Plant Pressures

Plant Pressures

Current Conditions

The last couple of weeks in June were dry across the region, receiving only a fraction (0.05 inches) of the average expected rainfall for the month. July began with a  couple of downpours and thunderstorms across the region as we experienced the outskirts of Hurricane Arthur. Daytime high temperatures have been seasonal, with the humidity increasing and hanging around as we get into the doggier days of summer. Excessive heat can be stressful for plants, rainfall and humidity, although uncomfortable and inconvenient help mitigate that stress. Soil temperatures are in excess of 72 degrees and plants can quickly succumb without proper watering and maintenance, carefully monitor your landscape for signs of heat stress and water appropriately. Plants in bloom currently include, but are not limited to; Kousa dogwood, butterfly bush, Catalpa, mountain laurel, Rosa rugosa, cinquefoil, inkberry, various species of hydrangea, Stewartia, American elderberry, some species of Spirea, Clematis, honeysuckle and many herbaceous plants. Of course as the growing season continues so does the potential for disease and pest issues, some previously discussed diseases continue to plague the landscape while others are in varying life cycle stages and new ones are presenting. Discussed below are just a couple of diseases and/or pests recently reported as active, it is not an all inclusive list, consult with your arborist if you have concerns about your landscape plants, treatments and preventative cultural measures you can employ.

Disease Distress

Boxwood psyllid damage

The boxwood psyllid feeding will result in cupping of this year’s foliage. White, powdery residue may be visible on young leaves and shoots. The plant may be able to outgrow the damage if addressed in a timely manner.

The boxwood psyllid is a common pest of ornamental boxwoods and is capable of infesting all species.

The boxwood psyllid is a common pest of ornamental boxwoods and is capable of infesting all species. They only produce one generation per year, insects overwinter laying orangish eggs in between bud scales. Nymphs hatch early in the season and a white, waxy substance thought to protect them can cover the plant and can be detrimental to plant health.


Fire blight on crabapple.

Fire blight can be caused by bacterium or fungus. It can produce cankers such as this one pictured which may require pruning in order to aid in the tree’s success. If you see something like this on your property contact your arborist to discuss treatment options.

Flagging due to fire blight.

Fire blight caused by the bacterium Erwinia amylovora will produce blackened, curling tips on young shoots and turn this year’s leaves brown.