How do you solve a problem like the whitefly?

THE GARDEN FANATIC

“Shoo fly, don’t bother me!”

-- TRADITIONAL SONG

“Do not use a hatchet to remove a fly from your friend’s

forehead.”

-- CHINESE PROVERB

Last weekend, while shopping for furniture with Catharine, scores

of giant whitefly whizzed by our heads. Their flight formation

resembled a squadron of MIGs -- CC thought they looked more like a

swarm of giant whitefly. Several times larger than the common

whitefly, these unwelcome pests have established themselves in Laguna

and other locales, threatening many species of plants.

Giant whitefly is a winged insect that is found mainly on the

undersides of leaves. When it is disturbed, it will flutter rapidly

around its host plant. All whiteflies belong to a family of insects

called Aleyrodidae, which means flourlike, in reference to the white

coating on their wings. The recent warmer temperatures encouraged the

population of giant whitefly to swell to tremendous numbers sending

gardeners down to their favorite nursery, rather than the beach, in

search of relief.

Hibiscus was originally the host of choice, but the giant whitefly

now attacks a number of plants -- a reported 39 genera at the

beginning of summer. Known Laguna hosts include bird of paradise,

citrus, fuchsia, morning glory, salvia, schefflera and xylosma, among

many others. Adult female whiteflies lay their eggs in a

characteristic circular pattern on the undersides of leaves. The

larvae that hatch from the eggs insert their mouthparts to remove sap

from leaves, weakening plants and causing them to grow poorly.

The giant whitefly eggs, larvae and adults form dense colonies on

the undersides of leaves. Trademark beardlike threads up to four

inches long hang from infested leaves. Because the insects are

actively secreting honeydew, sticky strands of material become a

nuisance, along with the black sooty mold that grows on the

excretions. I have found myself batting and muttering at individual

whiteflies as I bring in the morning paper.

The giant whitefly is resistant to chemical treatment, so those

who believe in elimination through the use of stronger pesticides

will discover that this is not an effective option. The giant

whitefly will simply return, stronger and more pervasive. It is too

widespread and breeds far too quickly for agricultural officials to

be able to eradicate it at this point. The proverbial pesticidal fly

swatter will not eliminate giant whitefly from the landscape.

Many gardeners have discovered that washing off the undersides of

foliage with water can reduce infestations. Although this is my

favored control, it is fair to say that there are limitations. Even

with the most focused attention to forceful spraying, water will only

remove a portion of the whiteflies and provides no residual activity.

I find that infested plants must be washed once or twice (or more) a

week to keep whitefly populations from increasing. The use of

whitefly sticky traps, placed adjacent to host plants, also aid in

slowing the pest down.

If you don’t have time to wash your plants everyday, both

insecticidal soaps and horticultural oils will kill adult whiteflies

and immature larvae through suffocation -- although they are not

particularly effective against eggs and mature larvae. Because these

chemicals have little residual activity, they are not as harmful to

beneficial insects as stronger and more persistent pesticides;

however, they must be applied weekly for control. Thorough coverage

of the undersides of leaves is essential.

We heard Oliver’s insistent mewing as Catharine and I made our way

home. He greeted us with a nod of his head and then raised his paw in

the opposite direction. He had caught his first mouse in years! I

picked up our cat and thought it be nice if he learns to catch

whitefly next. See you next time.

* STEVE KAWARATANI is the owner of Landscapes by Laguna Nursery,

1540 S. Coast Highway in Laguna Beach. He is married to local artist,

Catharine Cooper, and has three cats. He can be reached at (949) 497

2438, or e-mail to [email protected].