Mahogany webworms http://entnemdept.ufl.edu/creatures/orn/trees/mahogany_webworm.htm have been busy defoliating West Indies mahogany trees in the Upper Keys this spring. The colorful yellow, black and white striped caterpillars of this moth species also produce extensive webs. The adult moth is dull and brown.
The larvae of Macalla thyrsisalis Walker are active for about 10 days during the period of spring flush and leaf expansion. They feed primarily on immature leaves. These insects are not seen the rest of the year.
Although these pests are messy and do extensive damage, these conditions are temporary and do not have a lasting effect on the health of the host trees. The insects are kept under control naturally by parasitic wasps and and a parasitic fly.
Various insecticides were found to be lethal to mahogany webworms under laboratory conditions, but spraying large trees with insecticides, whether in urban or rural areas, may involve unacceptable health and environmental hazards. Spraying mahogany foliage with a neem product, which is a safer option, was found to be effective in preventing mahogany webworms from consuming foliage when applied just before the appearance of larvae in the spring, or when they were in early instars.