Dying tips on pine trees
A couple of weeks ago, I was asked to look at a pine tree that was declining in health over the past few years.
I looked over the tree and surveyed the site it was growing on. It was situated between two tall houses.
There wasn’t much space between the two buildings and the tree had just about outgrown its spot. The tips of the branches were almost touching one of the houses.
Because of where it was planted, not much sunshine was reaching the tree. It was shaded morning and evening and the rest of the day it received dappled shade from some nearby tall maple trees.
The soil, basically fill-dirt from the original excavation with a thin layer of topsoil, was obviously dry. Whatever grass that was there was thin and spotty.
The pine tree itself had many dead and dying branches. Those symptoms along with its growing site told me it was a classic case of Diplodia tip blight. Trees growing on poor sites are most apt to be infected.
This blight infects older conifers in the 15 - 30 year old range. The tree in question fell within the age range, adding more evidence to the diagnosis.
Nearly all Diplodia tip blight happens in conifers planted in suburban or urban environments. It rarely, if ever, occurs in the wild.
The infection begins during wet weather in spring during the tree’s candle stage (when needles are growing). Spores come from last year's infection that have overwintered in dead twigs, branches, needles and pine cones.
The newly infected buds appear stunted and turn yellow eventually becoming brown as they finally die.
Pruning off infected branches can help slow the progression of the disease to the healthy part of the tree. Since moisture facilitates the spread of the disease, all pruning must be done during dry weather. The fungus can also be transmitted by hitching a ride on cutting tools, so pruners, loppers and saw blades must be disinfected between each cut.
Removing pine cones from the infected branches and under the tree is necessary since they also harbour the spores. All needles must be raked up and destroyed as well.
Watering older trees growing on a poor site during drought will go a long way to help keep the tree vigorous and make it less susceptible to Diplodia.
Three or four sprays of a fungicide will prevent the fungus from getting a toehold. The initial spray is applied just as the buds begin to swell; then once a week through the candle stage. Once the needles are full grown the tree cannot be infected that season. Spraying large trees is best left to a tree service professional.