Drought and heat stress taking toll on trees and shrubs

This summer has been unmerciful on trees and shrubs. Many calls have been coming into the extension office from homeowners thinking theirs have died. In most cases they have not, but they are suffering from heat/drought stress and scorch.

Heat and drought stress have taken a toll on many newly planted trees and shrubs. New transplants often go through a period of "transplant shock." Just like the name implies, this is a period of stress on the new plant as it tries to adapt to its new environment. Many times, new trees will drop almost all of their leaves the first year planted. This year it has been even more severe due to the weather. Obviously, this is a concern to homeowners. The good news is that in most instances, the newly planted trees will be fine and leaf out the following spring.

The weather has also affected older, mature trees. I began seeing trees drop leaves in July, especially sycamore and cottonwood. Yews have also taken a beating this summer. Almost all of the yews I have seen have brown tips appearing. Here again, this is due from extreme heat, and homeowners should not be overly concerned.

Scorch is a physiological problem associated with damaged roots, limited soil area or hot, dry winds. Moisture is lost so quickly from the leaves that the roots can't absorb and transfer water quickly enough to replace what is lost. Scorched leaves turn brown or, in some cases, turn black from the edges and between the major veins. If severe, the leaf may drop. Leaves may be affected over the entire tree or may be affected only on one side. This is usually seen earlier in the summer during our first hot spell.

If the heat and lack of rain weren't enough by themselves, they also bring with them the problem of plant- feeding insects and mites. Why is this, you might be wondering? Well, excessive heat accelerates insect and mite development, so it takes less time to complete a life cycle or generation and, therefore, more insects to deal with. Also, plant stress due to lack of soil moisture often increases susceptibility to wood-boring insects and bark beetles. In times of drought stress, plants decrease the production of compounds that deter wood-boring insects and begin to emit volatile chemicals that actually attract these insects. Basically, the plants become more attractive to insects. So it turns into a double whammy.

So what does a homeowner do? Watch your plants carefully, keep them watered and do a preventative treatment for wood-boring insects. There are products on the market that are soil applied and will offer 12 months of protection. For product information, please contact me.

On another note, the registration deadline for the 2011 Extension Master Gardener class is quickly approaching. The class will be offered in Fort Scott beginning Sept. 8 and will run through Oct. 27.

For information on the class, please contact me at the extension office at kharding@ksu.edu or call (620) 244-3826.