Citrus Leafminer - A Curiosity

We have had several samples of contorted leaves with serpentine squiggly lines brought to our help desk by concerned citrus owners.

Folks want to know what is happening with their citrus leaves and if it will kill their tree.

This damage is caused by the citrus leafminer (the larval stage of a small moth) and it is mostly cosmetic damage. Mature trees can easily tolerate this damage. Young trees may need to have some horticulture oil sprayed on the new growth to keep this damage to a minimum.

For more information see this publication: http://trec.ifas.ufl.edu/mannion/pdfs/CitrusLeafminer.pdf

Cypress Twig Gall Midge

These pretty berry looking appendages on the ends of the twigs are a gall caused by a midge. No cause for alarm -- just think of them as an extra oddity to the plant.

For more information see this publication: http://edis.ifas.ufl.edu/pdffiles/IN/IN80600.pdf

Giant Caterpiller Eats Plumeria

Take a look at your Plumeria to see if this colorful caterpillar is munching away at the leaves. This is the georgeous larva of the plain looking tetrio sphinx moth. One of its favorite host plants is Plumeria. Please consider sparing this caterpillar. Your Plumeria leaves will soon be falling off anyway.

For more information see this publication: http://edis.ifas.ufl.edu/in621

The Case of the Brown-tipped Oak

By Andy Wilson
Extension Specialist

The client was concerned about her oak tree. She had noticed that the last several inches of some of branches were dead, with brown, lifeless leaves. She brought some branch samples to our Lawn and Garden Help Desk, fearing the worst. Was this something that would spread? Would it kill the tree?

Looking at the damage, my first suspicion was twig borers, tiny beetles that bore into branches. These borers introduce a fungus that kills the branch from the point where the beetle has entered the branch to the branch tip. Often this is the last one to 2 feet of the branch. The fungus serves as the food source for the immatures (young). The entrance holes are tiny and my middle-aged eyes, even with the help of reading glasses could not locate a hole. However, a quick look under the microscope revealed the tiny, round hole, almost machine drilled in its appearance.

Twig borers are common on many kinds of trees in our area, including red maple, oaks and some other trees. The damage is usually more cosmetic than threatening to the tree. Eventually the dead branch tips drop to the ground. Insecticidal treatment is usually not necessary.

More information about twig borers can be found here: http://www.entnemdept.ufl.edu/creatures/trees/black_twig_borer.htm

Powdery Mildew of Cucumber

By Andy Wilson
Extension Specialist

Fall is a good time for vegetable gardening in Pinellas County and cucumbers are one of the many vegetables that can be grown now. Cucumbers are not difficult to grow but, as with other vegetable crops, some problems can occur. One of the most common disease problems of cucumbers is powdery mildew. We usually receive many samples of this disease during the fall through spring vegetable gardening seasons at our Lawn and Garden Help Desk.

Powdery mildew is one of the easier to diagnose diseases due to the distinctive white fungal growth it produces. This growth resembles a fine dusting of talcum powder over the leaves. Heavily infected leaves turn brown, shrivel and die.

Where possible, select cucumber varieties that are known to be resistant to powdery mildew. Also, keep the plants adequately fertilized. Cucumber plants that are suffering from nutrient deficiencies tend to be more vulnerable to attack by powdery mildew than healthy plants.

Among the fungicides that can be applied to cucumbers in the home garden to control powdery mildew are copper fungicides and neem oil. Neem oil may harm bees and other beneficial insects. Be sure to read and follow all label directions. For more information on disease control on cucumber see this fact sheet: http://edis.ifas.ufl.edu/PG046

Take-all Root Rot of St. Augustine lawn

In August and September we saw many Take-all Root Rot samples brought in to our Diagnostic Desk by frustrated homeowners. Periods of heavy rainfall and a stressed lawn trigger this disease which appears in summer and early fall.

Yellow and light green patches of St. Augustine lawn that eventually thin and die are the symptoms our walk-in customers described. Roots show the symptoms before the leaves do. By the time the leaves turn yellow, the disease has been destroying the roots for weeks or even months.

This disease is more easily prevented than controlled. Reducing stress on the lawn in the areas of mowing, fertilizing and herbicide applications is important. Proper watering, with a Rain Sensor Shutoff for sprinkler systems, helps in prevention.

There is no chemical control for Take-all Root Rot unless you are treating preventatively.
For more information, please see this University of Florida link: http://edis.ifas.ufl.edu/pdffiles/LH/LH07900.pdf

Hickory Horned Devil

This imposing larva (caterpillar), known as the hickory horned devil, is most often observed when it is full grown and comes down from the trees to wander in search of a site for pupation. It can beome as large as a hot dog.

This large caterpillar will eventually become the regal or royal walnut moth, one of our largest and most spectacular moths. Like most other moths, it is nocturnal but is sometimes observed around lights at night.
The regal moth typically has only a single generation per year. In Florida adults have been collected in May, but are more common during the summer.

The larvae live about 35 days and have been reported from a variety of host tree species. They are commonly found on species of the family (Juglandaceae) including walnut (Juglans nigra), butternut or white walnut (Juglans cinerea), and a variety of hickories (Carya spp.) including pecan. In Florida, larvae are frequently found on sweetgum (Liquidambar styraciflua). Other hosts commonly listed are persimmon (Diospyros virginiana) and sumacs (Rhus spp.).

In central Florida, larvae are usually found from late July to mid-August while they are wandering on the ground searching for a suitable location to burrow into the soil for pupation. The pupa is the overwintering stage.

The regal moth is a beautiful and fascinating member of our native fauna, and its larvae should NOT be killed. If a larva is found crawling on pavement or in an area of thick turf grass where it would have difficulty burrowing, it should be moved to an area of soft soil or a mulched area where it can burrow for pupation.

For more information see this website: http://entomology.ifas.ufl.edu/creatures/bfly/regal_moth.htm