OCTOBER
2009

 

 

 

By
B. Rosie Lerner
 
Purdue
Extension
Consumer Horticulturist

 

 

 

 

 

10-01-09

Question and Answer

Q. I moved to the country 15 years ago, and started planting oak trees then. I have a problem with my white oaks, but not the reds. The leaves are severely curled up and wilted; new growth comes on and looks good for a short while, then it curls also. The tips are especially affected. The trees are growing, but slowly and look awful. Any idea what to do?

A. This sounds like a case of "oak tatters," a disorder of White and bur oak trees that is not entirely understood. This is still a relatively new disorder that was first reported in the 1980s. The assumption is often made that insects are devouring the leaves because of their shredded, lacy appearance, but upon a closer look, there is no evidence of current insect activity. It is thought that the damage actually occurred while the leaves were still in their buds or just after bud break. According to the USDA Forest Service, one or more of the following factors may be involved:

*Low temperature injury to buds or newly expanding leaves

*Insects feeding or laying eggs in the buds or developing leaves. (Specific insect species not yet identified!)

*Herbicides drift from lawn or field treatments.

So, it is difficult to recommend preventative or post-treatment since we're not yet sure what the actual cause or causes might be. Mulching to conserve soil moisture, watering during extended droughts and fertilizing young trees will help trees recover from the injury.

For more information on oak tatters, see http://www.ppdl.org/dd/id/oak_tatters-oak.html.

Q. I have two plants of the endless summer hydrangea. One is 5 years old and the other is 4 years old. When I planted them, one was 2 years old and the other was 1 year old. One of them is not thriving. The older plant is 3 foot tall and 3 foot wide and full of flowers. The younger one is 1/2 foot tall and had only 4 flowers all season long. What am I doing wrong? They are planted in same soil and have the same amount of sun/shade. I am hoping you can help me out. I know it will be the easiest to dig it up and buy a new one. But, I want to transplant it to other location. Is that feasible?

A. It is difficult to know why the one plant is performing so differently; perhaps the younger plant's root system was not as vigorous as the older plant? The two plants may come from different stock plants originally and so might vary in their degree of vigor. Or one container had more fertilizer in the container media than the other. Or perhaps the two sites are not as identical as they might appear? Perhaps there are tree/shrub roots or other plants that are in greater competition with the one plant. There are so many factors, including sun exposure, soil drainage, water distribution, fertilizer availability and soil pH that can vary considerably, even within the same planting bed. Hydrangea are rather demanding of adequate moisture and nutrients. If rains are lacking, watering thoroughly but gently once per week is recommended. A low-nitrogen/high phosphorus fertilizer is ideal for hydrangeas. It certainly wouldn't hurt to try moving the younger plant to a different location to see if it can make better progress elsewhere.

Q. I enjoy reading your column in Kosciusko REMC Electric Consumer and just really need some advice. We have a beautiful tulip tree in our front lawn that drips sap all spring and summer. The tree gets yellow flowers in the spring and starts dripping! It is sticky and is black on the windows, railing and anything under it. We can feel it drip on us when sitting under it. I have planted myrtle and a variety of annuals and perennials but everything dies off -- except mint, which attracts bees. All the plants have that black sticky coating and just look awful. Is there any hope for me? What will grow under this tree? Should it be taken down?

A. You are in good company -- just about everyone who has tuliptrees can relate to your troubles. The sticky drip is actually insect poop and the black is a sooty mold that grows on the poop. Yuck! The tuliptree aphid adult and young nymphs feed on the sap of the foliage, primarily from the undersides of leaves. The aphids excrete a sticky honeydew, which is prime real estate for sooty mold to move in. Similarly, tuliptrees are also frequently home to scale insects that form colonies on the twigs of the tuliptree, and, again, excrete the sticky honeydew.

A strong spray of water from the garden hose and/or application of insecticidal soap may help reduce the aphid population. However, this is not likely to provide much relief from scale insects, but may help reduce the honeydew and sooty mold. Insecticides may be helpful, but only if applied when the scale insects are in their crawler stage of activity. Information on identification and control of scale insects can be found in Purdue Entomology publication E-29 http://extension.entm.purdue.edu/publications/E-29.pdf.

Also, keep in mind that some beneficial insects (ladybird beetles, lacewings and tiny parasitic wasps) will feed on aphids, and insecticide applications may kill these beneficials.

 

 

Writer: B. Rosie Lerner
Editor: Olivia Maddox,