Taking an environmentally sensitive approach to pest management
We Midwesterners have painful memories of the "Easter Freeze" of 2007, when temperatures suddenly flipped from 20 degrees F above normal in late March to 20 degrees below normal. Most trees and shrubs had significant new growth, with the cold hardiness of tomato plants, when the temperature plunged to the mid 20's for several days. Flowers and shoots turned to mush and there was significant damage to bark, leading to more dieback as the season progressed. Many of us are still pruning our Japanese maples to bring them back to their former glory. Unfortunately, the current season has, so far, set our woody companions up for a similar disaster.
Overall, the winter of 2011 has been mild, ranking in the top 5 mildest on record in Missouri. The foliage on the southern magnolias on MU campus is bright green, showing none of the browning that we see near the end of a more typical winter. However, since plant development is approximately two weeks ahead of normal, with above normal temperatures predicted over the next week, there is a high probability that we will see some damage before we reach the frost free date in May. A quick review of weather extremes in Missouri reveals that we are, by no means, out of the wintery woods. On March 12, 1948 the minimum temperature was -4 F. In 1997, on the date of Easter for this year (April 8), the temperature dropped to 24. A similar temperature on Easter of 2012 for more than a few hours would cause serious injury to woody plants.
Woody plants have an amazing ability to tolerate temperature extremes if changes occur slowly. Even after our current warm spell, freeze damage from a cold period would be much less severe if we had gradual cooling to more normal temperatures before the freeze arrived. The good news is that trees and shrubs can usually recover from even severe freezing injury with good cultural practices like pruning, mulching, irrigation during drought and judicious fertilization (don't over-fertilize stressed plants). I would not, however, be sleeping very well if my livelihood depended on a crop of peaches. There may be slim pickings this year.
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REVISED: September 29, 2015