Feature Article - for release the week of  April 13, 2008

Dan Culbert - Extension Horticulture Agent

Waxy Bumps

There have been lots of things are buzzing around our community the past few weeks, including a good number of ornamental plant pest issues.  When the same critter comes in on homeowner plants and is mentioned by some of our local nursery growers, it does catch your attention.

We will be busy this week with Tuesday programs on the Africanized Honey bee, and our Wednesday installment on our Spring Gardening ShortCourse (Wildlife is the subject).  Our office continues to offer help to local residents who are now spending more time in our Florida Yards.

What’s that thing?

As new growth begins to appear on landscape plants, a close look at some of the leaves may show some small whitish bumps on the leaves.  A fingernail can flick them off the surface, but it would take a lot of time to remove all of them. 

A local nursery grower has been battling these bumps on Indian Hawthorn shrubs for some time. While I was visiting with her a few weeks back, we also notice that her Gardenias had lots of these curious creatures on the tops of the leaves.  Larger ones remind me of small turtles, and the small ones look like little stars. They were clustered on the veins, not scattered across the leaf surface.

The cause?  Florida Wax scale, a real sap sucker.  If left untreated they may slow down the plant’s growth.  Florida wax scale (Ceroplastes floridensis) is covered with a wet looking, whitish wax which is tinged in pink with some dark spots near the edges.  This protective waxy layer on these critters gets thicker as the insect gets bigger, and makes them larger to control.

Scales like this one are often found with a black sooty mold, and if let untreated, will cause leaves to drop off the plant.  The black flaky sooty mold is a fungus, but it grows on the waste material left behind by scales, whiteflies, aphids, and other sucking plant pests.  Control the insects, and the sooty mold will also disappear.

 

Managing Wax Scale

Since adult scale insects often lack legs they stay and place, and are good targets for attack. A careful look under a magnifying glass at colonies of many sap sucking insects may show that some of these scales haves small holes in them.  This means the good guys are at work. 

There are many different predatory and parasitic insects that lay their small eggs on scales, which hatch and then bore into these pests.  These small wasps or flies emerge as adults to lay more eggs and reduce pest populations.  Scientists tell us that the use of highly toxic pesticides will kill these scale pests, but it also does in the good guys as well.

In some cases, predators of pests have been studied enough so that specific insects can be grown in laboratories and released as a means to manage plant pests.  In one study, a researcher found that released beneficial insects controlled scale pests when pesticides could not.

An alternate control measure is to find products harmful to the scales, but not so hard on the good guys.  With scale insects, an application of an insecticidal soap is often enough to smother and dry out the pest insects, but is not as hard on predators and parasites. 

Another least-toxic approach is to use horticultural oils.  But when weather gets warm, the sun gets bright and new tender leaves appear there is a greater risk of burning the plant when oils are used. 

With some of these pests, the infestation may be so great that we many have to rely on the standard insecticides to jump-start our pest control program.  These should be saved as the last resort, and not relied upon as the normal way of getting rid of scales insects.

 

Serious Pesticides

Pesticide recommendations from the University of Florida are required to be based on sound scientific research.  Our information is subject to constant change as new products are brought on the market and less effective ones are not longer sold.  Any time a pesticide recommendation is needed, please be sure that the information is up to date and suitable for the kind of site that is being treated.

Homeowners needing more serious “scale-icides” than soaps and oils may look in the garden centers for products containing Malathion or acephate (“Orthene”).   In all cases, READ THE LABEL to be sure that it is legal to use it where you intend to, and then also see if the target pest is mentioned on  the label as one that can be managed with this product.

Commercial growers and Licensed Pest Control companies have a few more products available in their “pesticide tool kit”.  They have the training and experience that allows them to use different materials.  They also should have the licenses that allow them to legally buy and use these other products.

I’ve waxed on enough this week, and it’s time to buzz on to other issues and events.  I’ve placed more information on our Okeechobee web page, http://okeechobee.ifas.ufl.edu.  If you need additional information on Florida Wax scale, please email us at okeechobee@ifas.ufl.edu or call us at 863-763-6469.  Local residents can stop by our office at 458 Hwy 98 North in Okeechobee, and visit our Okeechobee County Master Gardeners from 1 to 3 PM on Tuesday afternoons.  Go Gators!    

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Trade  names, where used, are given for the purpose of providing specific information. They do not constitute an endorsement or guarantee of products named, nor does it imply criticism of products not named. The Florida Cooperative Extension Service - Institute of Food and Agricultural Sciences is an equal opportunity/affirmative action employer authorized to provide research, educational information, and other services to individuals and institutions that function without regard to race, color, sex, age, handicap, or national origin.  Florida Cooperative Extension Service / IFAS / University of Florida.  Larry A.  Arrington, Dean. Last update: 04/11/2008.  This page is maintained by Dan Culbert