A trio of landscape problems are showing up in our gardens

This Sri Lanka weevil has eaten scalloped patterns into the tropical almond leaf. Doug Caldwell

This Sri Lanka weevil has eaten scalloped patterns into the tropical almond leaf. Doug Caldwell

The rusty millipede is new this year and comes in varying shades of coral-brown. Doug Caldwell

The rusty millipede is new this year and comes in varying shades of coral-brown. Doug Caldwell

These white patches on the Mexican petunia leaves are caused by an arthropod. Doug Caldwell

These white patches on the Mexican petunia leaves are caused by an arthropod. Doug Caldwell

We are seeing many types of plants with chewing damage which starts at the edge of the leaf and meanders toward the midrib. So many plants are chewed, that the destruction reminds me of hail damage on some properties. This is caused by a ¼ inch long weevil, Myllocerus undatus, from Sri Lanka. It became established in Homestead and the Boca Raton areas in 2000 or so. This weevil, creatively nicknamed, the Sri Lanka weevil or Asian grey weevil, is unusual in that it feeds during the daytime. Typically, weevils are nighttime munchers.

If you look closely, you can see the grayish-cast weevil with little black scribbly lines etched on its back and a yellow-ish hued head. As soon as you touch the leaf, they drop to the ground and hide or fly away. Flight is also unusual for the weevil group; many species are flightless.

Thus far, Florida records include 68 hosts from citrus to weeds to palms, some of the commonly notched plants are: areca palm, Australian brush-cherry, black-olive (oxhorn bucida), bottlebrush, buttonwood, cocoplum, copper leaf plant, crape-myrtle, ficus, golden dewdrops, grapefruit, hibiscus, Hong Kong orchid tree, live oak, loquat, lychee, mahogany, mango, plumbago, pygmy date palm, roses, tibouchina, senna, tropical almond (Terminalia catappa), wild tamarind and woman’s tongue (Albizia lebbeck).

Apparently no information is to be found in the reference books on the biology of this weevil. Most likely the larvae or grubs feed on roots in the soil, but no observations have been made to shed much light on that aspect of its life history. This is most likely a good situation, as it indicates that the grubs aren’t causing significant damage…yet! With many weevils it is the grub stage that does the most damage. For instance, grubs of the black vine weevil wreak havoc on roots and main trunks at ground level of taxus and rhododendron shrubs in the Midwest.

The foliar chewing by the adult weevils may be cosmetically unappealing, but should cause little damage to plants. If the shredded-leaf damage surpasses your aesthetic threshold, sprays with products containing pyrethroids such as bifenthrin or cyfluthrin have provided good knockdown of the weevils. Only use products labeled for landscape ornamental use. If you are spraying citrus, again, be sure the label specifies citrus as a target plant.

A more rewarding approach for some individuals is to go around your landscape with a bucket of soapy water. Place the bucket under the attacked foliage, tap the plant branches and watch the little buggers disappear beneath the bubbles.

I have one report of grubs chewing the roots on lychee and longan trees. So if your trees aren’t growing very well you may want to do a little rooting around for grubs. See this fact sheet for pictures and more biology:

http://trec.ifas.ufl.edu/mannion/pdfs/SriLankaWeevil.pdf

We have several new millipedes which have been popping up in mulched beds and inside homes. We have had the yellow-banded millipede (Anadenobolus monilicornis) for a few years and earlier this year the rusty millipede (Trigoniulus corallines) and an isolated report of the giant African millipede. Millipedes are considered beneficial, but people get upset when they crawl up exterior walls and then indoors to spend some quality time with you.

Millipedes are pretty amazing if you ever watched them crawl along — how do they get all of those legs to work in sequence? There are four legs per body segment! And at least 50 segments per millipede. A fact sheet on millipedes is available here:

http://trec.ifas.ufl.edu/mannion/pdfs/Yellow-bandedMillipede.pdf

If they are getting indoors, caulk or fix the cracks and crevices, because if millipedes can get in, you can bet ants and lizards and other critters can, too. If you feel it is necessary, try using Ortho Bug-Geta Plus, it has two pesticides incorporated into a bait which may be attractive to millipedes, but this is still speculative.

Another landscape phenomenon has created a little controversy as it occurs on Mexican petunia (Ruellia species). Plants are developing white woolly patches on their leaves and stems and people are wondering if it was powdery mildew or a chemical residue.

Turns out it is neither. It is a type of growth distortion called an erineum and it is caused by tiny mites called eriophyid mites.

I doubt treatment is ever needed, although there is some leaf distortion. After all, this is a plant which seemingly prospers after an application of Roundup herbicide! But perhaps this information on this plant, often bad-mouthed as invasive, may save some people from wasting their money and time on a misdiagnosed fungicide application.

Some landscapers were wondering: why worry about this aggressive plant that shouldn’t be used. I reminded them that there is the seedless variety, “Purple Showers,” and not to get bent out of shape about seeing it in the landscape. Then they reminded me that it is aggressive just by its flopping vegetative growth habit and runners which cause small plants to grow into large stands of lovely blue flowering shrubbery.

I also got a picture of my one and only viewing of a malachite butterfly hovering around my Mexican petunias, a reported host plant! If you’d like to discuss more, please see my blog:

http://dougsbugs-n-shrubs.blogspot.com/

Doug Caldwell, Ph.D., is the commercial landscape horticulture extension agent and landscape entomologist with the University of Florida Collier County Extension Service. Phone phone, 353-4244 x203. E-mail dougbug@ufl.edu

© 2009 marconews.com. All rights reserved. This material may not be published, broadcast, rewritten or redistributed.

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