In some horticulture circles one hears that native plants have fewer pests than other ornamental plants. This may have been true 50 years ago, but with all of the international trade and commerce, we constantly have new foreign pests, and some have a hunger for our native plants.
A new whitefly — this time it’s a pest from Central America or Mexico— hasn’t reached our county (as far as I know), but it is in Monroe and Dade (in March 2009) counties. It is the rugose spiraling whitefly, also known as the gumbo limbo spiraling whitefly or Aleurodicus rugioperculatus. Gumbo limbo is a native tree, more commonly known as the “tourist tree,” because of its reddish peeling bark.
The rugose spiraling whitefly is a large whitefly, about 2.5 millimeters, and a slow flyer. It deposits eggs in a distinctive spiral pattern which is highlighted by the white waxy substance it also leaves behind. One person called me from Key Biscayne, an outbreak area, and exclaimed that there were so many whiteflies and wax in his landscape that it was almost like snow!
These insects also produce significant amounts of “honeydew,” which is the liquid waste it excretes. This “honeydew” is then colonized by a black fungus and called sooty mold. This sticky “honeydew” can accumulate on objects beneath infested trees — and slow-moving pedestrians.
This insect has a host list that would make the spread at the Golden Corral look sparse. Some of the 38 hosts besides gumbo limbo include: copperleaf, Norfolk Island pine, periwinkle, cocoplum, buttonwood, mango, live oak, coconut, areca, Christmas and sabal palms. Also see this website: tinyurl.com/3qnc2dz
What to do: Fortunately, this whitefly isn’t as damaging as the ficus whitefly. Some good bugs have been found attacking it: a parasitic wasp and lady beetles. So avoid spraying with long-residual pesticides as the good attack bugs may end up as collateral damage. Some “softer” pesticides, which have only a few days residual, are horticultural mineral oils and insecticidal soaps. But be careful with our hot, muggy weather now because those “soft” pesticides could cause some foliage damage.
So wait until things cool a bit and just spray a branch or two to see if there will be foliage damage. If you need some other options refer to this article by Catharine Mannion: bit.ly/q7oxHI
If you suspect an outbreak of this new whitefly, please call or e-mail me.
Another new pest which attacks gumbo limbo and crotons and firebush is the — for lack of a better common name —croton-firebush scale. Master gardener Carol Sweat alerted me to have everyone check crotons for this killer scale (see picture). More details are here: bit.ly/p79QL2
Doug Caldwell, Ph.D., is the commercial landscape horticulture extension agent and landscape entomologist with the University of Florida Collier County Extension Service. E-mail: email@example.com