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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
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
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
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
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