THRIPS
Cuban laurel thrips - eggs
and adult
(Photo courtesy of Missouri
Botanical Garden PlantFinder)
Because they are tiny, thrip infestation is
typically recognized by the dark fecal matter and desiccated plant tissue
they leave behind after feeding. Thrips then burrow deeply into petal and
leaf tissue, inserting their eggs into leaves and stems.
As the nymphs and adults suck plant juices, they
scrape and puncture petals, causing considerable discoloration and
disfiguration. Leaves become bleached and then wither; flowers become
scarred. Heavy infestations result in striated leaves and destroyed blossoms.
Irises are among the flowering plants favored by thrips and therefore they
are highly susceptible to damage. Iris thrips produce stunted growth and
sooty leaves. The tops of infested plants eventually die out. Severe
infestations can kill nearly all of the roots and otherwise leave the plants
vulnerable to fungal infection.
Alternative Solutions:
·
Introduce beneficial insects into your garden. Green
lacewings (sometimes called the "aphid lion") are the best
organic defense again aphids. After a few days, the eggs hatch and tiny
larvae emerge with a voracious appetite. There is no better predator known to
consume vast quantities of eggs and the soft bodies of aphids, mealy-bugs,
spider mites, leafhopper nymphs, caterpillar eggs, scales, thrips, and
whiteflies. The ladybug and the praying mantis also have a taste for aphids
and can prove quite effective in an organically managed garden.
·
Use an insecticidal soap, but in moderation, as it will kill beneficial
insects as well as the aphids. Spray the base of each infested plant every 3
days for at least 2 weeks (or longer if the infestation has not disappeared),
making sure you get both upper and lower leaf surfaces. Prune away affected
flowers and dispose of them; do not compost them.
·
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 thrips
include acephate/fenbutatin-oxide combination (Ortho Systemic Insect Killer), spinosad (Fertilome
Borer, Bagworm, Leafminer and Tent Caterpillar Spray; Garden's Alive
Bulls-Eye; Conserve SC), abamectin (Avid), biphenthrin (Talstar), permethrin
(Immunox), and acephate (Orthene).
Because our gardens border neighbors who liberally
use chemicals, organic gardening is not a practical choice. We have found
spinosad to be the most effective against thrips in our gardens.
*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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