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Thursday, Apr. 28, 2016

Extension Line

Wednesday, March 24, 2010

Last week we discussed the damage being done to the landscape plants in our yards by rabbits and deer. Below are excerpts from an article that crossed my desk from Paul Domoto, Iowa State University Extension Fruit Specialist, that discusses other damage to our fruit crops because of the severe winter.

This winter is going down as one of the snowiest on record and has far surpassed the record for consecutive days with snow cover on the ground. These accumulations of snow are good in moderating soil temperatures and protecting plants under the snow from exposure to extremely low air temperatures. However, the presence of snow cover that has accumulated and the spring thaw that will inevitably occur can present several problems to the various fruit crops grown in Iowa. These problems include diseases, wildlife, and the physical weight of the snow accumulation.

Over-wintering diseases. With the snow cover, diseases that over-winter on leaves, such as leaf spot, leaf scorch, and powdery mildew on strawberries, downy mildew on grapes, and apple scab will be more prevalent this spring. This is because fewer leaves have blown away and temperatures under the snow are more favorable for their survival. Leaf scorch in strawberries can continue to develop beneath snow cover at temperatures between 37 and 25 degrees F. With greater carryover of inoculums, early season disease control will be important to keep diseases under control.

Soil borne root rots. With a prolonged snow melt, there is a good chance that soils will be saturated for extended periods of time and create conditions conducive for the development of soil borne root rots caused by Phytophora, Pythium, or Verticillium wilt, particularly when they have been planted on soils that are not well drained. Symptoms of these diseases will first appear as reddening of the young leaves followed by stunted grown and plant decline. Fungicide drenches are available for Phytophora, but not for Pythium or Verticillium wilt. Proper site selection with a well-drained soil and planting resistant cultivars (when they exist) are the best solutions for controlling soil borne root rots.

Breakage. With the heavy snow pack that has accumulated, especially in areas with high drifts, there is a risk of limb breakage in fruit trees; and pulling of canes from trellises, staples giving out, and wires breaking in grapes. As snow melts, it becomes harder and heavier near the surface. This puts greater strain on tree limbs covered by snow and pulls any trapped grape canes downward as it settles. Where limbs and canes are trapped in the snow, breaking the surface crust above the limbs and around the canes will help to lessen the load, but can be time consuming. Consider doing it on the deepest drifts.

Frost heaving. Frost heaving should be a minor concern for strawberries this spring. However, a special set of circumstances may cause frost heaving to occur. For it to occur, the snow has to have melted, the soil remains saturated, and temperatures drop low enough to re-freeze the top few inches of soil. Evidence that frost heaving has occurred would be strawberry crowns laying on the soil surface with many of their roots exposed. This is more likely to happen in areas of a field that are poorly mulched and lack good internal drainage. The best protection against frost heaving is planting strawberries on well-drained sites.

Being aware of potential problems should assist homeowners in being proactive with maintaining the health of plants in their home landscape. If you have any questions feel free to call your local County Extension Office. The phone number for the office in Cherokee County is 712-225-6196. You can also call our Horticulture Hotline phone number at 515-294-3108.