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Thrips and the damages they cause

These little guys are very hard to spot with the naked eye and are as evasive as they are

small. Most people find the signs of these pests long before the pests themselves are

spotted. The symptoms include; black spots or specks dotting all along the infected plant

(these are actually the thrips droppings), small patches of dead leaf tissue throughout the

leaves (the thrips actually pierce through the leaf skin and suck out the juices inside,

leaving a hollow spot while the skin of the leaf is still intact), curling of the new leaf

growth (the feeding of thrips at the point of new growth causes the new growth to curl

around the point of incesion causing deformed leaf growth).

Thrips are rarely seen because of their small size. The insects feed by puncturing the

surface of the plant parts with their single large mandible and slurping the plant juices

that seep from the wound. Flowers or leaves may develop silvery streaks. Heavily infested

leaves appear brownish or silvery, and growing points may become contorted. Some

species of thrips leave sooty spots of black fecal matter on the leaves. Thrips also vector

plant diseases.

Egg-laying scars and feeding damage on pepper

SSppeecciiaall EEnnffoorrcceemmeenntt DDiivviissiioonn Office of intelligence (OI)

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Western flower thrips (WFT) is the most important vector of a group of viruses called

tospoviruses. Tomato spotted wilt virus (TSWV) and impatiens necrotic spot virus (INSV)

are the most common tospoviruses in greenhouse crops. In Ontario, TSWV is generally

found in vegetable crops and some ornamental crops such as chrysanthemum, while INSV

is more common in ornamental crops. In vegetables, symptoms of this disease vary

according to the host, cultivar and stage of plant development, but it can severely reduce

or even stop plant growth. Other general symptoms include stunting, bronzing and curling

of the leaves, and distortion of affected plant areas. In addition, infected fruit are

misshapen and ripen unevenly, often with a necrotic ring pattern.

Close up of the eggs eggs inside the leaf Typical thrips life cycle. Illustration

. by Jane C. Medley, University of Florida.

Life Cycle

Female thrips lay their eggs in tiny slits cut into the surface of leaves, flowers, and

stems. The eggs can be laid any time of year and hatch within a few days in warm, indoor

conditions. The young, called nymphs, are cream to pale green and only visible with

magnification. They feed for 7–14 days. Full grown nymphs, in most species, drop off the

plant to the soil where they burrow down and pupate. Winged adults emerge to complete

the cycle.

Silver-like air-filled plant cells are typical symptoms of a thrips attack

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Leaf spot symptoms caused by Ovipostion damage on

thrips-transmitted TSWV. tomato fruits from thrips

Feeding on foliage causes young leaves to curl upward and gives older leaves a silvery or

speckled appearance. Feeding within blooms on the ovary of flowers can result in

malformed, stunted or discolored fruit, and oviposition into small fruit can also cause

deformities or halo spotting. Generally, any direct damage is overshadowed by the impact

of TSWV transmission in tomato. Tomato spotted wilt virus (TSWV) is transmitted

exclusively by thrips and especially by western flower thrips and tobacco thrips. The

initial symptom of this disease is usually a spotting of the leaf. This is followed by a

wilting of the plant, and by mid season this can clearly be seen as short distorted plants in

the row. Plants infected early in development do not produce fruit. The fruit from infected

plants later in development is usually unmarketable and can display irregular ripening

symptoms.

Onion thrips (Thrips tabaci) nymphs in new growth, between onion leaves. Photo Credit: Whitney Cranshaw, Colorado State University

Helionothrips errans feeding on orchid leaves. Silver streaking on leaf of Dendrobium orchid from (Thysanoptera errans)

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Thrips and the damages they cause

Cuban laurel thrips (Thysanoptera) eggs and adult eitchia sp. Damaging palm leaves

Thrips store their eggs inside the plant tissue and puppestadier can

survive in the soil.

Deformed petals are the results of thrips infestation.

Thrips (Thysanoptera) on the pistils

Larger infestations can easily kill off young plants or even older stressed plants, by

simply eating away at all of the plants tissue. Leaf curl and mutation can cause fruit and

flower drop. A big concern with thrips is the passing of disease from one plant to another.

Thrips will also "bite" humans leaving pain and irritation similar to that of no-see-ums, or

mosquitoes.

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Damages caused by Thrips

Thrips, Scirtothrips perseaeNakahara (Thysanoptera: Thripidae)

Fruit scarring can be severe resulting in "alligator skin". Avocado thrips has only been found feeding on

avocado.

Citrus Thrips Scirtothrips citri Kelly’s citrus thrips (KCT), Pezothrips kellyanus KCT scurfing (or halo) damage .

. Pezothrips kellyanus, on lemon flower

Citrus thrips has a history of rapidly developing resistance to chemicals that are

used repeatedly and frequently for its control.

Western Flower Thrips (WFT) lays its eggs in plant tissue, using a blade-like ovipositor

to insert eggs into leaves, buds, and petals. After egg hatch, there are two feeding life

stages (called the first and second instar larvae), followed by two immobile non-feeding

stages (the propupa and pupa) that both occur in the soil. Adults emerge from pupae and

are winged. Adults feed, mate, disperse, and females lay eggs. Western flower thrips is a

vector of many plant diseases, the most important of which for greenhouse producers are

two plant viruses in the genus Tospovirus: impatiens necrotic spot virus (INSV) and

tomato spotted wilt virus (TSWV).

