Disease Diagnostics

Disease Diagnostics

Current Conditions

In the past couple of weeks the weather has fluctuated from mild, seasonal temperatures with about an inch of rain, then more recent cold, wet snap and back to summery feeling highs.  Seasonable day time highs, during the sunny period, and consistently cool night time lows along with the accumulated rainfall overall have been adequate for plant growth. The slow pace of spring development has caused extended, overlapping bloom periods, azaleas and rhododendrons are particularly spectacular right now. Lawns have greened up and mowing season is in full swing. On average 213 growing degree days have been added so far this season, and the soil temperatures have reached an average of 61 degrees. Of course as the growing season continues so do the potential problems, diseases have developed or are presenting in new life cycle stages. Discussed below are several currently being reported as active, this is, by no means, a complete list so make sure to contact your arborist with any questions, concerns or treatment needs.

Disease Dilemmas

Plant diseases may have many life cycle stages and multiple hosts so they may present differently in the late spring or early summer as air and soil temperatures rise and days grow longer and sunnier.  These complex life cycles, morphological stages and multiple hosts can  make identification and treatment tricky. Discussed below are some diseases which currently active. Your arborist will be able to properly assess disease on your landscape and recommend treatments and/or preventative measures.

anthracnose - silver maple

Anthracnose is beginning to present on maples and sycamores. Angular, wet looking lesions along the primary vein on leaf surfaces is an indication that this disease is present. Damp, mild weather is very conducive to the development of this fungal disease.


Phomopsis shoot blight is beginning to be visible on mature junipers and spruces, especially those in full sun. Branch tip die back will be very noticeable at the top of canopy or the top most branches, while the rest of the canopy appears relatively healthy.

dothistroma dead tips and ooze'

Red band needle blight appears as winter burned needle tips on white pines, with Asian varieties being the most susceptible. Premature needle shedding will be visible on the lower canopy of affected trees.

sphaeropsis tip blight on ap2

Diplodia needle blight would not normally host on 5-needle pines (eastern white pine, bristle cone pine, Korean pine, Japanese white pine etc.) but it can be very destructive when it does. Brown stunted shoots with brown needles is an indicative symptom of this fungal disease.