Extension Service: Anthracnose blight visits variegated plant

I visited a large landscape site on July 22. That was before all of the recent major rains. The landscape manager was concerned about defoliating and dying variegated "Goldfinger" scheffleras or, as they are referred to around here, arboricolas. Over 80 to 100 plants were declining and in various throes of die-back. Interestingly, the plain green arboricolas in the same planting beds were not affected.

That is the price one may pay for a fancier-looking plant. It may be flashier looking than the parent species, but susceptible to some insect or disease or less able to handle colder temperatures. In this example, an anthracnose fungus (Colletotrichum sp.) was causing leaf spotting and twig cankers on the variegated dwarf scheffleras.

One could confuse the symptoms of this disease with the common scorching of leaves after a severe pruning to reduce hedge height. However, in that case, the plants will refoliate and not continue to decline.

What to Do: Make certain that the planting bed is well-drained and that the irrigation is hitting the root zone (ground) and not the foliage. Rip out moderately to severely infected plants to minimize anthracnose spore dispersal. Apply fungicides that have propiconazole or thiophanate-methyl and are labeled for use on ornamental plants in the landscape. Applications may need to be repeated on a two-week basis until the disease is not a threat.

Updates: Because individuals read the July 10 column and called the pink hibiscus mealybug hotline, (888) 397-1517, the USDA and the local Division of Plant Industry inspectors released parasitic wasps in this region, which combat the plant-killing mealybugs. Hopefully, they will significantly reduce the numbers of this serious threat pest.

Palm lethal yellowing disease was confirmed from a large screwpine sample, Pandanus sp. on the Isles of Capri. Pictures of this and other lethal yellow disease symptoms are at: collier.ifas.ufl.edu/Horticulture/palmyellowing.htm.

Doug Caldwell is entomologist and commercial horticulture agent for the Collier County University Extension Service. E-mail dlcaldwell@ifas.ufl.edu or call 353-4244; Web site, collier.ifas.ufl.edu. For home gardening information, call the Collier County Extension Service Master Gardener Plant Clinic at 353-2872; open 9 a.m. to noon and 1 p.m. to 4 p.m. Monday, Wednesday and Friday at the extension office, 14700 Immokalee Road.

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