Down the Garden Path

Since the drought of 2012, Austrian pines have been stressed, especially older trees. Austrian Pines are not native to Illinois, coming from western Europe into Asia, including Austria for which the tree is named. While tolerant of our weather pattern when young and growing well, Austrian Pine becomes more stressed as the years go by.

The past two years a fungal disease called Diplodia Tip Blight has really hit them hard. Diplodia attacks the new growth, killing it before the candle even has a chance to expand. You can see trees impacted by Diplodia as you drive through the neighborhoods. You will see more infection lower on the pine than in the upper canopy usually. The newly killed candles will have a bright tan or straw color to them. Older needles will be covered with small black picnidia, a sign of the infection. These are the fruiting bodies of the fungus. Besides finding the very small black pinhead-sized fruiting bodies on the needles, they can and will be found on the pine cones too. As the disease progresses all needles will be killed, resulting the loss of entire branches.

If you have younger Austrian Pine in your home landscape, preventing stress goes a long way in preventing the fungal disease. Watering during dry periods and not just during a prolonged drought will supply the pine with good amounts of soil moisture. Consider a 2-3-inch-deep mulch extending out a foot or so past the drip line to conserve soil moisture and keep the ground cooler will also help.

Once the disease is present on older Austrian Pine, cultural management practices are really important. Diseases branches, branch tips and cones will all promote the disease in future years so pruning is critical. Removal of any dead wood is not harming the pine. By removing dead wood, diseased needles and pine cones, you are reducing the inoculum for future infections. If there are parts of a branch that still healthy and parts that are diseases, prune back at least 6-8 inches from the disease portion.

Part of your sanitation efforts have to include sanitizing your pruners or saws between cuts so you're not spreading the disease. Another practice is to only prune in dry weather, lessening the spread of the fungal pathogen as well.

It is too late for any fungicide treatments this year, so plan ahead for next year. Be sure Diplodia Tip blight is listed on the label. There will be three sprays during the spring of the year and timing is everything. The fungicide spray will need to be applied when the buds are swelling, again as the new needles just begin to emerge and the third time and 10 to 14 days later. The first two sprays are timed on how quickly the pine goes from bud swell to when the needles begin to emerge. You only use the calendar to count the 10-14 days for the third spray treatment.

Consider treatments for those pines critical in the landscape. Even with treatments, older pines may not recover.