Drought stress continues to be an issue for our landscapes
A multitude of evergreens has taken on an eerie, orangey-brown hue that strikes panic in the hearts of plant lovers everywhere. Needle loss can have biotic (insect, disease, etc.) and abiotic (soil compaction, mechanical damage, etc.) causes, but the rate of mature conifers that have recently begun shedding their needles is most alarming, especially because it encompasses several different species.
Read below for some of the most common evergreen species affected by environmental stressors around Boston.
White pines have traditionally been an ironclad plant in our New England landscapes, more prone to break apart in heavy winter snow than to have an insect or disease issue. However, several years ago mature specimens began browning at the interior, dropping needles and then pushing out the new season’s growth. Years of dry weather began to stress out these behemoths which caused an increased susceptibility to certain needle fungi. A severe lack of precipitation last year caused an explosion in the number of white pines to exhibit decline, specifically along roadways where salt use exacerbated the situation.
Eastern and Carolina Hemlocks
These notoriously sensitive species are shedding needles like the Charlie Brown Christmas tree all across Massachusetts. Drought conditions dramatically increased elongate hemlock scale populations, an aggressive piercing and sucking pest that can negatively impact vigor in relatively healthy trees. Around roadways, in urban environments, or near hardscapes, salt damage is also increasing decline in Eastern and Carolina hemlocks.
Norway spruces suffering from drought have seen a staggering increase in spruce spider mites, spruce gall adelgid, and spruce gall midge populations. The latter two pests have a more irregular pattern to their damage, which blights entire sections of their host plant. Again, the number and frequency of mature specimens suffering disfiguring damage from these pests is staggering.
How can I help my tree recover?
The prescription for restoring plant health should be written on a case by case basis.
- Insect control must be attained before pursuing results by adjusting cultural practices.
- Low nitrogen fertilizer applications are advisable because high nitrogen fertilizers increase tender new tissue which is more susceptible to insect feeding.
- Checking soil composition and microorganisms along with applying a 1-2” layer of mulch can help retain soil moisture levels.
- Gypsum applications should be made to release salt in planting beds impacted by winter salt congregation.
Although crossing your fingers is advisable, it has not actually been proven help plants suffering from these issues.