Entry, distribution and optical manipulation of thrips and other

pests in greenhouses

David Ben-YakirEntomology Dept., ARO, The Volcani Center, Israel

Sub orders

Order Thysanoptera• Small insects (1-3 mm long).• Feather-like wings.• Hide in shelters.• Feed mainly on plans, some on

fungi and few are predators.• Asymmetric mouth parts -

cutting and sucking.

Life cycle of thrips

Incomplete metamorphosis

Eggs are laid in plant tissue

2 larval stages feed on plants and mobile

2 “pupal” stages do not feed usually off the plant

Winged adults feed on plants and mobile (dispersal)

Egg to EggC° Days

16 4020 2625 1830 14

Western flower thripsFrankliniella occidentalis• Origin–North West America• Spread throughout the world

with international shipping of plants and by its ability to develop resistance to insecticides.

• Prefers to feed on flowers and pollen.

• Main vector of TSWV.• Main pest in Spring & Fall

Western flower thripsFrankliniella occidentalis

Onion thripsThrips tabaci• Origin–the Middle East• Spread throughout the world

with international shipping of plants and by its ability to develop resistance to insecticides.

• Prefers to feed on plants of the onion family.

• Main vector of IYSV.• Main pest in Summer

Onion thripsThrips tabaciGray-brown, no red ocelli, only few setae on head and thorax, 7 segments antenna

Thrips feed by puncturing epidermis cells and sucking

their contents

Thrips damages

Tomato spotted wilt virus (TSWV)

Onion thrips damagesin chives

UNDAMAGED DAMAGED

Damages caused by onion thrips to onion• Direct feeding, silvering, weakening the plants.• Transmission of Iris Yellow Spot Virus (IYSV),

weakening the plants.• “White straw” = drying of plants before bulb is

fully developed (smaller bulbs, lower yields, shorter storage).

Chilli thrips Scirtothrips dorsalis

• Origin– South East Asia• Spread the middle east and

Eastern USA by international shipping of plants.

• Prefers to feed on growing tips of many plants.

• Main damage - stop or distort new plant growth.

• Main activity in Summer

Chilli thrips damage

Beating method

Thrips monitoring by scouting and traps

Colored sticky traps

Extract in 70% ethanol

Thrips monitoring on the plants

“Extract” using Berlese funnel

On plant counting (inaccurate)

What is known about thrips flight ?

• Weak fliers.• Take off when wind speed 2-4 km/hr.• No flight above wind speed 9 km/hr.• Initially fly up wind.• Transported passively with faster

winds.

The distribution of thrips trapping by height (June 2005, Alumot)

0 25 50

3.0 m

2.0 m

1.0 m

0.3 m

Trap

Heig

ht

% Thrips Trapped

N=2,196

Daily flight time (June-Sept.)

0

50

7--11 11--15 15--19

Time Periods During the Day

% o

f Dai

ly T

rapp

ing N = 67 days

300-1,800 thrips / day

Daily trapping – relation to wind speed

0

15

30

06:00 07:00 08:00 09:00 10:00

Time in July 19th, 2006

Win

d Sp

eed

(km

/hr) Speed

0

15

30

15:00 16:00 17:00 18:00 19:00

Time in July 19th, 2006

Win

d Sp

eed

(km

/hr)

Speed

Moving (wind vane) trap (1 m high)

Leeward side

BACK

FRONT

Wind direction

Trapping Direction – up or down wind ?

Most were trapped on the leeward side Daily trapping – relation to wind direction

No. BackFrontThripsDate73273325/4/0750504625/5/076337439/6/0778224923/6/079010301/7/0763375921/8/07

69.530.543.3Mean13.913.910.7SD

% Trapped

In most sites highest trapping was on the east sideand lowest trapping on the west side (based on about

800 trapping days).

0

25

50

South East North West

Direction on the Pole Trap

% T

hrip

s Tr

appe

d

Tunnel-ATunnel-BOpen-AOpen-B

Geographical differences in annual trapping = risk of thrips

invasion

0

200

400

Mar-04 Apr-04 Apr-04 May-04 Jun-04 Jul-04 Aug-04 Sep-04 Oct-04

Date in 2004

No.

thrip

s/ p

ole/

day

NorthernSouthern

Picks associated with drying of spring wild flowers and cultivated wheat.

protected crops…* Stable growing conditions* Protection from pests

Whitefly: tomato: TYLCV

Thrips: pepper: TSWV

* Limited ventilation (high temperatures and humidity)

Developing methods to reduce small pests invasion to and establishment while

optimizing ventilation

• Protect only where and when needed. • Optical manipulation of pests.• Physical methods to reduce pests

(heat, suction).

Small pests move by the wind.

A wind-tunnel particle image

airflowM. Kacira, S. Sase & L.

Okushima (2004) JARQ 38: 227 – 233

The air flow around the greenhouse effects the distribution of pests outside.

N% N 13

% W 30 % E

10 28 n=795 19 50

23

Door

% S 27n=4296

The distribution of thrips

trapped around the greenhouse

Air flow through roof vents

N

leeward ventilation

….and inside

Air flow and turbulences in and around sixty-span greenhouse.

internal airflow in the wind direction

internal airflow in the opposite

direction

Predicted x-velocity in and around empty Venlo-type glasshouse under leeward ventilation. S. Reichrath, T.W. Davies (2002) Agronomie 22: 3–19

Vertical walls and turbulences slow down the wind.

When the wind slows down the particles it carries precipitated out of its stream.

Thrips are more abundant where the wind slows down. % N 13

% W 30 % E

10 28 n=795 19 50

23

Door

% S 27n=4296

At what time invasion occurs ?Only in the morning….

