Thrips Management in BlueberriesBlueberry Day, UC Kearney Agricultural Center, May 2008

David Haviland, UC Cooperative Extension- Kern County

Thrips

• “fringe wings”• small, narrow• gradual metamorphosis• rasping/sucking

mouthparts• 4 wings- both pairs

narrow straps fringed with hairs

• mostly plant pests, some beneficial

Thysanoptera

Citrus thrips life cycle

• Eggs deposited in leaf tissue

• Eggs become larvae• Larvae feed on new

flush• Prepupae• Adult

– Male smaller than female

– Have wings

Citrus thrips vs. Flower thrips

Seasonal Biology• Navel Orange• Up to 8 generations

per year• First appear in March• May/June (small fruit)

critical in citrus• 3rd generation begins

around June 1• Multiple pesticide

applications in non-bearing citrus

0

5

10

15

20

25

30

35

40

4-May

18-M

ay1-J

un15

-Jun

29-Ju

n13

-Jul

27-Ju

l10

-Aug

24-A

ug7-S

ep21

-Sep

5-Oct

19-O

ct2-N

ov16

-Nov

30-N

ov

Ave

rage

thrip

s pe

r bea

t sam

ple

Site 1

Site 2a

Site 2b

Site 3Average number of citrus thrips per beat sample

0

100

200

300

400

500

15-Mar 15-Apr 15-May 15-Jun 15-Jul 15-Aug 15-Sep 15-Oct 15-Nov 15-Dec

Thrip

s pe

r tw

o w

eeks

Site 1 Site 2

Average number of citrus thrips per yellow sticky cards

0

5

10

15

20

25

30

35

40

4-May

18-M

ay1-J

un15

-Jun

29-Ju

n13

-Jul

27-Ju

l10

-Aug

24-A

ug7-S

ep21

-Sep

5-Oct

19-O

ct2-N

ov16

-Nov

30-N

ov

Ave

rage

thrip

s pe

r bea

t sam

ple

Site 1

Site 2a

Site 2b

Site 3

Notes:• Samples taken in the canopy• Probably miss the entire first, and possibly second generations on the suckers from March through May

• In the upper canopy by mid June• Natural cycling out by late September (no more egg hatch)

• Populations crash by mid October

0

20

40

60

80

1-May 16-May 31-May 15-Jun 30-Jun 15-Jul

Ave

rage

thrip

s pe

r bea

t sam

ple

No Hoop Hoop

a

a

a

a

bb

b

b

ns

Effects of using tunnels on thrips densities in the spring

Damage to blueberries

• Do not appear to directly damage fruit– Down on suckers, not near fruit

• Feed on new flush all summer

– Shoot stunting– Leaf deformation– Shortened internodes– Stem scarring– Varies by variety

Damage to blueberries

Beat samples• 10 shoots per sampling area• Sample most sensitive variety• Select top 6-8 inches of new flush• Choose new shoots with few laterals

– Make sure terminal is alive (try to standardize sampling)• Beat onto a black acrylic card

– Also clipboard, notepad, your hand• Count thrips

– On hot days, count adults quickly, then nymphs– Best if done in the morning– Problematic when fruit is present

• Solution could be to sample suckers

0

4

8

12

16

Jubilee Misty O'Neal Star

Varie ty

Ave

rage

citr

us th

rips

per b

eat

19-Jun

25-Aug

Star, Wonderful, particularly susceptible. Advisable to avoid these varieties. Mechanism of selectivity not known.

Varietal differences

High pressure water

0

5

10

15

20

25

30

35

Precounts 1 HAT 1 2 DAT 1 2 DAT 1 1 HAT 2 1 DAT 2

Aver

age

thrip

s pe

r bea

t

Success

Water

Water/Ecotrol

Untreated

a

b

b

c

a

b

b

c

a a

ab

b

c

ab

b

c

nsns

1

High pressure water

0

5

10

15

20

25

30

35

40

45

5017

-Aug

21-A

ug

24-A

ug

27-A

ug

31-A

ug

4-S

ep

17-A

ug

21-A

ug

24-A

ug27

-Aug

31-A

ug

4-S

ep

17-A

ug

21-A

ug

24-A

ug

27-A

ug

31-A

ug

4-S

ep

AdultAdultAdultAdultAdult AdultNymphNymphNymphNymphNymphNymphTotalTotalTotalTotalTotalTotal

avg.

thrip

s pe

r bea

t sam

ple

SuccessWaterUntreated

Adult Nymph Total

Biological Control

• None naturally occurring• Insectary

– Pred mites– Generalists

• Entomopathogens– Beauveria being

investigated– Pathogen of pupal stage

in soil

105 106 107 108

%

Infection

n=231

0

2

4

6

8

10

12

14

16

18

20

0cm 0.1 - 12.7cm 12.8 - 25.4cm Pupated on Plant

Second Instar Thrips Distance from Plant Base at Death

DamageTreatment Thresholds

So… how serious of an issue is this?

