter
was significantly colder than normal in the northern half of Indiana. Many
areas north of "I-70" experienced temperatures between -15 and -20˚F
in early January. That is cold enough to cause considerable cold injury to
grapes, peaches, and blackberries. Ten below zero is a commonly accepted
threshold for seeing damage to cold sensitive crops. In Lafayette, we had a minimum winter
temperature of -19˚F on Jan. 2, but also had three other mornings when
temperature reached -17˚F.
We have
evaluated fruit crops at the Meigs Horticulture Research Farm in Lafayette and
found considerable injury. Peach flower buds appear to be 100% dead. (Fig 1).
Most blackberry cultivars appear to be severely injured, but raspberries appear
to be fine (Fig 2 and 3). With brambles, damage occurs to the cambium in the
canes rather than the buds. Sweet cherries have some minor damage, but should
have plenty of live flowers for a full crop (Fig 4). Apples are cold hardy and
seldom damaged. I only checked Golden Delicious and the flower buds appear to
be fine. (Fig. 5). And finally, I looked at a few paw paws and found some
injury to their flower buds as well (Fig 6).
Injury in
grapes depends largely on genotype (cultivar). Cold hardiness varies greatly
among commonly grown cultivars. In our trials, several cultivars have more than
50% primary bud injury (Fig 7). These include Chambourcin (45% live), Noiret
(32% live), Cayuga white (23% alive), Traminette (21% live), and Vidal (18%
live). Super cold hardy cultivars like Brianna, Frontenac, Marquette and
LaCrescent are 80-95% live. The popular backyard grape cultivar Concord has 73%
live buds. Fortunately, grape growers can adjust pruning severity to make up for
damaged primary buds. Once the extent of cold injury is determined, a grower
can decide if they need to adjust pruning severity. By leaving extra buds to
account for those damaged, a full crop can be produced.
Even though we have seen significant damage in our area,
that doesn’t mean there won’t be a crop of fruit at your local orchard. For
instance, I checked peaches in the Goshen area recently and they looked fine. Peaches
are seldom grown in regions where cold injury is likely. That’s why most of the commercial peach
orchards in Indiana are in the far southern counties along the Ohio River, or
near Lake Michigan in the northern part of the state. Even if there is
considerable injury, it only takes about 10% of the flowers to produce a full
crop of peaches. Many blackberry growers are using a rotating cross arm trellis
and cover the plants over winter. This is a year that will test that system.
The plants I saw in Goshen looked healthy. Hopefully there will be a good crop
of all your favorite fruits this year. Let’s hope we get past spring frost
damage.