Thrips-transmitted tospoviruses are a major group of plant viruses affecting over 1,090

host-plant species worldwide. Twenty Tospovirus species have been identified globally

along with the fourteen thrips species that can serve as vectors. Tospovirus species can

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feed on virus infected host plants and infect healthy plants causing huge economic losses

in the agriculture industry and ornamental plant trade.

WFT lays its eggs in plant tissue, using a blade-like ovipositor to insert eggs

into leaves, buds, and petals to protect them from the elements. Washing may

not remove them. Once females mated, WFT produce offspring biased toward

females, ranging from 58-70% female depending on age of the mother

INSV symptoms on Exacum: complete plant collapse.

Eggplant leaf damage caused by melon thrips, Thrips palmi Karny. Photograph by John Capinera, University of Florida

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The thrips species are ranked from highest to lowest based on the no. of virus

associated publications currently available.

Thrips species Tospovirustransmitted References on Tospovirustransmission.

Frankliniella occidentalis Chrysanthemum stem necrosis virus Nagata and de A´évila 2000, Nagata et al. 2004

Groundnut ringspot virus Wijkamp et al. 1995, Nagata et al. 2004

Impatiens necrotic spot virus De Angelis et al. 1993, Wijkamp et al. 1995, and

Sakurai et al. 2004

Tomato chlorotic spot virus Nagata et al. 2004, Whitfield et al. 2005

Tomato spotted wilt virus Medeiros et al. 2004, Nagata et al. 2004, and

Wijkamp et al. 1995

Thrips tabaci Iris yellow spot virus Corteˆs et al. 1998, Hsu et al. 2010

Tomato spotted wilt virus Wijkamp et al. 1995

Tomato yellow fruit ring virus Golnaraghi et al. 2007

Frankliniella schultzei Chrysanthemum stem necrosis virus Nagata and de A´évila 2000, Nagata et al. 2004

Groundnut ringspot virus Wijkamp et al. 1995, de Bordo´ n et al. 2006, and

Nagata et al. 2004

Groundnut bud necrosis virus Meena et al. 2005

Tomato chlorotic spot virus Wijkamp et al. 1995, Nagata et al. 2004

Tomato spotted wilt virus Wijkamp et al. 1995, Sakimura 1969

Frankliniella fusca Tomato spotted wilt virus Sakimura 1963 Naidu et al. 2001

Impatiens necrotic spot virus

Thrips palmi Calla lily chlorotic spot virus Chen et al. 2005

Groundnut bud necrosis virus Lakshmi et al. 1995, Meena et al. 2005, Reddy et al. 1992

Melon yellow spot virus Kato et al. 2000

Watermelon silver mottle virus Iwaki et al. 1984

Scirtothrips dorsalisa Groundnut bud necrosis virus German et al. 1992, Meena et al. 2005

Peanut chlorotic fan-spot virus Chen et al. 1996, Chu et al. 2001

Peanut yellow spot virus Gopal et al. 2010

Frankliniella intonsa Groundnut ringspot virus Wijkamp et al. 1995

Impatiens necrotic spot virus Sakurai et al. 2004

Tomato chlorotic spot virus Wijkamp et al. 1995

Tomato spotted wilt virus Wijkamp et al. 1995

Frankliniella bispinosa Tomato spotted wilt virus Avila et al. 2006

Thrips setosus Tomato spotted wilt virus Tsuda et al. 1996

Ceratothripoides claratris Capsicum chlorosis virus Premachandra et al. 2005a,b

Frankliniella zucchini Zucchini lethal chlorosis virus Nakahara and Monteiro 1999

Frankliniella gemina Tomato spotted wilt virus de Bordo´ n et al. 1999

Groundnut ringspot virus de Bordo´ n et al. 1999

Frankliniella cephalica Tomato spotted wilt virus Ohnishi et al. 2006

Dictyothrips betae Polygonum ring spot virus Ciuffo et al. 2010

Amin et al. (1981) reported S. dorsalis as a vector for Tomato spotted wilt virus, but later German et al. (1992) clarified that this

previous report of a Tomato spotted wilt virus-like virus in India based on a nonspecific identification was actuallyGroundnut bud

necrosis virus.

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Inspecting plant products with the use of a loupe greatly improves your ability to detect pests.

The eradication of new thrips species would cost the Government millions of dollars.

Introduction may destroy native fauna and agricultural crops forcing the people of Guam

to import more produce.

The first line of defense against invasive species is to keep

them out. Control at ports of entry is essential to prevent

the spread of invasive species.

Source: https://greenmethods.com/thrips/

http://plantpath.ifas.ufl.edu/extension/fact-sheets/pdfs/circ0914.pdf

http://pvo.bio-mirror.cn/genus049.htm#Nomenclature

http://ucanr.edu/sites/veg_crop_sjc/files/75702.pdf

Note: All officers are reminded to exercise additional scrutiny when screening passengers with fresh fruits,

cut flowers, live plants and cargo arriving into Guam. For more information, please contact the CQA

Biosecurity Taskforce at 642-8058/60.

Stay Alert. Stay Safe