08/27/07 - Variable oakleaf caterpillar defoliation in Florida

Received from:
Albert "Bud" Mayfield, Ph.D., Forest Entomologist
Florida DACS Division of Forestry
1911 SW 34th Street, Gainesville, FL 32608
Phone: (352) 372-3505 x.119
Fax: (352) 955-3295
E-mail: mayfiea@doacs.state.fl.us
and
John L. Foltz, Forest Entomologist, Retired
University of Florida
Department of Entomology & Nematology
PO Box 110620
Gainesville FL 32611-0620

It would seem that an outbreak of the variable oakleaf caterpillar (Lochmaeus manteo, formerly Heterocampa manteo) is occurring in north central Florida this summer. I have been receiving calls, emails, pictures, and/or specimens from Dixie, Levy, Suwannee, Alachua, and Marion Counties. The defoliation on laurel oaks is quite impressive in some areas, with trees being stripped of nearly all foliage. Adjacent live oaks are apparently remaining un-attacked.


Oak defloliated by variable oakleaf caterpillar feeding.
Photograph by: Holly Houghton, Dixie County Cooperative Extension Service


Oaks defloliated by variable oakleaf caterpillar feeding.
Photograph by: Holly Houghton, Dixie County Cooperative Extension Service

I just wanted you to be aware of this in case you start receiving inquires. A good source of information on this insect is the following link: http://www.na.fs.fed.us/spfo/pubs/fidls/variableOLC/voc.htm

Any caterpillars present at this time likely represent the second of two generations of the insect. Upon completion of their development, these larvae will enter the soil and overwinter as pre-pupae, with no life stages to be seen again this year. Attempting to control caterpillar populations at this relatively late stage is largely unnecessary and probably futile. In general, most oaks should be able to handle this defoliation and the outbreak will likely subside on its own through control by natural enemies. Homeowners with relatively small, landscape oaks that were heavily defoliated this year may want to monitor the foliage next year in April and May for the presence of egg masses and young caterpillars, and if necessary, apply an insecticide at that time when the caterpillars are small and before the second generation develops.


Variable oakleaf caterpillars feeding on oak leaves.
Photograph by: Holly Houghton, Dixie County Cooperative Extension Service

I am keeping a list of counties from which I have received calls about heavy defoliation (for academic/reporting purposes), so if any of you see this in a county not listed above, please let me know. - Bud Mayfield

Additonal comment from John Foltz:

Some years there are substantial larval populations in October. From the information I have available, I can't infer much about the number and timing of generations in Florida. It seems that caterpillars are most numerous in August. They are occasionally abundant in October-early November. I don't recall any pest reports in the spring and early summer. It may be that the variable oakleaf caterpillar has 2 generations a year in Florida with flight 1 during June-July and flight 2 during September-October. Or maybe this late flight is a flight 3? Some day we should try to assemble flight and larval data to see what this critter does in Florida relative to areas farther north.


The UF/IFAS Pest Alert WWW site is at: http://entomology.ifas.ufl.edu/pestalert/