Freezing temperatures and a heavy dumping of snow are not new to the Yakima Valley. Yakima County Washington State University tree fruit extension agent Dana Faubion said similar occurrances have happened at other times in the past.
Faubion said looking back at the history of the Valley, similar Arctic weather systems can be seen in 1919, 1955 and in 1968.
Despite that fact that cold weather, like that experienced throughout the region last week, is something that has happened in the area before, local crops are still susceptible to damage.
Faubion said at this point in the winter season he is most concerned with the effect the weather could have on soft fruit trees.
He explained that there are several forms of damage these trees can be susceptible to when the temperature drops so dramatically. One way trees can be damaged is when water gets into the tree and freezes, which Faubion said will split the tree open. He said this type of damage results in the dramatic death of trees.
Faubion said another form of damage growers have to watch for when temperatures drop and snow falls is called southwest injury. He explained that what happens is on a sunny day the sun will shine down on fallen snow and be reflected back up toward the tree. This warms the bark of the tree. Faubion said the bark can often get as hot as 60 degrees, however when the sun goes down the temperature of the bark is then plummeted back into the Arctic temperatures.
Although both types of damage can happen when Arctic weather systems come through the region, Faubion said neither occurred in the Yakima Valley last week.
Faubion said the main type of damage he has seen is a severe darkening of the cambium tissue on the trunk of many trees, and he said this is thought to have occurred during the freeze that took place in October 2003. He explained that cambium tissue is the tissue found directly under the bark of a tree. He said the same type of damage was found after the freeze that occurred on Halloween 2002, and no negative impact was found during the following 2003 growing season.
The only other damage he has noticed in local orchards has been centered in the buds and the pencil wood of the trees. He explained that pencil wood is the part of the tree where the crop is located, or the branches of the tree.
He said if local orchardists would like to check their trees for this type of damage all they have to do is take a sharp knife and dissect the bud. Faubion said if there is any brown tissue inside the bud is dead.
The reason it's important to go out and test trees is that depending on how trees fared the cold weather, farmers will have to plan their pruning and heating regimens accordingly, Faubion said. He explained that before farmers prune it's important to figure out what is on the tree. He said if there is a smaller number of healthy buds on the tree it will also affect how farmers plan to heat up and protect the trees from spring frosts.
"Every year we can lose a lot of blooms to frost, but we like to lose those in March," Faubion said.
. Elena Olmstead can be contacted at (509) 837-4500, or e-mail her at firstname.lastname@example.org