0

30

7 to 8 8 to 9 9 to 10 10 to 11 11 to 12 12 to 13Time interval during the day

% w

hit

efl

ies

tra

pp

ed

Vents can be opened when the is no risk of whiteflies’ entry (in the afternoon, at night). Rolling

motors to regulate internal climate

N

CC

SEECCWCW

60-80

40-60

20-40

0-20

N

CC

SEECCWCW

21.3-21.9

20.7-21.3

20.1-20.7

19.5-20.1

SUMMER

WINTER

Seasonal changes of

spatial distribution of

thrips in a chives’ growing

tunnel

Mean temperature

°C

Rate (%) of infested plants

Thrips simplex

Insects have

compound eye

Thrips’ eyes

The light intensity, size, shape and contrast of the visual cues are

affecting the response.

Unfocused mosaics view of reflected sunlight

Adapted from J. R. Meyer, NC State University

Sky; Take off, Fly

Host finding, Land

Plant use red and blue for

photosynthesis(PAR)

Optical manipulation of pestsAttract or deter pests using light

Whiteflyeye Sky; Take off, Fly

Host finding, Land

Patterns of UV reflection as seen

through the insect eye vs the image obtained

by the human eye

Visual cues affecting pests’ invasion to protected crops

Reflection of Sunlight

To land ?

To stay ?

To enter ?

Adapted from B. M. Diaz and A. Fereres (2007) Pest Technology 1: 85-95.

Pests are deterred from landing on highly reflective (>20% sunlight) surfaces

OptiNet™ Screens absorb UV and have high reflection of sunlight protect crops from pests Infestations

0.0

0.1

0.2

0.3

0.4

350 450 550 650 750 850

Frac

tion

of s

un lig

ht

Wave Length

OptiNet 50 mesh

Standard 50 mesh

0

30

60

4 5 6 7

Weeks after Planting on Feb. 27th, 2005

Mea

n no

. thr

ips

per t

rap

(± S

D)

Standard 50 meshOptinet 40 mesh

40 mesh Optinet® significantly reduce thrips invasion of chives compare to standard 50 mesh net

Whiteflies landing

Higher reflection = less landing(N=3). Bars with * or ** sign over them are significantly different

at the P<0.10 or P<0.05, respectively (ANOVA).

0

300

600

25-08 09-09 24-09 09-10 24-10

Mean No. W

hiteflies Captured per W

eek

Checking Date in 2008

50 mesh OptiNet

50 mesh 50% OptiNet

50 mesh Standard

Protection is maintained at 30 mesh.Symptoms of tomato yellow leaf curl virus two

month after planting - 93% under standard screen and 20% under OptiNet®.

standard screen OptiNet®

Blinding by high intensity of reflected sunlight

To land ?

To enter ?

Adapted from B. M. Diaz and A. Fereres (2007) Pest Technology 1: 85-95.

Insect response to optical cuesRepelling or deterring

UV blocking

high reflection

Camouflage by reducing contrast or by high reflection

Colored shading nets impede insect invasion and decrease the incidences of insect born-transmitted viral diseases in vegetable crops. Ben-Yakir et al. 2012 Entomol. Exp. Applic. 144: 249–257.

Partly protected summer

pepper and tomato crops

Sunlight filtering and

diffusion

0

50

100

Yellow Red BlackNo.

Whi

tefli

es /

Fram

e / W

eek A

B B

Yellow is clearly preferred

compare to Black or Red

(40 folds)

Clear sticky traps

On which colored net whiteflies

prefer to land ?

Mea

n no

. whi

tefli

es/ t

rap/

wee

k

% to

mat

o pl

ants

with

TYLC

V

0

20

40

A

BB

August 2009

AB

0

5

10

15

B

B

A September 2009A

0

20

40

Black Red Yellow Pearl

A

B B

June2010AB

0

20

40

Black Red Yellow Pearl

B B

AJuly 2010A

Whiteflies - Tomato - Tomato Yellow Leaf Curl Virus (TYLCV)

Bemisia tabaci

Summer planting

Aphids - Pepper -Cucumber Mosaic Virus

(CMV)M

ean

no.

aph

ids/

trap

/ wee

k

% p

eppe

r pla

nts

with

CM

V

April 2007

0

5

10

15A

BB

May 2006

0

8

16

24

B B

August 2006

0

20

40

Black Red Yellow Pearl

July 2007

AB

0

5

10

Black Red Yellow Pearl

April 2007

Myzus persicae and Aphis gossypii

Insect response to optical cuesYellow Attracts and Arrests outside and inside

Artificial yellow flowers to divert thrips away from crop plants (+ lure; + sugary water with insecticides).

Their effects depends on the properties of the sunlight at the place and time that the pests

are active.

They can only provide partial protection from pests and viral diseases.

(may be combined with other control methods and crop cultivars that are disease tolerant)

Limitations of optically active cladding materials

Currently, optically active additives are not specific. Therefore, optically active cladding

materials cause increased shading.

Adapted from J. R. Meyer, NC State University

For optically manipulating pests, covering materials should contain selective additives that let the PAR

pass and highly reflect the colors that the insects respond to.

LEDs: the future of greenhouse lighting!(Chronica Horticulturae 52: 6-12, March 2012)

LED Project at Purdue University

How insects will respond to this environment ?

Reduce establishment of thrips by daily air blow and / or vacuum suction.

Solarization under plasticneed about 2 hours above 40°C

Possible damage to plants.

Thank you for your attention

AcknowledgmentsFunded by the Chief Scientist of the Agricultural Ministry and the board of vegetable growers