I’m only just a beginner… don’t judge me ;-D
© Ilex – Midwestern Plant Girl
Last year’s drought caused Austrian, Scots, and red pines of the Midwest to be susceptible to the Zimmerman pine moth (Dioryctria zimmermani). White, tan, or rust colored resin flowing on the trunk could indicate the presence of the moth’s caterpillar like larva. Finding one or two boring points is usually of no concern. Heavier infestations could cause weakened trees that topple in strong winds, and the tree will act like a nursery for the moths infecting nearby, stressed trees. These heavier infested trees should be removed.
It is critical to understand the life cycle of the Zimmerman pine moth [ZPM] for proper management. The tiny caterpillar over-winters in a silken cocoon-like structure just under the bark. Now, in the early spring, the caterpillars feed on the bark for a week or two, then tunnel into the main trunk, usually in a whorl area. Resin is pushed out by the insect causing a ‘pitch tube’. Fresh pitch tubes are white to tan, the consistency of lard, and have a shiny appearance. Old tubes are yellow to grey, crystallized and hard, with a dull appearance. It is important not be confused by old tubes and new, which all together, may look like an infestation.
In mid summer, the caterpillars pupate either inside the external resin or within their tunnels. At this time, it may be possible to kill the pupa by hitting the resin with a rubber mallet. I love organic cures!
The adults emerge as small grey moths in mid to late August. These moths fly at night and are rarely seen. Females lay their eggs on the trunk under the bark, thus beginning the cycle.
Management of ZPM begins with tree care including proper mulching, watering, pruning, and fertilization. Healthy trees do not get attacked.
Insecticides should be applied during the two vulnerable times in the ZPM cycle. These times are late to mid-April, as the over wintering caterpillars become active, and in August, when the female moth has just laid her eggs and the caterpillars are searching for over wintering sites. Indicator plants for these spray times are when the saucer magnolia is in pink bud to early bloom, or in mid to late summer when panicle hydrangea is pink. Preventive insecticide sprays should be applied as a drenching spray to trunks in mid to late April. Spraying branches and foliage is not necessary & wasteful. Permethrin or bifenthrin are preventative sprays that are available for use by homeowners. Spraying at any other time is inefficient, as it has no effect, and the insecticide may kill predators of the Zimmerman pine moth.
© Ilex Farrell
I had noticed that a couple pines and spruce at work were starting to turn brown in December. They are in a large row on the property line screening us from the funeral home next door. I couldn’t get out to see them earlier, as the snow drifts by them were 3 feet high. Now that finally, all the snow has melted, I took the time to investigate.
As a trained arborist, I learned to assess trees from a distance, then move in for the close up. There are many symptoms that look the same for many different problems. My non-arborist coworker was confident that it was only a lack of water causing the browning of the needles. Nope. With a bit more patience and observation, he too could have seen the signs and potentially diagnosed the problem correctly.
First, let me discuss the difference between symptoms and signs.
Symptoms; An attribute that the disease or pest causes, but is not the disease or pest directly. Needles or leaves turning yellow or brown, leaves wilting, stunted growth, and die-back are all symptoms.
Signs; Is direct evidence or seeing the disease or pest itself. Signs include; fruiting bodies of fungus, chewed leaves or twigs, cankers, galls, and holes in the trunk or branches are just a few.
I was seeing the symptom of browning needles on the trees, but upon closer inspection of the trunks,noticed the signs of pine bark borer in the small holes they left.
The specific symptoms for this pest in the evergreen (although the bug is called pine bark beetle, it does also attack spruce) is that the tree browns from the top down. Many other problem start this way also, but many problems don’t, so I was able to eliminate a good 50% of possible diagnosis.
Upon seeing the multiple small holes in the truck, I didn’t need to go any further with my observations.
Pine bark borer is a small beetle that, in it’s larvae stage, lives just under the bark in evergreens during the winter. It bores tunnels, eating it’s way through the important water transportation system of the tree. Eventually, they damage it to the point the trees can’t get water to it’s needles and it will die. A badly infested tree can not be saved, sadly, even a mildly infested one is difficult to save.
What needs to be done now is remove the trees that have the borer before mid-April. That is the time when the mature beetles come out of the tree and are able to fly to nearby pines and spruces. This adult stage lasts from mid-April through September. If a tree is found with this pest during this window, it should be removed and destroyed (burned, buried or chipped) ASAP.
Generally, this pest only is able to attack stressed trees, and with the drought we had last year, most trees are at least mildly stressed. With that in mind, it is important to try to prevent the spread of the pest to the nearby trees.
In general, the consensus on treatment is to water your trees! It’s that simple. Long story short, think of a hose under high pressure. If you were trying to push something into it, the pressure would push the object out. The theory works for trees, if the tree is full of water, the borers wouldn’t be able to penetrate the bark. If the tree is water-stressed and doesn’t have the pressure to keep the beetles out, you’ll have another infected tree.
Enjoy the day & keep on planting!