The foliage at the ends of the branches on my honey locust are turning brown. Why?


The foliage at the ends of the branches on my honey locust are turning brown. Why?


The browning of the honey locust foliage is probably due to the mimosa webworm.  Damage occurs when the caterpillars tie honey locust leaflets together and feed on the foliage inside the tightly compressed, protective webs.  Affected foliage gradually turns brown.  There are two generations of caterpillars per year.  Extensive damage is most obvious following the second generation in August. 

Damage from the mimosa webworm is seldom serious to otherwise healthy, well-established trees.  The webs and browned foliage are unsightly.  The damage is more aesthetic than serious. 

Chemical control for mimosa webworm is rarely warranted.  Treatments after the foliage has turned brown are ineffective and a waste of time.  Such late treatments may do more harm than good by destroying the natural enemies of the pest rather than the pest itself.  Sprays must be applied at the start of the caterpillar period and before webbing is apparent to be effective (mid-June and again in early August in Iowa).  Insecticides available to homeowners include Bacillus thuringiensis (Dipel, Thuricide, etc.), Sevin, permethrin, and spinosad.  Carefully read and follow directions on the insecticide label.


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 . The information contained within may not be the most current and accurate depending on when it is accessed.