I recently noticed a nearby Catalpa tree that was about 90% defoliated. Actually, when I looked at it, I expected it to be defoliated because what I noticed first was the collection of fecal pellets on the ground. The fecal pellets were signs of caterpillars. And the mother of one caterpillar is particularly fond of southern Catalpa.
This species of sphinx moth lays her eggs on the Catalpa because she knows her children will be well fed; they enjoy feeding on Catalpa. So the fecal pellets on the pavement gave me to believe there would be significant defoliation.
Although this scenario seems to put fear in the hearts of many gardeners, perhaps it is worth noting that southern gardeners have actually planted this tree because it is a good source of caterpillars, which are good fish bait, which means there could be food on the table. This is a perspective on plant injury by insects entirely different from that of overfed gardeners fretting about the injury.
And the good news is that the tree is not likely to have serious adverse effects from the damage. Established trees and shrubs can tolerate far more foliar injury that most people are comfortable with. Visible injury to trees and shrubs sometimes creates more stress for humans than it does for the plants.
And those four paragraphs are simply a prelude to the punch line, which is to suggest we not fret ourselves unnecessarily over Japanese beetles. First it’s almost a full time job to have any impact at reducing the injury they do. Second, the injury can be sustained by healthy trees and shrubs. Your efforts at control may be justifiable for new plantings, young plants not yet established, or plants such as grapes that need all the photosynthesis they can get to produce fruit.
But in most cases the insects will feed, and the plants will recover. The plants may not look good for a while. But if they are reasonably healthy when attacked, they probably won’t die. Don’t sweat the small stuff.
alcooke
PS – watch the next issue of Green Thumb Prints for a list of plants seldom damaged by Japanese Beetles.
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Al Cooke
Extension Agent, Horticulture
Chatham County Center
N.C. Cooperative Extension
PO Box 279, Pittsboro, NC 27312
919.542-8202; Fax 919.542.8246
al_cooke@ncsu.edu
http://www.ces.ncsu.edu/chatham/staff/acooke/home.html