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This is a complicated subject, not a happy one. Please take your time and read all the pages. . .twice!
There is no need to say something stupid like, Meet the whitefly. You have already met or you wouldn't be reading this page.
On the following pages you're going to learn about the most common whiteflies in Southern California how they live, and what you can do to make them die!
Index:
Beneficial Insects. These are not sprays! They have little bodies, and eyes and legs & wings etc. Out in nature there is almost always a predator or parasitic insect that feeds on a pest insect. We call the insects that destroy our plants 'bad bugs' and the insects that prey on the bad bugs 'beneficials' or good bugs.
Unfortunately we don't always have the specific beneficial up here in the states. The new Giant Whitfly is a case in point. It has become a major problem for homeowners everywhere. The San Diego Ag Dept. entomologists continues to try to find the best beneficial wasp that will attack the giant whitefly. So far, they have not been very successful. All this takes lots of time and we are all in a hurry to get this problem solved.
We do have some 'Beneficials' that will help with many of your gardening problems. Here they are:
Lace Wings. Lacewings are some of the best 'good bugs' you can release. They will out eat a LadyBug 10 to 1 on aphids and will eat whitefly larvae, scale eggs and most other pests. They won't fly off to your neighbors yard at the drop of a hat like LadyBugs do. Lacewings are pretty little insects with either green or light brown transparent wings that fly around at dusk in your garden. The Lacewing in the adult stage only sips nectar, looks pretty, has sex ( I guess!) and lays eggs. They are not quite an inch long.
The eggs are attached to little thread like stems. These eggs hatch out into tiny little brown larvae that look a little like a minute aligator with lots of legs. These are the ones that do the eating. They can eat lots of aphids, whitefly larvae and eggs, spider mites... almost anything tha moves.
Plant lots of herbs like dill, and cilantro and let them bloom. Sweet allysum and other small flowered bloomers are excellent. Keep your garden well watered and have some small pans of water nestled around to provide drinking water. Change these water pans often so you don't breed mosquitos!
Lacewings will reproduce in your garden and you simply can't put out
too
many. They will certainly help keep your whitefly population down. The
cost at
Weidners' is $2.75 for each strip with about 160 lacewing eggs on each
strip
ready to hatch. To be successful with lace wings you need to put out as
many
strips as you can afford sometime in April or May and then follow up
with a 2nd
and 3rd group every two weeks or so.
WHY? Because all of the whiteflies are on a 21 day cycle or so. You
already
have plenty of those in every stage of the cylcle. Lacewings go through
their
own 4 stage cycle too. The larvae eats for about 10 to 12 days, then
pupates,
becomes and adult who lays eggs and finally the eggs hatch and eat
again. If
you only put out one batch you have no one working for 3/4ths of the
time. With
beneficials its timing, timing, timing. They plant some beneficial
friendly
plants with small easy to sip from flowers. Some of the easiest are
Sweet
Alysum, Bacopa or some parsley or carrots that you allow to bloom.
Encarsia formosa is the specific whitefly parasitic insect that we have available right now. They parasitize the larval stages of regular garden whitefly. Unfortunately they don't seem to like the giant whiteflies very much. Encarsia come as parasitized whitefly eggs. 100 to a little circle for $2.75
I leaned down real close and asked them why they didn't want to help us out on these new pests. "Too hairy" was the reply. This is an insider joke and will not make any sense to any of you folks reading this from other parts of the country where the giant whitefly has not yet landed.
Trichogramma (invisible) wasps for caterpillar control. These are really neat. Each little paper strip has about 4,000 cabbage looper eggs that have already been parasitized by the trichogramma. By the way, I call these 'Tricky-grammas".
A day or two after you hang up your little strip of eggs they will begin to hatch out. A hand magnifying lens makes watching this hatching process possible. Great science lesson for children. The tricky-gramma immediately starts to fly around your garden and hunt out the eggs that night flying moths and butterflies have laid. Instead of a little caterpillar hatching out and destroying your geraniums, petunias, tomatoes or other plants, a tricky-gramma hatches out. Bear in mind this is a preventative only. Your tricky-grammas will pass right over the already hatched worms. For those already hatched and munching, you should spray one of the bacillus thuringensis products. (This is always shortened to BT.) It is not poisonous except to caterpillars. Remember when you are spraying with BT, the caterpillars have to actually eat some of the sprayed plant material in order for it to work.
Tricky-grammas cost $2.74 for a strip and that should be plenty for an average garden. It is best to release monthly during the summer.
Greenhouse whitefly and sweetpotato whitefly are the most common whiteflies found in the garden.
Giant whitefly in Southern California is bigger than all the rest.
DUH!!!
That's why it is called giant whitefly. Hibiscus is the number 1 host
and they
can totally destroy full grown plants. In giant whitefly you can see
the eggs
in an oval group of little white dots. The adults secret a white hairy
thread
that hangs down and with lots of whiteflies looks like a whispy beard.
This is
sticky and makes it hard for the beneficials and other sprays to
penetrate.
All the whiteflies have nice long scientific names and are each a
little
different. If you enjoy a certain masochistic curiosity and want to
learn to
know the scientific details go to the UC Davis site.
www.ipm.ucdavis.edu. We thank
them for
excellent pictures and they have lots of great technical information.