Georgia O’Neal

August 2007• Thrips at/past threshold

on Aug, 1• Not treated for 1 month• Measured thrips weekly• Measured length of new

growthSpring 2007• Evaluated yields and

quality

y = -0.3442x + 22.813R2 = 0.8988

5

10

15

20

25

0 5 10 15 20 25 30 35 40

average thrips per beat sample (August 2006)

shoo

t gro

wth

in A

ugus

t 200

6 (c

m)

R2 = 0.8743

R2 = 0.6876

R2 = 0.5506

0

5

10

15

20

25

0 50 100 150 200 250 300

Cumulative thrips from August Evaluation Dates

cm o

f new

gro

wth

in A

ugus

t Misty

Georgia

Oneil

Correlations between citrus thrips density in August and the amount of new flush growth in August for three blueberry varieties.

Measuring thrips damage

Shoot growth and Thrips vs.

Yield(based on 240 plants=1.5 million berries)

y = 0.2461x + 11.464R2 = 0.7687

10

12

14

16

18

20

8 10 12 14 16 18 20 22 24

shoot growth in August 2006 (cm)

Aver

age

yiel

d pe

r pla

nt

(lb, M

ay-J

une

2007

)

y = -0.0906x + 17.192R2 = 0.7902

10

12

14

16

18

20

0 5 10 15 20 25 30 35 40

average thrips per beat sample (August 2006)

Ave

rage

yie

ld p

er p

lant

(lb

, May

-Jun

e 20

07)

For every 10 thrips average for 1 month, 0.91lb/plant reduction in yield (5.26%)

Control plots-- 3.2 lb/plant

reduction (18.4%)

- ~$16,000/acre in losses

Yield Studies Summary

• Impact– Reduced growth (2 yrs)– Reduced number of berries– Reduced yield per plant

• No impact– Size of berries– Quality of berries– Shift in harvest date

Conventional Insecticide Trial

0

5

10

15

20

25

30

35

40

Pre DAT6 DAT10 DAT14 DAT19 DAT27

Thrip

s pe

r bea

t sam

ple

CarzolSuccess/Delegate3Movento2Assail2NovaluronVeratranDLannate/Diazinon2Untreated

Conventional Insecticide Trial

0

5

10

15

20

25

30

35

40

Pre DAT6 DAT10 DAT14 DAT19 DAT27

Thrip

s pe

r bea

t sam

ple

CarzolSuccess/Delegate3Movento2Assail2NovaluronVeratranDLannate/Diazinon2Untreated

Conventional Insecticide Trial

0

5

10

15

20

25

30

35

40

Pre DAT6 DAT10 DAT14 DAT19 DAT27

Thrip

s pe

r bea

t sam

ple

CarzolSuccess/Delegate3Movento2Assail2NovaluronVeratranDLannate/Diazinon2Untreated

Conventional Insecticide Trial

0

5

10

15

20

25

30

35

40

Pre DAT6 DAT10 DAT14 DAT19 DAT27

Thrip

s pe

r bea

t sam

ple Carzol

Success/Delegate3Movento2Assail2NovaluronVeratranDLannate/Diazinon2Untreated

Conventional Insecticide Trial

0

5

10

15

20

25

30

35

40

Pre DAT6 DAT10 DAT14 DAT19 DAT27

Thrip

s pe

r bea

t sam

ple Carzol

Success/Delegate3Movento2Assail2NovaluronVeratranDLannate/Diazinon2Untreated

New Shoot Growth (Star)

y = -0.1586x + 5.9812R2 = 0.5129

0

1

2

3

4

5

6

7

0 5 10 15 20 25 30 35

Average thrips per beat sam ple

Shoo

t gro

wth

(cm

)

Carzol, Movento

Untreated, Diazinon, Lannate

Treatment Program Summary

• Don’t worry until harvest is over• Monitor, treat at about 20 thrips per beat

sample• Success/Delegate• Follow up with Movento (June? Reg,) ~2-3

wks later• Alternate with Assail, Veratran D (NR?)• In the clear by late September

Other Insect Pests

White GrubsPacific Flatheaded Borer

White Grubs (Chafers)• May beetle, scarab,

chafer, white grub, June bug, etc.

• C-shaped grub• Brown adult (attracted

to lights in the summer)

• One generation per year

• Highly polyphagus

Grub biology• Adults present during the

summer (June? to July?)• Lay eggs on soil surface

– Attracted to organic matter• Grub emerges, feeds through

the fall– Numerous host plants– Usually feed on feeder roots

• Overwinters as large grub• Pupates in the spring• Emerges as an adult

Management• Biological Control

– Nematodes• Heterorhabditis bacteriophora• Steinernema carpocapsae• Timing?, Heat/moisture sensitivity issues

• Insecticides– Imidacloprid (Admire)– Diazinon– Timing likely best in ~August when grubs are

small

Pacific Flatheaded Borer

• Adults emerge April-July

• Lay eggs on bark– Usually weak or

sunburned areas• Feed within wood• One generation per

year

Pacific Flatheaded BorerManagement

• Insecticides ineffective in most crops

• Pruning• Destroy prunings• Sunburn prevention

– White wash or paint– Avoid summer pruning