Plant Doctor

Good Morning!  I have been blogging lately ad nauseum about pant diseases, and pests in gardens this year.  So today I thought I would post some pictures of some of the diseases I am seeing everyday out in gardens in the Chicago area.

The boxwood hedge pictured to the left is showing signs of phtophyora root & crown rot.  This Springs weather is perfect for these diseases.  Phytophthora cinnamomi and P. parasitica are water mold, fungus-like microorganisms favored by waterlogged conditions and warm weather.  Irrigation scheduling that promotes prolonged soil saturation can encourage disease development. fair warning, the disease can be can be carried in recycled irrigation water.  Sypmtoms include, foliage wilting and turning gray-green to bronze to a dry brown color. Whole sections of the plant may dry and brown as the disease progresses. Roots become brown and water soaked. The cortex is rotted and falls off all but the larger roots. A chocolate-brown to black color develops from roots into the root crown and may extend a few centimeters above the soil. Infected plants generally die.   There is no chemical solution.  Fungicides can help prevent the disease.  The best thing you can do to help prevent this disease is to control your irrigation.    Should you lose boxwood to this disease DO NOT replant boxwood in that area as the fungus will remain in the soil.

The daylilly pictured next has classic crown rot.   Crown rot in generally caused by a fungus.  When plants are stressed by the combination of the stress of blooming and high heat and humidity the can be susceptible to crown rot.  Our weather in Chicago has been perfect for this disease.  Be on the look out for perennials that are yellowing and flopping over.  They may also be soft/slimy and they will smell like they are rotting.  Try sprays that have an anti-bacterial and/or fungicide.

Powdery mildew is another common plant disease that favors hot humid conditions and is exacerbated by planting plants in tight clusters.  Spacing plants and keeping plants properly pruned can help keep the disease under control.  As can good garden hygiene. Clean up any fallen diseased leaves in the garden to help keep it from spreading. Fungicides are helpful in managing the disease.  Fair warning, not all fungicides will work universally.  Read the label to make sure you are buying the right fungicide for the right plant.

The next picture is of Black spot, a disease commonly found on roses.  To help prevent and control black spot water your roses from below and in the early morning hours.  Cleanup any fallen leaves from under your roses.  Remove already diseased leaves to prevent it from spreading.  Use Ortho rose spray to help control it during the growing season.  Sulfur powder will also help keep it from spreading.  A dormant oil applied in Winter will also help.

The rose pictured next has Bortrytis.  These

infections are favored by cool, rainy spring and summer weather usually around 60 degrees.  Gray mold can be particularly damaging when rainy, drizzly weather continues over several days.   Again keeping the garden clean is your best form of prevention.  Should you see this disease dispose of any infected petals or leaves and treat with a fungicide.

Yep, 2010 the year of the garden plagues....

Good Luck my friend and Happy Gardening!