For all
of us ordinary folks it is enough to know that the whitefly called
greenhouse
whitefly came on the scene first. Perhaps they were part of God's
original
curse when he kicked Adam and Eve out of Paradise. As soon as the
whiteflies
appeared it wasn't Paradise any more!
The silverwing or sweetpotato whitefly came to Southern California in the late 80's and this is the whitefly that you heard about in huge masses destroying the lettuce in the Imperial Valley.
All the whitefly feed on the underside of leaves, sucking the juice out of the tissues. Let's take a look at the life cycle of our typical whitefly. We'll call her Wendy Whitefly. (no offence to all the wonderful Wendy's ) Wendy Whitefly starts out her life as an egg that is too small for you to see with the naked eye. A good hand lens will show you a black spot that looks like this....picture of an egg. In 3 to 5 days that egg hatches into larval form. Looks like the egg to our eyes. In the Giant you can see the eggs plainly.
Wendy changes several times during her larval state. These changes are called 'instars' but we don't need to worry about technical terms. The warmer the weather gets, the faster Wendy Whitefly goes through all those growing up stages. Somewhere between 17 to 21 days later Wendy splits open that larval casing and out comes a little crawler that devolps quickly into an adult whitefly.
She immediately starts to feed on plant tissue, very quickly laying large numbers of eggs to start even more nasty little Wendy's.
It is almost impossible to kill the eggs with any kind of pesticide. The other stages can be killed but whitefly very quickly become resistant to many of our spray materials. The adults also have a waxy covering that helps to protect them from spray material. Wendy is so clever, unless you are spraying when the temperature is down into the 60's Wendy and all her friends fly off just as soon as the first drops of spray approach. She hovers around overhead and as soon as you leave she call out, "All clear, all clear, return to base."
Since there are not too many days in Wendy's life cycle when a spray is effective it is necessary to spray about every 5 days on a regular schedule in order to get any kind of control. One of the new better sprays is the Bayer brand of Rose Advance. Bayer wanted into the US market and spent the money to register a very good chemical for the retail home garden. This costs a lot of money!!!! This is the same chemical that we as growers have had for about 5 or so years. It has some long term affect and also comes as a soil drench formula for larger plants. Use the drench carefully....it is hard to decide how much to use.
If you live in San Diego County, Orange County Los Angeles County, Southern Texas, Florida and probably Lousiana stop and read this now. All others stop and thank God for small favors.
San Diego has the dubious honor of being the first home base for a new whitefly know as the giant whitefly. It also has a long latin name but we won't make you learn it.
This whitefly entered from Mexico and it was not carrying a green card when it came in. These whiteflies are many times larger than the regular garden whiteflies that have plagued you in the past. They are easy to recognize. They totally cover the undersides of leaves of infested plants. A long white hair hangs from each whitefly giving the leaf a furry, almost flocked look. The circle of eggs is easily seen by the naked eye. An irregular circle of little white dots.
The favorite host plant is hibiscus. After that they go for zylosma, avocado, citrus, begonias, cannas, bananas, jade plants, and about 40 more species of plants. The list keeps growing. Left alone they will completely cover a hibiscus and eventually kill it. They seem to stay on a plant they like rather than spreading immediately to lots of other plants. The older shadier leaves are favored. Beacuase of the masses of white hairs and sticky excretions it is very difficult for beneficial insects to penetrate to the larvae. Too hairy! The same goes for spray material. This is one bad bug from Hell!
We will give you a list of things you can do to help! All you folks reading this in affected areas, check your hibiscus plants. This new whitefly is now pretty well spread over all of Southern California.
These are the steps that the homeowner can do to minimze the infestation.
Now
what
to do about them? You really have two paths to go down. The first one is beneficial insects and soft organic type sprays which are the more natural approch. The second path is that of chemicals and Nuke'em type of things.
What sprays can be used and how do they work. All of this is in laymans terms and you need to know that I am not a registered pesicide operator. Other people at the nursery are...as for me...I would rather do other things like talk to customers.
Is there a better way. Certainly there are a number of things that can be done to keep the whitefly population down to a reasonable level.
Water: The cheapest and one of the best sprays there is. Clean plants are healthier plants and especially with the new giant whitefly washing away the white waxy hairs is crucial. Use a strong forceful spray and hit the undersides of the leaves.This is where the whiteflies are.
Insecticidal soap: other soap types of sprays. Soap kills by drying out the waxy covering on many insects. Using an insecticidal soap is the safest for your plants. You can mix your own using Palmolive, Ivory liquid, Dr. Bruners, Simple Green.
Oil sprays. Neem oil types of spray. This is from the neem tree in India , It acts as a growth interrupter. This spray will not hurt the beneficial insects in your garden. It is expensive and needs to be used on a regular basis to work.
Good Luck, The whole study of insects and insect control is so complex and really far beyond my knowledge. We do the best we can to help you. Go back to school and become an entomologist and then you can help us. There are any number of new insects and diseases that seem to be attacking in California in recent years.
Many of them are so serious and have such huge potential economic impacts that it behoves us all to be very careful not to sneak any plants into the country on your travels.
Evelyn Weidner
