Farewell, Old Spruce

Our observant readers probably noticed something unusual in the photo accompanying the last post. As is my custom after the first mowing, I included a photo of our yard that showed an empty spot where we used to have a spruce tree. I had to make the painful decision recently to remove that tree, and I hope my experience can help someone else avoid the loss we've endured.

About a year ago I noticed some brown spots on a few branches of the tree, but since they were high in the crown and limited in number I didn't give them much thought. The brown sections grew in size and number over the next few weeks, prompting me to investigate more closely. Although the image below was taken this spring, the general appearance of the tree approximates what I observed early last summer.

On closer observation I found small clusters of dead needles hanging from the defoliated branches. The needles were held together by silky thread surrounding a small, black worm that would actually navigate a tree branch collecting needles for its cocoon. One could detach these worms from the tree with a slight pull near the base of the cocoon, so I spent most of one afternoon pulling worms off my tree. Unfortunately, many branches had already been defoliated, and although I removed hundreds of worms, there were still hundreds (if not thousands) of worms remaining, destroying more needles every day.

A little online research identified the pests as a bagworm that feeds on both evergreens and deciduous trees, but since spruce trees don't regenerate their needles, the damage to conifers is more noticeable than when these pests attack deciduous trees. My only consolation was the fact that the worms finished stripping branches by mid summer. The males emerge from the cocoons in a few weeks as a moth to fertilize the females that remain in their cocoons, and the fertilized eggs remain in the cocoon until late spring the next year.

This image from a few weeks ago shows several cocoons that had remained intact through the winter, some of which may have contained eggs ready to hatch into thousands of worms this spring. I removed a few hundred of these nests before I gave up. The tree was already badly damaged, especially in the crown, and if only one nest remained unpicked, I would have hundreds of worms to deal with by early summer. Since I have another spruce about 50 feet from this one from which I've already removed a handful of cocoons, I decided to destroy the damaged tree in an attempt to arrest the spread of the bagworms.

Even though I felt my options were severely limited, the decision was still hard. I considered the tree an exemplary specimen of its genus, and enjoyed watching it grow larger each year. The image above from December 2013 shows the beauty of both the tree and the snow, in my opinion. Ironically, there were obviously bagworm cocoons in the tree when this picture was taken, since the worms showed up just a few months later. That winter was also the coldest we've had here in recent memory, which doesn't offer much hope that cold weather might kill off the bagworms.

I vaguely recall seeing a few cocoons on this tree in 2013, but they didn't excite enough curiosity in me to cause me to investigate. Now that I recognize bagworm cocoons, I won't delay in acting in the future. Hopefully others will learn from my experience and will save their trees before it's too late.

First mowing of 2015

Spring growth was pretty minimal this year until about a week ago. Suddenly, trees are flowering, budding, or leafing out, and the grass is not only green, but long enough to cut. Although the yard could have waited a few more days for the first cutting, the weather on April 18 was well suited to mowing. It was evidently well suited to farming also as farmer neighbors in the two fields adjacent to our property were both out working, one planting corn in the field to the north, and the other performing a second fine tilling operation in preparation for planting in the field to the west. Although I'd seen tilling in other fields in the area earlier in the season, I hadn't noticed much planting until the 18th.

Time will tell how many more times we'll mow before the season is over, and I'm sure I'll tire of the experience at least once before next winter, but for now I'm glad to see green growth again!

Central Illinois Winter Temperature Summary, 2014-2015

Now that winter is officially finished, we can look back at the temperature data and compare reality to what we remembered. I think everyone here in Central Illinois perceived our latest winter to be warmer than the one before it, but prolonged cold (and warm) spells have a way of making comparisons difficult from year to year. The data is presented again this year in the form of combined bar and line charts. The blue bars represent the deviation of the daily mean temperature from the historical average where each bar represents one day. The red curve represents the cumulative deviation from the historical average, and indicates whether the season as a whole was colder or warmer than what we'd typically expect.

The first observation I'd like to bring to your attention is the value of the red curve at the right side of the chart. Including data from March 20, the cumulative deviation from average was -3 degrees. That's almost as close to "normal" as one can get. That means, on average, the daily mean temperature was about 0.03°F colder than the historical average each day. That's a temperature difference most of us can't perceive. It's also probably a smaller number than the error in the measuring equipment at the National Weather Service in Peoria, not to mention the fact that the daily mean temperatures I use are reported as integers that have already been rounded a fraction of a degree each day.

It's also interesting to note that the winter as a whole was warmer than normal until the last week of February, indicated by the red curve crossing the x-axis into negative territory on February 26. February 27 added momentum to that move by recording the largest deviation from average of 28 degrees F below the historical mean. The deviation of 23 degrees F above normal on March 23 recorded the largest deviation on the warm side.

By comparison, we can look again at the data from the winter of 2013-2014 and notice that the cumulative temperature that winter was above normal only a few days all season. I think most of us are happy not to repeat those temperatures this year.

To illustrate just how unusual our temperatures were last winter, I've plotted the cumulative deviation curves for both winters on the same scale on this chart. In both cases, February contributed the largest cumulative degrees below normal, but this year a significant warming trend began on March 7 that carried through the end of the season. Another significant difference this winter was the 18 consecutive days of warmer than normal temperatures beginning on January 15. Those days averaged 10.5 degrees above normal and contributed greatly to counteracting the colder than normal periods.

Since our historical mean temperatures are still low enough to expect heating degree days this time of year, we are technically still in our heating season. We'll continue to compile data to see whether this heating season as a whole was warmer or colder than average.