Plant and Insect Diagnostic Clinic Update – May 24, 2019

In my previous clinic update, I warned you about inspecting your plants before purchasing. I found an excellent example of what not to buy at a plant sale. The plant had virus symptoms restricted to some leaves.

Vegetative propagation is a great way to keep your plants healthy when clumps are getting too thick in the garden, but it becomes a way that plant pathogens and pests move around. Always keep your eye peeled for symptoms that may indicate a problem, and do not propagate those plants nor buy symptomatic plants that will introduce a problem in your garden.

 

When purchasing flowers, avoid plants that have abnormalities and unusual symptoms. In this case, the color break is caused by a virus.
When purchasing flowers, avoid plants that have abnormalities and unusual symptoms. In this case, the color break is caused by a virus.

 

Broadleaf trees

We received several inquiries of ash dropping leaves. Leaf drop can be caused by fungal pathogens including those that cause anthracnose

ash anthracnose symptoms
Ash anthracnose symptoms.

See other potential suspects in the publication Common Problems of Ash Trees. We recommend you monitor these trees, and if symptoms worsen over the summer, get in touch with us at the clinic if you are looking to test for vascular wilts.

As trees continue to slowly leaf out, you may notice growth in the branches, some possibilities include Oak phomopsis galls and insect galls

We continue to see the aftermath of harsh winter temperatures on chokecherries and burning bush. In Chokecherries (and other Prunus) the limbs or trunk affected by low temperatures resulted in tissue death. Then white rotter mushrooms move in to decompose the dead wood — more information on a previous update in this article. Several questions have reached us about burning bush (Euonymus) not leafing out fully at this time. We recommend monitoring the bushes until mid-June, then prune off dead limbs only.

We continue to receive questions about the impact of the flooding, and how saturated soils may affect trees and plants in general. Cottonwood, sycamores, and silver maples are good examples of trees that are adapted to flood planes, and they can tolerate these types of conditions.  On the other hand, an example of plants with little tolerance to wet soils include bur oaks, hard maples, and junipers; those may suffer under wet conditions.

Perennial and annuals

Jack-in-the-pulpit rust

Symptoms caused by the fungal pathogen Uromyces are-triphylli, like other rusts, consist of small yellow pustules (spot like) that contain fungal spores. These spots enlarge and turn bright yellow-orange as they mature. Rusts are minor diseases of plants and won't result in plant death. This pathogen only infects jack in the pulpit and two related plants: green arrow arum (Peltandra virginica) and green dragon plants (Muricauda dracontium). Fungicide treatments are not recommended since the damage is cosmetic.

Jack-in-the-pulpit rust symptoms
Jack-in-the-pulpit rust symptoms.

Jack-in-the-pulpit close up of the fungal pustules where rust spores are produced.
Jack-in-the-pulpit close up of the fungal pustules where rust spores are produced.

Columbines- sawfly

Last week we had a hot day on 5/16, and insect continues to become more active. See these sawflies munching on columbines on that day! learn more about sawflies on this article from U. of Minnesota

Note the sawfly larvae eating the edges of the columbine leaves.
Note the sawfly larvae eating the edges of the columbine leaves.

Issue: 
Authors: 

Lina Rodriguez Salamanca Extension Plant Pathologist and Diagnostician

Dr. Lina Rodriguez-Salamanca is an extension plant pathologist and diagnostician with the Iowa State University Plant and Insect Diagnostic Clinic  (clinic.ipm.iastate.edu), a member of the National Plant Diagnostic Network (NPDN,&nbsp...

Links to this article are strongly encouraged, and this article may be republished without further permission if published as written and if credit is given to the author, Horticulture and Home Pest News, and Iowa State University Extension and Outreach. If this article is to be used in any other manner, permission from the author is required. This article was originally published on May 24, 2019. The information contained within may not be the most current and accurate depending on when it is accessed.