Clinic Update: Spring Samples Submitted to the Plant Diagnostic Clinic

Spring is progressing rapidly, and we are beginning to see more samples in the extension plant diagnostic clinic. What follows is a description of what we have received in the past several weeks.

Many of our samples received this spring have been from woody trees and shrubs, especially various conifers and evergreens. Some of these samples appear to be weather related damage.

Spruce and yew samples displayed dieback that could be traced back to points where partial branch breakage occurred, and areas where it appears snow and ice remained on the branches for extended periods of time.

Some young Norway spruce trees planted last fall came into the clinic dropping needles and with saturated heavy clay soil surrounding rotted roots. While Pythium root rot was present, it appears the newly planted trees were in a poorly draining spot, and snow and ice melt last winter as well as heavy rains this spring may all have contributed to the problem.

Healthy white pine next to a tree with severe decline symptoms. Photo courtesy of Rosie Lerner. Purdue Extension

We have also had some white pine samples that appear to be suffering from white pine decline (thinning canopy, yellow or brown foliage, needle drop). As in the past, these are challenging samples that can take a lot of time. In some cases root diseases such as Leptographium, Armillaria or Phytophtora have been found, and we’ve found pine-wilt nematode in a few samples in the past, but many of the samples we have received this spring have not included root material, and the problems may be related to environmental stress and poor site conditions. More information on white pine decline can be found at:

• http://www.ppdl.purdue.edu/ppdl/weeklypics/8-16-04.html.
• http://hyg.aces.uiuc.edu/secure/subscribers/199902f.html

Some other tree samples we have received this spring have included a Jeffrey pine with brown spot needle blight (a disease we often see on the more common Scotts or Ponderosa pines). A juniper with dying branches had Botryosphaeria canker. A Washington hawthorn had cedar quince rust galls causing the twigs to die. A Japanese holly with a leaf scorch and leaf drop had black root rot when the roots were examined. A young maple with a large canker running up the trunk had Schizophyllum sapwood decay. Finally, tiny orange flies flying around several boxwoods were found to be boxwood leafminer adults, laying eggs.

When collecting samples from trees and shrubs, it is important to remember that it is difficult to diagnose from completely dead, dried out branches. If possible, select branches that show symptoms, but have not completely died. In some cases it is helpful to submit root material as well. You can contact the clinic for instructions on what to submit for various types of problems.

We have also received several greenhouse samples. Earlier this spring we had high-tunnel tomatoes in cold, wet soil infected with Pythium root and stem rot. We also diagnosed Pythium root and stem rot on hydroponic basil. Several tomato samples have already been submitted with herbicide injuries. Injury from 2,4-D applications seems to be most common. It is important to remember that tomatoes are very susceptible to injury from nearby applications.

I have also looked at several geranium samples with edema. This disorder generally occurs in the greenhouse when the plants are kept wet in a high humidity environment during cloudy weather. More information on edema can be found at: http://www.ces.ncsu.edu/depts/pp/notes/oldnotes/gp3.htm.

Other greenhouse samples have been fertility issues. Because the plant diagnostic clinic is part of the Soil Testing and Plant Diagnostic Service Laboratories at MU, a sample submitted to the diagnostic clinic with symptoms of nutritional problems can be easily directed to plant tissue analysis lab when a client wishes to have a nutritional problem confirmed.

We have also received several insect samples from homes this spring, including millipedes, termites, psychodid flies and varied carpet beetles.

We look forward to receiving your samples. Not only does an accurate diagnosis allow you to manage your plant problems, your samples also allow us to see what’s happening around the state, and provide better updates in the newsletter. Please refer to the sample submission section of our Website http://soilplantlab.missouri.edu/plant/index.htm, or contact us for more information on sample submission.

Simeon Wright
Plant Diagnostic Clinic
WrightSi@missouri.edu