WHITEFLIES
(Photo courtesy of South Carolina
Growing,
Clemson University
Integrated Pest Management Program)
If your plant is becoming weak and the leaves are
yellow and dying, it may be harboring whiteflies. If hordes of what appear to
be flying dandruff dart out when you shake it, you have a problem! Another
indicator of infestation is the sticky honeydew whiteflies excrete on leaves,
encouraging the growth of black fungus. The whitefly adult is approximately
the size of a pinhead, moth-like, dusty and white winged. The nymph is
yellowish, legless, flat and oval. The yellow, cone shaped eggs are laid on
the underside of leaves. Both nymphs and adults suck juices from leaves, buds
and stems. In addition to being generally weakened with yellowed, dying
foliage, affected plants may be undersized and poorly colored. Whitefly
infestations are difficult to control once they have taken hold in your
garden.
Alternative Solutions:
·
Use an insecticidal soap, but in moderation, as it will kill beneficial insects
as well as the aphids.
·
Spray your garden with silica Aerogel/Pyrethrin. This product that will
dissolve the cuticle layer on the insect causing it to dehydrate and die.
·
Use Neem Oil.*
Chemical Solutions:
Suggested insecticides for use against whiteflies
include acephate/fenbutatin-oxide combination (Ortho Systemic Insect Killer), permethrin (Immunox), spiromesifen (Forbid), spinosad (Fertilome Borer,
Bagworm, Leafminer and Tent Caterpillar Spray; Garden's Alive Bulls-Eye;
Conserve SC), and tau-fluvalinate (Mavrik).
Because our gardens border neighbors who liberally
use chemicals, organic gardening is not a practical choice. We have found spiromesifen to be the most effective,
but unfortunately also the most expensive, against whiteflies in our gardens.
If you have a serious problem with whiteflies in your area, it might be worth
the extra expense.
*A Word (or two or three…) about Neem
Oil
Neem oil is a botanical pesticide made from an extract of the plant Azadirachta indica. When the oil is distilled from the plant's seeds, its concentrated mixture
contains high amounts of the active chemical azadirachtin. It doesn't
strongly affect humans, mammals, or beneficial bugs, and it has been proven
as an effective insecticide and miticide. When sprayed on plants, Neem oil repels harmful insects like white flies, gnats,
aphids, mites, and weevils, as well as reportedly strengthening the crops
against rust, scab, mildew, and blight. Edible crops of vegetables do not get
poisoned when neem oil is used. Additionally, Neem oil makes plants taste bitter, so pests won't eat
them, thereby functioning as a "contact" insecticide. Azadirachtin
also interrupts insects' transitions between different stages of
metamorphosis, such as growing from larvae to pupae. It prevents insects from
developing a hardened exoskeleton. When the chemical gets absorbed through
the roots of plants, it functions as a "systemic insecticide." That
means crops don't need to be constantly re-sprayed. Perhaps the greatest lure
for using neem oil is that it doesn't harm
beneficial insects. Butterflies, earthworms, bees, lacewings are all safe in
your garden.
Sounds too good to be true, doesn't it? Well, for
the Southern gardener, it just might be. Neem oil is just that… an oil. Just
like the dormant oil sprays that burn our plants when it gets too hot, Neem
oil will too. So, about the time that the whiteflies and aphids are most
active, Neem oil will have to find it's way back onto your shelf until the
weather once again drops below 75 or 80 degrees. *Sigh*
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